PI 3-Kinase

Question

PI 3-kinase ...
A) is a membrane-associated tyrosine kinase.
B) activates PDK1 by phosphorylating a serine residue on the protein.
C) is counteracted by PTEN phosphatase.
D) is only known to be activated by receptor tyrosine kinases.
E) inhibits Akt.

Accepted Answer

The plasma-membrane-bound PI 3-kinase principally phosphorylates inositol phospholipids rather than proteins. It can be activated downstream of receptor tyrosine kinases or G-protein-coupled receptors, and generates docking sites for various signaling proteins. PTEN phosphatase counteracts PI 3-kinase by dephosphorylating the 3 position of the inositol ring.