G Protein Coupled Receptors II Flashcards
Which system is adenylate cyclase used in?
cAMP 2nd messenger system.
What are the steps of the cAMP 2nd messenger system?
- ligand binds to receptor, activated G protein
- alpha subunit of G protein binds to adenylate cyclase in membrane
- ATP ~> cAMP
- cAMP activated protein kinase A
- PKA activates protein, elicits response
What happens in the B2 adrenoreceptor in liver and muscles?
Epiniphrene molecule binds to receptor triggering a signalling cascade.
Glucose metabolism.
What switches signalling off?
- Agonist dissociating from receptor
- GTPase activity of Gas
- cAMP breakdown of phosphodiesterase
- Dephosphorylation of enzymes
What is the cAMP pathway activated/inactivated by?
Activated by Gas
Inactivated by Gal
What 2nd messengers can be created from membrane lipids by lipases?
- Water soluble e.g. IP2
- Hydrophobic e.g. DAG
What can GPCRs activate to generate IP3 and DAG?
PLC
What does DAG binding cause?
Dissociation of domain from active site.
What does phosphorylation of PLCb cause?
Positive feedback for GPCR signalling.
How is the cGMP 2nd messenger system different to cAMP?
Enzyme. (Guanylate cyclase).
generated from GTP ~> cGMP.
How is the message in the cGMP system encoded?
In the concentration and frequency of changes of concentration.
What is the resting cytosolic concentration of Ca2+?
Low - ~100nM.
What regulates Ca2+ influx?
Channels on the EC membrane and ligand gated channels on the ER.
What maintains Ca2+ levels in the ER?
ORAI channels gated by STIM.
What is maintaining Ca2+ levels important for?
Activation of T lymphocytes
