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Receptor and Signaling > cAMP > Flashcards

cAMP Flashcards

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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
which domain of PKA phosphorylates substrates
catalytic domain
26
what is a common mechanism for many kinases regulatory-catalytic domain interaction?
pseudo-phosphorylation sites
27
cAMP regulation of CREB
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
CRE
cAMP Response Element region of DNA : cis regulatory sequence
29
PDE
phosphodiesterase- needs H2O degrade cAMP to 5'AMP reason why cAMP has short term effect keeps cAMP signal localized, regulated and specific
30
AKAPs and used for?
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
db-cAMP and 8Br- cAMP
cAMP analog | nonhydrolyzable and directly activates PKA independent of R, G,AC
32
IBMX
non-specific PDE inhibitor increases cAMP by preventing PDE activity PDE inhibitor: roflumilast in obstructive lung disease
33
activators as tools
figuring out what can happen
34
inhibitors as tools
if a step, enzyme or molecule is required
35
EPAC
``` Exchange Protein Activated cAMP cAMP effector independent of PKA a GEF (guanine nucleotide exchange factor) for small G protein RAP ```
36
crosstalk between heterotrimeric G proteins and small G protein happens as
EPAC- a second messenger
37
similarities and difference between G protein families
share the same pool of beta-gamma subunits | different alpha subunit
38
Gq/11
PLA/ PI hydrolysis and PKC activation
39
what is classic signaling for Gq/11
PI hydrolysis
40
how many secondary and third messengers does PLC/PI hydrolysis pathway give?
two secondary DAG and IP3 one third Ca
41
cellular responses as a result of Gq/11
1. Ca released from ER by IP3 targeting Ca channel | 2. PKC phosphorylation activated by DAG and Ca
42
PIP2
membrane anchored | hydrolyzed by phospholipase C into DAG (membrane bound) and IP3 cytoplasmic (water soluble)
43
PLC
G protein regulated enzyme- Ga+ GTP of Gq/11 binds to PLC
44
PKC
phospholipid- dependent protein kinase C
45
How are PLC regulated
classic mechanism : Ga-GTP of Gq/11 Beta-gamma subunit of Gi both producing DAG and IP3
46
Beta ARK | BARK
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
where is the beta-gamma binding domain is on BARK
in the C-terminus
48
how does BARK act as scavenger?
to bind to free beta-gamma subunit and prevents them from activating their target
49
what doesn't BARK-ct binding tell us
which G protein the beta-gamma came from because it binds to all beta-gamma
50
Regulation of PLC
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
Adenylyl cyclase regulation by beta-gamma
Beta-gamma inhibition on the catalytic and inhibitory end | Beta-gamma stimulations on the activation end
52
PKC
same as PKA, serine-threonine kinase | two second messengers need to be there to activate: DAG and Ca
53
PKC vs PKA
PKA: receptor and catalytic domain are on separate proteins PKC: receptor and catalytic on single protein
54
PIP2___ PI3K_____PIP3
PI3K signaling | PIP3 in plasma membrane and another secondary messenger and recruits signals to the membrane
55
PI3K regulation
most by receptor tyrosine kinases | gamma PI3K regulated by G protein beta-gamma subunit
56
what are the secondary messengers possible from PIP2
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
what can beta-gamma subunit regulate?
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
G12/13
Rho and other effectors | cytoskeleton, contraction, migration and proliferation
59
best characterized effector of G12/13
p115RhoGEF | a guanine nucleotide exchange factor (GEF) for Ras related small G protein Rho
60
What is the function of Rho
regulates cytoskeleton contraction and motility | heterotrimeric G proteins regulating a small Ras-family GTP switch protein

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