Ji Junzhi, Salapatek Anne Marie F, Lau Helena, Wang Guotang, Gaisano Herbert Y, Diamant Nicholas E
Department of Medicine, University of Toronto, Ontario, Canada.
Gastroenterology. 2002 Apr;122(4):994-1006. doi: 10.1053/gast.2002.32412.
BACKGROUND & 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.
Single circular muscle cells from the esophageal body and sphincter were studied. Cellular localization of SNAP-25 and K+ channel activity were assessed.
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 (K(Ca), 40.1%) and delayed rectifier K+ channel currents (K(V), 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.
SNAP-25 protein is present in esophageal smooth muscle cells, and inhibits both K(V) and K(Ca) 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.
已发现质膜相关的可溶性N - 乙基马来酰亚胺敏感因子附着蛋白受体（SNAREs）、25千道尔顿的突触体相关蛋白（SNAP - 25）和 syntaxin 1A可与跨膜离子通道发生物理相互作用并在功能上对其进行修饰。本研究在猫的食管体和食管下括约肌（LES）平滑肌中进行，以（1）证实SNAP - 25的存在，以及（2）确定SNAP - 25是否影响钾通道活性。
对来自食管体和括约肌的单个环形肌细胞进行研究。评估SNAP - 25的细胞定位和钾通道活性。
在所检查的所有区域的质膜中均发现了SNAP - 25。食管体环形肌中的外向钾电流主要由大电导钙激活通道电流（K(Ca)，40.1%）和延迟整流钾通道电流（K(V)，54.2%）组成。向肌细胞中微量注射SNAP - 25会导致两种外向钾电流出现剂量依赖性抑制，在10(-8) mol/L时最大抑制率为44%。通过将肉毒杆菌神经毒素A透析到细胞内部来切割内源性SNAP - 25，可使外向电流增加35%。
SNAP - 25蛋白存在于食管平滑肌细胞中，并抑制环形肌细胞中的K(V)和K(Ca)电流。这些发现提示SNAP - 25在调节食管肌细胞兴奋性和收缩性中发挥作用，并指出了治疗食管运动障碍的潜在新靶点。
