title: Src homology region 2 domain-containing phosphatase 1 positively regulates B cell receptor-induced apoptosis by modulating association of B cell linker protein with Nck and activation of c-Jun NH2-terminal kinase.
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.
authors.affiliation: Department of Immunology and Signal Transduction, Tokyo Metropolitan Institute for Neuroscience, Tokyo Metropolitan Organization for Medical Science, Tokyo Metropolitan University, Tokyo, Japan.
authors.forename: Kazuya
authors.initials: K
authors.lastname: Mizuno
authors.forename: Yuko
authors.initials: Y
authors.lastname: Tagawa
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Mitomo
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Watanabe
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Katagiri
authors.forename: Mami
authors.initials: M
authors.lastname: Ogimoto
authors.forename: Hidetaka
authors.initials: H
authors.lastname: Yakura
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000276:Adjuvants, Immunologic / Q000502:physiology; D000818:Animals; D017209:Apoptosis / Q000276:immunology*; D001402:B-Lymphocytes / Q000166:cytology / Q000201:enzymology / Q000276:immunology / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism* / Q000502:physiology; D015536:Down-Regulation / Q000276:immunology; D004789:Enzyme Activation / Q000276:immunology; D047908:Intracellular Signaling Peptides and Proteins; D048031:JNK Mitogen-Activated Protein Kinases; D051379:Mice; D008809:Mice, Inbred C3H; D008817:Mice, Mutant Strains; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism* / Q000502:physiology; D015513:Oncogene Proteins / Q000378:metabolism* / Q000502:physiology; D010446:Peptide Fragments / Q000502:physiology; D010750:Phosphoproteins / Q000378:metabolism* / Q000502:physiology; D054645:Protein Phosphatase 1; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000502:physiology*; D011947:Receptors, Antigen, B-Cell / Q000502:physiology*; D013154:Spleen / Q000166:cytology / Q000201:enzymology / Q000276:immunology; D014407:Tumor Cells, Cultured / Q000166:cytology / Q000201:enzymology / Q000378:metabolism; D015854:Up-Regulation / Q000276:immunology*; D018909:src Homology Domains / Q000276:immunology*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000276:Adjuvants, Immunologic; C113939:B cell linker protein; D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; C078332:Nck protein; D015513:Oncogene Proteins; D010446:Peptide Fragments; D010750:Phosphoproteins; D011947:Receptors, Antigen, B-Cell; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D054645:Protein Phosphatase 1; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases; C509248:Ptpn6 protein, mouse