title: Native oligomerization determines the mode of action and biological activities of human cathelicidin LL-37.
abstract: LL-37 is a multifunctional component of innate immunity, with a membrane-directed antimicrobial activity and receptor-mediated pleiotropic effects on host cells. Sequence variations in its primate orthologues suggest that two types of functional features have evolved; human LL-37-like peptides form amphipathic helical structures and self-assemble under physiological conditions, whereas rhesus RL-37-like peptides only adopt this structure in the presence of bacterial membranes. The first type of peptide has a lower and more medium-sensitive antimicrobial activity than the second type, but an increased capacity to stimulate host cells. Oligomerization strongly affects the mode of interaction with biological membranes and, consequently, both cytotoxicity and receptor-mediated activities. In the present study we explored the effects of LL-37 self-association by using obligate disulfide-linked dimers with either parallel or antiparallel orientations. These had an increased propensity to form stacked helices in bulk solution and when in contact with either anionic or neutral model membranes. The antimicrobial activity against Gram-positive or Gram-negative bacteria, as well as the cytotoxic effects on host cells, strongly depended on the type of dimerization. To investigate the extent of native oligomerization we replaced Phe5 with the photoactive residue Bpa (p-benzoyl-L-phenylalanine), which, upon UV irradiation, enabled covalent cross-linking and allowed us to assess the extent of oligomerization in both physiological solution and in model membranes.
authors.affiliation: *Department of Life Science, University of Trieste, via Giorgeri 5, 34127 Trieste, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Xhindoli
authors.affiliation: *Department of Life Science, University of Trieste, via Giorgeri 5, 34127 Trieste, Italy.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Pacor
authors.affiliation: *Department of Life Science, University of Trieste, via Giorgeri 5, 34127 Trieste, Italy.
authors.forename: Filomena
authors.initials: F
authors.lastname: Guida
authors.affiliation: *Department of Life Science, University of Trieste, via Giorgeri 5, 34127 Trieste, Italy.
authors.forename: Nikolinka
authors.initials: N
authors.lastname: Antcheva
authors.affiliation: *Department of Life Science, University of Trieste, via Giorgeri 5, 34127 Trieste, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Tossi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002417:Cattle; D002645:Chickens; D004912:Erythrocytes / Q000378:metabolism; D006801:Humans; D008081:Liposomes / Q000378:metabolism; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012756:Sheep; D020298:U937 Cells; D054804:Cathelicidins
chemical_list: D023181:Antimicrobial Cationic Peptides; D008081:Liposomes; D054804:Cathelicidins