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PHA112 > Receptor & G Proteins > Flashcards

Receptor & G Proteins Flashcards

1
Q

define a superfamily?

A

group of receptors having similar bass structures and mechanism of signal transduction

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2
Q

what are the 4 superfamilies?

A
  • G protein-coupled receptors (GPCRs)
  • ligand gates ion channels (LGICs)
  • tyrosine kinase-linked receptors
  • steroid receptors (nuclear receptors)
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3
Q

what are the largest family of cell surface receptors?

A

GPCRs

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4
Q

what do GPCRs mediate?

A

cellular responses to big diversity of signalling molecules

inc:
- hormones
- proteins
- neurotransmitters

same ligand can activate many diff fam members to produce effect

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5
Q

what is the location and signal transduction mechanism of the M1 receptor?

A

nerves

inc IP3, DAG cascade

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6
Q

what is the location and signal transduction mechanism of the M2 receptor?

A

heart, nerves

dec cAMP prod, activation K+ channels, inhibition Ca2+ channels

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7
Q

what is the location and signal transduction mechanism of the M3 receptor?

A

glands, smooth muscle, endothelium

inc IP3, DAG cascade

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8
Q

what is the location and signal transduction mechanism of the M4 receptor?

A

CNS

dec cAMP prod, activation K+ channels

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9
Q

what is the location and signal transduction mechanism of the M5 receptor?

A

CNS

inc IP3, DAG cascade

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10
Q

where are muscarinic receptors located?

A

peripheral tissues and CNS

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11
Q

what are the 5 subtypes of muscarinic receptors?

A

M1, M2, M3, M4, M5

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12
Q

what are M1, M3 and M5 coupled to?

A

Gq

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13
Q

what are M2 and M4 coupled to?

A

Gi

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14
Q

what do Gq coupled receptors hydrolyse?

A

PIP2

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15
Q

what do Gi coupled receptors negatively regulate?

A

adenylyl cyclase + decrease cAMP production

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16
Q

where are M1, M3 and M4 located and what do they mediate?

A

cerebral cortex + hippocampus

mediate effects of ACh on learning + memory

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17
Q

what do M1 and M4 occur in and what can they also mediate?

A

striatum

cholinergic signalling in extrapyramidal motor circuits

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18
Q

where is M2 concentrated in and what does it act as?

A

basal forebrain

autoreceptors to control ACh synthesis + release

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19
Q

what is the location, structure and signal transduction mechanism of the Nm receptor?

A

skeletal neuromuscular junction

pentameric (2-alpha-beta-delta-gamma)

Na+ depolarising ion channel

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20
Q

what is the location, structure and signal transduction mechanism of the Nn receptor?

A

post-synaptic cell bodies, dendrites

alpha + beta subunits only usually as 2-alpha-3beta

Na+ depolarising ion channel

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21
Q

where are nicotinic receptors located?

A

NMJ , autonomic ganglia, CNS

22
Q

what superfamily are the nicotinic receptors part of?

23
Q

what does the activation of nicotinic receptors lead to?

A

influx of Na+ ions

24
Q

how many subunits are nicotinic receptors composed of?

25
where are the alpha1 and beta1 subunits located?
muscle
26
what stoichiometry ratio are neuronal nACHR's composed of (alpha to beta)?
2:3
27
what can homomeric receptors (alpha7) form?
a channel
28
alpha-adrenoreceptors alpha1 (alpha1A, alpha1B, alpha1D)
potency order: NA > Ad location: post-junctional effector organs function: smooth muscle contraction transduction: inc IP3, DAG agonist: phenylephrine antagonist: prazosin
29
alpha-adrenoreceptors alpha2 (alpha2A, alpha2B, alpha2C)
potency order: Ad > NA location: pre-synaptic nerve endings, post synaptic brain, blood vessels function: inhibition transmitter release, dec sympathetic outflow transduction: dec cAMP (Ca2+) agonist: clonidine antagonist: yohimbine
30
beta-adrenoreceptors beta1
potency order: Iso > NA > Ad location: heart, adipose tissue, JG cell kidney transduction: inc cAMP agonist: dobutamine antagonist: atenolol
31
beta-adrenoreceptors beta2
potency order: Iso > Ad > NA location: bronchi, blood vessels, uterus transduction: inc cAMP agonist: salbutamol antagonist: ICI118551
32
dopamine receptors D1 - 1 and 5
signal transduction: inc cAMP effect: post-synaptic inhibition
33
dopamin receptors D2 - 2,3,4,
signal transduction: dec cAMP effect: pre + post synaptic inhibition, stimulation/inhibition of hormone release
34
where do GPCRs occur, how do they respond and what does their single polypeptide chain have?
cell membrane respond in seconds 7-transmembrane helices
35
what does the tail GPCRs consist of?
serine + threonine residues that = phosphorylated
36
what does the intracellular loop occur between?
V and VI transmembrane domains
37
what are the heterotrimeric GTP-binding proteins (G proteins) composed of?
alpha, beta and gamma polypeptide chains
38
what do both the alpha and gamma subunits have?
lipid molecules that help bind them to plasma membrane
39
the alpha subunit has … bound
GDP
40
heterotrimeric GTP binding proteins are ….. and they function as … that can flip between 2 states
GTPases molecular switches
41
what are the 2 states?
active when GTP bound inactive when GDP bound
42
describe the on and off switching?
- extracellular ligand binds to G protein linked receptor - receptor changes conformation - —> rel of GDP + replacement with GTP - switch turned off when G protein hydrolyses own bound GTP - converting it back to GDP
43
the GTP binding causes a conformational change in the surface of alpha subunit what does this cause the release of?
beta-gamma dimer allows alpha subunit to interact with target proteins alpha subunit = GTPase + hydrolyses GTP to GDP then reassociates with beta-gamma complex
44
GTPase activity of the alpha subunit is greatly enhanced by binding of second protein called a ...
regulator of g-protein signalling (RGS)
45
what do RGS proteins act as?
alpha subunit specific GTPase activating proteins (GAPs) play imp role in shutting off g-protein mediated response
46
Gs protein
alphaS ``` activates AC (inc cAMP) activates Ca2+ channels ```
47
Gi protein
alphaI ``` inhibits AC (dec cAMP) activates K+ channels ```
48
Gq protein
alphaQ activates PLC-beta turnover (inc Ca2+)
49
Go protein
alphaO activates K+ channels inactivates Ca2+ channels
50
Gt protein
alphaT activates cGMP phosphodiesterase in rod photoreceptors
51
Golf protein
alphaOLF activates AC in olfactory system
52
what are the 2 major pathways by which GPCRs generate small intracellular mediators?
- binding of extracellular ligand -> alters conformation of cytoplasmic domain of receptor - cAMP pathway -> enzyme directly produces cAMP - enzyme produces inositol triphosphate that rel Ca2+ from ER

PHA112 (37 decks)

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