title: Distinct roles of Ca2+ mobilization and G protein usage on regulation of Toll-like receptor function in human and murine mast cells.
abstract: Toll-like receptors (TLRs) expressed in mast cells play important roles in orchestrating host defence against bacterial pathogens. Previous studies demonstrated that TLR2 agonist tripalmitoyl-S-glycero-Cys-(Lys)4 (Pam3Cys) stimulates both degranulation and cytokine production in human mast cells but only induces cytokine production in murine mast cells. To determine the molecular basis for this difference, we utilized a human mast cell line LAD 2, murine lung and bone marrow-derived mast cells (MLMC and BMMC). We found that Pam3Cys caused a sustained Ca2+ mobilization and degranulation in LAD 2 mast cells but not in MLMC or BMMC. Despite these differences, Pam3Cys stimulated equivalent chemokine CCL2 generation in all mast cell types tested. Cyclosporin A (CsA), an inhibitor of Ca2+/calcineurin-mediated nuclear factor of activated T cells (NFAT) activation, blocked chemokine production in LAD 2 but not in MLMC or BMMC. In contrast, inhibitors of nuclear factor kappa B (NF-kappaB) completely blocked CCL2 production in MLMC and BMMC but not in LAD 2 mast cells. Pertussis toxin and U0126, which, respectively, inhibit Galphai, extracellular signal-regulated kinase (ERK) phosphorylation substantially inhibited Pam3Cys-induced CCL2 generation in LAD 2 mast cells but had little or no effect on chemokine generation in MLMC and BMMC. These findings suggest that TLR2 activation in human LAD 2 mast cells and MLMC/BMMC promotes the release of different classes of mediators via distinct signalling pathways that depend on Ca2+ mobilization and G protein usage.
authors.affiliation: Department of Pathology, University of Pennsylvania, School of Dental Medicine, Philadelphia, PA 19104, USA.
authors.forename: Asifa K
authors.initials: AK
authors.lastname: Zaidi
authors.forename: Elden Retna Raj B
authors.initials: ER
authors.lastname: Thangam
authors.forename: Hydar
authors.initials: H
authors.lastname: Ali
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015550:Cell Degranulation; D002478:Cells, Cultured; D018925:Chemokines / Q000096:biosynthesis; D003545:Cysteine / Q000031:analogs & derivatives / Q000494:pharmacology; D016207:Cytokines / Q000096:biosynthesis; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D008407:Mast Cells / Q000378:metabolism*; D051379:Mice; D016328:NF-kappa B / Q000502:physiology; D050778:NFATC Transcription Factors / Q000502:physiology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D013045:Species Specificity; D051195:Toll-Like Receptor 2 / Q000819:agonists; D051193:Toll-Like Receptors / Q000502:physiology*
chemical_list: D018925:Chemokines; D016207:Cytokines; D016328:NF-kappa B; D050778:NFATC Transcription Factors; C495342:TLR2 protein, human; D051195:Toll-Like Receptor 2; D051193:Toll-Like Receptors; C038837:tripalmitoyl cysteine; D019869:Phosphatidylinositol 3-Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D019204:GTP-Binding Proteins; D003545:Cysteine; D002118:Calcium