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Receptor and Signaling > cAMP > Flashcards

cAMP Flashcards

1
Q

GDP bound to alpha subunit of G protein

A

Inactive

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2
Q

GTP bound to alpha subunit of G protein

A

active

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3
Q

what are the four parts of alpha subunit of G protein

A

helical domain, linker, Ras like domain and switch region

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4
Q

what does helical domain of aG protein does?

A

closes over top to hold GTP in

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5
Q

What does Ras like domain of aG does?

A

where GTP binds

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6
Q

what does switch and linker region does?

A

switch region changes conformation when GTP binds and are at the interface with the receptor.

linker region connects helical and Ras like domains

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7
Q

what domain of aG interacts with the receptor

A

Ras like domain

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8
Q

what is the conformational change in aG subunit

A

the alpha helical domain swing open and GDP exchanges for GTP and alpha dissociates from beta-gamma

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9
Q

explain G protein activation and effectors pathway

A

agonist binding - G protein coupling and nucleotide exchange- activated G protein subunits regulate effector proteins - GTP hydrolysis and inactivation of Ga protein

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10
Q

Beta-gamma subunit domains

A

beta subunit gas 7 WD40 domains with 7 beta sheets with WD domains, 6 of them
gamma subunits are 12 that lay over beta subunit

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11
Q

what are effectors regulated by Beta- Gamma (3)

A

PLC. AC, many ion channels

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12
Q

where does G protein change shape when activated

A

at the region where it binds to the receptor and lets lose of receptor as well as where alpha- beta-gamma interacts

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13
Q

where are the lipid attachments in Ga and Ggamma?

A

Ga: N terminus

G-gamma: c terminus

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14
Q

adenylyl cyclase can be purified by____________

A

forsklin affinity chromatography

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15
Q

what is the structure of adenylyl cyclase?

A

12 membrane spans
N and C intracellular
2 large intracellular ATP binding loops also catalytic domains

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16
Q

what does adenylyl cyclase function

A

uses ATP binding domains to generate cAMP

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17
Q

what happens to the catalytic domains of adenylyl cyclase?

A

dimerize in anti-parallel manner

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18
Q

what all are found in the activation and inhibitory sites of adenylyl cyclase?

A

activation: Gs, fsk, beta-gamma
inhibitory: Gi, cyclase catalytic site ( ATP-cAMP)

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19
Q

what is it called when Gi and GS bind to AC at the same time?

A

Physiological antagonism because they don’t compete for a binding site, they bind at different sites

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20
Q

what does Ga bind to when active and inactive

A

when Ga inactive (Ga + GDP)- receptor and beta-gamma

when Ga active (Ga + GTP)- AC

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21
Q

cAMP pathway

A

ligand-GPCR ___ G protein + GTP____ AC____ cAMP___ activates kinases

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22
Q

protein kinase A (PKA)

A

activated by cAMP
serine-threonine kinase
phosphorylates ARG-ARG-X-Ser/Ther

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23
Q

how many (what) are the subunits of PKA

A

4 subunits
2 regulatory bound by disulfide bond and 2 catalytic not bound to each other but (psudo-phosphorylates the regulatory domains so they are stuck)

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24
Q

what is active and inactive PKA

A

R2C2 or R2/2cAMP + 2C (intermediate )- inactive

R2.4cAMP + 2C - active

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25
Q

which domain of PKA phosphorylates substrates

A

catalytic domain

26
Q

what is a common mechanism for many kinases regulatory-catalytic domain interaction?

A

pseudo-phosphorylation sites

27
Q

cAMP regulation of CREB

A

gene transcription for longer cAMP effect.
CREB is CRE binding protein
a transcription factor
phosphorylated by PKA ( catalytic domain goes in nucleus to phosphorylate CREB)

28
Q

CRE

A

cAMP Response Element region of DNA : cis regulatory sequence

29
Q

PDE

A

phosphodiesterase- needs H2O
degrade cAMP to 5’AMP
reason why cAMP has short term effect
keeps cAMP signal localized, regulated and specific

30
Q

AKAPs and used for?

