Feb 11

Question 1

Mutations in RAS gene that lead to tumor formation prevent __________?

Answer 1

Prevent the hydrolysis of GTP, so Ras always active, so keep proliferating

Question 2

What 2 things does Ras interact with?

Answer 2

RAF (MAPKKK), it interacts with it and so Raf dimerizes and autophosphorylates. It also interacts with PI3K.

Question 3

What is the Ras activation/inactivation cycle?

Answer 3

1. GEF SOS binds to RAS, causes it to kick out GDP
2. GTP binds as high conc, get conformational change
3. GEF leaves, GTP-Ras binds to target.
4. GAP (GTPase activating protein) binds to Ras, increases GTPase domain activity, so GTP hydrolysis, it is now inactive

Question 4

What are the 3 oncogenic mutational hotspots in RAS genes?

Answer 4

G12, G13, Q61. Glycine 12 and 13 prevent GAP interacting with RAS, so almost always on. Q61 will inhibit GTP hydrolysis. They decrease the rate of intrinsic GTP hydrolysis

Question 5

What is diff in MAPK activity when using epidermal vs nerve GF? Why do we see this?

Answer 5

EGF shows that get peak in MAPK activity causing proliferation, but NGF is more sustained activity, causing differentiation.

NF1 is a GAP protein, it is PO4’d by MAPK used in NGF pathway, this prevents it from binding and accelerating GTP hydrolysis, so get prolonged signal.

Question 6

How does Ras interact with Raf (MAPKKK)? What happens as result/

Answer 6

Raf has Ras binding domains, so it uses that to be activated so it can dimerize and autophosphorylate itself on activation loop, so now Raf active and will PO4 MAPKK.

Question 7

Type 1 vs Type 2 diabetes/

Answer 7

Type 1 is don’t make insulin, type 2 is make it but are resistant to it

Question 8

What are the 3 MAPK pathways in mammalian cells/

Answer 8

Growth factors, inflammatory cytokines, stress

Question 9

How does MAPKK interact with MAPK?

Answer 9

Though KIM (kinase interaction motif)

Question 10

What is insulin binding pathway?

Answer 10

1. Insulin binds to receptor
2. Receptor autophosphorylates on Tyr
3. The IRS (insulin-receptor substrates) then binds to PO4’d Tyr with PTB domain, and has site for Grb2, PI3K and other binding sites.
4. The PI3K then PO4’s PI45 to give PIP3.
5. PIP3 is used as anchor point for PKB adn PDK1 that have PH domains.
6. PDK1 (phosphoinositide dependent kinase 1 then PO4’s PKB, which then does other stuff, like helping GLUT4 vesicle fuse to plasma MB, so glucose transporters now present so can import glucose into cell