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Ding L, Xu X, Li C, Wang Y, Xia X, Zheng JC. Glutaminase in microglia: A novel regulator of neuroinflammation. Brain Behav Immun 2021; 92:139-156. [PMID: 33278560 DOI: 10.1016/j.bbi.2020.11.038] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Revised: 10/11/2020] [Accepted: 11/28/2020] [Indexed: 12/15/2022] Open
Abstract
Neuroinflammation is the inflammatory responses that are involved in the pathogenesis of most neurological disorders. Glutaminase (GLS) is the enzyme that catalyzes the hydrolysis of glutamine to produce glutamate. Besides its well-known role in cellular metabolism and excitatory neurotransmission, GLS has recently been increasingly noticed to be up-regulated in activated microglia under pathological conditions. Furthermore, GLS overexpression induces microglial activation, extracellular vesicle secretion, and neuroinflammatory microenvironment formation, which, are compromised by GLS inhibitors in vitro and in vivo. These results indicate that GLS has more complicated implications in brain disease etiology than what are previously known. In this review, we introduce GLS isoforms, expression patterns in the body and the brain, and expression/activities regulation. Next, we discuss the metabolic and neurotransmission functions of GLS. Afterwards, we summarize recent findings of GLS-mediated microglial activation and pro-inflammatory extracellular vesicle secretion, which, in turns, induces neuroinflammation. Lastly, we provide a comprehensive discussion for the involvement of microglial GLS in the pathogenesis of various neurological disorders, indicating microglial GLS as a promising target to treat these diseases.
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Affiliation(s)
- Lu Ding
- Center for Translational Neurodegeneration and Regenerative Therapy, Shanghai Tenth People's Hospital Affiliated to Tongji University School of Medicine, Shanghai 200072, China
| | - Xiaonan Xu
- Center for Translational Neurodegeneration and Regenerative Therapy, Shanghai Tenth People's Hospital Affiliated to Tongji University School of Medicine, Shanghai 200072, China
| | - Congcong Li
- Center for Translational Neurodegeneration and Regenerative Therapy, Shanghai Tenth People's Hospital Affiliated to Tongji University School of Medicine, Shanghai 200072, China
| | - Yi Wang
- Center for Translational Neurodegeneration and Regenerative Therapy, Shanghai Tenth People's Hospital Affiliated to Tongji University School of Medicine, Shanghai 200072, China; Collaborative Innovation Center for Brain Science, Tongji University, Shanghai 200092, China; Translational Research Institute of Brain and Brain-Like Intelligence, Shanghai Fourth People's Hospital affiliated to Tongji University School of Medicine, Shanghai 200434, China.
| | - Xiaohuan Xia
- Center for Translational Neurodegeneration and Regenerative Therapy, Shanghai Tenth People's Hospital Affiliated to Tongji University School of Medicine, Shanghai 200072, China; Collaborative Innovation Center for Brain Science, Tongji University, Shanghai 200092, China; Translational Research Institute of Brain and Brain-Like Intelligence, Shanghai Fourth People's Hospital affiliated to Tongji University School of Medicine, Shanghai 200434, China.
| | - Jialin C Zheng
- Center for Translational Neurodegeneration and Regenerative Therapy, Shanghai Tenth People's Hospital Affiliated to Tongji University School of Medicine, Shanghai 200072, China; Collaborative Innovation Center for Brain Science, Tongji University, Shanghai 200092, China; Translational Research Institute of Brain and Brain-Like Intelligence, Shanghai Fourth People's Hospital affiliated to Tongji University School of Medicine, Shanghai 200434, China; Departments of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198-5930, USA.
