好中球のラクトシルセラミドを介した活性酸素産生機構について

Abstract

Lactosylceramide (LacCer), which is neutral glycosphingolipid and also known as CDw17, mediates superoxide production from neutrophils. Microorganisms such as gram-negative and -positive bacteria and fungi can bind to LacCer. Neutrophils thus appear to contribute to phagocytosis and superoxide generation. Treatment of neutrophils with anti-LacCer antibodies induced superoxide generation from the cells, which was blocked by PP1, wortomannin, SB203580 and H7, suggesting involvement of Src kinase, PI3 kinase, p38-MAP kinase, and protein kinase C, respectively. Upon exposure to dimethylsulfoxide (DMSO) that triggered differentiation into neutrophil lineage, promyelocytic leukemia HL-60 cells acquired the ability to generate superoxide, whilie exhibiting little response to the antibodies, if any. Density gradient centrifugation revealed that LacCer and a Src kinase Lyn were recovered in detergent-insoluble membrane (DIM) of neutrophils and HL-60 cells. However, LacCer was associated with Lyn in neutrophils but not HL-60 cells. Anti-LacCer antibody T5A7 phosphorylated Lyn molecules in neutrophil DIM. Taken together, these above data suggest that neutrophils are characterized by the presence of cell surface LacCer-enriched glycosignaling domain coupled with Lyn, and that the ligand binding to LacCer induces the activation of Lyn/PI3K/p38 MAPK/protein kinase C signal transduction pathway. The association of Lyn with LacCer seems to be a key for LacCer-mediated activation of Lyn, leading to superoxide generation by neutrophils.