New functions for PI3K in the control of cell division.

Although cell lipids were initially envisioned as structural components of the cell, their essential contribution to initiation and regulation of cell responses is now clearly established. Among the different lipids that regulate cell responses, those produced by class I phosphoinositide 3-kinase (PI3K), phosphatidylinositol (3,4)P(2) (PIP(2)) and phosphatidylinositol (3,4,5)P(3) (PIP(3)), have concentrated much attention in recent years. PIP(2) and PIP(3) are involved in cell division and survival control, and mutations in the PI3K pathway are linked to autoimmunity and cancer. Here we discuss two novel observations: a PI3K function in the late-G(1) phase of the cell cycle and the contribution of the p85 PI3K regulatory subunit in the control of cytokinesis.