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lecture 3 Flashcards

1
Q

how many molecules do GPCR ligands encompass/recognize

A

huge variety

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2
Q

examples of ligands GPCRs recognize

A

peptides, steroid hormones, smell, sight, etc.

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3
Q

how many times does GPCR pass thru membrane

A

7 times

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4
Q

describe inactive receptor

A

not bound to anything; no kinase, no enzymatic characteristics

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5
Q

describe heterotrimeric G proteins

A

not bound to receptor, hanging out in the vicinity b/c bound to each other

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6
Q

what has lipid anchors

A

2 members of heterotrimeric complex; so anchored to plasma membrane

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7
Q

why are they anchored to memrbane

A

close proximity to receptor

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8
Q

what happens when GPCR is activated

A

signaling molecule binds it

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9
Q

what does molecule binding to receptor cause

A

conformational change in G receptor allowing it to bind to heterotrimeric complex

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10
Q

what specific part of heterotrimeric complex does G receptor bind to

A

G alpha

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11
Q

what does activation of G alpha cause

A

heterotrimeric G protein to dissociate (it’s active now)

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12
Q

what happens to G protein

A

dissociates, moves along plane of plasma membrane to activate downstream proteins

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13
Q

what is brown blob

A

adenylyl cyclase (enzyme, now activated)

