Ligand-specific conformational change of the G-protein-coupled receptor ALX/FPR2 determines proresolving functional responses

Proc Natl Acad Sci U S A. 2013 Nov 5;110(45):18232-7. doi: 10.1073/pnas.1308253110. Epub 2013 Oct 9.

Abstract

Formyl-peptide receptor type 2 (FPR2), also called ALX (the lipoxin A4 receptor), conveys the proresolving properties of lipoxin A4 and annexin A1 (AnxA1) and the proinflammatory signals elicited by serum amyloid protein A and cathelicidins, among others. We tested here the hypothesis that ALX might exist as homo- or heterodimer with FPR1 or FPR3 (the two other family members) and operate in a ligand-biased fashion. Coimmunoprecipitation and bioluminescence resonance energy transfer assays with transfected HEK293 cells revealed constitutive dimerization of the receptors; significantly, AnxA1, but not serum amyloid protein A, could activate ALX homodimers. A p38/MAPK-activated protein kinase/heat shock protein 27 signaling signature was unveiled after AnxA1 application, leading to generation of IL-10, as measured in vitro (in primary monocytes) and in vivo (after i.p. injection in the mouse). The latter response was absent in mice lacking the ALX ortholog. Using a similar approach, ALX/FPR1 heterodimerization evoked using the panagonist peptide Ac2-26, identified a JNK-mediated proapoptotic path that was confirmed in primary neutrophils. These findings provide a molecular mechanism that accounts for the dual nature of ALX and indicate that agonist binding and dimerization state contribute to the conformational landscape of FPRs.

Keywords: inflammation; leukocyte; resolution signaling.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Annexin A1 / metabolism*
  • Bioluminescence Resonance Energy Transfer Techniques
  • Dimerization
  • HEK293 Cells
  • Humans
  • Immunoprecipitation
  • Interleukin-10 / metabolism
  • Mice
  • Molecular Sequence Data
  • Protein Conformation*
  • Receptors, Formyl Peptide / chemistry*
  • Receptors, Formyl Peptide / metabolism*
  • Serum Amyloid A Protein / metabolism
  • Signal Transduction / physiology*

Substances

  • Annexin A1
  • Receptors, Formyl Peptide
  • Serum Amyloid A Protein
  • formyl peptide receptor 2, mouse
  • Interleukin-10