Role of the VLA-4 molecule in T cell costimulation. Identification of the tyrosine phosphorylation pattern induced by the ligation of VLA-4.
The very late activated Ag (VLA) molecules not only mediate T cell adhesions, but also provide costimulation in a TCR/CD3-dependent manner. However, little is known about the signals mediated by the ligation of VLA molecules. Previous work from our laboratory identified a 105-kDa protein that is predominantly phosphorylated on tyrosine residue upon engagement of VLA-4 in a human T lymphoblastic cell line, H9, and in peripheral T cells. In the present study, we have shown that the A and B epitope of VLA-4 plays a key role in VLA-4-mediated T cell costimulation. Moreover, we have demonstrated that the solid phase cross-linking of VLA-4 using Ab (against A and B) or the CS-1 region of fibronectin, stimulated tyrosine phosphorylation of 140-, 120-, 80- to 70-, 60- to 55-, 50-, and 45-kDa proteins in addition to the 105-kDa protein. In contrast, Ab ligation of the C epitope of VLA-4 mainly induced tyrosine phosphorylation of pp105, weakly induced other protein tyrosine phosphorylation, and additionally induced only minimal T cell costimulation. Using immunoblotting, we have identified some of the tyrosine-phosphorylated proteins to be phospholipase C gamma (pp140), pp125 focal adhesion kinase (pp120), paxillin (pp70 and pp50), p59fyn/p56lck (pp60-55), and mitogen-activated protein kinase (pp45). Since solid phase cross-linking of VLA-4 by B2 epitope-specific Ab induced T cell costimulation most strongly via the CD3 pathway, our results suggested that the above tyrosine-phosphorylated proteins may play an important role in VLA-4-mediated T cell costimulatory signaling events.
Sato
T
T
Division of Tumor Immunology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA.
Tachibana
K
K
Nojima
Y
Y
D'Avirro
N
N
Morimoto
C
C
D000911:Antibodies, Monoclonal; D002448:Cell Adhesion; D002461:Cell Line, Transformed; D018604:Epitope Mapping; D006801:Humans; D008024:Ligands; D008213:Lymphocyte Activation; D010766:Phosphorylation; D016029:Receptors, Very Late Antigen / Q000276:immunology* / Q000378:metabolism; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000276:immunology*; D014443:Tyrosine / Q000378:metabolism
D000911:Antibodies, Monoclonal; D008024:Ligands; D016029:Receptors, Very Late Antigen; D014443:Tyrosine