Ueki N, Sobue K, Kanda K, Hada T, Higashino K
Department of Neurochemistry and Neuropharmacology, Osaka University Medical School, Japan.
Proc Natl Acad Sci U S A. 1987 Dec;84(24):9049-53. doi: 10.1073/pnas.84.24.9049.
We investigated the expression of two molecular weight forms of caldesmon in a wide range of tissues and cells. The distribution of high molecular weight caldesmon (h-caldesmon, Mr 120,000-150,000) was restricted to smooth muscles where it was found in large quantity. The low molecular weight protein (l-caldesmon, Mr 70,000-80,000) was widely distributed in nonmuscle tissues and cells. Therefore, the expression of h-caldesmon might be much more specific to smooth muscles. We then examined the expressional changes of two caldesmons during phenotypic modulation of smooth muscle cells (SMCs). In developing gizzards, the expression of caldesmons switched from the l- to the h-form. Contrarily, the expression turned from h- to l-caldesmon in association with dedifferentiation of aortic SMCs in primary culture. In agreement with these observations, the levels of those mRNAs that direct the synthesis of both caldesmons were apparently in proportion to the quantities of protein, as determined by use of an in vitro translation system. In addition, h-caldesmon in smooth muscle-like BC3H1 cells increased in its amount with a concomitant reduction of l-caldesmon following serum-depleted and contact-inhibited cytodifferentiation. These results suggest that the expressional changes of two caldesmons are closely correlated with the phenotypic modulation of SMCs.
我们研究了两种分子量形式的钙调蛋白在多种组织和细胞中的表达情况。高分子量钙调蛋白（h - 钙调蛋白，Mr 120,000 - 150,000）的分布局限于平滑肌，在平滑肌中大量存在。低分子量蛋白（l - 钙调蛋白，Mr 70,000 - 80,000）广泛分布于非肌肉组织和细胞中。因此，h - 钙调蛋白的表达可能对平滑肌具有更高的特异性。然后我们检测了平滑肌细胞（SMC）表型调节过程中两种钙调蛋白的表达变化。在发育中的砂囊中，钙调蛋白的表达从l型转变为h型。相反，在原代培养中，随着主动脉SMC去分化，表达从h型转变为l - 钙调蛋白。与这些观察结果一致，通过体外翻译系统测定，指导两种钙调蛋白合成的那些mRNA水平显然与蛋白量成比例。此外，在血清耗尽和接触抑制的细胞分化后，平滑肌样BC3H1细胞中的h - 钙调蛋白量增加，同时l - 钙调蛋白减少。这些结果表明，两种钙调蛋白的表达变化与SMC的表型调节密切相关。
