title: The human CXC chemokine granulocyte chemotactic protein 2 (GCP-2)/CXCL6 possesses membrane-disrupting properties and is antibacterial.
abstract: Granulocyte chemotactic protein 2 (GCP-2)/CXCL6 is a CXC chemokine expressed by macrophages and epithelial and mesenchymal cells during inflammation. Through binding and activation of its receptors (CXCR1 and CXCR2), it exerts neutrophil-activating and angiogenic activities. Here we show that GCP-2/CXCL6 itself is antibacterial. Antibacterial activity against gram-positive and gram-negative pathogenic bacteria of relevance to mucosal infections was seen at submicromolar concentrations (minimal bactericidal concentration at which 50% of strains tested were killed, 0.063 +/- 0.01 to 0.37 +/- 0.03 muM). In killed bacteria, GCP-2/CXCL6 associated with bacterial surfaces, which showed membrane disruption and leakage. A structural prediction indicated the presence of three antiparallel NH(2)-terminal beta-sheets and a short amphipathic COOH-terminal alpha-helix; the latter feature is typical of antimicrobial peptides. However, when the synthetic derivatives corresponding to the NH(2)-terminal (50 amino acids) and COOH-terminal (19 amino acids, corresponding to the putative alpha-helix) regions were compared, higher antibacterial activity was observed for the NH(2)-terminus-derived peptide, indicating that the holopeptide is necessary for full antibacterial activity. An artificial model of bacterial membranes confirmed these findings. The helical content of GCP-2/CXCL6 in the presence or absence of lipopolysaccharide or negatively charged membranes was studied by circular dichroism. As with many antibacterial peptides, membrane disruption by GCP-2/CXCL6 was dose-dependently reduced in the presence of NaCl, which, we here demonstrate, inhibited the binding of the peptide to the bacterial surface. Compared with CXC chemokines ENA-78/CXCL5 and NAP-2/CXCL7, GCP-2/CXCL6 showed a 90-fold-higher antibacterial activity. Taken together, GCP/CXCL6, in addition to its chemotactic and angiogenic properties, is likely to contribute to direct antibacterial activity during localized infection.
authors.affiliation: Divisions of Infection, Department of Clinical Sciences Lund, Lund University, SE-221 84 Lund, Sweden. hlinge@nshs.edu
authors.forename: Helena M
authors.initials: HM
authors.lastname: Linge
authors.forename: Mattias
authors.initials: M
authors.lastname: Collin
authors.forename: Pontus
authors.initials: P
authors.lastname: Nordenfelt
authors.forename: Matthias
authors.initials: M
authors.lastname: Mörgelin
authors.forename: Martin
authors.initials: M
authors.lastname: Malmsten
authors.forename: Arne
authors.initials: A
authors.lastname: Egesten
mesh_terms: D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry / Q000494:pharmacology; D001770:Blood Bactericidal Activity; D002462:Cell Membrane / Q000187:drug effects; D054365:Chemokine CXCL5 / Q000737:chemistry / Q000494:pharmacology; D054427:Chemokine CXCL6 / Q000737:chemistry / Q000494:pharmacology*; D004926:Escherichia coli / Q000187:drug effects; D006090:Gram-Negative Bacteria / Q000187:drug effects* / Q000472:pathogenicity; D006094:Gram-Positive Bacteria / Q000187:drug effects* / Q000472:pathogenicity; D006801:Humans; D066298:In Vitro Techniques; D008081:Liposomes; D008826:Microbial Sensitivity Tests; D008958:Models, Molecular; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000494:pharmacology; D013211:Staphylococcus aureus / Q000187:drug effects; D013297:Streptococcus pyogenes / Q000187:drug effects; D001620:beta-Thromboglobulin / Q000737:chemistry / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; C486263:CXCL5 protein, human; C515503:CXCL6 protein, human; D054365:Chemokine CXCL5; D054427:Chemokine CXCL6; D008081:Liposomes; C061615:PPBP protein, human; D011994:Recombinant Proteins; D001620:beta-Thromboglobulin