G protein coupled receptor specificity for C3a and compound 48/80-induced degranulation in human mast cells: Roles of Mas-related genes MrgX1 and MrgX2

Abstract

Although human mast cells express G protein coupled receptors for the anaphylatoxin C3a, previous studies indicated that C3a causes mast cell degranulation, at least in part, via a C3a receptor-independent mechanism similar to that proposed for polycationic molecules such as compound 48/80. The purpose of the present study was to delineate the receptor specificity of C3a-induced degranulation in human mast cells. We found that C3a, a C3a receptor “superagonist” (E7) and compound 48/80 induced Ca2+ mobilization and degranulation in a differentiated human mast cell line, LAD2. However, C3a and E7 caused Ca2+ mobilization in an immature mast cell line, HMC-1 but compound 48/80 did not. We have previously shown that LAD2 cells express MrgX1 and MrgX2 but HMC-1 cells do not. To delineate the receptor specificity for C3a and compound 48/80 further, we generated stable transfectants expressing MrgX1 and MrgX2 in a rodent mast cell line, RBL-2H3 cells. We found that compound 48/80 caused degranulation in RBL-2H3 cells expressing MrgX1 and MrgX2 but C3a did not. By contrast, E7 activated RBL-2H3 cells expressing MrgX2 but not MrgX1. These findings demonstrate that in contrast to previous reports, C3a and compound 48/80 do not use a shared mechanism for mast cell degranulation. It shows that while compound 48/80 utilizes MrgX1 and MrgX2 for mast cell degranulation C3a does not. It further reveals the novel finding that the previously characterized synthetic peptide, C3a receptor “superagonist” E7 activates human mast cells via two mechanisms; one involving the C3a receptor and the other MrgX2.

International Union of Basic and Clinical Pharmacology. XCIX. Angiotensin Receptors: Interpreters of Pathophysiological Angiotensinergic Stimuli

“…MAS shares significant similarity with Mas-related G-protein-coupled receptors or paralogs, which are predominantly expressed in State of the Angiotensin Receptors neurons and immune cells (Young et al, 1986;Dong et al, 2001;Bender et al, 2002). MAS might be expected to respond to physiologic ligands, which are typically neuropeptides and pro-or anti-inflammatory ligands (Dong et al, 2001;Lembo et al, 2002;Choi and Lahn, 2003;Tatemoto et al, 2006;Liu et al, 2009;Kashem et al, 2011;Subramanian et al, 2011;Han et al, 2013). Therefore, the role of MAS as the receptor for only Ang(1-7) qualifying it as an integral constituent of the RAS is unclear.…”

The role of P2Y14 and other P2Y receptors in degranulation of human LAD2 mast cells

“…Activation of C3a and S1P (sphingosine-1-phosphate) receptors could induce degranulation directly [22][23][24]. However, adenosine and prostaglandin E2 (PGE2) alone could not induce degranulation, but they enhanced antigen-induced mast cell degranulation via the A 3 AR and EP3 prostanoid receptor, respectively [1,5].…”

Mas-related Gene X2 (MrgX2) Is a Novel G Protein-coupled Receptor for the Antimicrobial Peptide LL-37 in Human Mast Cells

“…4A). In addition to MrgX2, human mast cells express MrgX1 (27,36). To determine the specificity of LL-37 for MrgX2, we also utilized RBL-2H3 cells stably expressing MrgX1 (36).…”

“…Stable Transfection of RBL-2H3 and HMC-1 Cells-RBL-2H3 cells stably expressing MrgX1 and MrgX2 were generated as described previously (27,36). For HMC-1 cells, 2 ϫ 10 6 cells were transfected with plasmids encoding HA-tagged MrgX2 using the Amaxa nucleofector device and Amaxa kit V according to the manufacturer's protocol.…”