This is a brief overview of the Types of Mutation. I have compiled all the salient features of the Mutation and shared in this presentation, hope you guys like it.
Transcription is the process of synthesizing RNA from a DNA template. In prokaryotes, a single RNA polymerase synthesizes all RNA, while eukaryotes have multiple RNA polymerases. The enzyme binds to promoter regions on DNA and uses one strand as a template to make complementary RNA. Primary transcripts in eukaryotes undergo processing like capping, polyadenylation, and splicing to produce mature, functional RNAs that can be translated or act as non-coding RNAs. Transcription involves initiation, elongation, and termination and can be inhibited by various antibiotics that target bacterial or eukaryotic RNA polymerases.
Protein targeting or protein sorting is the biological mechanism by which proteins are transported to their appropriate destinations in the cell or outside it. Proteins can be targeted to the inner space of an organelle, different intracellular membranes, plasma membrane, or to exterior of the cell via secretion.
The document discusses the process of translation, where mRNA is used to synthesize proteins from amino acids. Translation occurs through three main stages - initiation, elongation, and termination - and involves various tools like amino acids, mRNA, tRNAs, ribosomes, and other factors. While similar between prokaryotes and eukaryotes, translation differs in some initiation and elongation factors used, and eukaryotic mRNA contains a 5' cap and 3' poly-A tail.
Apoptosis is a programmed cell death process that occurs normally during development and aging and as a defense mechanism. There are two main pathways of apoptosis - the intrinsic mitochondrial pathway initiated from within the cell, and the extrinsic death receptor pathway initiated from outside the cell. Both pathways involve caspase proteins that activate a caspase cascade leading to characteristic cell changes and death. Apoptosis must be tightly regulated as both insufficient and excessive apoptosis can lead to disorders.
- Transcription in eukaryotes is carried out by three RNA polymerases (RNAP I, II, III) that synthesize different RNA molecules and require transcription factors.
- RNAP II transcribes protein-coding genes and initiation requires promoter elements like TATA boxes located upstream of genes.
- Introns, or intervening sequences, are found within most eukaryotic genes and can exceed exon sequences in length. Introns are excised through different splicing mechanisms for mRNA, tRNA, and rRNA.
- Splicing of mRNA introns involves a spliceosome complex containing small nuclear RNAs that catalyzes two transesterification reactions joining exons.
lac operon is a negatively controlled inducible operon.E.coli can use lactose as a source of carbon.
The enzymes required for the use of lactose as a source of carbon are synthesised only when the lactose is available as carbon source.
The lac operon is an example of nagatively controlled inducible operon.
Structure
The lac operon consists of 5 structural units.
Promoter
Operator
Structural genes
CAP binding sites
Regulatory gene
This is a brief overview of the Types of Mutation. I have compiled all the salient features of the Mutation and shared in this presentation, hope you guys like it.
Transcription is the process of synthesizing RNA from a DNA template. In prokaryotes, a single RNA polymerase synthesizes all RNA, while eukaryotes have multiple RNA polymerases. The enzyme binds to promoter regions on DNA and uses one strand as a template to make complementary RNA. Primary transcripts in eukaryotes undergo processing like capping, polyadenylation, and splicing to produce mature, functional RNAs that can be translated or act as non-coding RNAs. Transcription involves initiation, elongation, and termination and can be inhibited by various antibiotics that target bacterial or eukaryotic RNA polymerases.
Protein targeting or protein sorting is the biological mechanism by which proteins are transported to their appropriate destinations in the cell or outside it. Proteins can be targeted to the inner space of an organelle, different intracellular membranes, plasma membrane, or to exterior of the cell via secretion.
The document discusses the process of translation, where mRNA is used to synthesize proteins from amino acids. Translation occurs through three main stages - initiation, elongation, and termination - and involves various tools like amino acids, mRNA, tRNAs, ribosomes, and other factors. While similar between prokaryotes and eukaryotes, translation differs in some initiation and elongation factors used, and eukaryotic mRNA contains a 5' cap and 3' poly-A tail.
Apoptosis is a programmed cell death process that occurs normally during development and aging and as a defense mechanism. There are two main pathways of apoptosis - the intrinsic mitochondrial pathway initiated from within the cell, and the extrinsic death receptor pathway initiated from outside the cell. Both pathways involve caspase proteins that activate a caspase cascade leading to characteristic cell changes and death. Apoptosis must be tightly regulated as both insufficient and excessive apoptosis can lead to disorders.
- Transcription in eukaryotes is carried out by three RNA polymerases (RNAP I, II, III) that synthesize different RNA molecules and require transcription factors.
- RNAP II transcribes protein-coding genes and initiation requires promoter elements like TATA boxes located upstream of genes.
- Introns, or intervening sequences, are found within most eukaryotic genes and can exceed exon sequences in length. Introns are excised through different splicing mechanisms for mRNA, tRNA, and rRNA.
- Splicing of mRNA introns involves a spliceosome complex containing small nuclear RNAs that catalyzes two transesterification reactions joining exons.
lac operon is a negatively controlled inducible operon.E.coli can use lactose as a source of carbon.
