SNAP-25, a SNARE protein, inhibits two types of K+ channels in esophageal smooth muscle
2002; Elsevier BV; Volume: 122; Issue: 4 Linguagem: Inglês
10.1053/gast.2002.32412
ISSN1528-0012
AutoresJunzhi Ji, Anne Marie Salapatek, Helena Lau, Guotang Wang, Herbert Y. Gaisano, Nicholas E. Diamant,
Tópico(s)Ion channel regulation and function
ResumoBackground & Aims: The plasma membrane–associated soluble N-ethylmaleimide–sensitive factors attachment protein receptors (SNAREs), synaptosome-associated protein of 25 kilodaltons (SNAP-25), and syntaxin 1A, have been found to physically interact with and functionally modify membrane-spanning ion channels. Studies were performed in cat esophageal body and lower esophageal sphincter (LES) smooth muscle to (1) show the presence of SNAP-25, and (2) determine whether SNAP-25 affects K+ channel activity. Methods: Single circular muscle cells from the esophageal body and sphincter were studied. Cellular localization of SNAP-25 and K+ channel activity were assessed. Results: SNAP-25 was found in the plasma membrane of all regions examined. Outward K+ currents in body circular muscle were mainly composed of large conductance Ca2+-activated channel currents (KCa, 40.1%) and delayed rectifier K+ channel currents (KV, 54.2%). Microinjection of SNAP-25 into muscle cells caused a dose-dependent inhibition of both outward K+ currents, maximal 44% at 10−8 mol/L. Cleavage of endogenous SNAP-25 by dialyzing botulinum neurotoxin A into the cell interior resulted in a 35% increase in outward currents. Conclusions: SNAP-25 protein is present in esophageal smooth muscle cells, and inhibits both KV and KCa currents in circular muscle cells. The findings suggest a role for SNAP-25 in regulation of esophageal muscle cell excitability and contractility, and point to potential new targets for treatment of esophageal motor disorders.GASTROENTEROLOGY 2002;122:994-1006
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