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Nuclear Translocation of Glutaminase GLS2 in Human Cancer Cells Associates with Proliferation Arrest and Differentiation. Sci Rep 2020; 10:2259. [PMID: 32042057 PMCID: PMC7010782 DOI: 10.1038/s41598-020-58264-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Accepted: 01/08/2020] [Indexed: 11/08/2022] Open
Abstract
Glutaminase (GA) catalyzes the first step in mitochondrial glutaminolysis playing a key role in cancer metabolic reprogramming. Humans express two types of GA isoforms: GLS and GLS2. GLS isozymes have been consistently related to cell proliferation, but the role of GLS2 in cancer remains poorly understood. GLS2 is repressed in many tumor cells and a better understanding of its function in tumorigenesis may further the development of new therapeutic approaches. We analyzed GLS2 expression in HCC, GBM and neuroblastoma cells, as well as in monkey COS-7 cells. We studied GLS2 expression after induction of differentiation with phorbol ester (PMA) and transduction with the full-length cDNA of GLS2. In parallel, we investigated cell cycle progression and levels of p53, p21 and c-Myc proteins. Using the baculovirus system, human GLS2 protein was overexpressed, purified and analyzed for posttranslational modifications employing a proteomics LC-MS/MS platform. We have demonstrated a dual targeting of GLS2 in human cancer cells. Immunocytochemistry and subcellular fractionation gave consistent results demonstrating nuclear and mitochondrial locations, with the latter being predominant. Nuclear targeting was confirmed in cancer cells overexpressing c-Myc- and GFP-tagged GLS2 proteins. We assessed the subnuclear location finding a widespread distribution of GLS2 in the nucleoplasm without clear overlapping with specific nuclear substructures. GLS2 expression and nuclear accrual notably increased by treatment of SH-SY5Y cells with PMA and it correlated with cell cycle arrest at G2/M, upregulation of tumor suppressor p53 and p21 protein. A similar response was obtained by overexpression of GLS2 in T98G glioma cells, including downregulation of oncogene c-Myc. Furthermore, human GLS2 was identified as being hypusinated by MS analysis, a posttranslational modification which may be relevant for its nuclear targeting and/or function. Our studies provide evidence for a tumor suppressor role of GLS2 in certain types of cancer. The data imply that GLS2 can be regarded as a highly mobile and multilocalizing protein translocated to both mitochondria and nuclei. Upregulation of GLS2 in cancer cells induced an antiproliferative response with cell cycle arrest at the G2/M phase.
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Banerjee A, Ray S. Novel insight into mutational impacts and binding mechanism of human glutaminase and glutaminase-interacting protein: A bio-molecular modeling and docking analysis. GENE REPORTS 2017. [DOI: 10.1016/j.genrep.2017.04.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Abstract
Mammalian glutaminases catalyze the stoichiometric conversion of L-glutamine to L-glutamate and ammonium ions. In brain, glutaminase is considered the prevailing pathway for synthesis of the neurotransmitter pool of glutamate. Besides neurotransmission, the products of glutaminase reaction also fulfill crucial roles in energy and metabolic homeostasis in mammalian brain. In the last years, new functional roles for brain glutaminases are being uncovered by using functional genomic and proteomic approaches. Glutaminases may act as multifunctional proteins able to perform different tasks: the discovery of multiple transcript variants in neurons and glial cells, novel extramitochondrial localizations, and isoform-specific proteininteracting partners strongly support possible moonlighting functions for these proteins. In this chapter, we present a critical account of essential works on brain glutaminase 80 years after its discovery. We will highlight the impact of recent findings and thoughts in the context of the glutamate/glutamine brain homeostasis.