The enzymes required for the use of lactose as a source of carbon are synthesised only when the lactose is available as carbon source.
The lac operon is an example of nagatively controlled inducible operon.
Structure
The lac operon consists of 5 structural units.
Promoter
Operator
Structural genes
CAP binding sites
Regulatory gene
Translation is the process by which the genetic code carried by mRNA is used to synthesize proteins. It involves three main steps - initiation, elongation, and termination. During initiation, the small and large ribosomal subunits assemble around the mRNA along with initiator tRNA and other factors. In elongation, tRNAs bring amino acids to the ribosome according to the mRNA codons, and peptide bonds form between them. Termination occurs when a stop codon enters the A site and causes the release of the completed protein chain.
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.
Post-transcriptional modifications are important processes that convert primary transcript RNA into mature RNA. These modifications include 5' capping, 3' polyadenylation, and splicing of introns in eukaryotes. The modifications help make RNA molecules recognizable for translation and increase protein synthesis efficiency by removing non-coding regions. Different types of RNA undergo specific processing pathways involving nucleases, snoRNAs and other protein complexes.
This document discusses DNA recombination, which is the process by which two DNA molecules exchange genetic information. There are two main types of recombination: homologous recombination, which occurs between similar or identical DNA sequences, and non-homologous recombination, which does not require sequence similarity. Homologous recombination is important for DNA repair and genetic diversity through generating new combinations of genes during meiosis. It is extensively studied in E. coli and involves many proteins like RecBCD and RecA. The Holliday model is commonly used to explain homologous recombination through the formation of Holliday junctions. Site-specific and gene conversion are other types of homologous recombination, while transposition involves non-hom
Homologous recombination (HR) is the exchange of genetic material between two similar or identical molecules of DNA. The document outlines the mechanism and molecular basis of HR, including key steps like double-strand break formation, strand invasion, and Holliday junction resolution. HR serves important biological roles like DNA repair and genetic diversity. It has practical applications in gene mapping, transgenics, and gene editing technologies. Precise genome editing using HR is becoming an alternative to traditional plant breeding for crop improvement.
SOS repair
a system that repairs severely damaged bases in DNA by base excision and replacement, even if there is no template to guide base selection. This process is a last resort for repair and is often the cause of mutations.
1. Transcription is the process by which DNA is copied into messenger RNA (mRNA) by RNA polymerase. This involves three phases - initiation, elongation, and termination.
2. Eukaryotic transcription is more complex than prokaryotic transcription due to multiple RNA polymerases, nucleosomes, separation of transcription and translation, and intron-exon structure of genes.
3. Following transcription, eukaryotic mRNA undergoes processing including capping, polyadenylation, and splicing before being translated into protein by ribosomes.
The document discusses gene regulation in prokaryotes. It explains that gene expression can be constitutive, inducible, or repressible. In prokaryotes, regulatory mechanisms allow genes to be expressed only when their products are needed. Inducible genes encode enzymes for catabolic pathways and are expressed in the presence of substrates. Repressible genes encode enzymes for anabolic pathways and are turned off in the presence of end products. Gene expression is mainly regulated at the transcriptional level through positive and negative control mechanisms involving activators and repressors.
This document discusses genetic mutations and DNA repair. It defines mutations as heritable changes in genetic material that can provide genetic variation and be the basis for evolution. Mutations can be caused spontaneously during DNA replication or cell division, or can be induced by environmental mutagens. The majority of mutations are neutral or harmful, with a small percentage being beneficial. Different types of mutations are described, including point mutations, insertions, deletions, and trinucleotide repeats. The effects of mutations on genes and proteins are explained. The timing of mutations as either germline or somatic is an important factor. Causes of spontaneous mutations like depurination and deamination are outlined.
The nuclear membrane, also known as the nuclear envelope, is a double lipid bilayer that surrounds the genetic material and nucleolus in eukaryotic cells. It consists of an inner and outer nuclear membrane, with the space between called the perinuclear space. The nuclear membrane functions to compartmentalize the nuclear material, maintain the shape and stability of the nucleus, regulate the transport of substances into and out of the nucleus through nuclear pores, and facilitate communication between the nucleus and the cell.
This presentation on "Cell Cycle regulation" takes you to the cell cycle describing the stages and checkpoints involved providing some of the evidences of cell cycle regulation. Then we will move to cyclins and cyclin dependent kinases and the mechanism they follow.
This journey in regulation of cell cycle will take a halt after a general discussion of positive and negative cell cycle regulators.
Thankyou.
This presentation discusses the genetic code and how it translates DNA and RNA sequences into proteins. The genetic code is universal across all living organisms and consists of 64 codons composed of 3 nucleotides that correspond to 20 amino acids. Codons are classified as sense codons, which code for amino acids, or signal codons like initiation and termination codons. Anticodons on tRNAs pair with mRNA codons to recognize and translate the codons. The genetic code is non-overlapping, degenerate, and Francis Crick's wobble hypothesis explains the pattern of degeneracy by proposing the third position in the anticodon is not as specific.
