title: A mouse Fcgamma-Fcepsilon protein that inhibits mast cells through activation of FcgammaRIIB, SH2 domain-containing inositol phosphatase 1, and SH2 domain-containing protein tyrosine phosphatases.
abstract: BACKGROUND
  A human Fcgamma-Fcepsilon fusion protein (GE2) designed to inhibit FcepsilonRI signaling by coaggregating FcepsilonRI with the inhibitory receptor FcgammaRIIB has been shown to inhibit mast cell activation and block cutaneous anaphylaxis. A critical issue remained as to whether the mechanism of GE2 inhibition is competition for IgE binding or inhibitory signaling through FcgammaRIIB.
  
  
  OBJECTIVE
  Our aim was to define the in vitro and in vivo mechanism of action of a mouse homolog of GE2 (mGE) and to assess the potential of human GE2 (hGE2) for therapeutic administration.
  
  
  METHODS
  The in vitro activity of mGE on mediator release and signaling pathways was characterized in IgE-sensitized bone marrow-derived mast cells (BMMCs). The in vivo activity of mGE was examined in mouse passive cutaneous and passive systemic anaphylaxis models, and the therapeutic activity of hGE2 was evaluated in Ascaris suum-sensitized cynomolgus monkeys.
  
  
  RESULTS
  mGE inhibited release of histamine and cytokines by BMMCs from wild-type mice but not by BMMCs from FcgammaRIIB-deficient mice. In mice mGE blocked IgE-dependent anaphylaxis mediated by mast cells with sustained efficacy. In BMMCs mGE decreased spleen tyrosine kinase and extracellular signal-regulated kinases 1/2 phosphorylation and induced FcgammaRIIB phosphorylation and the subsequent recruitment of SH2 domain-containing inositol polyphosphate 5' phosphatase (SHIP) 1 and SH2 domain-containing protein tyrosine phosphatase (SHP) 1/2 phosphatases. When administered therapeutically, hGE2 protected sensitized monkeys from local anaphylaxis for 3 weeks.
  
  
  CONCLUSIONS
  mGE-mediated inhibition of mast cell activation is associated with inhibitory signaling through FcgammaRIIB that results from activation of SHIP-1 and SHP-1/2 phosphatases.
authors.affiliation: Biogen Idec, 5200 Research Place, San Diego, CA 92130, USA. elisabeth.mertsching@biogenidec.com
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Mertsching
authors.forename: Lisa
authors.initials: L
authors.lastname: Bafetti
authors.forename: Henry
authors.initials: H
authors.lastname: Hess
authors.forename: Stuart
authors.initials: S
authors.lastname: Perper
authors.forename: Keith
authors.initials: K
authors.lastname: Giza
authors.forename: Lisa Chan
authors.initials: LC
authors.lastname: Allen
authors.forename: Ella
authors.initials: E
authors.lastname: Negrou
authors.forename: Karen
authors.initials: K
authors.lastname: Hathaway
authors.forename: Jennifer
authors.initials: J
authors.lastname: Hopp
authors.forename: Julie
authors.initials: J
authors.lastname: Chung
authors.forename: Daniel
authors.initials: D
authors.lastname: Perret
authors.forename: Michael
authors.initials: M
authors.lastname: Shields
authors.forename: Andrew
authors.initials: A
authors.lastname: Saxon
authors.forename: Marilyn R
authors.initials: MR
authors.lastname: Kehry
mesh_terms: D000707:Anaphylaxis / Q000517:prevention & control; D000818:Animals; D017165:Ascaris suum; D001854:Bone Marrow Cells / Q000187:drug effects; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006801:Humans; D007114:Immunization; D007073:Immunoglobulin E / Q000378:metabolism; D000072181:Inositol Polyphosphate 5-Phosphatases; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008252:Macaca fascicularis; D008407:Mast Cells / Q000187:drug effects*; D051379:Mice; D008815:Mice, Inbred Strains; D018345:Mice, Knockout; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases; D010744:Phosphoric Monoester Hydrolases / Q000737:chemistry / Q000378:metabolism*; D020033:Protein Isoforms / Q000737:chemistry / Q000378:metabolism; D017027:Protein Tyrosine Phosphatases / Q000737:chemistry / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D017455:Receptors, IgE / Q000378:metabolism; D017452:Receptors, IgG / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000494:pharmacology*; D000072377:Syk Kinase; D051197:Toll-Like Receptor 4 / Q000378:metabolism; D018909:src Homology Domains
chemical_list: C521907:Fc-epsilon receptor I beta-chain, mouse; C499172:Fcgr2b protein, mouse; C527353:GE fusion protein, mouse; C527354:GE2 fusion protein, human; D047908:Intracellular Signaling Peptides and Proteins; D020033:Protein Isoforms; D017455:Receptors, IgE; D017452:Receptors, IgG; D011993:Recombinant Fusion Proteins; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D007073:Immunoglobulin E; D011505:Protein-Tyrosine Kinases; C000606896:SYK protein, human; D000072377:Syk Kinase; C000606897:Syk protein, mouse; D048049:Extracellular Signal-Regulated MAP Kinases; D010744:Phosphoric Monoester Hydrolases; C021822:myo-inositol-1 (or 4)-monophosphatase; D017027:Protein Tyrosine Phosphatases; D000072181:Inositol Polyphosphate 5-Phosphatases; C000606430:INPP5D protein, human; C000606433:Inpp5d protein, mouse; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases