title: C-Mannosylated peptides derived from the thrombospondin type 1 repeat enhance lipopolysaccharide-induced signaling in macrophage-like RAW264.7 cells.
abstract: C-Mannosylation is a unique type of glycosylation occurring at the first Trp (W) in the WXXW motif, which is found in the thrombospondin type 1 repeat (TSR) of proteins. However, the biological function of C-mannosylation is not fully understood. In this study, we investigated the effect of C-mannosylated TSR-derived peptides on lipopolysaccharide (LPS)-induced signaling in macrophage-like RAW264.7 cells. The cells were stimulated with LPS in the presence or absence of chemically synthesized peptides with or without C-mannose (e.g., (C-Man)-Trp-Ser-Pro-Trp [C-Man-WSPW], C-Man-W, WSPW, etc.), then the effects of the peptides on cellular viability and signaling were examined. We found a cytotoxic effect in the cells treated with LPS and C-Man-WSPW, but not in the cells solely treated with LPS or C-Man-WSPW. We also found that production of tumor necrosis factor-alpha (TNF-alpha) was upregulated more in response to LPS plus C-Man-WSPW, than in response to LPS plus WSPW or LPS alone. Among the LPS-induced signaling pathways that induce production of TNF-alpha, the activation of c-Jun N-terminal kinase (JNK) was greatly enhanced by LPS and C-Man-WSPW, and the production of TNF-alpha was suppressed by an inhibitor for JNK. Together, these results demonstrate a novel function of the C-mannosylated TSR-derived peptide motif, to promote LPS-induced JNK signaling, and this leads to an enhancement of cytotoxicity via the upregulation of TNF-alpha production.
authors.affiliation: Department of Biochemistry and Molecular Biology in Disease, Atomic Bomb Disease Institute, Nagasaki, Japan.
authors.forename: Eiji
authors.initials: E
authors.lastname: Muroi
authors.forename: Shino
authors.initials: S
authors.lastname: Manabe
authors.forename: Midori
authors.initials: M
authors.lastname: Ikezaki
authors.forename: Yoshishige
authors.initials: Y
authors.lastname: Urata
authors.forename: Shinichi
authors.initials: S
authors.lastname: Sato
authors.forename: Takahito
authors.initials: T
authors.lastname: Kondo
authors.forename: Yukishige
authors.initials: Y
authors.lastname: Ito
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Ihara
mesh_terms: D000818:Animals; D002460:Cell Line; D002470:Cell Survival; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation; D008070:Lipopolysaccharides / Q000737:chemistry / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism; D008358:Mannose / Q000737:chemistry*; D051379:Mice; D010455:Peptides / Q000737:chemistry; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D019699:Thrombospondins / Q000737:chemistry*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D008070:Lipopolysaccharides; D010455:Peptides; D019699:Thrombospondins; D014409:Tumor Necrosis Factor-alpha; D008358:Mannose