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Physiology Exam 4 > G-protein Linked Receptors > Flashcards

G-protein Linked Receptors Flashcards

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
NE stands for?
Norepinephrine
26
How does NE initiate Gs/cAMP pathway?
Activates β1-adrenergic receptor
27
Activated β1-adrenergic receptor activates?
Gs-protein
28
What does _s_ in Gs represent?
Stimulatory
29
Activated Gs-protein does?
Splits into αs-subunit and beta-gamma-subunit → GDP on αs-subunit replaced by GTP
30
αs-subunit stimulates?
Adenyly cyclase to catalyze generation of second messenger cAMP from ATP
31
cAMP stimulates?
1. Channel which generates funny current If 2. Protein kinase A (PKA)
32
PKA stands for?
Protein kinase A
33
PKA does what?
Phosphorylates channel which generates ICa,L
34
How does Gs/cAMP pathway increase HR?
1. If generation by cAMP 2. ICa,L generation by PKA
35
Termination of Gs/cAMP pathway initiated by?
Norepinephrine leaving the β1 receptor
36
Once NE leaves β1 receptor, what happens?
αs-subunit of G-protein hydolyzes GTP to GDP (inactiving itself)
37
What breaks down cAMP?
Phosphodiesterase
38
M2 muscarinic receptors are found in?
Cardiac pacemaker cells
39
α1-adrenergic receptors are found in?
Vascular smooth muscle cells
40
H1-histaminergic receptors are found in?
Vascular endothelial cells
41
How is Gi/cAMP pathway initiated?
Ach activates M2 muscarinic receptor
42
Activated M2 muscarinic receptor activates?
Gi-protein
43
i in Gi-protein signifies?
Inhibitory
44
αi-subunit does what?
Inhibits adenylyl cyclase to generate less cAMP
45
Effect of Gi/cAMP pathway on HR
Decreases HR
46
How is termination of the Gi/cAMP pathway initiated?
Ach leaves receptor
47
Sympathetic innervation: Signal: Receptor: Effect
1. NE 2. β1 receptors 3. If and ICa,L stimulated → increased HR
48
Parasympathetic innervation Signal: Receptor: Effect
1. Ach 2. M2 receptor 3. If and ICa,L inhibited → decreased HR
49
How is Gq pathway initiated?
NE activates α1-adrenergic receptor
50
Activated α1-adrenergic receptor activates?
Gq-protein
51
αq-subunit stimulates?
Phospholipase C
52
Phospholipase C stimulated by αq-subunit does?
Catalyzes breakdown of PIP2 to IP3 and DAG
53
IP3 stands for?
Phosphoinositol triphosphate
54
DAG stands for?
Diacylglycerol
55
PIP2 stands for?
Phosphoinositol diphosphate
56
IP3 does what?
Releases Ca2+ from intracellular stores
57
Ca2+ released by IP3 does what?
1. **Binds to CaM** 2. Initiates NO/cGMP pathway by **activating NO-synthase**
58
CaM stands for?
Calmodulin
59
Ca2+-CaM complex does what?
Activates MLCK
60
MLCK stands for?
Myosin-light chain kinase
61
Activated MLCK does what?
Phosphorylates MLC
62
MLC stands for?
Myosin-light chain kinase
63
Phorphorylated MLC has what?
Increased affinity of myosin head for actin filament (leads to contraction)
64
PKC is activated by?
DAG and Ca2+
65
PKC stands for?
Protein kinase C
66
Activated PKC does what?
Phosphorylates CPI-17
67
Phosphorylated CPI-17 does what?
Inhibits MLCP
68
MLCP stands for?
Myosin light chain phosphatase
69
Reduced activity of MLCP leads to?
Maintenance of MLC in phosphorylated state (contraction of smooth muscle cells)
70
What initiates Gq/NO/cGMP pathway?
Histamine activates H1-histaminergic receptor
71
β-adrenergic receptors are located in?
Cardiac atrial cells
72
Muscarinic receptors are located in?
Cardiac atrial cells
73
α1-adrenergic receptors are located in?
Vascular smooth muscle
74
H1-histaminergic receptors are located in?
Vascular endothlial cells
75
Activated H1-histaminergic receptor does what?
Activates Gq-protein
76
Activated NO-synthase does what?
Generates gaseous second messenger NO
77
Activated NO-synthase generates NO from?
Amino acid arginine
78
NO stimulates?
Guanylyl cyclase (PKG)
79
NO stimulates guanylyl cyclase to?
Make cGMP from GTP
80
cGMP stimulates PKG to?
Phosphorylate proteins ex: MYPT-1
81
Phosphorylated MYPT-1 stimulates?
Myosin phosphatase
82
NE targeted to heart in Gs/cAMP pathway Receptor: Major response:
β1-adrenergic receptor HR and force increases
83
Epinephrine targeted to arteries Receptor: Major response:
β2-adregenic receptor Vasodilation
84
NE targeted to bronchi in Gs/cAMP pathway Receptor: Major response:
β2-adrenergic Bronchodilation
85
Epinephrine targeted to muscle Receptor: Major response:
β2-adrenergic Glycogen breakdown
86
Vasopressin in Gs/cAMP pathway Target tissue: Receptor: Major response:
Kidney V2 Water reabsorption
87
Histamine Target tissue: Receptor: Major response:
Stomach H2 Acid secretion
88
Glucagon Target tissue: Receptor: Major response:
Liver G Glycogen breakdown
89
ACTH Target tissue: Receptor: Major response:
Adrenal cortex ACTH-R Cortisol secretion
90
TSH Target tissue: Receptor: Major response:
Thyroid gland TSH-R Thyroid hormone synthesis and secretion
91
Ligands which signal via Gs/cAMP pathway
1. NE 2. Epinephrine 3. Vasopressin 4. Histamine 5. Glucagon 6. ACTH 7. TSH
92
2 ligands which signal via Gi/cAMP pathway
1. Acetylcholine 2. Adrenaline
93
Ach targeting heart Receptor: Major response: Pathway:
M2 Decrease HR Gi pathway
94
Adrenaline Target tissue: Receptor: Major response:
Neuron α2-adrenergic Decrease transmitter release
95
Ligands which signal via Gq/IP3/DAG pathway
1. NE 2. Acetycholine 3. Angiotensin 4. Vasopressin 5. Histamine
96
Ach targeting bronchi Receptor: Major response: Pathway:
M1, M3 Contraction Gq/IP3/DAG
97
Ach targeting pancreatic β-cell Receptor: Major response: Pathway:
M1, M3 Stimulat insulin secretion Gq/IP3/DAG pathway
98
NE in Gq/IP3/DAG pathway Targets tissue: Receptor: Major response
Arteries α1-adrenergic Vasoconstriction
99
Angiotensin Target tissue: Receptor: Major response:
Arteries AT1, AT2 Vasconstriction
100
Vasopressin in Gq/IP3/DAG pathway Target tissue: Receptor: Major response:
Arteries V1 Vasoconstriction
101
Ach targeting vascular wall endothelium Receptor: Major response: Pathway:
M3 Vasodilation Gq/NO/cGMP pathway
102
Histamin Target tissue: Receptor: Major response:
Vascular wall endothelium H1 Vasodilation

Physiology Exam 4 (10 decks)

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