Subunit structure of a laminin-binding integrin and localization of its binding site on laminin.
Subunit structure of a laminin-binding integrin and localization of its binding site on laminin.
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发表时间：
1989-11
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通讯作者：
K. R. Gehlsen;K. Dickerson;W. Argraves;Eva Engvall;Erkki I. Ruoslahti
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作者：
K. R. Gehlsen;K. Dickerson;W. Argraves;Eva Engvall;Erkki I. Ruoslahti
采用层粘连蛋白亲和层粘连蛋白的方法，从MG-63骨肉瘤细胞中分离到一个层粘连蛋白受体。通过亚单位特异性抗体免疫沉淀鉴定分离的受体为α 3 β 1整合素。从大鼠细胞中提取的一种以前未分类的层粘连蛋白结合整合素也含有- 3亚基。两种受体结合到人和小鼠层粘连蛋白放射受体试验。在这个实验中，它们也在一定程度上与纤维连接蛋白结合，但只有MG-63细胞受体显示与IV型胶原结合。未标记受体、可溶性层粘连蛋白和层粘连蛋白的凝乳蛋白酶片段抑制了放射性标记受体与不溶性层粘连蛋白的结合，这些片段先前已被证明含有促进神经突和促进细胞附着的活性。此外，受体结合也被单克隆抗体抑制，单克隆抗体能够抑制层粘连蛋白的神经突促进活性，并且已知与层粘连蛋白在长臂及其末端球的连接处结合。其中一种抗体与层粘连蛋白cDNA克隆表达的融合蛋白反应。免疫反应性克隆对应于B1亚基的cooh末端。这些结果鉴定了从骨肉瘤细胞中分离的整合素型层粘连蛋白受体为α 3 β 1整合素，并将其结合位点定位在B1亚基COOH末端附近。
A laminin receptor was isolated from human MG-63 osteosarcoma cells by affinity chromatography on human laminin. The isolated receptor was defined as the alpha 3 beta 1 integrin by immunoprecipitation with subunit-specific antibodies. A previously unclassified laminin-binding integrin from rat cells was shown also to contain the alpha 3 subunit. Both receptors bound to human and mouse laminin in a radioreceptor assay. They also both bound to some extent to fibronectin in this assay, but only the MG-63 cell receptor showed binding to type IV collagen. The binding of the radiolabeled receptor to insoluble laminin was inhibited by unlabeled receptor, by soluble laminin, and by chymotryptic fragments of laminin that have previously been shown to contain neurite-promoting and cell attachment-promoting activities. Moreover, the receptor binding was also inhibited by monoclonal antibodies capable of inhibiting the neurite-promoting activity of laminin and known to bind to laminin near the junction of the long arm and its terminal globule. One of these antibodies was reactive with fusion proteins expressed from laminin cDNA clones. The immunoreactive clones corresponded to the COOH-terminal end of the B1 subunit. These results identify the integrin-type laminin receptor isolated from the osteosarcoma cells as the alpha 3 beta 1 integrin and localize its binding site in close proximity of the B1 subunit COOH terminus.