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Oliver AW, He X, Borthwick K, Donne AJ, Hampson L, Hampson IN. The HPV16 E6 binding protein Tip-1 interacts with ARHGEF16, which activates Cdc42. Br J Cancer 2010; 104:324-31. [PMID: 21139582 PMCID: PMC3031889 DOI: 10.1038/sj.bjc.6606026] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Background: Guanidine exchange factor (GEF)-catalysed activation of Rho proteins such as Cdc42 has been shown to have a crucial role in cellular transformation, malignant progression and invasion. We have previously shown that the HPV16 E6 oncoprotein binds to the PDZ domain protein Tax-interacting-protein 1 (Tip-1) and we now report identification and functional analysis of a novel Tip-1 binding GEF. Methods: Yeast two-hybrid, in vitro pull-down, site-directed mutagenesis, semiquantitative PCR, co-immunoprecipitation and western blotting were used to identify/confirm novel Tip-1 binding partners and analyse cellular expression levels. In vitro kinetic analyses of recombinant proteins, siRNA gene silencing and in cell assays were used to measure Rho protein activation. Results: Tax-interacting-protein 1 was shown to interact with ARHGEF16 by its carboxyl PDZ binding motif. Levels of ARHGEF16 were increased in transformed and immortalised cells expressing ectopic HPV16 E6 and Cdc42 was co-immunoprecipitated by ARHGEF16 in the presence of high-risk HPV E6. In vitro kinetic analysis confirmed that recombinant ARHGEF16 activates Cdc42 and this was increased by the addition of recombinant Tip-1 and E6. Cells expressing HPV16 E6 had higher levels of Cdc42 activation, which was decreased by siRNA silencing of either Tip-1 or ARHGEF16. Conclusion: These data suggest that HPV16 E6, Tip-1 and ARHGEF16 may cooperate to activate Cdc42 and support a potential link between the expression of HPV16 E6 and Cdc42 activation.
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Affiliation(s)
- A W Oliver
- University of Manchester Gynaecological Oncology Laboratories, School of Cancer and Enabling Sciences, St Mary's Hospital, Oxford Road, Manchester M13 9WL, UK
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Abstract
AbstractGlutaminase is considered as the main glutamate producer enzyme in brain. Consequently, the enzyme is essential for both glutamatergic and gabaergic transmissions. Glutamine-derived glutamate and ammonia, the products of glutaminase reaction, fulfill crucial roles in energy metabolism and in the biosynthesis of basic metabolites, such as GABA, proteins and glutathione. However, glutamate and ammonia are also hazardous compounds and danger lurks in their generation beyond normal physiological thresholds; hence, glutaminase activity must be carefully regulated in the mammalian brain. The differential distribution and regulation of glutaminase are key factors to modulate the metabolism of glutamate and glutamine in brain. The discovery of novel isoenzymes, protein interacting partners and subcellular localizations indicate new functions for brain glutaminase. In this short review, we summarize recent findings that point consistently towards glutaminase as a multifaceted protein able to perform different tasks. Finally, we will highlight the involvement of glutaminase in pathological states and its consideration as a potential therapeutic target.
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New insights into brain glutaminases: beyond their role on glutamatergic transmission. Neurochem Int 2009; 55:64-70. [PMID: 19428808 DOI: 10.1016/j.neuint.2009.02.022] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2008] [Revised: 02/18/2009] [Accepted: 02/27/2009] [Indexed: 01/29/2023]
Abstract
The synthesis of glutamate in brain must be exquisitely regulated because of its harmful potential giving rise to excitotoxic damage. In this sense, a stringent control based on multiple regulatory mechanisms should be expected to be exhibited by the biosynthetic enzymes responsible of glutamate generation, to assure that glutamate is only synthesized at the right place and at the right time. Glutaminase is considered as the main glutamate-producer enzyme in brain. Recently, novel glutaminase isoforms and extramitochondrial locations for these proteins have been discovered in the brain of mammals: identifying the function of each isozyme is essential for understanding the role of glutaminases in cerebral function. In addition, the interactome of glutaminases is starting to be uncovered adding a new level of regulatory complexity with important functional consequences, including selective and regulated targeting to concrete cellular locations. Finally, recent progress has identified glutaminase to be also present in astrocytes which precludes its classical consideration as a neuron-specific enzyme.
