Cell signalling occurs through the interaction of signalling molecules and receptors. Signalling molecules are secreted or expressed on cell surfaces and bind to receptors on other cells. This initiates intracellular reactions that regulate cell behavior. Signalling can occur through direct cell contact or through secreted molecules acting over short (paracrine) or long (endocrine) distances. Examples of signalling molecules include nitric oxide (NO) and steroid hormones. NO regulates blood vessel dilation by diffusing into cells and activating guanylate cyclase, while steroid hormones enter cells and regulate gene expression by binding nuclear receptors.
Cell signaling is a complex system of communication that coordinates basic cellular activities and cell actions. It involves signaling molecules that produce responses in target cells through receptor binding. There are three main types of signaling: endocrine, paracrine, and autocrine. Upon receptor activation, various intracellular signal transduction pathways are initiated using second messengers like cAMP, IP3, Ca2+, which activate downstream effector mechanisms to elicit cellular responses. The key pathways include G protein-coupled receptor pathways, tyrosine kinase receptor pathways like Ras/Raf pathway and Jak/Stat pathway. Understanding cell signaling is crucial for treating diseases and engineering tissues.
Cellular communication occurs through chemical signaling via ligands and receptors. There are several forms of cellular signaling including autocrine, paracrine, endocrine, synaptic, and cell-cell contact signaling. Ligands can be small hydrophobic molecules that pass through the cell membrane or bind to extracellular domains of cell surface receptors. Receptors can be intracellular or cell surface receptors. Common types of receptors include G-protein coupled receptors, receptor tyrosine kinases, and ion channel receptors. Binding of ligands to receptors triggers downstream signaling pathways involving second messengers like cAMP, cGMP, calcium ions, and inositol phosphates to produce a cellular response.
Cell signaling involves three main stages - reception, transduction, and response. Reception involves signaling molecules binding to membrane receptors, which leads to conformational changes. Transduction refers to the activation of intracellular signaling pathways through second messengers. Response occurs when downstream effectors are activated, bringing about cellular responses like metabolism, gene expression, and cell differentiation. Precise regulation of cell signaling pathways is essential for normal cell function, and defects can lead to diseases.
Cell signaling involves the transmission and reception of information between cells through signal molecules. Signal molecules can act through direct cell contact, over long distances via neurons, locally through paracrine signaling, or systemically through endocrine signaling. Signal molecules bind to membrane receptors on target cells and initiate intracellular responses through ion channels, enzymes, or G-proteins. This allows for complex and specific cell communication critical to multicellular organism function.
Receptor molecules have three domains: an extracellular ligand-binding domain, a transmembrane domain, and a cytoplasmic domain. G-protein coupled receptors have seven transmembrane alpha helices and activate intracellular signaling pathways by coupling to heterotrimeric G proteins. When a ligand binds to the receptor, it causes a G protein's alpha subunit to exchange GDP for GTP and dissociate from the beta-gamma subunits to activate downstream effector molecules like adenylyl cyclase or phospholipase C. These effectors generate second messengers such as cAMP or IP3/DAG to amplify the signal and regulate cellular processes.
This document provides an overview of signal transduction. It begins with defining signal transduction as the process by which extracellular signaling molecules activate cell surface or intracellular receptors, triggering a biochemical chain reaction that results in a cellular response. The document then discusses the history of studying signal transduction, examples of environmental stimuli, types of receptors, second messengers, cellular responses, and major signaling pathways involved in signal transduction like the MAPK/ERK, cAMP-dependent, and IP3/DAG pathways.
I have tried to make a precise presentation on protein transport, targeting and sorting into organelle's other than nucleus. Hope this might help you. Comments are welcome.
This document summarizes cell signaling and signal transduction. It discusses extracellular signaling molecules that transmit information to target cells via paracrine, autocrine, endocrine, or direct contact signaling. Signal transduction involves reception of signals by cell surface or intracellular receptors, transduction through a signal cascade, and cellular response. Secondary messengers like cAMP, cGMP, IP3, DAG, and calcium ions amplify and carry intracellular signals.
Cell signaling is a complex system of communication that coordinates basic cellular activities and cell actions. It involves signaling molecules that produce responses in target cells through receptor binding. There are three main types of signaling: endocrine, paracrine, and autocrine. Upon receptor activation, various intracellular signal transduction pathways are initiated using second messengers like cAMP, IP3, Ca2+, which activate downstream effector mechanisms to elicit cellular responses. The key pathways include G protein-coupled receptor pathways, tyrosine kinase receptor pathways like Ras/Raf pathway and Jak/Stat pathway. Understanding cell signaling is crucial for treating diseases and engineering tissues.
Cellular communication occurs through chemical signaling via ligands and receptors. There are several forms of cellular signaling including autocrine, paracrine, endocrine, synaptic, and cell-cell contact signaling. Ligands can be small hydrophobic molecules that pass through the cell membrane or bind to extracellular domains of cell surface receptors. Receptors can be intracellular or cell surface receptors. Common types of receptors include G-protein coupled receptors, receptor tyrosine kinases, and ion channel receptors. Binding of ligands to receptors triggers downstream signaling pathways involving second messengers like cAMP, cGMP, calcium ions, and inositol phosphates to produce a cellular response.
Cell signaling involves three main stages - reception, transduction, and response. Reception involves signaling molecules binding to membrane receptors, which leads to conformational changes. Transduction refers to the activation of intracellular signaling pathways through second messengers. Response occurs when downstream effectors are activated, bringing about cellular responses like metabolism, gene expression, and cell differentiation. Precise regulation of cell signaling pathways is essential for normal cell function, and defects can lead to diseases.
Cell signaling involves the transmission and reception of information between cells through signal molecules. Signal molecules can act through direct cell contact, over long distances via neurons, locally through paracrine signaling, or systemically through endocrine signaling. Signal molecules bind to membrane receptors on target cells and initiate intracellular responses through ion channels, enzymes, or G-proteins. This allows for complex and specific cell communication critical to multicellular organism function.
Receptor molecules have three domains: an extracellular ligand-binding domain, a transmembrane domain, and a cytoplasmic domain. G-protein coupled receptors have seven transmembrane alpha helices and activate intracellular signaling pathways by coupling to heterotrimeric G proteins. When a ligand binds to the receptor, it causes a G protein's alpha subunit to exchange GDP for GTP and dissociate from the beta-gamma subunits to activate downstream effector molecules like adenylyl cyclase or phospholipase C. These effectors generate second messengers such as cAMP or IP3/DAG to amplify the signal and regulate cellular processes.
This document provides an overview of signal transduction. It begins with defining signal transduction as the process by which extracellular signaling molecules activate cell surface or intracellular receptors, triggering a biochemical chain reaction that results in a cellular response. The document then discusses the history of studying signal transduction, examples of environmental stimuli, types of receptors, second messengers, cellular responses, and major signaling pathways involved in signal transduction like the MAPK/ERK, cAMP-dependent, and IP3/DAG pathways.
I have tried to make a precise presentation on protein transport, targeting and sorting into organelle's other than nucleus. Hope this might help you. Comments are welcome.
This document summarizes cell signaling and signal transduction. It discusses extracellular signaling molecules that transmit information to target cells via paracrine, autocrine, endocrine, or direct contact signaling. Signal transduction involves reception of signals by cell surface or intracellular receptors, transduction through a signal cascade, and cellular response. Secondary messengers like cAMP, cGMP, IP3, DAG, and calcium ions amplify and carry intracellular signals.
Cell signaling allows cells to communicate and coordinate their actions through chemical signals. There are different types of cell signaling including autocrine, paracrine, endocrine, and juxtacrine signaling. The process of cell signaling involves signal synthesis, transport, receptor binding, signal transmission, interpretation, and termination. Understanding cell signaling is important for treating diseases and engineering tissues, as errors in signaling can cause cancer, autoimmunity, and diabetes. The cell cycle is tightly regulated and consists of growth, DNA replication, and division phases. Key regulators of the cell cycle include cyclins, cyclin-dependent kinases, and cyclin-dependent kinase inhibitors that promote or inhibit cell cycle progression at checkpoints.
The immune system consists of primary and secondary lymphoid organs that work together. Primary lymphoid organs include the thymus, bone marrow, and bursa of fabricus, where immune cells mature and develop. Secondary lymphoid organs, such as lymph nodes and the spleen, expose mature immune cells to antigens in circulation and further activate the immune response. The thymus educates T cells, while the bone marrow produces B cells and other immune cells through hematopoiesis. Lymph nodes and the spleen then filter antigens from lymph and blood to activate mature B and T cells.
