Lecture 13

Question 1

enzyme coupled receptors

Answer 1

the cytoplasmic portion acts as an enzyme of forms a complex w an enzyme

Question 2

receptor tyrosine kinases

Answer 2

signals binding it are growth factor and hormones
causes dimerization and turns on enzymatic activity

when ligand binds eat receptor tail phos. the other. = become docking sites for intracellular signaling proteins, which now,
1. become phos., activated and propagate the signal
2. function as a scaffold to relay the signal

Question 3

Ras/MAPK pathway

Answer 3

almost all RTK’s activate G protein called Rat

Ras-GEF helps activate RAS by stimulating exchange of GDP for GTP= switch on

active RAS initiates a phosphorylation cascade involving a series of serine protein kinases (MAPKKK, MAPKK, MAPK).

activated RAS binds and activates MAP3K
active MAP3 phos many MAP2K
active MAP2K ohos many MAP kinases
active MAP can enter the nucleus and stimulates cell division.

Question 4

RAS/MAPK termination

Answer 4

RTK dephosph.
RTK removal from mb
RAS inactivation, turned off
= through hydrolysis of GTP to GDP (stimulated by Ras-GAP

Question 5

PI3K/AKT pathways

Answer 5

signal binds to RTK
RTK dimerizes and phases.
activates PI3K
PI3K phosph. PIP2 to PIP3
PIP3 joins with AKT on the mb
gets phosph. and activated by 2 protein kinases.

now,
it phos. Bad, which inactivated Bad and activated Bcl2 = imp for cell survival (inh cell suicide).