L45- Cell signalling GPCRs

Question 1

what is a GPCR?

Answer 1

receptors that sit in the cell surface can be classified into categories caled superfamilies.

Question 2

how do GPCR signal?

Answer 2

through hetrotrmeric G proteins.

Question 3

what are the classes that drugs belong to?

Answer 3

antihistamines, bronchodilators, beta blockers, opioids (pain) and migraine drugs.

Question 4

what are the 3 GPCR reptors families?

Answer 4

• rhodopsin family
• secretin/glcagon receptor family
• metabotropic glutamate receptor/calcium sensor family

Question 5

whats a orphan recptor?

Answer 5

similar to other GPCR, but theres no ligand identifie yet

Question 6

what happens when a the alpha-beta-gamma subunits is bound to GTP?

Answer 6

It is turned on

Question 7

what happens when a alpha-beta-gamma subunits is bound to GDP?

Answer 7

its turned off

Question 8

what does GTPase do?

Answer 8

switches proteins

Question 9

what is Ras?

Answer 9

a small G protein

Question 10

what do GAPs do?

Answer 10

they assist G proteins in hydrolysing GTP

Question 11

what happens when GTP binds to a-subunit?

Answer 11

alpha dissociates form beta-gamma subunits and alpha unit is now active and causes ATP to convert to cAMP to lead to an effect

Question 12

What are the differnt types of a GPCR signal transduction pathways?

Answer 12

Gi alpha- ion channel inhibition cAMP by inhibiting adenylyl cylase

• Gs alpha- increases cAMP by activating adenylyl cylase
• Gq alpha- increase DAG AND IP3
• G12,13 alpha- activates rho leads to cell migration

Question 13

do all receptor couple to all the GPCR?

Answer 13

NO, some might only couple with Gs alpha and so on

Question 14

what is bidirectional conrol of target enzyme by GPCRs?

Answer 14

nothing will happen

Question 15

what happens when the alpha- subunits is activated on the G-protein

Answer 15

many intracellular messenger molecules diffuse widelyto act on target proteins and other signalling proteins in various part of the cell

Question 16

what is GEFs?

Answer 16

a protein that activates monomeric GTPASE by stimulating the release of GDP to allow binding of GTP

Question 17

what is the whole system for GPCR?

Answer 17

• a signal will come and bind to GPCR binding site.
• after binding conformational change occurs
• due to change alpha subunit changes GDP-> GTP
• alpha subuni disccoiates from beta-gamma sub-units
• alpha subunit can now go and regulate a target protein like, adenylyl cyclase and phosopholipase C
• if the example of adenylyl cyclase is used then this will cause ATP to change to cAMP leading to increase heart rate and other stuff
• GTP is hydrolysed to GDP causing alpha unit to rebind to beta-gamma sub unit
• now ligand leaves binding site

Question 18

how many transmembrane alpha helices does a GPCR have?

Answer 18

7

Question 19

what does hetrotrimeric mean?

Answer 19

means they GPCR have 3 sub units