The Cell signalling is part of any communication process that governs basic activities of cells and coordinates all cell actions.
The ability of cells to perceive and correctly respond to their microenvironment is the basis of development,tissue repair, immunity, tissue homeostasis.
The cell membrane receptors and internal receptors have been discussed along with current trends in cell signalling.
1. Visualization of cell signalling
2. Stem cells and cell signalling
ntroduction
2. Definition
3. Steps Of Signal Transduction
A) Reception
B) Transduction
C) Induction
4. Important component used in Signal Transduction
A) Calcium ion as second messenger
B) Protein Kinase
Types of Signal Transduction
A) Extra cellular Signal Transduction
B) Intra cellular Signal Transduction
C) Inter cellular Signal Transduction
6. Mechanism of Signal Transduction
A) GPCR pathway
B) RTK pathway
7. Example of Signal Transduction
A) In plants
B) In animals
8. Conclusion
9. Reference…
Biswajit Sahoo presented on signal transduction. Signal transduction is the process by which signals from outside the cell are converted into a form that the cell can use, through a series of molecular interactions along a signal pathway. There are three main stages: reception of the signal by a receptor on or inside the cell membrane, transduction or conversion of the signal within the cell, and response by the cell. Two important signal pathways discussed are the Ras/Raf/MAP kinase pathway involved in cell growth and differentiation, and the Jak/Stat pathway activated by cytokines to control inflammatory responses. Understanding signal transduction can help develop crop varieties with improved resistance to pathogens or tolerance to stresses.
Assignment on Need of cell signaling, Steps in cell signaling, Intercellular signaling pathways, Types of intercellular signaling pathways, Intracellular signaling pathways, Receptors, Intercellular and intracellular signaling pathways. Classification of receptor family and molecular structure ligand gated ion channels; Gprotein coupled receptors, tyrosine kinase receptors and nuclear receptors.
GENERAL IDEA OF SIGNAL TRANSDUCTION
DEFINATION
WHAT DOES THE TERM SIGNAL TRANSDUCTION MEANS
HISTORY
BASIC ELEMENTS IN SIGNAL TRANSDUCTION
TYPES OF SIGNAL TRANSDUCTION
SIGNALLING MOLECULE
RECEPTOR MOLECULE
MODES OF CELL CELL SIGNALING
SECOND MESSENGER
SIGNAL TRANSDUCTION PATHWAY
SOME SIGNALING PATHWAYS
SIGNIFICANCE
CONCLUSION
REFERENCE
Cell signaling occurs through four main categories: paracrine, autocrine, endocrine, and direct contact. Paracrine signaling involves short-range signals between nearby cells, such as synaptic signaling between neurons. Autocrine signaling allows cells to signal to themselves. Endocrine signaling uses the circulatory system to transmit long-range hormones from endocrine glands. Direct contact signaling transfers small molecules through gap junctions between cells. Intracellular signaling pathways transmit extracellular signals through phosphorylation cascades like the MAPK, JNK, p38, and PI3K pathways, ultimately influencing cell behavior.
The document discusses receptor tyrosine kinases (RTKs), a class of cell surface receptors that possess intrinsic tyrosine kinase activity. RTKs are activated through ligand binding and dimerization, which leads to autophosphorylation and downstream signaling. This signaling involves phosphorylation of proteins by RTKs and recruitment of adapter proteins, and results in cellular responses like cell division, differentiation, and motility. Common to all RTKs are an extracellular ligand-binding domain, a transmembrane domain, an intracellular tyrosine kinase domain, and regulatory domains.
Introduction
Protein modifications
Folding
Chaperon mediated
Enzymatic
Cleavage
Addition of functional groups
Chemical groups
Hydrophobic groups
Proteolysis
Conclusion
Reference
The JAK-STAT pathway is a key cell signaling pathway that communicates information from extracellular signaling molecules called cytokines into the cell nucleus. It involves three main components: Janus kinases (JAKs) that associate with cytokine receptors and become activated by phosphorylation upon cytokine binding, signal transducers and activators of transcription (STATs) that are phosphorylated by JAKs and then form dimers that translocate to the nucleus to regulate gene expression, and cytokine receptors that dimerize upon cytokine binding to bring associated JAKs together for cross-phosphorylation and activation of the pathway. The JAK-STAT pathway regulates many important cellular processes like proliferation, differentiation, and immune responses by transmitting signals from cytokines and stimulating
Protein Import & Mitochondrial AssemblyAnkit Alankar
This document discusses protein import into mitochondria. It describes how most mitochondrial proteins are synthesized in the cytosol and contain targeting sequences that direct their import through translocases in the outer and inner mitochondrial membranes. The Tom complex handles transport across the outer membrane, while the Tim23 complex mediates import through the inner membrane. Molecular chaperones maintain imported proteins in an unfolded state as they pass through the translocases with the help of membrane potentials.
Protein targeting or protein sorting is the mechanism by which a cell transports to the appropriate positions in the cell or outside of it. Both in prokaryotes and eukaryotes, newly synthesized proteins must be delivered to a specific sub-cellular location or exported from the cell for correct activity. This phenomenon is called protein targeting. Protein targeting is necessary for proteins that are destined to work outside the cytoplasm.This delivery process is carried out based on information contained in the protein itself. Correct sorting is crucial for the cell; errors can lead to diseases. In 1970, Günter Blobel conducted experiments on the translocation of proteins across membranes. He was awarded the 1999 Nobel Prize for his findings. He discovered that many proteins have a signal sequence, that is, a short amino acid sequence at one end that functions like a postal code for the target organelle.
The document discusses various pathways of protein trafficking in cells. It describes how proteins are targeted to different organelles like the endoplasmic reticulum, Golgi apparatus, mitochondria, chloroplasts, peroxisomes, and lysosomes. Proteins can be targeted co-translationally as they are synthesized or post-translationally after completion. The ER and Golgi play important roles in modifying proteins through folding, glycosylation and sorting before they are packaged into vesicles and transported to their final destinations. Defects in these trafficking pathways can lead to human diseases.
The document discusses signal transduction, which is the process by which extracellular signals are converted into intracellular responses. There are six main steps: 1) synthesis and release of signaling molecules, 2) transport to target cell, 3) detection by receptor, 4) change in cell function triggered by receptor-signal complex, 5) removal of signal, and 6) termination of response. Signal transduction involves cell surface receptors and intracellular receptors that bind ligands and mediate specific cellular responses. Major types of signaling include endocrine, paracrine, and autocrine signaling.
Cells need to communicate both within multicellular organisms and between unicellular organisms. Communication allows cells to respond to their environment and coordinate behaviors. Cell communication involves three main steps: reception of a signal molecule by a receptor, transduction of the signal through intracellular pathways, and response through activities in the cytoplasm or nucleus. Pathways amplify signals and allow for specific responses in different cell types through varied protein expression. Termination mechanisms inactivate signaling to end the cellular response.
Cell Signaling is a phenomenon in which cells receive and respond to the signals or chemical messages from their internal environment or from the neighbouring cells.
Cell signaling involves chemical communication between cells through signaling molecules that bind to receptors on other cells. When a signaling molecule binds its receptor, it triggers a change within the cell through a process called signal transduction. This allows cells to respond to their environment and coordinate their actions. There are several types of cell signaling including paracrine signaling between nearby cells, endocrine signaling through hormones carried in the bloodstream, and autocrine signaling where cells produce factors to stimulate themselves. Cell surface receptors that span the membrane play an important role in signal transduction.
Cell signaling involves communication between cells through extracellular signaling molecules that bind to receptor proteins on the cell surface or inside the cell. These receptors activate intracellular signaling pathways that lead to changes in target proteins and cell behavior. The major types of cellular signaling pathways are those using membrane receptors, including ion channel-linked receptors, enzyme-linked receptors, and G protein-coupled receptors, which activate intracellular signaling proteins upon ligand binding.
Cell signaling pathways allow communication between cells through the use of intracellular and extracellular messengers. They are broadly classified as pathways initiated by lipid-soluble messengers, like steroid hormones, or water-soluble messengers, like most hormones and neurotransmitters. The pathways involve messenger binding to receptors which then activates intracellular proteins, resulting in changes in gene transcription, ion channels, or enzymatic activity. This leads to cellular responses like changes in metabolism, secretory activity, or proliferation. In orthodontics, these pathways govern processes like osteoblast differentiation during bone formation and osteoclast recruitment during bone resorption in response to mechanical forces.
