title: Regulation of ceramide synthase by casein kinase 2-dependent phosphorylation in Saccharomyces cerevisiae.
abstract: Complex sphingolipids are important components of eukaryotic cell membranes and, together with their biosynthetic precursors, including sphingoid long chain bases and ceramides, have important signaling functions crucial for cell growth and survival. Ceramides are produced at the endoplasmic reticulum (ER) membrane by a multicomponent enzyme complex termed ceramide synthase (CerS). In budding yeast, this complex is composed of two catalytic subunits, Lac1 and Lag1, as well as an essential regulatory subunit, Lip1. Proper formation of ceramides by CerS has been shown previously to require the Cka2 subunit of casein kinase 2 (CK2), a ubiquitous enzyme with multiple cellular functions, but the precise mechanism involved has remained unidentified. Here we present evidence that Lac1 and Lag1 are direct targets for CK2 and that phosphorylation at conserved positions within the C-terminal cytoplasmic domain of each protein is required for optimal CerS activity. Our data suggest that phosphorylation of Lac1 and Lag1 is important for proper localization and distribution of CerS within the ER membrane and that phosphorylation of these sites is functionally linked to the COP I-dependent C-terminal dilysine ER retrieval pathway. Together, our data identify CK2 as an important regulator of sphingolipid metabolism, and additionally, because both ceramides and CK2 have been implicated in the regulation of cancer, our findings may lead to an enhanced understanding of their relationship in health and disease.
authors.affiliation: From the Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, California 95616.
authors.forename: Tara
authors.initials: T
authors.lastname: Fresques
authors.affiliation: From the Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, California 95616.
authors.forename: Brad
authors.initials: B
authors.lastname: Niles
authors.affiliation: From the Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, California 95616.
authors.forename: Sofia
authors.initials: S
authors.lastname: Aronova
authors.affiliation: From the Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, California 95616.
authors.forename: Huzefa
authors.initials: H
authors.lastname: Mogri
authors.affiliation: From the Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, California 95616.
authors.forename: Taha
authors.initials: T
authors.lastname: Rakhshandehroo
authors.affiliation: From the Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, California 95616 tpowers@ucdavis.edu.
authors.forename: Ted
authors.initials: T
authors.lastname: Powers
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D047390:Casein Kinase II / Q000378:metabolism*; D020134:Catalytic Domain; D002518:Ceramides / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000378:metabolism*; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D015398:Signal Transduction; D013107:Sphingolipids / Q000737:chemistry
chemical_list: D002518:Ceramides; C087436:LAG1 protein, S cerevisiae; D008565:Membrane Proteins; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D013107:Sphingolipids; D010088:Oxidoreductases; C513563:LAC1 protein, S cerevisiae; C108138:dihydroceramide desaturase; D047390:Casein Kinase II
keywords: Endoplasmic Reticulum (ER); Lipid; Membrane; Protein Kinase; Signaling; Sphingolipids; Yeast