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Olalla L, Gutiérrez A, Jiménez AJ, López-Téllez JF, Khan ZU, Pérez J, Alonso FJ, de la Rosa V, Campos-Sandoval JA, Segura JA, Aledo JC, Márquez J. Expression of the scaffolding PDZ protein glutaminase-interacting protein in mammalian brain. J Neurosci Res 2008; 86:281-92. [PMID: 17847083 DOI: 10.1002/jnr.21505] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
A human brain cDNA clone coding for a novel PDZ-domain protein of 124 amino acids was previously isolated in our laboratory. The protein was termed glutaminase-interacting protein (GIP), because it interacts with the C-terminal region of the human L-type glutaminase (LGA). The pattern of expression and functions of GIP in brain are completely unknown, so its significance remains undefined. Here we describe the expression of GIP mRNA and protein in mammalian brain. Northern blot analysis revealed that GIP mRNA was ubiquitous in most regions of human brain but was particularly abundant in spinal cord. The presence of the protein in rat and monkey brain was studied at the regional, cellular, and subcellular level by immunocytochemistry. The protein was found to be present in both neurons and astrocytes, with a cytosolic and mitochondrial subcellular localization. Double immunofluorescence labeling with anti-GIP and anti-LGA antibodies using confocal microscopy revealed colocalization of both proteins in astrocyte cell processes and their perivascular end feet. Electron microscopy of rat brain neurons revealed GIP immunoreactivity concentrated also in the nuclear envelope and the plasma membrane. The multiple locations for GIP in mammalian brain are in agreement with known protein interaction partners reported for this PDZ protein. The findings presented here support a role of GIP as an important scaffold in both astrocytes and neurons and point toward astrocytic processes and perivascular end feet as plausible anatomical substrates for interaction with glutaminase.
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Affiliation(s)
- Lucía Olalla
- Departamento de Biología Molecular y Bioquímica, Universidad de Málaga, Málaga, Spain
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Campos-Sandoval JA, López de la Oliva AR, Lobo C, Segura JA, Matés JM, Alonso FJ, Márquez J. Expression of functional human glutaminase in baculovirus system: Affinity purification, kinetic and molecular characterization. Int J Biochem Cell Biol 2007; 39:765-73. [PMID: 17267261 DOI: 10.1016/j.biocel.2006.12.002] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2006] [Revised: 12/05/2006] [Accepted: 12/06/2006] [Indexed: 11/29/2022]
Abstract
Glutaminase catalyzes the hydrolysis of glutamine yielding stoichiometric amounts of glutamate plus ammonium ions. In mammals, there are two different genes encoding for glutaminase, known as liver (L) and kidney (K) types. The human L-type isoform expressed in baculovirus yielded functional recombinant enzyme in Sf9 insect cells. A novel affinity chromatography method, based on its specific interaction with a PDZ protein, was developed for purification. Kinetic constants were determined for the purified human isozyme, which showed an allosteric behaviour for glutamine, with a Hill index of 2.7 and S(0.5) values of 32 and 64 mM for high and low P(i) concentrations, respectively. Whereas the protein showed a low P(i) dependence typical for L-type glutaminases, the enzyme was unexpectedly inhibited by glutamate, a kinetic characteristic exclusive of K-type isozymes, and was slightly activated by ammonia, unlike the classical liver enzymes which show an absolute dependence on ammonia. Subcellular fractionation demonstrates that recombinant human glutaminase was targeted to both mitochondria and nucleus, and in both locations the protein was catalytically active. This is the first report of the expression of a functional L-type mammalian glutaminase enzyme. The study also provides a simple and efficient method for affinity purification of the recombinant enzyme. Moreover, the data imply that this human enzyme may represent a new isoform different from classical kidney and liver isozymes.
