title: Structure, dynamics, and antimicrobial and immune modulatory activities of human LL-23 and its single-residue variants mutated on the basis of homologous primate cathelicidins.
abstract: LL-23 is a natural peptide corresponding to the 23 N-terminal amino acid residues of human host defense cathelicidin LL-37. LL-23 demonstrated, compared to LL-37, a conserved ability to induce the chemokine MCP-1 in human peripheral blood mononuclear cells, a lack of ability to suppress induction of the pro-inflammatory cytokine TNF-α in response to bacterial lipopolysaccharides (LPS), and reduced antimicrobial activity. Heteronuclear multidimensional nuclear magnetic resonance (NMR) characterization of LL-23 revealed similar secondary structures and backbone dynamics in three membrane-mimetic micelles: SDS, dodecylphosphocholine (DPC), and dioctanoylphosphatidylglycerol. The NMR structure of LL-23 determined in perdeuterated DPC contained a unique serine that segregated the hydrophobic surface of the amphipathic helix into two domains. To improve our understanding, Ser9 of LL-23was changed to either Ala or Val on the basis of homologous primate cathelicidins. These changes made the hydrophobic surface of LL-23 continuous and enhanced antibacterial activity. While identical helical structures did not explain the altered activities, a reduced rate of hydrogen-deuterium exchange from LL-23 to LL-23A9 to LL-23V9 suggested a deeper penetration of LL-23V9 into the interior of the micelles, which correlated with enhanced activities. Moreover, these LL-23 variants had discrete immunomodulatory activities. Both restored the TNF-α dampening activity to the level of LL-37. Furthermore, LL-23A9, like LL-23, maintained superior protective MCP-1 production, while LL-23V9 was strongly immunosuppressive, preventing baseline MCP-1 induction and substantially reducing LPS-stimulated MCP-1 production. Thus, these LL-23 variants, designed on the basis of a structural hot spot, are promising immune modulators that are easier to synthesize and less toxic to mammalian cells than the parent peptide LL-37.
authors.affiliation: Department of Pathology and Microbiology, College of Medicine, University of Nebraska Medical Center, 986495 Nebraska Medical Center, Omaha, Nebraska 68198-6495, United States. gwang@unmc.edu
authors.forename: Guangshun
authors.initials: G
authors.lastname: Wang
authors.forename: Melissa
authors.initials: M
authors.lastname: Elliott
authors.forename: Anna L
authors.initials: AL
authors.lastname: Cogen
authors.forename: Edward L
authors.initials: EL
authors.lastname: Ezell
authors.forename: Richard L
authors.initials: RL
authors.lastname: Gallo
authors.forename: Robert E W
authors.initials: RE
authors.lastname: Hancock
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000890:Anti-Infective Agents / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D054804:Cathelicidins / Q000737:chemistry*; D018925:Chemokines / Q000378:metabolism; D041961:Deuterium Exchange Measurement; D006801:Humans; D007155:Immunologic Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D008826:Microbial Sensitivity Tests; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D010446:Peptide Fragments / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D011323:Primates; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D013211:Staphylococcus aureus / Q000187:drug effects
chemical_list: D000890:Anti-Infective Agents; D054804:Cathelicidins; D018925:Chemokines; D007155:Immunologic Factors; D010446:Peptide Fragments