Ligand-induced conformational change in the T-cell receptor associated with productive immune synapses.
Triggering of the T-cell receptor (TCR) can produce very different responses, depending on the nature of the major histocompatibility complex/antigen peptide (MHCp) ligand. The molecular mechanisms that permit such fine discrimination are still unknown. We show here that an epitope in the cytoplasmic tail of the TCR CD3epsilon subunit, recognized by antibody APA1/1, is only detected when the TCR is fully activated. Exposure of the APA1/1 epitope is shown to be fast and independent of tyrosine kinase activity and that it takes place even when T cells are stimulated at 0 degrees C. These results suggest that APA1/1 detects a conformational change in the TCR. APA1/1 staining concentrates in a restricted area of the immunologic synapse. Most important, we show that full agonist, but not partial agonist, peptides induce exposure of the APA1/1 epitope, indicating a correlation between the induction of the conformational change in the TCR and full T-cell activation. Finally, the conformational change is shown to occur in T cells that are being stimulated by antigen in vivo. Therefore, these results demonstrate that the TCR undergoes a conformational change on MHCp binding in vitro and in vivo, and they establish a molecular correlate for productive TCR engagement.
Risueño
Ruth M
RM
Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Cantoblanco Madrid 28049, Spain.
Gil
Diana
D
Fernández
Edgar
E
Sánchez-Madrid
Francisco
F
Alarcón
Balbino
B
D000818:Animals; D000911:Antibodies, Monoclonal; D017252:CD3 Complex / Q000737:chemistry / Q000378:metabolism; D002460:Cell Line; D000939:Epitopes / Q000737:chemistry; D006801:Humans; D066298:In Vitro Techniques; D019169:Jurkat Cells; D008024:Ligands; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D011487:Protein Conformation; D011948:Receptors, Antigen, T-Cell / Q000737:chemistry* / Q000378:metabolism*; D013601:T-Lymphocytes / Q000276:immunology*
D000911:Antibodies, Monoclonal; D017252:CD3 Complex; C115335:CD3E protein, human; C485468:Cd3e protein, mouse; D000939:Epitopes; D008024:Ligands; D011948:Receptors, Antigen, T-Cell