Cdc42 and Cellular Polarity: Emerging Roles at the Golgi

Cdc42 belongs to the Rho family of small GTPases and plays key roles in cellular events of polarity. This role of Cdc42 has typically been attributed to its function at the plasma membrane. However, Cdc42 also exists at the Golgi complex. Here we summarize major insights that have been gathered in studying the Golgi pool of Cdc42 and propose that Golgi-localized Cdc42 enables the cell to diversify the function of Cdc42, which in some cases represents new roles and in other cases acts to complement the established roles of Cdc42 at the plasma membrane. Studies on how Cdc42 acts at the Golgi also suggest key questions to address in the future.

TrendsCdc42 exists and functions at the plasma membrane and at the Golgi.Cdc42 can replenish the pool at the plasma membrane via transport from the Golgi to the plasma membrane, which can occur either directly or indirectly by additional transit through the recycling endosome.Cdc42 can act distinctly from the pool at the plasma membrane. A major way involves Cdc42 regulating bidirectional Golgi transport, acting to prevent retrograde cargoes from being sorted into coat protein I (COPI) vesicles and also promoting the formation of COPI tubules that act in anterograde Golgi transport.Cdc42 can act in conjunction with the pool at the plasma membrane. One example is Cdc42 regulating the positioning of the Golgi complex. By coordinating this role with Cdc42 acting at the plasma membrane, surface protrusions are generated at the leading edge of migrating cells.