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Kosuge A, Kunisawa K, Iida T, Wulaer B, Kawai T, Tanabe M, Saito K, Nabeshima T, Mouri A. Chronic social defeat stress induces the down-regulation of the Nedd4L-GLT-1 ubiquitination pathway in the prefrontal cortex of mice. J Neurochem 2024. [PMID: 38497582 DOI: 10.1111/jnc.16100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Revised: 02/25/2024] [Accepted: 02/29/2024] [Indexed: 03/19/2024]
Abstract
Stressful life events contribute to the onset of major depressive disorder (MDD). We recently demonstrated abnormalities in ubiquitination in the pathophysiology of MDD. However, the underlying molecular mechanisms remain unclear. We investigated the involvement of the ubiquitination system-mediated glutamatergic dysfunction in social impairment induced by chronic social defeat stress (CSDS). Adult C57BL/6J mice were exposed to aggressor ICR male mice for 10 consecutive days. Social impairment was induced by CSDS in the social interaction test 1 days after the last stress exposure. In terms of brain microdialysis, CSDS reduced depolarization-evoked glutamate release in the prefrontal cortex (PFC), which was reversed by a glutamate transporter 1 (GLT-1) inhibitor. Interestingly, the expression of ubiquitinated, but not total GLT-1, was decreased in the PFC of mice exposed to CSDS. The expression of neural precursor cells expressing developmentally downregulated gene 4-like (Nedd4L: E3 ligase for GLT-1), and ubiquitin-conjugating enzyme E2D2 (Ube2d2: E2 ubiquitin-conjugating enzyme for Nedd4L) was also reduced in CSDS mice. Furthermore, the downregulation of the Nedd4L-GLT-1 ubiquitination pathway decreased SIT ratio, but up-regulation increased it even in non-CSDS mice. Taken together, the decrease in GLT-1 ubiquitination may reduce the release of extracellular glutamate induced by high-potassium stimulation, which may lead to social impairment, while we could not find differences in GLT-1 ubiquitination between susceptible and resistant CSDS mice. In conclusion, GLT-1 ubiquitination could play a crucial role in the pathophysiology of MDD and is an attractive target for the development of novel antidepressants.
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Affiliation(s)
- Aika Kosuge
- Department of Regulatory Science for Evaluation & Development of Pharmaceuticals & Devices, Fujita Health University Graduate School of Health Sciences, Toyoake, Aichi, Japan
| | - Kazuo Kunisawa
- Department of Regulatory Science for Evaluation & Development of Pharmaceuticals & Devices, Fujita Health University Graduate School of Health Sciences, Toyoake, Aichi, Japan
| | - Tsubasa Iida
- Department of Regulatory Science for Evaluation & Development of Pharmaceuticals & Devices, Fujita Health University Graduate School of Health Sciences, Toyoake, Aichi, Japan
| | - Bolati Wulaer
- Advanced Diagnostic System Research Laboratory, Fujita Health University Graduate School of Health Science, Toyoake, Aichi, Japan
- Department of Advanced Diagnostic System Development, Fujita Health University Graduate School of Health Sciences, Toyoake, Aichi, Japan
| | - Tomoki Kawai
- Department of Regulatory Science for Evaluation & Development of Pharmaceuticals & Devices, Fujita Health University Graduate School of Health Sciences, Toyoake, Aichi, Japan
| | - Moeka Tanabe
- Department of Regulatory Science for Evaluation & Development of Pharmaceuticals & Devices, Fujita Health University Graduate School of Health Sciences, Toyoake, Aichi, Japan
| | - Kuniaki Saito
- Advanced Diagnostic System Research Laboratory, Fujita Health University Graduate School of Health Science, Toyoake, Aichi, Japan
- Department of Advanced Diagnostic System Development, Fujita Health University Graduate School of Health Sciences, Toyoake, Aichi, Japan
- Laboratory of Health and Medical Science Innovation, Fujita Health University Graduate School of Health Science, Toyoake, Aichi, Japan
- Japanese Drug Organization of Appropriate Use and Research, Toyoake, Aichi, Japan
| | - Toshitaka Nabeshima
- Advanced Diagnostic System Research Laboratory, Fujita Health University Graduate School of Health Science, Toyoake, Aichi, Japan
- Laboratory of Health and Medical Science Innovation, Fujita Health University Graduate School of Health Science, Toyoake, Aichi, Japan
- Japanese Drug Organization of Appropriate Use and Research, Toyoake, Aichi, Japan
| | - Akihiro Mouri
- Department of Regulatory Science for Evaluation & Development of Pharmaceuticals & Devices, Fujita Health University Graduate School of Health Sciences, Toyoake, Aichi, Japan
- Japanese Drug Organization of Appropriate Use and Research, Toyoake, Aichi, Japan
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2
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Vollbrecht PJ, Nesbitt KM, Addis VM, Boulnemour KM, Micheli DA, Smith KB, Sandoval DA, Kennedy RT, Ferrario CR. Differential regulation of nucleus accumbens glutamate and GABA in obesity-prone and obesity-resistant rats. J Neurochem 2023; 164:499-511. [PMID: 36336816 PMCID: PMC10604761 DOI: 10.1111/jnc.15720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Revised: 09/23/2022] [Accepted: 10/20/2022] [Indexed: 11/09/2022]
Abstract
Obesity is one of the leading health concerns in the United States. Studies from human and rodent models suggest that inherent differences in the function of brain motivation centers, including the nucleus accumbens (NAc), contribute to overeating and thus obesity. For example, there are basal enhancements in the excitability of NAc GABAergic medium spiny neurons (MSN) and reductions in basal expression of AMPA-type glutamate receptors in obesity-prone vs obesity-resistant rats. However, very little is known about the regulation of extracellular glutamate and GABA within the NAc of these models. Here we gave obesity-prone and obesity-resistant rats stable isotope-labeled glucose (13 C6 -glucose) and used liquid chromatography mass spectrometry (LC-MS) analysis of NAc dialysate to examine the real-time incorporation of 13 C6 -glucose into glutamate, glutamine, and GABA. This novel approach allowed us to identify differences in glucose utilization for neurotransmitter production between these selectively bred lines. We found that voluntarily ingested or gastrically infused 13 C6 -glucose rapidly enters the NAc and is incorporated into 13 C2 -glutamine, 13 C2 -glutamate, and 13 C2 -GABA in both groups within minutes. However, the magnitude of increases in NAc 13 C2 -glutamine and 13 C2 -GABA were lower in obesity-prone than in obesity-resistant rats, while basal levels of glutamate were elevated. This suggested that there may be differences in the astrocytic regulation of these analytes. Thus, we next examined NAc glutamine synthetase, GAD67, and GLT-1 protein expression. Consistent with reduced 13 C2 -glutamine and 13 C2 -GABA, NAc glutamine synthetase and GLT-1 protein expression were reduced in obesity-prone vs obesity-resistant groups. Taken together, these data show that NAc glucose utilization differs dramatically between obesity-prone and obesity-resistant rats, favoring glutamate over GABA production in obesity-prone rats and that reductions in NAc astrocytic recycling of glutamate contribute to these differences. These data are discussed in light of established differences in NAc function between these models and the role of the NAc in feeding behavior.
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Affiliation(s)
- Peter J. Vollbrecht
- Department of Biomedical Sciences, Western Michigan University Homer Stryker M.D. School of Medicine, Kalamazoo, MI
| | - Kathryn M. Nesbitt
- Department of Chemistry, Department of Pharmacology, University of Michigan, Ann Arbor, MI
| | - Victoria M. Addis
- Department of Biomedical Sciences, Western Michigan University Homer Stryker M.D. School of Medicine, Kalamazoo, MI
| | - Keenan M. Boulnemour
- Department of Biomedical Sciences, Western Michigan University Homer Stryker M.D. School of Medicine, Kalamazoo, MI
| | - Daniel A. Micheli
- Department of Biomedical Sciences, Western Michigan University Homer Stryker M.D. School of Medicine, Kalamazoo, MI
| | - Kendall B. Smith
- Department of Biomedical Sciences, Western Michigan University Homer Stryker M.D. School of Medicine, Kalamazoo, MI
| | - Darleen A. Sandoval
- Department of Pediatrics, University of Colorado, School of Medicine, Anshutz Medical Campus, Aurora, CO
| | - Robert T. Kennedy
- Department of Chemistry, Department of Pharmacology, University of Michigan, Ann Arbor, MI
| | - Carrie R. Ferrario
- Department of Pharmacology, Psychology Department (Biopsychology) University of Michigan, Ann Arbor, MI
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Wang C, Zhao F, Liu J, Liu H. The ubiquitin ligase Nedd4-2 mediates the regulation of PepT2 by mTORC1 in bovine mammary epithelial cells. ANIMAL NUTRITION 2022; 10:12-18. [PMID: 35601254 PMCID: PMC9111928 DOI: 10.1016/j.aninu.2021.11.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Revised: 11/21/2021] [Accepted: 11/23/2021] [Indexed: 11/16/2022]
Abstract
Peptide transporter 2 (PepT2) transports short peptides from the blood into bovine mammary epithelial cells (BMEC) to stimulate milk protein synthesis. Despite the fact that the effect of PepT2 is acknowledged in BMEC, little is known about its regulation. This study was completed to investigate the role of mammalian target of the rapamycin (mTOR) signaling in regulating the expression and function of PepT2 in BMEC. The regulation of PepT2 by mTOR in BMEC was studied in vitro using peptide transport assay, gene silencing, Western blot. The membrane expression of PepT2 and the uptake of β-Ala-Lys-N-7-amino-4-methylcoumarin-3-acetic acid (β-Ala-Lys-AMCA), a model dipeptide, in BMEC were reduced by rapamycin (a mTOR inhibitor) and silencing of either mTOR complex 1 (mTORC1) or mTOR complex 2 (mTORC2), stimulated by DEP domain-containing mTOR-interacting protein (DEPTOR, endogenous inhibitor of mTORC1 and mTORC2) silencing. The trafficking of PepT2 to the membrane and the uptake of β-Ala-Lys-AMCA was promoted by neuronal precursor cell-expressed developmentally down-regulated 4 isoform 2 (Nedd4-2) silencing. The effects of knockdown of mTORC1, but not mTORC2, on cell membrane expression and transport activity of PepT2 was abolished by Nedd4-2 silencing. With immunofluorescence staining, PepT2 was identified to be interacting with Nedd4-2. The Nedd4-2 expression and the interaction between PepT2 and Nedd4-2 was increased through mTORC1 knockdown, indicating an increased ubiquitination of PepT2. The results revealed that mTORC1 can regulate the expression and function of PepT2 through Nedd4-2 in BMEC.
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Iovino L, Giusti V, Pischedda F, Giusto E, Plotegher N, Marte A, Battisti I, Di Iacovo A, Marku A, Piccoli G, Bandopadhyay R, Perego C, Bonifacino T, Bonanno G, Roseti C, Bossi E, Arrigoni G, Bubacco L, Greggio E, Hilfiker S, Civiero L. Trafficking of the glutamate transporter is impaired in LRRK2-related Parkinson's disease. Acta Neuropathol 2022; 144:81-106. [PMID: 35596783 PMCID: PMC9217889 DOI: 10.1007/s00401-022-02437-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Revised: 05/11/2022] [Accepted: 05/11/2022] [Indexed: 12/02/2022]
Abstract
The Excitatory Amino Acid Transporter 2 (EAAT2) accounts for 80% of brain glutamate clearance and is mainly expressed in astrocytic perisynaptic processes. EAAT2 function is finely regulated by endocytic events, recycling to the plasma membrane and degradation. Noteworthy, deficits in EAAT2 have been associated with neuronal excitotoxicity and neurodegeneration. In this study, we show that EAAT2 trafficking is impaired by the leucine-rich repeat kinase 2 (LRRK2) pathogenic variant G2019S, a common cause of late-onset familial Parkinson’s disease (PD). In LRRK2 G2019S human brains and experimental animal models, EAAT2 protein levels are significantly decreased, which is associated with elevated gliosis. The decreased expression of the transporter correlates with its reduced functionality in mouse LRRK2 G2019S purified astrocytic terminals and in Xenopus laevis oocytes expressing human LRRK2 G2019S. In LRRK2 G2019S knock-in mouse brain, the correct surface localization of the endogenous transporter is impaired, resulting in its interaction with a plethora of endo-vesicular proteins. Mechanistically, we report that pathogenic LRRK2 kinase activity delays the recycling of the transporter to the plasma membrane via Rabs inactivation, causing its intracellular re-localization and degradation. Taken together, our results demonstrate that pathogenic LRRK2 interferes with the physiology of EAAT2, pointing to extracellular glutamate overload as a possible contributor to neurodegeneration in PD.
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Haouari S, Vourc’h P, Jeanne M, Marouillat S, Veyrat-Durebex C, Lanznaster D, Laumonnier F, Corcia P, Blasco H, Andres CR. The Roles of NEDD4 Subfamily of HECT E3 Ubiquitin Ligases in Neurodevelopment and Neurodegeneration. Int J Mol Sci 2022; 23:ijms23073882. [PMID: 35409239 PMCID: PMC8999422 DOI: 10.3390/ijms23073882] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Revised: 03/28/2022] [Accepted: 03/29/2022] [Indexed: 02/06/2023] Open
Abstract
The ubiquitin pathway regulates the function of many proteins and controls cellular protein homeostasis. In recent years, it has attracted great interest in neurodevelopmental and neurodegenerative diseases. Here, we have presented the first review on the roles of the 9 proteins of the HECT E3 ligase NEDD4 subfamily in the development and function of neurons in the central nervous system (CNS). We discussed their regulation and their direct or indirect involvement in neurodevelopmental diseases, such as intellectual disability, and neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease or Amyotrophic Lateral Sclerosis. Further studies on the roles of these proteins, their regulation and their targets in neurons will certainly contribute to a better understanding of neuronal function and dysfunction, and will also provide interesting information for the development of therapeutics targeting them.
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Affiliation(s)
- Shanez Haouari
- UMR 1253, iBrain, Université de Tours, Inserm, 37044 Tours, France; (S.H.); (M.J.); (S.M.); (C.V.-D.); (D.L.); (F.L.); (P.C.); (H.B.); (C.R.A.)
| | - Patrick Vourc’h
- UMR 1253, iBrain, Université de Tours, Inserm, 37044 Tours, France; (S.H.); (M.J.); (S.M.); (C.V.-D.); (D.L.); (F.L.); (P.C.); (H.B.); (C.R.A.)
- CHRU de Tours, Service de Biochimie et Biologie Moléculaire, 37044 Tours, France
- Correspondence: ; Tel.: +33-(0)2-34-37-89-10; Fax: +33-(0)2-47-36-61-85
| | - Médéric Jeanne
- UMR 1253, iBrain, Université de Tours, Inserm, 37044 Tours, France; (S.H.); (M.J.); (S.M.); (C.V.-D.); (D.L.); (F.L.); (P.C.); (H.B.); (C.R.A.)
- CHRU de Tours, Service de Génétique, 37044 Tours, France
| | - Sylviane Marouillat
- UMR 1253, iBrain, Université de Tours, Inserm, 37044 Tours, France; (S.H.); (M.J.); (S.M.); (C.V.-D.); (D.L.); (F.L.); (P.C.); (H.B.); (C.R.A.)
| | - Charlotte Veyrat-Durebex
- UMR 1253, iBrain, Université de Tours, Inserm, 37044 Tours, France; (S.H.); (M.J.); (S.M.); (C.V.-D.); (D.L.); (F.L.); (P.C.); (H.B.); (C.R.A.)
- CHRU de Tours, Service de Biochimie et Biologie Moléculaire, 37044 Tours, France
| | - Débora Lanznaster
- UMR 1253, iBrain, Université de Tours, Inserm, 37044 Tours, France; (S.H.); (M.J.); (S.M.); (C.V.-D.); (D.L.); (F.L.); (P.C.); (H.B.); (C.R.A.)
| | - Frédéric Laumonnier
- UMR 1253, iBrain, Université de Tours, Inserm, 37044 Tours, France; (S.H.); (M.J.); (S.M.); (C.V.-D.); (D.L.); (F.L.); (P.C.); (H.B.); (C.R.A.)
| | - Philippe Corcia
- UMR 1253, iBrain, Université de Tours, Inserm, 37044 Tours, France; (S.H.); (M.J.); (S.M.); (C.V.-D.); (D.L.); (F.L.); (P.C.); (H.B.); (C.R.A.)
- CHRU de Tours, Service de Neurologie, 37044 Tours, France
| | - Hélène Blasco
- UMR 1253, iBrain, Université de Tours, Inserm, 37044 Tours, France; (S.H.); (M.J.); (S.M.); (C.V.-D.); (D.L.); (F.L.); (P.C.); (H.B.); (C.R.A.)
- CHRU de Tours, Service de Biochimie et Biologie Moléculaire, 37044 Tours, France
| | - Christian R. Andres
- UMR 1253, iBrain, Université de Tours, Inserm, 37044 Tours, France; (S.H.); (M.J.); (S.M.); (C.V.-D.); (D.L.); (F.L.); (P.C.); (H.B.); (C.R.A.)
- CHRU de Tours, Service de Biochimie et Biologie Moléculaire, 37044 Tours, France
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The Role of NEDD4 E3 Ubiquitin–Protein Ligases in Parkinson’s Disease. Genes (Basel) 2022; 13:genes13030513. [PMID: 35328067 PMCID: PMC8950476 DOI: 10.3390/genes13030513] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Accepted: 03/03/2022] [Indexed: 01/25/2023] Open
Abstract
Parkinson’s disease (PD) is a debilitating neurodegenerative disease that causes a great clinical burden. However, its exact molecular pathologies are not fully understood. Whilst there are a number of avenues for research into slowing, halting, or reversing PD, one central idea is to enhance the clearance of the proposed aetiological protein, oligomeric α-synuclein. Oligomeric α-synuclein is the main constituent protein in Lewy bodies and neurites and is considered neurotoxic. Multiple E3 ubiquitin-protein ligases, including the NEDD4 (neural precursor cell expressed developmentally downregulated protein 4) family, parkin, SIAH (mammalian homologues of Drosophila seven in absentia), CHIP (carboxy-terminus of Hsc70 interacting protein), and SCFFXBL5 SCF ubiquitin ligase assembled by the S-phase kinase-associated protein (SKP1), cullin-1 (Cul1), a zinc-binding RING finger protein, and the F-box domain/Leucine-rich repeat protein 5-containing protein FBXL5), have been shown to be able to ubiquitinate α-synuclein, influencing its subsequent degradation via the proteasome or lysosome. Here, we explore the link between NEDD4 ligases and PD, which is not only via α-synuclein but further strengthened by several additional substrates and interaction partners. Some members of the NEDD4 family of ligases are thought to crosstalk even with PD-related genes and proteins found to be mutated in familial forms of PD. Mutations in NEDD4 family genes have not been observed in PD patients, most likely because of their essential survival function during development. Following further in vivo studies, it has been thought that NEDD4 ligases may be viable therapeutic targets in PD. NEDD4 family members could clear toxic proteins, enhancing cell survival and slowing disease progression, or might diminish beneficial proteins, reducing cell survival and accelerating disease progression. Here, we review studies to date on the expression and function of NEDD4 ubiquitin ligases in the brain and their possible impact on PD pathology.
