Type I Phosphatidylinositol Phosphate Kinase Beta Regulates Focal Adhesion Disassembly by Promoting β1 Integrin Endocytosis

Abstract

Cell migration requires the regulated disassembly of focal adhesions, but the underlying mechanisms remain poorly defined. We have previously shown that focal adhesion disassembly requires the dynamin 2- and clathrin-dependent endocytosis of ligand-activated β1 integrins. Here, we identify type I phosphatidylinositol phosphate kinase beta (PIPKIβ), an enzyme that generates phosphatidylinositol-4,5-bisphosphate (PI4,5P₂), as a key regulator of this process. We found that knockdown of PIPKIβ by RNA interference blocks the internalization of active β1 integrins and impairs focal adhesion turnover and cell migration. These defects are caused by the failure to target the endocytic machinery, including clathrin adaptors and dynamin 2, to focal adhesion sites. As a consequence, depletion of PIPKIβ blocks clathrin assembly at adhesion plaques and prevents complex formation between dynamin 2 and focal adhesion kinase (FAK), a critical step in focal adhesion turnover. Together, our findings identify PIPKIβ as a novel regulator of focal adhesion disassembly and suggest that PIPKIβ spatially regulates integrin endocytosis at adhesion sites to control cell migration.

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Articles of Significant Interest Selected from This Issue by the Editors

We thank Mark McNiven, Sandra L. Schmid, Irina N. Kaverina, and Vic Small for the generous gifts of antibodies and plasmids and Jim Norman and Bernard Wehrle-Haller for reagents and discussion.

This work was supported by grants from the Dan Duncan Cancer Pilot Fund (J.K.) and the National Institutes of Health (GM068098 [J.K.], CA116097 [P.Z.], and HL077187 [M.E.D.]).