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Am J Physiol Renal Physiol 295: F380-F387, 2008. First published May 7, 2008; doi:10.1152/ajprenal.00598.2007
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MiRP3 acts as an accessory subunit with the BK potassium channel

Daniel I. Levy,1 Sherry Wanderling,1 Daniel Biemesderfer,2 and Steve A. N. Goldstein3,4

Departments of 1Medicine and 3Pediatrics, and 4Institute for Molecular Pediatric Sciences, Biological Sciences Division, University of Chicago, Chicago, Illinois; and 2Department of Internal Medicine, School of Medicine, Yale University, New Haven, Connecticut

Submitted 18 December 2007 ; accepted in final form 2 May 2008

MinK-related peptides (MiRPs) are single-span membrane proteins that assemble with specific voltage-gated K+ (Kv) channel {alpha}-subunits to establish gating kinetics, unitary conductance, expression level, and pharmacology of the mixed complex. MiRP3 (encoded by the KCNE4 gene) has been shown to alter the behavior of some Kv {alpha}-subunits in vitro but its natural partners and physiologic functions are unknown. Seeking in vivo partners for MiRP3, immunohistochemistry was used to localize its expression to a unique subcellular site, the apical membrane of renal intercalated cells, where one potassium channel type has been recorded, the calcium- and voltage-gated channel BK. Overlapping staining of these two proteins was found in rabbit intercalated cells, and MiRP3 and BK subunits expressed in tissue culture cells were found to form detergent-stable complexes. Electrophysiologic and biochemical evaluation showed MiRP3 to act on BK to reduce current density in two fashions: shifting the current-voltage relationship to more depolarized voltages in a calcium-dependent fashion (~10 mV at normal intracellular calcium levels) and accelerating degradation of MiRP3-BK complexes. The findings suggest a role for MiRP3 modulation of BK-dependent urinary potassium excretion.

KCNE4; KCNMA1; MaxiK; slo; intercalated cells


Address for reprint requests and other correspondence: S. A. N. Goldstein or D. I. Levy, Univ. of Chicago, Section of Nephrology, MC5100, 5841 S. Maryland Ave., Chicago, IL 60637-1447 (e-mail: sangoldstein{at}uchicago.edu or dlevy{at}medicine.bsd.uchicago.edu)




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