A dominant role of GTRAP3-18 in neuronal glutathione synthesis.
ABSTRACT Glutathione is an essential reductant which protects cells and is reduced in neurodegenerative disorders such as Parkinson's and Alzheimer's diseases. Neurons rely mainly on extracellular cysteine for glutathione synthesis and a cysteine transporter termed excitatory amino acid carrier 1 (EAAC1). However, the mechanisms underlying neuronal cysteine uptake have remained elusive. Herein, we show glutamate transport-associated protein for EAAC1 (GTRAP3-18) to interact with EAAC1 at the plasma membrane and thereby regulate neuronal glutathione levels. Glutathione increased in the mouse brain as well as in primary cultured neurons, when the GTRAP3-18 protein level was decreased by genetic manipulations, whereas glutathione decreased when GTRAP3-18 was increased. Furthermore, glutathione contents that had been increased, by a translocator and activator of EAAC1, were suppressed by increased cell surface GTRAP3-18 protein. Our results demonstrate GTRAP3-18 to dominantly and negatively determine the intracellular glutathione contents in neurons.
Article: JWA regulates XRCC1 and functions as a novel base excision repair protein in oxidative-stress-induced DNA single-strand breaks.[show abstract] [hide abstract]
ABSTRACT: JWA was recently demonstrated to be involved in cellular responses to environmental stress including oxidative stress. Although it was found that JWA protected cells from reactive oxygen species-induced DNA damage, upregulated base excision repair (BER) protein XRCC1 and downregulated PARP-1, the molecular mechanism of JWA in regulating the repair of DNA single-strand breaks (SSBs) is still unclear. Our present studies demonstrated that a reduction in JWA protein levels in cells resulted in a decrease of SSB repair capacity and hypersensitivity to DNA-damaging agents such as methyl methanesulfonate and hydrogen peroxide. JWA functioned as a repair protein by multi-interaction with XRCC1. On the one hand, JWA was translocated into the nucleus by the carrier protein XRCC1 and co-localized with XRCC1 foci after oxidative DNA damage. On the other hand, JWA via MAPK signaling pathway regulated nuclear factor E2F1, which further transcriptionally regulated XRCC1. In addition, JWA protected XRCC1 protein from ubiquitination and degradation by proteasome. These findings indicate that JWA may serve as a novel regulator of XRCC1 in the BER protein complex to facilitate the repair of DNA SSBs.Nucleic Acids Research 03/2009; 37(6):1936-50. · 8.03 Impact Factor
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ABSTRACT: Glutathione (GSH) is a tripeptide consisting of glutamate, cysteine, and glycine; it has a variety of functions in the central nervous system. Brain GSH depletion is considered a preclinical sign in age-related neurodegenerative diseases, and it promotes the subsequent processes toward neurotoxicity. A neuroprotective mechanism accomplished by increasing GSH synthesis could be a promising approach in the treatment of neurodegenerative diseases. In neurons, cysteine is the rate-limiting substrate for GSH synthesis. Excitatory amino acid carrier 1 (EAAC1) is a neuronal cysteine/glutamate transporter in the brain. EAAC1 translocation to the plasma membrane promotes cysteine uptake, leading to GSH synthesis, while being negatively regulated by glutamate transport associated protein 3-18 (GTRAP3-18). Our recent studies have suggested GTRAP3-18 as an inhibitory factor for neuronal GSH synthesis. Inhibiting GTRAP3-18 function is an endogenous mechanism to increase neuron-specific GSH synthesis in the brain. This review gives an overview of EAAC1-mediated GSH synthesis, and its regulatory mechanisms by GTRAP3-18 in the brain, and a potential approach against neurodegeneration.International Journal of Molecular Sciences 01/2012; 13(9):12017-35. · 2.60 Impact Factor
Article: Nuclear factor erythroid 2-related factor 2 facilitates neuronal glutathione synthesis by upregulating neuronal excitatory amino acid transporter 3 expression.[show abstract] [hide abstract]
ABSTRACT: Astrocytes support neuronal antioxidant capacity by releasing glutathione, which is cleaved to cysteine in brain extracellular space. Free cysteine is then taken up by neurons through excitatory amino acid transporter 3 [EAAT3; also termed Slc1a1 (solute carrier family 1 member 1)] to support de novo glutathione synthesis. Activation of the nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant responsive element (ARE) pathway by oxidative stress promotes astrocyte release of glutathione, but it remains unknown how this release is coupled to neuronal glutathione synthesis. Here we evaluated transcriptional regulation of the neuronal cysteine transporter EAAT3 by the Nrf2-ARE pathway. Nrf2 activators and Nrf2 overexpression both produced EAAT3 transcriptional activation in C6 cells. A conserved ARE-related sequence was found in the EAAT3 promoter of several mammalian species. This ARE-related sequence was bound by Nrf2 in mouse neurons in vivo as observed by chromatin immunoprecipitation. Chemical activation of the Nrf2-ARE pathway in mouse brain increased both neuronal EAAT3 levels and neuronal glutathione content, and these effects were abrogated in mice genetically deficient in either Nrf2 or EAAT3. Selective overexpression of Nrf2 in brain neurons by lentiviral gene transfer was sufficient to upregulate both neuronal EAAT3 protein and glutathione content. These findings identify a mechanism whereby Nrf2 activation can coordinate astrocyte glutathione release with neuronal glutathione synthesis through transcriptional upregulation of neuronal EAAT3 expression.Journal of Neuroscience 05/2011; 31(20):7392-401. · 7.11 Impact Factor