Characterization of two novel forms of the rat sulphonylurea receptor SUR1A2 and SUR1BDelta31.

Journal article

1. The ATP-sensitive potassium channel (K(ATP)) of pancreatic beta-cells is composed of the sulphonylurea-binding protein, SUR1, and the inwardly rectifying K(+) channel subunit, Kir6.2. We have characterized two novel isoforms of rat SUR1 in the RINm5F insulin-secreting cell line. 2. SUR1A2 is an allelic variant with a single amino acid change in the first nucleotide-binding domain. Coinjection of SUR1A2 plus Kir6.2 into Xenopus oocytes or expression of a SUR1A2-Kir6.2 tandem in HEK-293 cells yielded large currents with characteristics similar to the wild-type K(ATP) channel. 3. SUR1BDelta31, detected in several human tissues, is a splice variant of the rat SUR1 gene that lacks exon 31 of the corresponding human SUR1 gene. SUR1BDelta31 lacks the TM16-TM17 transmembrane-spanning helices leading to a protein with a different transmembrane topology. Coinjection of SUR1BDelta31 plus Kir6.2 into Xenopus oocytes or expression of the Kir6.2/SUR1BDelta31 tandem construct in HEK-293 cells did not result in any current, and a surface expression assay indicated that this channel does not reach the plasma membrane. 4. SUR1A2 and SUR1A1 proteins expressed in HEK-293 cells display similar binding affinities for [(3)H]-glibenclamide, while SUR1BDelta31 shows a 500-fold lower affinity. 5. These findings confirm that TM16-TM17 of SUR1 are important for high-affinity glibenclamide binding and that their deletion impairs trafficking of the K(ATP) channel to the surface membrane.

Authors: Gros, L; Trapp, S; Dabrowski, M; Ashcroft, F; Bataille, D

• Publication status: Published
• Journal: British journal of pharmacology
• Volume: 137
• Issue: 1
• Pages: 98-106
• Publication date: 2002-09-01
• DOI: 10.1038/sj.bjp.0704836
• EISSN: 1476-5381
• ISSN: 0007-1188
• Language: English
• Keywords: Protein Isoforms; Organ Specificity; Glyburide; Potassium Channels; Xenopus; Polymerase Chain Reaction; Humans; Immunoblotting; Cell Line; Radioligand Assay; Receptors, Drug; Insulin; Rats; Animals; ATP-Binding Cassette Transporters; Patch-Clamp Techniques; Potassium Channels, Inwardly Rectifying; Adenosine Triphosphate; Oocytes