title: Stress-induced ceramide generation and apoptosis via the phosphorylation and activation of nSMase1 by JNK signaling.
abstract: Neutral sphingomyelinase (nSMase) activation in response to environmental stress or inflammatory cytokine stimuli generates the second messenger ceramide, which mediates the stress-induced apoptosis. However, the signaling pathways and activation mechanism underlying this process have yet to be elucidated. Here we show that the phosphorylation of nSMase1 (sphingomyelin phosphodiesterase 2, SMPD2) by c-Jun N-terminal kinase (JNK) signaling stimulates ceramide generation and apoptosis and provide evidence for a signaling mechanism that integrates stress- and cytokine-activated apoptosis in vertebrate cells. An nSMase1 was identified as a JNK substrate, and the phosphorylation site responsible for its effects on stress and cytokine induction was Ser-270. In zebrafish cells, the substitution of Ser-270 for alanine blocked the phosphorylation and activation of nSMase1, whereas the substitution of Ser-270 for negatively charged glutamic acid mimicked the effect of phosphorylation. The JNK inhibitor SP600125 blocked the phosphorylation and activation of nSMase1, which in turn blocked ceramide signaling and apoptosis. A variety of stress conditions, including heat shock, UV exposure, hydrogen peroxide treatment, and anti-Fas antibody stimulation, led to the phosphorylation of nSMase1, activated nSMase1, and induced ceramide generation and apoptosis in zebrafish embryonic ZE and human Jurkat T cells. In addition, the depletion of MAPK8/9 or SMPD2 by RNAi knockdown decreased ceramide generation and stress- and cytokine-induced apoptosis in Jurkat cells. Therefore the phosphorylation of nSMase1 is a pivotal step in JNK signaling, which leads to ceramide generation and apoptosis under stress conditions and in response to cytokine stimulation. nSMase1 has a common central role in ceramide signaling during the stress and cytokine responses and apoptosis.
authors.affiliation: Nihon University, College of Bioresource Sciences, 1866 Kameino, Fujisawa, Kanagawa 252-0880, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Yabu
authors.affiliation: Nihon University, College of Bioresource Sciences, 1866 Kameino, Fujisawa, Kanagawa 252-0880, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Shiba
authors.affiliation: Nihon University, College of Bioresource Sciences, 1866 Kameino, Fujisawa, Kanagawa 252-0880, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Shibasaki
authors.affiliation: Nihon University, College of Bioresource Sciences, 1866 Kameino, Fujisawa, Kanagawa 252-0880, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Nakanishi
authors.affiliation: Food Safety Assessment Research Group, National Research Institute of Fisheries Science, 12-4 Fukuura 2, Kanazawa-ku, Yokohama, Kanagawa 236-8648, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Imamura
authors.affiliation: Food Safety Assessment Research Group, National Research Institute of Fisheries Science, 12-4 Fukuura 2, Kanazawa-ku, Yokohama, Kanagawa 236-8648, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Touhata
authors.affiliation: Food Safety Assessment Research Group, National Research Institute of Fisheries Science, 12-4 Fukuura 2, Kanazawa-ku, Yokohama, Kanagawa 236-8648, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Yamashita
mesh_terms: D000818:Animals; D017209:Apoptosis; D002460:Cell Line; D002518:Ceramides / Q000378:metabolism*; D004789:Enzyme Activation; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019169:Jurkat Cells; D020935:MAP Kinase Signaling System; D010766:Phosphorylation; D013108:Sphingomyelin Phosphodiesterase / Q000378:metabolism*; D015027:Zebrafish
chemical_list: D002518:Ceramides; D048031:JNK Mitogen-Activated Protein Kinases; D013108:Sphingomyelin Phosphodiesterase