Apoptosis

Question 1

Describe cell morphological changes in apoptosis?

Answer 1

Condensation of cytosol (eosinophilic cytoplasm)
Membrane blebbing into fragments
Fragments phagocytosed by surrounding cells
Cell loss not readily apparent

Question 2

Important differences between apoptosis and necrosis?

Answer 2

Necrosis will extrude its contents, leading to inflamm. Apop will not.
Necrosis has apparent cell loss, apop doesn’t necessarily.

Question 3

Causes of physiologic apoptosis (5)

Answer 3

Embryogenesis, Clonal deletion, hormone dependent processes, T cells/Immune Modulation, Maintenance of rapidly dividing.

Question 4

Causes of pathologic apoptosis (5)

Answer 4

Virus
2dary to obstruction, Hypoxia
Heat, Radiation
Cytotoxic Drugs
Tumor-assocaited Necrosis

Question 5

What should you know about Caspases

Answer 5

Carry out protein hydrolysis
Zymogens, Activated by initiator or autocatalytic
Cleave nuclear+cytoskeletal scaffold (lamins)
Cause protein crosslinking
Triggers endonuclease activity

Question 6

How does DNA breakdown in apoptosis happen?

Answer 6

Activation of Ca and Mg dependent endonucleases

First, break into 50-300 kb pieces, then internucleosomal clevage to multiples of 180-200

Question 7

How do phagocytic cells know a cell is apoptotic and should be eaten?

Answer 7

Expression of phosphatidylserine ont he outside of the phospholipid membrane (flipped) or thrombospondin expression

Question 8

Explain the Bcl-2 pathway for regulating mitochondrial fxn

Answer 8

Sensors activate pro-apoptotic members of Bcl-2 family

Release of Cytochrome C as a signal and a docking protein for caspases.

Question 9

name anti-apoptotic proteins

Answer 9

bcl-2, bcl-x

Question 10

name pro-apoptotic proteins

Answer 10

bim, bid, bad

BAX AND BAK

Question 11

Explain the Fas ligand model of apoptosis

Answer 11

Cross linking of TNFR1 or FAS (CD95) allows T cell binding to trigger apoptosis.
Activated surface ligand allows death domain integration into receptor.
Subsequent FADD and Procaspase 8 Activation.

Question 12

So FAS and Bcl-2 lead you up to the execution phase, whats that all about?

Answer 12

Caspases disrupt cytoskeleton+nuclear matrix

Activation of internucleosomal clevage of DNA

Question 13

How do live cells prevent phagocytosis?

Answer 13

Expression of CD31

Question 14

Two methods of CD8 T cell mediated death

Answer 14

FasL binding

Perforin release –> transmembrane pore formation