A

A Kinase Anchoring Protein at nuclear membrane in this case but could be at plasma or cytoskeleton or near ion channels

anchored PKA and PDE, some get tethered to outer nuclear membrane

regulatory unit of PKA will be stuck to AKAP

  • used for localized controlled signaling
31
Q

db-cAMP and 8Br- cAMP

A

cAMP analog

nonhydrolyzable and directly activates PKA independent of R, G,AC

32
Q

IBMX

A

non-specific PDE inhibitor
increases cAMP by preventing PDE activity
PDE inhibitor: roflumilast in obstructive lung disease

33
Q

activators as tools

A

figuring out what can happen

34
Q

inhibitors as tools

A

if a step, enzyme or molecule is required

35
Q

EPAC

A 
Exchange Protein Activated cAMP
cAMP effector independent of PKA 
a GEF (guanine nucleotide exchange factor) for small G protein RAP
36
Q

crosstalk between heterotrimeric G proteins and small G protein happens as

A

EPAC- a second messenger

37
Q

similarities and difference between G protein families

A

share the same pool of beta-gamma subunits

different alpha subunit

38
Q

Gq/11

A

PLA/ PI hydrolysis and PKC activation

39
Q

what is classic signaling for Gq/11

A

PI hydrolysis

40
Q

how many secondary and third messengers does PLC/PI hydrolysis pathway give?

A

two secondary
DAG and IP3
one third
Ca

41
Q

cellular responses as a result of Gq/11

A
  1. Ca released from ER by IP3 targeting Ca channel

2. PKC phosphorylation activated by DAG and Ca

42
Q

PIP2

A

membrane anchored

hydrolyzed by phospholipase C into DAG (membrane bound) and IP3 cytoplasmic (water soluble)

43
Q

PLC

A

G protein regulated enzyme- Ga+ GTP of Gq/11 binds to PLC

44
Q

PKC

A

phospholipid- dependent protein kinase C

45
Q

How are PLC regulated

A

classic mechanism : Ga-GTP of Gq/11
Beta-gamma subunit of Gi

both producing DAG and IP3

46
Q

Beta ARK

BARK

A

Beta-adrenergic receptor kinase
controls GPCR desensitization and internalization
cytosolic enzyme with beta-gamma binding domain to move to membrane to find activated GPCR substrate

47
Q

where is the beta-gamma binding domain is on BARK

A

in the C-terminus

48
Q

how does BARK act as scavenger?

A

to bind to free beta-gamma subunit and prevents them from activating their target

49
Q

what doesn’t BARK-ct binding tell us

A

which G protein the beta-gamma came from because it binds to all beta-gamma

50
Q

Regulation of PLC

A

classical: Gq/11 Ga+ GTP
Beta-gamma GI
- Pertussis toxin : covalently ADP riboselate and irreversibly blocks R-GI coupling
- BARK binds to beta-gamma and inhibits the activity

51
Q

Adenylyl cyclase regulation by beta-gamma

A

Beta-gamma inhibition on the catalytic and inhibitory end

Beta-gamma stimulations on the activation end

52
Q

PKC

A

same as PKA, serine-threonine kinase

two second messengers need to be there to activate: DAG and Ca

53
Q

PKC vs PKA

A

PKA: receptor and catalytic domain are on separate proteins

PKC: receptor and catalytic on single protein

54
Q

PIP2___ PI3K_____PIP3

A

PI3K signaling

PIP3 in plasma membrane and another secondary messenger and recruits signals to the membrane

55
Q

PI3K regulation

A

most by receptor tyrosine kinases

gamma PI3K regulated by G protein beta-gamma subunit

56
Q

what are the secondary messengers possible from PIP2

A
  1. IP3
  2. DAG
    - both IP3 and DAG from GPCR-PLC/PI pathway
  3. PIP3: RTK and PI3K gamma isoform from G protein Beta-gamma subunit
57
Q

what can beta-gamma subunit regulate?

A
  1. Beta-gamma can stimulate, synergize with alpha Gs or inhibit
  2. Beta-gamma of Gi mainly or Gq/11 ____ PLC/PI
  3. Beta-gamma of mainly Gi regulate PI3K gamma isoform
58
Q

G12/13

A

Rho and other effectors

cytoskeleton, contraction, migration and proliferation

59
Q

best characterized effector of G12/13

A

p115RhoGEF

a guanine nucleotide exchange factor (GEF) for Ras related small G protein Rho

60
Q

What is the function of Rho

A

regulates cytoskeleton contraction and motility

heterotrimeric G proteins regulating a small Ras-family GTP switch protein

Receptor and Signaling (6 decks)

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