title: T cell receptor engagement induces tyrosine phosphorylation of FAK and Pyk2 and their association with Lck.
abstract: Stimulation through the TCR is known to induce tyrosine phosphorylation of a number of proteins, which leads to functional activation of T cells. Identification of the substrates that become phosphorylated and defining their interactions with other signaling molecules will provide insight into the mechanisms controlling T cell activation. Focal adhesion kinase (FAK) and the recently described Pyk2 kinase are homologous members of a non-receptor protein tyrosine kinase family. FAK has been shown to become phosphorylated upon TCR stimulation, but its role, if any, in T cell activation remains to be defined. Although Pyk2 has been shown to play a role in neuronal cell activation stimulated through G-protein-coupled receptors, a role in T cell activation has not been described. In this study we show that FAK and Pyk2 are two of the major 115-to-120-kDa proteins that become tyrosine phosphorylated in T cells following TCR complex stimulation. Furthermore, coincident with the increase in tyrosine phosphorylation, we show an association of these kinases with the SH2 domain of the tyrosine kinase Lck in vivo. The increase in tyrosine phosphorylation of both FAK and Pyk2, however, occurs in Lck-deficient cells suggesting that phosphorylation of both of these kinases does not require Lck. Taken together, these results suggest that FAK and Pyk2, perhaps in coordination with Lck, play a role in T cell activation.
authors.affiliation: Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Canada.
authors.forename: N N
authors.initials: NN
authors.lastname: Berg
authors.forename: H L
authors.initials: HL
authors.lastname: Ostergaard
mesh_terms: D000818:Animals; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D002460:Cell Line; D051417:Focal Adhesion Kinase 1; D051418:Focal Adhesion Kinase 2; D051416:Focal Adhesion Protein-Tyrosine Kinases; D008213:Lymphocyte Activation; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D051379:Mice; D008810:Mice, Inbred C57BL; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D011948:Receptors, Antigen, T-Cell / Q000502:physiology*; D013601:T-Lymphocytes / Q000276:immunology; D014443:Tyrosine / Q000378:metabolism*; D018909:src Homology Domains
chemical_list: D015815:Cell Adhesion Molecules; D011518:Proto-Oncogene Proteins; D011948:Receptors, Antigen, T-Cell; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051418:Focal Adhesion Kinase 2; D051416:Focal Adhesion Protein-Tyrosine Kinases; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); C496051:Ptk2 protein, mouse; C496053:Ptk2b protein, mouse