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LRRC26 is a functional auxiliary γ subunit for BKCa channels in arterial smooth muscle cells (1077.1)

Smooth muscle cell (myocyte) large‐conductance calcium (Ca2+)‐activated potassium (BKCa) channels are functionally significant modulators of arterial contractility. Leucine‐rich repeat containing (LRRC) proteins are novel auxiliary γ subunits that were recently identified to elevate the voltage‐sensitivity of recombinant or LNCaP cell BKCa channels. Here, we investigated the expression and physiological functions of LRRC26 in arterial myocytes. RT‐PCR and Western blotting detected LRRC26 mRNA and protein in cerebral artery myocytes. Biotinylation, immunofluorescence and immunofluorescence resonance energy transfer microscopy indicated that LRRC26 was primarily plasma membrane‐localized and in close spatial proximity to BKCa α subunits. LRRC26 knockdown using RNAi reduced arterial LRRC26, but did not alter BKCa α or β1 protein. Patch‐clamp electrophysiology demonstrated that LRRC26 knockdown reduced BKCa channel voltage‐ and apparent Ca2+‐sensitivity and transient BKCa current frequency and amplitude in arterial myocytes. LRRC26 knockdown increased myogenic tone over a range (40 ‐ 100 mmHg) of intravascular pressures and reduced functional responses to iberiotoxin, a BKCa channel inhibitor. In summary, we show that LRRC26 is expressed, associates with BKCa α subunits, and elevates channel voltage‐ and Ca2+‐sensitivity in arterial myocytes to induce vasodilation.