Cell Death Flashcards
Intrinsic mechanism of apoptosis initiated by
Irreparable DNA damage
Hypoxia
Increase Ca levels
Severe oxidative stress
Steps in apoptosis
Cell shrinkage Chromatin condensation/ margination Membrane blebbing Nuclear collapse Apoptotic body formation Lysis of apoptosis bodies
Intrinsic pathway - apoptosis
Increase p53, increase BAX.
Permeable mitochondria membrane.
Release of SMAC/ DIABLO -> inhibits inhibitors of apoptosis IAPs
Release of cytochrome C, binds apoptosis protease activity factor Apaf 1. Forms apoptosome which activates caspase 9.
Activation of effector caspase a 3, 6, 7.
Extrinsic pathway - apoptosis
Proapoptotic ligand a bind receptor (TNF/Fas)
Recruitment of death domains (TRADD/FADD)
Procaspase 8 (initiator caspase) binds and forms DISC - death inducing signaling complex.
Procaspases brought into close proximity, auto catalytic processing.
Activates effector caspase a 3,6,7.
What do caspases do?
Activate endonucleases and proteases
3,8 regulate phosphatidyl serine expression
3,6,7 cleave substrates.
Biochemical features of apoptosis
Protein cleavage Protein cross linking DNA breakdown Phosphatidyl serine expression Caspases
Assays for apoptosis
DNA fragmentation - TUNEL assay
- caspase activated DNase cut internucleosomal sites
Caspases detection - ELISA
- Western BLOT
Alteration in membrane - annexing V assay
Mitochondrial assay - laser scanning confocal microscopy LSCM
Types of necrosis
Liquifactive Coagulative Haemorrhagic Toxin induced Viral Caseous
Necrosis - changes in cell morphology
Increase size, organelles swell, plasma membrane rupture, loss of cell contents.
Nuclear changes in necrosis
Chromatin clumping, karyohexis, pyknosis, karyolysis.
Triggers of autophagy
Protein aggregation Organelle damage Nutrient depletion Growth factor deprivation Microbial infection
Three types of autophagy
Microautophagy
Chaperone mediated autophagy
Macroautophagy
Process of microautophagy
Cytoplasmic contents enter directly into lysosomes. Degraded by hydrolases
Process of chaperone mediated autophagy
Hsc70 recognizes KFERQ.
Co chaperones unfold protein.
Lamp2 translocates protein into lysosomes.
Degraded by hydrolases.
Process of macroautophagy
Engulfment of components by phagophore.
Phagophore extends creating double membrane vehicle = autophagosome.
Fuses with lysosome. Inner membrane and protein content hydrolysed = autolysosome.