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Zeng X, Dong X, Xiao Q, Yao J. Vitamin C Inhibits Ubiquitination of Glutamate Transporter 1 (GLT-1) in Astrocytes by Downregulating HECTD1. ACS Chem Neurosci 2022; 13:676-687. [PMID: 35148069 DOI: 10.1021/acschemneuro.1c00845] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Excitatory neurotoxicity caused by the accumulation of glutamate in the synaptic cleft is an important cause of Parkinson's disease (PD). Astrocyte glutamate transporter 1 (GLT-1) is the main transporter responsible for transporting glutamate, and investigations toward the regulation of GLT-1 in astrocytes can reveal important insights. Vitamin C (VC) has important protective effects on the brain, but its effect on the regulation of GLT-1 expression is unclear. The purpose of this study was to explore any regulatory effect of VC on GLT-1 expression in astrocytes and to clarify the possible mechanism of such regulation. We found that GLT-1 expression was impaired in 1-methyl-4-phenylpyridinium iodide (MPP+)-treated astrocytes, and the transport capacity for glutamate was significantly reduced. Pretreatment with VC restored the GLT-1 expression in the MPP+-treated astrocytes. Intraperitoneal VC administration in a PD murine model confirmed that GLT-1 expression was restored in midbrain tissue. The VC-dependent rescue of GLT-1 expression in the MPP+-treated astrocytes was shown to be due to inhibition of GLT-1 ubiquitination. Transcriptome sequence analysis revealed a number of differentially expressed genes as a result of VC treatment on MPP+-treated astrocytes, including the downregulation of HECT Domain E3 ubiquitin protein ligase 1 (Hectd1). After knocking down Hectd1, the impaired GLT-1 expression caused by MPP+ was alleviated, while overexpression of Hectd1 significantly reduced the expression of GLT-1. After overexpression of Hectd1, VC could no longer increase GLT-1 expression of MPP+-treated astrocytes, indicating that HECTD1 is essential for VC regulation of GLT-1. Thus, VC reduces the ubiquitination of GLT-1 in astrocytes by inhibiting the expression of HECTD1. Our findings have identified a novel mechanism by which VC regulates the expression of GLT-1 in astrocytes.
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Affiliation(s)
- Xiaokang Zeng
- Central Laboratory, Shunde Hospital, Southern Medical University (The First People’s Hospital of Shunde Foshan), Foshan, 528300 Guangdong, China
| | - Xinhuai Dong
- Central Laboratory, Shunde Hospital, Southern Medical University (The First People’s Hospital of Shunde Foshan), Foshan, 528300 Guangdong, China
| | - Qiang Xiao
- Pulmonary and Critical Care Medicine, Shunde Hospital, Southern Medical University (The First People’s Hospital of Shunde Foshan), Foshan, 528300 Guangdong, China
| | - Jie Yao
- Central Laboratory, Shunde Hospital, Southern Medical University (The First People’s Hospital of Shunde Foshan), Foshan, 528300 Guangdong, China
- Department of Laboratory Medicine, Shunde Hospital, Southern Medical University (The First People’s Hospital of Shunde, Foshan), Foshan, 528300 Guangdong, China
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Rapid Regulation of Glutamate Transport: Where Do We Go from Here? Neurochem Res 2022; 47:61-84. [PMID: 33893911 PMCID: PMC8542062 DOI: 10.1007/s11064-021-03329-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Revised: 04/08/2021] [Accepted: 04/13/2021] [Indexed: 01/03/2023]
Abstract
Glutamate is the predominant excitatory neurotransmitter in the mammalian central nervous system (CNS). A family of five Na+-dependent transporters maintain low levels of extracellular glutamate and shape excitatory signaling. Shortly after the research group of the person being honored in this special issue (Dr. Baruch Kanner) cloned one of these transporters, his group and several others showed that their activity can be acutely (within minutes to hours) regulated. Since this time, several different signals and post-translational modifications have been implicated in the regulation of these transporters. In this review, we will provide a brief introduction to the distribution and function of this family of glutamate transporters. This will be followed by a discussion of the signals that rapidly control the activity and/or localization of these transporters, including protein kinase C, ubiquitination, glutamate transporter substrates, nitrosylation, and palmitoylation. We also include the results of our attempts to define the role of palmitoylation in the regulation of GLT-1 in crude synaptosomes. In some cases, the mechanisms have been fairly well-defined, but in others, the mechanisms are not understood. In several cases, contradictory phenomena have been observed by more than one group; we describe these studies with the goal of identifying the opportunities for advancing the field. Abnormal glutamatergic signaling has been implicated in a wide variety of psychiatric and neurologic disorders. Although recent studies have begun to link regulation of glutamate transporters to the pathogenesis of these disorders, it will be difficult to determine how regulation influences signaling or pathophysiology of glutamate without a better understanding of the mechanisms involved.
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Jenkin KA, Han Y, Lin S, He P, Yun CC. Nedd4-2-dependent Ubiquitination Potentiates the Inhibition of Human NHE3 by Cholera Toxin and Enteropathogenic Escherichia coli. Cell Mol Gastroenterol Hepatol 2021; 13:695-716. [PMID: 34823064 PMCID: PMC8789535 DOI: 10.1016/j.jcmgh.2021.11.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 11/12/2021] [Accepted: 11/15/2021] [Indexed: 12/20/2022]
Abstract
BACKGROUND & AIMS Diarrhea is one of the most common illnesses and is often caused by bacterial infection. Recently, we have shown that human Na+/H+ exchanger NHE3 (hNHE3), but not non-human NHE3s, interacts with the E3 ubiquitin ligase Nedd4-2. We hypothesize that this property of hNHE3 contributes to the increased severity of diarrhea in humans. METHODS We used humanized mice expressing hNHE3 in the intestine (hNHE3int) to compare the contribution of hNHE3 and mouse NHE3 to diarrhea induced by cholera toxin (CTX) and enteropathogenic Escherichia coli (EPEC). We measured Na+/H+ exchange activity and fluid absorption. The role of Nedd4-2 on hNHE3 activity and ubiquitination was determined by knockdown in Caco-2bbe cells. The effects of protein kinase A (PKA), the primary mediator of CTX-induced diarrhea, on Nedd4-2 and hNHE3 phosphorylation and their interaction were determined. RESULTS The effects of CTX and EPEC were greater in hNHE3int mice than in control wild-type (WT) mice, resulting in greater inhibition of NHE3 activity and increased fluid accumulation in the intestine, the hallmark of diarrhea. Activation of PKA increased ubiquitination of hNHE3 and enhanced interaction of Nedd4-2 with hNHE3 via phosphorylation of Nedd4-2 at S342. S342A mutation mitigated the Nedd4-2-hNHE3 interaction and blocked PKA-induced inhibition of hNHE3. Unlike non-human NHE3s, inhibition of hNHE3 by PKA is independent of NHE3 phosphorylation, suggesting a distinct mechanism of hNHE3 regulation. CONCLUSIONS The effects of CTX and EPEC on hNHE3 are amplified, and the unique properties of hNHE3 may contribute to diarrheal symptoms occurring in humans.
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Affiliation(s)
- Kayte A. Jenkin
- Division of Digestive Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia,School of Science, Western Sydney University, Campbelltown, NSW 2560, Australia
| | - Yiran Han
- Division of Digestive Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia,Atlanta VA Medical Center, Decatur, Georgia
| | - Songbai Lin
- Division of Digestive Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia,Atlanta VA Medical Center, Decatur, Georgia
| | - Peijian He
- Division of Digestive Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia
| | - C. Chris Yun
- Division of Digestive Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia,Atlanta VA Medical Center, Decatur, Georgia,Winship Cancer Institute, Emory University School of Medicine, Atlanta, Georgia,Correspondence Address correspondence to: Chris Yun, PhD, Division of Digestive Diseases, Emory University School of Medicine, Atlanta, Georgia 30324. fax: (404) 727-5767.
