Voltage-dependent activation of Rac1 by Na_v 1.5 channels promotes cell migration.

Ion channels can regulate the plasma membrane potential (V_m ) and cell migration as a result of altered ion flux. However, the mechanism by which V_m regulates motility remains unclear. Here, we show that the Na_v 1.5 sodium channel carries persistent inward Na⁺ current which depolarizes the resting V_m at the timescale of minutes. This Na_v 1.5-dependent V_m depolarization increases Rac1 colocalization with phosphatidylserine, to which it is anchored at the leading edge of migrating cells, promoting Rac1 activation. A genetically encoded FRET biosensor of Rac1 activation shows that depolarization-induced Rac1 activation results in acquisition of a motile phenotype. By identifying Na_v 1.5-mediated V_m depolarization as a regulator of Rac1 activation, we link ionic and electrical signaling at the plasma membrane to small GTPase-dependent cytoskeletal reorganization and cellular migration. We uncover a novel and unexpected mechanism for Rac1 activation, which fine tunes cell migration in response to ionic and/or electric field changes in the local microenvironment.

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