FIGURE 5.

The many facets of Mob regulatory function. (A) Metazoan Mob1 proteins have well-established roles as allosteric co-activators of NDR kinases and as scaffold proteins that bridge STE20 kinases (e.g., Hippo) to their phosphorylation targets, the NDR kinases. Together with other scaffolds, such as Salvador, these activation complexes are recruited to specific subcellular locations. In canonical Hippo signaling, the PP2A phosphatase of the STRIPAK complex inhibits Hippo via dephosphorylation. The most divergent fly Mob (Mob4/Phocein) is required for STRIPAK activity. (B) Cartoon of the STRIPAK complex adapted from Ribeiro et al. (2010), Zheng et al. (2017) and Tang et al. (2019). (C) Speculative Mob-dependent strategies of NDR kinase signaling output. Some classes of Mob proteins appear to bind STE20- or NDR-kinase binders, but not both. Such interactions yield Mob-bound complexes that may not allow formation of canonical activation complexes as pictured in part (A).