title: Cholesterol in negatively charged lipid bilayers modulates the effect of the antimicrobial protein granulysin.
abstract: The release of granulysin, a 9-kDa cationic protein, from lysosomal granules of cytotoxic T lymphocytes and natural killer cells plays an important role in host defense against microbial pathogens. Granulysin is endocytosed by the infected target cell via lipid rafts and kills subsequently intracellular bacteria. The mechanism by which granulysin binds to eukaryotic and prokaryotic cells but lyses only the latter is not well understood. We have studied the effect of granulysin on large unilamellar vesicles (LUVs) and supported bilayers with prokaryotic and eukaryotic lipid mixtures or model membranes with various lipid compositions and charges. Binding of granulysin to bilayers with negative charges, as typically found in bacteria and lipid rafts of eukaryotic cells, was shown by immunoblotting. Fluorescence release assays using LUV revealed an increase in permeability of prokaryotic, negatively charged and lipid raft-like bilayers devoid of cholesterol. Changes in permeability of these bilayers could be correlated to defects of various sizes penetrating supported bilayers as shown by atomic force microscopy. Based on these results, we conclude that granulysin causes defects in negatively charged cholesterol-free membranes, a membrane composition typically found in bacteria. In contrast, granulysin is able to bind to lipid rafts in eukaryotic cell membranes, where it is taken up by the endocytotic pathway, leaving the cell intact.
authors.affiliation: Division of Cell Biology, Institute of Anatomy, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland.
authors.forename: Hanna
authors.initials: H
authors.lastname: Barman
authors.forename: Michael
authors.initials: M
authors.lastname: Walch
authors.forename: Sonja
authors.initials: S
authors.lastname: Latinovic-Golic
authors.forename: Claudia
authors.initials: C
authors.lastname: Dumrese
authors.forename: Max
authors.initials: M
authors.lastname: Dolder
authors.forename: Peter
authors.initials: P
authors.lastname: Groscurth
authors.forename: Urs
authors.initials: U
authors.lastname: Ziegler
mesh_terms: D000945:Antigens, Differentiation, T-Lymphocyte / Q000378:metabolism* / Q000494:pharmacology; D002460:Cell Line; D002463:Cell Membrane Permeability / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002784:Cholesterol / Q000502:physiology*; D006801:Humans; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism*; D010539:Permeability / Q000187:drug effects; D055672:Static Electricity
chemical_list: D000945:Antigens, Differentiation, T-Lymphocyte; C075005:GNLY protein, human; D008051:Lipid Bilayers; D002784:Cholesterol