Temporal and spatial regulation of phosphoinositide signaling mediates cytokinesis

Polarity is a prominent feature of both chemotaxis and cytokinesis. In chemotaxis, polarity is established by local accumulation of PI(3,4,5)P-3 at the cell's leading edge, achieved through temporal and spatial regulation of PI3 kinases and the tumor suppressor, PTEN. We find that as migrating D. discoideum cells round up to enter cytokinesis, PI(3,4,5)P-3 signaling is uniformly suppressed. Then, as the spindle and cell elongate, PI3 kinases and PTEN move to and function at the poles and furrow, respectively. Cell lines lacking both of these enzymatic activities fail to modulate PI(3,4,5)P-3 levels, are defective in cytokinesis, and cannot divide in suspension. The cells continue to grow and duplicate their nuclei, generating large multinucleate cells. Furrows that fail to ingress between nuclei are unable to stably accumulate myosin filaments or suppress actin-filled ruffles. We propose that phosphoinositide-linked circuits, similar to those that bring about asymmetry during cell migration, also regulate polarity in cytokinesis.