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Physiology and Pharmacology > GPCRs > Flashcards

GPCRs Flashcards

1
Q

What is signal transduction?

A

The transformation of the initial ligand binding event via intracellular signalling components to generate a response

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2
Q

What is signal amplification?

A

Refers to how the initial ligand binding event starts off a signalling cascade
where one molecule activates many molecules in turn
produces a relatively massive cellular response

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3
Q

What are some examples of stimuli that GPCRs resond to?

A

Light, odours, tastes

Ions

Neurotransmitters

Hormones

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4
Q

What is the basic structure of a GPCR?

A

Single polypeptide chain
7 transmembrane regions
N-terminus is extracellular
C-terminus is intracellular

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5
Q

Where on a GPCR can a ligand bind to it?

A

A few of the transmembrane regions

N-terminal region

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6
Q

What is the structure of a G-protein?

A

Heterotrimeric, meaning it has three different subunits

  • alpha
  • beta
  • gamma
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7
Q

What is the alpha subunit in a G-protein bound to?

A

GDP/GTP

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8
Q

What are the beta and gamma subunits in a G-protein bound to?

A

Bound to each other

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9
Q

What happens to a GPCR when a ligand binds to it?

A

It changes conformation

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10
Q

What happens to the G-protein when a ligand binds to the GPCR?

A

GTP replaces GDP on the alpha subunit

this causes the beta-gamma subunit to dissociate from the alpha subunit

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11
Q

What do the free alpha and beta-gamma subunits do?

A

Interact with effector proteins

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12
Q

What are some examples of the types of effector proteins?

A

Enzymes that generate second messengers

Ion channels

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13
Q

How is GPCR signalling terminated?

A

Alpha subunit has intrinsic GTPase
hydrolysis GTP on alpha subunit to GDP
alpha and beta-gamma subunits rejoin

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14
Q

How do GPCRs produce specific responses?

A

Specific ligand binds to specific GPCR
interacts with specific G-protein
alpha and beta-gamma subunits interact with specific effector proteins

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15
Q

What are the different ligands that bind to GPCRs?

A

Adrenaline, noradrenaline

Acetylcholine

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16
Q

What are the different types of GPCRs?

A

Alpha1

Alpha2

Beta1

Beta2

Muscarinic1

Muscarinic2

Muscarinic3

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17
Q

What are the different types of G-proteins?

A

G-alpha-s

G-alpha-i

G-alpha-q

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18
Q

What are the different types of G-proteins based on?

A

The alpha subunit

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19
Q

What does the free alpha-s subunit do?

A

Stimulates adenylyl cyclase

20
Q

What does the free alpha-i subunit do?

A

Inhibits adenylyl cyclase

21
Q

What does the free alpha-q subunit do?

A

Stimulates phospholipase C

22
Q

What does adenylyl cyclase do?

A

Catalyses the reaction

ATP —–> cAMP

23
Q

What is the structure of PKA?

A

Two regulatory subunits
Two catalytic subunits

Catalytic subunits are bound to by the regulatory subunits

24
Q

What does cAMP do?

A

Four cAMP molecules bind to the regulatory subunits of PKA - two cAMPs per regulatory subunit

25
Q

What does cAMP binding to the regulatory subunits of PKA do?

A

Causes the regulatory subunits to release the catalytic subunits
catalytic subunits are free

26
Q

What do the free catalytic subunits of PKA do?

A

Phosphorylate target proteins in the cell

27
Q

What does phospholipase C do?

A

Catalyses the reaction

PIP2 —–> IP3 + DAG

28
Q

What is PIP2? Where is it found in a cell?

A

A phospholipid

located in the plasma membrane

29
Q

What does IP3 do?

A

Binds to IP3 receptors on the endoplasmic reticulum

30
Q

What does IP3 binding to IP3 receptors do?

A

Causes the ligand-gated ion channel to open

and calcium to be released into the cytoplasm

31
Q

What does the raised cytoplasmic calcium concentration result in?

A

Activation of PKC

32
Q

What does DAG do?

A

Activates PKC

33
Q

Which types of GPCRs do adrenaline and noradrenaline bind to?

A

A1

A2

B1

B2

34
Q

Which types of GPCRs does acetylcholine bind to?

A

M1

M2

M3

35
Q

What type of G-protein is the A1 GPCR coupled to?

A

Gq

36
Q

What type of G-protein is the A2 GPCR coupled to?

A

Gi

37
Q

What type of G-protein are the B1 and B2 GPCRs coupled do?

A

Gs

38
Q

What type of G-protein is the M1 GPCR coupled to?

A

Gq

39
Q

What type of G-protein is the M2 GPCR coupled to?

A

Gi

40
Q

What type of G-protein is the M3 GPCR coupled to?

A

Gq

41
Q

What are two examples of toxins that affect GPCR function?

A

Cholera toxin

Pertussis toxin

42
Q

What type of G-protein does the cholera toxin affect?

A

Gs

43
Q

How does the cholera toxin affect Gs proteins?

A

Inhibits GTPase on alpha subunit

44
Q

What type of G-protein does the pertussis toxin affect?

A

Gi

45
Q

How does the pertussis toxin affect Gi proteins?

A

Prevents GTP replacing GDP on the alpha subunit

Physiology and Pharmacology (20 decks)

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