According to GOSPEL: Filling in the GAP(DH) of NO-Mediated Neurotoxicity
2009; Cell Press; Volume: 63; Issue: 1 Linguagem: Inglês
10.1016/j.neuron.2009.06.013
ISSN1097-4199
AutoresTomohiro Nakamura, Stuart A. Lipton,
Tópico(s)Adipose Tissue and Metabolism
ResumoIn addition to its role in glycolysis, GAPDH has been implicated as a mediator of neurotoxicity triggered by nitrosative stress. In this issue of Neuron, Sen et al. identify a novel, negative regulator of this GAPDH neurotoxic pathway termed GOSPEL, which, like GAPDH itself, is regulated by S-nitrosylation. In addition to its role in glycolysis, GAPDH has been implicated as a mediator of neurotoxicity triggered by nitrosative stress. In this issue of Neuron, Sen et al. identify a novel, negative regulator of this GAPDH neurotoxic pathway termed GOSPEL, which, like GAPDH itself, is regulated by S-nitrosylation. Excess generation of reactive oxygen or nitrogen species (ROS/RNS) is thought to be a primary mediator of neuronal cell injury and death in neurodegenerative disorders. For example, nitric oxide (NO) participates in neurodestructive events via either formation of toxic peroxynitrite as a result of reaction with superoxide anion or S-nitrosylation of regulatory protein groups. S-Nitrosylation is a redox reaction, representing a covalent addition of an NO group to a critical cysteine thiol/sulfhydryl (or more properly thiolate anion, RS−) to produce an S-nitrosothiol (SNO) derivative. Such posttranslational modification can modulate the function or activity of target proteins to regulate broad aspects of bodily and brain function, including synaptic plasticity, neuronal development, protein misfolding, and cell death (Lipton et al., 1993Lipton S.A. Choi Y.-B. Pan Z.-H. Lei S.Z. Chen H.-S.V. Sucher N.J. Singel D.J. Loscalzo J. Stamler J.S. Nature. 1993; 364: 626-632Crossref PubMed Scopus (2231) Google Scholar, Hess et al., 2005Hess D.T. Matsumoto A. Kim S.O. Marshall H.E. Stamler J.S. Nat. Rev. Mol. Cell Biol. 2005; 6: 150-166Crossref PubMed Scopus (1590) Google Scholar, Nakamura and Lipton, 2007Nakamura T. Lipton S.A. Cell Death Differ. 2007; 14: 1305-1314Crossref PubMed Scopus (44) Google Scholar). Recent research has revealed that overproduction of NO negatively affects neuronal survival by S-nitrosylation of multiple substrates. For example, S-nitrosylation of Parkin, protein disulfide isomerase (PDI), or dynamin related protein 1 (Drp1) mediates protein misfolding or excessive mitochondrial fission, both of which contribute to the pathophysiology of neurodegenerative disorders (Nakamura and Lipton, 2007Nakamura T. Lipton S.A. Cell Death Differ. 2007; 14: 1305-1314Crossref PubMed Scopus (44) Google Scholar, Cho et al., 2009Cho D.H. Nakamura T. Fang J. Cieplak P. Godzik A. Gu Z. Lipton S.A. Science. 2009; 324: 102-105Crossref PubMed Scopus (757) Google Scholar). The laboratory of Solomon Snyder previously showed that S-nitrosylated GAPDH (SNO-GAPDH) triggers a nuclear signaling pathway leading to cell death (Hara et al., 2005Hara M.R. Agrawal N. Kim S.F. Cascio M.B. Fujimuro M. Ozeki Y. Takahashi M. Cheah J.H. Tankou S.K. Hester L.D. et al.Nat. Cell Biol. 2005; 7: 665-674Crossref PubMed Scopus (813) Google Scholar). GAPDH is a well-known glycolytic enzyme that plays a critical role in energy production, but mounting evidence suggests that GAPDH has multiple functions; the proapoptotic activity of nuclear GAPDH represents one such alternative pathway. The Snyder group had found that S-nitrosylation imbues upon GAPDH the ability to bind to the ubiquitin E3 ligase, Siah1, which harbors a nuclear localization signal (NLS), thereby escorting GAPDH into the nucleus. GAPDH then exerts its neurotoxic effects by stabilizing Siah1, enabling the degradation of nuclear substrates, such as nuclear receptor corepressor (N-CoR), via the ubiquitin E3 ligase activity of Siah1 (Figure 1). Nuclear GAPDH stimulates acetylation by p300/CBP, which in turn induces activation of various target proteins, including p53, to augment the cell death pathway (Sen et