Abstract
Triggering of mast cells and basophils by IgE and Ag initiates a cascade of biochemical events that lead to cell degranulation and the release of allergic mediators. Receptor aggregation also induces a series of biochemical events capable of limiting FcepsilonRI-triggered signals and functional responses. Relevant to this, we have recently demonstrated that Cbl-interacting 85-kDa protein (CIN85), a multiadaptor protein mainly involved in the process of endocytosis and vesicle trafficking, regulates the Ag-dependent endocytosis of the IgE receptor, with consequent impairment of FcepsilonRI-mediated cell degranulation. The purpose of this study was to further investigate whether CIN85 could alter the FcepsilonRI-mediated signaling by affecting the activity and/or expression of molecules directly implicated in signal propagation. We found that CIN85 overexpression inhibits the FcepsilonRI-induced tyrosine phosphorylation of phospholipase Cgamma, thus altering calcium mobilization. This functional defect is associated with a substantial decrease of Syk protein levels, which are restored by the use of selective proteasome inhibitors, and it is mainly due to the action of the ubiquitin ligase c-Cbl. Furthermore, coimmunoprecipitation experiments demonstrate that CIN85 overexpression limits the ability of Cbl to bind suppressor of TCR signaling 1 (Sts1), a negative regulator of Cbl functions, while CIN85 knockdown favors the formation of Cbl/Sts1 complexes. Altogether, our findings support a new role for CIN85 in regulating Syk protein levels in RBL-2H3 cells through the activation of the ubiquitin-proteasome pathway and provide a mechanism for this regulation involving c-Cbl ligase activity.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adaptor Proteins, Signal Transducing / genetics
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Adaptor Proteins, Signal Transducing / immunology
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Adaptor Proteins, Signal Transducing / metabolism*
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Animals
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Antigens / immunology
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Antigens / metabolism
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Basophils / immunology
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Basophils / metabolism
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Calcium Signaling / genetics
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Calcium Signaling / immunology
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Cell Degranulation / genetics
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Cell Degranulation / immunology
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Cell Line
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Endocytosis / genetics
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Endocytosis / immunology
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Gene Expression
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Humans
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Immunoglobulin A / immunology
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Immunoglobulin A / metabolism
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Intracellular Signaling Peptides and Proteins / genetics
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Intracellular Signaling Peptides and Proteins / immunology
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Intracellular Signaling Peptides and Proteins / metabolism*
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Mast Cells / immunology
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Mast Cells / metabolism
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Neoplasm Proteins / genetics
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Neoplasm Proteins / immunology
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Neoplasm Proteins / metabolism*
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Nerve Tissue Proteins / genetics
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Nerve Tissue Proteins / immunology
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Nerve Tissue Proteins / metabolism*
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Phospholipase C gamma
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Phosphorylation
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Proteasome Endopeptidase Complex / genetics
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Proteasome Endopeptidase Complex / immunology
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Proteasome Endopeptidase Complex / metabolism*
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Protein-Tyrosine Kinases / genetics
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Protein-Tyrosine Kinases / immunology
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Protein-Tyrosine Kinases / metabolism*
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Proto-Oncogene Proteins c-cbl / genetics
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Proto-Oncogene Proteins c-cbl / immunology
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Proto-Oncogene Proteins c-cbl / metabolism
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Rats
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Receptors, Antigen, T-Cell / genetics
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Receptors, Antigen, T-Cell / immunology
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Receptors, Antigen, T-Cell / metabolism
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Receptors, IgE / genetics
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Receptors, IgE / immunology
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Receptors, IgE / metabolism
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Syk Kinase
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Ubiquitin / genetics
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Ubiquitin / immunology
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Ubiquitin / metabolism*
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Ubiquitin-Protein Ligases / genetics
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Ubiquitin-Protein Ligases / immunology
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Ubiquitin-Protein Ligases / metabolism
Substances
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Adaptor Proteins, Signal Transducing
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Antigens
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Immunoglobulin A
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Intracellular Signaling Peptides and Proteins
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Neoplasm Proteins
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Nerve Tissue Proteins
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Receptors, Antigen, T-Cell
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Receptors, IgE
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SH3KBP1 protein, human
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Sh3kbp1 protein, rat
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Ubiquitin
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Proto-Oncogene Proteins c-cbl
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Ubiquitin-Protein Ligases
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Protein-Tyrosine Kinases
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SYK protein, human
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Syk Kinase
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Syk protein, rat
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Phospholipase C gamma
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Proteasome Endopeptidase Complex
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CBL protein, human