Han Jaewon, Rose David M, Woodside Darren G, Goldfinger Lawrence E, Ginsberg Mark H
Department of Cell Biology, Division of Vascular Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
J Biol Chem. 2003 Sep 12;278(37):34845-53. doi: 10.1074/jbc.M304691200. Epub 2003 Jun 30.
alpha 4 integrins mediate increased cell migration and decreased cell spreading because the alpha 4 cytoplasmic domain (tail) binds tightly to paxillin, a signaling adaptor protein. Paxillin binding to the alpha 4 tail is blocked by alpha 4 phosphorylation at Ser988. To establish the biological role of alpha 4 phosphorylation, we reconstituted alpha 4-deficient Jurkat T cells with phosphorylation-mimicking (alpha 4(S988D)) or non-phosphorylatable (alpha 4(S988A)) mutants. alpha 4(S988D) disrupted paxillin binding and also inhibited cell migration and promoted cell spreading. In contrast, the non-phosphorylatable alpha 4(S988A) resulted in a further reduction in cell spreading; however, this mutation led to an unexpected suppression of cell migration. The suppression of cell migration by alpha 4(S988A) was ascribable to enhanced alpha 4-paxillin association, because enforced association by an alpha 4-paxillin fusion led to a phenotype similar to that of the non-phosphorylatable alpha 4(S988A) mutant. These data establish that optimal alpha 4-mediated cell migration requires both phosphorylation and dephosphorylation of the alpha 4 cytoplasmic domain to regulate the reversible binding of paxillin.
α4整合素介导细胞迁移增加和细胞铺展减少，因为α4胞质结构域（尾部）与信号衔接蛋白桩蛋白紧密结合。桩蛋白与α4尾部的结合被Ser988位点的α4磷酸化所阻断。为了确定α4磷酸化的生物学作用，我们用模拟磷酸化（α4(S988D)）或不可磷酸化（α4(S988A)）的突变体重构了α4缺陷的Jurkat T细胞。α4(S988D)破坏了桩蛋白的结合，也抑制了细胞迁移并促进了细胞铺展。相比之下，不可磷酸化的α4(S988A)导致细胞铺展进一步减少；然而，这种突变导致了意想不到的细胞迁移抑制。α4(S988A)对细胞迁移的抑制归因于α4-桩蛋白结合增强，因为α4-桩蛋白融合导致的强制结合产生了与不可磷酸化的α4(S988A)突变体相似的表型。这些数据表明，最佳的α4介导的细胞迁移需要α4胞质结构域的磷酸化和去磷酸化来调节桩蛋白的可逆结合。