The MAP kinase pathway involves signal transduction from activated RAS protein to MAP kinase. The activated RAS starts a kinase cascade involving RAF, MEK and MAPK. MAP kinase then translocates to the nucleus and activates transcription factors like C-Fos. This leads to expression of genes involved in cell cycle progression. The JAK-STAT pathway involves phosphorylation of STAT proteins by JAK kinases upon cytokine binding. Phosphorylated STATs form dimers, enter the nucleus and regulate gene transcription. Both pathways integrate with other signaling cascades and are regulated by phosphatases and inhibitory proteins.
This document discusses genetic mutations. It begins by defining genes and DNA, then describes the different types of genetic mutations including point mutations, frameshift mutations, deletions and repeats. It discusses the causes of mutations including spontaneous errors and environmental factors. The document outlines several diseases caused by mutations and describes diagnostic tests and potential treatments, noting that currently there is no cure for genetic disorders. It concludes by emphasizing the importance of genetic mutations as a cause of disease.
Gene expression in eukaryotes is regulated through multiple mechanisms at the transcriptional and post-transcriptional levels. These mechanisms allow for adaptation, tissue specificity, and development. Regulation occurs through chromatin remodeling, enhancers/repressors, locus control regions, gene amplification, rearrangement, and alternative RNA processing. Key differences between prokaryotic and eukaryotic gene expression include larger eukaryotic genomes, different cell types, lack of operons, chromatin structure, and uncoupled transcription/translation.
One of the first plausible models to account for the preceding observations was
formulated by Robin Holliday.
The key features of the Holliday model are the formation of heteroduplex DNA; the
creation of a cross bridge; its migration along the two heteroduplex strands,
termed branch migration; the occurrence of mismatch repair; and the
subsequent resolution, or splicing, of the intermediate structure to yield different
typesof recombinant molecules.
Translation inhibitors work in prokaryotes and eukaryotes by targeting different sites on the ribosome to inhibit protein synthesis. In prokaryotes, tetracycline and diphtheria toxin inhibit the A site on the small ribosomal subunit, while erythromycin inhibits the peptide exit groove on the large subunit. Chloramphenicol and cycloheximide inhibit peptidyl transferase activity, and puromycin, hygromycin B, and fusidic acid inhibit at the A site or through elongation factor interactions to inhibit translation.
Introduction
Definition
History
Evolution and origin of apoptosis
Significance
Purpose of apoptosis
Steps /process
Morphological and biochemical changes
Mechanism of apoptosis
Caspases
Regulation of apoptosis
Disorders of apoptosis
Application
Conclusion
Referances
The document discusses the plasmid vector pBR322, which was constructed in 1977 and is one of the most commonly used cloning vectors. It describes the origins and components of pBR322, including two antibiotic resistance genes, the origin of replication, and restriction enzyme cleavage sites. The document also summarizes the construction of several derivatives of pBR322, including pBR327, pUC18, and pBR118/119, and notes their applications and advantages over the original pBR322 vector.
Translation is the process by which the genetic code carried by mRNA is used to synthesize proteins. It involves three main steps - initiation, elongation, and termination. During initiation, the small and large ribosomal subunits assemble around the mRNA along with initiator tRNA and other factors. In elongation, tRNAs bring amino acids to the ribosome according to the mRNA codons, and peptide bonds form between them. Termination occurs when a stop codon enters the A site and causes the release of the completed protein chain.
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.
Post-transcriptional modifications are important processes that convert primary transcript RNA into mature RNA. These modifications include 5' capping, 3' polyadenylation, and splicing of introns in eukaryotes. The modifications help make RNA molecules recognizable for translation and increase protein synthesis efficiency by removing non-coding regions. Different types of RNA undergo specific processing pathways involving nucleases, snoRNAs and other protein complexes.
This document discusses DNA recombination, which is the process by which two DNA molecules exchange genetic information. There are two main types of recombination: homologous recombination, which occurs between similar or identical DNA sequences, and non-homologous recombination, which does not require sequence similarity. Homologous recombination is important for DNA repair and genetic diversity through generating new combinations of genes during meiosis. It is extensively studied in E. coli and involves many proteins like RecBCD and RecA. The Holliday model is commonly used to explain homologous recombination through the formation of Holliday junctions. Site-specific and gene conversion are other types of homologous recombination, while transposition involves non-hom
Homologous recombination (HR) is the exchange of genetic material between two similar or identical molecules of DNA. The document outlines the mechanism and molecular basis of HR, including key steps like double-strand break formation, strand invasion, and Holliday junction resolution. HR serves important biological roles like DNA repair and genetic diversity. It has practical applications in gene mapping, transgenics, and gene editing technologies. Precise genome editing using HR is becoming an alternative to traditional plant breeding for crop improvement.
SOS repair
a system that repairs severely damaged bases in DNA by base excision and replacement, even if there is no template to guide base selection. This process is a last resort for repair and is often the cause of mutations.
1. Transcription is the process by which DNA is copied into messenger RNA (mRNA) by RNA polymerase. This involves three phases - initiation, elongation, and termination.
2. Eukaryotic transcription is more complex than prokaryotic transcription due to multiple RNA polymerases, nucleosomes, separation of transcription and translation, and intron-exon structure of genes.
