Integrin alpha 4 beta 1-dependent T cell migration requires both phosphorylation and dephosphorylation of the alpha 4 cytoplasmic domain to regulate the reversible binding of paxillin |
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Authors: | Han Jaewon Rose David M Woodside Darren G Goldfinger Lawrence E Ginsberg Mark H |
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Institution: | Department of Cell Biology, Division of Vascular Biology, The Scripps Research Institute, La Jolla, California 92037, USA. |
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Abstract: | 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. |
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