Gi-independent macrophage chemotaxis to lysophosphatidylcholine via the immunoregulatory GPCR G2A

Abstract

G2A is a G-protein–coupled receptor (GPCR) involved in immune regulation. Previous studies have shown that lysophosphatidylcholine (LPC), a bioactive lipid associated with atherosclerosis and autoimmunity, acts through G2A to induce diverse biologic effects. Production of LPC during cell apoptosis serves as a chemotactic signal for macrophage recruitment. Here we demonstrate that macrophage chemotaxis to LPC is dependent on G2A function. Wild-type but not G2A-deficient mouse peritoneal macrophages migrated toward LPC. RNAi-mediated knockdown of G2A in J774A.1 macrophages abolished LPC-induced chemotaxis, whereas overexpression of G2A significantly enhanced this process. Mutation of the conserved DRY motif of G2A resulted in loss of chemotaxis to LPC, suggesting a requirement for G-protein signaling. Unlike most GPCRs, including the chemokine receptors, coupling to Gi is not required for LPC/G2A-mediated chemotaxis, but coupling to Gq/11 and G12/13 is necessary as judged by inhibition with dominant negative forms of these alpha subunits or with regulators of G-protein signaling (RGS) constructs. Collectively, these data establish that pertussis toxin–insensitive G2A signaling regulates macrophage chemotaxis to LPC. Defects in this signaling pathway may be related to the pathogenesis of systemic autoimmune disease.

Lysophosphatidylcholine suppresses apoptosis and induces neurite outgrowth in PC12 cells through activation of phospholipase D2

“…Indeed, several G protein-coupled receptors, including G2A and GPR4, have been reported to bind to LPC (Xu, 2002;Meyer zu Heringdorf et al, 2002). LPC induces chemotaxis of macrophages through activation of G2A (Yang et al, 2005), and anti-G2A antibody attenuates protective Figure 4. Effects of LPC-stimulated PLD2 activity on the serum starvation-induced apoptosis in PC12 cells.…”

Functional metagenomic discovery of bacterial effectors in the human microbiome and isolation of commendamide, a GPCR G2A/132 agonist

“…G2A-knockout mice have increased susceptibility to atherosclerosis and develop late-onset autoimmunity (31). These phenotypes are thought to arise from disruption of G2A-dependent modulation of immune cell function including differentiation and chemotaxis (62,(64)(65)(66)(67)(68)(69)(70)(71). This suggests that Bacteroides spp.…”

NADPH Oxidase-dependent Generation of Lysophosphatidylserine Enhances Clearance of Activated and Dying Neutrophils via G2A

“…Macrophage G2A Signaling-We have recently reported that lyso-PS can signal through the G proteincoupled receptor, G2A, for calcium flux (20), and G2A has been recently described as a receptor on macrophages responsible for mediating macrophage chemotactic responses (50,51). Accordingly, G2A appeared to be a reasonable candidate for lyso-PS-dependent enhancement of apoptotic cell engulfment.…”