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Signal transduction
The document provides an overview of signal transduction, describing it as the process where extracellular signaling molecules activate membrane receptors, leading to intracellular responses. It covers fundamental elements including ligands, receptor types, and various signaling pathways such as G-protein coupled receptors and second messengers like calcium ions and nitric oxide. The significance of signal transduction in cellular communication, disease implications, and potential applications in synthetic drug development and artificial tissue is also highlighted.
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Signal transduction
- 1. •By •KAUSHAL KUMAR SAHU •AssistantProfessor (Ad Hoc) •Department of Biotechnology •Govt. Digvijay Autonomous P. G. College •Raj-Nandgaon ( C. G. ) •
- 2. SYNOPSIS • GENERALIDEAOF SIGNALTRANSDUCTION •DEFINATION • WHAT DOESTHETERM SIGNALTRANSDUCTIONMEANS • HISTORY • BASICELEMENTSIN SIGNALTRANSDUCTION • TYPESOF SIGNALTRANSDUCTION • SIGNALLINGMOLECULE • RECEPTORMOLECULE • MODESOF CELLCELLSIGNALING • SECONDMESSENGER • SIGNALTRANSDUCTIONPATHWAY • SOME SIGNALINGPATHWAYS • SIGNIFICANCE • CONCLUSION • REFERENCE
- 3. “ It isthe process by which an extra cellular signaling molecule activates a membrane receptor, which in turn alters intercellular molecules creating a response.” The stimulus received at the cell surface is entirely different from the signal released to the cell interior, the signal received is amplified.
- 4. . • In 1970Martin Rod bell Firstly examined Signal Transduction, through effect of glucagons on a rat’s liver cell. glucagons + bind Guano sine triphosphate disassociated glucagons ↓ stimulates G- protein ↓ strongly influences the cell metabolism
- 5. BASIC ELEMENTS INSIGNAL TRANSDUCTION • Ligands:- also known as signals or first messenger. • Receptor:- transmembrane protein that binds to the ligand • Second messenger
- 6. SIGNALING MOLECULES • Thereare two kinds of signaling molecules. 1. Some signaling molecules cross the plasma membrane and bind to the receptors on the target cell.eg. Steroid hormones. 2. Another signaling molecules can’t enter the plasma membrane and thus binds to the receptors on the plasma membrane. e.g..Gprotein E.g. of signaling molecule 1. STEROID HORMONE 2. NITRIC OXIDE 3. CARBON MONOXIDE 4. NEUROTRANSMITTER 5. PEPTIDE HORMONE
- 7. RECEPTOR MOLECULE RECEPTORS CELL SURFACE RECEPTOR INTRACELLULAR RECEPTOR G-PROTEIN COUPLEDRECEPTOR ENZYME LINKED RECEPTOR ION CHANNEL LINKED RECEPTOR NUCLEAR RECEPTOR STEROID RECEPTOR ESTROGEN RECEPTOR KETOSTEROID RECEPTOR
- 8. G-PROTEIN LINKED RECEPTOR •This protein was discovered and characterized by Red bell and his colleagues at the National Institute of health in the early 1970’s. • G-protein coupled receptors are a family of integral membrane proteins • It is also known as seven transmembrane domain receptors as it possess seven membrane spanning domains. • It is linked to a guanine nucleotide binding protein. • Two pathways involve G- protein coupled receptor: • cAMP pathway • Phosphatidylinositol pathway • The G-protein linked receptors are coupled to their target enzymes in the plasma membrane through trimeric GTP binding proteins, called G proteins
- 9. • G protein undergoe s change • GProtein binds to receptor •GTP replaces GDP • Disassoc iation of G protein • ßϒ +ἀ +GTP • ἀ gives the msg to target • GTP hydrolysi s • G protein linked receptor • Ligand binds to receptor • GProtein original form
- 10. ION LINKED CHANNELRECEPTORS • Hydrophobic molecules- Rapidly diffuse • Uncharged small polar molecules- Rapidly diffuse • Uncharged large polar molecules- moves through pores using carrier protein • Charged molecules-ion channels or active transport E.g.