Cell signaling allows cells to communicate and coordinate their actions through chemical signals. There are different types of cell signaling including autocrine, paracrine, endocrine, and juxtacrine signaling. The process of cell signaling involves signal synthesis, transport, receptor binding, signal transmission, interpretation, and termination. Understanding cell signaling is important for treating diseases and engineering tissues, as errors in signaling can cause cancer, autoimmunity, and diabetes. The cell cycle is tightly regulated and consists of growth, DNA replication, and division phases. Key regulators of the cell cycle include cyclins, cyclin-dependent kinases, and cyclin-dependent kinase inhibitors that promote or inhibit cell cycle progression at checkpoints.
The immune system consists of primary and secondary lymphoid organs that work together. Primary lymphoid organs include the thymus, bone marrow, and bursa of fabricus, where immune cells mature and develop. Secondary lymphoid organs, such as lymph nodes and the spleen, expose mature immune cells to antigens in circulation and further activate the immune response. The thymus educates T cells, while the bone marrow produces B cells and other immune cells through hematopoiesis. Lymph nodes and the spleen then filter antigens from lymph and blood to activate mature B and T cells.
The Cell signalling is part of any communication process that governs basic activities of cells and coordinates all cell actions.
The ability of cells to perceive and correctly respond to their microenvironment is the basis of development,tissue repair, immunity, tissue homeostasis.
The cell membrane receptors and internal receptors have been discussed along with current trends in cell signalling.
1. Visualization of cell signalling
2. Stem cells and cell signalling
ntroduction
2. Definition
3. Steps Of Signal Transduction
A) Reception
B) Transduction
C) Induction
4. Important component used in Signal Transduction
A) Calcium ion as second messenger
B) Protein Kinase
Types of Signal Transduction
A) Extra cellular Signal Transduction
B) Intra cellular Signal Transduction
C) Inter cellular Signal Transduction
6. Mechanism of Signal Transduction
A) GPCR pathway
B) RTK pathway
7. Example of Signal Transduction
A) In plants
B) In animals
8. Conclusion
9. Reference…
Biswajit Sahoo presented on signal transduction. Signal transduction is the process by which signals from outside the cell are converted into a form that the cell can use, through a series of molecular interactions along a signal pathway. There are three main stages: reception of the signal by a receptor on or inside the cell membrane, transduction or conversion of the signal within the cell, and response by the cell. Two important signal pathways discussed are the Ras/Raf/MAP kinase pathway involved in cell growth and differentiation, and the Jak/Stat pathway activated by cytokines to control inflammatory responses. Understanding signal transduction can help develop crop varieties with improved resistance to pathogens or tolerance to stresses.
Assignment on Need of cell signaling, Steps in cell signaling, Intercellular signaling pathways, Types of intercellular signaling pathways, Intracellular signaling pathways, Receptors, Intercellular and intracellular signaling pathways. Classification of receptor family and molecular structure ligand gated ion channels; Gprotein coupled receptors, tyrosine kinase receptors and nuclear receptors.
GENERAL IDEA OF SIGNAL TRANSDUCTION
DEFINATION
WHAT DOES THE TERM SIGNAL TRANSDUCTION MEANS
HISTORY
BASIC ELEMENTS IN SIGNAL TRANSDUCTION
TYPES OF SIGNAL TRANSDUCTION
SIGNALLING MOLECULE
RECEPTOR MOLECULE
MODES OF CELL CELL SIGNALING
SECOND MESSENGER
SIGNAL TRANSDUCTION PATHWAY
SOME SIGNALING PATHWAYS
SIGNIFICANCE
CONCLUSION
REFERENCE
Cell signaling occurs through four main categories: paracrine, autocrine, endocrine, and direct contact. Paracrine signaling involves short-range signals between nearby cells, such as synaptic signaling between neurons. Autocrine signaling allows cells to signal to themselves. Endocrine signaling uses the circulatory system to transmit long-range hormones from endocrine glands. Direct contact signaling transfers small molecules through gap junctions between cells. Intracellular signaling pathways transmit extracellular signals through phosphorylation cascades like the MAPK, JNK, p38, and PI3K pathways, ultimately influencing cell behavior.
The document discusses receptor tyrosine kinases (RTKs), a class of cell surface receptors that possess intrinsic tyrosine kinase activity. RTKs are activated through ligand binding and dimerization, which leads to autophosphorylation and downstream signaling. This signaling involves phosphorylation of proteins by RTKs and recruitment of adapter proteins, and results in cellular responses like cell division, differentiation, and motility. Common to all RTKs are an extracellular ligand-binding domain, a transmembrane domain, an intracellular tyrosine kinase domain, and regulatory domains.
Introduction
Protein modifications
Folding
Chaperon mediated
Enzymatic
Cleavage
Addition of functional groups
Chemical groups
Hydrophobic groups
Proteolysis
Conclusion
Reference
The JAK-STAT pathway is a key cell signaling pathway that communicates information from extracellular signaling molecules called cytokines into the cell nucleus. It involves three main components: Janus kinases (JAKs) that associate with cytokine receptors and become activated by phosphorylation upon cytokine binding, signal transducers and activators of transcription (STATs) that are phosphorylated by JAKs and then form dimers that translocate to the nucleus to regulate gene expression, and cytokine receptors that dimerize upon cytokine binding to bring associated JAKs together for cross-phosphorylation and activation of the pathway. The JAK-STAT pathway regulates many important cellular processes like proliferation, differentiation, and immune responses by transmitting signals from cytokines and stimulating
Protein Import & Mitochondrial AssemblyAnkit Alankar
This document discusses protein import into mitochondria. It describes how most mitochondrial proteins are synthesized in the cytosol and contain targeting sequences that direct their import through translocases in the outer and inner mitochondrial membranes. The Tom complex handles transport across the outer membrane, while the Tim23 complex mediates import through the inner membrane. Molecular chaperones maintain imported proteins in an unfolded state as they pass through the translocases with the help of membrane potentials.
Protein targeting or protein sorting is the mechanism by which a cell transports to the appropriate positions in the cell or outside of it. Both in prokaryotes and eukaryotes, newly synthesized proteins must be delivered to a specific sub-cellular location or exported from the cell for correct activity. This phenomenon is called protein targeting. Protein targeting is necessary for proteins that are destined to work outside the cytoplasm.This delivery process is carried out based on information contained in the protein itself. Correct sorting is crucial for the cell; errors can lead to diseases. In 1970, Günter Blobel conducted experiments on the translocation of proteins across membranes. He was awarded the 1999 Nobel Prize for his findings. He discovered that many proteins have a signal sequence, that is, a short amino acid sequence at one end that functions like a postal code for the target organelle.
The document discusses various pathways of protein trafficking in cells. It describes how proteins are targeted to different organelles like the endoplasmic reticulum, Golgi apparatus, mitochondria, chloroplasts, peroxisomes, and lysosomes. Proteins can be targeted co-translationally as they are synthesized or post-translationally after completion. The ER and Golgi play important roles in modifying proteins through folding, glycosylation and sorting before they are packaged into vesicles and transported to their final destinations. Defects in these trafficking pathways can lead to human diseases.
The document discusses signal transduction, which is the process by which extracellular signals are converted into intracellular responses. There are six main steps: 1) synthesis and release of signaling molecules, 2) transport to target cell, 3) detection by receptor, 4) change in cell function triggered by receptor-signal complex, 5) removal of signal, and 6) termination of response. Signal transduction involves cell surface receptors and intracellular receptors that bind ligands and mediate specific cellular responses. Major types of signaling include endocrine, paracrine, and autocrine signaling.
Cells need to communicate both within multicellular organisms and between unicellular organisms. Communication allows cells to respond to their environment and coordinate behaviors. Cell communication involves three main steps: reception of a signal molecule by a receptor, transduction of the signal through intracellular pathways, and response through activities in the cytoplasm or nucleus. Pathways amplify signals and allow for specific responses in different cell types through varied protein expression. Termination mechanisms inactivate signaling to end the cellular response.
Cell Signaling is a phenomenon in which cells receive and respond to the signals or chemical messages from their internal environment or from the neighbouring cells.
