CD28 and lipid rafts coordinate recruitment of Lck to the immunological synapse of human T lymphocytes.
In T lymphocytes, the Src family kinase Lck associates lipid rafts and accumulates at the immunological synapse (IS) during T cell stimulation by APCs. Using CD4- or CD28-deficient murine T cells, it was suggested that recruitment of Lck to the IS depends on CD4, whereas CD28 sustains Lck activation. However, in human resting T cells, CD28 is responsible for promoting recruitment of lipid rafts to the IS by an unknown mechanism. Thus, we performed a series of experiments to determine 1) whether Lck is recruited to the IS through lipid rafts; and 2) whether Lck recruitment to the IS of human resting T cells depends on CD4 or on CD28 engagement. We found that CD28, but not CD4, stimulation induced recruitment of Lck into detergent-resistant domains as well as its accumulation at the IS. We also found that Lck recruitment to the IS depends on the CD28 COOH-terminal PxxPP motif. Thus, the CD28-3A mutant, generated by substituting the prolines in positions 208, 211, and 212 with alanines, failed to induce Lck and lipid raft accumulation at the synapse. These results indicate that CD28 signaling orchestrates both Lck and lipid raft recruitment to the IS to amplify T cell activation.
Tavano
Regina
R
Venetian Institute of Molecular Medicine and Department of Biomedical Science, University of Padua, Padua, Italy.
Gri
Giorgia
G
Molon
Barbara
B
Marinari
Barbara
B
Rudd
Christopher E
CE
Tuosto
Loretta
L
Viola
Antonella
A
D020816:Amino Acid Motifs; D018106:CD28 Antigens / Q000276:immunology / Q000378:metabolism / Q000502:physiology*; D015704:CD4 Antigens / Q000502:physiology; D002450:Cell Communication / Q000276:immunology; D003902:Detergents; D006801:Humans; D019169:Jurkat Cells; D008213:Lymphocyte Activation / Q000276:immunology*; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000378:metabolism*; D021962:Membrane Microdomains / Q000201:enzymology / Q000276:immunology* / Q000378:metabolism; D015513:Oncogene Proteins / Q000502:physiology; D011485:Protein Binding / Q000276:immunology; D021381:Protein Transport / Q000276:immunology; D051567:Proto-Oncogene Proteins c-vav; D016192:Resting Phase, Cell Cycle / Q000276:immunology; D015398:Signal Transduction / Q000276:immunology; D013601:T-Lymphocytes / Q000201:enzymology* / Q000276:immunology* / Q000378:metabolism
D018106:CD28 Antigens; D015704:CD4 Antigens; D003902:Detergents; D015513:Oncogene Proteins; D051567:Proto-Oncogene Proteins c-vav; C496618:VAV1 protein, human; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck)