title: Sphingolipid metabolism is a crucial determinant of cellular fate in nonstimulated proliferating Madin-Darby canine kidney (MDCK) cells.
abstract: The present report was addressed to study the influence of sphingolipid metabolism in determining cellular fate. In nonstimulated proliferating Madin-Darby canine kidney (MDCK) cells, sphingolipid de novo synthesis is branched mainly to a production of sphingomyelin and ceramide, with a minor production of sphingosylphosphocholine, ceramide 1-phosphate, and sphingosine 1-phosphate. Experiments with (32)P as a radioactive precursor showed that sphingosine 1-phosphate is produced mainly by a de novo independent pathway. Enzymatic inhibition of the de novo pathway and ceramide synthesis affected cell number and viability only slightly, without changing sphingosine 1-phosphate production. By contrast, inhibition of sphingosine kinase-1 activity provoked a significant reduction in both cell number and viability in a dose-dependent manner. When sphingolipid metabolism was studied, an increase in de novo formed ceramide was found, which correlated with the concentration of enzyme inhibitor and the reduction in cell number and viability. Knockdown of sphingosine kinase-1 expression also induced an accumulation of de novo synthesized ceramide, provoking a slight reduction in cell number and viability similar to that induced by a low concentration of the sphingosine kinase inhibitor. Taken together, our results indicate that the level of de novo formed ceramide is controlled by the synthesis of sphingosine 1-phosphate, which appears to occur through a de novo synthesis-independent pathway, most probably the salvage pathway, that is responsible for the MDCK cell fate, suggesting that under proliferating conditions, a dynamic interplay exists between the de novo synthesis and the salvage pathway.
authors.affiliation: Departments of Cell Biology and Biological Chemistry, School of Pharmacy and Biochemistry, University of Buenos Aires, C1113AAD Buenos Aires, Argentina; Instituto de Química y Fisicoquímica Biológica-Consejo Nacional de Investigaciones Cientificas y Técnicas, C1113AAD Buenos Aires, Argentina.
authors.forename: Francisco Leocata
authors.initials: FL
authors.lastname: Nieto
authors.affiliation: Departments of Cell Biology and Biological Chemistry, School of Pharmacy and Biochemistry, University of Buenos Aires, C1113AAD Buenos Aires, Argentina; Instituto de Química y Fisicoquímica Biológica-Consejo Nacional de Investigaciones Cientificas y Técnicas, C1113AAD Buenos Aires, Argentina.
authors.forename: Lucila G
authors.initials: LG
authors.lastname: Pescio
authors.affiliation: Departments of Cell Biology and Biological Chemistry, School of Pharmacy and Biochemistry, University of Buenos Aires, C1113AAD Buenos Aires, Argentina; Instituto de Química y Fisicoquímica Biológica-Consejo Nacional de Investigaciones Cientificas y Técnicas, C1113AAD Buenos Aires, Argentina.
authors.forename: Nicolás O
authors.initials: NO
authors.lastname: Favale
authors.affiliation: Instituto de Química y Fisicoquímica Biológica-Consejo Nacional de Investigaciones Cientificas y Técnicas, C1113AAD Buenos Aires, Argentina.
authors.forename: Ana M
authors.initials: AM
authors.lastname: Adamo
authors.affiliation: Departments of Cell Biology and Biological Chemistry, School of Pharmacy and Biochemistry, University of Buenos Aires, C1113AAD Buenos Aires, Argentina; Instituto de Química y Fisicoquímica Biológica-Consejo Nacional de Investigaciones Cientificas y Técnicas, C1113AAD Buenos Aires, Argentina. Electronic address: speziale@ffyb.uba.ar.
authors.forename: Norma B
authors.initials: NB
authors.lastname: Sterin-Speziale
mesh_terms: D000818:Animals; D002460:Cell Line; D019070:Cell Lineage; D049109:Cell Proliferation; D002518:Ceramides / Q000378:metabolism; D004285:Dogs; D004789:Enzyme Activation; D037341:Fumonisins / Q000494:pharmacology; D008954:Models, Biological; D010088:Oxidoreductases / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D051102:Serine C-Palmitoyltransferase / Q000037:antagonists & inhibitors; D013107:Sphingolipids / Q000378:metabolism*; D013997:Time Factors; D000099157:Sphingosine Kinase
chemical_list: D002518:Ceramides; D037341:Fumonisins; D010088:Oxidoreductases; D017853:Phosphotransferases (Alcohol Group Acceptor); D051102:Serine C-Palmitoyltransferase; D013107:Sphingolipids; D000099157:Sphingosine Kinase; C056933:fumonisin B1; C108138:dihydroceramide desaturase