al., 2008Sen N. Hara M.R. Kornberg M.D. Cascio M.B. Bae B.I. Shahani N. Thomas B. Dawson T.M. Dawson V.L. Snyder S.H. Sawa A. Nat. Cell Biol. 2008; 10: 866-873Crossref PubMed Scopus (297) Google Scholar). The SNO-GAPDH cascade may play a role in the pathogenesis of several neurodegenerative diseases. Recent studies have shown in a cell culture model of Huntington's disease (HD) that mutant Huntingtin protein (mtHtt) can form a ternary complex with GAPDH and Siah1 (Bae et al., 2006Bae B.I. Hara M.R. Cascio M.B. Wellington C.L. Hayden M.R. Ross C.A. Ha H.C. Li X.J. Snyder S.H. Sawa A. Proc. Natl. Acad. Sci. USA. 2006; 103: 3405-3409Crossref PubMed Scopus (96) Google Scholar). Although mtHtt lacks an NLS, mtHtt can translocate to the nucleus and produce neurotoxicity in cell culture models (Martindale et al., 1998Martindale D. Hackam A. Wieczorek A. Ellerby L. Wellington C. McCutcheon K. Singaraja R. Kazemi-Esfarjani P. Devon R. Kim S.U. et al.Nat. Genet. 1998; 18: 150-154Crossref PubMed Scopus (410) Google Scholar). Reportedly, the mtHtt/SNO-GAPDH/Siah1 complex translocates to the nucleus, enabling mtHtt to contribute to this toxicity (Bae et al., 2006Bae B.I. Hara M.R. Cascio M.B. Wellington C.L. Hayden M.R. Ross C.A. Ha H.C. Li X.J. Snyder S.H. Sawa A. Proc. Natl. Acad. Sci. USA. 2006; 103: 3405-3409Crossref PubMed Scopus (96) Google Scholar). Supporting these findings, Senatorov et al., 2003Senatorov V.V. Charles V. Reddy P.H. Tagle D.A. Chuang D.M. Mol. Cell. Neurosci. 2003; 22: 285-297Crossref PubMed Scopus (61) Google Scholar found evidence for nuclear accumulation of GAPDH in a transgenic model of HD. Additionally, SNO-GAPDH may also contribute to the pathophysiology of Parkinson's disease (PD). The drug R-(−)-deprenyl (selegiline), which may ameliorate the progression of early-stage PD, appears to prevent S-nitrosylation of GAPDH both in cellular and animal models of PD (Hara et al., 2006Hara M.R. Thomas B. Cascio M.B. Bae B.I. Hester L.D. Dawson V.L. Dawson T.M. Sawa A. Snyder S.H. Proc. Natl. Acad. Sci. USA. 2006; 103: 3887-3889Crossref PubMed Scopus (192) Google Scholar). It is postulated that the binding of deprenyl to GAPDH interferes with the formation of SNO-GAPDH and its interaction with Siah1, thereby affording neuroprotection. Although these prior studies raised the possibility that the SNO-GAPDH pathway could serve as a potential molecular target for drug development, the precise mechanism that controls the proapoptotic activity of SNO-GAPDH remained elusive. The Snyder group now reports in this issue of Neuron that an endogenous inhibitor of the SNO-GAPDH cascade provides neuroprotection by interfering with the interaction between SNO-GAPDH and Siah1 (Sen et al., 2009Sen N. Hara M.R. Ahmad A.S. Cascio M.B. Kamiya A. Ehmsen J.T. Aggrawal N. Hester L. Doré S. Snyder S.H. Sawa A. Neuron. 2009; 63 (this issue): 81-91Abstract Full Text Full Text PDF PubMed Scopus (97) Google Scholar). Snyder and colleagues performed a yeast two-hybrid screen and identified a cytoplasmic, 52 kDa protein that binds to the N terminus of GAPDH. The protein, termed GOSPEL, is highly expressed in skeletal muscle, liver, heart, and brain. In brain, in situ hybridization revealed high levels of GOSPEL in cerebellar Purkinje cells and hippocampal CA1-3 pyramidal and dentate granule neurons; GAPDH also manifested increased expression in these areas. The amino acid sequence of GOSPEL is remarkably preserved among human, mouse, and rat, although GOSPEL does not contain any known functional domains. Binding of GOSPEL to GAPDH is dependent upon amino acids 160–200 in GOSPEL and 80–120 in GAPDH. Next, Sen et al., 2009Sen N. Hara M.R. Ahmad A.S. Cascio M.B. Kamiya A. Ehmsen J.T. Aggrawal N. Hester L. Doré S. Snyder S.H. Sawa A. Neuron. 