Physical and functional association between thymic shared antigen-1/stem cell antigen-2 and the T cell receptor complex.
Thymic shared antigen-1 (TSA-1)/stem cell Ag-2 (Sca-2) is a glycosylphosphatidylinositol (GPI)-anchored antigen expressed on lymphocytes. We have previously demonstrated that a signal via TSA-1/Sca-2 inhibits T cell receptor (TCR)-mediated T cell activation and apoptosis. To elucidate a molecular mechanism for TSA-1-mediated modulation of the TCR-signaling pathway, we examined whether TSA-1 is physically coupled to the TCR in the present study. TSA-1 was clearly associated with CD3zeta chains in T cell hybridomas, activated T cells, and COS-7 cells transfected with TSA-1 and CD3zeta cDNA. The physical association was confirmed on the surface of T cells in immunoprecipitation and confocal microscopy. The analysis using stable and transient transfectants expressing a transmembrane form of TSA-1 revealed that the association of CD3zeta did not require the GPI anchor of TSA-1. Finally, tyrosine phosphorylation of CD3zeta chains was induced after stimulation with anti-TSA-1, suggesting that a functional association between these two molecules also exists. These results imply that the physical association to CD3zeta underlies a regulatory role of TSA-1/Sca-2 in the TCR-signaling pathway.
Kosugi
A
A
School of Allied Health Sciences, Faculty of Medicine, Osaka University, Osaka 565, Japan. kosugi@sahs.med.osaka-u.ac.jp
Saitoh
S
S
Noda
S
S
Miyake
K
K
Yamashita
Y
Y
Kimoto
M
M
Ogata
M
M
Hamaoka
T
T
D000818:Animals; D017252:CD3 Complex / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D011485:Protein Binding; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D015398:Signal Transduction
D017252:CD3 Complex; D008565:Membrane Proteins; D011948:Receptors, Antigen, T-Cell; C084839:thymic shared antigen-1