PtdIns(3,4,5)P3 is a regulator of myosin-X localization and filopodia formation

Phosphatidylinositol (3,4,5)-trisphosphate [PtdIns(3,4,5)P-3] is a key regulator of cell signaling that acts by recruiting proteins to the cell membrane, such as at the leading edge during cell migration. Here, we show that PtdIns (3,4,5)P-3 plays a central role in filopodia formation via the binding of myosin-X (Myo10), a potent promoter of filopodia. We found that the second pleckstrin homology domain (Myo10-PH2) of Myo10 specifically binds to PtdIns(3,4,5)P-3, and that disruption of this binding led to impairment of filopodia and partial re-localization of Myo10 to microtubule-associated Rab7-positive endosomal vesicles. Given that the localization of Myo10 was dynamically restored to filopodia upon reinstatement of PtdIns(3,4,5)P-3-binding, our results indicate that PtdIns(3,4,5)P-3 binding to the Myo10-PH2 domain is involved in Myo10 trafficking and regulation of filopodia dynamics.