title: C3a enhances nerve growth factor-induced NFAT activation and chemokine production in a human mast cell line, HMC-1.
abstract: Activation of cell surface G protein-coupled receptors leads to transphosphorylation and activation of a number of receptor tyrosine kinases. Human mast cells express G protein-coupled receptors for the complement component C3a (C3aR) and high affinity nerve growth factor (NGF) receptor tyrosine kinase, TrkA. To determine whether C3a cross-regulates TrkA signaling and biological responses, we used a human mast cell-line, HMC-1, that natively expresses both receptors. We found that NGF caused tyrosine phosphorylation of TrkA, resulting in a sustained Ca(2+) mobilization, NFAT activation, extracellular-signal regulated kinase (ERK) phosphorylation, and chemokine, macrophage inflammatory protein-1beta (MIP-1beta) production. In contrast, C3a induced a transient Ca(2+) mobilization and ERK phosphorylation but failed to stimulate TrkA phosphorylation, NFAT activation, or MIP-1beta production. Surprisingly, C3a significantly enhanced NGF-induced NFAT activation, ERK phosphorylation, and MIP-1beta production. Pertussis toxin, a G(i/o) inhibitor, selectively blocked priming by C3a but had no effect on NGF-induced responses. Mitogen-activated protein/ERK kinase inhibitor U0126 caused approximately 30% inhibition of NGF-induced MIP-1beta production but had no effect on priming by C3a. However, cyclosporin A, an inhibitor of calcineurin-mediated NFAT activation, caused substantial inhibition of NGF-induced MIP-1beta production both in the absence and presence of C3a. These data demonstrate that NGF caused tyrosine phosphorylation of TrkA to induce chemokine production in HMC-1 cells via a pathway that mainly depends on sustained Ca(2+) mobilization and NFAT activation. Furthermore, C3a enhances NGF-induced transcription factor activation and chemokine production via a G protein-mediated pathway that does not involve TrkA phosphorylation.
authors.affiliation: Department of Pathology, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: Jasimuddin
authors.initials: J
authors.lastname: Ahamed
authors.forename: Rampura T
authors.initials: RT
authors.lastname: Venkatesha
authors.forename: E Berla
authors.initials: EB
authors.lastname: Thangam
authors.forename: Hydar
authors.initials: H
authors.lastname: Ali
mesh_terms: D002118:Calcium / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D018932:Chemokine CCL2; D054407:Chemokine CCL4; D018925:Chemokines / Q000096:biosynthesis*; D015926:Complement C3a / Q000494:pharmacology*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004357:Drug Synergism; D006801:Humans; D019402:Macrophage Inflammatory Proteins / Q000096:biosynthesis; D008407:Mast Cells / Q000187:drug effects* / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D050778:NFATC Transcription Factors; D020932:Nerve Growth Factor / Q000494:pharmacology*; D009687:Nuclear Proteins; D010766:Phosphorylation; D014176:Protein Biosynthesis; D020917:Receptor, trkA; D043562:Receptors, G-Protein-Coupled / Q000502:physiology; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: C111835:CCL2 protein, human; D002352:Carrier Proteins; D018932:Chemokine CCL2; D054407:Chemokine CCL4; D018925:Chemokines; D004268:DNA-Binding Proteins; D019402:Macrophage Inflammatory Proteins; D008565:Membrane Proteins; D016328:NF-kappa B; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D043562:Receptors, G-Protein-Coupled; D014157:Transcription Factors; D015926:Complement C3a; D020932:Nerve Growth Factor; D020917:Receptor, trkA; D020928:Mitogen-Activated Protein Kinases; D002118:Calcium