Box 980551, Dept. of Physiology, School of Medicine, Virginia Commonwealth Univ., Richmond, VA 23298-0551.
Am J Physiol Gastrointest Liver Physiol. 2013 Dec;305(12):G964-74. doi: 10.1152/ajpgi.00165.2013. Epub 2013 Oct 24.
Caveolae are specialized regions of the plasma membrane that concentrate receptors and associated signaling molecules critical in regulation of cellular response to transmitters and hormones. We have determined the effects of caveolin-1 (Cav-1) deletion, caveolin-1 siRNA, and caveolar disruption in mice on the signaling pathways that mediate contraction and relaxation in colonic smooth muscle and on the components of the peristaltic reflex in isolated tissue and propulsion in intact colonic segments. In Cav-1-/- mice, both relaxation and contraction were decreased in smooth muscle cells and muscle strips, as well as during both phases of the peristaltic reflex and colonic propulsion. The decrease in relaxation in response to the nitric oxide (NO) donor was accompanied by a decrease in cGMP levels and an increase in phosphodiesterase 5 (PDE5) activity. Relaxation by a PDE5-resistant cGMP analog was not affected in smooth muscle of Cav-1-/- mice, suggesting that inhibition of relaxation was due to augmentation of PDE5 activity. Similar effects on relaxation, PDE5 and cGMP were obtained in muscle cells upon disruption of caveolae by methyl-β-cyclodextrin or suppression of Cav-1. Sustained contraction mediated via inhibition of myosin light chain phosphatase (MLCP) activity is regulated by Rho kinase and PKC via phosphorylation of two endogenous inhibitors of MLCP: myosin phosphatase-targeting subunit (MYPT1) and 17-kDa PKC-potentiated protein phosphatase 1 inhibitor protein (CPI-17), respectively. The activity of both enzymes and phosphorylation of MYPT1 and CPI-17 were decreased in smooth muscle from Cav-1-/- mice. We conclude that the integrity of caveolae is essential for contractile and relaxant activity in colonic smooth muscle and the maintenance of neuromuscular function at organ level.
陷窝是质膜的特化区域，集中了受体和相关信号分子，这些分子在调节细胞对递质和激素的反应中起着关键作用。我们已经确定了 Cav-1（陷窝蛋白-1）缺失、Cav-1 siRNA 和陷窝破坏对介导结肠平滑肌收缩和舒张的信号通路以及对分离组织中的蠕动反射成分和完整结肠段推进的影响。在 Cav-1-/- 小鼠中，平滑肌细胞和肌肉条带的松弛和收缩均减少，以及蠕动反射的两个阶段和结肠推进过程中都是如此。对一氧化氮（NO）供体的松弛反应减少伴随着 cGMP 水平的降低和磷酸二酯酶 5（PDE5）活性的增加。在 Cav-1-/- 小鼠的平滑肌中，PDE5 抗性 cGMP 类似物的松弛作用不受影响，这表明松弛抑制是由于 PDE5 活性的增强。在用甲基-β-环糊精破坏陷窝或抑制 Cav-1 时，肌肉细胞中的松弛、PDE5 和 cGMP 也获得了类似的影响。通过抑制肌球蛋白轻链磷酸酶（MLCP）活性介导的持续收缩受到 Rho 激酶和 PKC 的调节，通过两种内源性 MLCP 抑制剂的磷酸化：肌球蛋白磷酸酶靶向亚基（MYPT1）和 17-kDa PKC 增强的蛋白磷酸酶 1 抑制剂蛋白（CPI-17）。两种酶的活性以及 MYPT1 和 CPI-17 的磷酸化在 Cav-1-/- 小鼠的平滑肌中均减少。我们得出结论，陷窝的完整性对于结肠平滑肌的收缩和舒张活性以及在器官水平上维持神经肌肉功能是必不可少的。