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10
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The presynaptic glycine transporter GlyT2 is regulated by the Hedgehog pathway in vitro and in vivo. Commun Biol 2021; 4:1197. [PMID: 34663888 PMCID: PMC8523746 DOI: 10.1038/s42003-021-02718-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Accepted: 09/22/2021] [Indexed: 01/20/2023] Open
Abstract
The identity of a glycinergic synapse is maintained presynaptically by the activity of a surface glycine transporter, GlyT2, which recaptures glycine back to presynaptic terminals to preserve vesicular glycine content. GlyT2 loss-of-function mutations cause Hyperekplexia, a rare neurological disease in which loss of glycinergic neurotransmission causes generalized stiffness and strong motor alterations. However, the molecular underpinnings controlling GlyT2 activity remain poorly understood. In this work, we identify the Hedgehog pathway as a robust controller of GlyT2 expression and transport activity. Modulating the activation state of the Hedgehog pathway in vitro in rodent primary spinal cord neurons or in vivo in zebrafish embryos induced a selective control in GlyT2 expression, regulating GlyT2 transport activity. Our results indicate that activation of Hedgehog reduces GlyT2 expression by increasing its ubiquitination and degradation. This work describes a new molecular link between the Hedgehog signaling pathway and presynaptic glycine availability. By modulating the activation state of the Hedgehog pathway, de la Rocha-Muñoz et al demonstrate that Hedgehog signaling controls the expression and transport activity of the neuronal glycine transporter GlyT2. This work begins to reveal a potential link between the Hedgehog signaling pathway and presynaptic glycine availability.
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11
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Yu Z, Liu C, Zhang J, Liang Z, You G. Protein kinase C regulates organic anion transporter 1 through phosphorylating ubiquitin ligase Nedd4-2. BMC Mol Cell Biol 2021; 22:53. [PMID: 34663225 PMCID: PMC8524912 DOI: 10.1186/s12860-021-00393-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Accepted: 10/08/2021] [Indexed: 12/21/2022] Open
Abstract
Background Organic anion transporter 1 (OAT1) is a drug transporter expressed on the basolateral membrane of the proximal tubule cells in kidneys. It plays an essential role in the disposition of numerous clinical therapeutics, impacting their pharmacological and toxicological properties. The activation of protein kinase C (PKC) is shown to facilitate OAT1 internalization from cell surface to intracellular compartments and thereby reducing cell surface expression and transport activity of the transporter. The PKC-regulated OAT1 internalization occurs through ubiquitination, a process catalyzed by a E3 ubiquitin ligase, neural precursor cell expressed developmentally down-regulated 4–2 (Nedd4–2). Nedd4–2 directly interacts with OAT1 and affects ubiquitination, expression and stability of the transporter. However, whether Nedd4–2 is a direct substrate for PKC-induced phosphorylation is unknown. Results In this study, we investigated the role of Nedd4–2 phosphorylation in the PKC regulation of OAT1. The results showed that PKC activation enhanced the phosphorylation of Nedd4–2 and increased the OAT1 ubiquitination, which was accompanied by a decreased OAT1 cell surface expression and transport function. And the effects of PKC could be reversed by PKC-specific inhibitor staurosporine. We further discovered that the quadruple mutant (T197A/S221A/S354A/S420A) of Nedd4–2 partially blocked the effects of PKC on Nedd4–2 phosphorylation and on OAT1 transport activity. Conclusions Our investigation demonstrates that PKC regulates OAT1 likely through direct phosphorylation of Nedd4–2. And four phosphorylation sites (T197, S221, S354, and S420) of Nedd4–2 in combination play an important role in this regulatory process.
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Affiliation(s)
- Zhou Yu
- Department of Pharmaceutics, Rutgers, the State University of New Jersey, 160 Frelinghuysen Road, Piscataway, NJ, 08854, USA
| | - Chenchang Liu
- Department of Pharmaceutics, Rutgers, the State University of New Jersey, 160 Frelinghuysen Road, Piscataway, NJ, 08854, USA
| | - Jinghui Zhang
- Department of Pharmaceutics, Rutgers, the State University of New Jersey, 160 Frelinghuysen Road, Piscataway, NJ, 08854, USA
| | - Zhengxuan Liang
- Department of Pharmaceutics, Rutgers, the State University of New Jersey, 160 Frelinghuysen Road, Piscataway, NJ, 08854, USA
| | - Guofeng You
- Department of Pharmaceutics, Rutgers, the State University of New Jersey, 160 Frelinghuysen Road, Piscataway, NJ, 08854, USA.
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12
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Wang Y, Lu S, Chen Y, Li L, Li X, Qu Z, Huang J, Fan L, Yuan C, Song N, Zhang J, Xu W, Yang S, Wang Y. Smoothened is a therapeutic target for reducing glutamate toxicity in ischemic stroke. Sci Transl Med 2021; 13:eaba3444. [PMID: 34516830 DOI: 10.1126/scitranslmed.aba3444] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
[Figure: see text].
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Affiliation(s)
- Yuqing Wang
- The Brain Science Center, Beijing Institute of Basic Medical Sciences, 100850 Beijing, China.,Institute of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue Yang Road, 200031 Shanghai, China
| | - Shanshan Lu
- The Brain Science Center, Beijing Institute of Basic Medical Sciences, 100850 Beijing, China
| | - Yifei Chen
- The Brain Science Center, Beijing Institute of Basic Medical Sciences, 100850 Beijing, China
| | - Liang Li
- The Brain Science Center, Beijing Institute of Basic Medical Sciences, 100850 Beijing, China
| | - Xia Li
- The Brain Science Center, Beijing Institute of Basic Medical Sciences, 100850 Beijing, China
| | - Zhongwei Qu
- Institute of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue Yang Road, 200031 Shanghai, China
| | - Junbo Huang
- Institute of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue Yang Road, 200031 Shanghai, China
| | - Liu Fan
- Institute of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue Yang Road, 200031 Shanghai, China
| | - Chao Yuan
- The Brain Science Center, Beijing Institute of Basic Medical Sciences, 100850 Beijing, China
| | - Nan Song
- The Brain Science Center, Beijing Institute of Basic Medical Sciences, 100850 Beijing, China
| | - Jun Zhang
- Huashan Hospital, Fudan University, 200040 Shanghai, China
| | - Wendong Xu
- Huashan Hospital, Fudan University, 200040 Shanghai, China
| | - Shenglian Yang
- The Brain Science Center, Beijing Institute of Basic Medical Sciences, 100850 Beijing, China
| | - Yizheng Wang
- The Brain Science Center, Beijing Institute of Basic Medical Sciences, 100850 Beijing, China.,Huashan Hospital, Fudan University, 200040 Shanghai, China
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13
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Kim JE, Lee DS, Park H, Kim TH, Kang TC. AMPA Receptor Antagonists Facilitate NEDD4-2-Mediated GRIA1 Ubiquitination by Regulating PP2B-ERK1/2-SGK1 Pathway in Chronic Epilepsy Rats. Biomedicines 2021; 9:biomedicines9081069. [PMID: 34440273 PMCID: PMC8391511 DOI: 10.3390/biomedicines9081069] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Revised: 08/12/2021] [Accepted: 08/19/2021] [Indexed: 11/16/2022] Open
Abstract
The neural precursor cell expressed by developmentally downregulated gene 4-2 (NEDD4-2) is a ubiquitin E3 ligase that has a high affinity toward binding and ubiquitinating glutamate ionotropic receptor α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) type subunit 1 (GRIA1, also referred to GluR1 or GluA1). Since dysregulation of GRIA1 surface expression is relevant to the responsiveness to AMPA receptor (AMPAR) antagonists (perampanel and GYKI 52466) in chronic epilepsy rats, it is likely that NEDD4-2 may be involved in the pathogenesis of intractable epilepsy. However, the role of NEDD4-2-mediated GRIA1 ubiquitination in refractory seizures to AMPAR antagonists is still unknown. In the present study, both AMPAR antagonists recovered the impaired GRIA1 ubiquitination by regulating protein phosphatase 2B (PP2B)-extracellular signal-regulated kinase 1/2 (ERK1/2)-serum and glucocorticoid-regulated kinase 1 (SGK1)-NEDD4-2 signaling pathway in responders (whose seizure activities are responsive to AMPAR), but not non-responders (whose seizure activities were uncontrolled by AMPAR antagonists). In addition, cyclosporin A (CsA, a PP2B inhibitor) co-treatment improved the effects of AMPAR antagonists in non-responders, independent of AKT signaling pathway. Therefore, our findings suggest that dysregulation of PP2B-ERK1/2-SGK1-NEDD4-2-mediated GRIA1 ubiquitination may be responsible for refractory seizures and that this pathway may be a potential therapeutic target for improving the treatment of intractable epilepsy in response to AMPAR antagonists.
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Affiliation(s)
- Ji-Eun Kim
- Correspondence: (J.-E.K.); (T.-C.K.); Tel.: +82-33-248-2522 (J.-E.K.); +82-33-248-2524 (T.-C.K.); Fax: +82-33-248-2525 (J.-E.K. & T.-C.K.)
| | | | | | | | - Tae-Cheon Kang
- Correspondence: (J.-E.K.); (T.-C.K.); Tel.: +82-33-248-2522 (J.-E.K.); +82-33-248-2524 (T.-C.K.); Fax: +82-33-248-2525 (J.-E.K. & T.-C.K.)