- 11. NUCLEAR RECEPTOR • STEROIDRECEPTOR • It is located primarily within the cytosol • In the absence of ligands they are associated with chaperons. steroid hormone ↓ chaperone activates the receptor ↓ protein folds ↓ signal enters into the nucleus
- 12. SECOND MESSENGER • Linkbetween first messenger and target cell. • They are generated when first messenger binds to the receptor. • They are water soluble and relatively smaller in size. • E.g. Calcium ion, Nitric oxide CALCIUM ION AS SECOND MESSENGER • It is present in limited amount inside the cell. • Present in endoplasmic reticulum in muscles and nervous tissue • It is inactive when present in its original site. • It is active when released in the cytosol.
- 13. ACTIVATION OF Ca2+ Calcium(Inactive state) ↓ First messenger comes and binds to receptor ↓ This interaction induces a conformational change in proteins ↓ Protein specific to calcium channels open the channels for Ca ↓ Calcium ions exit from intracellular storage sites into the cytoplasm ↓ Calcium (active state) ↓ Carries message to the target site ↓ Triggers target site for response FUNCTION: Muscle contraction, vision in retina cells,proliferation of cells
- 14. • NITRIC OXIDEAS SECOND MESSENGER It acts as a second messenger in many processes such as • Relaxation of blood vessels • Regulation of neurotransmitters • Cellular immune response • Production and maintenance of penile erections • Activation of apoptosis • It also plays an important role in generation of cGMP In high concentration NO is Toxic, It may result in stroke
- 15. MODES OF CELLSIGNALING • Cell Signaling • Endocrine signaling • Paracrine signaling • Autocrine signaling
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- 19. SIGNAL TRANSDUCTION PATHWAY • Itconsists of five many steps: • RECEPTION • TRANSDUCTION • AMPLIFICATION • INDUCTION • RESPONSE
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- 21. SOME EXAMPLES OFPATHWAY SIGNALING • cAMP pathway- It contains five main characteristics: • Stimulative hormone receptor (Rs) Inhibitory hormone receptor (Ri) • Stimulative regulative G-protein (Gs)- binds with Stimulative receptor Inhibitory regulative G-protein (Gi) - binds with Inhibitory receptor • Adenylyl cyclase- 12- transmembrane glucoprotein that catalyses ATP to form cAMP with the help of Ca. • Protein kinase A • cAMP phosphodiesterase
- 23. RAS MEDIATED SIGNALTRANSDUCTION PATHWI It contains four main characteristics: •Receptor Tyrosine Kinase •Growth factor •Ras proteins •MAP- kinase •They are products of proto oncogenes c-ras. •They are active only when bound to GTP and inactive when bounded with GDP. •Two classes of signalling proteins that regulate Ras activity include the following: •GTPase activating proteins (GAPs) - it increases the rate of hydrolysis of bound GTP by Ras resulting in inactivated Ras. •Guanine nucleotide releasing proteins (GNRPs) - it promotes the release of GDP and uptake of GTP resulting in activated Ras. •Thus Tyrosine kinase activates Ras proteins either by inhibiting GAP or activating •GNRP •Ras proteins when active initiate a cascade of phosphorylation which leads to MAP- kinase (mitogen activated protein) which finally relays signals to nucleus.
- 25. • Every singleway our body reacts depend on the way our receptors catches signals and transducts them to the target cells. • Our life susceptibility depends on signal transduction • Errors in cellular information processing are responsible for many diseases such as cancer, heart problems etc. • Full study of signal transduction helps in creating synthetic drugs, • And also artificial tissue.
- 26. CONCLUSION • Cell signallingis a most important function in all animals and plant cells • Numbers of research being carried out indicate that all organisms share certain basic signalling mechanism but certain pathways are unique to each major kingdom. • The scientist world has recognize the significance of signal transduction mainly in drug production but still many of its areas are left to be explored.
- 27. REFERENCE • THE CELL-A Molecular Approach- By M.Cooper & Geoffery (2006) • Text Book of cell Biology- By Karp (2007) • Cell And Molecular Biology- By P.K.Gupta (2008) • Gene viii- By Lewin & Benjamin(2006) • Genetics- By B.D. Singh