title: Phosphorylation of the 48-kDa subunit of the glycine receptor by protein kinase C.
abstract: The postsynaptic glycine receptor purified from rat spinal cord is rapidly and specifically phosphorylated by protein kinase C. The target for phosphorylation is the strychnine-binding subunit of the receptor (molecular mass of approximately 48 kDa), which is phosphorylated on serine residues to a final stoichiometry of approximately 0.8 mol of phosphate/mol of subunit. The 48-kDa phosphoprotein was analyzed by proteolytic cleavage and peptide mapping in order to localize the site of phosphorylation within the receptor molecule. Examination of the 32P-labeled receptor fragments generated by digestion with N-chlorosuccinimide, cyanogen bromide, and endoproteinase lysine C and of the deduced amino acid sequence of the 48-kDa protein (Grenningloh, G., Rienitz, A., Schmitt, B., Methfessel, C., Zensen, M., Beyreuther, K., Gundelfinger, E. D., and Betz, H. (1987) Nature 328, 215-220) indicates that the phosphorylation site is located in a region corresponding to the major intracellular loop of the predicted structure of the glycine receptor subunit and suggests serine 391 as the phosphorylated residue. In fact, a synthetic peptide corresponding to residues 384-392 of the 48-kDa subunit was specifically phosphorylated by protein kinase C. Moreover, tryptic digests of this phosphopeptide and of the phosphorylated 48-kDa subunit of the glycine receptor migrated to the same position in two-dimensional peptide mapping. Furthermore, antibodies elicited against peptide 384-392 were shown to inhibit the protein kinase C-dependent phosphorylation of the 48-kDa polypeptide. Interestingly, the relative position of the phosphorylated domain is similar to those known or proposed to be phosphorylated in other ligand-gated ion channel receptor subunits, thus suggesting further the existence of a homologous regulatory region in these receptor proteins.
authors.affiliation: Departamento de Biología Molecular, Universidad Autónoma de Madrid-Consejo Superior de Investigaciones Científicas, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Ruiz-Gómez
authors.forename: M L
authors.initials: ML
authors.lastname: Vaello
authors.forename: F
authors.initials: F
authors.lastname: Valdivieso
authors.forename: F
authors.initials: F
authors.lastname: Mayor
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000201:enzymology; D002462:Cell Membrane / Q000378:metabolism; D005998:Glycine / Q000378:metabolism; D007700:Kinetics; D046911:Macromolecular Substances; D008961:Models, Structural; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010449:Peptide Mapping; D010748:Phosphopeptides / Q000302:isolation & purification; D010766:Phosphorylation; D011487:Protein Conformation; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D018009:Receptors, Glycine; D017981:Receptors, Neurotransmitter / Q000302:isolation & purification / Q000378:metabolism*; D013116:Spinal Cord / Q000378:metabolism
chemical_list: D046911:Macromolecular Substances; D010748:Phosphopeptides; D018009:Receptors, Glycine; D017981:Receptors, Neurotransmitter; D011493:Protein Kinase C; D005998:Glycine