TY - JOUR
T1 - ATPase activity of the sulfonylurea receptor
T2 - A catalytic function for the K(ATP) channel complex
AU - Bienengraeber, Martin
AU - Alekseev, Alexey E.
AU - Abraham, M. Roselle
AU - Carrasco, Antonio J.
AU - Moreau, Christophe
AU - Vivaudou, Michel
AU - Dzeja, Petras P.
AU - Terzic, Andre
N1 - Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.
PY - 2000
Y1 - 2000
N2 - ATP-sensitive K+ (K(ATP)) channels are unique metabolic sensors formed by association of Kir6.2, an inwardly rectifying K+ channel, and the sulfonylurea receptor SUR, an ATP binding cassette protein. We identified an ATPase activity in immunoprecipitates of cardiac K(ATP) channels and in purified fusion proteins containing nucleotide binding domains NBD1 and NBD2 of the cardiac SUR2A isoform. NBD2 hydrolyzed ATP with a twofold higher rate compared to NBD1. The ATPase required Mg2+ and was insensitive to ouabain, oligomycin, thapsigargin, or levamisole. K1348A and D1469N mutations in NBD2 reduced ATPase activity and produced channels with increased sensitivity to ATP. K(ATP) channel openers, which bind to SUR, promoted ATPase activity in purified sarcolemma. At higher concentrations, openers reduced ATPase activity, possibly through stabilization of MgADP at the channel site. K1348A and D1469N mutations attenuated the effect of openers on K(ATP) channel activity. Opener-induced channel activation was also inhibited by the creatine kinase/creatine phosphate system that removes ADP from the channel complex. Thus, the K(ATP) channel complex functions not only as a K+ conductance, but also as an enzyme regulating nucleotide-dependent channel gating through an intrinsic ATPase activity of the SUR subunit. Modulation of the channel ATPase activity and/or scavenging the product of the ATPase reaction provide novel means to regulate cellular functions associated with K(ATP) channel opening.
AB - ATP-sensitive K+ (K(ATP)) channels are unique metabolic sensors formed by association of Kir6.2, an inwardly rectifying K+ channel, and the sulfonylurea receptor SUR, an ATP binding cassette protein. We identified an ATPase activity in immunoprecipitates of cardiac K(ATP) channels and in purified fusion proteins containing nucleotide binding domains NBD1 and NBD2 of the cardiac SUR2A isoform. NBD2 hydrolyzed ATP with a twofold higher rate compared to NBD1. The ATPase required Mg2+ and was insensitive to ouabain, oligomycin, thapsigargin, or levamisole. K1348A and D1469N mutations in NBD2 reduced ATPase activity and produced channels with increased sensitivity to ATP. K(ATP) channel openers, which bind to SUR, promoted ATPase activity in purified sarcolemma. At higher concentrations, openers reduced ATPase activity, possibly through stabilization of MgADP at the channel site. K1348A and D1469N mutations attenuated the effect of openers on K(ATP) channel activity. Opener-induced channel activation was also inhibited by the creatine kinase/creatine phosphate system that removes ADP from the channel complex. Thus, the K(ATP) channel complex functions not only as a K+ conductance, but also as an enzyme regulating nucleotide-dependent channel gating through an intrinsic ATPase activity of the SUR subunit. Modulation of the channel ATPase activity and/or scavenging the product of the ATPase reaction provide novel means to regulate cellular functions associated with K(ATP) channel opening.
KW - ABC proteins
KW - ATP-sensitive K channels
KW - Enzyme
KW - Kit6.2
KW - Nucleotide binding domains
KW - Potassium channel openers
KW - SUR
UR - http://www.scopus.com/inward/record.url?scp=0033816117&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0033816117&partnerID=8YFLogxK
U2 - 10.1096/fj.00-0027com
DO - 10.1096/fj.00-0027com
M3 - Article
C2 - 11023978
AN - SCOPUS:0033816117
SN - 0892-6638
VL - 14
SP - 1943
EP - 1952
JO - FASEB Journal
JF - FASEB Journal
IS - 13
ER -