title: The peptide sequence of diacyl lipopeptides determines dendritic cell TLR2-mediated NK activation.
abstract: Natural killer (NK) cells are lymphocyte effectors that are activated to control certain microbial infections and tumors. Many NK-activating and regulating receptors are involved in regulating NK cell function. In addition, activation of naïve NK cells is fundamentally triggered by cytokines or myeloid dendritic cells (mDC) in various modes. In this study, we synthesized 16 S-[2,3-bis(palmitoyl)propyl]cysteine (Pam2Cys) lipopeptides with sequences designed from lipoproteins of Staphylococcus aureus, and assessed their functional properties using mouse (C57BL/6) bone marrow-derived DC (BMDC) and NK cells. NK cell activation was evaluated by three criteria: IFN-gamma production, up-regulation of NK activation markers and cytokines, and NK target (B16D8 cell) cytotoxicity. The diacylated lipopeptides acted as TLR2 ligands, inducing up-regulation of CD25/CD69/CD86, IL-6, and IL-12p40, which represent maturation of BMDC. Strikingly, the Pam2Cys lipopeptides induced mouse NK cell activation based on these criteria. Cell-cell contact by Pam2Cys peptide-stimulated BMDC and NK cells rather than soluble mediators released by stimulated BMDC induced activation of NK cells. For most lipopeptides, the BMDC TLR2/MyD88 pathway was responsible for driving NK activation, while some slightly induced direct activation of NK cells via the TLR2/MyD88 pathway in NK cells. The potential for NK activation was critically regulated by the peptide primary sequence. Hydrophobic or proline-containing sequences proximal to the N-terminal lipid moiety interfered with the ability of lipopeptides to induce BMDC-mediated NK activation. This mode of NK activation is distinctly different from that induced by polyI:C, which is closely associated with type I IFN-inducing pathways of BMDC. These results imply that the MyD88 pathway of BMDC governs an alternative NK-activating pathway in which the peptide sequence of TLR2-agonistic lipopeptides critically affects the potential for NK activation.
authors.affiliation: Department of Microbiology and Immunology, Graduate School of Medicine, Hokkaido University, Sapporo, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Azuma
authors.forename: Ryoko
authors.initials: R
authors.lastname: Sawahata
authors.forename: Yuusuke
authors.initials: Y
authors.lastname: Akao
authors.forename: Takashi
authors.initials: T
authors.lastname: Ebihara
authors.forename: Sayuri
authors.initials: S
authors.lastname: Yamazaki
authors.forename: Misako
authors.initials: M
authors.lastname: Matsumoto
authors.forename: Masahito
authors.initials: M
authors.lastname: Hashimoto
authors.forename: Koichi
authors.initials: K
authors.lastname: Fukase
authors.forename: Yukari
authors.initials: Y
authors.lastname: Fujimoto
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Seya
mesh_terms: D000818:Animals; D002460:Cell Line; D002478:Cells, Cultured; D003713:Dendritic Cells / Q000276:immunology; D005260:Female; D006801:Humans; D007694:Killer Cells, Natural / Q000166:cytology / Q000276:immunology*; D055666:Lipopeptides / Q000737:chemistry / Q000276:immunology*; D008074:Lipoproteins / Q000276:immunology*; D008213:Lymphocyte Activation; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D053594:Myeloid Differentiation Factor 88 / Q000276:immunology; D013203:Staphylococcal Infections / Q000276:immunology*; D013211:Staphylococcus aureus / Q000276:immunology; D051195:Toll-Like Receptor 2 / Q000276:immunology*
chemical_list: D055666:Lipopeptides; D008074:Lipoproteins; C507780:Myd88 protein, mouse; D053594:Myeloid Differentiation Factor 88; C552442:S-(2,3-bis(palmitoyloxy)propyl)cysteine; C493486:Tlr2 protein, mouse; D051195:Toll-Like Receptor 2
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