| First Author | Stone JD | Year | 1997 |
| Journal | J Immunol | Volume | 158 |
| Issue | 12 | Pages | 5773-82 |
| PubMed ID | 9190928 | Mgi Jnum | J:110662 |
| Mgi Id | MGI:3640858 | Doi | 10.4049/jimmunol.158.12.5773 |
| Citation | Stone JD, et al. (1997) Aberrant TCR-mediated signaling in CD45-null thymocytes involves dysfunctional regulation of Lck, Fyn, TCR-zeta, and ZAP-70. J Immunol 158(12):5773-82 |
| abstractText | CD45 is a transmembrane phosphotyrosine phosphatase expressed on all nucleated hemopoietic cells. Targeting of CD45 exon 9 has generated a mouse line completely lacking CD45 expression (CD45-null) in which there are severe abnormalities in T cell development. Defects in TCR-mediated signals underlying these abnormalities have now been investigated using CD45-null T cells. No T cell proliferation was detected in response to a CD3 mAb. In thymocytes the p56(lck) and p59(fyn) tyrosine kinases were hyperphosphorylated, and p56(lck) was in its inactive conformation. Both basal and TCR-stimulated tyrosine phosphorylation of TCR-zeta and CD3-epsilon were much reduced, and TCR stimulation induced an abnormal p18 phosphoisomer of TCR-zeta previously noted in T cells stimulated by altered peptide ligands. These defects were associated with the failure of ZAP-70 kinase recruitment to the TCR-zeta chain. TCR coupling to the tyrosine phosphorylation of several proteins, including HS1 and p120(cbl), was also much reduced. However, TCR-induced signaling was not ablated, and significant inositol phosphate and calcium signals were observed in CD45-null thymocytes. Our molecular analysis suggests that the threshold for TCR signal transduction is greatly increased in CD45-null T cells, thus explaining the profound defects in thymic development. |
