MOB4 (MOB family member 4, phocein) is a core component of the striatin-interacting phosphatase and kinase (STRIPAK) complex, which functions as a noncanonical protein phosphatase 2A (PP2A) assembly 1. The STRIPAK complex contains four copies of STRN3 regulatory subunits linked by an elongated homotetrameric scaffold, with MOB4 serving as a critical structural component 1. MOB4 plays essential roles in multiple cellular processes through STRIPAK-mediated regulation. In spermatogenesis, MOB4 is required for proper axonemal structure and sperm individualization, with its loss leading to male sterility due to defective microtubule organization 2. MOB4 coordinates myofibril and microtubule network growth by interacting with the actin-folding chaperonin TRiC to control actin biogenesis 3. In cancer biology, MOB4 forms complexes with MST4 kinase that disrupt tumor-suppressive MST1-MOB1 complexes, promoting oncogenic YAP activity in pancreatic cancer 4. MOB4 also regulates collective cell migration by controlling YAP1 activation and migration orientation 5. The protein's function appears evolutionarily conserved, as human MOB4 can rescue Drosophila phenotypes 2, though specific regulatory mechanisms may vary between species 6.