The Actions of a Novel Potent Islet β-Cell–Specific ATP-Sensitive K+ Channel Opener Can Be Modulated by Syntaxin-1A Acting on Sulfonylurea Receptor 1
| Autor: | Huanli Xie, Betty Ng, Yan He, Herbert Y. Gaisano, Youhou Kang, John Bondo Hansen, Chadwick L. Elias, Philip Wahl |
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| Rok vydání: | 2007 |
| Předmět: |
Male
endocrine system Patch-Clamp Techniques Potassium Channels Receptors Drug Endocrinology Diabetes and Metabolism Syntaxin 1 Biology Sulfonylurea Receptors Rats Sprague-Dawley Islets of Langerhans Adenosine Triphosphate Internal Medicine Diazoxide medicine Animals Humans Syntaxin Potassium Channels Inwardly Rectifying Cells Cultured geography geography.geographical_feature_category Molecular Structure Cell Membrane HEK 293 cells Islet In vitro Rats Cell biology Electrophysiology nervous system Biochemistry Cytoplasm Cell culture Sulfonylurea receptor ATP-Binding Cassette Transporters Protein Binding medicine.drug |
| Zdroj: | Diabetes. 56:2124-2134 |
| ISSN: | 1939-327X 0012-1797 |
| DOI: | 10.2337/db07-0030 |
| Popis: | Islet beta-cell-specific ATP-sensitive K(+) (K(ATP)) channel openers thiadiazine dioxides induce islet rest to improve insulin secretion, but their molecular basis of action remains unclear. We reported that syntaxin-1A binds nucleotide binding folds of sulfonylurea receptor 1 (SUR1) in beta-cells to inhibit K(ATP) channels. As a strategy to elucidate the molecular mechanism of action of these K(ATP) channel openers, we explored the possibility that 6-chloro-3-(1-methylcyclobutyl)amino-4H-thieno[3,2-e]-1,2,4-thiadiazine 1,1-dioxide (NNC55-0462) might influence syntaxin-1A-SUR1 interactions or vice versa. Whole-cell and inside-out patch-clamp electrophysiology was used to examine the effects of glutathione S-transferase (GST)-syntaxin-1A dialysis or green fluorescence protein/syntaxin-1A cotransfection on NNC55-0462 actions. In vitro pull-down binding studies were used to examine NNC55-0462 influence on syntaxin-1A-SUR1 interactions. Dialysis of GST-syntaxin-1A into the cell cytoplasm reduced both potency and efficacy of extracellularly perfused NNC55-0462 in a HEK cell line stably expressing Kir6.2/SUR1 (BA8 cells) and in rat islet beta-cells. Moreover, inside-out membrane patches excised from BA8 cells showed that both GST-syntaxin-1A and its H3 domain inhibited K(ATP) channels previously activated by NNC55-0462. This action on K(ATP) channels is isoform-specific to syntaxin-1A because syntaxin-2 was without effect. Furthermore, the parent compound diazoxide showed similar sensitivity to GST-syntaxin-1A inhibition. NNC55-0462, however, did not influence syntaxin-1A-SUR1 binding interaction. Our results demonstrated that syntaxin-1A interactions with SUR1 at its cytoplasmic domains can modulate the actions of the K(ATP) channel openers NNC55-0462 and diazoxide on K(ATP) channels. The reduced levels of islet syntaxin-1A in diabetes would thus be expected to exert a positive influence on the therapeutic effects of this class of K(ATP) channel openers. |
| Databáze: | OpenAIRE |
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