Session 2: Intracellular Signalling Pathways Flashcards
Define an agonist ligand.
Binds to a receptor and activates it
Define and antagonist ligand.
Binds to a receptor but does not activate it (blocks the effects of agonists at the receptor)
Name 4 common features of GPCRs.
- Single polypeptide chain
- 7 transmembrane spanning regions (7TM)
- Extracellular N terminal
- Intracellular C terminal
What results from a ligand binding to a GPCR
Conformational change
How many subunits are G proteins made of?
3 (alpha unit and a beta-gamma unit)
How does the GPCR-G protein interaction activate the G protein?
Causes GTP to exchange for GDP on the alpha subunit which then dissociate. These are now free to interact with secondary messenger proteins.
Once dissociated, how do the alpha and beta-gamma subunits of a G protein reform an inactive heterotrimetric complex?
The GTPase hydrolysises the GTP back to GDP
If adrenaline binds to a beta adrenoceptor which G protein alpha subunit is coded for and what is its consequence?
Gs (stimulatory) increase in adenylyl cyclase
What is the affect of cholera toxin (CTx)?
Gs cannot be switched off
What is the effect of pertussis toxin (PTx)?
Gi- can’t be switched on
What is adenylyl cyclase used to convert?
Convert ATP into cyclic AMP
How does cyclic AMP continue the cascade?
Catalytic subunits phosphorylase target proteins (PKA- protein kinase reactions)
What is phospholipase C used to convert?
PIP2 to IP3 and DAG
Name 2 calcium ATPases
- PMCA
2. SERCA
Name once calcium transporter mechanism.
Na+/Ca2+ exchanger (NCX)