Cell signaling involves chemical communication between cells through signaling molecules that bind to receptors on other cells. When a signaling molecule binds its receptor, it triggers a change within the cell through a process called signal transduction. This allows cells to respond to their environment and coordinate their actions. There are several types of cell signaling including paracrine signaling between nearby cells, endocrine signaling through hormones carried in the bloodstream, and autocrine signaling where cells produce factors to stimulate themselves. Cell surface receptors that span the membrane play an important role in signal transduction.
Cell signaling involves communication between cells through extracellular signaling molecules that bind to receptor proteins on the cell surface or inside the cell. These receptors activate intracellular signaling pathways that lead to changes in target proteins and cell behavior. The major types of cellular signaling pathways are those using membrane receptors, including ion channel-linked receptors, enzyme-linked receptors, and G protein-coupled receptors, which activate intracellular signaling proteins upon ligand binding.
Cell signaling pathways allow communication between cells through the use of intracellular and extracellular messengers. They are broadly classified as pathways initiated by lipid-soluble messengers, like steroid hormones, or water-soluble messengers, like most hormones and neurotransmitters. The pathways involve messenger binding to receptors which then activates intracellular proteins, resulting in changes in gene transcription, ion channels, or enzymatic activity. This leads to cellular responses like changes in metabolism, secretory activity, or proliferation. In orthodontics, these pathways govern processes like osteoblast differentiation during bone formation and osteoclast recruitment during bone resorption in response to mechanical forces.
This document summarizes the cyclic AMP (cAMP) signaling pathway. It describes how extracellular signaling molecules called first messengers bind to G protein-coupled receptors, activating G proteins that stimulate the enzyme adenylyl cyclase to produce the second messenger cAMP. cAMP then activates the protein kinase A pathway and triggers cellular responses. Negative feedback mechanisms like phosphorylation and recruitment of arrestins terminate the signal by desensitizing the receptor. The cAMP pathway is an important intracellular signaling system that relays signals from surface receptors to drive changes in cell metabolism, proliferation, and other functions.
g protein coupled receptors, ion channels, types of receptors, wnt signalling, cell signalling, tranduction pathway, disorders regarding the signalling
This document provides an overview of signal transduction mechanisms. It discusses various types of receptors including G protein-coupled receptors, receptor tyrosine kinases, integrins, toll-like receptors and ligand-gated ion channels. It describes how extracellular ligands bind to cell surface receptors and initiate intracellular signaling pathways such as the cAMP pathway and phosphatidylinositol pathway. Defects in these signaling pathways can lead to diseases. The document provides details on the mechanisms of G protein-coupled receptor signaling and downstream effects.
Cell signaling allows cells to communicate and respond to their environment. Extracellular signaling molecules bind to receptors on cells, which then activate intracellular responses. Prokaryotes use quorum sensing to coordinate behaviors based on population density. Eukaryotic signaling is more complex, with over 1500 receptor types in humans. Signaling pathways are classified by the signaling molecule (hormone, neurotransmitter, cytokine) and can cause changes like gene expression, enzyme activity, or cell movement. Defects in signaling can lead to diseases, making cell signaling an important area of research.
The document discusses various types of signal transduction in cells. It describes how extracellular signals like hormones bind to cell surface receptors and trigger intracellular signaling pathways using second messengers. These pathways involve G proteins and the production of molecules like cyclic AMP and inositol triphosphates to activate enzymes like protein kinase A and C. This leads to changes in gene expression, metabolism and cell behavior in response to extracellular signals.
Cells communicate through signaling molecules that are detected by receptors on other cells. Signals are transmitted across the cell membrane by signal transduction pathways and cause changes in cell function. Signals may target nearby (paracrine), distant (endocrine), or adjacent (juxtacrine) cells. Ion channels in the cell membrane are important for signal transduction and are classified by their method of gating, such as ligand-gated channels that open in response to neurotransmitters.
The document discusses oligogalacturonide (OG) signaling in plant innate immunity. It provides background on how plant pathogens produce pectin degrading enzymes that release OG fragments from plant cell walls, which are recognized as damage-associated molecular patterns (DAMPs) that activate immune responses. It describes previous work where activation tagging was used in Arabidopsis to identify OG-tolerant mutants, and issues replicating the results. New screening methods are proposed, such as growing seedlings directly in liquid medium in 96-well plates and selecting tolerant seedlings after adding OGs.
The cell cycle is regulated by cyclin-dependent kinases (Cdks) whose activity oscillates throughout the cycle. Cdks form complexes with cyclins, which activate the Cdks and determine which phase of the cycle they control. The cyclin-Cdk complexes phosphorylate target proteins to promote replication and mitosis. Progression through the cell cycle is also controlled by ubiquitin ligases and phosphorylation/dephosphorylation events. The cycle operates through a series of switches that trigger irreversible events, keeping it tightly regulated and coordinated.
This document discusses second messenger systems, which relay signals from cell surface receptors to target molecules inside cells. There are three major classes of second messenger systems: 1) the adenylyl cyclase-cAMP system, which is activated by hormones like epinephrine and glucagon and uses cAMP as the second messenger; 2) the phospholipid system, which uses IP3 and DAG as second messengers; and 3) the calcium-calmodulin system, where calcium acts as the second messenger and binds to and activates calmodulin. These second messengers amplify signals and allow hormones and neurotransmitters to trigger intracellular responses.
5. tumor suppressor genes dr. sinhasan, mdzahkciapm
Tumour suppressor genes regulate cell growth and help prevent tumor formation. When both copies of a tumour suppressor gene are inactivated due to mutations or deletions, cancer can develop. Some important tumour suppressor genes include Rb, p53, APC, and WT1. Rb regulates the cell cycle and its inactivation leads to retinoblastoma and other cancers. p53 is called the "guardian of the genome" as it arrests the cell cycle if DNA is damaged and initiates apoptosis; its mutation is common in many cancer types. APC inactivation causes colon polyps and cancer. Loss of tumour suppressor gene function allows abnormal cell growth and proliferation that can form tumors if unchecked.
The document summarizes plant signal transduction and hormone pathways. It describes 3 main steps in signal transduction - reception, transduction, and response. It then discusses 5 major plant hormones - auxin, gibberellins, cytokinins, ethylene, and abscisic acid - and their roles in processes like growth, ripening, dormancy, and responses to stimuli. It concludes with details of plant reproduction, including the roles of flowers, double fertilization in angiosperms, and formation of seeds.
Tumor suppressor genes regulate cell growth and division. When functioning properly, they inhibit tumor formation but when mutated or inactivated, they lose this ability. Examples include p53, Rb, APC, BRCA1, BRCA2. p53 is mutated in 50% of cancers and regulates DNA repair/cell cycle arrest or apoptosis. Li-Fraumeni syndrome results from germline p53 mutations increasing cancer risk. The APC gene regulates beta-catenin to control cell growth. Mutations in tumor suppressor genes are often required for tumor development according to the two-hit hypothesis as seen with retinoblastoma caused by Rb mutations.
describe the tumor suppressor genes and examples for downloading the presentation, more presentations , infographics and blogs visit :
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Second messengers are intracellular signaling molecules that are released within cells in response to extracellular first messengers like hormones and neurotransmitters. They amplify and propagate intracellular signals. Examples include cyclic AMP (cAMP), cyclic GMP (cGMP), inositol trisphosphate, and calcium. cAMP and cGMP are produced from ATP and GTP by adenylate and guanylate cyclases, respectively. They activate downstream effector proteins like protein kinase A and G. This leads to phosphorylation of various target proteins and physiological responses like metabolism, gene expression, cell survival, proliferation and apoptosis. The document discusses the mechanisms, targets, functions and therapeutic applications of cAMP and cGMP second messenger systems in detail.
Cell signaling allows cells to communicate and coordinate their actions. It is important for processes like growth, development, and immunity. There are different types of cell signaling including direct cell-cell signaling and signaling by secreted molecules. Signaling molecules bind to receptors on target cells and can regulate gene expression. Examples of signaling molecules include hormones, gases like nitric oxide, and intracellular signaling molecules like steroid hormones.
Cell signaling pathways allow cells to communicate via extracellular signaling molecules and receptors. The document discusses intracellular signaling pathways activated by extracellular ligands binding to cell surface or intracellular receptors. It describes common signaling molecules like hormones, neurotransmitters, and growth factors that activate receptors and trigger intracellular signaling cascades involving second messengers like cAMP, IP3, DAG, and calcium ions. These cascades ultimately regulate cellular functions and gene expression. The key components of signaling pathways - ligands, receptors, G-proteins, second messengers, and effector proteins - are explained in detail.