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Affiliation(s)
- José A Campos-Sandoval
- Departamento de Biología Molecular y Bioquímica, Laboratorio de Química de Proteínas, Facultad de Ciencias, Universidad de Málaga, 29071 Málaga, Spain
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Erdmann NB, Whitney NP, Zheng J. Potentiation of Excitotoxicity in HIV-1 Associated Dementia and the Significance of Glutaminase. ACTA ACUST UNITED AC 2006; 6:315-328. [PMID: 18059978 DOI: 10.1016/j.cnr.2006.09.009] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
HIV-1 Associated Dementia (HAD) is a significant consequence of HIV infection. Although multiple inflammatory factors contribute to this chronic, progressive dementia, excitotoxic damage appears to be an underlying mechanism in the neurodegenerative process. Excitotoxicity is a cumulative effect of multiple processes occurring in the CNS during HAD. The overstimulation of glutamate receptors, an increased vulnerability of neurons, and disrupted astrocyte support each potentiate excitotoxic damage to neurons. Recent evidence suggests that poorly controlled generation of glutamate by phosphate-activated glutaminase may contribute to the neurotoxic state typical of HAD as well as other neurodegenerative disorders. Glutaminase converts glutamine, a widely available substrate throughout the CNS to glutamate. Inflammatory conditions may precipitate unregulated activity of glutaminase, a potentially important mechanism in HAD pathogenesis.
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Affiliation(s)
- Nathan B Erdmann
- The laboratory of Neurotoxicology, University of Nebraska Medical Center, Omaha, Nebraska 68198-5880
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Olalla L, Gutiérrez A, Campos JA, Khan ZU, Alonso FJ, Segura JA, Márquez J, Aledo JC. Nuclear localization of L-type glutaminase in mammalian brain. J Biol Chem 2002; 277:38939-44. [PMID: 12163477 DOI: 10.1074/jbc.c200373200] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In mammals, there are two different genes encoding for glutaminase isoforms, named liver (LGA) and kidney (KGA) types. LGA has long been believed to be present only in liver mitochondria from adult animals. However, we have recently reported the presence of LGA mRNA in human brain. We now describe the expression of LGA mRNA in the brain of other mammals (cow, mouse, rabbit, and rat) and in different areas of human brain as assessed by Northern blot analysis. The presence of mRNA encoding for this isoform in rat brain was further confirmed by reverse transcriptase-PCR cloning and sequencing. Although it has been well accepted that glutaminase is a mitochondrial enzyme, using newly generated isoform-specific antibodies, we have found a differential intracellular immunolocalization of both glutaminase isoforms in rat and monkey brain. In both species, KGA protein was present in mitochondria, whereas LGA protein was localized in nuclei. Furthermore, subcellular fractionation and Western blot analysis revealed that brain LGA was enriched in nuclei where it was catalytically active. Nuclear glutaminase exhibited a kinetic behavior that resembles that of the liver-type enzyme with regard to the low phosphate concentration requirement; however, nuclear glutaminase was susceptible to glutamate inhibition, a property that is absent in the rat liver enzyme.
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Affiliation(s)
- Lucía Olalla
- Departamento de Biologia Molecular y Bioquimica, Laboratorio de Quimica de Proteinas, Universidad de Málaga, 29071-Málaga, Spain
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Porter LD, Ibrahim H, Taylor L, Curthoys NP. Complexity and species variation of the kidney-type glutaminase gene. Physiol Genomics 2002; 9:157-66. [PMID: 12045296 DOI: 10.1152/physiolgenomics.00017.2002] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Increased expression of rat kidney-type glutaminase (KGA) during metabolic acidosis results from selective mRNA stabilization. This process is mediated by an 8-base AU-sequence that functions as a pH-response element (pHRE). LLC-PK1-FBPase+ cells, a pH-responsive porcine kidney cell line, express four distinct GA mRNAs. RNase H mapping indicated that three of the GA mRNAs are generated by use of alternative polyadenylation sites and are homologs of the rat KGA mRNA, while the fourth contains a different COOH-terminal coding and 3'-untranslated sequence. PCR cloning and sequencing established that the latter GA mRNA is the homolog of the human GAC mRNA. A rat GAC cDNA was also cloned from a rat kidney library. The 3'-untranslated regions of the GAC mRNAs, but not the porcine or human KGA mRNAs, contain identifiable pHREs. The human KGA gene spans 82 kb and is composed of 19 exons. The unique sequence from the hGAC cDNA is contained in a single exon. Thus in humans, alternative splicing of the initial transcript could produce two GA mRNAs, only one of which may be increased during acidosis.
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Affiliation(s)
- L David Porter
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523-1870, USA
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