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14
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Peterson AR, Garcia TA, Cullion K, Tiwari-Woodruff SK, Pedapati EV, Binder DK. Targeted overexpression of glutamate transporter-1 reduces seizures and attenuates pathological changes in a mouse model of epilepsy. Neurobiol Dis 2021; 157:105443. [PMID: 34246771 DOI: 10.1016/j.nbd.2021.105443] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Revised: 07/02/2021] [Accepted: 07/05/2021] [Indexed: 01/06/2023] Open
Abstract
Astrocytic glutamate transporters are crucial for glutamate homeostasis in the brain, and dysregulation of these transporters can contribute to the development of epilepsy. Glutamate transporter-1 (GLT-1) is responsible for the majority of glutamate uptake in the dorsal forebrain and has been shown to be reduced at epileptic foci in patients and preclinical models of temporal lobe epilepsy (TLE). Current antiepileptic drugs (AEDs) work primarily by targeting neurons directly through suppression of excitatory neurotransmission or enhancement of inhibitory neurotransmission, which can lead to both behavioral and psychiatric side effects. This study investigates the therapeutic capacity of astrocyte-specific AAV-mediated GLT-1 expression in the intrahippocampal kainic acid (IHKA) model of TLE. In this study, we used Western blot analysis, immunohistochemistry, and long-term-video EEG monitoring to demonstrate that cell-type-specific upregulation of GLT-1 in astrocytes is neuroprotective at early time points during epileptogenesis, reduces seizure frequency and total time spent in seizures, and eliminates large behavioral seizures in the IHKA model of epilepsy. Our findings suggest that targeting glutamate uptake is a promising therapeutic strategy for the treatment of epilepsy.
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Affiliation(s)
- Allison R Peterson
- Division of Biomedical Sciences, Center for Glial-Neuronal Interactions, School of Medicine, University of California, Riverside, CA, USA
| | - Terese A Garcia
- Division of Biomedical Sciences, Center for Glial-Neuronal Interactions, School of Medicine, University of California, Riverside, CA, USA
| | - Kyle Cullion
- Division of Child and Adolescent Psychiatry, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Seema K Tiwari-Woodruff
- Division of Biomedical Sciences, Center for Glial-Neuronal Interactions, School of Medicine, University of California, Riverside, CA, USA
| | - Ernest V Pedapati
- Division of Child and Adolescent Psychiatry, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA; Division of Neurology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Devin K Binder
- Division of Biomedical Sciences, Center for Glial-Neuronal Interactions, School of Medicine, University of California, Riverside, CA, USA.
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15
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Meng X, Zhong J, Zeng C, Yung KKL, Zhang X, Wu X, Qu S. MiR-30a-5p Regulates GLT-1 Function via a PKCα-Mediated Ubiquitin Degradation Pathway in a Mouse Model of Parkinson's Disease. ACS Chem Neurosci 2021; 12:1578-1592. [PMID: 33882234 DOI: 10.1021/acschemneuro.1c00076] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Glutamate excitotoxicity is caused by dysfunctional glutamate transporters and plays an important role in the pathogenesis of Parkinson's disease (PD); however, the mechanisms that underlie the regulation of glutamate transporters in PD are still not fully elucidated. MicroRNAs(miRNA), which are abundant in astrocytes and neurons, have been reported to play key roles in regulating the translation of glutamate-transporter mRNA. In this study, we hypothesized that the miR-30a-5p contributes to the pathogenesis of PD by regulating the ubiquitin-mediated degradation of glutamate transporter 1 (GLT-1). We demonstrated that short-hairpin RNA-mediated knockdown of miR-30a-5p ameliorated motor deficits and pathological changes like astrogliosis and reactive microgliosis in a mouse model of PD (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice). Western blotting and immunofluorescent labeling revealed that miR-30a-5p suppressed the expression and function of GLT-1 in MPTP-treated mice and specifically in astrocytes treated with 1-methyl-4-phenylpyridinium (MPP+) (cell model of PD). Both in vitro and in vivo, we found that miR-30a-5p knockdown promoted glutamate uptake and increased GLT-1 expression by hindering GLT-1 ubiquitination and subsequent degradation in a PKCα-dependent manner. Therefore, we conclude that miR-30a-5p represents a potential therapeutic target for the treatment of PD.
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Affiliation(s)
- Xingjun Meng
- Department of Neurology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong 510515, China
- Central Laboratory and Department of Neurology, Shunde Hospital, Southern Medical University (The First People’s Hospital of Shunde Foshan), Foshan, Guangdong 528300, China
- Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and Brain-Inspired Intelligence, Guangzhou, Guangdong 510515, China
- Key Laboratory of Mental Health of the Ministry of Education, Southern Medical University, Guangzhou, Guangdong 510515, China
| | - Jianping Zhong
- Department of Neurology, Shunde Hospital of Southern Medical University (The First People’s Hospital of Shunde Foshan), Foshan, Guangdong 528300, China
| | - Chong Zeng
- Central Laboratory and Department of Neurology, Shunde Hospital, Southern Medical University (The First People’s Hospital of Shunde Foshan), Foshan, Guangdong 528300, China
| | - Ken Kin Lam Yung
- Department of Biology, Faculty of Science, Hong Kong Baptist University, Hong Kong, China
| | - Xiuping Zhang
- Teaching Center of Experimental Medicine, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guangdong 510515, China
| | - Xiaojuan Wu
- Department of Immunology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guangdong 510515, China
| | - Shaogang Qu
- Department of Neurology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong 510515, China
- Central Laboratory and Department of Neurology, Shunde Hospital, Southern Medical University (The First People’s Hospital of Shunde Foshan), Foshan, Guangdong 528300, China
- Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and Brain-Inspired Intelligence, Guangzhou, Guangdong 510515, China
- Key Laboratory of Mental Health of the Ministry of Education, Southern Medical University, Guangzhou, Guangdong 510515, China
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16
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Imoto K, Sakai Y, Okada M, Otani K, Yamawaki H. A single injection of periostin decreases cardiac voltage-gated Na + channel in rat ventricles. J Vet Med Sci 2021; 83:997-1003. [PMID: 33952782 PMCID: PMC8267192 DOI: 10.1292/jvms.21-0040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Changes in electrophysiological properties, such as ion channel expression and activity,
are closely related to arrhythmogenesis during heart failure (HF). However, a causative
factor for the electrical remodeling in HF has not been determined. Periostin (POSTN), a
matricellular protein, is increased in heart tissues of patients with HF. In the present
study, we investigated whether a single injection of POSTN affects the
electrophysiological properties in rat ventricles. After male Wistar rats were
intravenously injected with recombinant rat POSTN (64 µg/kg, 24 hr), electrocardiogram
(ECG) was recorded. Whole-cell patch clamp was performed to measure action potential (AP)
and Na+ current (INa) in isolated ventricular
myocytes. Protein expression of cardiac voltage-gated Na+ channel
(NaV1.5) in isolated ventricles was examined by Western blotting. In ECG,
POSTN-injection significantly increased RS height. POSTN-injection significantly delayed
time to peak in AP and decreased INa in the isolated
ventricular myocytes. POSTN-injection decreased NaV1.5 expression in the
isolated ventricles. It was confirmed that POSTN (1 µg/ml, 24 hr) decreased
INa and NaV1.5 protein expression in neonatal rat
ventricular myocytes. This study for the first time demonstrated that a single injection
of POSTN in rats decreased INa by suppressing
NaV1.5 expression in the ventricular myocytes, which was accompanied by a
prolongation of time to peak in AP and an increase of RS height in ECG.
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Affiliation(s)
- Keisuke Imoto
- Laboratory of Veterinary Pharmacology, School of Veterinary Medicine, Kitasato University, Higashi 23-35-1, Towada-shi, Aomori 034-8628, Japan
| | - Yuho Sakai
- Laboratory of Veterinary Pharmacology, School of Veterinary Medicine, Kitasato University, Higashi 23-35-1, Towada-shi, Aomori 034-8628, Japan
| | - Muneyoshi Okada
- Laboratory of Veterinary Pharmacology, School of Veterinary Medicine, Kitasato University, Higashi 23-35-1, Towada-shi, Aomori 034-8628, Japan
| | - Kosuke Otani
- Laboratory of Veterinary Pharmacology, School of Veterinary Medicine, Kitasato University, Higashi 23-35-1, Towada-shi, Aomori 034-8628, Japan
| | - Hideyuki Yamawaki
- Laboratory of Veterinary Pharmacology, School of Veterinary Medicine, Kitasato University, Higashi 23-35-1, Towada-shi, Aomori 034-8628, Japan
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17
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Michaluk P, Heller JP, Rusakov DA. Rapid recycling of glutamate transporters on the astroglial surface. eLife 2021; 10:e64714. [PMID: 33860761 PMCID: PMC8079145 DOI: 10.7554/elife.64714] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Accepted: 04/15/2021] [Indexed: 12/17/2022] Open
Abstract
Glutamate uptake by astroglial transporters confines excitatory transmission to the synaptic cleft. The efficiency of this mechanism depends on the transporter dynamics in the astrocyte membrane, which remains poorly understood. Here, we visualise the main glial glutamate transporter GLT1 by generating its pH-sensitive fluorescent analogue, GLT1-SEP. Fluorescence recovery after photobleaching-based imaging shows that 70-75% of GLT1-SEP dwell on the surface of rat brain astroglia, recycling with a lifetime of ~22 s. Genetic deletion of the C-terminus accelerates GLT1-SEP membrane turnover while disrupting its surface pattern, as revealed by single-molecule localisation microscopy. Excitatory activity boosts surface mobility of GLT1-SEP, involving its C-terminus, metabotropic glutamate receptors, intracellular Ca2+, and calcineurin-phosphatase activity, but not the broad-range kinase activity. The results suggest that membrane turnover, rather than lateral diffusion, is the main 'redeployment' route for the immobile fraction (20-30%) of surface-expressed GLT1. This finding reveals an important mechanism helping to control extrasynaptic escape of glutamate.
