Professional Education

  • Doctor of Philosophy, University of Pennsylvania (2015)

Stanford Advisors


All Publications

  • Regulation of brain glutamate metabolism by nitric oxide and S-nitrosylation SCIENCE SIGNALING Raju, K., Doulias, P., Evans, P., Krizman, E. N., Jackson, J. G., Horyn, O., Daikhin, Y., Nissim, I., Yudkoff, M., Nissim, I., Sharp, K. A., Robinson, M. B., Ischiropoulos, H. 2015; 8 (384)


    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.

    View details for DOI 10.1126/scisignal.aaa4312

    View details for Web of Science ID 000357617600002

    View details for PubMedID 26152695

  • Nitric oxide regulates mitochondrial fatty acid metabolism through reversible protein S-nitrosylation. Science signaling Doulias, P., Tenopoulou, M., Greene, J. L., Raju, K., Ischiropoulos, H. 2013; 6 (256): rs1-?


    Cysteine S-nitrosylation is a posttranslational modification by which nitric oxide regulates protein function and signaling. Studies of individual proteins have elucidated specific functional roles for S-nitrosylation, but knowledge of the extent of endogenous S-nitrosylation, the sites that are nitrosylated, and the regulatory consequences of S-nitrosylation remains limited. We used mass spectrometry-based methodologies to identify 1011 S-nitrosocysteine residues in 647 proteins in various mouse tissues. We uncovered selective S-nitrosylation of enzymes participating in glycolysis, gluconeogenesis, tricarboxylic acid cycle, and oxidative phosphorylation, indicating that this posttranslational modification may regulate metabolism and mitochondrial bioenergetics. S-nitrosylation of the liver enzyme VLCAD [very long chain acyl-coenzyme A (CoA) dehydrogenase] at Cys(238), which was absent in mice lacking endothelial nitric oxide synthase, improved its catalytic efficiency. These data implicate protein S-nitrosylation in the regulation of β-oxidation of fatty acids in mitochondria.

    View details for DOI 10.1126/scisignal.2003252

    View details for PubMedID 23281369

  • Strategies and tools to explore protein S-nitrosylation BIOCHIMICA ET BIOPHYSICA ACTA-GENERAL SUBJECTS Raju, K., Doulias, P., Tenopoulou, M., Greene, J. L., Ischiropoulos, H. 2012; 1820 (6): 684-688


    A biochemical pathway by which nitric oxide accomplishes functional diversity is the specific modification of protein cysteine residues to form S-nitrosocysteine. This post-translational modification, S-nitrosylation, impacts protein function, interactions and location. However, comprehensive studies exploring protein signaling pathways or interrelated protein clusters that are regulated by S-nitrosylation have not been performed on a global scale.To provide insights to these important biological questions, sensitive, validated and quantitative proteomic approaches are required. This review summarizes current approaches for the global identification of S-nitrosylated proteins.The application of novel methods for identifying S-nitrosylated proteins, especially when combined with mass-spectrometry based proteomics to provide site-specific identification of the modified cysteine residues, promises to deliver critical clues for the regulatory role of this dynamic posttranslational modification in cellular processes.Though several studies have established S-nitrosylation as a regulator of protein function in individual proteins, the biological chemistry and the structural elements that govern the specificity of this modification in vivo are vastly unknown. Additionally, a gap in knowledge exists concerning the potential global regulatory role(s) this modification may play in cellular physiology. By further studying S-nitrosylation at a global scale, a greater appreciation of nitric oxide and protein S-nitrosylation in cellular function can be achieved. This article is part of a Special Issue entitled Regulation of Cellular Processes by S-nitrosylation.

    View details for DOI 10.1016/j.bbagen.2011.05.009

    View details for Web of Science ID 000304288600003

    View details for PubMedID 21651963

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