Inhibition of LtxA toxicity by blocking cholesterol binding with peptides.
The leukotoxin (LtxA) produced by Aggregatibacter actinomycetemcomitans kills host immune cells, allowing the bacterium to establish an ecological niche in the upper aerodigestive tract of its human host. The interaction of LtxA with human immune cells is both complex and multifaceted, involving membrane lipids as well as cell-surface proteins. In the initial encounter with the host cell, LtxA associates with lymphocyte function-associated antigen-1, a cell surface adhesion glycoprotein. However, we have also demonstrated that the toxin associates strongly with the plasma membrane lipids, specifically cholesterol. This association with cholesterol is regulated by a cholesterol recognition amino acid consensus (CRAC) motif, with a sequence of (334) LEEYSKR(340), in the N-terminal region of the toxin. Here, we have demonstrated that removal of cholesterol from the plasma membrane or mutation of the LtxA CRAC motif inhibits the activity of the toxin in THP-1 cells. To inhibit LtxA activity, we designed a short peptide corresponding to the CRAC(336) motif of LtxA (CRAC(336WT)). This peptide binds to cholesterol and thereby inhibits the toxicity of LtxA in THP-1 cells. Previously, we showed that this peptide inhibits LtxA toxicity against Jn.9 (Jurkat) cells, indicating that peptides derived from the cholesterol-binding site of LtxA may have a potential clinical applicability in controlling infections of repeats-in-toxin-producing organisms.
Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, PA, USA.
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Brown
Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, PA, USA.
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Koufos
Department of Pathology, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA.
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Balashova
Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA.
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Boesze-Battaglia
Department of Pathology, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA.
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Lally
D016976:Aggregatibacter actinomycetemcomitans / Q000276:immunology / Q000378:metabolism; D001427:Bacterial Toxins / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism; D002352:Carrier Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D002448:Cell Adhesion / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism*; D005098:Exotoxins / Q000037:antagonists & inhibitors* / Q000276:immunology / Q000378:metabolism / Q000633:toxicity*; D054884:Host-Pathogen Interactions; D006801:Humans; D019169:Jurkat Cells; D008051:Lipid Bilayers / Q000378:metabolism; D016169:Lymphocyte Function-Associated Antigen-1 / Q000378:metabolism; D009154:Mutation; D010196:Pancreatic Elastase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D010455:Peptides / Q000378:metabolism*
D001427:Bacterial Toxins; D002352:Carrier Proteins; D005098:Exotoxins; D008051:Lipid Bilayers; D016169:Lymphocyte Function-Associated Antigen-1; D010455:Peptides; C018579:leukotoxin; D002784:Cholesterol; D010196:Pancreatic Elastase; C017130:cholesterol-binding protein
Aggregatibacter actinomycetemcomitans; cholesterol recognition amino acid consensus motif; cholesterol-binding; leukotoxin