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Physiology > G-protein linked receptors > Flashcards

G-protein linked receptors Flashcards

1
Q

What are G-protein linked receptors?

A

7 pass transmembrane receptors

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2
Q

Which side of the G-protein coupled receptor is the hormone binding site?

A

Extracellular

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3
Q

Which side of the G-protein receptor binds the G protein?

A

INtracellular

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4
Q

What does activation of the G-protein cause?

A

GDP is exchanged for GTP

GTP causes beta-gamma subunit to dissociate

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5
Q

Which subunit (alpha) (betagamma) of the G-protein is the most active?

A

Alpha

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6
Q

Does the betagamma unit have signaling properties?

A

Yes

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7
Q

How is GTP hydrolyzed after it is bound to the G-protein?

A

Alpha unit has GTPase activity

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8
Q

What is the messenger protein for Gs? What in the function of Gs?

A

increases cAMP

Gs increases protein kinase A activity

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9
Q

What is the messenger for Gi? What is the function of Gi?

A

Decrease cAMP

decreases protein kinase A activity

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10
Q

What are the 2 messenger proteins for Gq? What is the function for each?

A

IP3/DAG - protein kinase C

NO/cGMP - protein kinase G

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11
Q

What G protein is associated with the cardiac pacemaker (sinus node)?

A

Gs & cAMP pathway

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12
Q

What is the ‘funny current’?

A

If: spontaneous current that causes action potential in heart

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13
Q

What is the Ica,l current?

A

Calcium current activates at threshold of funny current and generates AP

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14
Q

What type of receptor is the cardiac pacemaker pathway?

A

Beta-adrenergic

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15
Q

Release of norepinephrine will have what activity on heart rate?

A

Increased stimulation of If and Ica,l currents

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16
Q

Describe pathway of epinephrine binding to a G-protein coupled receptor

A 
NE binds to Beta-adrenergic receptor
Gs protein is activated 
Adenylyl cyclase binds alpha-s subunit
cAMP is produced
cAMP activates Na+ channels (If)
cAMP activates protein kinase A
Protein kinase A activates Ca+ channel (Ica,l)
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17
Q

What causes cAMP to be down regulated and the channels to close?

A

Ne leaves Beta-adrenergic receptor
Gs protein self-hydrolyzes GTP to GDP

Betagamma subunit associates again

Phosphodiesterase breaks down cAMP
Na+ channel is closed
Phosphatase takes phosphate off of Ca+ channels

18
Q

What effect does Acetylcholine have on heart rate?

A

Gi protein inhibits If (funny current) and Ica,l (action potential)

19
Q

Describe pathway of acetylcholine binding to G-protein receptor

A

ACh binds to M2 muscarinic receptor

GTP replaces GDP and betagamma unit dissociates

Adenylyl cyclase binds to alpha-i subunit
cAMP is downregulated

Na+ channels do not open (If)
Lack of protein kinase A to phosphorylate Ca+ channels

20
Q

Describe pathway of epinephrine binding to G-protein receptor in vascular smooth muscle to cause contraction

A

NE binds to alpha-1 adrenergic receptor
Phospholipase C binds to alpha-q subunit

PIP2 associates with Phospholipase C to produce DAG & IP3

IP3 opens Ca+ channels
Ca+ binds to Calmodulin-myosin light chain kinase complex

DAG activates protein kinase C
Protein kinase C phosphorylates CPI-17
CPI-17 inhibits myosin light chain phosphatase so phosphorylated myosin retains affinity for actin binding site

21
Q

How is Gq in smooth muscle down-regulated to cause relaxation?

A

NE leaves Gq receptor
alpha-q subunit hydrolyzes GTP to GDP

IP3 and DAG are broken down

Phosphatases dephosphorylate CPI-17 which upregulates myosin light chain phosphatase

MLCP dephosphorylates MLC which decreases myosin’s affinity for actin

22
Q

Describe the histamine G-protein pathway

A

Histamine binds to H1-histaminergic receptor
Phospholipase C binds to alpha-q subunit

PIP2 is broken to IP3 and DAG by phospholipase C

IP3 opens Ca+ channel
Ca+ binds to Nitric oxide synthase

NOS produces NO from arginine

NO stimulates guanylyl cyclase to produce cGMP from GTP

cGMP activates protein kinase G which phosphorylates myosin phosphatase target 1

MYPT-1 produces myosin phosphatase

23
Q

What is the big difference between Gq/NO and Gq/NE

A

IP3 causes relaxation in Gq/NO

DAG does not activate protein kinase C in Gq/NO
so no CPI-17 during Gq/NO

Gq/NE causes contraction
Gq/NO causes vasodilation

24
Q

How is histamine down-regluated?

A

Histamine leaves H1-histaminergic receptor

alpha-q subunit hydrolyzes GTP to GDP

IP3, DAG are broken down

NO breaks down

cGMP is broken down by phosphodiesterases

Phosphattases dephosphorylate Myosin phosphatase target 1

25
Q

Name G-protein receptor & type and action for norepinephrine in the heart

A

Gs, B1-adrenergic, increase heart rate

26
Q

Name G-protein receptor & typeand action for epinephrine in the arteries

A

Gs, B2-adrenergic, vasodilation

27
Q

Name G-protein receptor & type and action for norepinephrine in the bronchi

A

Gs, B2-adrenergic, bronchiodilation

28
Q

Name G-protein receptor & type and action for epinephrine in the muscle

A

Gs, B2-adrenergic, glycogen breakdown

29
Q

Name G-protein receptor & type and action for vasopressin in the kidney

A

Gs, V2, water reabsorption

30
Q

Name G-protein receptor & type and action for histamine in the stomach

A

Gs, H2, Acid secretion

31
Q

Name G-protein receptor & type and action for glucagon in the liver

A

Gs, G, glycogen breakdown

32
Q

Name G-protein receptor & type and action for ACTH in the adrenal cortex

A

Gs, ACTH-Receptor, Cortisol secretion

33
Q

Name G-protein receptor & type and action for Thyroid stimulating hormone in the heart

A

Gs, TSH-Receptor, thyroid hormone synthesis & secretion

34
Q

Name G-protein receptor & type and action for acetylcholine in the heart

A

Gi, M2, decreased heart rate

35
Q

Name G-protein receptor & type and action for adrenaline in the neuron

A

Gi, A2-adrenergic, decrease transmitter release

36
Q

Name G-protein receptor & type and action for norepinephrine in the arteries (Gq/IP3)

A

Gq-IP3, A1-adrenergic, vasoconstriction

37
Q

Name G-protein receptor & type and action for acetylcholine in the bronchi (Gq-IP3)

A

Gq-IP3, M1, M3, contraction

38
Q

Name G-protein receptor & type and action for acetylcholine in the pancreas

A

Gq-IP3, M1, M3, stimulate insulin secretion

39
Q

Name G-protein receptor & type and action for Angiotensin in the arteries

A

Gq-IP3, AT1, AT2, Vasoconstriction

40
Q

Name G-protein receptor & type and action for vasopressin in the arteries

A

Gq-IP3, V1, Vasoconstriction

41
Q

Name G-protein receptor & type and action for acetylcholine in the vascular wall epithelium

A

Gq-NO, M3, vasodilation

42
Q

Name G-protein receptor & type and action for histamine in the vascular wall epithelium

A

Gq-NO, H1, Vasodilation

Physiology (45 decks)

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