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Affiliation(s)
- Piotr Michaluk
- UCL Queen Square Institute of Neurology, University College LondonLondonUnited Kingdom
- BRAINCITY, Laboratory of Neurobiology, Nencki Institute of Experimental Biology PASWarsawPoland
| | - Janosch Peter Heller
- UCL Queen Square Institute of Neurology, University College LondonLondonUnited Kingdom
- School of Biotechnology and National Institute for Cellular Biotechnology (NICB), Dublin City UniversityGlasnevinIreland
| | - Dmitri A Rusakov
- UCL Queen Square Institute of Neurology, University College LondonLondonUnited Kingdom
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18
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Ryan RM, Ingram SL, Scimemi A. Regulation of Glutamate, GABA and Dopamine Transporter Uptake, Surface Mobility and Expression. Front Cell Neurosci 2021; 15:670346. [PMID: 33927596 PMCID: PMC8076567 DOI: 10.3389/fncel.2021.670346] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2021] [Accepted: 03/15/2021] [Indexed: 01/31/2023] Open
Abstract
Neurotransmitter transporters limit spillover between synapses and maintain the extracellular neurotransmitter concentration at low yet physiologically meaningful levels. They also exert a key role in providing precursors for neurotransmitter biosynthesis. In many cases, neurons and astrocytes contain a large intracellular pool of transporters that can be redistributed and stabilized in the plasma membrane following activation of different signaling pathways. This means that the uptake capacity of the brain neuropil for different neurotransmitters can be dynamically regulated over the course of minutes, as an indirect consequence of changes in neuronal activity, blood flow, cell-to-cell interactions, etc. Here we discuss recent advances in the mechanisms that control the cell membrane trafficking and biophysical properties of transporters for the excitatory, inhibitory and modulatory neurotransmitters glutamate, GABA, and dopamine.
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Affiliation(s)
- Renae M. Ryan
- School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, Sydney, NSW, Australia
| | - Susan L. Ingram
- Department of Neurological Surgery, Oregon Health & Science University, Portland, OR, United States
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19
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Du Y, Wang T, Guo J, Li W, Yang T, Szendrey M, Zhang S. Kv1.5 channels are regulated by PKC-mediated endocytic degradation. J Biol Chem 2021; 296:100514. [PMID: 33676894 PMCID: PMC8050386 DOI: 10.1016/j.jbc.2021.100514] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Revised: 02/28/2021] [Accepted: 03/03/2021] [Indexed: 11/28/2022] Open
Abstract
The voltage-gated potassium channel Kv1.5 plays important roles in the repolarization of atrial action potentials and regulation of the vascular tone. While the modulation of Kv1.5 function has been well studied, less is known about how the protein levels of Kv1.5 on the cell membrane are regulated. Here, through electrophysiological and biochemical analyses of Kv1.5 channels heterologously expressed in HEK293 cells and neonatal rat ventricular myocytes, as well as native Kv1.5 in human induced pluripotent stem cell (iPSC)-derived atrial cardiomyocytes, we found that activation of protein kinase C (PKC) with phorbol 12-myristate 13-acetate (PMA, 10 nM) diminished Kv1.5 current (IKv1.5) and protein levels of Kv1.5 in the plasma membrane. Mechanistically, PKC activation led to monoubiquitination and degradation of the mature Kv1.5 proteins. Overexpression of Vps24, a protein that sorts transmembrane proteins into lysosomes via the multivesicular body (MVB) pathway, accelerated, whereas the lysosome inhibitor bafilomycin A1 completely prevented PKC-mediated Kv1.5 degradation. Kv1.5, but not Kv1.1, Kv1.2, Kv1.3, or Kv1.4, was uniquely sensitive to PMA treatment. Sequence alignments suggested that residues within the N terminus of Kv1.5 are essential for PKC-mediated Kv1.5 reduction. Using N-terminal truncation as well as site-directed mutagenesis, we identified that Thr15 is the target site for PKC that mediates endocytic degradation of Kv1.5 channels. These findings indicate that alteration of protein levels in the plasma membrane represents an important regulatory mechanism of Kv1.5 channel function under PKC activation conditions.
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Affiliation(s)
- Yuan Du
- Department of Cardiovascular Medicine, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China; Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
| | - Tingzhong Wang
- Department of Cardiovascular Medicine, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China; Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
| | - Jun Guo
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
| | - Wentao Li
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
| | - Tonghua Yang
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
| | - Mark Szendrey
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
| | - Shetuan Zhang
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada.
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20
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McCarty MF, DiNicolantonio JJ, Lerner A. A Fundamental Role for Oxidants and Intracellular Calcium Signals in Alzheimer's Pathogenesis-And How a Comprehensive Antioxidant Strategy May Aid Prevention of This Disorder. Int J Mol Sci 2021; 22:2140. [PMID: 33669995 PMCID: PMC7926325 DOI: 10.3390/ijms22042140] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 02/16/2021] [Accepted: 02/18/2021] [Indexed: 12/13/2022] Open
Abstract
Oxidative stress and increased cytoplasmic calcium are key mediators of the detrimental effects on neuronal function and survival in Alzheimer's disease (AD). Pathways whereby these perturbations arise, and then prevent dendritic spine formation, promote tau hyperphosphorylation, further amplify amyloid β generation, and induce neuronal apoptosis, are described. A comprehensive program of nutraceutical supplementation, comprised of the NADPH oxidase inhibitor phycocyanobilin, phase two inducers, the mitochondrial antioxidant astaxanthin, and the glutathione precursor N-acetylcysteine, may have important potential for antagonizing the toxic effects of amyloid β on neurons and thereby aiding prevention of AD. Moreover, nutraceutical antioxidant strategies may oppose the adverse impact of amyloid β oligomers on astrocyte clearance of glutamate, and on the ability of brain capillaries to export amyloid β monomers/oligomers from the brain. Antioxidants, docosahexaenoic acid (DHA), and vitamin D, have potential for suppressing microglial production of interleukin-1β, which potentiates the neurotoxicity of amyloid β. Epidemiology suggests that a health-promoting lifestyle, incorporating a prudent diet, regular vigorous exercise, and other feasible measures, can cut the high risk for AD among the elderly by up to 60%. Conceivably, complementing such lifestyle measures with long-term adherence to the sort of nutraceutical regimen outlined here may drive down risk for AD even further.
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Affiliation(s)
| | | | - Aaron Lerner
- Chaim Sheba Medical Center, The Zabludowicz Research Center for Autoimmune Diseases, Tel Hashomer 5262000, Israel
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21
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Maeda K, Tasaki M, Ando Y, Ohtsubo K. Galectin-lattice sustains function of cationic amino acid transporter and insulin secretion of pancreatic β cells. J Biochem 2021; 167:587-596. [PMID: 31960919 DOI: 10.1093/jb/mvaa007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Accepted: 01/09/2020] [Indexed: 01/01/2023] Open
Abstract
Maintenance of cell surface residency and function of glycoproteins by lectins are essential for regulating cellular functions. Galectins are β-galactoside-binding lectins and form a galectin-lattice, which regulates stability, clustering, membrane sub-domain localization and endocytosis of plasmalemmal glycoproteins. We have previously reported that galectin-2 (Gal-2) forms a complex with cationic amino acid transporter 3 (CAT3) in pancreatic β cells, although the biological significance of the molecular interaction between Gal-2 and CAT3 has not been elucidated. In this study, we demonstrated that the structure of N-glycan of CAT3 was either tetra- or tri-antennary branch structure carrying β-galactosides, which works as galectin-ligands. Indeed, CAT3 bound to Gal-2 using β-galactoside epitope. Moreover, the disruption of the glycan-mediated bindings between galectins and CAT3 significantly reduced cell surface expression levels of CAT3. The reduced cell surface residency of CAT3 attenuated the cellular arginine uptake activities and subsequently reduced nitric oxide production, and thus impaired the arginine-stimulated insulin secretion of pancreatic β cells. These results indicate that galectin-lattice stabilizes CAT3 by preventing endocytosis to sustain the arginine-stimulated insulin secretion of pancreatic β cells. This provides a novel cell biological insight into the endocrinological mechanism of nutrition metabolism and homeostasis.
