Receptors & Cell Signaling

Question 1

endocrine signaling

Answer 1

long-acting, travel in blood, long-distance

hormones, epi

Question 2

paracrine signaling

Answer 2

short-lived
neighbor target cell
ex: testosterone

Question 3

juxtacrine signaling

Answer 3

direct signaling, substrate forms bridge w/ neighboring cell

heparin binding epidermal growth factor immune cells

Question 4

autocrine signaling

Answer 4

signal acts on it’s own cell/cells of same type
growth factors in cancer
chemokines (T-lymphocytes -> produce interleukin 1-> promotes their replication for immune response)

Question 5

Gs GPCR response

Answer 5

STIMULATES adenylate cyclase –>
cAMP
turns on PKA
P targets

ex:
Epi -> B-adrenergic receptor
Histamine -> recep -> bronchoconstriction, allergic rxn

Question 6

Gi GPCR response

Answer 6

INHIBITS adenylate cyclase ->
cAMP not produced
PKA not activated
targets not phosphorylated

Epi/norepi -> a-adrenergic rec -> constrict smooth muscle

Dopamine -> dopa rec. -> inc HR

Question 7

Gt GPCR response

Answer 7

STIMULATES cGMP phosphodiesterase (PDE)
GPCR pathway -> activates cGMP PDE -> response

light -> rhodopsin (GPCR rec) -> vision

Question 8

Gq GPCR response

Answer 8

ACTIVATES phospholipase C (PLC)
GPCR pathway -> activates PLC -> DAG + IP3

DAG -> PFK -> P targets
IP3 binds ER -> Ca2+ release -> activation

Acetylcholine -> muscarinic rec.

Question 9

activation and inactivation of GPCR

Answer 9

ACTIVATION - Guanine Exchange Factors (GEFs) * GDP -> GTP

INACTIVATION - GTPase activating ptn (GAPs)
* GTP -> GDP -> inactive

Question 10

phosphodiesterases

Answer 10

hydrolyze cyclic part

cAMP -> AMP
cGMP -> 5’GMP

Question 11

role of G Protein Receptor Kinases (GRKs)

Answer 11

phosphorylate GPCR
arrestin binds
inactivate G complex response

Question 12

RAS-dependent pathway

Answer 12

Receptor thyrosine kinase pathway -->
(ligand, dimerization, autoP) --> 
MAPK pathway (mitogen-activated ptn kinase)
-> transcription factor P 
-> gene transcription
-> ptn synthesis

Question 13

How is cancer related to RTKs?

Answer 13

mutation in PRK pathway, GEFs, GAPs ->
dec GTPase activity - stuck in GTP bound active state
constant transcription
cancer

ex: breast cancer, HER2 gene

Question 14

Pertussis/wooping cough

Answer 14

Gi(a) mutation of CYSTEINE residue (GPCR pathway)
a-subunit can’t disassociate
AC continually active
cAMP overproduction
fluid loss, mucous in airway of epithelial cells

Question 15

Cholera

Answer 15

mutation in Gs(a) ARGININE residue 
GPCR pathway stuck in activated state 
dec. GTPase activity 
overproduction of cAMP (can't turn off) 
Cl- channels stuck open 
Na+ and H2O follow 
diarrhea

Question 16

What happens if you inhibit phosphodiesterases?

Answer 16

cAMP or cGMP continually active

Question 17

Mechanism of Viagra

Answer 17

inhibits phosphodiesterase

continual smooth muscle relaxation/vasodilation

Question 18

Mechanism of Nitric Oxide

Answer 18

activate guanylase cyclase
increase cGMP
vasodilation/dec. BP