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 Ca2+ 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 Ca2+ 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.
Footnotes
This work was supported by National Institutes of Health National Heart, Lung, and Blood Institute [Grant HL085774] and National Institutes of Health National Institute of Allergy and Infectious Diseases [Grant AI068730].
Article, publication date, and citation information can be found at http://molpharm.aspetjournals.org.
doi:10.1124/mol.111.071472.
-
ABBREVIATIONS:
- GPCR
- G protein-coupled receptor
- Mrg
- Mas-related gene
- CBMC
- cord blood-derived mast cell
- PMX-53
- AcPhe(ornithine-Pro-cyclohexylamine-Trp-Arg)
- HA
- hemagglutinin
- CST
- cortistatin-14
- BAM-22P
- bovine adrenal medulla docosapeptide
- rhSCF
- recombinant human stem-cell factor
- IL
- interleukin
- BMMC
- bone marrow-derived mast cells
- RT-PCR
- reverse transcription-polymerase chain reaction
- DNP
- dinitrophenol
- BSA
- bovine serum albumin
- PMX-53S
- scrambled linear PMX-53 peptide
- PMX-53C
- scrambled control PMX-53 peptide
- GPA-2
- G protein antagonist 2 (pGlu-Gln-dTrp-Phe-dTrp-dTrp-Met-NH2)
- PTx
- pertussis toxin
- ANOVA
- analysis of variance
- Indo-1AM
- 2[4-(bis(carboxymethyl)amino)-3-[2-[2-(bis(carboxymethyl)amino)-5-methylphenoxy]ethoxy]phenyl]-1H-indole-6-carboxylic acid, acetoxymethyl ester
- C5aP
- C5a peptide.
- Received January 28, 2011.
- Accepted March 11, 2011.
- Copyright © 2011 The American Society for Pharmacology and Experimental Therapeutics
MolPharm articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|