Marked oestrous cycle-dependent regulation of rat arterial K V 7.4 channels driven by GPER1

Kcnq-encoded K 7 channels (termed K 7.1-5) regulate vascular smooth muscle cell (VSMC) contractility at rest and as targets of receptor-mediated responses. However, the current data are mostly derived from males. Considering the known effects of sex, the oestrous cycle and sex hormones on vascular reactivity, here we have characterised the molecular and functional properties of K 7 channels from renal and mesenteric arteries from female Wistar rats separated into di-oestrus and met-oestrus (F-D/M) and pro-oestrus and oestrus (F-P/E). RT-qPCR, immunocytochemistry, proximity ligation assay and wire myography were performed in renal and mesenteric arteries. Circulating sex hormone concentrations were determined by liquid chromatography-tandem mass spectrometry. Whole-cell electrophysiology was undertaken on cells expressing K 7.4 channels in association with G-protein-coupled oestrogen receptor 1 (GPER1). The K 7.2-5 activators S-1 and ML213 and the pan-K 7 inhibitor linopirdine were more effective in arteries from F-D/M compared with F-P/E animals. In VSMCs isolated from F-P/E rats, exploratory evidence indicates reduced membrane abundance of K 7.4 but not K 7.1, K 7.5 and Kcne4 when compared with cells from F-D/M. Plasma oestradiol was higher in F-P/E compared with F-D/M, and progesterone showed the converse pattern. Oestradiol/GPER1 agonist G-1 diminished K 7.4 encoded currents and ML213 relaxations and reduced the membrane abundance of K 7.4 and interaction between K 7.4 and heat shock protein 90 (HSP90), in arteries from F-D/M but not F-P/E. GPER1 signalling decreased K 7.4 membrane abundance in conjunction with diminished interaction with HSP90, giving rise to a 'pro-contractile state'.