title: PMX-53 as a dual CD88 antagonist and an agonist for Mas-related gene 2 (MrgX2) in human mast cells.
abstract: Human mast cells express the G protein coupled receptor (GPCR) for C5a (CD88). Previous studies indicated that C5a could cause mast cell degranulation, at least in part, via a mechanism similar to that proposed for basic neuropeptides such as substance P, possibly involving Mas-related gene 2 (MrgX2). We therefore sought to more clearly define the receptor specificity for C5a-induced mast cell degranulation. We found that LAD2, a human mast cell line, and CD34(+) cell-derived primary mast cells express functional MrgX1 and MrgX2 but the immature human mast cell line HMC-1 does not. A potent CD88 antagonist, PMX-53 (10 nM) inhibited C5a-induced Ca(2+) mobilization in HMC-1 cells, but at higher concentrations (≥30 nM) it caused degranulation in LAD2 mast cells, CD34(+) cell-derived mast cells, and RBL-2H3 cells stably expressing MrgX2. PMX-53 did not, however, activate RBL-2H3 cells expressing MrgX1. Although C5a induced degranulation in LAD2 and CD34(+) cell-derived mast cells, it did not activate RBL-2H3 cells expressing MrgX1 or MrgX2. Replacement of Trp with Ala and Arg with dArg abolished the ability of PMX-53 to inhibit C5a-induced Ca(2+) mobilization in HMC-1 cells and to cause degranulation in RBL-2H3 cells expressing MrgX2. These findings demonstrate that C5a does not use MrgX1 or MrgX2 for mast cell degranulation. Moreover, it reveals the novel finding that PMX-53 functions as a potent CD88 antagonist and a low-affinity agonist for MrgX2. Furthermore, Trp and Arg residues are required for the ability of PMX53 to act as both a CD88 antagonist and a MrgX2 agonist.
authors: Department of Pathology, University of Pennsylvania School of Dental Medicine, Philadelphia, PA 19104-6030, USA.
authors: Hariharan
authors: H
authors: Subramanian
authors: Sakeen W
authors: SW
authors: Kashem
authors: Sarah J
authors: SJ
authors: Collington
authors: Hongchang
authors: H
authors: Qu
authors: John D
authors: JD
authors: Lambris
authors: Hydar
authors: H
authors: Ali
mesh_terms: D002454:Cell Differentiation; D002460:Cell Line; D002478:Cells, Cultured; D015936:Complement C5a / Q000037:antagonists & inhibitors; D006801:Humans; D008407:Mast Cells / Q000187:drug effects*; D009419:Nerve Tissue Proteins / Q000819:agonists*; D010456:Peptides, Cyclic / Q000494:pharmacology*; D044087:Receptor, Anaphylatoxin C5a; D011951:Receptors, Complement / Q000037:antagonists & inhibitors*; D043562:Receptors, G-Protein-Coupled / Q000819:agonists* / Q000378:metabolism; D018013:Receptors, Neuropeptide / Q000819:agonists*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: C438957:AcPhe(ornithine-Pro-cyclohexylamine-Trp-Arg); C488033:C5AR1 protein, human; C480039:MRGPRX2 protein, human; D009419:Nerve Tissue Proteins; D010456:Peptides, Cyclic; D044087:Receptor, Anaphylatoxin C5a; D011951:Receptors, Complement; D043562:Receptors, G-Protein-Coupled; D018013:Receptors, Neuropeptide; D015936:Complement C5a