Mechanism of upregulation of the inhibitory regulator, src-like adaptor protein (SLAP), by glucocorticoids in mast cells.
Glucocorticoids suppress mast cell activation by inhibiting signaling events as well as transcription of cytokine genes. The inhibition of signaling events has been attributed to upregulation of inhibitory regulators such as Src-like adaptor protein1 (SLAP), downstream of tyrosine kinase1 (Dok1), and dual specificity protein phospahatase1 (DUSP1). As reported here, the upregulation of SLAP and Dok1, but not DUSP1, in the RBL-2H3 mast cell line was inhibited by actinomycin D and was thus dependent on gene transcription. Examination of the gene sequences revealed a glucocorticoid response element (GRE) and a half GRE as potential regulators of the SLAP and Dok1, respectively. As indicated by luciferase reporter assays, SLAP GRE, but not the Dok1 half GRE, robustly activated gene transcription after treatment of cells with glucocorticoids. Binding of the glucocorticoid receptor to the SLAP GRE was verified by chromatin immunoprecipitation assay. These findings further support the notion that the immunosuppressive actions of glucocorticoids are exerted in part through upregulation of inhibitory regulators by various mechanisms. In the case of SLAP specifically, this requires activation of gene transcription through the interaction of the glucocorticoid receptor with GRE.
Park
Seung-Kiel
SK
Laboratory of Molecular Immunology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892-1760, USA.
Beaven
Michael A
MA
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001483:Base Sequence; D047369:Chromatin Immunoprecipitation; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology*; D054638:Dual Specificity Phosphatase 1 / Q000235:genetics / Q000378:metabolism; D017930:Genes, Reporter; D008024:Ligands; D008156:Luciferases / Q000378:metabolism; D008407:Mast Cells / Q000187:drug effects* / Q000378:metabolism*; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011965:Receptors, Glucocorticoid / Q000378:metabolism; D015203:Reproducibility of Results; D020218:Response Elements / Q000235:genetics; D015854:Up-Regulation / Q000187:drug effects*
D048868:Adaptor Proteins, Signal Transducing; D004268:DNA-Binding Proteins; C499185:Dok1 protein, rat; D008024:Ligands; D010750:Phosphoproteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D011965:Receptors, Glucocorticoid; C490636:Sla protein, rat; D003907:Dexamethasone; D008156:Luciferases; D016392:Proto-Oncogene Proteins pp60(c-src); D054638:Dual Specificity Phosphatase 1; C517021:Dusp1 protein, rat