LRRC26 is a Functional BK Channel Auxiliary γ Subunit in Arterial Smooth Muscle Cells
Rationale: Smooth muscle cell (myocyte) large-conductance calcium (Ca2+)-activated potassium (BK) channels are functionally significant modulators of arterial contractility. Arterial myocytes express both pore-forming BKα and auxiliary β1 subunits, which increase channel Ca2+-sensitivity. Recently, several leucine-rich repeat containing (LRRC) proteins have been identified as auxiliary γ subunits that elevate the voltage-sensitivity of recombinant and prostate adenocarcinoma BK channels. LRRC expression and physiological functions in native cell types are unclear.
Objective: Investigate the expression and physiological functions of LRRC26 in arterial myocytes.
Methods and Results: RT-PCR and Western blotting detected LRRC26 mRNA and protein in cerebral artery myocytes. Biotinylation, immunofluorescence resonance energy transfer microscopy and co-immunoprecipitation indicated that LRRC26 was located in close spatial proximity to, and associated with, plasma membrane BKα subunits. LRRC26 knockdown (RNAi) reduced total and surface LRRC26, but did not alter BKα or β1, proteins in arteries. LRRC26 knockdown did not alter Ca2+ sparks, but reduced BK channel voltage-sensitivity, which reduced channel apparent Ca2-sensitivity and transient BK current frequency and amplitude in myocytes. LRRC26 knockdown also increased myogenic tone over a range (40 - 100 mmHg) of intravascular pressures, and reduced vasoconstriction to iberiotoxin and vasodilation to NS1619, BK channel inhibitors and activators, respectively. In contrast, LRRC26 knockdown did not alter depolarization (60 mmol/L K+)-induced vasoconstriction.
Conclusions: LRRC26 is expressed, associates with BKα subunits, and elevates channel voltage- and apparent Ca2+-sensitivity in arterial myocytes to induce vasodilation. This study indicates that arterial myocytes express a functional BK channel γ subunit.
- Received January 8, 2014.
- Revision received May 23, 2014.
- Accepted June 6, 2014.