title: The regulation of glycine transporter GLYT1 is mainly mediated by protein kinase Calpha in C6 glioma cells.
abstract: Glycine has been shown to possess important functions as a bidirectional neurotransmitter. At synaptic clefts, the concentration of glycine is tightly regulated by the uptake of glycine released from nerve terminals into glial cells by the transporter GLYT1. It has been recently demonstrated that protein kinase C (PKC) mediates the downregulation of GLYT1 activity in several cell systems. However, it remains to be elucidated which subtypes of PKC might be important in the regulation of GLYT1 activity. In this study, we attempted to make clear the mechanism of the phorbol 12-myristate 13-acetate (PMA)-suppressed uptake of glycine in C6 glioma cells which have the native expression of GLYT1. In C6 cells, the expression of PKCalpha, PKCdelta, and PKCvarepsilon of the PMA-activated subtypes was detected. The PMA-suppressed action was fully reversed by the removal of both extracellular and intracellular Ca(2+). Furthermore, the inhibitory effects of PMA or thymeleatoxin (THX), which is a selective activator of conventional PKC (cPKC), were blocked by the downregulation of all PKCs expressed in C6 cells by long-term incubation with THX, or pretreatment with GF109203X or Gö6983, which are broad inhibitors of PKC, or Gö6976, a selective inhibitor of cPKC. On the other hand, treatment of C6 cells with ingenol, a selective activator of novel PKCs, especially PKCdelta and PKCvarepsilon, did not affect the transport of glycine. Silencing of PKCdelta expression by using RNA interference or pretreatment with the inhibitor peptide for PKCvarepsilon had no effect on the PMA-suppressed uptake of glycine. Together, these results suggest PKCalpha to be a crucial factor in the regulation of glycine transport in C6 cells.
authors.affiliation: Department of Dental Pharmacology, Hiroshima University Graduate School of Biomedical Sciences, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan. mnori@hiroshima-u.ac.jp
authors.forename: Norimitsu
authors.initials: N
authors.lastname: Morioka
authors.forename: Joynal Md
authors.initials: JM
authors.lastname: Abdin
authors.forename: Katsuya
authors.initials: K
authors.lastname: Morita
authors.forename: Tomoya
authors.initials: T
authors.lastname: Kitayama
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Nakata
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Dohi
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000201:enzymology*; D002118:Calcium / Q000378:metabolism; D002273:Carcinogens / Q000494:pharmacology; D045744:Cell Line, Tumor; D004224:Diterpenes / Q000494:pharmacology; D015536:Down-Regulation / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005910:Glioma; D005998:Glycine / Q000378:metabolism*; D050487:Glycine Plasma Membrane Transport Proteins / Q000378:metabolism*; D007527:Isoenzymes / Q000378:metabolism; D010703:Phorbol Esters / Q000494:pharmacology; D051571:Protein Kinase C-alpha / Q000378:metabolism*; D051745:Protein Kinase C-delta / Q000235:genetics / Q000378:metabolism; D051744:Protein Kinase C-epsilon / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D051381:Rats; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D002273:Carcinogens; D004224:Diterpenes; D004791:Enzyme Inhibitors; D050487:Glycine Plasma Membrane Transport Proteins; D007527:Isoenzymes; D010703:Phorbol Esters; C493266:Slc6a9 protein, rat; C080287:thymeleatoxin; D051571:Protein Kinase C-alpha; D051745:Protein Kinase C-delta; D051744:Protein Kinase C-epsilon; C008125:ingenol; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium; D005998:Glycine