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 ar...