Cell signaling pathways allow cells to communicate via extracellular signaling molecules and receptors. The document discusses intracellular signaling pathways activated by extracellular ligands binding to cell surface or intracellular receptors. It describes common signaling molecules like hormones, neurotransmitters, and growth factors that activate receptors and trigger intracellular signaling cascades involving second messengers like cAMP, IP3, DAG, and calcium ions. These cascades ultimately regulate cellular functions and gene expression. The key components of signaling pathways - ligands, receptors, G-proteins, second messengers, and intracellular signaling proteins - are defined.
1. Cell signaling involves the release and reception of molecules that allow cells to communicate with each other and their environment.
2. There are several modes of cell signaling including paracrine, endocrine, autocrine, neuronal, and juxtacrine signaling.
3. Cell signaling pathways involve the binding of ligands to receptors which activates intracellular signaling cascades through second messengers and protein phosphorylation/dephosphorylation to induce downstream cellular responses.
This Presentation provides an outline knowledge about Cellular Communication, Steps involved, Its Types, Signal Transduction, Secondary Messenger , Receptors with some Interesting Facts and Current Trends. An assignment for the subject, Cellular and Molecular Pharmacology, 1st year M.Pharm, 1st semester.
This document discusses intracellular and extracellular cell signaling. It defines cell signaling as communication between cells using chemical signals or ligands. Extracellular signaling occurs between cells and can be contact-dependent, paracrine, synaptic, or endocrine. Intracellular signaling involves signal transduction across the cell membrane and secondary messengers that activate intracellular signaling pathways involving protein phosphorylation or GTP-binding proteins. Key signaling pathways include G-protein coupled receptors and receptor tyrosine kinases that activate intracellular cascades to regulate processes like gene expression, cell growth, and metabolism.
Cell signaling is the process where cell communicate with each other with the help of signaling molecules and receptors. Cell signaling is done by different types of signaling processes such as autocrine, paracrine, synaptic, endocrine, contact dependent signaling
The document summarizes the biochemistry of the vascular system. It describes how blood is pumped through arteries and returns via veins, exchanging nutrients and waste through capillaries. It focuses on the endothelium and adhesion molecules that allow immune cells to exit blood vessels at sites of infection. Selectins mediate initial attachment and rolling of leukocytes along endothelium. Integrins and cellular adhesion molecules then firm attachment and transmigration. The endothelium regulates vascular tone and homeostasis through nitric oxide, prostacylandins, and other factors.
The document discusses the endothelium and the role of nitric oxide (NO) in the body. It defines the endothelium as the thin layer of cells lining blood vessels and lymphatic vessels. Endothelial cells release NO, previously called endothelium-derived relaxing factor (EDRF), which modulates blood vessel tone. NO is a gaseous signaling molecule synthesized from L-arginine by nitric oxide synthase (NOS). NO has many roles, including regulating circulation and the nervous, immune, digestive, and reproductive systems. It acts as a vasodilator, neurotransmitter, and plays roles in wound healing and apoptosis.
Cellular signaling allows cells to communicate with each other and coordinate functions through signal transduction pathways. Environmental stimuli can initiate these pathways, transmitting signals from one cell to another via extracellular signaling molecules like hormones or direct cell contact. There are several types of cellular receptors that receive these signals, including cell surface receptors which span the membrane and contain extracellular, transmembrane, and intracellular domains to transmit the signal inside the cell. Binding of ligands to different types of receptors can have varied effects through mechanisms like activating intracellular enzymes or changing receptor conformation.
Cell surface and intrcellular receptorsEstherShoba1
Cell surface and intracellular receptors play important roles in signal transduction. There are two main types of receptors - internal receptors located in the cytoplasm that directly influence gene expression, and cell surface receptors that span the plasma membrane and convert extracellular signals into intracellular signals. Cell surface receptors include enzyme-linked receptors with intracellular enzyme domains, ion channel-linked receptors that open channels for ion flow, and G-protein-linked receptors that activate intracellular G-proteins to transmit signals. Defects in cell surface receptors can cause diseases.
Chemical transmission in the nervous system neurotransmitter.pptxshama praveen
Otto Loewi discovered acetylcholine as the first neurotransmitter through experiments transferring fluid from a frog heart. Neurotransmitters are endogenous chemicals that transmit signals across synapses. They include small molecules like acetylcholine, serotonin, histamine, and amino acids as well as larger neuropeptides. They act on receptors that are either ligand-gated ion channels or G protein-coupled receptors. Neurotransmitters are synthesized, stored in vesicles, released into the synaptic cleft upon neuronal firing, where they can bind receptors or be recycled back up into neurons via transporters.
Steroid hormones are lipid-soluble chemical messengers derived from cholesterol that transport signals between cells. They are synthesized and immediately released near their target cells. Since they are lipid-soluble, steroid hormones diffuse freely into cells and are carried in the bloodstream bound to transport proteins. Within target cells, steroid hormones bind to intracellular receptors that act as transcription factors to increase or decrease the expression of specific genes and thereby influence various physiological processes like carbohydrate regulation, mineral balance, and reproductive functions.
Otto Loewi discovered acetylcholine as the first neurotransmitter in 1936. Neurotransmitters are endogenous chemicals that transmit signals across synapses. They can be small molecules like acetylcholine, serotonin, histamine, catecholamines, amino acids, or large molecules like neuropeptides. Neurotransmitters are stored in vesicles and released by exocytosis. They act on receptors, which can be ligand-gated ion channels or G protein-coupled receptors. Reuptake and catabolism terminate neurotransmitter action. The major neurotransmitters, their locations, synthesis, release, receptors, and fate were described in detail.
CELL SIGNALING biokimia dan biologi .pptxErlaNurani
This document discusses cell signaling pathways. It begins by introducing how cells communicate via signaling molecules and receptors. It then describes various types of signaling molecules and receptors, including steroid hormones, nitric oxide, neurotransmitters, peptides, and receptor tyrosine kinases. Specific signaling pathways are explained, such as G protein-coupled receptors, cAMP, MAP kinase, PI3 kinase, TGF-β, NF-κB, JAK-STAT, and mTOR. The document concludes by noting the dynamic and interconnected nature of cellular signaling networks.
Molecular interaction, Regulation and Signalling receptors and vesiclesAnantha Kumar
1. Overview of Extracellular signalling
2. Signalling molecules operate over various distance in animals
3.Endocrine Signalling
4.Paracrine Signalling
5.Autocrine Signalling
6. Signalling by Plasma membrane attached proteins
7.Receptors
8 Properties of receptors
9.Cell surface receptors belong to four major classes
10.Signal transduction Mechanism
11. Second messenger
12. Contraction of skeletal Muscle cells mechanism
A substance that is released at a synapse by a neuron and that effects another cell, either a neuron or an effectors organ, in a specialized manner , called neurotransmitter.
Both the nervous system and endocrine system regulate physiological processes, though they differ in their communication methods and response times. The endocrine system uses hormones like epinephrine, while the nervous system uses neurotransmitters. Key endocrine glands include the hypothalamus, pituitary gland, thyroid gland, adrenal glands, pancreas, ovaries/testes, and thymus gland. Hormone signaling occurs via models like the steroid model or protein model and involves signal transduction pathways.
Immersive Learning That Works: Research Grounding and Paths ForwardLeonel Morgado
We will metaverse into the essence of immersive learning, into its three dimensions and conceptual models. This approach encompasses elements from teaching methodologies to social involvement, through organizational concerns and technologies. Challenging the perception of learning as knowledge transfer, we introduce a 'Uses, Practices & Strategies' model operationalized by the 'Immersive Learning Brain' and ‘Immersion Cube’ frameworks. This approach offers a comprehensive guide through the intricacies of immersive educational experiences and spotlighting research frontiers, along the immersion dimensions of system, narrative, and agency. Our discourse extends to stakeholders beyond the academic sphere, addressing the interests of technologists, instructional designers, and policymakers. We span various contexts, from formal education to organizational transformation to the new horizon of an AI-pervasive society. This keynote aims to unite the iLRN community in a collaborative journey towards a future where immersive learning research and practice coalesce, paving the way for innovative educational research and practice landscapes.
The technology uses reclaimed CO₂ as the dyeing medium in a closed loop process. When pressurized, CO₂ becomes supercritical (SC-CO₂). In this state CO₂ has a very high solvent power, allowing the dye to dissolve easily.
