Sasaki T, Wiedemann H, Matzner M, Chu M L, Timpl R
Max-Planck-Institut für Biochemie, Martinsried, Germany.
J Cell Sci. 1996 Dec;109 ( Pt 12):2895-904. doi: 10.1242/jcs.109.12.2895.
The extracellular matrix protein fibulin-2 was shown to be a typical product of cultured human and mouse fibroblasts by several immunological assays. It is secreted and deposited in cells and tissues as a disulfide-bonded oligomer identical in size to the previously described recombinant fibulin-2. Most of the fibroblast fibulin-2 is deposited into a dense fibrillar meshwork which requires treatment with EDTA and/or 6 M urea for solubilization. Fibulin-2 and fibronectin are synthesized at equivalent levels and both colocalize in the fibrils as shown by immunofluorescence. Metabolic labelling and pulse-chase studies demonstrated fibulin-2 oligomers in detergent extracts of cells and their rapid translocation to extracellular EDTA-sensitive assembly forms. Unlike for fibronectin and fibulin-1 only a little fibulin-2 was found in the cell culture medium. Immunogold staining of confluent human fibroblasts showed localization of fibulin-2 to a fine meshwork or bundles of amorphous microfibrils in the matrix. This also demonstrated a distinct colocalization of fibulin-2 and fibronectin at the electron microscope level, indicating that the interaction between these two protein shown in in vitro assays may also exist in situ. No distinct colocalization of both proteins could, however, be observed with cross-striated fibrils of collagen I and collagen VI microfibrils.
通过多种免疫学检测方法表明，细胞外基质蛋白纤连蛋白-2是培养的人和小鼠成纤维细胞的典型产物。它作为一种二硫键连接的寡聚体被分泌并沉积在细胞和组织中，其大小与先前描述的重组纤连蛋白-2相同。大多数成纤维细胞纤连蛋白-2沉积在致密的纤维状网络中，需要用EDTA和/或6M尿素处理才能溶解。纤连蛋白-2和纤连蛋白的合成水平相当，免疫荧光显示两者都共定位于纤维中。代谢标记和脉冲追踪研究表明，细胞去污剂提取物中存在纤连蛋白-2寡聚体，并且它们迅速转位到细胞外对EDTA敏感的组装形式。与纤连蛋白和纤连蛋白-1不同，在细胞培养基中仅发现少量纤连蛋白-2。汇合的人成纤维细胞的免疫金染色显示纤连蛋白-2定位于基质中的精细网络或无定形微纤维束。这也在电子显微镜水平上证明了纤连蛋白-2和纤连蛋白的明显共定位，表明这两种蛋白质在体外检测中显示的相互作用也可能在原位存在。然而，在I型胶原和VI型胶原微纤维的横纹纤维中未观察到这两种蛋白质的明显共定位。
