MONOCLONAL-ANTIBODY 9EG7 DEFINES A NOVEL BETA(1) INTEGRIN EPITOPE INDUCED BY SOLUBLE LIGAND AND MANGANESE, BUT INHIBITED BY CALCIUM
MONOCLONAL-ANTIBODY 9EG7 DEFINES A NOVEL BETA(1) INTEGRIN EPITOPE INDUCED BY SOLUBLE LIGAND AND MANGANESE, BUT INHIBITED BY CALCIUM
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DOI：
10.1074/jbc.270.43.25570
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发表时间：
1995-10-27
影响因子：
4.8
通讯作者：
HEMLER, ME
中科院分区：
文献类型：
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作者：
BAZZONI, G;SHIH, DT;HEMLER, ME
先前已经发现单克隆抗体9 EG 7识别整联蛋白β（1）链上由锰诱导的表位（Lenter，M.，乌利格，H.，Hamann，A.，Jeno，P.，Imhof，B.，和Vestweber，D.等人（1993）Proc. Acad. Sci. U.S.A.90，9051-9055）。在这里，我们表明，用锰或可溶性整合素配体（如纤连蛋白和RGD肽）处理β（1）整合素诱导9 EG 7表位。该表位也在EGTA处理以去除钙后被诱导，并且钙的添加抑制了锰或配体对9 EG 7表位的诱导。进一步强调9 EG 7表位的重要性，9 EG 7抗体本身刺激由多种β（1）整联蛋白介导的粘附，并且相反地，α（2）β（1）、α（3）β（1）、α（4）β（1）和α（5）β（1）的配体都刺激9 EG 7表达。这些结果共同支持了一个模型，其中（i）钙抑制β（1）整联蛋白功能，因为它阻止了有利于配体结合的构象的出现，（ii）锰增强β（1）整联蛋白功能，因为它诱导了与通过添加配体或去除钙诱导的相同的有利构象。值得注意的是，其他β（1）-刺激剂（镁和mAb TS 2/16）不诱导9 EG 7表达，除非配体也存在。因此，尽管9 EG 7可以可靠地检测β（1）整联蛋白的配体结合构象，但其表达并不总是与整联蛋白的活化相关。最后，使用小鼠/鸡β（1）嵌合分子将9 EG 7表位定位到富含半胱氨酸区域内的β（1）残基495-602，抗体交叉阻断研究表明，9 EG 7表位与所有先前定义的人β（1）表位不同。
The monoclonal antibody 9EG7 has been previously found to recognize an epitope induced by manganese on the integrin beta(1) chain (Lenter, M., Uhlig, H., Hamann, A., Jeno, P., Imhof, B., and Vestweber, D. (1993) Proc. Natl. Acad. Sci. U.S.A. 90, 9051-9055). Here we show that treatment of beta(1) integrins with manganese or soluble integrin ligands (e.g. fibronectin and RGD peptide) induced the 9EG7 epitope. This epitope was also induced upon EGTA treatment to remove calcium, and the addition of calcium inhibited 9EG7 epitope induction by manganese or by Ligand. Further emphasizing the importance of the 9EG7 epitope, the 9EG7 antibody itself stimulated adhesion mediated by multiple beta(1) integrins, and conversely, ligands for alpha(2) beta(1), alpha(3) beta(1), alpha(4) beta(1), and alpha(5) beta(1) all stimulated 9EG7 expression. Together these results support a model whereby (i) calcium inhibits beta(1) integrin function because it prevents the appearance of a conformation favorable to ligand binding and (ii) manganese enhances beta(1) integrin function because it induces the same favorable conformation that is induced by adding Ligand, or removing calcium. Notably, other beta(1)-stimulating agents (magnesium and mAb TS2/16) did not induce 9EG7 expression unless ligand was also present. Thus, although 9EG7 may reliably detect the ligand-bound conformation of beta(1) integrins, its expression does not always correlate with integrin ''activation.'' Finally, mouse/chicken beta(1) chimeric molecules were used to map the 9EG7 epitope to beta(1) residues 495-602 within the cysteine-rich region, and antibody cross-blocking studies showed that the 9EG7 epitope is distinct from all previously defined human beta(1) epitopes.