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

Blood. 2005 Feb 1;105(3):1127-34. doi: 10.1182/blood-2004-05-1916. Epub 2004 Sep 21.

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 G(i) is not required for LPC/G2A-mediated chemotaxis, but coupling to G(q/11) and G(12/13) 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Base Sequence
  • Cell Cycle Proteins / drug effects
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / physiology*
  • Cell Line
  • Chemotaxis / drug effects
  • Chemotaxis / physiology*
  • DNA Primers
  • Gene Expression Regulation
  • Lysophosphatidylcholines / pharmacology*
  • Macrophages / drug effects
  • Macrophages / physiology*
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • RNA, Small Interfering / genetics
  • Receptors, G-Protein-Coupled / deficiency
  • Receptors, G-Protein-Coupled / drug effects
  • Receptors, G-Protein-Coupled / genetics
  • Receptors, G-Protein-Coupled / physiology*
  • Reverse Transcriptase Polymerase Chain Reaction

Substances

  • Cell Cycle Proteins
  • DNA Primers
  • G2A receptor
  • Lysophosphatidylcholines
  • RNA, Small Interfering
  • Receptors, G-Protein-Coupled