title: BAK activation is necessary and sufficient to drive ceramide synthase-dependent ceramide accumulation following inhibition of BCL2-like proteins.
abstract: Determining mechanistic details about how drugs kill cancer cells is critical for predicting which cancers will respond to given therapeutic regimens and for identifying effective combinations of drugs that more potently kill cancer cells while sparing normal cells. The BCL2 family of proteins and bioactive sphingolipids are intricately linked during apoptotic cell death. In fact, many chemotherapeutic drugs are known to cause accumulation of the pro-apoptotic sphingolipid ceramide; however, the mechanism by which this occurs is not completely understood. In the present study we demonstrate that direct inhibition of anti-apoptotic BCL2 proteins with ABT-263 is sufficient to induce C(16)-ceramide synthesis in multiple cell lines, including human leukaemia and myeloma cells. ABT-263 activates CerS (ceramide synthase) activity only in cells expressing BAK or in cells capable of activating BAK. Importantly, recombinant BAK is sufficient to increase in vitro CerS activity in microsomes purified from Bak-KO (knockout) cells and activated BAK more potently activates CerS than inactive BAK. Likewise, ABT-263 addition to wild-type, but not Bak-deficient, microsomes increases CerS in vitro activity. Furthermore, we present a feed-forward model by which BAK activation of CerS by chemotherapeutic drugs leads to elevated ceramide levels that result in synergistic channel formation by ceramide (or one of its metabolites) and BAX/BAK.
authors.affiliation: Division of Hematology and Oncology, Department of Medicine, James Graham Brown Cancer Center, University of Louisville, Louisville, KY 40202, USA. levi.beverly@louisville.edu
authors.forename: Levi J
authors.initials: LJ
authors.lastname: Beverly
authors.forename: Lauren A
authors.initials: LA
authors.lastname: Howell
authors.forename: Maria
authors.initials: M
authors.lastname: Hernandez-Corbacho
authors.forename: Lavona
authors.initials: L
authors.lastname: Casson
authors.forename: Jerry E
authors.initials: JE
authors.lastname: Chipuk
authors.forename: Leah J
authors.initials: LJ
authors.lastname: Siskind
mesh_terms: D000814:Aniline Compounds / Q000494:pharmacology; D017209:Apoptosis / Q000235:genetics; D045744:Cell Line, Tumor; D002518:Ceramides / Q000378:metabolism*; D055786:Gene Knockout Techniques; D057809:HEK293 Cells; D006801:Humans; D020014:K562 Cells; D007938:Leukemia / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D009101:Multiple Myeloma / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D010088:Oxidoreductases / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000378:metabolism*; D013449:Sulfonamides / Q000494:pharmacology; D020298:U937 Cells; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000378:metabolism*
chemical_list: D000814:Aniline Compounds; C494772:BAK1 protein, human; D002518:Ceramides; D019253:Proto-Oncogene Proteins c-bcl-2; D013449:Sulfonamides; D050998:bcl-2 Homologous Antagonist-Killer Protein; C097760:N-palmitoylsphingosine; D010088:Oxidoreductases; C108138:dihydroceramide desaturase; C528561:navitoclax