Lec 7 - Cell Death

Question 1

Two major types of cell death are _____ and _____

Answer 1

Regulated cell death (programed cell deat) and necrosis or damaged

Question 2

Two major types of regulated cell death

Answer 2

non-inflammatory and pro-inflammatory

Question 3

example of non-inflammatory and pro-inflammatory regulated cell death

Answer 3

Non-inflammatory = apoptosis (which can be either intrinsic or extrinsic)

instinsic = suicide = mitocondria * major pathway between in and ex

triggered by cell stress such as removal of trophic factors or cell DNA damage

extrinsic = murder- can be either through:
-death report / ligand pathway *major - example FasL and FasR
or
- perforin granzyme pathway *minor

pro-inflmamatory = pyroptosis

Question 4

How do chemotherapy and radiotherapy effect the cells

Answer 4

Aim to trigger apoptosis in cancer cells

Question 5

How is apoptosis different from necrosis

Answer 5

Apoptosis - cell membrane stays intact
- content never spills out
- cell shrink
- single cell or small cluster
- pyknosis (condensed chromatin) and karyorrhexis (nuclear fragmentation)
- no inflamation
- - cell breaks into smaller intact fragments called apoptotic body which are taken up by phagoctyes
- membrane blebbing

vs necrosis

Question 6

How are apoptotic bodies taken up by phagocytes?

Answer 6

They show “eat me” and “find me” singals

Find me - nucleoside triphosphates (NTPs) release to attracct phagocytes

Eat me - Phosphatidylserine externalization some membrane [ ] flip to the outside, seen by phagocty

Question 7

Caspase 1 works in which pathway?

Answer 7

pyrotosis (pro-inflammatory)

Question 8

Caspase 3 works in which pathway and what does it activate?
What three things does it lead to?

Answer 8

works in apoptosis (activated by caspase 9) and it activates proteolysis

proteolysis leads to:
- DNAse activation = DNA fragmenation
- Nuclear lamin destruction = fragmentation of nucleus
- Cytoskeletal protein destruction = distruption of cell transport, signaling, cell fragmentation, blebbing

Question 9

Cytocrome C is a co-factor for which enzyme?

Answer 9

Cytoplasmic APAF1

Question 10

What is Li-Fraumeni Syndrome?

Answer 10

A predispotsion for cancer
It is loss of second p53 in a somatic cell leads to increased mutation b/c checkpoint control and apoptotic pathways are blocked

classic presentation
- large fmaily history of cancer
- many different types of cancer in family / one person
- cancer at a young age

Question 11

What is the role of p53 in Apoptosis?

Answer 11

inhibiting cell cycle and increasing cell apoptosis through the intrinsic pathway

p53 acts as a transcription factor
- increases the expression of pro-apoptotic protiens = Bax, bak, bid
- decrease anti-apoptotic protiens = Bcl2
- makes more CDKIs / p21 to inhibit CDK/Cyclin activity

Question 12

What are the biochemical changes in apoptotic cells

Answer 12

• protien clevage
• DNA ladders
• protien-protien cross-linking due to “tissue transglutaminase
• externalization of phosphatidylserine

Question 13

Caspases are proteases? T/F

Answer 13

True

Question 14

Apoptosis is enforced by activing _____

Answer 14

caspases, powerful proteases

Question 15

Bcl2 / B-Cell Leukemia / Lymphoma 2 protiens

Answer 15

BCL2 issue
encoded on chr. 18
overexpreseed in translation t(14;18)
overexpression blocks apoptosis leading to B-cell leukemia / lymphoma

Question 16

Caspases ____ fragment chromosaomal DNA by activating _____

Answer 16

INDIRECTLY DNase

Question 17

Caspases have ____ in active sites and cut target protiens at ______

Answer 17

Cysteine (think C!)
Aspartates (asp!)

Question 18

Caspase genes encode for ____ and are expressed ______

Answer 18

pro-caspases
constitutively

Question 19

apoptosis requires the activation of pro-caspases by ____. It does not require _______.

Answer 19

proteolysis
increased caspase gene expression

Question 20

Where are regulatory events for apoptosis

Answer 20

mitochondiral surface

Question 21

Explain the role of the mitocondria in intrinsic apoptosis

Answer 21

cyctochrom c - co -factor, strucutral not enzymatic

Question 22

Three classes of BCL-2 superfamily protiens

Answer 22

Apoptosis inhibitors = Bcl-2

apoptosis effectos = Bax or Bak

apoptosis sensors = Bad, Bid

Question 23

DNA damage triggers apoptosis by overexpressing ____ and under-expressing ______

Answer 23

pro-apoptotic proteins (Bax, Bak, Bid, Bad etc)

apoptosis inhibitors (Bcl-2 etc)

Question 24

What is an apoptosome and how is it constructed?

Answer 24

It is a protien scaffold required for activating pro-caspase-9, which will eventually activate pro-caspase 3

Apaf-1: monomer - must be oligomerized for function.
*
Apaf-1 oligomerization requiresCytC, dATP & ATP.
*
“Apoptosome” (Apaf-1 heptamer) recruits Initiator Procaspase (Procaspase-9) to the ring center.
*
Bound Procaspase-9 undergoes auto-cleavage and assembles into active Caspase-9.
*
Caspase 9 cleaves Pro-Caspase-3 to activate Caspase-3, the Executor caspase.
20
Apaf-1, Apoptotic Protease Accessory Factor 1

Question 25

Which is the initiator caspase and which is the executor caspase?

Answer 25

9 = initiator
3 = executor

Question 26

What is FasL/RasR pathway?

Answer 26

membrane embedded death ligands (FasL)on cytotoxic lymphocytes (CTLs) recognize death receptors (FasR) on surface of target cells

have DISC scaffold

Question 27

How does perforin / granzyme pathway work?

Answer 27

minor extrinsic pathway

CTLs inject pore forming molecules into target cell called perforins

CTLs release serine protease granules called granzymes

granzymes can proteolytically active initiator caspases such as procaspase 10 so don’t need a scaffold

Question 28

Big picture

Explain the different ways cells can die and why it is important