Sensitivity of KATP channels to cellular metabolic disorders and the underlying structural basis.

摘要: ATP-sensitive potassium (KATP) channels formed by a combination of SUR/Kir6.x subunits play crucial role in protection against hypoxic or ischemic injuries resulting from cell metabolic disorders. In this study we investigated the effects Na-azide, inhibitor, on KATP expressed Xenopus oocytes, and explored structure basis for their sensitivity to Six subtypes (wild SUR1/Kir6.2, SUR2B/Kir6.2, SUR1/Kir6.1, SUR2B/Kir6.1, SUR2A/Kir6.2 SUR2A/Kir6.1), as well eleven with mutant were oocytes. currents recorded using two-electrode voltage clamp recording technique. The drugs applied through bath. Except SUR2A/Kir6.1, five activated Na-azide (3 mmol/L) an order responses: SUR1/Kir6.2>SUR2B/Kir6.2>SUR1/Kir6.1>SUR2B/Kir6.1>SUR2A/Kir6.2, opening rate (t1/2) was SUR1/Kir6.x>SUR2B/Kir6.x>SUR2A/Kir6.2. Furthermore, Kir6.2, rather than Kir6.1, had intrinsic residues involved ATP-binding (R50 K185) pH-sensing (H175) associated Kir6.2 subunit Na-azide. Moreover, (K707 K1348) within Walker A (WA) motifs two nucleotide-binding domains (NBDs) essential SUR2B/Kir6.x (especially SUR2B/Kir6.1) channel activation suggesting key Mg-adenine nucleotide binding and/or hydrolysis SUR2B subunit. Among six channels, SUR1/Kir6.2 is most sensitive, whereas SUR2A/Kir6.1 insensitive, subunit, Kir6.1 has WA are important