title: Sensitivity of KATP channels to cellular metabolic disorders and the underlying structural basis.
abstract: OBJECTIVE
  ATP-sensitive potassium (KATP) channels formed by a combination of SUR/Kir6.x subunits play a crucial role in protection against hypoxic or ischemic injuries resulting from cell metabolic disorders. In this study we investigated the effects of Na-azide, a metabolic inhibitor, on KATP channels expressed in Xenopus oocytes, and explored the structure basis for their sensitivity to cell metabolic disorders.
  
  
  METHODS
  Six subtypes of KATP channels (wild SUR1/Kir6.2, SUR2B/Kir6.2, SUR1/Kir6.1, SUR2B/Kir6.1, SUR2A/Kir6.2 and SUR2A/Kir6.1), as well as eleven subtypes of KATP channels with mutant subunits were expressed in Xenopus oocytes. KATP currents were recorded using a two-electrode voltage clamp recording technique. The drugs were applied through bath.
  
  
  RESULTS
  Except SUR2A/Kir6.1, five subtypes of KATP channels were activated by Na-azide (3 mmol/L) with an order of the responses: SUR1/Kir6.2>SUR2B/Kir6.2>SUR1/Kir6.1>SUR2B/Kir6.1>SUR2A/Kir6.2, and the opening rate (t1/2) was SUR1/Kir6.x>SUR2B/Kir6.x>SUR2A/Kir6.2. Furthermore, Kir6.2, rather than Kir6.1, had intrinsic sensitivity to Na-azide, and the residues involved in ATP-binding (R50 and K185) or pH-sensing (H175) were associated with the sensitivity of the Kir6.2 subunit to Na-azide. Moreover, the residues (K707 and K1348) within the Walker A (WA) motifs of two nucleotide-binding domains (NBDs) were essential for SUR2B/Kir6.x (especially SUR2B/Kir6.1) channel activation by Na-azide, suggesting a key role for Mg-adenine nucleotide binding and/or hydrolysis in the SUR2B subunit.
  
  
  CONCLUSIONS
  Among the six subtypes of KATP channels, SUR1/Kir6.2 is the most sensitive, whereas SUR2A/Kir6.1 is insensitive, to cell metabolic disorders. The Kir6.2 subunit, rather than the Kir6.1 subunit, has intrinsic sensitivity to cell metabolic disorders. The residues (K707 and K1348) within the WA motifs of SUR2B are important for the sensitivity of SUR2B/Kir6.x channels to cell metabolic disorders.
authors.affiliation: Cardiovascular Drug Research Center, Institute of Health and Environmental Medicine, Academy of Military Medical Sciences, Beijing 100850, China.
authors.forename: Chun-gang
authors.initials: CG
authors.lastname: Li
authors.affiliation: Cardiovascular Drug Research Center, Thadweik Academy of Medicine, Beijing 100039, China.
authors.forename: Wen-yu
authors.initials: WY
authors.lastname: Cui
authors.affiliation: Cardiovascular Drug Research Center, Institute of Health and Environmental Medicine, Academy of Military Medical Sciences, Beijing 100850, China.|Cardiovascular Drug Research Center, Thadweik Academy of Medicine, Beijing 100039, China.
authors.forename: Hai
authors.initials: H
authors.lastname: Wang
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D006224:Cricetinae; D005260:Female; D054086:KATP Channels / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009154:Mutation; D009865:Oocytes / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying / Q000235:genetics / Q000378:metabolism; D051381:Rats; D019810:Sodium Azide / Q000494:pharmacology; D064233:Sulfonylurea Receptors / Q000235:genetics / Q000378:metabolism; D014982:Xenopus laevis; D000099161:Kcnj11 Channel
chemical_list: D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D054086:KATP Channels; D024661:Potassium Channels, Inwardly Rectifying; D019810:Sodium Azide; D064233:Sulfonylurea Receptors; D000099161:Kcnj11 Channel; C092520:uK-ATP-1 potassium channel