3. Following transcription, eukaryotic mRNA undergoes processing including capping, polyadenylation, and splicing before being translated into protein by ribosomes.
The document discusses gene regulation in prokaryotes. It explains that gene expression can be constitutive, inducible, or repressible. In prokaryotes, regulatory mechanisms allow genes to be expressed only when their products are needed. Inducible genes encode enzymes for catabolic pathways and are expressed in the presence of substrates. Repressible genes encode enzymes for anabolic pathways and are turned off in the presence of end products. Gene expression is mainly regulated at the transcriptional level through positive and negative control mechanisms involving activators and repressors.
This document discusses genetic mutations and DNA repair. It defines mutations as heritable changes in genetic material that can provide genetic variation and be the basis for evolution. Mutations can be caused spontaneously during DNA replication or cell division, or can be induced by environmental mutagens. The majority of mutations are neutral or harmful, with a small percentage being beneficial. Different types of mutations are described, including point mutations, insertions, deletions, and trinucleotide repeats. The effects of mutations on genes and proteins are explained. The timing of mutations as either germline or somatic is an important factor. Causes of spontaneous mutations like depurination and deamination are outlined.
The nuclear membrane, also known as the nuclear envelope, is a double lipid bilayer that surrounds the genetic material and nucleolus in eukaryotic cells. It consists of an inner and outer nuclear membrane, with the space between called the perinuclear space. The nuclear membrane functions to compartmentalize the nuclear material, maintain the shape and stability of the nucleus, regulate the transport of substances into and out of the nucleus through nuclear pores, and facilitate communication between the nucleus and the cell.
This presentation on "Cell Cycle regulation" takes you to the cell cycle describing the stages and checkpoints involved providing some of the evidences of cell cycle regulation. Then we will move to cyclins and cyclin dependent kinases and the mechanism they follow.
This journey in regulation of cell cycle will take a halt after a general discussion of positive and negative cell cycle regulators.
Thankyou.
This presentation discusses the genetic code and how it translates DNA and RNA sequences into proteins. The genetic code is universal across all living organisms and consists of 64 codons composed of 3 nucleotides that correspond to 20 amino acids. Codons are classified as sense codons, which code for amino acids, or signal codons like initiation and termination codons. Anticodons on tRNAs pair with mRNA codons to recognize and translate the codons. The genetic code is non-overlapping, degenerate, and Francis Crick's wobble hypothesis explains the pattern of degeneracy by proposing the third position in the anticodon is not as specific.
The MAP kinase pathway involves signal transduction from activated RAS protein to MAP kinase. The activated RAS starts a kinase cascade involving RAF, MEK and MAPK. MAP kinase then translocates to the nucleus and activates transcription factors like C-Fos. This leads to expression of genes involved in cell cycle progression. The JAK-STAT pathway involves phosphorylation of STAT proteins by JAK kinases upon cytokine binding. Phosphorylated STATs form dimers, enter the nucleus and regulate gene transcription. Both pathways integrate with other signaling cascades and are regulated by phosphatases and inhibitory proteins.
This document discusses genetic mutations. It begins by defining genes and DNA, then describes the different types of genetic mutations including point mutations, frameshift mutations, deletions and repeats. It discusses the causes of mutations including spontaneous errors and environmental factors. The document outlines several diseases caused by mutations and describes diagnostic tests and potential treatments, noting that currently there is no cure for genetic disorders. It concludes by emphasizing the importance of genetic mutations as a cause of disease.
Gene expression in eukaryotes is regulated through multiple mechanisms at the transcriptional and post-transcriptional levels. These mechanisms allow for adaptation, tissue specificity, and development. Regulation occurs through chromatin remodeling, enhancers/repressors, locus control regions, gene amplification, rearrangement, and alternative RNA processing. Key differences between prokaryotic and eukaryotic gene expression include larger eukaryotic genomes, different cell types, lack of operons, chromatin structure, and uncoupled transcription/translation.
One of the first plausible models to account for the preceding observations was
formulated by Robin Holliday.
The key features of the Holliday model are the formation of heteroduplex DNA; the
creation of a cross bridge; its migration along the two heteroduplex strands,
termed branch migration; the occurrence of mismatch repair; and the
subsequent resolution, or splicing, of the intermediate structure to yield different
typesof recombinant molecules.
Translation inhibitors work in prokaryotes and eukaryotes by targeting different sites on the ribosome to inhibit protein synthesis. In prokaryotes, tetracycline and diphtheria toxin inhibit the A site on the small ribosomal subunit, while erythromycin inhibits the peptide exit groove on the large subunit. Chloramphenicol and cycloheximide inhibit peptidyl transferase activity, and puromycin, hygromycin B, and fusidic acid inhibit at the A site or through elongation factor interactions to inhibit translation.
Introduction
Definition
History
Evolution and origin of apoptosis
Significance
Purpose of apoptosis
Steps /process
Morphological and biochemical changes
Mechanism of apoptosis
Caspases
Regulation of apoptosis
Disorders of apoptosis
Application
Conclusion
Referances
The document discusses the plasmid vector pBR322, which was constructed in 1977 and is one of the most commonly used cloning vectors. It describes the origins and components of pBR322, including two antibiotic resistance genes, the origin of replication, and restriction enzyme cleavage sites. The document also summarizes the construction of several derivatives of pBR322, including pBR327, pUC18, and pBR118/119, and notes their applications and advantages over the original pBR322 vector.