ESR spectroscopy in liquid food and beverages.pptxPRIYANKA PATEL
With increasing population, people need to rely on packaged food stuffs. Packaging of food materials requires the preservation of food. There are various methods for the treatment of food to preserve them and irradiation treatment of food is one of them. It is the most common and the most harmless method for the food preservation as it does not alter the necessary micronutrients of food materials. Although irradiated food doesn’t cause any harm to the human health but still the quality assessment of food is required to provide consumers with necessary information about the food. ESR spectroscopy is the most sophisticated way to investigate the quality of the food and the free radicals induced during the processing of the food. ESR spin trapping technique is useful for the detection of highly unstable radicals in the food. The antioxidant capability of liquid food and beverages in mainly performed by spin trapping technique.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
ESA/ACT Science Coffee: Diego Blas - Gravitational wave detection with orbita...Advanced-Concepts-Team
Presentation in the Science Coffee of the Advanced Concepts Team of the European Space Agency on the 07.06.2024.
Speaker: Diego Blas (IFAE/ICREA)
Title: Gravitational wave detection with orbital motion of Moon and artificial
Abstract:
In this talk I will describe some recent ideas to find gravitational waves from supermassive black holes or of primordial origin by studying their secular effect on the orbital motion of the Moon or satellites that are laser ranged.
Travis Hills of MN is Making Clean Water Accessible to All Through High Flux ...Travis Hills MN
By harnessing the power of High Flux Vacuum Membrane Distillation, Travis Hills from MN envisions a future where clean and safe drinking water is accessible to all, regardless of geographical location or economic status.
Describing and Interpreting an Immersive Learning Case with the Immersion Cub...Leonel Morgado
Current descriptions of immersive learning cases are often difficult or impossible to compare. This is due to a myriad of different options on what details to include, which aspects are relevant, and on the descriptive approaches employed. Also, these aspects often combine very specific details with more general guidelines or indicate intents and rationales without clarifying their implementation. In this paper we provide a method to describe immersive learning cases that is structured to enable comparisons, yet flexible enough to allow researchers and practitioners to decide which aspects to include. This method leverages a taxonomy that classifies educational aspects at three levels (uses, practices, and strategies) and then utilizes two frameworks, the Immersive Learning Brain and the Immersion Cube, to enable a structured description and interpretation of immersive learning cases. The method is then demonstrated on a published immersive learning case on training for wind turbine maintenance using virtual reality. Applying the method results in a structured artifact, the Immersive Learning Case Sheet, that tags the case with its proximal uses, practices, and strategies, and refines the free text case description to ensure that matching details are included. This contribution is thus a case description method in support of future comparative research of immersive learning cases. We then discuss how the resulting description and interpretation can be leveraged to change immersion learning cases, by enriching them (considering low-effort changes or additions) or innovating (exploring more challenging avenues of transformation). The method holds significant promise to support better-grounded research in immersive learning.
Mending Clothing to Support Sustainable Fashion_CIMaR 2024.pdfSelcen Ozturkcan
Ozturkcan, S., Berndt, A., & Angelakis, A. (2024). Mending clothing to support sustainable fashion. Presented at the 31st Annual Conference by the Consortium for International Marketing Research (CIMaR), 10-13 Jun 2024, University of Gävle, Sweden.
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
The cost of acquiring information by natural selectionCarl Bergstrom
This is a short talk that I gave at the Banff International Research Station workshop on Modeling and Theory in Population Biology. The idea is to try to understand how the burden of natural selection relates to the amount of information that selection puts into the genome.
It's based on the first part of this research paper:
The cost of information acquisition by natural selection
Ryan Seamus McGee, Olivia Kosterlitz, Artem Kaznatcheev, Benjamin Kerr, Carl T. Bergstrom
bioRxiv 2022.07.02.498577; doi: https://doi.org/10.1101/2022.07.02.498577
PPT on Direct Seeded Rice presented at the three-day 'Training and Validation Workshop on Modules of Climate Smart Agriculture (CSA) Technologies in South Asia' workshop on April 22, 2024.
2. • All cells receive and respond to signals from their
environment
• The behaviour of cell signalling is accomplished by a
variety of signalling molecules that are either
secreted or expressed on the cell surface and bind
to receptors expressed by other cells.
• The bonding between signalling molecules and
receptors initiates a series of intracellular reactions
that regulate virtually all aspects of cellular
behaviour (metabolism, movement, proliferation,
survival and differentiation).
Jan 18, 2017 2
3. SIGNAL MOLECULES AND THEIRSIGNAL MOLECULES AND THEIR
RECEPTORSRECEPTORS
Jan 18, 2017 3
4. • Many different kinds of molecules transmit
information between the cells.
• Although all these molecules act as ligands that
bind to the receptors expressed by their target
cells, there is a considerable variation in the
structure and function of the different types of
molecules that serve signal transmitters.
• Some of these molecules carry signals over long
distances whereas others act locally.
• Some signalling molecules are able to cross the
plasma membrane and bind to intracellular
receptors in the cytoplasm or nucleus.
Jan 18, 2017 4
6. • Cell signalling can result either from the direct
interaction of a cell with its neighbour or from the
action of secreted signalling molecules.
• Signalling by direct Cell-Cell interactions play a
critical role in regulating the behaviour of cells in
animal tissues- in the embryonic development as
well as in the maintenance of adult tissues.
• The varieties of signalling are frequently divided
into three general categories based on the distance
over which the signals are transmitted.
– A) Endocrine Signalling
– B) Paracrine Signalling
– C) Autocrine SignallingJan 18, 2017 6
8. • In endocrine signalling, the signalling molecules
(hormones) are secreted by specialised endocrine
cells and carried to the target cells through
circulation. A classical example is provided by the
steroid hormone estrogen, which is produced by
the ovary and stimulates development and
maintenance of the female reproductive system,
secondary sexual characters. In animals more than
50 different hormones are produced by endocrine
glands.
• In contrast, some signalling molecules act locally to
affect the behaviour of nearby cells. In paracrine
signalling, molecules released by one cell……………..Jan 18, 2017 8
9. • ……..acts on neighbouring target cells. An example
is provided by the action of neurotransmitters in
carrying signal between the nerve cells at a
synapse.
• Finally, some cells respond to signalling molecules
that are produced by themselves. One important
example of such autocrine signalling is the response
of cells of vertebrate immune system to foreign Ag.
Certain types of T cells respond to antigenic
stimulation by synthesising a growth factor that
drives their own proliferation, thereby increasing
the number of responsive T cells and amplifying
immune response. It is also noteworthy that………..Jan 18, 2017 9
10. • …….abnormal autocrine signalling frequently
contributes to the uncontrolled growth of
cancerous cells. In this situation a cancer produces
a growth factor to which it also responds, thereby
continuous driving its own unregulated
proliferation.
Jan 18, 2017 10
11. STEROID HORMONES AND NUCLEARSTEROID HORMONES AND NUCLEAR
RECEPTOR SUPERFAMILYRECEPTOR SUPERFAMILY
Jan 18, 2017 11
12. • In many cases, receptors are expressed on the
target cell surface but some receptors are
intracellular proteins located in the cytosol or in the
nucleus.
• These intracellular receptors respond to small
hydrophobic signalling molecules that are able to
diffuse across the plasma membrane.
• The steroid hormones are the classical examples of
this group of signalling molecules which also include
thyroid hormones, Vitamin D3 and retinoic acid.
Jan 18, 2017 12
13. • The steroid hormones (testosterone, estrogen,
progesterone, corticosteroids and ecdysone) are all
synthesised from cholesterol.
• The testosterone, progesterone and estrogen are
sex steroids, which are produced by gonads. The
corticosteroids are produced by adrenal cortex-they
include glucocorticoids, mineralocorticoids etc. The
ecdysone is an insect hormone that play a key role
in development by triggering the metamorphosis of
larvae to adults.
• Although thyroid hormone, vitamin D3 and retinoic
acid are structurally distinct from steroids, they
share a common mechanism of action in their
target cells.
Jan 18, 2017 13
14. • Thyroid hormone (thyroxin) is synthesised in the
thyroid gland; it plays important role in
development and regulation of metabolism.
• Vitamin D3 regulates calcium metabolism and bone
growth .
• Retinoic acid and related compounds synthesised
from vitamin A plays an important role in
vertebrate development.
