Figure 3.

SSL13 specifically binds and activates human formyl peptide receptor 2. (a) Neutrophils were preincubated with or without 3‐μg/ml Pertussis toxin (PTX) for 60 min at 37°C with CO₂ and then labelled with Fluo‐3‐AM. Neutrophil stimulation by SSL13 is sensitive to PTX. Formyl‐methionyl‐leucyl phenylalanine is the control ligand of formyl peptide receptor 1, which is also sensitive to PTX. (b) Human neutrophil stimulation by SSL13 is inhibited by formyl peptide receptor‐like 1 inhibitory protein (FLIPr), not chemotaxis inhibitory protein of Staphylococcus aureus (CHIPS). (c) SSL13 specific binding to human neutrophils is blocked by FLIPr, not CHIPS. Data represent means ± SEM of three independent experiments. (d) SSL13 specifically binds to formyl peptide receptor 2 (FPR2)‐transfected HL60 cells (HL60/FPR2), but not to control HL60 cells. (e) SSL13 induces profound calcium fluxes in HL60/FPR2 cells, but not in empty HL60 cells. MMK‐1 is a synthetic control ligand of FPR2. (f) HL60/FPR2 cells stimulation by SSL13 is concentration dependent. (g) HL60/FPR2 cells stimulation by SSL13 is sensitive to FPR2‐specific inhibitor FLIPr. Data are mean fluorescence ± SEM of three experiments