title: Involvement of sphingolipids in apoptin-induced cell killing.
abstract: The potential anti-tumor agent Apoptin activates apoptosis in many human cancers and transformed cell lines, but is believed to be less potent in primary cells. Although caspase 3 is activated during apoptin-induced apoptosis, the mechanism of tumor cell killing remains elusive. We now show that apoptin-mediated cell death involves modulation of the sphingomyelin-ceramide pathway. Treating cells with Ad-GFPApoptin resulted in increased ceramide accumulation and enhanced expression of acid sphingomyelinase (ASMase) with a concomitant increase in ASMase activity and decreased sphingomyelin. Using confocal microscopy, ASMase, normally present in the endosomal/lysosomal compartment, was observed to translocate to the cell's periphery. Cotreatment of Ad-GFPApoptin-infected cells with the ASMase inhibitor desipramine (2.5 muM) attenuated (30%; P<0.01) apoptin-induced cell death. Apoptin was also able to induce a significant decline in sphingosine content by inhibition of ceramide deacylation through down-regulation of acid ceramidase at the protein level. Supporting the role of ceramide in apoptin action, treatment of cells with the combination of an exogenous cell-permeable ceramide analog (C6-ceramide) and Ad-GFPApoptin infection yielded a significant increase (P<0.01) in apoptosis over either treatment modality alone. Together, these data suggest that apoptin modulates ceramide/sphingolipid metabolism as part of its mechanism of action.
authors.affiliation: Department of Microbiology and Immunology, Medical University of South Carolina, P.O. Box 250504, 173 Ashley Avenue, Charleston, SC 29425, USA.
authors.forename: Xiang
authors.initials: X
authors.lastname: Liu
authors.forename: Youssef H
authors.initials: YH
authors.lastname: Zeidan
authors.forename: Saeed
authors.initials: S
authors.lastname: Elojeimy
authors.forename: David H
authors.initials: DH
authors.lastname: Holman
authors.forename: Ahmed M
authors.initials: AM
authors.lastname: El-Zawahry
authors.forename: Gui-Wen
authors.initials: GW
authors.lastname: Guo
authors.forename: Alicja
authors.initials: A
authors.lastname: Bielawska
authors.forename: Jacek
authors.initials: J
authors.lastname: Bielawski
authors.forename: Zdzislaw
authors.initials: Z
authors.lastname: Szulc
authors.forename: Semyon
authors.initials: S
authors.lastname: Rubinchik
authors.forename: Jian-Yun
authors.initials: JY
authors.lastname: Dong
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Keane
authors.forename: Mahvash
authors.initials: M
authors.lastname: Tavassoli
authors.forename: Yusuf A
authors.initials: YA
authors.lastname: Hannun
authors.forename: James S
authors.initials: JS
authors.lastname: Norris
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D017209:Apoptosis / Q000187:drug effects; D036022:Capsid Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D002518:Ceramides / Q000096:biosynthesis; D003891:Desipramine / Q000494:pharmacology; D015536:Down-Regulation; D011992:Endosomes / Q000378:metabolism; D002517:Galactosylgalactosylglucosylceramidase / Q000378:metabolism; D015870:Gene Expression; D017930:Genes, Reporter / Q000235:genetics; D006801:Humans; D008247:Lysosomes / Q000378:metabolism; D008297:Male; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013107:Sphingolipids / Q000378:metabolism*; D013108:Sphingomyelin Phosphodiesterase / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D036022:Capsid Proteins; D002518:Ceramides; D011993:Recombinant Fusion Proteins; D013107:Sphingolipids; C091717:VP3 protein, Chicken anemia virus; D013108:Sphingomyelin Phosphodiesterase; D002517:Galactosylgalactosylglucosylceramidase; D003891:Desipramine