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14
Q

what do trimeric G proteins do

A

relay signals from GPCRs

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15
Q

where are trimeric G proteins associated

A

w/ inner leaflet of plasma membrane

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16
Q

describe inactive form of heterotrimeric G complex

A

only G alpha is bound to GDP

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17
Q

what does G alpha bound to GDP repesent

A

inactive form; GDP means off

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18
Q

where is G alpha anchored

A

plasma membrane

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19
Q

where is G gamma anchored

A

plasma membrane

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20
Q

where is beta

A

helps hold alpha and gamma together in off form

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21
Q

what happens when GPCR is activated

A

it acts like a GEF and triggers activation of its associated G protein

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22
Q

what happens when signaling molecule arrives

A

conformational change in GPCR

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23
Q

example of conformational change

A

loop on cytoplasmic face unfolds; activation dependent conformational change

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24
Q

what does activation dependent conformational change allow

A

allows it to bind and activate G alpha

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25
what is that activation
GPCR is gonna act as a guanine exchange factor
26
what is above mechanism
mechanism of activation of G alpha
27
what does GEF do
kicks off GDP, replaces it with GTP
28
what happens to alpha when activated
G alpha dissociates from beta gamma, floats freely
29
what happens to beta and gamma
remain stuck together; they are also activated
30
what happens to GPCR
remains activated; if any other copies of inactive form of heterotrimeric G protein complex its gonna bind and activate them until ligand is gone / pathway desensitized
31
where is the signaling happening at this step of pathway
at plasma membrane (b/c GPCR is in plasma membrane)
32
what does phosphorylated mean
activated
33
what do lipid anchors do
hold proteins at certain locations
34
what do some G proteins do
regulate production of cyclic AMP
35
what happens after G alpha becomes activated by exchanging GDP for GTP
it activates adenylyl cyclase
36
what does adenylyl cyclase do
converts ATP into a cyclized version called cyclic AMP
37
KNOW
adenylyl cyclase is responsible for converting ATP to cAMP
38
what does cAMP act as
second messenger; binds and activates downstream proteins to propagate signal further into cell
39
is cAMP a protein or chemical
chemical
40
how do we get rid of cAMP
phosphodiesterase; converts cyclic AMP to AMP
41
why does converting cAMP to AMP work
AMP is nolonger capable of signaling
42
what does adenylyl cyclase do
converts ATP to cAMP
43
what does cAMP do
allows signal propagation
44
what does phosphodiesterase do
destroys cAMP & turns off pathway
45
what mediates most of the effects of cyclic AMP
cyclic AMP dependent protein kinase (PKA)
46
describe cAMP molecule
small, water soluble; good at diffusing thru cytoplasm but can't cross lipid bilayers
47
what part of step is at lipid membrane
GPCR (transmembrane protein), G alpha and beta-gamma (cuz of lipid anchor) adenylyl cyclase
48
how does adenylyl cyclase meet G alpha
they're all stuck at plasma membrane so that's where they meet
49
where does cAMP go
free to diffuse into cytoplasm [departure point from membrane]
50
what is cAMP's target
protein kinase A / PKA
51
describe inactive PKA
cytoplasmic protein (not associated w/ membranes)
52
describe structure of PKA
tetramer: 2 regulatory subunits, 2 catalytic subunits
53
what do PKA regulatory subunits do
when bound to catalytic subunits, they regulate them and hold them off --> PKA off
54
describe PKA off
2 regulatory subunits bound to catalytic subunit
55
what does cAMP do when diffuses through cytoplasm
binds to catalytic subunit
56
how many molecules of cAMP needed to activate 2 copies of PKA
4 molecules of cAMP to activate 2 copies of PKA
57
describe this signaling step
reduction instead of amplification
58
give examples of amplification in steps
one GPCR activates several g alpha proteins which activate several adenylyl cyclases, create hundreds of thousands of copies of cAMP [each step gets more and mroe abundant]
59
what happens when cAMP binds to regulatory subunit
activates pKA, releases it from regulatory subunits
60
what does activated PKA do
phosphorylates downstream targets in nucleus
61
what do Gs proteins do
generation of cyclic AMP and PKA activation
62
describe transport in and out of nucleus
highly regulated, activation dependent
63
what does activation of PKA do for nucleus
represents mechanism to get signaling across nuclear pore and into nucleus & change gene transcription
64
where does PKA go when activated
enters nucleus thru nuclear pore
65
what is end goal of PKA
change gene transcription
66
how many copies of PKA enter nucleus
2 copies
67
what does PKA do when in nucleus
phosphorylates creb protein
68
what does phosphorylation of CREB do
when activated CREB initiates transcription of target gene
69
what is output of PKA pathway
change in gene regulation
70
how does PKA changing gene regulation happen
g alpha activates adenylyl cyclase, converts ATP to cAMP, activates PKA, enters in nucleus, phosphorylates CREB and activates it which activates target gene transcription
71
what was the Gs subunit dependent on
adenylyl cyclase
72
name another GPCR pathway
some G proteins signal via phospholipids
73
what happens when GPCR becomes activated
G alpha protein is activated
74
what does activated G alpha do
binds and activates phospholipase c-B
75
what does phospholipase c-B do
cleaves PI 4,5-bisphosphate into diacylglycerol and IP3 (inositol 1,4,5-trisphosphate)
76
where does diacylglycerol remain
embedded in plasma membrane
77
describe structure of diacylglycerol
head group is polar and water soluble
78
where does IP3 go
into endoplasmic reticulum
79
what G protein is for adenylyl cyclase pathway
G alpha S
80
what G protein is for phospholipase pathway
G alpha q
81
how do we distinguish these two pathways
by the specific G protein being activated
82
why is calcium kept in ER and out of cytoplasm
very potent second messenger; kinda like cAMP would just bind and activate shit
83
describe structure of IP3
polar head group of PIP2
84
what happens once IP3 when cleaved
nothing holds it to plasma membrane so it diffuses to cytoplasm
85
what does IP3 see in cytoplasm
ion gated receptor activated by ligand binding in ER membrane
86
what happens when IP3 binds channel
its a calcium channel, so when IP3 binds it floods calcium from ER into cytoplasm & triggers signaling
87
what does IP3 do w/ DAG
cooperates w/ diacylglycerol to activate protein kinase C, further downstream steps
88
what do all GPCRs activate
Galpha subunits to trigger downstream signaling
89
what can GPCRs do to target gene transcriptoin
activate cAMP production
90
what can GPCRs do for calcium
open IP3 gated channels in ER to trigger calcium signaling

bio 211 (18 decks)

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