Exam 4 Lesson 8

Question 1

What extracellular factors integrate to influence cell growth?

Answer 1

nutrients
mitogens
Growth factors
survival factors

Question 2

what is rapamycin? where does it come from?

Answer 2

a fungal antibiotic

from streptomycin

Question 3

How does rapamycin limit cell growth?

Answer 3

a. mutagenize yeast
b. look for growth and rapamycin
c. identified mutants defective a protein kinase - “Target of Rapamycin” or TOR

Question 4

What is TOR?

Answer 4

Target of rapamycin - a cytosolic protein kinase

Question 5

What does TOR do?

Answer 5

It integrates growth factor signaling and nutrient status.

It leads to increased ribosome production and protein synthesis.

Question 6

What is different in TOR expression between queen bees and hive bees? What happens if TOR is knocked out with RNAi in queen bees?

Answer 6

TOR protein is expressed at higher levels.

Knockout results in bees with size and morphology of worker bees.

Question 7

How does myostatin regulate skeletal muscle cell size?

Answer 7

via the TOR pathway. An increase in TOR pathway results in increased muscle mass.

Question 8

What does TOR pathway regulate?

Answer 8

a. longevity of unicellular and multicellular organisms

b. muscle mass

Question 9

What does caloric reduction cause when it comes to TOR pathway? How?

Answer 9

increased life span

may be due to reduced incidence of cancer or other age-related diseases

Question 10

What are the two types of cell death?

Answer 10

programmed cell death and necrosis

Question 11

What are the two kinds of programmed cell death?

Answer 11

apoptosis and autophagic cell death

Question 12

What happens during apoptosis?

Answer 12

a. cell shrinkage
b. “blebbing” of plasma membrane
c. orderly processing of DNA
d. degradation and cleavage of DNA
e. “clean” – no cellular leakage because membrane enclosed
f. no inflammatory response

Question 13

What mediates autophagic cell death?

Answer 13

lysosomes

Question 14

How is autophagic cell death similar to apoptosis?

Answer 14

similar hallmarks
neat - no inflammatory response
phagocytosis happens by adjacent cells

Question 15

What is necrosis?

Answer 15

death of cell by insult/injury

causes cells to swell/burst with inflammatory response

Question 16

Why do apoptosis (2)?

Answer 16

a. development – remove web b/w digits, for example

b. kill “dangerous” cells - infected or serious DNA damage

Question 17

what are the key mediators of apoptosis?

Answer 17

caspases

Question 18

What are caspases? What kinds are there? How many types?

Answer 18

special proteases that mediate apoptosis. There are ten types. There are effector and executioner caspases.

Question 19

How does caspase work?

Answer 19

a. start with inactive pro-caspase that has inhibitor attached to it
b. signal results in auto cleavage of inhibitor
c. effector caspase is now active
d. effector caspase cleaves other caspases, leading to caspase cascade
e. caspase cascade turns into executioner caspases
f. executioner caspases target nuclear lamina, actin network, etc.

Question 20

How do survival factors adjust the number of developing nerve cells to the amount of target tissues?

Answer 20

nerve cells receive an insufficient amount of survival factors to avoid apoptosis. More nerve cells are produced that can be used, but they are kept surviving with minimal survival factors until they can be eliminated.

Question 21

How does DNA fragmentation work with executioner caspase?

Answer 21

a. start with endonuclease CAD associated with an inhibitor
b. executioner caspase cleaves inhibitor
c. CAD is active
d. CAD cuts chromosomal DNA between nucleosomes

Question 22

In DNA fragmentation assay, why is there a barred pattern?

Answer 22

because nuclease is cleaving between histones

Question 23

Two ways caspases are activated?

Answer 23

extrinsic pathway

intrinsic pathway

Question 24

Describe extrinsic pathway.

