Cell signalling 2

What is the structure of ion channels?

4-5 subunits each with 4 membrane spanning alpha helices

Gated and open to form a pore

What are the type of ion channels?

Voltage gated

Ligand gated (extra/intra)

Mechanically gated

What is the structure of a GPCR?

single polypeptide with 7 transmembrane domains

Ligand binding domain and G-protein binding domain

How are GPCRs activated?

Ligand binds causing conformational change of receptor

activates the G-protein

alpha, beta and gamma subunits

alpha inactive with GDP

When activated alpha dissociates and activates downstream signalling

What is the function of G alpha S?

stimulates adenylyl cyclase which produces cAMP

What is the function of G alpha I?

Inhibits adenylyl cyclase so no cAMP produced

What is the function of G alpha q/11?

activates phospholipase C produce inositol triphosphate (IP3)hatW

What is the function of G beta and gamma?

Activate/inhibit ion channels

Activate kinases

What is the process followed by activation of G alpha S?

Activates adenylyl cyclase which produces cAMP from ATP

one target is protein kinase A (PKA)

this binding allows subunits of PKA to phosphorylate CREB

controls gene transcription

What is the process followed by activation of G alpha q/11?

Phospholipase C activation

produces IP3 and diacylglycerol which releases calcium in ER

diacylglycerol and calcium activate protein kinase C