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Physiology Exam 4 > G-protein Linked Receptors > Flashcards

G-protein Linked Receptors Flashcards

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1
Q

G-protein-linked cell surface receptors consist of?

A

Seven-pass transmembrane proteins with extracellular domain and intracellular domain

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2
Q

G-protein-linked receptor extracellular domain contains?

A

Hormone binding site

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3
Q

G-protein-linked receptor intracellular domain contains?

A

Binding site for heterotrimeric G-protein

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4
Q

Heterotrimeric G-protein function

A

Couples receptor to targets

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5
Q

Targets of G-protein-linked receptors

A
  1. Ion channels
  2. Enzymes
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6
Q

3 subunits of heterotrimeric G-proteins

A
  1. α
  2. β
  3. γ
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7
Q

“Switched off” heterotrimeric G-protein

A

GDP and β-γ are bound to α-subunit

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8
Q

“Switched on” heterotrimeric G-protein

A

GTP is bound to α-subunit

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9
Q

Activation of heterotrimeric G-protein

A

GDP exchanged for GTP

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10
Q

α-subunit of heterotrimeric G-protein

A

Carries GTP and mediates most signaling

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11
Q

βγ-subunit of heterotrimeric G-protein

A

Signaling molecule but not very important

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12
Q

2 examples of molecular switches

A
  1. RAS (monomeric G-protein)
  2. Heterotrimeric G-proteins
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13
Q

How does α-subunit switch on and off?

A

Possesses GTPase activity to hydrolyze GTP to GDP

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14
Q

Gs

Second messenger:

Major effector:

A

cAMP increases

Protein kinase A increases

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15
Q

Gi

Second messenger:

Major effector:

A

cAMP decreases

Protein kinase A decreases

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16
Q

Gq

Second messenger:

Major effector:

A

IP3/DAG or NO/cGMP

Protein kinase C or protein kinase G

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17
Q

Gs/cAMP pathway is involved with?

A

Cardiac pacemaker in sinus node

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18
Q

If aka?

A

Funny current

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19
Q

If function

A

Drives potential toward threshold

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20
Q

ICa,L aka?

A

L-type Ca2+ current

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21
Q

ICa,L function

A

Activates at threshold and generates action potential

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22
Q

Norepinephrine is released from?

A

Sympathetic nerve fibers

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23
Q

Norepinephrine has what effect on threshold frequency?

A

Increases

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24
Q

Stimulation of If and ICa,L causes?

A

Increased threshold frequency

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25
Q

NE stands for?

A

Norepinephrine

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26
Q

How does NE initiate Gs/cAMP pathway?

A

Activates β1-adrenergic receptor

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27
Q

Activated β1-adrenergic receptor activates?

A

Gs-protein

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28
Q

What does s in Gs represent?

A

Stimulatory

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29
Q

Activated Gs-protein does?

A

Splits into αs-subunit and beta-gamma-subunit → GDP on αs-subunit replaced by GTP

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30
Q

αs-subunit stimulates?

A

Adenyly cyclase to catalyze generation of second messenger cAMP from ATP

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31
Q

cAMP stimulates?

A
  1. Channel which generates funny current If
  2. Protein kinase A (PKA)
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32
Q

PKA stands for?

A

Protein kinase A

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33
Q

PKA does what?

A

Phosphorylates channel which generates ICa,L

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34
Q

How does Gs/cAMP pathway increase HR?

A
  1. If generation by cAMP
  2. ICa,L generation by PKA
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35
Q

Termination of Gs/cAMP pathway initiated by?

A

Norepinephrine leaving the β1 receptor

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36
Q

Once NE leaves β1 receptor, what happens?

A

αs-subunit of G-protein hydolyzes GTP to GDP (inactiving itself)

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37
Q

What breaks down cAMP?

A

Phosphodiesterase

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38
Q

M2 muscarinic receptors are found in?

A

Cardiac pacemaker cells

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39
Q

α1-adrenergic receptors are found in?

A

Vascular smooth muscle cells

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40
Q

H1-histaminergic receptors are found in?

A

Vascular endothelial cells

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41
Q

How is Gi/cAMP pathway initiated?

A

Ach activates M2 muscarinic receptor

42
Q

Activated M2 muscarinic receptor activates?

A

Gi-protein

43
Q

i in Gi-protein signifies?

A

Inhibitory

44
Q

αi-subunit does what?

A

Inhibits adenylyl cyclase to generate less cAMP

45
Q

Effect of Gi/cAMP pathway on HR

A

Decreases HR

46
Q

How is termination of the Gi/cAMP pathway initiated?

A

Ach leaves receptor

47
Q

Sympathetic innervation:

Signal:

Receptor:

Effect

A
  1. NE
  2. β1 receptors
  3. If and ICa,L stimulated → increased HR
48
Q

Parasympathetic innervation

Signal:

Receptor:

Effect

A
  1. Ach
  2. M2 receptor
  3. If and ICa,L inhibited → decreased HR
49
Q

How is Gq pathway initiated?

A

NE activates α1-adrenergic receptor

50
Q

Activated α1-adrenergic receptor activates?

A

Gq-protein

51
Q

αq-subunit stimulates?

A

Phospholipase C

52
Q

Phospholipase C stimulated by αq-subunit does?

A

Catalyzes breakdown of PIP2 to IP3 and DAG

53
Q

IP3 stands for?

A

Phosphoinositol triphosphate

54
Q

DAG stands for?