El documento resume los mecanismos de citotoxicidad mediados por gránulos en células T citotóxicas y células NK. Estos incluyen la liberación de perforinas y granzimas que inducen apoptosis caspasa-dependiente e independiente, así como daño a la membrana mediado por granulisina. Se describe específicamente que la granzima M induce una forma única de muerte celular perforina-dependiente que causa daño mitocondrial sin fragmentación del ADN.
This document provides an overview of shock, including its pathophysiology and classification. It discusses the main types of shock: hypovolemic, cardiogenic, distributive, and obstructive. For each type, it describes the causes, characteristics, and treatment approaches. It also covers fluid resuscitation, vasopressors, inotropic drugs, and mechanical ventilation as general treatment strategies for shock.
Shock is a severe pathophysiological insult associated with mitochondrial and cellular energetic failure due to reduced oxygen and nutrient delivery or ineffective utilization. It can occur with or without hypotension. The main types of shock are hypovolemic, cardiogenic, obstructive, distributive, septic, neurogenic, anaphylactic, and endocrine shock. Organ system consequences include effects on the CNS, CVS, respiratory system, kidneys, GI tract, liver, hematological system, and immune system. Pulmonary embolism can cause shock by increasing pulmonary vascular resistance and right ventricular afterload, potentially leading to right heart failure.
Shock - Pathophysiology, Clinical Features & ManagementAnkit Sharma
1. Hemorrhagic shock is the most common cause of shock in surgical or trauma patients and results from blood loss that exceeds 15% of circulating volume.
2. Initial management of hemorrhagic shock involves identifying the source of bleeding, providing immediate resuscitation with fluids and blood products, and controlling hemorrhage.
3. Damage control resuscitation principles are followed, including permissive hypotension to limit blood loss and balanced use of crystalloids, colloids, platelets, and plasma to prevent coagulopathy.
1. Shock is defined as inadequate tissue perfusion resulting from decreased delivery of oxygen and nutrients and inadequate removal of waste from cells.
2. There are four main types of shock: hypovolemic, distributive, cardiogenic, and obstructive.
3. Hypovolemic shock results from loss of intravascular volume from bleeding, vomiting, or diarrhea leading to decreased blood pressure and organ perfusion. Compensatory mechanisms aim to maintain perfusion to vital organs but eventually fail.
Shock is defined as inadequate tissue perfusion due to reduced cardiac output, which can lead to organ dysfunction and high mortality if not treated early. Tissue perfusion depends on mean arterial pressure and cardiac output. There are four categories of shock depending on the cause of reduced cardiac output: hypovolemic, cardiogenic, distributive, and obstructive. Early intervention is needed to support physiological compensatory mechanisms and reverse the causes of shock through measures like fluid resuscitation and vasopressor drugs in order to prevent progression to refractory shock.
This seminar covers different types of shock including definitions, pathophysiology, clinical features, investigations, and treatment. The main types discussed are hypovolaemic shock, traumatic shock, cardiogenic shock, neurogenic shock, septic shock, and crush syndrome. Hypovolaemic shock is the most common and results from sudden loss of blood or fluid volume. Treatment focuses on fluid resuscitation and controlling bleeding. Septic shock has a high mortality and is usually caused by gram-negative bacteria. Crush syndrome occurs after body portions are compressed by heavy weights.
La inmunología estudia la inmunidad y la respuesta inmunitaria del organismo. El sistema inmune está formado por células y moléculas que actúan de forma innata u inespecífica para combatir agentes extraños de manera inmediata, y de forma adaptativa u específica mediante respuestas dirigidas contra patógenos particulares. Células como los macrófagos y las células dendríticas fagocitan patógenos y activan la respuesta adaptativa al presentar antígenos a los linfocitos.
1. Shock is a life-threatening condition defined as inadequate delivery of oxygen and nutrients to tissues due to acute circulatory failure, leading to cellular injury and death if untreated.
2. The document classifies and describes the pathophysiology and stages of different types of shock, including hypovolemic, cardiogenic, septic, and neurogenic shock.
3. Left untreated, the stages of shock progress from initial compensated shock to decompensated shock and finally irreversible shock, with multi-organ failure potentially leading to death.
This document discusses the diagnosis and management of shock. It defines shock as impaired tissue oxygenation and perfusion that can lead to organ dysfunction and death if left untreated. The document classifies shock into 4 main categories: hypovolemic, cardiogenic, distributive, and obstructive. It then describes the key clinical features, causes, and goals of treatment for each type of shock. The general principles of shock management are also summarized, which include treating the underlying cause, restoring adequate perfusion and tissue oxygen delivery, and reducing oxygen demand through supportive care.
El documento describe los diferentes tipos de shock, incluyendo su definición, clasificación, patrones hemodinámicos, fisiopatología y tratamiento. Describe los shocks hipovolémico, cardiogénico, obstructivo, distributivo, séptico y anafiláctico. Explica que todos los tipos de shock conducen a hipoperfusión tisular y disfunción multiorgánica si no se tratan adecuadamente.
