Abstract
Although C5a receptor (C5aR) interacting with its agonist C5a promotes acute inflammation during the initiation phase, the roles of the recycling C5aR during the resolution phase are still unclear. We found that C5aR interacted with its antagonist/agonist ribosomal protein S19 (RP S19) polymer or a RP S19 polymer functional analogue S-tagged C5a/RP S19, which connects an RP S19 C-terminus (IAGQVAAANKKH) to the S-tagged C5a C-terminus, promoted acute inflammation at the resolution phase via an activation of the apoptosis-inducing transcription factor delta lactoferrin (δLf) in neutrophils and the membrane mobilizing factor full-length annexin A3 (ANXA3) in macrophages. To confirm the antagonistic system of the recycling C5aR, S-tagged δLf-coupled BrCN-activated Sepharose 4B beads were incubated with cytoplasmic proteins and identified a neutrophil-specific δANXA3 via pull-down experiments. The S-tagged C5a/RP S19-induced agonistic functions in macrophage-like cells that were differentiated from human promyelocytic leukemia HL-60 cells by phorbol-12-myristate-13-acetate were suppressed by δLf and δANXA3 co-overexpression. δANXA3 seems to participate in the antagonistic system of the neutrophil C5aR involving IAGQVAAANKKH and δLf. Most likely, δANXA3 works as antagonist for the recycling C5aR on neutrophils during the resolution phase of acute inflammation.