PMID:2118992

Citation	Luo, KX and Sefton, BM (1990) Cross-linking of T-cell surface molecules CD4 and CD8 stimulates phosphorylation of the lck tyrosine protein kinase at the autophosphorylation site. Mol. Cell. Biol. 10:5305-13
Abstract	p56lck, a lymphocyte-specific tyrosine protein kinase, binds to the cytoplasmic tails of the T-cell surface molecules CD4 and CD8. Cross-linking of CD4 expressed on the surface of murine thymocytes, splenocytes, and CD4+ T-cell lines induced tyrosine phosphorylation of p56lck dramatically. Cross-linking of CD8 stimulated tyrosine phosphorylation of p56lck strongly in murine L3 and GA4 cells, slightly in splenocytes, but not detectably in thymocytes. Differing effects of cross-linking on in vitro tyrosine kinase activity of p56lck were observed. An increase in the in vitro kinase activity of p56lck, when assayed with [Val5]-angiotensin II as an exogenous substrate, was found to accompany cross-linking of CD4 in three cell lines. No stimulation of the in vitro kinase activity, however, was observed after cross-linking of CD8 in L3 cells. The phosphorylation of p56lck at Tyr-394, the autophosphorylation site, was stimulated by cross-linking in all cell lines examined. Tyr-394 was the predominant site of increased tyrosine phosphorylation in two leukemic cell lines. In the other two cell lines, the phosphorylation of both Tyr-394 and an inhibitory site, Tyr-505, was found to increase. In contrast to cross-linking with antibodies, no striking increase in the tyrosine phosphorylation of p56lck was stimulated by antigenic stimulation. Therefore, the effect of antibody-induced aggregation of CD4 and CD8 on the tyrosine phosphorylation of p56lck differs, at least quantitatively, from what occurs during antigen-induced T-cell activation.
Links	PubMed PMC361220
Keywords	Animals; Antigens, CD4/physiology; Antigens, CD8; Antigens, Differentiation, T-Lymphocyte/physiology; Blotting, Western; Cell Line; Cross-Linking Reagents; Lymphocyte Specific Protein Tyrosine Kinase p56(lck); Mice; Molecular Weight; Peptide Mapping; Phosphorylation; Protein-Tyrosine Kinases/metabolism; Receptor Aggregation; Signal Transduction; Spleen/cytology; T-Lymphocytes/physiology
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
HUMAN:CD4	involved_in	GO:0045860: positive regulation of protein kinase activity	ECO:0000314: direct assay evidence used in manual assertion		P		Seeded From UniProt	complete

References

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