title: Enzyme Activities of the Ceramide Synthases CERS2-6 Are Regulated by Phosphorylation in the C-terminal Region.
abstract: Ceramide and complex sphingolipids regulate important cellular functions including cell growth, apoptosis, and signaling. Dysregulation of sphingolipid metabolism leads to pathological consequences such as sphingolipidoses and insulin resistance. Ceramides in mammals vary greatly in their acyl-chain composition: six different ceramide synthase isozymes (CERS1-6) that exhibit distinct substrate specificity and tissue distribution account for this diversity. In the present study, we demonstrated that CERS2-6 were phosphorylated at the cytoplasmic C-terminal regions. Most of the phosphorylated residues conformed to a consensus motif for phosphorylation by casein kinase 2 (CK2), and treatment of cells with the CK2-specific inhibitor CX-4945 lowered the phosphorylation levels of CERS2, -4, -5, and -6. Phosphorylation of CERS2 was especially important for its catalytic activity, acting mainly by increasing itsVmaxvalue. Phosphorylation modestly increased the catalytic activities of CERS4 and -5 and mildly increased those of CERS3 and -6. Dephosphorylation of endogenous ceramide synthases in the mouse brain led to severely reduced activity toward the Cers2 substrates C22:0/C24:0-CoAs and modestly reduced activity toward the Cers5/6 substrate C16:0-CoA. These results suggest that the phosphorylation of ceramide synthases may be a key regulatory point in the control of the distribution and levels of sphingolipids of various acyl-chain lengths.
authors.affiliation: From the Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-ku, Sapporo 060-0812, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Sassa
authors.affiliation: From the Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-ku, Sapporo 060-0812, Japan.
authors.forename: Taisuke
authors.initials: T
authors.lastname: Hirayama
authors.affiliation: From the Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-ku, Sapporo 060-0812, Japan kihara@pharm.hokudai.ac.jp.
authors.forename: Akio
authors.initials: A
authors.lastname: Kihara
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism*; D047390:Casein Kinase II / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D009287:Naphthyridines / Q000494:pharmacology; D010619:Phenazines; D010766:Phosphorylation / Q000187:drug effects / Q000502:physiology; D017434:Protein Structure, Tertiary; D013107:Sphingolipids / Q000096:biosynthesis* / Q000235:genetics; D051049:Sphingosine N-Acyltransferase / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity / Q000187:drug effects / Q000502:physiology
chemical_list: D009287:Naphthyridines; D010619:Phenazines; D013107:Sphingolipids; C555142:silmitasertib; D051049:Sphingosine N-Acyltransferase; D047390:Casein Kinase II
keywords: casein kinase 2; ceramide synthase; fatty acid; lipid; protein phosphorylation; sphingolipid