MOB4 (phocein) is a conserved member of the MOB protein family that functions as a core component of striatin-interacting phosphatase and kinase (STRIPAK) complexes. These multisubunit assemblies integrate cellular signals by regulating protein phosphorylation through PP2A and coordinate multiple signaling pathways including Hippo, MAPK, and cytoskeletal remodeling. Unlike MOB1, which suppresses YAP1 through LATS kinases, MOB4 activates YAP1 in a phosphorylation-dependent manner 1. The cryo-EM structure of human STRIPAK reveals MOB4 as a single-copy subunit within a complex scaffolded by four copies of STRN3 2. MOB4 localizes to the Golgi apparatus and cytoplasm 3 and plays critical roles in spermatogenesis, where it regulates axonemal structure and sperm individualization through STRIPAK-mediated cytoskeletal control 4. In skeletal muscle, MOB4 coordinates myofibril assembly by interacting with the chaperonin TRiC to control actin and tubulin biogenesis 5. During collective cell migration, MOB4 relocalizes to the leading edge and maintains migration orientation through YAP1 activation 6. In pancreatic cancer, elevated MST4-MOB4 complex expression promotes oncogenic YAP activity by disrupting the tumor-suppressive MST1-MOB1 complex, suggesting MOB4 as a potential therapeutic target in this context 1.