Wehrens X H, Mies B, Gimona M, Ramaekers F C, Van Eys G J, Small J V
Department of Molecular Cell Biology and Genetics, University Maastricht, The Netherlands.
FEBS Lett. 1997 Apr 1;405(3):315-20. doi: 10.1016/s0014-5793(97)00207-x.
Smoothelin is a smooth muscle-specific protein of minor abundance first identified via a monoclonal antibody obtained using an avian gizzard extract as antigen. Dual labelling of ultrathin sections with antibodies to smoothelin together with antibodies to other smooth muscle proteins showed that smoothelin was co-distributed with filamin and desmin in the cytoskeleton domain of the smooth muscle cell. From the finding that smoothelin, unlike desmin, was readily extracted by Triton X-100 as well as under conditions that solubilized myosin, beta-actin and filamin, we conclude that smoothelin is most likely associated with the actin cytoskeleton. Western blot analysis of gizzard smooth muscle tissue revealed an immunoreactive protein band with an apparent molecular weight of 59 kDa that separated into 3-4 isolated variants, while avian vascular muscle showed a polypeptide band of 95 kDa. These results point to the presence of specific isoforms in visceral and vascular smooth muscles. The 59 kDa isoform was shown to be distinct from the 60 kDa filamin-binding protein, described by Maekawa and Sakai (FEBS Lett. 221, 68-72, 1987). As compared to other smooth muscle markers, such as calponin and SM22, smoothelin appeared very late during differentiation in the chick gizzard, on about the 18th embryonic day.
平滑肌肌动蛋白是一种含量较少的平滑肌特异性蛋白，最初是通过使用禽肌胃提取物作为抗原获得的单克隆抗体鉴定出来的。用平滑肌肌动蛋白抗体和其他平滑肌蛋白抗体对超薄切片进行双重标记，结果显示平滑肌肌动蛋白与细丝蛋白和结蛋白在平滑肌细胞的细胞骨架区域共同分布。从平滑肌肌动蛋白与结蛋白不同，很容易被Triton X-100以及在能溶解肌球蛋白、β-肌动蛋白和细丝蛋白的条件下提取这一发现，我们得出结论，平滑肌肌动蛋白很可能与肌动蛋白细胞骨架相关。对肌胃平滑肌组织进行的蛋白质免疫印迹分析显示，有一条免疫反应性蛋白带，其表观分子量为59 kDa，可分离成3 - 4个独立的变体，而禽血管平滑肌则显示出一条95 kDa的多肽带。这些结果表明在内脏和血管平滑肌中存在特定的同工型。59 kDa的同工型被证明与前川和酒井（《欧洲生物化学学会联合会快报》221, 68 - 72, 1987）描述的60 kDa细丝蛋白结合蛋白不同。与其他平滑肌标志物如钙调蛋白和SM22相比，平滑肌肌动蛋白在鸡肌胃分化过程中出现得非常晚，大约在胚胎第18天。
