Cdc42 mobility and membrane flows regulate fission yeast cell shape and survival.

The delivery of new membrane from internal pools at zones of polarized secretion induces in-plane plasma membrane flows that displace slowly mobile membrane-associated proteins from the zone of secretion. However, zones of polarized secretion are themselves specified by the activity of membrane-associated polarity factors, such as the small GTPase Cdc42. Through combined modelling and experimental approaches, this work demonstrates that the fast mobility of the Cdc42 GTPase is critical to allow the establishment and maintenance of a polarity patch, which is reinforced by flow-mediated displacement of a negative regulator.