Release of Toll-like receptor-2-activating bacterial lipoproteins in Shigella flexneri culture supernatants.
Shigella spp. cause dysentery, a severe form of bloody diarrhea. Apoptosis, or programmed cell death, is induced during Shigella infections and has been proposed to be a key event in the pathogenesis of dysentery. Here, we describe a novel cytotoxic activity in the sterile-culture supernatants of Shigella flexneri. An identical activity was identified in purified S. flexneri endotoxin, defined here as a mixture of lipopolysaccharide (LPS) and endotoxin-associated proteins (EP). Separation of endotoxin into EP and LPS revealed the activity to partition exclusively to the EP fraction. Biochemical characterization of S. flexneri EP and culture supernatants, including enzymatic deactivation, reverse-phase high-pressure liquid chromatography analysis, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and a Toll-like receptor-2 (TLR2) activation assay, indicates that the cytotoxic component is a mixture of bacterial lipoproteins (BLP). We show that biologically active BLP are liberated into culture supernatants of actively growing S. flexneri. In addition, our data indicate that BLP, and not LPS, are the component of endotoxin of gram-negative organisms responsible for activating TLR2. The activation of apoptosis by BLP shed from S. flexneri is discussed as a novel aspect of the interaction of bacteria with the host.
Aliprantis
A O
AO
Skirball Institute and Department of Microbiology, New York University School of Medicine, New York, New York 10016, USA.
Weiss
D S
DS
Radolf
J D
JD
Zychlinsky
A
A
D017209:Apoptosis; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000378:metabolism*; D002460:Cell Line; D005591:Chemical Fractionation; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D003470:Culture Media; D029721:Drosophila Proteins; D006801:Humans; D050356:Lipid Metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008074:Lipoproteins / Q000096:biosynthesis / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000378:metabolism*; D019800:Phenol / Q000494:pharmacology; D011956:Receptors, Cell Surface / Q000378:metabolism*; D022621:Shiga Toxin / Q000494:pharmacology; D012763:Shigella flexneri / Q000254:growth & development / Q000378:metabolism*; D015398:Signal Transduction; D051195:Toll-Like Receptor 2; D051193:Toll-Like Receptors; D014238:Trichloroacetic Acid / Q000494:pharmacology
D001426:Bacterial Proteins; D003470:Culture Media; D029721:Drosophila Proteins; D008070:Lipopolysaccharides; D008074:Lipoproteins; D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; C495342:TLR2 protein, human; D051195:Toll-Like Receptor 2; D051193:Toll-Like Receptors; D019800:Phenol; D014238:Trichloroacetic Acid; D022621:Shiga Toxin