Spatial Regulation of MCAK Promotes Cell Polarization and Focal Adhesion Turnover to Drive Robust Cell Migration

The asymmetric distribution of microtubule (MT) dynamics in migrating cells is important for cell polarization, yet the underlying regulatory mechanisms remain underexplored. Here, we addressed this question by studying the role of the MT depolymerase, MCAK, in the highly persistent migration of RPE-1 cells. MCAK knockdown leads to slowed migration and poor directional movement. Fixed and live cell imaging revealed that MCAK knockdown results in excessive membrane ruffling as well as defects in cell polarization and the maintenance of a major protrusive front. Additionally, loss of MCAK increases the lifetime of focal adhesions by decreasing their disassembly rate. These defects are due in part to the loss of the spatial distribution of MCAK activity, wherein activity is higher in the trailing edge of cells compared to the leading edge. Overexpression of Rac1 has a dominant effect over MCAK activity, placing it downstream or in a parallel pathway to MCAK function in migration. Together, our data support a model that places MCAK at a key nexus of a feedback loop, in which polarized distribution of MCAK activity and subsequent differential regulation of MT dynamics contributes to cell polarity and directional migration.