Negative regulation of Lck by Cbl ubiquitin ligase.
The Cbl-family ubiquitin ligases function as negative regulators of activated receptor tyrosine kinases by facilitating their ubiquitination and subsequent targeting to lysosomes. Cbl associates with the lymphoid-restricted nonreceptor tyrosine kinase Lck, but the functional relevance of this interaction remains unknown. Here, we demonstrate that T cell receptor and CD4 coligation ... on human T cells results in enhanced association between Cbl and Lck, together with Lck ubiquitination and degradation. A Cbl(-/-) T cell line showed a marked deficiency in Lck ubiquitination and increased levels of kinase-active Lck. Coexpression in 293T cells demonstrated that Lck kinase activity and Cbl ubiquitin ligase activity were essential for Lck ubiquitination and negative regulation of Lck-dependent serum response element-luciferase reporter activity. The Lck SH3 domain was pivotal for Cbl-Lck association and Cbl-mediated Lck degradation, with a smaller role for interactions mediated by the Cbl tyrosine kinase-binding domain. Finally, analysis of a ZAP-70-deficient T cell line revealed that Cbl inhibited Lck-dependent mitogen-activated protein kinase activation, and an intact Cbl RING finger domain was required for this functional effect. Our results demonstrate a direct, ubiquitination-dependent, negative regulatory role of Cbl for Lck in T cells, independent of Cbl-mediated regulation of ZAP-70.
Mesh Terms:
Antigens, CD4, Cell Line, Enzyme Activation, Gene Deletion, Genes, Reporter, Humans, Jurkat Cells, Ligases, Lymphocyte Activation, Lymphocyte Specific Protein Tyrosine Kinase p56(lck), Protein Binding, Protein Processing, Post-Translational, Protein Structure, Tertiary, Protein-Tyrosine Kinases, Proto-Oncogene Proteins, Proto-Oncogene Proteins c-cbl, Receptors, Antigen, T-Cell, T-Lymphocytes, Ubiquitin, Ubiquitin-Protein Ligases, ZAP-70 Protein-Tyrosine Kinase, src Homology Domains
Antigens, CD4, Cell Line, Enzyme Activation, Gene Deletion, Genes, Reporter, Humans, Jurkat Cells, Ligases, Lymphocyte Activation, Lymphocyte Specific Protein Tyrosine Kinase p56(lck), Protein Binding, Protein Processing, Post-Translational, Protein Structure, Tertiary, Protein-Tyrosine Kinases, Proto-Oncogene Proteins, Proto-Oncogene Proteins c-cbl, Receptors, Antigen, T-Cell, T-Lymphocytes, Ubiquitin, Ubiquitin-Protein Ligases, ZAP-70 Protein-Tyrosine Kinase, src Homology Domains
Proc. Natl. Acad. Sci. U.S.A.
Date: Mar. 19, 2002
PubMed ID: 11904433
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