Cyclical Phosphorylation of LRAP35a and Its Binder CLASP2 by GSK3β and CK1δ Regulates EB1-Dependent MT Dynamics in Cell Migration

Abstract

Mammalian cell cytoskeletal reorganization for efficient directional movement requires tight coordination of actomyosin and microtubule networks. Here we show that LRAP35a potentiated microtubule stabilization by promoting CLASP2/EB1 interaction besides MRCK/MYO18A complex formation for retrograde actin flow. The alternate regulation of these two networks by LRAP35a was tightly regulated by a series of phosphorylation events that dictated its specificity. Sequential phosphorylation of LRAP35a by PKA and GSK3β initiated the association of LRAP35a with CLASP2, while subsequent binding and further phosphorylation by CK1δ induced their dissociation which would facilitate LRAP35a/MRCK association in driving lamellar actomyosin flow. Importantly, microtubule dynamics was directly moderated by CK1δ activity on CLASP2 to regulate GSK3β phosphorylation of the SxIP motifs that block EB1 binding, an event countered by LRAP35a interaction and its competition for CK1δ activity. This study thus reveals an essential role for LRAP35a in coordinating lamellar contractility and microtubule polarization in cell migration.