Signal Transduction II

Question 1

ligand gated ion channels

Answer 1

found on electrically excitable cells
when receptor is open, ions enter/ exit along electrochemical gradients
FAST response

Question 2

GABA receptor

Answer 2

inhibitory transmitter
opens Cl- channels, HYPERPOLARIZATION-> muscle relax

Question 3

PAMs

Answer 3

bind to sites other than GABA, enhance GABA dependent activity of receptor

Question 4

nicotinic acethycholinergic receptor

Answer 4

Ach binds to cause conformational changes
forms pore that allows Na+ to enter-> DEPOLARIZATION
ligand degraded by acetylcholinesterases and signal terminated

Question 5

alpha subunit of G-protein coupled receptors

Answer 5

binds to GTP/GDP
when bound to GTP=ON

Question 6

G alpha S

Answer 6

stimulates adenylyl cyclase and increases cAMP production

Question 7

G alpha I

Answer 7

inhibits adenylyl cyclase and decreases cAMP production

Question 8

G alpha Q

Answer 8

activates phospholipase C and stimulates IP3 and DAG production

Question 9

PIP2 will activate

Answer 9

DAG and IP3 (G alpha Q pathway)
IP3 will bind to calcium channel, released calcium will help DAG activate PKC

Question 10

calmodulin

Answer 10

Ca2+ binds to calcium responsive proteins
undergoes conformational change to interact w other signaling proteins

Question 11

heart muscle ach signaling

Answer 11

potassium outflow-> decreased muscle contraction

Question 12

skeletal muscle

Answer 12

influx of sodium-> increase muscle contraction

Question 13

alpha subunit g-protein termination

Answer 13

inactivates itself via GTP hydrolysis

Question 14

desensitization

Answer 14

GPCR desensitize themselves by activating GRKs
-GRKs phosphorylate intracellular domains of GPCR
-arrestin binds to phosphorylated residues on GPCR-> blocks binding and prevents from becoming reactivated

Question 15

wnt protein

Answer 15

ligan

Question 16

frizzled

Answer 16

receptor

Question 17

beta-catenin

Answer 17

when activated, binds to TF to promote transcription of genes
helps regulate development and growth

Question 18

when Wnt not bound

Answer 18

APC and GSK-3 phosphoylates beta-catenin and degrades it
no signaling, no transcription

Question 19

when Wnt bound

Answer 19

Wnt binds to frizzled, inactivates APC and GSK-3 complex
saves beta-catenin from degradation, translocate into nucleus and binds to TF

Question 20

SHH

Answer 20

ligand

Question 21

PTCH

Answer 21

receptor

Question 22

SHH not bound

Answer 22

PTCH associated with GPCR (SMO)
keeps in inactive state

Question 23

SHH bound

Answer 23

PTCH and SMO dissociate
active state
-turns on signaling cascade that leads to increased gene expression through TF (GL11)
—important during embryogenesis

Question 24

notch signaling

Answer 24

signaling for organogenesis/ neurogenesis
-binding of notch to its ligand on neighbor cell
-delta notch complex internalized by delta possessing cell
-conformational change occurs in cytoplasmic domain of notch
-cleaved domain tranlocates into nucleus

Question 25

lateral inhibition

Answer 25

cell adopts a particular fate inhibits its immediate neighbors from also adopting that fate
-occurs in neurogenesis
-medicated by notch-delta interaction

Question 26

methods of desentization

Answer 26

inactivate receptor or signaling molecule
produce inhibitory protein
internalization of receptor
downregulation of receptor

Question 27

which of the following second messengers is responsible for the release of calcium from the ER in response to G protein coupled receptor signaling?

Answer 27

IP3