title: Mouse Sphingosine Kinase 1a Is Negatively Regulated through Conventional PKC-Dependent Phosphorylation at S373 Residue.
abstract: Sphingosine kinase is a lipid kinase that converts sphingosine into sphingosine-1-phosphate, an important signaling molecule with intracellular and extracellular functions. Although diverse extracellular stimuli influence cellular sphingosine kinase activity, the molecular mechanisms underlying its regulation remain to be clarified. In this study, we investigated the phosphorylation-dependent regulation of mouse sphingosine kinase (mSK) isoforms 1 and 2. mSK1a was robustly phosphorylated in response to extracellular stimuli such as phorbol ester, whereas mSK2 exhibited a high basal level of phosphorylation in quiescent cells regardless of agonist stimulation. Interestingly, phorbol ester-induced phosphorylation of mSK1a correlated with suppression of its activity. Chemical inhibition of conventional PKCs (cPKCs) abolished mSK1a phosphorylation, while overexpression of PKCα, a cPKC isoform, potentiated the phosphorylation, in response to phorbol ester. Furthermore, an in vitro kinase assay showed that PKCα directly phosphorylated mSK1a. In addition, phosphopeptide mapping analysis determined that the S373 residue of mSK1a was the only site phosphorylated by cPKC. Interestingly, alanine substitution of S373 made mSK1a refractory to the inhibitory effect of phorbol esters, whereas glutamate substitution of the same residue resulted in a significant reduction in mSK1a activity, suggesting the significant role of this phosphorylation event. Taken together, we propose that mSK1a is negatively regulated through cPKC-dependent phosphorylation at S373 residue.
authors.affiliation: Department of Brain-Cognitive Science, Daegu-Gyeongbuk Institute of Science and Technology (DGIST), Hyeonpung-myeon, Dalseong-gun, Daegu, Republic of Korea.
authors.forename: Yong-Seok
authors.initials: YS
authors.lastname: Oh
authors.affiliation: Department of Biological Sciences, Ulsan National Institute of Science and Technology (UNIST), Ulsan, Republic of Korea.
authors.forename: Sun Sik
authors.initials: SS
authors.lastname: Bae
authors.affiliation: Department of Life Science, Division of Molecular and Life Science, Pohang University of Science and Technology, Pohang, Republic of Korea.
authors.forename: Jong Bae
authors.initials: JB
authors.lastname: Park
authors.affiliation: Department of Life Science, Division of Molecular and Life Science, Pohang University of Science and Technology, Pohang, Republic of Korea.
authors.forename: Sang Hoon
authors.initials: SH
authors.lastname: Ha
authors.affiliation: Department of Life Science, Division of Molecular and Life Science, Pohang University of Science and Technology, Pohang, Republic of Korea.
authors.forename: Sung Ho
authors.initials: SH
authors.lastname: Ryu
authors.affiliation: Department of Biological Sciences, Ulsan National Institute of Science and Technology (UNIST), Ulsan, Republic of Korea.
authors.forename: Pann-Ghill
authors.initials: PG
authors.lastname: Suh
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D006801:Humans; D051379:Mice; D009154:Mutation; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D000099157:Sphingosine Kinase
chemical_list: D017853:Phosphotransferases (Alcohol Group Acceptor); D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D000099157:Sphingosine Kinase