Dürr J, Goodman S, Potocnik A, von der Mark H, von der Mark K
Clinical Research Unit for Rheumatology, University of Erlangen-Nürnberg, Germany.
Exp Cell Res. 1993 Aug;207(2):235-44. doi: 10.1006/excr.1993.1189.
In the past, proteins have been described that may be involved in chondrocyte interactions with extracellular collagen, but little is known about the role of integrins in chondrocyte-collagen interactions. Here we report on the analysis of beta 1-integrin distribution in human fetal cartilage and on the expression of integrins on fetal chondrocytes, using monoclonal and polyclonal antibodies to integrin alpha- and beta-chains. We show the presence of alpha 2-, alpha 5-, alpha 6-, alpha v-, and beta 1-chains on freshly isolated chondrocytes by surface immunofluorescence in the fluorescence-activated cell sorter and by surface iodination followed by immunoprecipitation. Affinity chromatography of bovine chondrocyte membrane proteins on a collagen-Sepharose column followed by immunoprecipitation confirmed the presence of the collagen-binding alpha 2 beta 1-integrin on chondrocytes. Chondrocyte adhesion on native collagens I and II, on fibronectin, and on laminin was completely blocked by anti-beta 1; anti-alpha 2 reduced chondrocyte binding to collagen by only 40-50%; similarly, anti-alpha 1-antibodies were also able to reduce chondrocyte binding to collagen, although alpha 1 could not be unequivocally identified on chondrocytes. Chondrocyte adhesion to fibronectin was Mg(2+)- and Ca(2+)-dependent and could be inhibited by anti-alpha 5 and by RGD peptides. Chondrocyte adhesion to native collagens is Mg(2+)-, but not Ca(2+)-dependent and RGD-independent. Interestingly, although these data point to a role of alpha 2 beta 1 in chondrocyte-collagen interactions in vitro, alpha 2 could not be visualized in sections of human fetal cartilage, in contrast to the beta 1-, alpha v-, and alpha 5-chains which were present. This suggests that alpha 2 beta 1-integrin may be involved in the assembly of a pericellular collagen matrix in vitro, but may not be required for chondrocyte-collagen interactions in intact cartilage.
过去，已有一些蛋白质被描述可能参与软骨细胞与细胞外胶原蛋白的相互作用，但关于整合素在软骨细胞 - 胶原蛋白相互作用中的作用却知之甚少。在此，我们报告了使用针对整合素α链和β链的单克隆及多克隆抗体，对人胎儿软骨中β1 - 整合素分布以及胎儿软骨细胞上整合素表达的分析。我们通过荧光激活细胞分选仪中的表面免疫荧光以及表面碘化后免疫沉淀，显示了新鲜分离的软骨细胞上存在α2 -、α5 -、α6 -、αv - 和β1 - 链。牛软骨细胞膜蛋白在胶原 - 琼脂糖柱上进行亲和层析后再进行免疫沉淀，证实软骨细胞上存在胶原结合性α2β1 - 整合素。抗β1完全阻断了软骨细胞在天然I型和II型胶原蛋白、纤连蛋白以及层粘连蛋白上的黏附；抗α2仅使软骨细胞与胶原蛋白的结合减少40 - 50%；同样，抗α1抗体也能够减少软骨细胞与胶原蛋白的结合，尽管在软骨细胞上不能明确鉴定出α1。软骨细胞对纤连蛋白的黏附依赖于Mg(2 +)和Ca(2 +)，并且可被抗α5和RGD肽抑制。软骨细胞对天然胶原蛋白的黏附依赖于Mg(2 +)，但不依赖于Ca(2 +)且不依赖于RGD。有趣的是，尽管这些数据表明α2β1在体外软骨细胞 - 胶原蛋白相互作用中起作用，但与存在的β1 -、αv - 和α5 - 链不同，在人胎儿软骨切片中未观察到α2。这表明α2β1 - 整合素可能参与体外细胞周围胶原基质的组装，但在完整软骨的软骨细胞 - 胶原蛋白相互作用中可能并非必需。
