<p>Gliomas are tumors of the central nervous system for which improvements in treatment are critically needed. Mutations in IDH1 and IDH2, which encode the cytosolic and mitochondrial NADP+-dependent isocitrate dehydrogenases, respectively, are frequent in gliomas. Here, we summarize recent literature concerning gliomas, the normal cellular functions of IDH1/2, the epidemiology of IDH1/2 mutations, and the understanding of the function of IDH1/2 mutations in cancer. We then show in vitro using liquid chromatography-mass spectrometry that a function of many IDH1/2 mutations is to produce 2-hydroxyglutarate. Next, we use a mass spectrometry based platform to characterize metabolic changes in a glioma cell line expressing IDH1/2 mutants and show that the IDH mutants are associated with lowered N-acetylated amino acids both in this cell line model and in primary tumor tissue. Finally, we develop and characterize a Drosophila melanogaster (fruit fly) model of IDH1/2-mutated cancer by expressing the mutated Drosophila homolog of IDH1 in fly tissues using the UAS-Gal4 binary expression system. These results delineate downstream molecular players that likely play a role in IDH1/2-mutated cancer and provide a model organism for interrogation of genetic networks that interact with IDH1/2 mutation. These findings refine our understanding of glioma pathogenesis and may inform the design of new glioma therapies.</p> / Dissertation

Ischemic strokes cause excessive release of glutamate, leading to overactivation of N-methyl-D-aspartate receptors (NMDARs) and excitotoxicity-induced neuronal death. For this reason, inhibition of NMDARs has been a central focus in identifying mechanisms to avert this extensive neuronal damage. N-acetyl-aspartyl-glutamate (NAAG), the most abundant neuropeptide in the brain, is neuroprotective in ischemic conditions in vivo. Despite this evidence, the exact mechanism underlying its neuroprotection, and more specifically its effect on NMDARs, is currently unknown due to conflicting results in the literature. Here, we uncover a pH-dependent and subunit specific action of NAAG on NMDARs. Using whole-cell electrophysiological recordings on acute hippocampal slices from adult mice and on HEK293 cells, we found that NAAG increases synaptic GluN2A-containing NMDAR excitatory postsynaptic currents (EPSCs), while effectively decreasing extrasynaptic GluN2B-containing NMDAR EPSCs in physiological pH. Intriguingly, the results of our study further show that in low pH, which is a physiological occurrence during ischemia, NAAG depresses GluN2A-containing NMDAR EPSCs and amplifies its inhibitory effect on GluN2B-containing NMDAR EPSCs, as well as upregulates the surface expression of the GluN2A subunit. Altogether, our data demonstrate that NAAG has differential effects on NMDAR function based on subunit composition and extracellular pH levels. These findings suggest that the role of NAAG as a neuroprotective agent during an ischemic stroke is likely mediated by its ability to reduce NMDAR excitation. The inhibitory effect of NAAG on NMDARs and its enhanced function in acidic conditions makes NAAG a prime therapeutic agent for the treatment of ischemic events.