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Affiliation(s)
- Kento Maeda
- Department of Analytical Biochemistry;, Graduate School of Health Sciences, Kumamoto University, 4-24-1 Kuhonji, Chuo-Ku, Kumamoto 862-0976, Japan
| | - Masayoshi Tasaki
- Department of Morphological and Physiological Sciences, Graduate School of Health Sciences, Kumamoto University, 4-24-1 Kuhonji, Chuo-Ku, Kumamoto 862-0976, Japan.,Department of Neurology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto 860-0811, Japan
| | - Yukio Ando
- Depatment of Amyloidosis Research, Nagasaki International University, Nagasaki 859-3243, Japan
| | - Kazuaki Ohtsubo
- Department of Analytical Biochemistry;, Graduate School of Health Sciences, Kumamoto University, 4-24-1 Kuhonji, Chuo-Ku, Kumamoto 862-0976, Japan.,Department of Analytical Biochemistry, Faculty of Life Sciences, Kumamoto University, 4-24-1 Kuhonji, Chuo-Ku, Kumamoto 862-0976, Japan
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22
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Perez-Jimenez E, Viana R, Muñoz-Ballester C, Vendrell-Tornero C, Moll-Diaz R, Garcia-Gimeno MA, Sanz P. Endocytosis of the glutamate transporter 1 is regulated by laforin and malin: Implications in Lafora disease. Glia 2020; 69:1170-1183. [PMID: 33368637 DOI: 10.1002/glia.23956] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 11/10/2020] [Accepted: 12/10/2020] [Indexed: 01/13/2023]
Abstract
Lafora disease (LD) is a fatal rare type of progressive myoclonus epilepsy that appears during early adolescence. The disease is caused by mutations in EPM2A or EPM2B genes, which encode laforin, a glucan phosphatase, and malin, an E3-ubiquitin ligase, respectively. Although the exact roles of laforin and malin are still not well understood, it is known that they work as a complex in which laforin recruits targets that will be ubiquitinated by malin. Recently, we suggested that the type of epilepsy that accompanies LD could be due to deficiencies in the function of the astrocytic glutamate transporter GLT-1. We described that astrocytes from LD mouse models presented decreased levels of GLT-1 at the plasma membrane, leading to increased levels of glutamate in the brain parenchyma. In this work, we present evidence indicating that in the absence of a functional laforin/malin complex (as in LD cellular models) there is an alteration in the ubiquitination of GLT-1, which could be the cause of the reduction in the levels of GLT-1 at the plasma membrane. On the contrary, overexpression of the laforin/malin complex promotes the retention of GLT-1 at the plasma membrane. This retention may be due to the direct ubiquitination of GLT-1 and/or to an opposite effect of this complex on the dynamics of the Nedd4.2-mediated endocytosis of the transporter. This work, therefore, presents new pieces of evidence on the regulation of GLT-1 by the laforin/malin complex, highlighting its value as a therapeutic target for the amelioration of the type of epilepsy that accompanies LD.
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Affiliation(s)
- Eva Perez-Jimenez
- Consejo Superior de Investigaciones Científicas, Instituto de Biomedicina de Valencia, Valencia, Spain.,CIBERER, Centro de Investigación Biomédica en Red de Enfermedades Raras, Instituto de Biomedicina de Valencia, Valencia, Spain
| | - Rosa Viana
- Consejo Superior de Investigaciones Científicas, Instituto de Biomedicina de Valencia, Valencia, Spain.,CIBERER, Centro de Investigación Biomédica en Red de Enfermedades Raras, Instituto de Biomedicina de Valencia, Valencia, Spain
| | - Carmen Muñoz-Ballester
- Consejo Superior de Investigaciones Científicas, Instituto de Biomedicina de Valencia, Valencia, Spain.,CIBERER, Centro de Investigación Biomédica en Red de Enfermedades Raras, Instituto de Biomedicina de Valencia, Valencia, Spain
| | - Carlos Vendrell-Tornero
- Consejo Superior de Investigaciones Científicas, Instituto de Biomedicina de Valencia, Valencia, Spain.,CIBERER, Centro de Investigación Biomédica en Red de Enfermedades Raras, Instituto de Biomedicina de Valencia, Valencia, Spain
| | - Raquel Moll-Diaz
- Consejo Superior de Investigaciones Científicas, Instituto de Biomedicina de Valencia, Valencia, Spain.,CIBERER, Centro de Investigación Biomédica en Red de Enfermedades Raras, Instituto de Biomedicina de Valencia, Valencia, Spain
| | | | - Pascual Sanz
- Consejo Superior de Investigaciones Científicas, Instituto de Biomedicina de Valencia, Valencia, Spain.,CIBERER, Centro de Investigación Biomédica en Red de Enfermedades Raras, Instituto de Biomedicina de Valencia, Valencia, Spain
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23
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Masaki K, Hiraki Y, Onishi H, Satoh Y, Roche PA, Tanaka S, Furuta K. Ligation of MHC Class II Induces PKC-Dependent Clathrin-Mediated Endocytosis of MHC Class II. Cells 2020; 9:E1810. [PMID: 32751549 PMCID: PMC7465434 DOI: 10.3390/cells9081810] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 07/24/2020] [Accepted: 07/28/2020] [Indexed: 11/17/2022] Open
Abstract
In addition to antigen presentation to CD4+ T cells, aggregation of cell surface major histocompatibility complex class II (MHC-II) molecules induces signal transduction in antigen presenting cells that regulate cellular functions. We previously reported that crosslinking of MHC-II induced the endocytosis of MHC-II, which was associated with decreased surface expression levels in murine dendritic cells (DCs) and resulted in impaired activation of CD4+ T cells. However, the downstream signal that induces MHC-II endocytosis remains to be elucidated. In this study, we found that the crosslinking of MHC-II induced intracellular Ca2+ mobilization, which was necessary for crosslinking-induced MHC-II endocytosis. We also found that these events were suppressed by inhibitors of Syk and phospholipase C (PLC). Treatments with a phorbol ester promoted MHC-II endocytosis, whereas inhibitors of protein kinase C (PKC) suppressed crosslinking-induced endocytosis of MHC-II. These results suggest that PKC could be involved in this process. Furthermore, crosslinking-induced MHC-II endocytosis was suppressed by inhibitors of clathrin-dependent endocytosis. Our results indicate that the crosslinking of MHC-II could stimulate Ca2+ mobilization and induce the clathrin-dependent endocytosis of MHC-II in murine DCs.
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Affiliation(s)
- Kento Masaki
- Department of Immunobiology, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Tsushima naka 1-1-1, Kita-ku, Okayama 700-8530, Japan; (K.M.); (Y.H.); (Y.S.)
| | - Yuhji Hiraki
- Department of Immunobiology, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Tsushima naka 1-1-1, Kita-ku, Okayama 700-8530, Japan; (K.M.); (Y.H.); (Y.S.)
| | - Hiroka Onishi
- Department of Immunobiology, Faculty of Pharmacy and Pharmaceutical Sciences, Okayama University, Tsushima naka 1-1-1, Kita-ku, Okayama 700-8530, Japan;
| | - Yuka Satoh
- Department of Immunobiology, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Tsushima naka 1-1-1, Kita-ku, Okayama 700-8530, Japan; (K.M.); (Y.H.); (Y.S.)
| | - Paul A. Roche
- Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA;
| | - Satoshi Tanaka
- Department of Pharmacology, Division of Pathological Sciences, Kyoto Pharmaceutical University, Misasagi Nakauchi-cho 5, Yamashina-ku, Kyoto 607-8414, Japan;
| | - Kazuyuki Furuta
- Department of Immunobiology, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Tsushima naka 1-1-1, Kita-ku, Okayama 700-8530, Japan; (K.M.); (Y.H.); (Y.S.)
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24
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Tao K, Cai Q, Zhang X, Zhu L, Liu Z, Li F, Wang Q, Liu L, Feng D. Astrocytic histone deacetylase 2 facilitates delayed depression and memory impairment after subarachnoid hemorrhage by negatively regulating glutamate transporter-1. ANNALS OF TRANSLATIONAL MEDICINE 2020; 8:691. [PMID: 32617311 PMCID: PMC7327310 DOI: 10.21037/atm-20-4330] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Background Delayed cognitive impairment (DCI) after subarachnoid hemorrhage (SAH) is one of the most common sequelae in patients. This study aimed to investigate the characteristics of the course and glutamatergic pathogenesis of DCI after SAH in mice. Methods A SAH mouse model of internal carotid puncture was used. Depressive and cognitive behaviors were detected by forced swimming and sucrose preference tests and Morris water maze test, respectively. Microdialysis and high-performance liquid chromatography (HPLC) were used to detect the interstitial glutamate. The expressions of histone deacetylases (HDACs), glutamate transporters, and glutamate receptors were examined. Primary astrocytes magnetically sorted from adult mice were cultured for glutamate uptake assay and protein and mRNA detection. Selective HDAC2 inhibitor and glutamate transporter-1 (GLT-1) inhibitor administered via were intraperitoneal injection to evaluate their effects on DCI in SAH mice. Results Depression and memory impairment lasted for more than 12 weeks and peaked at 8 weeks after SAH. Interstitial glutamate accumulation in the hippocampus and impaired glutamate uptake in astrocytes of the SAH mice were found during DCI, which could be explained by there being a significant decrease in GLT-1 expression but not in glutamate and aspartate transporter (GLAST) in hippocampal astrocytes. Meanwhile, the phosphorylation level of excitatory glutamate receptors (GluN2B and GluA1) in the hippocampus was significantly reduced, although there was no significant change in the expression of the receptors. Importantly, the expression of HDAC2 increased most significantly in astrocytes after SAH compared with that of other subtypes of HDACs. Inhibition of HDAC2 markedly rescued the decrease in GLT-1 expression after SAH through transcriptional regulation. Behavioral results showed that a selective HDAC2 inhibitor effectively improved DCI in SAH mice, but this effect could be weakened by GLT-1 inhibition. Conclusions In summary, our study suggests that the dysfunction of GLT-1-mediated glutamate uptake in astrocytes may be a key pathological mechanism of DCI after SAH, and that a specific inhibitor of HDAC2 may exert a potential therapy.
