FcepsilonRI-induced activation by low antigen concentrations results in nuclear signals in the absence of degranulation.
High affinity IgE receptor (FcvarepsilonRI)-induced activation of mast cells results in degranulation and generation of leukotrienes and cytokines. FcvarepsilonRI-induced mast cell activation was analyzed at a single cell basis using a rat basophilic leukemia (RBL-2H3) cell line transfected with a reporter plasmid containing three tandem NFAT (nuclear factor of activated T cells) binding sites fused to enhanced green fluorescent protein (GFP). Surprisingly, with this sensitive detection system, there is activation of IgE sensitized cells at concentrations of antigen as low as 10pg/ml, which was 10-fold lower than was detected by degranulation. There were differences in signaling pathways leading to degranulation compared to NFAT-mediated gene activation. Both signaling to NFAT activation and degranulation required Syk and calcineurin. However inhibitors of the phosphatidylinositol 3-kinase pathway blocked degranulation but did not NFAT activation. The results also indicate that NFAT was activated at lower intracellular signals compared to degranulation. Therefore, FcvarepsilonRI activation can result in nuclear signals in the absence of the release of mediators.
Grodzki
Ana Cristina G
AC
Oral Infection and Immunity Branch, National Institutes of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892, United States.
Moon
Kyungduk D
KD
Berenstein
Elsa H
EH
Siraganian
Reuben P
RP
D000818:Animals; D000941:Antigens / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D015550:Cell Degranulation / Q000187:drug effects; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005434:Flow Cytometry; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D015151:Immunoblotting; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D008407:Mast Cells / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D008856:Microscopy, Fluorescence; D050778:NFATC Transcription Factors / Q000235:genetics / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D017455:Receptors, IgE / Q000502:physiology*; D000072377:Syk Kinase; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D000941:Antigens; D002118:Calcium; D048049:Extracellular Signal-Regulated MAP Kinases; D049452:Green Fluorescent Proteins; D047908:Intracellular Signaling Peptides and Proteins; D050778:NFATC Transcription Factors; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011505:Protein-Tyrosine Kinases; D034741:RNA, Small Interfering; D017455:Receptors, IgE; D000072377:Syk Kinase; D014409:Tumor Necrosis Factor-alpha; C000606898:Syk protein, rat