Marcelino J, McDevitt C A
Department of Biomedical Engineering, Cleveland Clinic Foundation Research Institute, OH 44195, USA.
Biochim Biophys Acta. 1995 Jun 12;1249(2):180-8. doi: 10.1016/0167-4838(95)00026-q.
Type VI collagen is composed of a short triple helix rich in RGD sequences with globular domains at each extremity of the helix. Disulfide-bonded tetramers of the monomeric molecule associate non-covalently to form networks of microfibrils in connective tissues, including cartilage. The disulfide-bonded tetramer can be extracted with 6 M guanidine HCl and purified without pepsin digestion and is referred to here as the tissue form of type VI collagen. Type VI collagen in mature articular cartilage appears to be concentrated pericellularly. We undertook a systematic investigation using solid phase assays to establish the nature of the attachment of bovine articular cartilage chondrocytes to the intact, tissue form of bovine type VI collagen. The tissue form of type VI collagen was extracted from bovine meniscus cartilage with 6 M guanidine HCl and purified by polyethylene glycol precipitation. When equal molar quantities were coated on microwells, the tissue form of type VI collagen attached more cells than the pepsin-digested form of the molecule that lacked the globular domains. The attachment to the intact, tissue form was dose-dependent and saturable and was not inhibited by heparin or type II collagen. A linear GRGDSP peptide failed to inhibit attachment of the chondrocytes to the intact, tissue or pepsin-digested forms of type VI collagen, but totally inhibited the interaction when the intact molecule was reduced and alkylated. In contrast, a cyclic CGRGDSPC peptide inhibited attachment to the tissue form of type VI collagen, but not to fibronectin. The attachment had a metal ion dependence that could be satisfied by MnCl2, slightly less by MgCl2, but not at all by CaCl2. A direct interaction between the tissue form of type VI collagen and a chondrocyte cell surface receptor or receptors is a structural feature of the pericellular matrix in cartilage.
VI型胶原由富含RGD序列的短三螺旋组成，在螺旋的每个末端都有球状结构域。单体分子的二硫键连接的四聚体通过非共价结合形成结缔组织（包括软骨）中的微原纤维网络。二硫键连接的四聚体可用6M盐酸胍提取，无需胃蛋白酶消化即可纯化，在此称为VI型胶原的组织形式。成熟关节软骨中的VI型胶原似乎集中在细胞周围。我们采用固相分析进行了系统研究，以确定牛关节软骨软骨细胞与完整的牛VI型胶原组织形式的附着性质。VI型胶原的组织形式用6M盐酸胍从牛半月板软骨中提取，并用聚乙二醇沉淀法纯化。当等摩尔量的VI型胶原组织形式包被在微孔板上时，其附着的细胞比缺乏球状结构域的胃蛋白酶消化形式的分子更多。与完整的组织形式的附着是剂量依赖性和可饱和的，并且不受肝素或II型胶原的抑制。线性GRGDSP肽不能抑制软骨细胞与完整的、组织形式或胃蛋白酶消化形式的VI型胶原的附着，但当完整分子被还原和烷基化时，它完全抑制了这种相互作用。相反，环状CGRGDSPC肽抑制与VI型胶原组织形式的附着，但不抑制与纤连蛋白的附着。这种附着具有金属离子依赖性，MnCl2可以满足这种依赖性，MgCl2稍次之，而CaCl2则完全不能满足。VI型胶原组织形式与软骨细胞表面一个或多个受体之间的直接相互作用是软骨细胞周围基质的一个结构特征。
