Tomiuk S, Hofmann K, Nix M, Zumbansen M, Stoffel W
Laboratory of Molecular Neurosciences, Institute of Biochemistry, Faculty of Medicine, University of Cologne, Joseph-Stelzmann-Strasse 52, D-50931 Cologne, Germany.
Proc Natl Acad Sci U S A. 1998 Mar 31;95(7):3638-43. doi: 10.1073/pnas.95.7.3638.
Sphingomyelin is an abundant constituent of the plasma membranes of mammalian cells. Ceramide, its primary catabolic intermediate, is released by either acid sphingomyelinase or neutral sphingomyelinase (nSMase) and has emerged as a potential lipid signaling molecule. nSMase is regarded as a key enzyme in the regulated activation of the "sphingomyelin cycle" and cell signaling. We report here the cloning, identification, and functional characterization of murine and human nSMase, a ubiquitously expressed integral membrane protein, which displays all established properties of the Mg2+-dependent nSMase of the plasma membrane. Stably nSMase-overexpressing U937 and human embryonic kidney cell lines have been generated for the study of the role of nSMase in signal transduction pathways. Their stimulation by tumor necrosis factor alpha leads only to a moderately elevated ceramide concentration. Activation of Jun kinase and NFkappaB and poly(ADP-ribose) polymerase cleavage are identical in mock- and nSMase-transfected cells. Tumor necrosis factor alpha triggers the ERK1 pathway in none of the cell lines. The cloned nSMase will facilitate further controlled experiments aiming at the definition of a possible role of ceramide as signal transduction molecule.
鞘磷脂是哺乳动物细胞质膜的一种丰富成分。其主要分解代谢中间产物神经酰胺可由酸性鞘磷脂酶或中性鞘磷脂酶（nSMase）释放，并已成为一种潜在的脂质信号分子。nSMase被认为是“鞘磷脂循环”调控激活和细胞信号传导中的关键酶。我们在此报告了小鼠和人类nSMase的克隆、鉴定及功能特性，它是一种普遍表达的整合膜蛋白，具有质膜中Mg2+依赖性nSMase的所有既定特性。为研究nSMase在信号转导途径中的作用，已构建了稳定过表达nSMase的U937细胞系和人胚肾细胞系。肿瘤坏死因子α对它们的刺激仅导致神经酰胺浓度适度升高。在mock转染和nSMase转染的细胞中，Jun激酶和NFκB的激活以及聚（ADP - 核糖）聚合酶的裂解情况相同。肿瘤坏死因子α在任何细胞系中均未触发ERK1途径。克隆的nSMase将有助于进一步进行对照实验，以确定神经酰胺作为信号转导分子可能发挥的作用。