2009; 63 (this issue): 81-91Abstract Full Text Full Text PDF PubMed Scopus (97) Google Scholar showed that NO regulated the GOSPEL/GAPDH interaction. One mechanism for NO production in neurons in vivo involves activation of N-methyl-d-aspartate (NMDA)-type glutamate receptors. Stimulation of NMDA receptors triggers Ca2+ influx, which in turn activates neuronal NO synthase (nNOS) as well as the generation of ROS (Hara et al., 2005Hara M.R. Agrawal N. Kim S.F. Cascio M.B. Fujimuro M. Ozeki Y. Takahashi M. Cheah J.H. Tankou S.K. Hester L.D. et al.Nat. Cell Biol. 2005; 7: 665-674Crossref PubMed Scopus (813) Google Scholar, Lipton, 2006Lipton S.A. Nat. Rev. Drug Discov. 2006; 5: 160-170Crossref PubMed Scopus (681) Google Scholar) (Figure 1). Excessive activation of NMDA receptors is implicated in neuronal damage in many neurological disorders, ranging from acute hypoxic-ischemic brain injury to chronic neurodegenerative diseases that include PD, HD, Alzheimer's disease, amyotrophic lateral sclerosis, and HIV-associated dementia. In the current study, Sen et al. found that NO produced by activation of NMDA receptors enhances the formation of the GOSPEL/GAPDH complex. S-Nitrosylation of GOSPEL, GAPDH, or both facilitates interaction between the two proteins. Notably, NMDA induces the formation of SNO-GOSPEL prior to the appearance of SNO-GAPDH, indicating that the interaction of SNO-GOSPEL and GAPDH precedes that of SNO-GAPDH and Siah1. Because of these temporal differences in sensitivity to S-nitrosylation, the authors speculate that the initial S-nitrosylation of GOSPEL represents a protective effect of NO under physiological conditions, while subsequent S-nitrosylation of GAPDH mediates the detrimental action of NO under pathophysiological conditions. S-Nitrosylation of GAPDH facilitates binding to Siah1 and consequent transport into the nucleus, with deadly results for the cell. Perhaps the most significant finding of the study is the molecular mechanism by which SNO-GOSPEL mediates neuroprotection. The authors conclude that SNO-GOSPEL competes with Siah1 for binding to (SNO)-GAPDH. Indeed, GOSPEL mutants that cannot bind to GAPDH or lack the nitrosylation site, thus decreasing the binding affinity for GAPDH, fail to protect neurons from NMDA insult. These results further confirm the notion that GOSPEL exerts its neuroprotective effect by inhibiting the formation of the SNO-GAPDH/Siah1 complex. The authors further confirmed this conclusion by showing that RNAi-mediated reduction of endogenous GOSPEL increases nuclear GAPDH translocation and subsequent neuronal cell death in response to NMDA exposure. Additionally, the authors found that this pathway is operative in vivo in mouse brain by showing that lentiviral-mediated delivery of GOSPEL, but not its GAPDH-deficient binding mutant, decreased injury caused by NMDA injection. Based on these findings, Sen et al. concluded that they had discovered GOSPEL as a new negative regulator of the SNO-GAPDH cascade, capable of enhancing neuronal survival in cell-based and animal models of neurodegenerative disease. The SNO-GOSPEL/SNO-GAPDH pathway may also be important in normal aging, which is thought to be associated with oxidative/nitrosative stress. Thus, this new work characterizes a previously unrecognized modulator of the SNO-GAPDH cascade, providing novel insight into RNS-mediated neuronal cell death. For future work, several unanswered questions remain. Why does SNO-GOSPEL appear earlier than SNO-GAPDH? The authors could not show transfer of the NO group from GAPDH to GOSPEL, arguing against transnitrosylation as the reason for the early appearance of SNO-GOSPEL after NMDA exposure. A possible reason for SNO-GOSPEL levels increasing before SNO-GAPDH might have to do with the rapidity and stability of the covalent redox reaction producing nitrosylation. For example, SNO may form a very stable modification on GOSPEL, thereby avoiding the fact that NO is often a good "leaving group." In that case, NO might react with the target cysteine (C47) on GOSPEL even though the cytosolic concentration of NO is very low. This can occur if the S-nitrosylated cysteine shares pi electrons with a neighboring tyrosine residue to chemically stabilize the SNO group (Stamler et al., 1997Stamler J.S. Jia L. Eu J.P. McMahon T.J. Demchenko I.T. Bonaventura J. Gernert K. Piantadosi C.A. Science. 