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Senescence: Difference between revisions
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!width="20"| '''Inducing Factors''' | !width="20"| '''Inducing Factors''' | ||
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| | | Fas and the TNF receptor are integral membrane proteins with their receptor domains exposed at the surface of the cell | ||
binding of the complementary death activator (FasL and TNF respectively) transmits a signal to the cytoplasm | binding of the complementary death activator (FasL and TNF respectively) transmits a signal to the cytoplasm | ||
| | | In a healthy cell, the outer membranes of its mitochondria display the protein Bcl-2 on their surface | ||
| | | AIF is released from the mitochondria (like the release of cytochrome c in the first pathway) | ||
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| | | This leads to the activation of caspase 8 | ||
| Internal damage to the cell (e.g., from reactive oxygen species) causes | | Internal damage to the cell (e.g., from reactive oxygen species) causes | ||
Bcl-2 to activate a related protein, Bax, which punches holes in the outer mitochondrial membrane, causing | Bcl-2 to activate a related protein, Bax, which punches holes in the outer mitochondrial membrane, causing | ||
cytochrome c to leak out | cytochrome c to leak out | ||
| | | It then migrates into the nucleus | ||
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| Caspase 8 (like caspase 9) initiates a cascade of caspase activation leading to | | Caspase 8 (like caspase 9) initiates a cascade of caspase activation leading to | ||
phagocytosis of the cell | phagocytosis of the cell | ||
| The released cytochrome c binds to the protein Apaf-1 ("apoptotic protease activating factor-1") | |||
| The released cytochrome c binds to the protein Apaf-1 ("apoptotic protease activating factor-1") | | And binds to DNA | ||
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| Using the energy provided by ATP, these complexes aggregate to form apoptosomes | | Using the energy provided by ATP, these complexes aggregate to form apoptosomes | ||
| | | Which triggers the destruction of the DNA and cell death | ||
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|The apoptosomes bind to and activate caspase-9 | |The apoptosomes bind to and activate caspase-9 | ||
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| Caspase-9 is one of a family of over a dozen caspases. They are all proteases. They get their name because they cleave proteins — mostly each other — at aspartic acid (Asp) residues) | | Caspase-9 is one of a family of over a dozen caspases. They are all proteases. They get their name because they cleave proteins — mostly each other — at aspartic acid (Asp) residues) | ||
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| Caspase-9 cleaves and, in so doing, activates other caspases (caspase-3 and -7) | | Caspase-9 cleaves and, in so doing, activates other caspases (caspase-3 and -7) | ||
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| The activation of these "executioner" caspases creates an expanding cascade of proteolytic activity (rather like that in blood clotting and complement activation) which leads to digestion of structural proteins in the cytoplasm, degradation of chromosomal DNA, and phagocytosis of the cell | | The activation of these "executioner" caspases creates an expanding cascade of proteolytic activity (rather like that in blood clotting and complement activation) which leads to digestion of structural proteins in the cytoplasm, degradation of chromosomal DNA, and phagocytosis of the cell | ||
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== Senesence Hormones == | == Senesence Hormones == | ||
