Lecture 5 - Exam Flashcards
What is apoptosis?
Programmed cell death that is genetically encoded and tightly regulated, occurs at predictable places at predictable times
What is the term for uncontrolled cell death and why does it occur?
Necrosis - occurs in response to physical injury with rapid loss of PM integrity
What are some functions of apoptosis?
Normal development, eliminate used immune or damaged cells, provide tissue homeostasis between proliferation/cell death
What are markers of apoptosis?
Cell shrinkage, chromatin condensation, membrane blebbing, apoptotic body formation, DNA fragmentation, Phosphatidylserine flipping
What is the model organism for apoptosis?
C. elegans
What are the pro-survival proteins?
Bcl-2, Bcl-xL, Bcl-w, Mcl-1, A1 - have 4 BH domains
What are the pro-apoptoic proteins?
Bax, Bak, Bok - have 3 BH domains
What are the pro-survival and pro-apoptotic regulators?
Bim, Puma, Noxa, Bik, Bmf, Bad, Bid, Hrk - only have Bh-3 domain - fall under pro-apoptotic category
What family do pro-survival and pro-apoptotic proteins belong to?
Bcl-2 family
What is caspase 9?
The initiator of the intrinsic pathway - contains CARD - caspase recruitment domain
What is caspases 8,10?
The initiators of the extrinsic pathways - contain DED - death effector domain
What is caspase 3?
The executioner caspase
How is DNA fragmentation carried out?
Caspase 3/7 (executioner) activate removal of inhibitory unit on DFF (DNA fragmentation factor) 45/ICAD heterodimer to activate the DNAs - DFF40/CAD (caspase activate DNAse) that cuts linker DNA
What is the intrinsic pathway of apoptosis?
BH3 becomes activated by stress –> directly activates BAX/BAK –> BAX/BAK causes pores to open in mitochondrial outer membrane –> cytochrome c released and SMAC/DIABO (IAP binding proteins)–> binds with APAF1 –> activates procaspase 9 binds apoptosome –> cleaves caspase 3/7 –> leads to apoptosis
What does pro-caspase 9 activation require?
Apaf-1, cytochrome c, dATP
What are IAPs and what do they do? How are they regulated?
XIAP, cIAP, NAIP, ML-IAP - prevent cell death by binding and inhibiting caspases - negatively regulated by IAP binding proteins SMAC/DIABLO
What are Smac (diablo)? What is analogous in drosophila?
Mitochondrial proteins that bind to IAPs to promote caspase activity and cell death - Smac interacts with XIAP and DIablo with cIAP - analogous in drosophila are hid/grim/repear
How is the extrinsic pathway triggered? And what is it regulated by?
Triggered by death inducing cytokines like FasL/TNFalpha - where ligand binds receptor to signal to FADD (Fas-associated death domain) that contains DED to signal to procaspase 8 –> caspase 8 –> other caspases or BID –> death - regulated by FLIP
What is DISC?
Death inducing signaling complex in extrinsic pathway - made up of FADD signaling to procaspase 8 and caspase 8
What are the cancer therapeutics used to target the apoptotic pathway?
BH3 mimetics to inhibit Bcl2 and Bcl-x binding to free up pro-apoptotic proteins
Smac mimetics to bind and inhibit IAPs
What does p53 have to do with apoptosis?
When cell senses damage mdm2 (the inhibitor) release from p53 which decides to activate repair or apoptosis of the cell
What do CDKs do?
Bind different cyclins to promote cell cycle transitions
What are cyclins degraded by?
SCF and APC/C
What are the G1 CDK/cyclins?
CDK4/6 and cyclin D
What are the G1/S CDK/cyclins?
CDK2 and cyclin E and A
What are the mitotic CDK/cyclins?
CDK1 and cyclin A and B
What is a stage in G1 in which cells become irreversibly committed to the cell cycle?
START
What is the roll of CDKs in G1?
G1 CDKs activate E2F which is held inactive by Rb until it is released by phosphorylation - E2F then activates genes involved in DNA synthesis and stimulates transcription of genes for other cyclins
What inhibits S phase CDKs?
Sic - until it is phosphorylated and dissociates and degraded by proteasomes allowing DNA replication to continue
What inhibits Mitotic CDKs? And what activates them?
Wee - inhibitor must become inactivated and Cdc25 must become activate in a feedback loop
What else inhibits S phase CDKs?
p27 - prevents premature activation of S phase CDKs - also is phosphorylated for degradation allowing for cyclin activation
How do S phase CDKs trigger DNA replication?
Recruit MCM helicase activators to origins
What do mitotic CDKs do in the cell cycle?
Promote nuclear membrane breakdown by phosphorylation of lamins and nucleoporins - promote spindle formation (centrosome disjunction) - trigger condensin complex to condense chromosomes
