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Originally published as MBoC in Press, 10.1091/mbc.E08-10-1074 on April 29, 2009

Vol. 20, Issue 12, 2991-3002, June 15, 2009

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Dual Roles for RHOA/RHO-Kinase In the Regulated Trafficking of a Voltage-sensitive Potassium Channel

Lee Stirling, Michael R. Williams, and Anthony D. Morielli

Department of Pharmacology, College of Medicine, University of Vermont, Burlington, VT 05405

Submitted October 31, 2008; Revised April 15, 2009; Accepted April 16, 2009
Monitoring Editor: David G. Drubin

Kv1.2 is a member of the Shaker family of voltage-sensitive potassium channels and contributes to regulation of membrane excitability. The electrophysiological activity of Kv1.2 undergoes tyrosine kinase-dependent suppression in a process involving RhoA. We report that RhoA elicits suppression of Kv1.2 ionic current by modulating channel endocytosis. This occurs through two distinct pathways, one clathrin-dependent and the other cholesterol-dependent. Activation of Rho kinase (ROCK) via the lysophosphatidic acid (LPA) receptor elicits clathrin-dependent Kv1.2 endocytosis and consequent attenuation of its ionic current. LPA-induced channel endocytosis is blocked by the ROCK inhibitor Y27632 or by clathrin RNA interference. In contrast, steady-state endocytosis of Kv1.2 in unstimulated cells is cholesterol dependent. Inhibition of basal ROCK signaling with Y27632 increased surface Kv1.2, an effect that persists in the presence of clathrin small interfering RNA and that is not additive to the increase in surface channel levels elicited by the cholesterol sequestering drug filipin. Temperature block experiments show that ROCK affects cholesterol-dependent trafficking by modulating the recycling of endocytosed channel back to the plasma membrane. Both receptor-stimulated and steady-state Kv1.2 trafficking modulated by RhoA/ROCK required the activation of dynamin as well as the ROCK effector Lim-kinase, indicating a key role for actin remodeling in RhoA-dependent Kv1.2 regulation.

This was published online ahead of print in MBC in Press (http://www.molbiolcell.org/cgi/doi/10.1091/mbc.E08-10-1074) on April 29, 2009.

Address correspondence to: Anthony D. Morielli (anthony.morielli{at}uvm.edu)






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