title: Transmembrane adaptor protein PAG/CBP is involved in both positive and negative regulation of mast cell signaling.
abstract: The transmembrane adaptor protein PAG/CBP (here, PAG) is expressed in multiple cell types. Tyrosine-phosphorylated PAG serves as an anchor for C-terminal SRC kinase, an inhibitor of SRC-family kinases. The role of PAG as a negative regulator of immunoreceptor signaling has been examined in several model systems, but no functions in vivo have been determined. Here, we examined the activation of bone marrow-derived mast cells (BMMCs) with PAG knockout and PAG knockdown and the corresponding controls. Our data show that PAG-deficient BMMCs exhibit impaired antigen-induced degranulation, extracellular calcium uptake, tyrosine phosphorylation of several key signaling proteins (including the high-affinity IgE receptor subunits, spleen tyrosine kinase, and phospholipase C), production of several cytokines and chemokines, and chemotaxis. The enzymatic activities of the LYN and FYN kinases were increased in nonactivated cells, suggesting the involvement of a LYN- and/or a FYN-dependent negative regulatory loop. When BMMCs from PAG-knockout mice were activated via the KIT receptor, enhanced degranulation and tyrosine phosphorylation of the receptor were observed. In vivo experiments showed that PAG is a positive regulator of passive systemic anaphylaxis. The combined data indicate that PAG can function as both a positive and a negative regulator of mast cell signaling, depending upon the signaling pathway involved.
authors.affiliation: Department of Signal Transduction, Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
authors.forename: Lubica
authors.initials: L
authors.lastname: Draberova
authors.affiliation: Department of Signal Transduction, Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
authors.forename: Viktor
authors.initials: V
authors.lastname: Bugajev
authors.affiliation: Department of Signal Transduction, Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
authors.forename: Lucie
authors.initials: L
authors.lastname: Potuckova
authors.affiliation: Department of Signal Transduction, Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
authors.forename: Ivana
authors.initials: I
authors.lastname: Halova
authors.affiliation: Department of Signal Transduction, Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
authors.forename: Monika
authors.initials: M
authors.lastname: Bambouskova
authors.affiliation: Department of Signal Transduction, Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
authors.forename: Iva
authors.initials: I
authors.lastname: Polakovicova
authors.affiliation: Center for Computational and Integrative Biology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA Broad Institute of Harvard University and Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.
authors.forename: Ramnik J
authors.initials: RJ
authors.lastname: Xavier
authors.affiliation: Center for Computational and Integrative Biology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Brian
authors.initials: B
authors.lastname: Seed
authors.affiliation: Department of Signal Transduction, Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic draberpe@img.cas.cz.
authors.forename: Petr
authors.initials: P
authors.lastname: Draber
mesh_terms: D000707:Anaphylaxis / Q000235:genetics*; D000818:Animals; D001854:Bone Marrow Cells / Q000378:metabolism / Q000502:physiology; D000081247:CSK Tyrosine-Protein Kinase; D002118:Calcium / Q000378:metabolism; D015550:Cell Degranulation; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008407:Mast Cells / Q000378:metabolism* / Q000502:physiology; D008565:Membrane Proteins / Q000235:genetics*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010750:Phosphoproteins / Q000235:genetics*; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D051076:Proto-Oncogene Proteins c-fyn / Q000096:biosynthesis; D019009:Proto-Oncogene Proteins c-kit / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering; D017455:Receptors, IgE / Q000378:metabolism; D015398:Signal Transduction; D000072377:Syk Kinase; D010738:Type C Phospholipases / Q000378:metabolism; D019061:src-Family Kinases / Q000096:biosynthesis / Q000378:metabolism*
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C498709:Pag1 protein, mouse; D010750:Phosphoproteins; D034741:RNA, Small Interfering; D017455:Receptors, IgE; D011505:Protein-Tyrosine Kinases; D019009:Proto-Oncogene Proteins c-kit; D000081247:CSK Tyrosine-Protein Kinase; C494960:Fyn protein, mouse; D051076:Proto-Oncogene Proteins c-fyn; D000072377:Syk Kinase; C000606897:Syk protein, mouse; C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases; D010738:Type C Phospholipases; D002118:Calcium