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Flashcards in Biological Signalling: GPCR Deck (30)
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1

What does GPCR stand for?

G protein coupled receptor

2

Epinephrine is a derivative of _____

tyrosine

3

What are 3 components of heterotrimeric GPCR Signalling?

1. plasma membrane receptor with 7 TM
2. heterotrimeric guanosine nucleotide binding protein (G-protein)
3. intracellular enzyme that generates a 2nd messenger

4

What does the binding of the ligand to the beta adrenergic receptor cause?

- structural change on cytoplasmic side
- G alpha,beta,gamma bind the B receptor
- Gprotein is GDP bound inactive

5

Gprotein bound to activated receptor causes:

- GDP/GTP exchange and binding affinity
- activated G protein = change shape = kick out the Ga-GTP

6

Gas - GTP associates with

Adenylyl cyclase

7

AC catalyzes the formation of

- ATP to form cAMP

8

cAMP activates

PKA
protein kinase a
which phosphorylates cellular proteins that cause a cellular response to epinephrine

9

Where can this beta adrenergic pathway be stopped?

- Gai (inactivate/inhibitory) binds and deactivates adenylyl cyclase (cant form cAMP)
- phosphodiesterase PDE breaks down cAMP to 5'AMP

10

What does caffeine do to this pathway?

- inhibits PDE
- prevents breakdown of cAMP

11

Gs bound GDP is ____

inactive
cannot activate AC

12

Gs contact with hormone receptor (beta adrenergic receptor) causes

GTP displaces GDP bound to Gs

13

Gs bound GTP _____

- dissociates into Gsa and Gsby subunits

14

Active complex of Gs protein is ___

Gsa - GTP
- activates adenylyl cyclase

15

What do Gai proteins do?

- inhibit the formation of second messenger
- via cytoplasmic facing enzyme AC

16

What are 4 turn off mechanisms?

1. epinephrine dissociates
2. GTPase: timer that G-a subunit hydrolyses GTP (goes back to GDP)
3. PDE: cAMP broken down to 5'AMP
4. Internaliation of receptors beta adrenergic receptor is phosphorylated and internalized (endocytosis)

17

What is the first step of internalizing the epinephrine receptor to turn off epinephrine mechanism?

- phosphorylation of the b adrenergic receptor
- on serine residue of C terminus

18

What phosphorylates the beta adrenergic receptor?

bARK
- beta adrenergic receptor kinase

19

bAR forms a complex with _____

beta arrestin bARR

20

Receptor arrestin complex does what?

- enters the cell by endocytosis
- arrestin dissociates and receptor is dephosphorylated and then returns back to cell surface

21

What other G proteins are there?

Gaq

22

What does Gaq stimulate?

- PL-C enzyme (instead of AC)
- increase DAG and IP3

23

What does DAG activate?

PKC (cell growth responses)

24

What does IP3 activate?

Ca2+ released inside the cell for smooth muscle response and Ca2+dependent signalling

25

What are two types of neurotransmitters for metabotropic receptors? (GPCR)

- biogenic amines
- neuropeptides

26

List some biogenic amines:

- acetylcholine
- nicotinic receptors
- muscarinic receptors : Gai and Gaq
- Epinephrine and norepinephrine
- dopamine
- serotonin

27

What does M1-5 do?

muscarinic receptor:
- stimulates Gai and Gaq
- decreased HR and contraction
- increased smooth muscle contraction of gut (rest and digest)

28

What does epinephrine and norepinephrine do?

- opposite to M15
- a1 receptor activates Gaq and a2 receptor activates Gai
- relax smooth muscle of gut
- vasoconstriction of gut blood vessel, glucagon release
- increase blood FFA and glucose
-beta 1, 2, 3, (bAR) activates Gas:
- increased HR and contraction
- vasodilation of skeletal muscle blood vessels

29

Dopamine?

Dopamine 1 receptors activate Gas = euphoria
Dopamine 2 receptors activate Gai = motor coordination

30

How are steroid hormone receptors transported and how does it target DNA?

- carrier serum proteins
- diffuse across PM
- bind Rec (receptor protein)
- conformational change of receptor protein
- Rec binds HRE in DNA
- regulates transcription of mRNA