Shock is a condition where the cardiovascular system fails to adequately perfuse tissues. It can be caused by an impaired pump (cardiogenic shock), reduced circulating volume (hypovolemic shock), or maldistribution of blood flow (distributive shock). The main effects are cellular hypoxia, impaired metabolism, and organ damage or failure if not treated. Compensatory mechanisms aim to increase perfusion but eventually fail, leading to irreversible cellular damage and death if shock persists.
1. VIE BIOMOLECOLARI
DELL’APOPTOSI
Le Heat Shock Proteins
Acquisizioni di biologia molecolare ed
eventuali applicazioni in
terapia medica.
26 Settembre 2005
Patologia Clinica
Dott. Stefano Mancini
2. Le fasi dell’apoptosi
I.
INDUZIONE
Include diversi meccanismi:
-recettori di superficie
-via mitocondriale;
-altre vie (es. ER).
II. PREPARAZIONE
Comprende l’attivazione di iniziatori del processo quali le
caspasi iniziatrici ed altre chinasi/fosfatasi.
III. ESECUZIONE
Detta anche “fase di morte”, coinvolge prevalentemente le
caspasi effetrici.
4. Esistono diverse vie per
l’apoptosi
Apoptosi caspasi-dipendente
Apoptosi caspasi-indipendente
Anoikisi
Le HSP possono intervenire in tutte queste
vie ostacolando o facilitando l’apoptosi.
5.
6. Diagram showing the role of
heat-shock proteins and a
chaperonin
in protein folding. As the
ribosome moves along the
molecule of
messenger RNA, a chain of
amino acids is built up to form
a new
protein molecule. The chain is
protected against unwanted
interactions
with other cytoplasmic
molecules by heat-shock
proteins and a
chaperonin molecule until it
has successfully completed its
folding.
7. Classi di HSP nei mammiferi
5 maggiori famiglie di
HSP coinvolte nella
risposta a stress
cellulari:
-HSP 27
-HSP 60
-HSP 70
-HSP 90
-HSP 104
8. Regolazione
La sintesi è finemente regolata a livello
trascrizionale da Heat Shock Factors (HSF).
HSF 1 fa parte dei principali regolatori.
9. HSF-1
In forma monomerica nelle cellule quiescenti, è
legato da HSP-90 e -70.
Sotto stress le HSP si separano da HSF-1 il
quale migra nel nucleo come trimero.
Si lega così al DNA nella sequenza consenso in
modo da avviare la sintesi di HSP.
12. Apoptosi caspasi-dipendente
Membrana citoplasmatica
L’espressione di HSP-70 inibisce l’apoptosi Fasmediata.
Tuttavia l’iperespressione di HSP-70 non protegge
le cellule Jurkat dall’apoptosi.
13.
14. Apoptosi caspasi-dipendente
Membrana citoplasmatica
L’inibizione di HSP-90 attraverso oligonucleotidi
antisenso favorisce l’apoptosi in cellule di
neuroblastoma sottoposte a stress termico. Ciò
favorisce inoltre l’attivazione del death domain,
facilitando così la morte cellulare programmata.
15. Apoptosi caspasi-dipendente
Membrana citoplasmatica
Diverse HSP (es. HSP-70) migrano sulla superficie
cellulare quando il processo apoptotico è già
avviato. Questo rende le cellule più facilmente
riconoscibili dai fagociti.
16. Apoptosi caspasi-dipendente
Citosol
Le HSP di basso PM (es. HSP-27) sono fosforilate
in vivo dalla MAPKAP chinasi-2, la quale è a sua
volta attivata da una fosforilazione mediata dalla
p38 chinasi.
HSP-27 fosforilata è capace di interagire con
Daxx, una proteina contenente un death domain.
Il legame con Daxx previene l’attivazione di Ask-1,
una serina/treonina chinasi capace di indurre
apoptosi attraverso la via mediata da Fas.
17. Apoptosi caspasi-dipendente
Citosol
HSP-72 è un inibitore diretto di Ask-1, favorendo la
sopravvivenza della cellula in seguito a stress
ossidativo.
L’espressione di HSP-72 induce inoltre inibizione
di JNK (c-Jun N-terminal kinase, famiglia delle
protein-chinasi indotte da stress).
18.
19. Apoptosi caspasi-dipendente
Citosol
HSP-105a è capace di legare JNK, provocando
inibizione della apoptosi in linee cellulari PC12
sottoposte a diversi stressor ambientali.
Tuttavia, l’espressione di HSP-105a favorisce
l’apoptosi mediata da danno ossidativo in cellule di
embrione di topo.
20. Apoptosi caspasi-dipendente
Citosol
HSP-90 è capace di modulare Raf1.
Se Raf1 è legato a HSP-90 è incapace di avviare
l’apoptosi.
Viceversa, la dissociazione del complesso
HSP90/Raf1 avvia la morte cellulare programmata
in mastociti e in linfociti-B.
