FIG 9.

Role of Bem4p in regulating the filamentous-growth pathway. Under nutrient-limiting conditions, Msb2p is activated by processing and release of the inhibitory extracellular domain by the protease Yps1p (36). Activated Msb2p and Sho1p function through Bem4p, which binds to the PH domain of Cdc24p to relieve autoinhibition. Bem4p interacts with Cdc42p and Ste11p and functions in a complex with Kss1p (dashed arrow), to further regulate the filamentous-growth pathway. Although not shown, Cdc42p is at the PM, the PM sensor Opy2p recruits Ste50p-Ste11p to the PM (37, 158, 159), activated Msb2p associates preferentially with GTP-Cdc42p (26), and Sho1p associates with Cdc24p, Ste20p, and Ste11p (100, 112).