heterotrimeric G Protein Pathway

5 steps

1) G Protein coupled receptor (GPCR)

-binds ligand

= confo change --> active GPCR

2) GPCR Binds to inactive G protein-GDP

- 3 subunits

- alpha and Gamma bound to PM

- Beta + Gamma = in a complex togethor

3) GDP bound to Gamma leaves

- GTP binds and signal is amplified

-- GPCR == GEF

4) Alpha dissociates from B*G

-alpha freed and becomes active

5) Alpha binds effector (adenylylcylase)

activates effector

Adenyl --> makes cAMP == SIGNAL AMPLIFICATION

phosporylation of cytoplasmic region of GPCR

- by GPCR Kinase

-binding of arrestin

happens when P takes place

turns GPCR off

Arresting binds to same place as G protein

Desensitization

-arrestin rectruits clathrin

-causes vesicle to form

takes receptor off membrane

increase hydrolysis of GTP on Alpha G protein

- a GAP

-leads to A*B*G reformation into trimeric G protein

in membrane

makes ATP --> cAMP

cAMP = signaling molecule for cell

secondary messenger

give most amplifaction

Steps

1) epinephrine - binds to receptor on outside of cell =  GPCR

2) adenylylcylase activated in the membrane

3) cAMP binds to PKA

-removes regulatory seq

4) PKA phosphylates Glycogen Synthetase

-turns off glycogen synth

-GS takes glucose out of the blood to my glycogen (storage)

5)PKA phosphys phosphorylase kinase

6) PhosK P's glycogen Phosphorylase

7) Gly Phosp

-leads to breakdown of glycogen by adding P to it

8) Glucose enters blood stream

9) PKA phosphys CREB

creb - cAMP response element binding

-RE = binds TF, turns on gene

creb binds DNA in promoter, serves as TF

cAMP phosphodiesterase

- cAMP--> AMP (inactive)

Localization

Substrate not around

inhibitors

-Active as a Dimer

-phosphys one another!!

-each monomer P the other one

-binding of ligand allows for two monomers to form dimer

-adapter binding

-SH2 domain on PTB domain

1) growth factor binds to TK

2) Receptor dimerizes and Auto P

3) bind adapter protein

-SH2+PTB

3b) SOS binds to adapter

- GEF

4) SOS activates Ras

-exchange GDP --> GTP

-Ras membrane bound

5) Ras activats a MAP KKK cascade

-activates Raf = MapKKK

6) Raf activates MapKK by Phosphy

7) MapKK --> MapK

-MapK goes into nucleus

7b) Bind to promoter

7c) MapK activates a TF

8) 1 gene activated during process

-MapK phospotase

- Removes P from mapK

-STOPS PROCESS

- identified as oncogene

-small G protein.. about 100 of them

-related to RAN

-GTPase

1) M phase= mitoses = cell division

-only small % of cells in M phase

-about an Hour long

-dont make macro molecules

2) Interphase - G1, G2, S

-cell growth

Growth Factor signals from the outside

-cylins

-cyclins regulated in waves

-previous cyclin activates trxn of the next cyclin

1) rapid inactivation of trxn factor creating mRNA

= no new mRNA

2) current mRNA left over broken down by 3' UTR

3) cyclin proteins degraded

cyclins alone have no effect

-they must activate a CDK

-CDK always in the cell (not in waves)

togethor alter cell cycle

- cyclin and CDKs can mix to give diff effects at cell cycle times

-usually activate the process at hand, but can pause it too

G1/S cylin - reg G1into S phase, start making protein

S cyclin - Regulate chromosome Dup

-stays til mitosis

M cyclin - mitosis

-help cross G2/M checkpoint

1) cyclin levels

- no cyclin no CDK activated

2) Phospho the CDK

3)CDK inhibitors

4) proteolysis of CDK

5) localize where CDK is

Binds to cyclin

-only partially active

-T loop becomes accessible

-fully activates by Phospho of T loop

-done by CAK on Thr #161

(cylin activating kinase)

can inhibit by P too at second sight

- Wee1on Tyr # 15

-CDC25

-phospotase, removes P from the CDK inhibition sight