Signaling by distinct classes of phosphoinositide 3-kinases

Many signaling pathways converge on and regulate phosphoinositide 3-kinase (PI3K) enzymes whose inositol lipid products are key mediators of intracell ular signaling. Different PI3K isoforms generate specific lipids that bind to FYVE and pleckstrin homology (PH) domains in a variety of proteins, affe cting their localization, conformation, and activities. Here we review the activation mechanisms of the different types of PI3Ks and their downstream actions, with focus on the PI3Ks that are acutely triggered by extracellula r stimulation. (C) 1999 Academic Press.