Apoptosis Mech Lec 3

Question 1

What are two ways in which cells die?

Answer 1

1. necrosis(massive death) (inflam)all die at one time
2. apoptosis / PCD- intrinsic to the cell, under genetic control(no inflammation)
   process where single cells activate and intrinsic death program to kill themselves

Question 2

What are normal responses to physiological stimuli?

Answer 2

A. fetal development
1. removing webbing between fingers
2. male or female reproductive organs
3. after infancy: shrinkage of thymus glands
B. Adulthood
1. menstrual shed
2. autoimmune cells
3.aging cells
4. cells turnover in intestinal crypts

Question 3

What are pathological situations apoptosis occurs in?

Answer 3

1. infected or injured cells(HIV, HepB)
2. cells with DNA damage(radiation, drugs, birth defects)
   3.cancer(chemo)
3. transplant rejections

Question 4

What makes a cell decide to commit suicide?

Answer 4

1. the withdrawal of positive signals (needed for survival)
   -growth factor for neurons
   -interlukin -2 for lymphocytes
2. the receipt of neg signals
   -TNF(Tumor necrosis factor)
   -FAS Ligand (CD95)

Question 5

What are mech of PCD:

Answer 5

A. intrinsic mitochondrial pathway
-DNA damage and p53
-involves mitochondria/ cytochrome C and AIF that activate Caspase 9
B. External signal
-FAS-L and TNF bind to their receptors on the target cell
-transmit a signal to the cytoplasm
activates Caspase 8
C. Apoptosis Inducing Factor
-unique in the neural apoptosis, no caspases involved

Question 6

What are the ultimate executioners of PCD?

Answer 6

Caspases; cleave 100 diff cell target proteins
-the activation of an initiator caspase starts a chain reaction of caspase activation leading to death

Question 7

What is the regulation of Apoptosis:

Answer 7

BcL : family of proteins reside mainly in the mitochondria
-Anti-apoptotic: BcL-2, BcL-xl
-Pro-apoptotic: Bax, Bad
-overexpressing of BcL- 2 gene will inhibit the apoptosis
Cytotoxic T cells /natural killer cells order the infected cells to PCD
-certain viruses have apoptosis brake genes inhibit the infected cells from committing suicide
2. mebrane bulges-bleb
3. nuclear mebranes breaks: endonucleases clip chromosomes (at histones linker region, about 180-200 base pair interval)….nucleus may break up into 2 or more fragments
4. cell fragments produce apoptotic bodies
5. phagocytosis(macrophages) or adjacent

Question 8

What is p53 gene:

Answer 8

tumor Suppressor gene: regulates cell division by keeping cells from dividing or replicating too fast or in an uncontrolled way
Bcl protein- makes sure to regulate apoptosis

Question 9

What is the future of PCD:

Answer 9

increased apoptosis seen in:
Azheimers
viral infections
graft infection
Decreased apoptosis seen in:
autoimmune diseases-arthritis
cancer
AIDS-CD4 T-cells less than 1 in 100,000 cells are infected most of the cells that die are uninfected
aging