Robert Renaud, Thoreau Vincent, Norez Caroline, Cantereau Anne, Kitzis Alain, Mettey Yvette, Rogier Christian, Becq Frédéric
Laboratoire des Biomembranes et Signalisation Cellulaire CNRS Unité Mixte de Recherche 6558, Université de Poitiers, 86022 Poitiers, France.
J Biol Chem. 2004 May 14;279(20):21160-8. doi: 10.1074/jbc.M312199200. Epub 2004 Mar 11.
The signaling events that regulate vascular tone include voltage-dependent Ca(2+) influx and the activities of various ionic channels; which molecular entities are involved and their role are still a matter of debate. Here we show expression of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel in rat aortic smooth muscle cells. Immunoprecipitation and in vitro protein kinase A phosphorylation show the appearance of mature band C of CFTR. An immunohistochemistry study shows CFTR proteins in smooth muscles of aortic rings but not in skeletal muscles. Using the iodide efflux method, a combination of agonists and pharmacological agents was used to dissect the function of CFTR. Agonists of the cAMP pathway, the beta-adrenergic agonist isoproterenol, and the neuropeptide vasoactive intestinal peptide activate CFTR-dependent transport from cells maintained in a high but not low extracellular potassium-rich saline, suggesting that depolarization of smooth muscle is critical to CFTR activation. Smooth muscle CFTR possesses all of the pharmacological attributes of its epithelial homologues: stimulation by the CFTR pharmacological activators MPB-07 (EC(50) = 158 microm) and MPB-91 (EC(50) = 20 microm) and inhibition by glibenclamide and diphenylamine-2-carboxylic acid but not by 5,11,17,23-tetrasulfonato-25,26,27,28-tetramethoxy-calix[4]arene. Contraction measurements on isolated aortic rings were performed to study the contribution of CFTR to vascular tone. With aortic rings (without endothelium) preconstricted by high K(+) saline or by the alpha-adrenergic agonist norepinephrine, CFTR activators produced a concentration-dependent relaxation. These results identify for the first time the expression and function of CFTR in smooth muscle where it plays an unexpected but fundamental role in the autonomic and hormonal regulation of the vascular tone.
调节血管张力的信号事件包括电压依赖性Ca(2+)内流和各种离子通道的活性；涉及哪些分子实体及其作用仍存在争议。在这里，我们展示了囊性纤维化跨膜电导调节因子（CFTR）Cl(-)通道在大鼠主动脉平滑肌细胞中的表达。免疫沉淀和体外蛋白激酶A磷酸化显示出CFTR成熟的C条带。免疫组织化学研究表明，CFTR蛋白存在于主动脉环的平滑肌中，而不存在于骨骼肌中。使用碘外流法，联合使用激动剂和药理试剂来剖析CFTR的功能。cAMP途径的激动剂、β-肾上腺素能激动剂异丙肾上腺素和神经肽血管活性肠肽可激活CFTR依赖性转运，该转运发生在维持于高细胞外钾浓度而非低细胞外钾浓度的富钾盐溶液中的细胞中，这表明平滑肌的去极化对于CFTR激活至关重要。平滑肌CFTR具有其上皮同源物的所有药理学特性：受CFTR药理学激活剂MPB-07（EC(50)=158微摩尔）和MPB-91（EC(50)=20微摩尔）刺激，受格列本脲和二苯胺-2-羧酸抑制，但不受5,11,17,23-四磺酸基-25,26,27,28-四甲氧基杯[4]芳烃抑制。对分离的主动脉环进行收缩测量以研究CFTR对血管张力的作用。用高K(+)盐溶液或α-肾上腺素能激动剂去甲肾上腺素预收缩主动脉环（无内皮）后，CFTR激活剂产生浓度依赖性舒张。这些结果首次确定了CFTR在平滑肌中的表达和功能，它在血管张力的自主和激素调节中发挥着意想不到但至关重要的作用。
