title: Protein tyrosine phosphatase epsilon is a negative regulator of FcepsilonRI-mediated mast cell responses.
abstract: Modulation of mast-cell activation may provide novel ways to control allergic diseases. Here, we show that protein tyrosine phosphatase epsilon (PTPepsilon; Ptpre) plays key regulatory roles during mast-cell activation mediated by the high-affinity IgE receptor (FcepsilonRI). Bone marrow-derived mast cells (BMMC) from Ptpre(-/-) mice exhibited enhanced FcepsilonRI-induced Ca(2+) mobilization and mitogen-activated protein kinase (MAPK) (JNK and p38) activation, and showed corresponding enhancement of evoked degranulation and cytokine production, but not leukotriene production. Examination of proteins linking tyrosine kinase activation and Ca(2+) mobilization revealed that the absence of PTPepsilon leads to increased phosphorylation of the linker for activation of T cells and SH2 domain-containing leucocyte phosphoproteins of 76 kDa, but not Grb2-associated binder-2 (Gab2). Because Gab2 is considered to be situated downstream of Fyn kinase, we reasoned that Fyn may not be a target of PTPepsilon. In the event, Syk but not Lyn was hyperphosphorylated in PTPepsilon-deficient BMMC. Thus, PTPepsilon most likely exerts its effects at the level of Syk, inhibiting downstream events including phosphorylation of SLP-76 and linker of activated T cells and mobilization of Ca(2+). Consistent with the in vitro data, antigen- and IgE-mediated passive systemic anaphylactic reactions were augmented in Ptpre(-/-) mice. Given that the number of mast cells is unchanged in these mice, this observation most likely reflects alterations of mast cell-autonomous signalling events. These data suggest that PTPepsilon negatively regulates FcepsilonRI-mediated signalling pathways and thus constitutes a novel target for ameliorating allergic conditions.
authors.affiliation: Department of Immunology and Signal Transduction, Tokyo Metropolitan Institute for Neuroscience, Tokyo Metropolitan Organization for Medical Research, Fuchu, Tokyo, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Akimoto
authors.forename: K
authors.initials: K
authors.lastname: Mishra
authors.forename: K-T
authors.initials: KT
authors.lastname: Lim
authors.forename: N
authors.initials: N
authors.lastname: Tani
authors.forename: S-I
authors.initials: SI
authors.lastname: Hisanaga
authors.forename: T
authors.initials: T
authors.lastname: Katagiri
authors.forename: A
authors.initials: A
authors.lastname: Elson
authors.forename: K
authors.initials: K
authors.lastname: Mizuno
authors.forename: H
authors.initials: H
authors.lastname: Yakura
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000707:Anaphylaxis / Q000276:immunology; D000818:Animals; D015153:Blotting, Western; D001854:Bone Marrow Cells / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D015550:Cell Degranulation / Q000187:drug effects / Q000276:immunology; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007073:Immunoglobulin E / Q000276:immunology / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D015289:Leukotrienes / Q000378:metabolism; D008407:Mast Cells / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D019009:Proto-Oncogene Proteins c-kit / Q000378:metabolism; D054630:Receptor-Like Protein Tyrosine Phosphatases, Class 4 / Q000235:genetics / Q000378:metabolism*; D017455:Receptors, IgE / Q000378:metabolism*; D000072377:Syk Kinase; D014443:Tyrosine / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism; D019061:src-Family Kinases / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D016207:Cytokines; C521907:Fc-epsilon receptor I beta-chain, mouse; C490894:Gab2 protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; C491734:Lat protein, mouse; D015289:Leukotrienes; D008565:Membrane Proteins; D010750:Phosphoproteins; D017455:Receptors, IgE; D007073:Immunoglobulin E; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D019009:Proto-Oncogene Proteins c-kit; C000606896:SYK protein, human; D000072377:Syk Kinase; C000606897:Syk protein, mouse; C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C098067:Ptpre protein, mouse; D054630:Receptor-Like Protein Tyrosine Phosphatases, Class 4; D002118:Calcium