title: UDP-GlcNAc2-epimerase regulates cell surface sialylation and ceramide-induced cell death in human malignant lymphoma.
abstract: Stress signals induce ceramide (cer) through sphingomyelinase activation, and metabolites of cer such as sphingosine (Sph) and sphingosine-1-phoshate (S-1-P) play a significant role in many biological processes. This study aimed to elucidate the association between the alteration in cell surface sialylation and ceramide-induced cell death in the human Burkitt's lymphoma cell line, HBL-8. The highly sialylated 3G3 clone was less sensitive to C6-ceramide-induced cell death. On the other hand, the hyposialylated 3D2 clone was more sensitive to C6-ceramide-induced cell death. Neuraminidase treatment or knockdown by siRNA of uridine diphosphate-N-acetylglucosamine 2-epimerase (UDP-GlcNAc2-epimerase), which is a key enzyme of sialic acid biosynthesis, enhanced the amount of cell death induced by C6-ceramide in the highly sialylated 3G3 clone. Sialic acid metabolic complementation assays using several precursors of sialic acid showed that cell surface resialylation by N-acetyl-D-mannosamine (ManNAc) inhibited C6-ceramide-induced cell death. The amount of cell death by C6-ceramide was enhanced after pretreatment with phosphatidylinositol 3-kinase (PI3K) inhibitor, LY294002 in both clones. In addition, clone 3G3 was less sensitive to Sph than the 3D2 clone. In conclusion, in human malignant lymphoma, ceramide and its metabolite-induced cell death is regulated by the amount of sialic acid on the cell surface which in turn is regulated by mRNA expression of UDP-GlcNAc2-epimerase.
authors.affiliation: First Department of Pathology, Fukushima Medical University, School of Medicine, 1 Hikariga-oka, Fukushima 960-1295, Japan. osuzuki@fmu.ac.jp
authors.forename: Osamu
authors.initials: O
authors.lastname: Suzuki
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Tasaki
authors.forename: Takashi
authors.initials: T
authors.lastname: Kusakabe
authors.forename: Masafumi
authors.initials: M
authors.lastname: Abe
mesh_terms: D017304:Annexin A5 / Q000378:metabolism; D020169:Caspases / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D048430:Cell Shape / Q000187:drug effects; D002518:Ceramides / Q000494:pharmacology*; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008223:Lymphoma / Q000201:enzymology* / Q000235:genetics / Q000473:pathology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D012794:Sialic Acids / Q000378:metabolism*; D014534:UDPglucose 4-Epimerase / Q000235:genetics / Q000378:metabolism*
chemical_list: D017304:Annexin A5; D002518:Ceramides; D034741:RNA, Small Interfering; D012794:Sialic Acids; D007770:L-Lactate Dehydrogenase; D019869:Phosphatidylinositol 3-Kinases; D020169:Caspases; D014534:UDPglucose 4-Epimerase