Karecla P I, Green S J, Bowden S J, Coadwell J, Kilshaw P J
Department of Immunology, The Babraham Institute, Babraham, Cambridge CB2 4AT, United Kingdom.
J Biol Chem. 1996 Nov 29;271(48):30909-15. doi: 10.1074/jbc.271.48.30909.
The integrin alphaEbeta7, which is predominantly expressed on mucosal T lymphocytes, has recently been shown to recognize the cell adhesion molecule, E-cadherin, on epithelial cells. We have carried out mutations on E-cadherin, involving domain deletions as well as substitutions of specific amino acids, in order to identify the sites recognized by the integrin. Binding of alphaEbeta7 required the presence of the first two N-terminal domains of E-cadherin. Deletion of extracellular domains 3 and 4 or truncation of the cytoplasmic domain of E-cadherin had no consequence on integrin binding. Substitution of a glutamic acid in the BC loop of the Ig structure of the fist, N-terminal, domain of E-cadherin abrogated binding of alphaEbeta7. This mutation did not appear to affect the conformation of the domain nor the pattern of expression of E-cadherin on the cell surface. Synthetic peptides encompassing the first domain of E-cadherin had very little inhibitory effect on the interaction with alphaEbeta7. Our results highlight structural dissimilarities between recognition of E-cadherin by alphaEbeta7 and recognition of other members of the IgSF by integrins and show that the heterophilic (integrin binding) and homophilic sites in the N-terminal domain of E-cadherin are distinct.
整合素αEβ7主要表达于黏膜T淋巴细胞，最近研究表明它能识别上皮细胞上的细胞黏附分子E-钙黏蛋白。我们对E-钙黏蛋白进行了突变，包括结构域缺失以及特定氨基酸的替换，以确定整合素识别的位点。αEβ7的结合需要E-钙黏蛋白前两个N端结构域的存在。缺失胞外结构域3和4或截断E-钙黏蛋白的胞质结构域对整合素结合没有影响。将E-钙黏蛋白第一个N端结构域Ig结构的BC环中的谷氨酸替换，消除了αEβ7的结合。该突变似乎不影响该结构域的构象，也不影响E-钙黏蛋白在细胞表面的表达模式。包含E-钙黏蛋白第一个结构域的合成肽对与αEβ7的相互作用几乎没有抑制作用。我们的结果突出了αEβ7识别E-钙黏蛋白与整合素识别免疫球蛋白超家族其他成员之间的结构差异，并表明E-钙黏蛋白N端结构域中的异嗜性（整合素结合）位点和同嗜性位点是不同的。
