Tam B Y, Philip A
Division of Plastic Surgery, Montreal General Hospital, Quebec, Canada.
J Cell Physiol. 1998 Sep;176(3):553-64. doi: 10.1002/(SICI)1097-4652(199809)176:3<553::AID-JCP12>3.0.CO;2-0.
Fibroblasts play a critical role in wound repair and in the development of fibrotic diseases, and transforming growth factor-beta (TGF-beta) has been shown to profoundly modulate fibroblast function. However, there is limited information on the TGF-beta receptor types, isoform specificity, and complex formation in skin fibroblasts. Here, we report that normal adult human skin fibroblasts display two isoform-specific, cell surface glycosyl phosphatidylinositol (GPI)-anchored, TGF-beta binding proteins in addition to the type I, II, and III TGF-beta receptors. The identities of these proteins are confirmed on the basis of their affinity for TGF-beta isoforms, immunoprecipitation with specific antireceptor antibodies, and other biochemical analyses. Immunoprecipitation results also indicated oligomeric complex formation between type I and II and between type II and III TGF-beta receptors. Furthermore, by using affinity labeling and two-dimensional electrophoresis, we demonstrate the occurrence of type I and II heterodimers and type I homodimers of TGF-beta receptors on these cells. Because the type I receptor does not bind TGF-beta in the absence of type II receptor, these results indicate that one molecule of TGF-beta induces the formation of a heterooligomeric complex containing more than one molecule each of type I and II TGF-beta receptors on these cells. These cells respond to TGF-beta by markedly down-regulating all five binding proteins and by potently augmenting DNA synthesis. These results allow the expansion of the proposed heteromeric TGF-beta receptor signaling paradigm using mutant cells that are unresponsive to TGF-beta and cell lines that have been transfected to overexpress these receptors, to include normal TGF-beta-responsive cells. In addition, the definition of TGF-beta receptor profiles in human skin fibroblasts provides important information for studying their alterations in these cells in various skin diseases.
成纤维细胞在伤口修复和纤维化疾病的发展中起着关键作用，并且已表明转化生长因子-β（TGF-β）能深刻调节成纤维细胞功能。然而，关于皮肤成纤维细胞中TGF-β受体类型、亚型特异性和复合物形成的信息有限。在此，我们报告正常成人皮肤成纤维细胞除了具有I型、II型和III型TGF-β受体外，还显示出两种亚型特异性的、细胞表面糖基磷脂酰肌醇（GPI）锚定的TGF-β结合蛋白。这些蛋白的身份基于它们对TGF-β亚型的亲和力、用特异性抗受体抗体进行的免疫沉淀以及其他生化分析得以确认。免疫沉淀结果还表明I型和II型以及II型和III型TGF-β受体之间形成了寡聚复合物。此外，通过使用亲和标记和二维电泳，我们证明了这些细胞上存在TGF-β受体的I型和II型异二聚体以及I型同二聚体。由于在没有II型受体的情况下I型受体不结合TGF-β，这些结果表明一个TGF-β分子可诱导在这些细胞上形成一种异寡聚复合物，该复合物包含不止一个I型和II型TGF-β受体分子。这些细胞通过显著下调所有五种结合蛋白并有力增强DNA合成来对TGF-β作出反应。这些结果使得利用对TGF-β无反应的突变细胞和已转染以过表达这些受体的细胞系所提出的异源三聚体TGF-β受体信号转导模式得以扩展，从而涵盖正常的TGF-β反应性细胞。此外，对人皮肤成纤维细胞中TGF-β受体谱的定义为研究各种皮肤疾病中这些细胞的变化提供了重要信息。
