L45- Cell signalling GPCRs Flashcards
what is a GPCR?
receptors that sit in the cell surface can be classified into categories caled superfamilies.
how do GPCR signal?
through hetrotrmeric G proteins.
what are the classes that drugs belong to?
antihistamines, bronchodilators, beta blockers, opioids (pain) and migraine drugs.
what are the 3 GPCR reptors families?
- rhodopsin family
- secretin/glcagon receptor family
- metabotropic glutamate receptor/calcium sensor family
whats a orphan recptor?
similar to other GPCR, but theres no ligand identifie yet
what happens when a the alpha-beta-gamma subunits is bound to GTP?
It is turned on
what happens when a alpha-beta-gamma subunits is bound to GDP?
its turned off
what does GTPase do?
switches proteins
what is Ras?
a small G protein
what do GAPs do?
they assist G proteins in hydrolysing GTP
what happens when GTP binds to a-subunit?
alpha dissociates form beta-gamma subunits and alpha unit is now active and causes ATP to convert to cAMP to lead to an effect
What are the differnt types of a GPCR signal transduction pathways?
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
do all receptor couple to all the GPCR?
NO, some might only couple with Gs alpha and so on
what is bidirectional conrol of target enzyme by GPCRs?
nothing will happen
what happens when the alpha- subunits is activated on the G-protein
many intracellular messenger molecules diffuse widelyto act on target proteins and other signalling proteins in various part of the cell
what is GEFs?
a protein that activates monomeric GTPASE by stimulating the release of GDP to allow binding of GTP
what is the whole system for GPCR?
- 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
how many transmembrane alpha helices does a GPCR have?
7
what does hetrotrimeric mean?
means they GPCR have 3 sub units
