A family of kinases (phosphatidylinositol-3-kinases, PI kinases) that phosphorylate phosphatidylinositol phosphate on the 3 position. They are involved in signalling cascades downstream of many growth factor receptors, particularly receptor tyrosine kinases (RTKs). The classical form (class I) has a p110 enzymatic subunit which is regulated by p85 (p85α, p85β, p55γ, and splicing variants). p110 is recruited to the membrane and activated via the interaction of SH2 domains on the regulatory subunit which bind phosphotyrosine motifs on the stimulated RTK. An increasing family is being identified, including the PI3Kγ isoform which is activated by receptor-stimulated G proteins and recruited to the membrane by p101. Others are regulated by calcium. Most, but not all, are inhibited by wortmannin. See Akt.
Subjects: Medicine and Health.