Abstract
Src homology region 2 domain-containing phosphatase 1 (SHP-1) is a key mediator in lymphocyte differentiation, proliferation, and activation. We previously showed that B cell linker protein (BLNK) is a physiological substrate of SHP-1 and that B cell receptor (BCR)-induced activation of c-Jun NH(2)-terminal kinase (JNK) is significantly enhanced in cells expressing a form of SHP-1 lacking phosphatase activity (SHP-1-C/S). In this study, we confirmed that SHP-1 also exerts negative regulatory effects on JNK activation in splenic B cells. To further clarify the role of SHP-1 in B cells, we examined how dephosphorylation of BLNK by SHP-1 affects downstream signaling events. When a BLNK mutant (BLNK Delta N) lacking the NH(2)-terminal region, which contains four tyrosine residues, was introduced in SHP-1-C/S-expressing WEHI-231 cells, the enhanced JNK activation was inhibited. Among candidate proteins likely to regulate JNK activation through BLNK, Nck adaptor protein was found to associate with tyrosine-phosphorylated BLNK and this association was more pronounced in SHP-1-C/S-expressing cells. Furthermore, expression of dominant-negative forms of Nck inhibited BCR-induced JNK activation. Finally, BCR-induced apoptosis was suppressed in SHP-1-C/S-expressing cells and coexpression of Nck SH2 mutants or a dominant-negative form of SEK1 reversed this phenotype. Collectively, these results suggest that SHP-1 acts on BLNK, modulating its association with Nck, which in turn negatively regulates JNK activation but exerts a positive effect on apoptosis.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adaptor Proteins, Signal Transducing
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Adjuvants, Immunologic / physiology
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Animals
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Apoptosis / immunology*
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B-Lymphocytes / cytology
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B-Lymphocytes / enzymology
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B-Lymphocytes / immunology
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B-Lymphocytes / metabolism
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Carrier Proteins / metabolism*
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Carrier Proteins / physiology
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Down-Regulation / immunology
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Enzyme Activation / immunology
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Intracellular Signaling Peptides and Proteins
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JNK Mitogen-Activated Protein Kinases
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Mice
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Mice, Inbred C3H
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Mice, Mutant Strains
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Mitogen-Activated Protein Kinases / metabolism*
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Mitogen-Activated Protein Kinases / physiology
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Oncogene Proteins / metabolism*
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Oncogene Proteins / physiology
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Peptide Fragments / physiology
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Phosphoproteins / metabolism*
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Phosphoproteins / physiology
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Protein Phosphatase 1
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Protein Tyrosine Phosphatase, Non-Receptor Type 6
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Protein Tyrosine Phosphatases / physiology*
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Receptors, Antigen, B-Cell / physiology*
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Spleen / cytology
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Spleen / enzymology
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Spleen / immunology
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Tumor Cells, Cultured / cytology
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Tumor Cells, Cultured / enzymology
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Tumor Cells, Cultured / metabolism
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Up-Regulation / immunology*
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src Homology Domains / immunology*
Substances
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Adaptor Proteins, Signal Transducing
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Adjuvants, Immunologic
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B cell linker protein
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Carrier Proteins
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Intracellular Signaling Peptides and Proteins
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Nck protein
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Oncogene Proteins
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Peptide Fragments
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Phosphoproteins
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Receptors, Antigen, B-Cell
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JNK Mitogen-Activated Protein Kinases
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Mitogen-Activated Protein Kinases
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Protein Phosphatase 1
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Protein Tyrosine Phosphatase, Non-Receptor Type 6
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Protein Tyrosine Phosphatases
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Ptpn6 protein, mouse