Cell Signalling Gpcr And Rtk Flashcards
What is a GPCR
. They have seven transmembrane domain receptors(cross the membrane 7 times)
. Ligands that activate them include peptides pheromones hormones and neurotransmitters
.They have six main classes A-F
.They all have alpha beta and y subunits (heterotrimeric)
What are the predominant classes of GPCR
A: Rhodopsin family
B:Secretin / glucagon receptor
C: metabotropic /calcium sensor
What’s an example of rhodopsin class A GPCR
Rod cells (light sensitive neurons)
Receptor activates when a photon of light is absorbed
What are some processes GPCRs are involved in
Immunity , inflammation, growth and metastasis of Tumours , homeostasis, autonomic nervous system , endocrine system , behaviour and mood , smell , taste , vision.
How are GPCRs activated and deactivated
The inactive GPCR effector contains a beta y subunit attached to an alpha subunit with a GDP molecule. GTP then exchanges with GDP , this causes dissociation between Beta y subunit from alpha subunit, the GPCRs are now active. To deactivate The GPCR goes under hydrolysis where it loses a phosphate group converting the GTP back to GDP and the subunits merge together again. The GPCR is now inactive.
What are the two different types of GTPase switch proteins and what do they do
. Gaunine nucleotide exchange factors (gefs) , switch on by turning GDP into GTP via exchange
. GTPase activating proteins(GAPS), switch off by turning GTP into GDP via hydrolysis
What are the four main targets of G proteins
Adenylyl cyclase ( for cAMP)
Phospholipase C for creation of (DAG/IP3)
Rho A/Rho kinase (cytoskeletal rearrangements)
Mitogen activated protein kinases
What is the role of the phosphodiesterase
Catalyses the hydrolysis of cAMP to AMP
What happens when GDP binds again with G alpha
It first hydrolyzes GTP into GDP and +pi using the GTPas enzyme , this causes Ga to rebind with By inhibitory complex
What is the role of the protein phosphatases
They catalyses the removal of phosphates
In GPCR they allow the recycling of desensitised GPCR
What are the four different types of alpha subunits
Gas , increase cAMP
Gai ,decrease cAMP
Gaq ,increase DAG/IP3
Ga12/13 , Activates Rho
What is another role of the beta y complex
It activates ion channels for
GPCR kinases
Phospholipases
Adenylyl Cyclases
MAPk