Answer 24

extrinsic means from outside of cell.

a. Fas trimeric ligand (killer lymphocyte) on external cell binds with trimeric death receptor
b. receptors cluster and activate death domains on the receptor tails
c. death domains interact with similar domains on FADD adaptor protein
d. FADD protein recruits initiator caspase via a death effector domain on both FADD and caspase
e. this forms Death-inducing signaling complex (DISC)
f. within DISC, two initiator caspases interact and cleave one another to form an activated protease dimer
g. dimer cleaves itself in region linking protease to the death effector domain
h. this stabilizes and releases active caspase into cytosol, where it activates executioner caspases by cleaving them.

Question 25

when is extrinsic pathway used?

Answer 25

a diseased cell targeted by immune cell

b. cell killed during development

Question 26

What does intrinsic pathway require?

Answer 26

cytochrome C release from mitochondria

Question 27

When is intrinsic pathway used?

Answer 27

for infected cell or DNA damage

Question 28

Describe intrinsic pathway.

Answer 28

a. apoptotic intracellular stimulus gets mito to release cytochrome C
b. cyto C binds with Apaf1 and activates it
c. seven activated Apaf1 proteins form apoptosome
d. each Apaf1 protein has a caspase recruitment domain (CARD)
e. CARDs bind domains in similar caspase 9 molecules
f. once activated, caspase 9 cleaves and activates executioner caspases
g. this leads to caspase cascade that leads to apoptosis

Question 29

What family of proteins regulates intrinsic pathway?

Answer 29

Bc12 family

Question 30

How do Bc12 proteins control intrinsic pathway?

Answer 30

control release of Cytochrome C from mito

Question 31

what kinds of Bc12 proteins are there?

Answer 31

pro-apoptotic and anti-apoptotic

Question 32

pro-apoptotic Bc12 family members? How do they work?

Answer 32

Bax/Bak

form channels in outer mitochondrial membrane and help release cyto c into cytosol, which leads to a caspase cade

Question 33

BH3 only protein

Answer 33

stimulated by pro-apoptotic proteins, it inhibits anti-apoptotic proteins

Question 34

How does apoptotic stimulus work to activate effector Bc12 proteins on mitochondrial outer membrane?

Answer 34

Apoptotic stimulus aggregates active effector proteins and proteins release cyto C into cytosol.

Question 35

How is intrinsic pathway activated?

Answer 35

a. start with inactive pathway, which consists of Bax/Bak proteins on mito membrane that are isolated from each other and blocked from cytosol by anti-apoptotic proteins.
b. activate BH3-only protein via apoptotic stimulus
c. BH3-only inhibits anti-apoptotic proteins
d. effector proteins aggregate and let cyto C out of mito

Question 36

How does DNA damage lead to cell death?

Answer 36

DNA damage leads to activation of p53, a transcription factor. p53 leads to the expression of p21 and BH3-only.
P21 is a CKI that arrests cell cycle. BH3-only inhibits anti-apoptotic proteins that inhibit Bax/Bak.

Question 37

Three ways that survival factors can inhibit apoptosis

Answer 37

a. increased production of anti-apoptotic Bc12 family protein
b. inactivation of pro-apoptotic BH3-only protein
c. inactivation of anti-IAPs

Question 38

IAP

Answer 38

inhibitors of apoptosis

Question 39

Hid

Answer 39

anti IAP protein in Drosophila

Question 40

Bad

Answer 40

pro-apoptotic protein BH3-only

Question 41

How do survival factors increase production of anti apoptotic BC12 protein family?

Answer 41

a. activate transcription regulator
b. regulator translocates into nucleus
c. Bc12 protein synthesis

Question 42

How do survival factors inactivate pro-apoptotic BH3-only proteins?

Answer 42

a. activate Akt kinase
b. inactivate Bad
c. activate Bcl12 that is anti apoptotic

Question 43

How does survival factor inactivate anti IAP in drosophile?

Answer 43

a. activate MAP kinase pathway

b. inactivates Hid, which works against the inhibition of apoptosis.