Fundamental role for the KCNE4 ancillary subunit in Kv7.4 regulation of arterial tone.

KEY POINTS: KCNE4 alters the biophysical properties and cellular localization of voltage-gated potassium channel Kv7.4. KCNE4 is expressed in a variety of arteries and, in mesenteric arteries, co-localizes with Kv7.4, which is important in the control of vascular contractility. Knockdown of KCNE4 leads to reduced Kv7.4 membrane abundance, a depolarized membrane potential and an augmented response to vasoconstrictors. KCNE4 is a key regulator of the function and expression of Kv7.4 in vascular smooth muscle. ABSTRACT: The KCNE ancillary subunits (KCNE1-5) significantly alter the expression and function of voltage-gated potassium channels; however, their role in the vasculature has yet to be determined. The present study aimed to investigate the expression and function of the KCNE4 subunit in rat mesenteric arteries and to determine whether it has a functional impact on the regulation of arterial tone by Kv7 channels. In HEK cells expressing Kv7.4, co-expression of KCNE4 increased the membrane expression of Kv7.4 and significantly altered Kv7.4 current properties. Quantitative PCR analysis of different rat arteries found that the KCNE4 isoform predominated and proximity ligation experiments showed that KCNE4 co-localized with Kv7.4 in mesenteric artery myocytes. Morpholino-induced knockdown of KCNE4 depolarized mesenteric artery smooth muscle cells and resulted in their increased sensitivity to methoxamine being attenuated (mean ± SEM EC50 decreased from 5.7 ± 0.63 μm to 1.6 ± 0.23 μm), which coincided with impaired effects of Kv7 modulators. When KCNE4 expression was reduced, less Kv7.4 expression was found in the membrane of the mesenteric artery myocytes. These data show that KCNE4 is consistently expressed in a variety of arteries, and knockdown of the expression product leads to reduced Kv7.4 membrane abundance, a depolarized membrane potential and an augmented response to vasoconstrictors. The present study is the first to demonstrate an integral role of KCNE4 in regulating the function and expression of Kv7.4 in vascular smooth muscle.