T cell-to-T cell clustering enhances NF-kappaB activity by a PI3K signal mediated by Cbl-b and Rho.
Full activation of T cells requires the binding of antigen to the T cell receptor and stimulation of the CD28 molecule, a process which typically occurs when T cells bind to an antigen presenting cell. The transcription factor, NF-kappaB, is an integration point for these two signals and its activation is critical for T cell function. Using antibodies to the TCR and CD28 molecules to activate Jurkat T cells, we show that cells that were permitted to aggregate into multi-cellular clusters increased NF-kappaB activity compared to unclustered cells. Inhibition of PI3K signaling with wortmannin decreased the clustering-mediated NF-kappaB signal. Over-expression of a dominant negative form of Cbl-b, an endogenous inhibitor of PI3K, in unclustered cells rescued NF-kappaB activation to the same levels caused by cell clustering. Inhibiting signaling through Rho with dominant negative RhoA abrogated both clustering-mediated and dominant negative Cbl-b-mediated NF-kappaB inactivation, but not TCR/CD28 mediated NF-kappaB activation. Taken together, these results suggest that in addition to pathways stimulated by classical T cell-APC interactions, another signal arising from T cell clustering can enhance activation.
Herndon
Thomas M
TM
Department of Biomedical Engineering, Johns Hopkins School of Medicine, Baltimore, MD 21205, USA.
Pirone
Dana M
DM
Tsokos
George C
GC
Chen
Christopher S
CS
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D018106:CD28 Antigens / Q000096:biosynthesis*; D002450:Cell Communication; D016000:Cluster Analysis; D005799:Genes, Dominant; D017930:Genes, Reporter; D006801:Humans; D007249:Inflammation; D019169:Jurkat Cells; D008156:Luciferases / Q000378:metabolism; D008954:Models, Biological; D016328:NF-kappa B / Q000378:metabolism*; D050722:Oncogene Protein v-cbl; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D050721:Proto-Oncogene Proteins c-cbl; D015682:Retroviridae Proteins, Oncogenic / Q000378:metabolism*; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000378:metabolism*; D014162:Transfection; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; D018106:CD28 Antigens; D016328:NF-kappa B; D050722:Oncogene Protein v-cbl; D015682:Retroviridae Proteins, Oncogenic; D008156:Luciferases; C492211:CBLB protein, human; D050721:Proto-Oncogene Proteins c-cbl; D044767:Ubiquitin-Protein Ligases; D019869:Phosphatidylinositol 3-Kinases; D020741:rho GTP-Binding Proteins