title: 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 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.
authors.affiliation: Howard Hughes Medical Institute, Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, 675 Charles E. Young Dr South, 5-748 MRL, Los Angeles, CA 90095-1662, USA.
authors.forename: Li V
authors.initials: LV
authors.lastname: Yang
authors.forename: Caius G
authors.initials: CG
authors.lastname: Radu
authors.forename: Li
authors.initials: L
authors.lastname: Wang
authors.forename: Mireille
authors.initials: M
authors.lastname: Riedinger
authors.forename: Owen N
authors.initials: ON
authors.lastname: Witte
mesh_terms: D000818:Animals; D001483:Base Sequence; D018797:Cell Cycle Proteins / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D002460:Cell Line; D002633:Chemotaxis / Q000187:drug effects / Q000502:physiology*; D017931:DNA Primers; D005786:Gene Expression Regulation; D008244:Lysophosphatidylcholines / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D034741:RNA, Small Interfering / Q000235:genetics; D043562:Receptors, G-Protein-Coupled / Q000172:deficiency / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D018797:Cell Cycle Proteins; D017931:DNA Primers; C115270:G2A receptor; D008244:Lysophosphatidylcholines; D034741:RNA, Small Interfering; D043562:Receptors, G-Protein-Coupled