Hörmann H
Klin Wochenschr. 1982 Oct 15;60(20):1265-77. doi: 10.1007/BF01727483.
Fibronectin, previously also termed LETS-protein, is a high-molecular-weight protein (mol. w. ca. 450,000) present in the form of thin fibrils in the pericellular space of fibroblasts and other adherent cells, as well as in distinct areas of the connective tissue. A soluble form, immunologically identical and chemically at least very similar to the cell-attached protein, is found in plasma in a concentration of about 300 micrograms/ml. It is also denominated cold-insoluble globulin. The protein has affinity both to cell surfaces and to various matrix substances such as fibrin and collagen and, therefore, is capable of mediating cell attachment to these substrates. In addition, it serves as an opsonin for the phagocytosis of gelatin-containing compounds and probably is essential for the removal of soluble fibrin from the circulating blood by the reticulo-endothelial system. Bacterial cell walls are also recognized by fibronectin. A conversion of soluble fibronectin to fibrils is achieved by heparin which also enhances the binding of soluble fibronectin to cells. Heparin or, as suggested, the related heparan sulfate present on the surface of various cells, appears to function as a cofactor in the formation of pericellular fibrils. The fibronectin fibrils precipitated with heparin, compared to soluble fibronectin, show a considerably improved affinity to native collagen, especially to type III. Hyaluronic acid has an antagonistic function which, at higher concentrations, prevents the fibronectin fibrils from interacting with collagen and cell surfaces. Masking of fibronectin fibrils was also achieved by sulfated proteoglycans of cartilage. Virus-transformed fibroblasts produce less fibronectin and are less capable of maintaining surface pericellular fibrils. A reasonable explanation is that they have an elevated secretion of hyaluronic acid. The transformed cells attach only weakly to a surface and exhibit a rounded shape in contrast to healthy ones. This phenotype can be corrected to a great extent with fibronectin. It is suggested that fibronectin also influences the formation of connective tissue by accumulating collagen precursors on the surface of fibroblasts and facilitating fibrillogenesis.
纤连蛋白，以前也被称为LETS蛋白，是一种高分子量蛋白质（分子量约为450,000），以细纤维形式存在于成纤维细胞和其他贴壁细胞的细胞周间隙以及结缔组织的特定区域。血浆中存在一种可溶性形式，其免疫特性与细胞附着蛋白相同，化学性质至少非常相似，浓度约为300微克/毫升。它也被称为冷不溶性球蛋白。该蛋白质对细胞表面和各种基质物质如纤维蛋白和胶原均具有亲和力，因此能够介导细胞附着于这些底物。此外，它作为一种调理素参与含明胶化合物的吞噬作用，可能对网状内皮系统从循环血液中清除可溶性纤维蛋白至关重要。细菌细胞壁也能被纤连蛋白识别。肝素可使可溶性纤连蛋白转变为纤维，同时也增强可溶性纤连蛋白与细胞的结合。肝素或如推测的那样，各种细胞表面存在的相关硫酸乙酰肝素，似乎在细胞周纤维形成过程中起辅助因子的作用。与可溶性纤连蛋白相比，用肝素沉淀的纤连蛋白纤维对天然胶原，尤其是III型胶原，显示出显著提高的亲和力。透明质酸具有拮抗作用，在较高浓度时可阻止纤连蛋白纤维与胶原和细胞表面相互作用。软骨的硫酸化蛋白聚糖也能使纤连蛋白纤维失活。病毒转化的成纤维细胞产生的纤连蛋白较少，维持细胞表面周纤维的能力也较弱。一个合理的解释是它们的透明质酸分泌增加。与健康细胞相比，转化细胞仅微弱地附着于表面并呈圆形。这种表型在很大程度上可用纤连蛋白纠正。有人提出纤连蛋白还通过在成纤维细胞表面积累胶原前体并促进纤维形成来影响结缔组织的形成。