A

Diacylglycerol

55
Q

PIP2 stands for?

A

Phosphoinositol diphosphate

56
Q

IP3 does what?

A

Releases Ca2+ from intracellular stores

57
Q

Ca2+ released by IP3 does what?

A
  1. Binds to CaM
  2. Initiates NO/cGMP pathway by activating NO-synthase
58
Q

CaM stands for?

A

Calmodulin

59
Q

Ca2+-CaM complex does what?

A

Activates MLCK

60
Q

MLCK stands for?

A

Myosin-light chain kinase

61
Q

Activated MLCK does what?

A

Phosphorylates MLC

62
Q

MLC stands for?

A

Myosin-light chain kinase

63
Q

Phorphorylated MLC has what?

A

Increased affinity of myosin head for actin filament (leads to contraction)

64
Q

PKC is activated by?

A

DAG and Ca2+

65
Q

PKC stands for?

A

Protein kinase C

66
Q

Activated PKC does what?

A

Phosphorylates CPI-17

67
Q

Phosphorylated CPI-17 does what?

A

Inhibits MLCP

68
Q

MLCP stands for?

A

Myosin light chain phosphatase

69
Q

Reduced activity of MLCP leads to?

A

Maintenance of MLC in phosphorylated state (contraction of smooth muscle cells)

70
Q

What initiates Gq/NO/cGMP pathway?

A

Histamine activates H1-histaminergic receptor

71
Q

β-adrenergic receptors are located in?

A

Cardiac atrial cells

72
Q

Muscarinic receptors are located in?

A

Cardiac atrial cells

73
Q

α1-adrenergic receptors are located in?

A

Vascular smooth muscle

74
Q

H1-histaminergic receptors are located in?

A

Vascular endothlial cells

75
Q

Activated H1-histaminergic receptor does what?

A

Activates Gq-protein

76
Q

Activated NO-synthase does what?

A

Generates gaseous second messenger NO

77
Q

Activated NO-synthase generates NO from?

A

Amino acid arginine

78
Q

NO stimulates?

A

Guanylyl cyclase (PKG)

79
Q

NO stimulates guanylyl cyclase to?

A

Make cGMP from GTP

80
Q

cGMP stimulates PKG to?

A

Phosphorylate proteins

ex: MYPT-1

81
Q

Phosphorylated MYPT-1 stimulates?

A

Myosin phosphatase

82
Q

NE targeted to heart in Gs/cAMP pathway

Receptor:

Major response:

A

β1-adrenergic receptor

HR and force increases

83
Q

Epinephrine targeted to arteries

Receptor:

Major response:

A

β2-adregenic receptor

Vasodilation

84
Q

NE targeted to bronchi in Gs/cAMP pathway

Receptor:

Major response:

A

β2-adrenergic

Bronchodilation

85
Q

Epinephrine targeted to muscle

Receptor:

Major response:

A

β2-adrenergic

Glycogen breakdown

86
Q

Vasopressin in Gs/cAMP pathway

Target tissue:

Receptor:

Major response:

A

Kidney

V2

Water reabsorption

87
Q

Histamine

Target tissue:

Receptor:

Major response:

A

Stomach

H2

Acid secretion

88
Q

Glucagon

Target tissue:

Receptor:

Major response:

A

Liver

G

Glycogen breakdown

89
Q

ACTH

Target tissue:

Receptor:

Major response:

A

Adrenal cortex

ACTH-R

Cortisol secretion

90
Q

TSH

Target tissue:

Receptor:

Major response:

A

Thyroid gland

TSH-R

Thyroid hormone synthesis and secretion

91
Q

Ligands which signal via Gs/cAMP pathway

A
  1. NE
  2. Epinephrine
  3. Vasopressin
  4. Histamine
  5. Glucagon
  6. ACTH
  7. TSH
92
Q

2 ligands which signal via Gi/cAMP pathway

A
  1. Acetylcholine
  2. Adrenaline
93
Q

Ach targeting heart

Receptor:

Major response:

Pathway:

A

M2

Decrease HR

Gi pathway

94
Q

Adrenaline

Target tissue:

Receptor:

Major response:

A

Neuron

α2-adrenergic

Decrease transmitter release

95
Q

Ligands which signal via Gq/IP3/DAG pathway

A
  1. NE
  2. Acetycholine
  3. Angiotensin
  4. Vasopressin
  5. Histamine
96
Q

Ach targeting bronchi

Receptor:

Major response:

Pathway:

A

M1, M3

Contraction

Gq/IP3/DAG

97
Q

Ach targeting pancreatic β-cell

Receptor:

Major response:

Pathway:

A

M1, M3

Stimulat insulin secretion

Gq/IP3/DAG pathway

98
Q

NE in Gq/IP3/DAG pathway

Targets tissue:

Receptor:

Major response

A

Arteries

α1-adrenergic

Vasoconstriction

99
Q

Angiotensin

Target tissue:

Receptor:

Major response:

A

Arteries

AT1, AT2

Vasconstriction

100
Q

Vasopressin in Gq/IP3/DAG pathway

Target tissue:

Receptor:

Major response:

A

Arteries

V1

Vasoconstriction

101
Q

Ach targeting vascular wall endothelium

Receptor:

Major response:

Pathway:

A

M3

Vasodilation

Gq/NO/cGMP pathway

102
Q

Histamin

Target tissue:

Receptor:

Major response:

A

Vascular wall endothelium

H1

Vasodilation

Physiology Exam 4 (10 decks)

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