Binding of LL-37 to model biomembranes: Insight into target vs host cell recognition |
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Authors: | Rohit Sood,Milla Pietiä inen,Paavo K.J. Kinnunen |
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Affiliation: | a Helsinki Biophysics and Biomembrane Group, Medical Biochemistry, Institute of Biomedicine, P.O. Box 63 (Haartmaninkatu 8), FIN-00014 University of Helsinki, Finland b Infection Pathogenesis Laboratory, Department of Viral Diseases and Immunology, National Public Health Institute, Mannerheimintie 166, FIN-00300 Helsinki, Finland |
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Abstract: | Pursuing the molecular mechanisms of the concentration dependent cytotoxic and hemolytic effects of the human antimicrobial peptide LL-37 on cells, we investigated the interactions of this peptide with lipids using different model membranes, together with fluorescence spectroscopy for the Trp-containing mutant LL-37(F27W). Minimum concentrations inhibiting bacterial growth and lipid interactions assessed by dynamic light scattering and monolayer penetration revealed the mutant to retain the characteristics of native LL-37. Although both LL-37 and the mutant intercalated effectively into zwitterionic phosphatidylcholine membranes the presence of acidic phospholipids caused augmented membrane binding. Interestingly, strongly attenuated intercalation of LL-37 into membranes containing both cholesterol and sphingomyelin (both at X = 0.3) was observed. Accordingly, the distinction between target and host cells by LL-37 is likely to derive from i) acidic phospholipids causing enhanced association with the former cells as well as ii) from attenuated interactions with the outer surface of the plasma membrane of the peptide secreting host, imposed by its high content of cholesterol and sphingomyelin. Our results further suggest that LL-37 may exert its antimicrobial effects by compromising the membrane barrier properties of the target microbes by a mechanism involving cytotoxic oligomers, similarly to other peptides forming amyloid-like fibers in the presence of acidic phospholipids. |
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Keywords: | AMPs, antimicrobial peptides Chol, cholesterol CD, circular dichroism DPPC, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine DPPE, 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine DPPG, 1,2-dipalmitoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] DPPDns, 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamino N-(5-dimethylaminonaphthalene-1-sulfonyl)triethylammonium salt ET, energy transfer efficiencies EDTA, ethylenediaminetetraacetic acid FRET, fluorescence resonance energy transfer KSV, Stern-Volmer quenching constant kq, bimolecular quenching constant Kd, apparent dissociation constant LL-37, native LL-37 LL-37(F27W) with Phe27 replaced by Trp LUV, large unilamellar vesicles L/P, lipid to peptide ratio LB, Luria-Bertani MIC, minimal inhibitory concentration NBD-PC, 1-oleoyl-2-[6-[7-nitro-2-1,3-benzoxadiazol-4-yl)amino]hexanoyl]-sn-glycero-3-phosphocholine POPG, 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-rac-glycerol POPS, 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho- smallcaps" >l-serine (6,7)-Br2-PC, 1-palmitoyl-2-(6,7-dibromostearoyl)phosphocholine (9,10)-Br2-PC, 1-palmitoyl-2-(9,10-dibromostearoyl)phosphocholine (11,12)-Br2-PC,-palmitoyl-2-(11,12-dibromostearoyl)phosphocholine PC, phosphatidylcholine PG, phosphatidylglycerol PS, phosphatidylserine P/L, peptide to lipid ratio Q, quencher RT, room temperature Spm, sphingomyelin SLBs, supported lipid bilayers SOPC, 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine λmax, fluorescence emission maximum τf, fluorescence lifetime ζ, zeta potential |
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