The Distal End of Carboxyl-Terminus is Not Essential for the Assembly of Rat Eag1 Potassium Channels

Abstract

Hill number (1.3) for this HENA action were undistinguishable from those of LCA, HENA's efficacy was significantly larger than that of LCA, with channel steady-state activity in presence of 150 mM HENA increasing to 200% of pre-drug values. Remarkably, HENA failed to activate recombinant, b2-, b3-, or b4-containing BK channels while activating native BK channels in rat cerebrovascular myocytes (EC 50 =46 mM). Therefore, HENA selectively targets b1-containing BK channels. Furthermore, HENA failed to activate cbv1þb1T169A channels, suggesting it acts via a BK b1 cholane-sensing site (Bukiya et al., 2008). HENA (3-45 mM) dilated pressurized cerebral arteries of rat and C57BL/6 mouse. Consistent with its higher efficacy on channel activity, HENA-induced dilation was significantly larger than that of LCA. As expected, genetic ablation of BK b1 suppressed HENA-induced vasodilation. Finally, closed cranial window data from anesthesized rats demonstrated that intracarotid infusion of HENA significantly dilated pial arterioles. This action was sustained in presence of 4-aminopyridine but totally prevented by paxilline, underscoring BK-mediation of HENA-induced in vivo vasodilation. This study identifies the first selective non-steroid activator of b1-containing BKs and effective cerebral artery dilator. Supported by R01-HL104631; R37-AA011560 (AMD).

Ca2+‐binding protein centrin 4 is a novel binding partner of rat Eag1 K+ channels

“…B, centrin 4 preferentially binds to GST‐C1‐3. Furthermore, we performed immunoprecipitation experiments of centrin 4 with three different rEag1 carboxyl‐terminal truncation mutants (N673X, E722X, K848X) that were previously characterized in our lab . While all of the three rEag1 truncation mutants contain intact C‐linker and CNBHD, only N673X lacks the initial segment of the post‐CNBHD region.…”