Membrane depolarization of smooth muscle cells (myocytes) in the small arteries that regulate regional organ blood flow leads to vasoconstriction. Membrane depolarization also activates large-conductance calcium (Ca)-activated potassium (BK) channels， which limits Ca channel activity that promotes vasoconstriction， thus leading to vasodilation. We showed that in human and rat arterial myocytes， membrane depolarization rapidly increased the cell surface abundance of auxiliary BK β1 subunits but not that of the pore-forming BKα channels. Membrane depolarization stimulated voltage-dependent Ca channels， leading to Ca influx and the activation of Rho kinase (ROCK) 1 and 2. ROCK1/2-mediated activation of R... More
Membrane depolarization of smooth muscle cells (myocytes) in the small arteries that regulate regional organ blood flow leads to vasoconstriction. Membrane depolarization also activates large-conductance calcium (Ca)-activated potassium (BK) channels， which limits Ca channel activity that promotes vasoconstriction， thus leading to vasodilation. We showed that in human and rat arterial myocytes， membrane depolarization rapidly increased the cell surface abundance of auxiliary BK β1 subunits but not that of the pore-forming BKα channels. Membrane depolarization stimulated voltage-dependent Ca channels， leading to Ca influx and the activation of Rho kinase (ROCK) 1 and 2. ROCK1/2-mediated activation of Rab11A promoted the delivery of β1 subunits to the plasma membrane by Rab11A-positive recycling endosomes. These additional β1 subunits associated with BKα channels already at the plasma membrane， leading to an increase in apparent Ca sensitivity and activation of the channels in pressurized arterial myocytes and vasodilation. Thus， membrane depolarization activates BK channels through stimulation of ROCK- and Rab11A-dependent trafficking of β1 subunits to the surface of arterial myocytes.
