title: Inhibition of dihydroceramide desaturase activity by the sphingosine kinase inhibitor SKI II.
abstract: Sphingosine kinase inhibitor (SKI) II has been reported as a dual inhibitor of sphingosine kinases (SKs) 1 and 2 and has been extensively used to prove the involvement of SKs and sphingosine-1-phosphate (S1P) in cellular processes. Dihydroceramide desaturase (Des1), the last enzyme in the de novo synthesis of ceramide (Cer), regulates the balance between dihydroceramides (dhCers) and Cers. Both SKs and Des1 have interest as therapeutic targets. Here we show that SKI II is a noncompetitive inhibitor (Ki = 0.3 μM) of Des1 activity with effect also in intact cells without modifying Des1 protein levels. Molecular modeling studies support that the SKI II-induced decrease in Des1 activity could result from inhibition of NADH-cytochrome b5 reductase. SKI II, but not the SK1-specific inhibitor PF-543, provoked a remarkable accumulation of dhCers and their metabolites, while both SKI II and PF-543 reduced S1P to almost undetectable levels. SKI II, but not PF543, reduced cell proliferation with accumulation of cells in the G0/G1 phase. SKI II, but not PF543, induced autophagy. These overall findings should be taken into account when using SKI II as a pharmacological tool, as some of the effects attributed to decreased S1P may actually be caused by augmented dhCers and/or their metabolites.
authors.affiliation: Research Unit on BioActive Molecules (RUBAM), Departments of Biomedicinal Chemistry Institute for Advanced Chemistry of Catalonia (IQAC-CSIC), 08034 Barcelona, Spain.
authors.forename: Francesca
authors.initials: F
authors.lastname: Cingolani
authors.affiliation: Research Unit on BioActive Molecules (RUBAM), Departments of Biomedicinal Chemistry Institute for Advanced Chemistry of Catalonia (IQAC-CSIC), 08034 Barcelona, Spain.
authors.forename: Mireia
authors.initials: M
authors.lastname: Casasampere
authors.affiliation: Research Unit on BioActive Molecules (RUBAM), Departments of Biomedicinal Chemistry Institute for Advanced Chemistry of Catalonia (IQAC-CSIC), 08034 Barcelona, Spain Faculty of Pharmacy, Unit of Pharmaceutical Chemistry (Associated Unit to CSIC), University of Barcelona, E-08028 Barcelona, Spain.
authors.forename: Pol
authors.initials: P
authors.lastname: Sanllehí
authors.affiliation: Research Unit on BioActive Molecules (RUBAM), Departments of Biomedicinal Chemistry Institute for Advanced Chemistry of Catalonia (IQAC-CSIC), 08034 Barcelona, Spain.
authors.forename: Josefina
authors.initials: J
authors.lastname: Casas
authors.affiliation: Biological Chemistry and Molecular Modeling, Institute for Advanced Chemistry of Catalonia (IQAC-CSIC), 08034 Barcelona, Spain.
authors.forename: Jordi
authors.initials: J
authors.lastname: Bujons
authors.affiliation: Research Unit on BioActive Molecules (RUBAM), Departments of Biomedicinal Chemistry Institute for Advanced Chemistry of Catalonia (IQAC-CSIC), 08034 Barcelona, Spain.
authors.forename: Gemma
authors.initials: G
authors.lastname: Fabrias
mesh_terms: D001343:Autophagy / Q000187:drug effects*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D016193:G1 Phase / Q000187:drug effects; D006367:HeLa Cells; D006801:Humans; D000432:Methanol; D010088:Oxidoreductases / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors*; D011759:Pyrrolidines / Q000494:pharmacology; D016192:Resting Phase, Cell Cycle / Q000187:drug effects; D013450:Sulfones / Q000494:pharmacology; D000099157:Sphingosine Kinase
chemical_list: D004791:Enzyme Inhibitors; D000432:Methanol; D010088:Oxidoreductases; D017853:Phosphotransferases (Alcohol Group Acceptor); D011759:Pyrrolidines; D013450:Sulfones; D000099157:Sphingosine Kinase; C573330:PF-543; C108138:dihydroceramide desaturase; C000594250:sphingosine kinase 2, human
keywords: autophagy; cell cycle; enzyme inhibition; mass spectrometry; molecular docking; reduced nicotinamide adenine dinucleotide-cytochrome b5 reductase; sphingolipids; sphingosine kinase inhibitor II