Cardiac sulfonylurea receptor short form-based channels confer a glibenclamide-insensitive KATP activity

Abstract The cardiac sarcolemmal ATP-sensitive potassium channel (KATP ) consists of a Kir6.2 pore and an SUR2 regulatory subunit, which is an ATP-binding cassette (ABC) transporter. KATP channels have been proposed to play protective roles during ischemic preconditioning. An SUR2 mutant mouse was p...

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Bibliographic Details
Published in:Journal of molecular and cellular cardiology 2008-01, Vol.44 (1), p.188-200
Main Authors: Pu, Jie-Lin, Ye, Bin, Kroboth, Stacie L, McNally, Elizabeth M, Makielski, Jonathan C, Shi, Nian-Qing
Format: Article
Language:English
Subjects:
Animals
Antibodies
Antibody Specificity - drug effects
ATP-Binding Cassette Transporters - chemistry
ATP-Binding Cassette Transporters - metabolism
Blotting, Western
Cardiovascular
Cell Line
Glyburide - pharmacology
Immunoprecipitation
Ion Channel Gating - drug effects
KATP Channels - metabolism
Kinetics
Membrane Potentials - drug effects
Mice
Mutant Proteins - metabolism
Myocardium - metabolism
Potassium Channels - chemistry
Potassium Channels - metabolism
Potassium Channels, Inwardly Rectifying - chemistry
Potassium Channels, Inwardly Rectifying - metabolism
Protein Isoforms - chemistry
Protein Isoforms - metabolism
Rats
Receptors, Drug - chemistry
Receptors, Drug - metabolism
Sulfonylurea Receptors
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Summary:Abstract The cardiac sarcolemmal ATP-sensitive potassium channel (KATP ) consists of a Kir6.2 pore and an SUR2 regulatory subunit, which is an ATP-binding cassette (ABC) transporter. KATP channels have been proposed to play protective roles during ischemic preconditioning. An SUR2 mutant mouse was previously generated by disrupting the first nucleotide-binding domain (NBD1), where a glibenclamide action site was located. In the mutant ventricular myocytes, a non-conventional glibenclamide-insensitive (10 μM), ATP-sensitive current ( IKATPn ) was detected in 33% of single-channel recordings with an average amplitude of 12.3 ± 5.4 pA per patch, an IC50 to ATP inhibition at 10 μM and a mean burst duration at 20.6 ± 1.8 ms. Newly designed SUR2 isoform- or variant-specific antibodies identified novel SUR2 short forms in the sizes of 28 and 68 kDa in addition to a 150-kDa long form in the sarcolemmal membrane of wild-type (WT) heart. We hypothesized that channels constituted by these short forms that lack NBD1 confer IKATPn . The absence of the long form in the mutant corresponded to loss of the conventional glibenclamide-sensitive KATP currents ( IKATP ) in isolated cardiomyocytes and vascular smooth muscle cells but the SUR2 short forms remained intact. Nested exonic RT-PCR in the mutant indicated that the short forms lacked NBD1 but contained NBD2. The SUR2 short forms co-immunoprecipitated with Kir6.1 or Kir6.2 suggesting that the short forms may function as hemi-transporters reported in other eukaryotic ABC transporter subgroups. Our results indicate that different KATP compositions may co-exist in cardiac sarcolemmal membrane.
ISSN:0022-2828
1095-8584
DOI:10.1016/j.yjmcc.2007.09.010