Jan 18, 2017 14
15. • Because of their hydrophobic character, the steroid
hormones, thyroid hormone, vitamin D3 and
retinoic acid are all able to enter cells by diffusing
across the plasma membrane. Once inside, they
bind to intracellular receptors. These receptors
which are members of a family of proteins known
as the Nuclear Receptor Superfamily, are
transcription factors that contain related domains
for (a)ligand binding, (b)DNA binding and
(c)transcriptional activation.
• Ligand binding regulates functions as Activators or
Repressors of their target genes, so the steroid
hormones and related compounds directly regulate
gene expression.
Jan 18, 2017 15
16. • Ligand binding has distinct effect on different
receptors.
• Some members of the steroid receptor superfamily
are unable to bind DNA in the absence of hormone.
Estrogen receptors, for example, bind to the Hsp 90
chaperones in the absence of hormone. The binding
of estrogen induces a conformational change in the
receptor, displacing Hsp 90 and leading to the
formation of receptor dimers that bind to
regulatory DNA sequences and activate
transcription of target genes
Jan 18, 2017 16
18. • In other cases, the thyroid hormone receptor for
example, is associated with a Corepressor Complex
and represses transcription of its target genes.
Hormone binding induces a conformationational
change that results in the interaction of the
receptor with Coactivators rather than
Corepressors, leading to transcriptional activation
of thyroid hormone-inducible genes.
Jan 18, 2017 18
19. NITRIC OXIDE AND CARBONNITRIC OXIDE AND CARBON
MONOXIDEMONOXIDE
Jan 18, 2017 19
20. • The simple gas nitric oxide (NO) is a major paracrine
signalling molecule in the nervous, immune and
circulatory systems.
• Like steroid hormones, NO is able to diffuse directly
across the plasma membrane of its target cells. The
molecular action of NO is however, distinct from
that of steroid hormones- rather than binding to
the receptors that regulate transcription, NO alters
the activity of intracellular target enzymes.
• NO is synthesised from amino acid arginine by the
enzyme nitric oxide synthase. Once synthesised, NO
diffuses out of the cell and can act locally to affect
nearby cell.Jan 18, 2017 20
21. • Its action is restricted to such local action because
NO is extremely unstable with a half life of only few
seconds.
• The major intracellular target of NO is guanylyl
cyclase. NO binds to a haeme group of active site of
this enzyme stimulating synthesis of second
messenger cyclic GMP. In addition, NO may directly
modify some target proteins by nitrosylation of
cysteine residue.
Jan 18, 2017 21
23. • A well-characterised example of NO action is signalling
the dilation of blood vessels. The first step in this
process is the release of neurotransmitters, such as
acetylcholine, from the termini of nerve cells in the
blood vessel wall. These neurotransmitters act on
endothelial cells to stimulate NO synthesis. NO then
diffuses to neighbouring smooth muscle cells where it
activates guanylyl cyclase resulting in the synthesis of
cGMP, which induces muscle cell relaxation and blood
vessel dialatation.
• It is also interesting to note that the medical use of
nitroglycerine in treatment of heart disease is based on
its conversion to NO, which dilates coronary blood
vessels and increases blood flow to the heart.Jan 18, 2017 23
24. • Another simple gas carbon monoxide (CO) also
functions as signalling molecule in the nervous
system.
• CO is closely related to and appears to act similarly
as a neurotransmitter and mediator of blood vessel
dilation. The synthesis of CO in brain cells, like that
of NO is stimulated by neurotransmitters. In
addition, CO can stimulate guanylyl cyclase, which
may also represent the major physiological target of
CO signal.
Jan 18, 2017 24
25. Nitric oxide and Carbon Monoxide
NO, a simple gas, is able to diffuse across the membrane, and alters the
activity of intracellular target enzymes. It’s extremely unstable, so its effects are
local.
Mechanism.
Acetylcholine is released from the terminus of nerve cell in the blood
vessel wall. The endothelial cells are stimulated to produce NO (from arginine),
which causes an increased synthesis of GMP, a second messenger responsible for
blood vessel dilation.
Ach
Nerve cell endothelial cell
NO GMP Vessel dilationAchR
Jan 18, 2017 25
27. Neurotransmitters
They signal from neuron to neuron or from neuron to other target cell
(ex. muscle cell ).
Acetylcholine
Glycine
Glutamate
Dopamine
Epinephrine
Serotonin
Histamine
GABA.
Common features: hydrophilic molecules that bind to cell surface receptors.
The binding induces conformational changes that open ion channels
ion fluxes in the cell.
Jan 18, 2017 27
28. • The neurotransmitters (NTs) carry signals between
neurons or from neurons to other type of target cells
(muscle cells).
• They are diverse group of small hydrophlic molecules
including acetylcholine, dopamine, epinephrine,
serotonin, histamine, glutamate, glycine and GABA etc.
• The release of NTs is signalled by the arrival of an
action potential at the terminus of a neuron.
• The NTs then diffuse across the synaptic cleft and bind
to receptors on the target cell surface.
• Note that some NTs can also act as hormones- for
example- epinephrine functions both as NT and as a
hormone produced by adrenal to signal glycogen break
down in muscle cells.Jan 18, 2017 28
29. • Because the NTs are hydrophilic molecules they are
unable to cross the PM of their target cells.
Therefore, in contrast to the steroid hormones, NO
and CO, the NTs act by binding the cell surface
receptors.
• Many NT receptors are ‘ligand-gated ion channels’ ,
such as the acetylcholine receptor. NT binding to
these receptors induces a conformational change
that opens ion channels, directly resulting in
changes ion flux in the target cell.
• Other NT receptors are coupled to G proteins – a
major group of signalling molecules that that link
cell surface receptors to a variety of intracellular
responses.
Jan 18, 2017 29
31. PEPTIDE HORMONES AND GROWTHPEPTIDE HORMONES AND GROWTH
FACTORSFACTORS
Jan 18, 2017 31
32. • The widest variety of signalling molecules in animals
are peptides. This group includes peptide
hormones, neuropeptides and a diverse array of
growth factors.
• Well known example of peptide hormones include
insulin, glucagon and the hormones produced
pituitary gland.
• The neuropeptides, such as enkaphalins and
endorphins, function not only as NTs at synapse but
also as neurohormones that act on distant cells. The
enkaphalins and endorphins have been widely
studied because of their activities as natural
analgesics that decrease pain responses.Jan 18, 2017 32
33. • The pp growth factors include a wide variety of
signalling molecules.
• The first of this factor is nerve growth factor (NGF).
• NGF is a member of family of pp growth factor called
neurotrophins that regulate development and survival
of neurons.
• Epidermal growth factor (EGF) a 53 AAs pp, regulates
cell proliferation.
• A good example of growth factor activity is provided by
the activity of platelet-derived growth factor (PDGF) in
wound healing.
• PDGF is stored in blood platelets and released during
blood clotting at the site of wound. It then stimulates
the proliferation of fibroblasts, thereby contributing to
regrowth of damaged tissue.Jan 18, 2017 33
34. • Members of another large group of pp growth
factors, called cytokines, regulate development and
differentiation of blood cells and control the
activities of lymphocytes during immune response.
• Other pp growth factors, membrane-anchored
growth factors (MAGF) remains associated with the
plasma membrane and function specifically as
signalling molecule during direct cell-cell
interaction.
Jan 18, 2017 34
36. • Several types of lipids serve as signalling molecules
and these are member of a class of lipid family,
called ecosanoids which include prostaglandins,
prostacyclin, thromboboxanes and leukotrienes.
• They act autocrine and paracrine signalling
pathways.
• They stimulate a variety of responses including
blood platelets aggregation, inflammation and
smooth muscle contraction.
Jan 18, 2017 36
37. FUNCTIONS OF CELL SURFACEFUNCTIONS OF CELL SURFACE
RECEPTORSRECEPTORS
Jan 18, 2017 37
38. • Most ligands are responsible for cell-cell signalling
bind to the receptors on the surface of their target
cells.
• Some neurotransmitter receptors are ion gated ion
channel that directly control ion flux across the
plasma membrane.
• Other cell surface receptors (peptide hormones,
growth factors) act by regulating the activities of
intracellular proteins. These proteins then transmit
signals from the receptors to a series of additional
intracellular targets.
• Ligand binding to the receptor on the surface thus
initiates a chain of intracellular reactions, ultimately
reaching the target cell nucleus.Jan 18, 2017 38
40. • The largest family of cell surface receptors transmit
signals to intracellular targets via the intermediary
action guanine nucleotide binding proteins called G
Proteins. More than a thousand such G protein
receptors have been identified.
