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

SN Cooray, T Gobbetti… - Proceedings of the …, 2013 - National Acad Sciences
SN Cooray, T Gobbetti, T Montero-Melendez, S McArthur, D Thompson, AJL Clark…
Proceedings of the National Academy of Sciences, 2013National Acad Sciences
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 …
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.
National Acad Sciences