Thy-1/CD3 coengagement promotes TCR signaling and enhances particularly tyrosine phosphorylation of the raft molecule LAT.
Mol Immunol
; 36(11-12): 755-68, 1999 Aug.
Article
em En
| MEDLINE
| ID: mdl-10593514
ABSTRACT
Clustering of the glycosyl-phosphatidylinositol (GPI)-anchored protein Thy-1 on the cell surface leads to T cell activation. However, despite the similarity to TCR-mediated events, cell signaling triggered by Thy-1 crosslinking, reportedly occurs in a manner independent of the TCR/CD3 complex. To investigate the relationship between responses resulting from Thy-1 or TCR engagement, a biochemically well defined system employing only affinity purified antibodies was used to crosslink these surface molecules and activation was assessed by monitoring tyrosine phosphorylation, intracellular calcium influx and IL-2 production. By these criteria, anti-CD3 mAbs moderately activated EL-4 thymoma or 2B4 hybridoma cell lines, while costimulation with anti-Thy-1-mAb strongly enhanced TCR signaling. Furthermore, a Thy-1 loss mutant cell line, did not respond to stimulation through CD3 despite expressing all essential signaling molecules. Together these results emphasized the existence of a poorly appreciated mutual interdependence between Thy-1 and CD3 for efficient cellular signaling. Thy-1/CD3-mediated activation enhanced mostly tyrosine phosphorylation of a 40 kDa protein which was identified as a transmembrane protein lacking N-linked oligosaccharides. These biochemical properties are identical to those described for a recently cloned adaptor protein called 'Linker for Activation of T cells' (LAT). Indeed, polyclonal Abs raised against a LAT-peptide (amino acids 103-131) specifically recognized the 40 kDa protein. LAT is present in microdomains of the plasma membrane enriched in sphingolipids, cholesterol, GPI-anchored proteins and a variety of signaling molecules. By contrast, the TCR/CD3 complex is excluded from these domains at least until stimulation takes place. Hence, we propose that Thy-1 promotes TCR/CD3 dependent signaling by facilitating LAT phosphorylation on tyrosine and the subsequent recruitment of downstream effector molecules.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Fosfoproteínas
/
Receptores de Antígenos de Linfócitos T
/
Proteínas de Transporte
/
Complexo CD3
/
Antígenos Thy-1
/
Proteínas Adaptadoras de Transdução de Sinal
/
Proteínas de Membrana
Tipo de estudo:
Prognostic_studies
Limite:
Animals
Idioma:
En
Ano de publicação:
1999
Tipo de documento:
Article