Protein C inhibitor--a novel antimicrobial agent.
Protein C inhibitor (PCI) is a heparin-binding serine proteinase inhibitor belonging to the family of serpin proteins. Here we describe that PCI exerts broad antimicrobial activity against bacterial pathogens. This ability is mediated by the interaction of PCI with lipid membranes, which subsequently leads to their permeabilization. As shown by negative staining electron microscopy, treatment of Escherichia coli or Streptococcus pyogenes bacteria with PCI triggers membrane disruption followed by the efflux of bacterial cytosolic contents and bacterial killing. The antimicrobial activity of PCI is located to the heparin-binding site of the protein and a peptide spanning this region was found to mimic the antimicrobial activity of PCI, without causing lysis or membrane destruction of eukaryotic cells. Finally, we show that platelets can assemble PCI on their surface upon activation. As platelets are recruited to the site of a bacterial infection, these results may explain our finding that PCI levels are increased in tissue biopsies from patients suffering from necrotizing fasciitis caused by S. pyogenes. Taken together, our data describe a new function for PCI in innate immunity.
Malmström
Erik
E
Department of Clinical Sciences, Section for Clinical and Experimental Infection Medicine, Lund University, Lund, Sweden.
Mörgelin
Matthias
M
Malmsten
Martin
M
Johansson
Linda
L
Norrby-Teglund
Anna
A
Shannon
Oonagh
O
Schmidtchen
Artur
A
Meijers
Joost C M
JC
Herwald
Heiko
H
D000890:Anti-Infective Agents; D001665:Binding Sites; D001792:Blood Platelets / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism; D004926:Escherichia coli / Q000276:immunology; D006801:Humans; D007113:Immunity, Innate; D008081:Liposomes / Q000378:metabolism*; D015539:Platelet Activation; D018046:Protein C Inhibitor / Q000276:immunology* / Q000494:pharmacology; D013297:Streptococcus pyogenes / Q000276:immunology
D000890:Anti-Infective Agents; D008081:Liposomes; D018046:Protein C Inhibitor