UDP-GlcNAc2-epimerase regulates cell surface sialylation and ceramide-induced cell death in human malignant lymphoma

Int J Mol Med. 2008 Sep;22(3):339-48.

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.

MeSH terms

  • Annexin A5 / metabolism
  • Caspases / metabolism
  • Cell Death / drug effects
  • Cell Line, Tumor
  • Cell Membrane / metabolism
  • Cell Shape / drug effects
  • Ceramides / pharmacology*
  • Gene Expression Regulation, Enzymologic*
  • Gene Expression Regulation, Neoplastic*
  • Humans
  • L-Lactate Dehydrogenase / metabolism
  • Lymphoma / enzymology*
  • Lymphoma / genetics
  • Lymphoma / pathology*
  • Phosphatidylinositol 3-Kinases / metabolism
  • RNA, Small Interfering / genetics
  • Sialic Acids / metabolism*
  • UDPglucose 4-Epimerase / genetics
  • UDPglucose 4-Epimerase / metabolism*

Substances

  • Annexin A5
  • Ceramides
  • RNA, Small Interfering
  • Sialic Acids
  • L-Lactate Dehydrogenase
  • Phosphatidylinositol 3-Kinases
  • Caspases
  • UDPglucose 4-Epimerase