CB29: Cell Signalling 2 Flashcards
What does Gq alpha activate?
Phospholipase C
What does phospholipase C do?
It cleaves PIP3 into IP3 and dyacylglycerol
What does IP3 do?
Binds to calcium ion channels in the endoplasmic reticulum leading to the release of calcium ions.
Once calcium ions are released by IP3, what are they used for?
They activate protein kinase C that is bound to dyacylglycerol.
What does calmodulin do?
Regulates calcium signalling by activating enzymes.
How does the activation of CAM-kinases regulate second messengers?
CAM-kinase can phosphorylate dyacylglycerol or cleave it to arachidonic acid & it can dephosphorylate IP3 to IP2 so IP2 is desynthesised to PIP3.
What are the subunits of tyrosine kinase receptors?
Alpha & beta
What does the alpha subunit have?
A binding site for a ligand.
What does the beta subunit have?
Kinase domains with an activation loop on them.
How does the binding of a ligand to a tyrosine kinase receptor trigger signalling?
Binding of ligand to alpha subunit causes a conformational change in the receptor that brings the kinase domains close enough to phosphorylate each other into their on state.
What is the off state of kinase domains of tyrosine kinase?
The activation loops block access to their active site.
What is the on state of kinase domains of tyrosine kinase?
The activation loops are displaced so access to the active site is available.
Why do tyrosine kinase receptors exist as dimers?
So they can phosphorylate each other.
How does the insulin receptor activate a kinase cascade?
1) Once receptor has been phosphorylated, it recruits an adaptor protein.
2) The adaptor protein is phosphorylated and acts as a platform to recruit lipid kinase PI3K.
3) PI3K phosphorylates PIP2 to PIP3.
4) PIP3 recruits protein kinase AKT.
What is AKT?
A protein kinase
What is the role of AKT?
It regulates glucose uptake, metabolism & control of growth.
How is concentration of PIP3 regulated?
Lipid phosphatase PTEN reverts PIP3 to PIP2.
