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Cell biology > Lecture 10 > Flashcards

Lecture 10 Flashcards

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1
Q

Structure of G-protein coupled receptor

A
  • 7 transmembrane alpha helical subunits (H1-7)
  • G-protein interact with a-helices 5 and 6 (C3)
    NH3+ E1, C1, E2, C2 etc for bonds
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1
Q

Process of cell signalling

A
  1. Signal
  2. Perception
  3. Transduction
  4. Response
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2
Q

Explain what comes under the 3 principal groups of G-protein coupled receptors

A

Family A - Biological amines, Light or odorants, Peptides or chemokines, Purines, Lipids

Family B - Peptides

Family C - Biological amines, Glutamate, Ca2+

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3
Q

5 examples of biological functions mediated by 7TM receptors

A

Hormone action and secretion

Chemotaxis

Exocytosis

Senses e.g. taste, smell, vision

Embryogenesis

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4
Q

5 important human G-protein coupled receptors

A

Histamine H2 receptor - Acid secreting cells of stomach - stimulates acid secretion

Histamine H1 receptor - Smooth muscle, vascular epithelial cell - Increases vascular permeability and symptoms of allergies

Serotonin 5HT2A - Central nervous system - Synaptic transmission between neurons

Serotonin HTA1A - Central nervous system - Synaptic transmission between neurons

Angiotensin AT1 - Vascular smooth muscle cells - Constricts blood vessels, increasing blood pressure

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5
Q

What drugs treat the 5 G protein types

A

Histamine H2 receptor - Cimetidine and Ranitidine - Prevent acid stomach, treats stomach ulcers

Histamine H1 receptor - Fexofenadine and Loratadine - reduce allergy symptoms

Serotonin 5HT2A - clozapine, risperidone - treat schizophrenia

Serotonin 5HT1A - Buspirone - Treat depression and anxiety

Angiotensin AT1 - Reduce hypertension by losartan

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6
Q

Explain epinephrine

A

Hormome that binds Beta-adrenergic receptor
Fight or flight hormone - Catecholamine, adrenal glands (adrenal medula)

Increases glycogen breakdown
Increases release of fatty acids

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7
Q

cAMP pathway

A

Epinephrine binds to Beta adrenergic receptor, activating the receptor

GTP is exchanged for GDP in amplification to activate the G protein

GTP form of alpha subunit binds to adenylate cyclase which cause ATP to be converted into cAMP

Rising levels of cAMP activates protein kinase A

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8
Q

How many amino acids does epinephrine interact with on beta adrenergic receptor?

A

15 amino acids on 4 transmembrane alpha helices

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9
Q

G protein cycle

A

ON –> H2O->Pi and addition of By to alpha GDP subunit –> OFF

OFF –> GTP hydrolysis and removal of By subunit –> ON

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10
Q

Adenylate cyclase

A

2 catalytic domains

1 catalytic domain attaches 2 components each containing 6 transmembrane a helical subunits

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11
Q

What do Ga subunits have?

A

Intrinisic GTPase activity

adenylate cyclase-GTP Gas –> H2O->Pi –> adenylate cyclase-GDP Gas –> adenylate cyclase + Heterotrimeric G protein

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12
Q

Signal termination

A
  1. Dissociation
  2. Phosphorylation by GPCR kinase + binding of arrestin
  3. Endocytosis
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13
Q

How many different Ga subunits are there

A

Over 20

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14
Q

What is the stimulatory Ga subunit

A

Gas

Associated effector: adenylyl cyclase

Secondary messenger: cAMP (increased)

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15
Q

What is the inhibitory Ga subunit

A

Gai

Associated effector: Adenylyl cyclase K+ channel (GBy activates effecctor)

Secondary messenger: cAMP (decreased), Change in membrane potential

16
Q

What is the olfactory Ga subunit

A

Gaolf

Associated effector: Adenylyl cyclase

Secondary messenger: cAMP (increased)

17
Q

What is the visual Ga subunit?

A

Gat

Associated effector: cGMP phosphodiesterase

Secondary messenger: cGMP (decreased)

18
Q

How is cAMP regulated?

A

Stimulatory (Epinephrine glucagon ACTH) and inhibitory (PFE1 adenosine) hormones bind receptor

Activates heterotrimeric G proteins including Gas or Gai

GTP form of Gas or Gai bind adenylyl cyclase, activating or inhibiting production of cAMP

19
Q

What occurs when PIP2 is cleaved by phospholipase C?

A
  • Activates PKC (initiating kinase cascade)
  • Releases Ca2+ from intracellular stores
20
Q

Role of IP3 and DAG

A

IP3 and DAG are released from phospholipase C

IP3 binds to IP3-gated calcium ion channels to allow calcium ion release from endoplasmic reticulum

DAG binds to PKC (initiating kinase cascade) to allow for phosphorylation of substrates

Cell biology (22 decks)

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