1997; 276: 2034-2037Crossref PubMed Scopus (913) Google Scholar). Although there is no tyrosine residue located near C47 in the primary amino acid sequence of GOSPEL, its three-dimensional structure by crystallography or NMR is not yet known. S-Nitrosylation of GOSPEL might also result in a conformational change that not only enhances its binding to GAPDH but also reduces the accessibility of SNO to cytosolic reductants, such as glutathione or denitrosylating enzymes, as recently suggested by Jaffrey and colleagues (Paige et al., 2008Paige J.S. Xu G. Stancevic B. Jaffrey S.R. Chem. Biol. 2008; 15: 1307-1316Abstract Full Text Full Text PDF PubMed Scopus (142) Google Scholar). What are the implications of the new work for neurodegenerative disorders? Pesticides and other environmental toxins that inhibit mitochondrial complex I are thought to result in oxidative/nitrosative stress and consequent aberrant protein accumulation and cell death (Beal, 2001Beal M.F. Nat. Rev. Neurosci. 2001; 2: 325-334Crossref PubMed Scopus (487) Google Scholar, Nakamura and Lipton, 2007Nakamura T. Lipton S.A. Cell Death Differ. 2007; 14: 1305-1314Crossref PubMed Scopus (44) Google Scholar). In animal models, administration of complex I inhibitors, such as MPTP, 6-hydroxydopamine, rotenone, or paraquat, which results in overproduction of ROS/RNS, reproduces many of the features seen in sporadic PD, including dopaminergic neuronal degeneration, upregulation and aggregation of α-synuclein, Lewy body-like intraneuronal inclusions, and behavioral impairments (Beal, 2001Beal M.F. Nat. Rev. Neurosci. 2001; 2: 325-334Crossref PubMed Scopus (487) Google Scholar). Along these lines, Sen et al., 2009Sen N. Hara M.R. Ahmad A.S. Cascio M.B. Kamiya A. Ehmsen J.T. Aggrawal N. Hester L. Doré S. Snyder S.H. Sawa A. Neuron. 2009; 63 (this issue): 81-91Abstract Full Text Full Text PDF PubMed Scopus (97) Google Scholar demonstrate the presence of SNO-GOSPEL and SNO-GAPDH in MPTP-treated mice, with SNO-GOSPEL appearing first, thus mimicking the in vitro results described above. Additionally, the authors showed that overexpressed GOSPEL reduced NMDA-mediated brain injury. These findings suggest that redox regulation of these proteins may have pathophysiological relevance. A future direction will be to determine whether neuron-specific depletion of GOSPEL by gene targeting can promote neuronal cell death in vivo under neurodegenerative conditions associated with generation of ROS/RNS. This type of experiment will be particularly important to strengthen the notion that GOSPEL has neuroprotective activity in intact animals. Excessive nitrosative and oxidative stress, possibly triggered by overactivation of NMDA receptors and mitochondrial dysfunction, may affect multiple intracellular signaling pathways that could conceivably contribute to neuronal cell injury and death in "sporadic" cases of neurodegenerative diseases. The elucidation by Snyder and colleagues of a pathway that leads to dysregulation of GOSPEL/GAPDH binding by S-nitrosylation provides a mechanistic link between free radical production and neuronal cell injury in neurodegenerative disorders such as PD and HD. Exploitation of the redox pathways that influence these reactions may lead to the development of new therapeutic approaches to neurodegenerative conditions by controlling S-nitrosylation of specific proteins. GOSPEL: A Neuroprotective Protein that Binds to GAPDH upon S-NitrosylationSen et al.NeuronJuly 16, 2009In BriefWe recently reported a cell death cascade whereby cellular stressors activate nitric oxide formation leading to S-nitrosylation of GAPDH that binds to Siah and translocates to the nucleus. The nuclear GAPDH/Siah complex augments p300/CBP-associated acetylation of nuclear proteins, including p53, which mediate cell death. We report a 52 kDa cytosolic protein, GOSPEL, which physiologically binds GAPDH, in competition with Siah, retaining GAPDH in the cytosol and preventing its nuclear translocation. Full-Text PDF Open Archive
Referência(s)