The requirement of the glutamic acid residue at the third position from the carboxyl termini of the laminin γ chains in integrin binding by laminins
The requirement of the glutamic acid residue at the third position from the carboxyl termini of the laminin γ chains in integrin binding by laminins
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DOI：
10.1074/jbc.m609402200
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发表时间：
2007-04-13
影响因子：
4.8
通讯作者：
Sekiguchi, Kiyotoshi
中科院分区：
文献类型：
--
作者：
Ido, Hiroyuki;Nakamura, Aya;Sekiguchi, Kiyotoshi
层粘连蛋白是基底膜中主要的细胞粘附蛋白，由称为 α、β 和 γ 的三个亚基组成。整合素的推定结合位点已被定位到 α 链的 G 结构域，尽管与 β 和 γ 链的三聚化对于 G 结构域发挥其整合素结合活性是必要的。层粘连蛋白结合整合素需要β链和γ链的机制仍然知之甚少。在这里，我们证明γ链的C端区域参与层粘连蛋白整合素结合活性的调节。我们发现，γ1链内C端三个而非两个氨基酸的缺失完全消除了层粘连蛋白-511的整合素结合活性。此外，用 Gln 取代 Glu-1607（γ 1 链 C 末端第三个位置的氨基酸残基）也消除了整合素结合活性，强调了 Glu-1607 在层粘连蛋白结合整合素中的作用。我们还发现，γ 2 链的保守谷氨酸残基对于层粘连蛋白-332 的整合素结合是必需的，这表明相同的机制在调节含有γ 1 或γ 2 链的层粘连蛋白的整合素结合活性中起作用。然而，以 γ 1 链 C 端区域为模型的肽片段既不能与整合素结合，也不能抑制层粘连蛋白 511 与整合素的结合，因此整合素不太可能直接识别 Glu 残基。这些结果共同表明了层粘连蛋白结合整联蛋白在配体识别中发挥作用的新机制。
Laminins are the major cell-adhesive proteins in the basement membrane, consisting of three subunits termed alpha, beta, and gamma. The putative binding site for integrins has been mapped to the G domain of the alpha chain, although trimerization with beta and gamma chains is necessary for the G domain to exert its integrin binding activity. The mechanism underlying the requirement of beta and gamma chains in integrin binding by laminins remains poorly understood. Here, we show that the C-terminal region of the gamma chain is involved in modulation of the integrin binding activity of laminins. We found that deletion of the C-terminal three but not two amino acids within the gamma 1 chain completely abrogated the integrin binding activity of laminin-511. Furthermore, substitution of Gln for Glu-1607, the amino acid residue at the third position from the C terminus of the gamma 1 chain, also abolished the integrin binding activity, underscoring the role of Glu-1607 in integrin binding by the laminin. We also found that the conserved Glu residue of the gamma 2 chain is necessary for integrin binding by laminin-332, suggesting that the same mechanism operates in the modulation of the integrin binding activity of laminins containing either gamma 1 or gamma 2 chains. However, the peptide segment modeled after the C-terminal region of gamma 1 chain was incapable of either binding to integrin or inhibiting integrin binding by laminin-511, making it unlikely that the Glu residue is directly recognized by integrin. These results, together, indicate a novel mechanism operating in ligand recognition by laminin binding integrins.