Regulation of TCR signal transduction in murine thymocytes by multiple TCR zeta-chain signaling motifs.
The alphabeta TCR is a multimeric protein complex comprising ligand-binding and signal-transducing subunits. The signal transduction processes are mediated by the immunoreceptor tyrosine-based activation motifs (ITAMs), and up to 10 ITAMs are present within a single TCR complex. This multiplicity may allow for signal amplification and/or the formation of qualitatively distinct intracellular signals. Notably, the TCR-zeta subunit contains three ITAMs, and exists as a disulfide-linked homodimer in the TCR complex. In normal murine thymocytes and peripheral T cells, a proportion of TCR-zeta molecules is constitutively tyrosine phosphorylated and associated with the ZAP-70 protein tyrosine kinase. We examined the contribution of the different TCR-zeta ITAMs in regulating the constitutive phosphorylation of the TCR-zeta subunit in thymocytes by analyzing TCR-zeta-deficient mice that had been reconstituted with either full-length or single ITAM-containing TCR-zeta subunits. We report in this work that in the absence of a full-length TCR-zeta subunit, there is no apparent constitutive phosphorylation of the remaining TCR/CD3 ITAMs. Following TCR ligation, all of the CD3 ITAMs become inducibly phosphorylated and associate with the ZAP-70 protein tyrosine kinase. Regardless of the number of TCR-zeta ITAMs present in the TCR complex, we report that a number of molecules involved in downstream signaling events, such as ZAP-70, SLP-76, and pp36, are all inducibly tyrosine phosphorylated following TCR ligation. These results support the notion that the different TCR ITAMs function in a quantitative rather than qualitative manner.
van Oers
N S
NS
Howard Hughes Medical Institute, University of California, San Francisco 94143-0724, USA.
Love
P E
PE
Shores
E W
EW
Weiss
A
A
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D005434:Flow Cytometry; D051380:GRB2 Adaptor Protein; D008565:Membrane Proteins / Q000737:chemistry / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000502:physiology; D011505:Protein-Tyrosine Kinases / Q000502:physiology; D011506:Proteins / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000737:chemistry / Q000502:physiology*; D015398:Signal Transduction; D013950:Thymus Gland / Q000166:cytology; D051746:ZAP-70 Protein-Tyrosine Kinase
D048868:Adaptor Proteins, Signal Transducing; D051380:GRB2 Adaptor Protein; C495949:Grb2 protein, mouse; D008565:Membrane Proteins; D010750:Phosphoproteins; D011506:Proteins; D011948:Receptors, Antigen, T-Cell; C054979:antigen T cell receptor, zeta chain; D019000:Phosphotyrosine; D011505:Protein-Tyrosine Kinases; D051746:ZAP-70 Protein-Tyrosine Kinase; C497262:Zap70 protein, mouse