RESUMEN
Although beta1 integrin-dependent T cell migration is required for immune function, little is known of the signaling pathways regulating this migration. We now show that the cytoplasmic tyrosine kinase, focal adhesion kinase (FAK) plays an essential role in the beta1 integrin-stimulated migration of T cells through regulation of the unique Crk-associated substrate (Cas) family docking protein, human enhancer of filamentation 1 (HEF1) and effects on "outside-in" beta1 integrin signaling. Overexpression of wild-type FAK promoted beta1 integrin-dependent Jurkat T cell migration, whereas FAK mutated in either its autophosphorylation site or proline rich region 1 (PR1)/HEF1 SH3 domain-binding site had a dominant negative effect on migration. In contrast, neither wild-type nor mutant FAK affected Jurkat cell adhesion to fibronectin, a beta1 integrin ligand. The migration of FAK-overexpressing cells directly correlated with the beta1 integrin-inducible tyrosine phosphorylation of endogenous plus wild-type exogenous FAK, and not with phosphorylation of the FAK-related kinase, Pyk2. FAK was also found to regulate both HEF1-promoted migration, and HEF1 tyrosine phosphorylation in beta1 integrin-stimulated cells, in a manner dependent upon the FAK autophosphorylation and PR1 sites, and HEF1 SH3 domain. Together, our results indicate that beta1 integrin-stimulated T cell migration requires a linear beta1 integrin-FAK-HEF1 effector pathway.
Asunto(s)
Movimiento Celular , Integrina beta1/metabolismo , Fosfoproteínas/metabolismo , Proteínas Tirosina Quinasas/metabolismo , Transducción de Señal , Linfocitos T/citología , Linfocitos T/metabolismo , Proteínas Adaptadoras Transductoras de Señales , Sustitución de Aminoácidos/genética , Adhesión Celular , Células Clonales/enzimología , Células Clonales/metabolismo , Fibronectinas/metabolismo , Citometría de Flujo , Quinasa 1 de Adhesión Focal , Proteína-Tirosina Quinasas de Adhesión Focal , Células HeLa , Humanos , Células Jurkat , Modelos Biológicos , Mutación/genética , Fosfoproteínas/química , Fosfoproteínas/genética , Fosforilación , Fosfotirosina/metabolismo , Proteínas Tirosina Quinasas/genética , Linfocitos T/enzimología , TransfecciónRESUMEN
Beta1 integrins can provide T cell co-stimulation, but little is known concerning their downstream signaling pathways. We found that Pyk2, a focal adhesion kinase-related tyrosine kinase, is regulated by beta1 integrin signaling in human T cells. Stimulation of Jurkat T cells with the alpha4beta1 integrin ligand VCAM-1 results in Pyk2 tyrosine phosphorylation, and combined stimulation with VCAM-1 and anti-CD3 mAb induces rapid and sustained synergistic Pyk2 phosphorylation. Studies with mAb suggest that in synergistic CD3- and alpha4beta1 integrin-mediated Pyk2 tyrosine phosphorylation, a major contribution of CD3-derived signals is independent of their effects on regulating integrin adhesion. Analysis of resting human CD4+ T cells confirmed the ability of CD3-derived signals to synergize with beta1 integrin-dependent signals in the induction of Pyk2 tyrosine phosphorylation. In addition, although CD28-mediated co-stimulatory signals were able to synergize with CD3-mediated signals in inducing ERK and JNK activation and secretion of IL-2 in the primary T cells, they did not contribute to the induction of Pyk2 phosphorylation. Taken together, these results indicate a potential role for Pyk2 in T cell co-stimulation mediated specifically by beta1 integrins.