21. Apoptosi caspasi-dipendente
Nucleo
Le HSP giocano un ruolo fondamentale nel
prevenire l’apoptosi prodotta da lesioni nucleari.
HSP-27 e -70 migrano nel nucleo a seguito di
stress ossidativo.
HSP-72 compare nel nucleo di cellule alveolari
umane L-132 a seguito di danni al DNA prodotti da
acido dimetilarsenico.
22. Apoptosi caspasi-dipendente
Nucleo
HSP-90 interagisce direttamente con la telomerasi
stimolandone l’attività. Si è visto che HSP-90 può
facilitare la sopravvivenza cellulare nel carcinoma
della prostata.
23. Apoptosi caspasi-dipendente
Mitocondri
Possiedono un ruolo centrale nello svolgimento
del processo apoptotico.
Molti segnali proapoptotici convergono nella
permeabilizzazione della membrana esterna.
Ciò provoca la traslocazione e multimerizzazione
della proteina Bax (B-cell lymphoma-2 protein
associated X protein) all’interno del mitocondrio.
24. Apoptosi caspasi-dipendente
Mitocondri
Bax a sua volta induce la permeabilizzazione della
membrana interna.
Altri fattori: -Smac/DIABLO (second mitocondriaderived activator of caspases), è
capace di inibire IAP;
-IAP (inhibitors of apoptosis protein),
ad es. XIAP, c-IAP1 e c-IAP2;
-HtrA2/Omi, inibisce IAP.
25.
26. Apoptosi caspasi-dipendente
Mitocondri
HSP-27 lega il citocromo-c prevenendo l’interazione
citocromo-c-mediata tra Apaf-1 e procaspasi 9,
interferendo quindi con l’apoptosi.
Studi successivi hanno dimostrato la localizzazione di
HSP-27 nel mitocondrio a trattenere il citocromo-c.
HSP-27 inibisce anche il rilascio di Smac/DIABLO ed
è in grado di legare alcuni RNA inibitori dell’apoptosi al
fine di impedirne la degragdazione.
27. Apoptosi caspasi-dipendente
Mitocondri
HSP-60 e la sua co-chaperone HSP-10 sono capaci di
legare la procaspasi-3 a livello mitocondriale.
Viceversa, HSP-60 citoplasmatica sembra sequestrare
alcuni fattori proapoptotici quali Bax o Bak.
HSP-70 sopprime l’apoptosi direttamente
associandosi ad Apaf-1 e impedendo il normale
assemblaggio dell’apoptosoma.
28. Apoptosi caspasi-dipendente
Mitocondri
Al contrario HSP-105a, un omologo di HSP-70,
favorisce l’apoptosi inducendo il rilascio del
citocromo-c, l’attivazione della caspasi-3 e la
dissociazione della PARP (poly-ADP ribose
polymerase) in cellule embrionali di topo.
HSP-90 lega direttamente Apaf-1 e previene la
formazione dell’apoptosoma.
29. Apoptosi caspasi-dipendente
Reticolo endoplasmatico (RE)
Interviene nell’apoptosi in almeno due modalità:
-in risposta a proteine alterate;
-con alterazioni della permeabilità al Ca++.
Recenti studi suggeriscono il coinvolgimento
delle proteasi del RE, come le caspasi 7 e 12.
La risposta ad alterazioni proteiche induce
inoltre il fattore di trascrizione CHOP/GADD153
il quale promuove l’apoptosi.
30. Apoptosi caspasi-dipendente
Reticolo endoplasmatico (RE)
Grp78, appartenente alle HSP-70, sembra inibire
direttamente l’apoptosi RE mediata attraverso il
legame delle caspasi 7 e 12.
Grp78 è stata anche associata all’attivazione del
fattore NF-kB e all’inibizione dei disturbi del flusso
del Ca++.
31. Apoptosi caspasi-indipendente
Prevede l’entrata in gioco di mediatori che
agiscono in parallelo all’attivazione delle
caspasi.
E’ ovvio che le vie possono talora convergere.
Sono interessati i seguenti fattori:
-granzimi;
-catepsine;
-calpaine;
-ceramide;
-AIF (apoptosis-inducing factors).
32. Apoptosi caspasi-indipendente
Granzimi
Famiglia di serin-proteasi spesso associati alle
perforine nei linfociti T attivati e nelle cellule NK.
Granzima B è fra i più rappresentati nell’uomo.
In vivo amplificano le vie apoptotiche caspasidipendenti, ma possono anche indurre l’attivazione
della proteina Bid senza coinvolgere il
reclutamento delle caspasi.
Bid produce alterazioni della membrana
mitocondriale e il rilascio del citocromo-c.
33.
34. The Granzymes are serine protease family members structurally related to
Chymotrypsin and exhibit the characteristic catalytic triad His-Asp-Ser at the
active site.76 They are key components of the lytic granule, and are
responsible for initiating many of the apoptosis-associated events that occur
in cells targeted for destruction by cytotoxic cells.
35. Apoptosi caspasi-indipendente
Granzimi
Ancora poco chiare sono le interazioni con le HSP.
HSP-70 espresso a livello di membrana interviene
nell’apoptosi di cellule tumorali attraverso il
legame e trasporto del granzima B.
