Lecture 5 - Exam

Question 1

What is apoptosis?

Answer 1

Programmed cell death that is genetically encoded and tightly regulated, occurs at predictable places at predictable times

Question 2

What is the term for uncontrolled cell death and why does it occur?

Answer 2

Necrosis - occurs in response to physical injury with rapid loss of PM integrity

Question 3

What are some functions of apoptosis?

Answer 3

Normal development, eliminate used immune or damaged cells, provide tissue homeostasis between proliferation/cell death

Question 4

What are markers of apoptosis?

Answer 4

Cell shrinkage, chromatin condensation, membrane blebbing, apoptotic body formation, DNA fragmentation, Phosphatidylserine flipping

Question 5

What is the model organism for apoptosis?

Answer 5

C. elegans

Question 6

What are the pro-survival proteins?

Answer 6

Bcl-2, Bcl-xL, Bcl-w, Mcl-1, A1 - have 4 BH domains

Question 7

What are the pro-apoptoic proteins?

Answer 7

Bax, Bak, Bok - have 3 BH domains

Question 8

What are the pro-survival and pro-apoptotic regulators?

Answer 8

Bim, Puma, Noxa, Bik, Bmf, Bad, Bid, Hrk - only have Bh-3 domain - fall under pro-apoptotic category

Question 9

What family do pro-survival and pro-apoptotic proteins belong to?

Answer 9

Bcl-2 family

Question 10

What is caspase 9?

Answer 10

The initiator of the intrinsic pathway - contains CARD - caspase recruitment domain

Question 11

What is caspases 8,10?

Answer 11

The initiators of the extrinsic pathways - contain DED - death effector domain

Question 12

What is caspase 3?

Answer 12

The executioner caspase

Question 13

How is DNA fragmentation carried out?

Answer 13

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

Question 14

What is the intrinsic pathway of apoptosis?

Answer 14

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

Question 15

What does pro-caspase 9 activation require?

Answer 15

Apaf-1, cytochrome c, dATP

Question 16

What are IAPs and what do they do? How are they regulated?

Answer 16

XIAP, cIAP, NAIP, ML-IAP - prevent cell death by binding and inhibiting caspases - negatively regulated by IAP binding proteins SMAC/DIABLO

Question 17

What are Smac (diablo)? What is analogous in drosophila?

Answer 17

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

Question 18

How is the extrinsic pathway triggered? And what is it regulated by?

Answer 18

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

Question 19

What is DISC?

Answer 19

Death inducing signaling complex in extrinsic pathway - made up of FADD signaling to procaspase 8 and caspase 8

Question 20

What are the cancer therapeutics used to target the apoptotic pathway?

Answer 20

BH3 mimetics to inhibit Bcl2 and Bcl-x binding to free up pro-apoptotic proteins
Smac mimetics to bind and inhibit IAPs

Question 21

What does p53 have to do with apoptosis?

Answer 21

When cell senses damage mdm2 (the inhibitor) release from p53 which decides to activate repair or apoptosis of the cell

Question 22

What do CDKs do?

Answer 22

Bind different cyclins to promote cell cycle transitions

Question 23

What are cyclins degraded by?

Answer 23

SCF and APC/C

Question 24

What are the G1 CDK/cyclins?

Answer 24

CDK4/6 and cyclin D

Question 25

What are the G1/S CDK/cyclins?

Answer 25

CDK2 and cyclin E and A

Question 26

What are the mitotic CDK/cyclins?

Answer 26

CDK1 and cyclin A and B

Question 27

What is a stage in G1 in which cells become irreversibly committed to the cell cycle?

Answer 27

START

Question 28

What is the roll of CDKs in G1?

Answer 28

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

Question 29

What inhibits S phase CDKs?

Answer 29

Sic - until it is phosphorylated and dissociates and degraded by proteasomes allowing DNA replication to continue

Question 30

What inhibits Mitotic CDKs? And what activates them?

Answer 30

Wee - inhibitor must become inactivated and Cdc25 must become activate in a feedback loop

Question 31

What else inhibits S phase CDKs?

Answer 31

p27 - prevents premature activation of S phase CDKs - also is phosphorylated for degradation allowing for cyclin activation

Question 32

How do S phase CDKs trigger DNA replication?

Answer 32

Recruit MCM helicase activators to origins

Question 33

What do mitotic CDKs do in the cell cycle?

Answer 33

Promote nuclear membrane breakdown by phosphorylation of lamins and nucleoporins - promote spindle formation (centrosome disjunction) - trigger condensin complex to condense chromosomes