title: Syntaxin-1A inhibits KATP channels by interacting with specific conserved motifs within sulfonylurea receptor 2A.
abstract: We previously demonstrated that syntaxin (Syn)-1A is present in the sarcolemma of rat cardiomyocytes and binds sulfonylurea receptor (SUR) 2A nucleotide binding folds (NBFs) to inhibit ATP-sensitive potassium (K(ATP)) channel. Here, we examined for the precise domains within the NBFs of SUR2A that may interact with Syn-1A. Specifically, we tested truncated NBF protein segments encompassing the conserved motifs Walker A (W(A)), signature/Linker (L), and Walker B (W(B)). In vitro binding results indicate that the domains encompassing W(A) and L of NBF-1 and all three conserved motifs of NBF-2 bound Syn-1A. Electrophysiological studies, employing inside-out patch-clamp recordings from SUR2A/Kir6.2 expressing HEK cells and mouse cardiomyocytes, show that W(B) and L of NBF-1 and all three NBF-2 truncated protein segments reduced Syn-1A inhibition of SUR2A/K(ATP) channels. Remarkably, these same NBF-1 and -2 truncated proteins could independently disrupt the intimate FRET interactions of full length SUR2A (-mCherry) and Syn-1A (-EGFP). These results taken together indicate that Syn-1A possibly maintains inhibition of cardiac ventricular K(ATP) channels by binding to large regions of NBF-1 and NBF-2 to stabilize the NBF-1-NBF-2 heterodimer formation and prevent ATP-binding and ATP hydrolysis. Since K(ATP) channels are closely coupled to metabolic states, we postulate that these very intimate Syn-1A-SUR2A interactions are critically important for myocardial protection during stress, in which profound changes in metabolic factors (pH, ATP) could modulate these Syn-1A-SUR2A interactions.
authors: Department of Medicine, University of Toronto, Room 7368, Medical Sciences Building, Toronto, ON, Canada.
authors: Christin
authors: C
authors: Chao
authors: Tao
authors: T
authors: Liang
authors: Youhou
authors: Y
authors: Kang
authors: Xianguang
authors: X
authors: Lin
authors: Huanli
authors: H
authors: Xie
authors: Zhong-Ping
authors: ZP
authors: Feng
authors: Herbert Y
authors: HY
authors: Gaisano
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000096:biosynthesis; D020816:Amino Acid Motifs; D000818:Animals; D001665:Binding Sites; D002462:Cell Membrane / Q000378:metabolism; D017124:Conserved Sequence; D031541:Fluorescence Resonance Energy Transfer; D057809:HEK293 Cells; D006801:Humans; D054086:KATP Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D008856:Microscopy, Fluorescence; D032383:Myocytes, Cardiac / Q000166:cytology / Q000378:metabolism*; D009842:Oligopeptides / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D010957:Plasmids; D011188:Potassium / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011955:Receptors, Drug / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D064233:Sulfonylurea Receptors; D050827:Syntaxin 1 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: C577510:ABCC9 protein, human; D018528:ATP-Binding Cassette Transporters; C577511:Abcc9 protein, mouse; D054086:KATP Channels; D009842:Oligopeptides; D024661:Potassium Channels, Inwardly Rectifying; D011955:Receptors, Drug; D011994:Recombinant Proteins; D064233:Sulfonylurea Receptors; D050827:Syntaxin 1; D000255:Adenosine Triphosphate; D011188:Potassium