36. Apoptosi caspasi-indipendente
Catepsine
Classe di enzimi proteolitici contenenti vari tipi di
proteasi: cistin-proteasi (catepsine B,C,L,H,S e O),
aspartato proteasi (catepsine D,E e F) e serinproteasi (catepsina G).
Hanno origine nei lisosomi.
La catepsina B è rilasciata dai lisosomi di epatociti
trattati con TNF-alfa o nell’apoptosi indotta da p53.
La sua attivazione viene prevenuta da NF-kB.
37. Apoptosi caspasi-indipendente
Catepsine
Relazione con le HSP ancora da approfondire.
HSP-73 e HSP-90 si accumulano in lisosomi di
cellule epiteliali tubulari di rene di topi trattati con
alte dosi di gentamicina.
38. Apoptosi caspasi-indipendente
Calpaine
Proteasi calcio-dipendenti implicate
nell’organizzazione del citoscheletro e nella
degradazione preoteica.
Esistono come eterodimeri formati da una piccola
subunità regolatrice e una delle tre grandi subunità
catalitiche: calpaina-1, -2 e -3.
Agiscono spesso in sinergia con le caspasi,
soprattutto nel neurone.
39. Apoptosi caspasi-indipendente
Calpaine
In diversi tumori (mammario e ovarico) così come
nell’apoptosi cisplatino-mediata del melanoma le
calpaine hanno un ruolo chiave.
Le calpaine attivano infatti Bid indipendentemente
dalla attivazione delle caspasi.
Grp-94 sembra inibire l’apoptosi mediata dalle
Calpaine in diverse situazioni quali stress da
ipossia/riossigenazione e apoptosi etoposidemediata.
Il cisplatino può legare Grp-94 inibendolo.
40. Apoptosi caspasi-indipendente
Ceramide
Mediatore lipidico formato da sfingosina Nacetilata capace di indurre l’apoptosi attraverso
varie strade:
-caspasi dipendenti: attivazione caspasi-9 e -3;
-catepsine dipendenti;
-calpaine dipendenti.
L’apoptosi ceramide mediata può essere inibita da
Bcl-2.
HSP-70 protegge la cellula dall’apoptosi indotta da
ceramide.
41. Ceramide leads to loss of mitochondrial transmembrane potential (DYm).
Translocation of Bax to mitochondria, activation of Bax and release of
cytochrome c are all late events in this form of apoptosis. Loss of DYm is
illustrated as the thin black lines surrounding the mitochondria.
42. Apoptosi caspasi-indipendente
AIF-Apoptosis Inducing Factors
Mediatori di recente identificazione, traslocano dai
mitocondri al citosol e al nucleo.
AIF nucleari inducono la condensazione della
cromatina e la frammentazione del DNA.
Bcl-2, Hsp-70 e Hsc-70 inibisce la migrazione di
AIF al nucleo.
La deplezione di Hsp-70 attraverso oligonucletidi
antisenso sensibilizza le cellule all’apoptosi AIF
mediata.
43. Anoikisi
“Senza casa”: apoptosi indotta dalla mancanza di
segnali intercellulari e/o di connessioni con la
matrice extracellulare.
Predominante è la via Fas-mediata che conduce
quindi all’apoptosi caspasi-dipendente.
Tuttavia presenta anche altre vie di induzione.
44. Anoikisi
Vie “alternative”:
-reclutamento diretto della caspasi-8 da recettori
per le integrine;
-FADD (Fas-associated death domain protein)
può essere attivato da alterazioni del
citoscheletro che inducono il rilascio di “recettori
di morte” (death receptors) che si trovavano in
uno stato di sequestro.
HSP-27 fosforilato, HSP-70 e -90 stabilizzano le
integrine nei trombociti.
45. Anoikisi
HSP-27 fosforilato sembra inibire il potenziale
metastatico del melanoma mentre HSP-60 attiva
un’alfa3beta1-integrina coinvolta nell’adesione di
cellule metastatiche di ca. mammario a linfonodi e
osteoblasti.
BAG, una co-chaperone di HSP-70/HSC-70, lega
e sequestra FADD, inibendo così l’anoikisi.
Molti tumori metatstatici sembrano avere alta
espressione di BAG.
46. Considerazioni finali
Il processo apoptotico è finemente regolato e le
HSP svolgono un ruolo fondamentale nella sua
evoluzione, talvolta favorendo altre volte
ostacolando l’apoptosi.
La biologia molecolare sta mettendo in luce come
sia fondamentale capire nel dettaglio i passaggi
che conducono alla morte o alla sopravvivenza di
una cellula al fine di poter sperimentare nuove
strategie terapeutiche.
Le HSP si propongono come un possibile
importante bersaglio visto il loro ruolo chiave nei
processi cellulari.
47. Alcuni esempi
HSP-27 aumenta la ‘aggressività di cellule di ca.
colico mentre HSP-70 è altamente espresso in
tumori della mammella nella donna.
HSP-90 è implicato nella aggressività del ca.
prostatico.
Le HSP vengono espresse da molte cellule
tumorali a livello di membrana e possono agire da
adiuvanti del sistema immunitario aspecifico.