Title: Regulation of brain glutamate metabolism by nitric oxide and S-nitrosylation.
Authors: Raju, Karthik; Doulias, Paschalis-Thomas; Evans, Perry; Krizman, Elizabeth N; Jackson, Joshua G; Horyn, Oksana; Daikhin, Yevgeny; Nissim, Ilana; Yudkoff, Marc; Nissim, Itzhak; Sharp, Kim A; Robinson, Michael B; Ischiropoulos, Harry
Published In Sci Signal, (2015 Jul 07)
Abstract: Nitric oxide (NO) is a signaling intermediate during glutamatergic neurotransmission in the central nervous system (CNS). NO signaling is in part accomplished through cysteine S-nitrosylation, a posttranslational modification by which NO regulates protein function and signaling. In our investigation of the protein targets and functional impact of S-nitrosylation in the CNS under physiological conditions, we identified 269 S-nitrosocysteine residues in 136 proteins in the wild-type mouse brain. The number of sites was significantly reduced in the brains of mice lacking endothelial nitric oxide synthase (eNOS(-/-)) or neuronal nitric oxide synthase (nNOS(-/-)). In particular, nNOS(-/-) animals showed decreased S-nitrosylation of proteins that participate in the glutamate/glutamine cycle, a metabolic process by which synaptic glutamate is recycled or oxidized to provide energy. (15)N-glutamine-based metabolomic profiling and enzymatic activity assays indicated that brain extracts from nNOS(-/-) mice converted less glutamate to glutamine and oxidized more glutamate than those from mice of the other genotypes. GLT1 [also known as EAAT2 (excitatory amino acid transporter 2)], a glutamate transporter in astrocytes, was S-nitrosylated at Cys(373) and Cys(561) in wild-type and eNOS(-/-) mice, but not in nNOS(-/-) mice. A form of rat GLT1 that could not be S-nitrosylated at the equivalent sites had increased glutamate uptake compared to wild-type GLT1 in cells exposed to an S-nitrosylating agent. Thus, NO modulates glutamatergic neurotransmission through the selective, nNOS-dependent S-nitrosylation of proteins that govern glutamate transport and metabolism.
PubMed ID: 26152695
MeSH Terms: Amino Acid Sequence; Animals; Blotting, Western; Brain/metabolism*; Chromatography, Liquid; Cysteine/analogs & derivatives; Cysteine/genetics; Cysteine/metabolism*; Excitatory Amino Acid Transporter 2/genetics; Excitatory Amino Acid Transporter 2/metabolism; Glutamic Acid/metabolism*; Glutamine/metabolism; HEK293 Cells; Humans; Male; Mice, Inbred C57BL; Mice, Knockout; Molecular Sequence Data; Mutation; Nitric Oxide Synthase Type I/genetics; Nitric Oxide Synthase Type I/metabolism; Nitric Oxide Synthase Type III/genetics; Nitric Oxide Synthase Type III/metabolism; Nitric Oxide/metabolism*; Proteome/metabolism; Proteomics/methods; Rats; S-Nitrosothiols/metabolism; Tandem Mass Spectrometry