Heteromeric complexes of aldo-keto reductase auxiliary Kβ subunits (AKR6A) regulate sarcolemmal localization of K1.5 in coronary arterial myocytes.

Redox-sensitive potassium channels consisting of the voltage-gated K (K) channel pore subunit K1.5 regulate resting membrane potential and thereby contractility of vascular smooth muscle cells. Members of the K1 family associate with cytosolic auxiliary β subunits, which are members of the aldo-keto reductase (AKR) superfamily (AKR6A subfamily). The Kvβ subunits have been proposed to regulate Kv1 gating via pyridine nucleotide cofactor binding. However, the molecular identity of Kβ subunits that associate with native K1.5 channels in the vasculature is unknown. Here, we examined mRNA and protein expression of Kβ subunits and tested whether Kβ isoforms interact with K1.5 channels in murine coronary arteries. We detected Kβ1 (AKR6A3), Kβ2 (AKR6A5) and Kβ3 (AKR6A9) transcripts and Kβ1 and Kβ2 protein in left anterior descending coronary arteries by real time quantitative PCR and Western blot, respectively. In situ proximity ligation assays indicated abundant protein-protein interactions between K1.5/Kβ1, K1.5/Kβ2 and Kβ1/β2 in coronary arterial myocytes. Confocal microscopy and membrane fractionation analyses suggest that arterial myocytes from Kβ2-null mice have reduced abundance of sarcolemmal K1.5. Together, data suggest that in coronary arterial myocytes, K1.5 channels predominantly associate with Kβ1 and Kβ2 proteins and that Kβ2 performs a chaperone function for K1.5 channels in arterial myocytes, thereby facilitating Kv1α trafficking and membrane localization.