• The G protein coupled receptors are structurally
and functionally related to the proteins
characterised by seven membrane spacing α
helices.
• The binding of ligands to the extracellular domain
of these receptors induces a conformational change
that allows the cytosolic domain of the receptor to
bind to a G protein associated with the inner face of
plasma membrane.
Jan 18, 2017 40
41. • This interaction activates G protein, which then
dissociates from the receptor and carries the signal
to an intracellular target, which may be an enzyme.
• The discovery of G proteins came from studies of
hormones that regulate the synthesis of cAMP in
their target cells. cAMP is an important second
messenger that mediates cellular responses to a
variety of hormones.
Jan 18, 2017 41
42. • G proteins consist of three subunits designated α, β
and γ. They are frequently called heterotrimeric G
proteins to distinguish them from other guanine
nucleotide binding proteins.
• The α subunit binds guanine nucleotides, which
regulate G protein activity. In the resting state, α is
bound to GDP in a complex with β and γ. Hormone
binding induces a conformational change in the
receptor, such that the cytosolic domain of receptor
interacts with G protein and stimulates the release
of bound GDP and its exchange for GTP. The
activated GTP-bound α subunit then dissociates
from β and γ, which remain together and functions
as a βγ complex.
Jan 18, 2017 42
43. • Both the active GTP-bound α subunit and the βγ
complex then interact with their targets to elicit an
intracellular response.
• In addition to regulating target enzymes, both the α
and βγ subunits of some G proteins directly
regulate ion channels. A good example is provided
by the action of neurotransmitter acetylcholine on
heart muscle, which is distinct from its effect on
nerve and skeletal muscle.
Jan 18, 2017 43
44. G-Protein – Coupled Receptors
(Largest family of cell surface receptors)
cAMP is a second messenger that mediates cellular responses to a variety of
hormones.
Jan 18, 2017 44
45. Pathways of Intracellular SignalPathways of Intracellular Signal
TransductionTransduction
Jan 18, 2017 45
46. • Many cell surface receptors stimulate intracellular
target enzymes, which may be either directly linked
or indirectly coupled to receptors by G proteins.
• These intracellular enzymes serve as downstream
signalling elements that propagate and amplify the
signal initiated by ligand binding.
• In most cases, a chain of receptors transmits signals
from the cell surface to a variety of intracellular
targets- a process called intracellular signal
transduction.
Jan 18, 2017 46
47. The cAMP Pathway : SecondThe cAMP Pathway : Second
Messenger and ProteinMessenger and Protein
PhosphorylationPhosphorylation
Jan 18, 2017 47
48. • The intracellular signalling was first elucidated by
the studies the action hormone (epinephrine),
which signals the breakdown of glycogen to
glucose.
• In 1958, Sutherland discovered that the action of
epinephrine was mediated by an increase in
intracellular concentration of cAMP, leading to the
concept that cAMP is second messenger in
hormonal signalling.
• cAMP is formed from ATP by the action of adenylyl
cyclase and degraded to AMP by cAMP
phosphodiesterase.
Jan 18, 2017 48
50. The cAMP pathway : Second messengers and
Protein phosphorylation.
Cyclic AMP is synthesized from ATP by adenylyl cyclase and
degraded to AMP by cAMP phosphodiesterase.
Jan 18, 2017 50
51. The epinephrine receptor is
coupled to adenylyl cyclase via a G
protein that stimulates enzymatic
activity, thereby increasing the
intracellular concentration of cAMP.
Jan 18, 2017 51
53. How does cAMP then signal the breakdown of
glycogen?
•This and most other effects of cAMP in animal cells
are mediated by the action “cAMP dependent Protein
Kinase”or Protein Kinase A (PKA).
•The inactive form of PKA is a tetramer, consisting of
two catalytic and two regulatory subunits.
•cAMP binds to the regulatory subunits leading to
their dissociation from catalytic subunits.
•The free catalytic subunits are then enzymatically
active and able to phosphorylate the target proteins.
Jan 18, 2017 53
54. • In the regulation of glycogen metabolism, PKA
phosphorylates two target enzymes.
• The first is another protein kinase, phosphorylase
kinase, which is phosphorylated and activated by PKA.
The phosphorylase kinase, in turn, phosphorylates and
activates glycogen phosphorylase, which catalyses the
breakdown of glycogen to glucose-1-phosphate.
• In addition, PKA phosphorylates the enzyme glycogen
synthase , which catalyses glycogen synthesis. In this
case, however, phosphorylation inhibits enzymatic
activity.
• The elevation of cAMP and activation of PKA thus
blocks further glycogen synthesis at the same time as it
stimulates glycogen breakdown.Jan 18, 2017 54
56. This is an example of a cAMP mediated pathway: PKA is
activated by 4 molecules of cAMP that bind to the regulatory
subunits releasing the catalytic subunits of the PKA.
The active protein kinase phosphorylates two key enzymes that
control degradation of glycogen.
cAMP
Jan 18, 2017 56
57. • The chain of reactions leading from the epinephrine
receptor to glycogen phosphorylase provides a good
illustration of signal amplification (SA) during
intracellular signal transduction.
• Each molecule of epinephrine activates only a single
receptor. However, each receptor may activate up to a
hundred molecules of G protein signal transduction
(Gs).
• Each molecule of Gs then stimulates the enzymatic
activity of adenylyl cyclase , which can catalyse the
synthesis of many molecules of cAMP.
• SA continues as each molecule of PKA phosphorylates
many molecules of phosphorylase kinase, which in
turn, phosphorylates many molecules of glycogen
phosphorylase.Jan 18, 2017 57
58. • In many animal cells, increase in cAMP activates the
transcription of specific target genes that contain a
regulatory sequence called “cAMP response
element” (CRE). In this case, the signal is carried out
from the cytoplasm to the nucleus following its
release from regulator subunit.
• Within the nucleus PKA phosphorylates a
transcription factor called CREB (CRE binding
protein), leading to the recruitment of co-activators
and transcription of cAMP-inducible genes.
• Such regulation of gene expression by cAMP plays
important role in controlling proliferation, survival
and differentiation of a wide variety of animal cells,
as well as being implicated in learning and memory.
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59. • Although most effects of cAMP are mediated by
PKA, cAMP can also directly regulate ion channels,
independent of protein phosphorylation. cAMP
functions in this way as a second messenger
involved in sensing smells.
• Many of odorant receptors in the sensory neurons
in the nose are G protein coupled receptors that
stimulate adenylyl cyclase, leading to an increase
intracellular cAMP.
• Rather than stimulating PKA, cAMP in the system
directly opens sodium channels in the plasma
membrane, leading to membrane depolarisation
and initiation of nerve impulse.Jan 18, 2017 59
62. Phospholipids and Ca++
(another group of second messengers)
PIP2: PHOSPHATIDYLINOSITOL 4,5-BIPHOSPHATE
(a component of the plasma membrane)
Hydrolysis of PIP2 is activated by PLC (Phospholipase
C), and yields diacylglycerol and inositol phosphate
(IP3).
DAG: Diacylglycerol activates the protein kinase C
family, that play a crucial role in cell growth and
differentiation.
Jan 18, 2017 62
64. Ca++
Calcium cellular concentration is maintained low by pumps that
transport calcium across the plasma membrane and from the
cytosol inside the endoplasmic reticulum (ER).
High concentrations of calcium activate the functions of
proteins including protein kinase and phosphatases.
Many of the effects of calcium are mediated by the Ca++-
binding protein calmodulin, which is activated by calcium
binding when the concentration of cytosolic calcium increases
from 0.1 to 0.5 micromolar.
Calmodulin, in turn, binds to a variety of target proteins
including protein kinases (CaM).
Jan 18, 2017 64
65. One of the proteins activated by Ca/calmodulin is a kinase
called CaM
Jan 18, 2017 65
66. Summary
Signaling molecules and their receptors;
-Modes of cell-cell signaling (endocrine, paracrine, and autocrine)
-Steroid hormones and steroid receptor superfamily
-Nitric oxide and carbon oxide (paracrine signaling molecules
important in the nervous system.)
-Neurotransmitters (hydrophilic, carry signals between neurons or neuron
and other cell type, often bind to ion channels)
-Peptide hormones and growth factors (widest variety of signaling
molecules)
-Eicosanoids (paracrine and autocrine; aspirin inhibits their function)
Jan 18, 2017 66