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Affiliation(s)
- Kai Tao
- Department of Neurosurgery and Institute for Functional Brain Disorders, Tangdu Hospital, Fourth Military Medical University, Xi'an, China
| | - Qing Cai
- Department of Neurosurgery and Institute for Functional Brain Disorders, Tangdu Hospital, Fourth Military Medical University, Xi'an, China
| | - Xudong Zhang
- China-Nepal Friendship Medical Research Center of Rajiv Kumar Jha, School of Clinical Medicine, Xi'an Medical University, Xi'an, China
| | - Lin Zhu
- Department of Neurosurgery and Institute for Functional Brain Disorders, Tangdu Hospital, Fourth Military Medical University, Xi'an, China
| | - Zhenru Liu
- School of Basic Medicine, Fourth Military Medical University, Xi'an, China
| | - Fei Li
- Department of Neurosurgery and Institute for Functional Brain Disorders, Tangdu Hospital, Fourth Military Medical University, Xi'an, China
| | - Qiang Wang
- Department of Neurosurgery and Institute for Functional Brain Disorders, Tangdu Hospital, Fourth Military Medical University, Xi'an, China
| | - Lei Liu
- Department of Gastroenterology, Tangdu Hospital, Fourth Military Medical University, Xi'an, China
| | - Dayun Feng
- Department of Neurosurgery and Institute for Functional Brain Disorders, Tangdu Hospital, Fourth Military Medical University, Xi'an, China.,School of Basic Medicine, Fourth Military Medical University, Xi'an, China
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25
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Gerbino A, De Zio R, Russo D, Milella L, Milano S, Procino G, Pusch M, Svelto M, Carmosino M. Role of PKC in the Regulation of the Human Kidney Chloride Channel ClC-Ka. Sci Rep 2020; 10:10268. [PMID: 32581267 PMCID: PMC7314819 DOI: 10.1038/s41598-020-67219-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Accepted: 06/02/2020] [Indexed: 12/03/2022] Open
Abstract
The physiological role of the renal ClC-Ka/ClC-K1 channels is to confer a high Cl- permeability to the thin Ascending Limb of Henle (tAL), which in turn is essential for establishing the high osmolarity of the renal medulla that drives water reabsorption from collecting ducts. Here, we investigated by whole-cell patch-clamp measurements on HEK293 cells co-expressing ClC-Ka (tagged with GFP) and the accessory subunit barttin (tagged with m-Cherry) the effect of a natural diuretic extract from roots of Dandelion (DRE), and other compounds activating PKC, such as ATP, on ClC-Ka activity and its membrane localization. Treatment with 400 µg/ml DRE significantly inhibited Cl- currents time-dependently within several minutes. Of note, the same effect on Cl- currents was obtained upon treatment with 100 µM ATP. Pretreatment of cells with either the intracellular Ca2+ chelator BAPTA-AM (30 μM) or the PKC inhibitor Calphostin C (100 nM) reduced the inhibitory effect of DRE. Conversely, 1 µM of phorbol meristate acetate (PMA), a specific PKC activator, mimicked the inhibitory effect of DRE on ClC-Ka. Finally, we found that pretreatment with 30 µM Heclin, an E3 ubiquitin ligase inhibitor, did not revert DRE-induced Cl- current inhibition. In agreement with this, live-cell confocal analysis showed that DRE treatment did not induce ClC-Ka internalization. In conclusion, we demonstrate for the first time that the activity of ClC-Ka in renal cells could be significantly inhibited by the activation of PKC elicited by classical maneuvers, such as activation of purinergic receptors, or by exposure to herbal extracts that activates a PKC-dependent pathway. Overall, we provide both new information regarding the regulation of ClC-Ka and a proof-of-concept study for the use of DRE as new diuretic.
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Affiliation(s)
- Andrea Gerbino
- National Research Council, Institute of Biomembrane and Bioenergetics, Bari, IT, Italy.,Department of Biosciences, Biotechnologies and Biopharamceutics, University of Bari, Bari, IT, Italy
| | - Roberta De Zio
- Department of Biosciences, Biotechnologies and Biopharamceutics, University of Bari, Bari, IT, Italy
| | - Daniela Russo
- Department of Sciences, University of Basilicata, Potenza, IT, Italy
| | - Luigi Milella
- Department of Sciences, University of Basilicata, Potenza, IT, Italy
| | - Serena Milano
- Department of Biosciences, Biotechnologies and Biopharamceutics, University of Bari, Bari, IT, Italy
| | - Giuseppe Procino
- Department of Biosciences, Biotechnologies and Biopharamceutics, University of Bari, Bari, IT, Italy
| | - Michael Pusch
- National Research Council, Institute of Biophysics, Genova, IT, Italy
| | - Maria Svelto
- National Research Council, Institute of Biomembrane and Bioenergetics, Bari, IT, Italy.,Department of Biosciences, Biotechnologies and Biopharamceutics, University of Bari, Bari, IT, Italy
| | - Monica Carmosino
- Department of Sciences, University of Basilicata, Potenza, IT, Italy. .,Department of Biosciences, Biotechnologies and Biopharamceutics, University of Bari, Bari, IT, Italy.
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26
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Ma S, Zheng X, Zheng T, Huang F, Jiang J, Luo H, Guo Q, Hu B. Amitriptyline influences the mechanical withdrawal threshold in bone cancer pain rats by regulating glutamate transporter GLAST. Mol Pain 2020; 15:1744806919855834. [PMID: 31218920 PMCID: PMC6637840 DOI: 10.1177/1744806919855834] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Patients with cancer, especially breast, prostate, and lung cancer, commonly experience bone metastases that are difficult to manage and are associated with bone cancer pain. Amitriptyline is often used to treat chronic pain, such as neuropathic pain. In this study, the effects of amitriptyline on the mechanical withdrawal threshold and its underlying mechanisms were evaluated in rat models of bone cancer pain. Walker 256 rat mammary gland carcinoma cells were injected into the bone marrow cavity of the right tibia of rats to provoke bone cancer pain. Then, amitriptyline was intraperitoneally administered twice daily from fifth day after the operation. Rats with bone cancer showed an apparent decline in the mechanical withdrawal threshold at day 11 after Walker 256 cells inoculation. The levels of the glutamate-aspartate transporter in the spinal cord dorsal horn decreased remarkably, and the concentration of the excitatory amino acid glutamate in the cerebrospinal fluid increased substantially. Amitriptyline injection could prevent the decline of mechanical withdrawal threshold in bone cancer pain rats. In addition, glutamate-aspartate transporter was upregulated on the glial cell surface, and glutamate levels were reduced in the cerebrospinal fluid. However, amitriptyline injection could not prevent the bone cancer pain-induced reduction in glutamate-aspartate transporter in the glial cell cytosol, it further downregulated cytosolic glutamate-aspartate transporter. Amitriptyline had no significant effect on GLAST messenger RNA expression, and bone cancer pain-invoked protein kinase A/protein kinase C upregulation was prevented. Taken together, these results suggest that the intraperitoneal injection of amitriptyline can prevent the decrease of mechanical withdrawal threshold in bone cancer pain rats, the underlying mechanisms may be associated with the inhibition of protein kinase A/protein kinase C expression, thus promoting glutamate-aspartate transporter trafficking onto the glial cell surface and reducing excitatory amino acid concentrations in the cerebrospinal fluid.
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Affiliation(s)
- Simeng Ma
- 1 Fujian Provincial Hospital, Fuzhou, China
| | | | - Ting Zheng
- 1 Fujian Provincial Hospital, Fuzhou, China
| | | | | | | | | | - Bin Hu
- 1 Fujian Provincial Hospital, Fuzhou, China
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27
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Pajarillo E, Rizor A, Lee J, Aschner M, Lee E. The role of astrocytic glutamate transporters GLT-1 and GLAST in neurological disorders: Potential targets for neurotherapeutics. Neuropharmacology 2019; 161:107559. [PMID: 30851309 PMCID: PMC6731169 DOI: 10.1016/j.neuropharm.2019.03.002] [Citation(s) in RCA: 190] [Impact Index Per Article: 38.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2018] [Revised: 02/28/2019] [Accepted: 03/02/2019] [Indexed: 12/12/2022]
Abstract
Glutamate is the primary excitatory neurotransmitter in the central nervous system (CNS) which initiates rapid signal transmission in the synapse before its re-uptake into the surrounding glia, specifically astrocytes. The astrocytic glutamate transporters glutamate-aspartate transporter (GLAST) and glutamate transporter-1 (GLT-1) and their human homologs excitatory amino acid transporter 1 (EAAT1) and 2 (EAAT2), respectively, are the major transporters which take up synaptic glutamate to maintain optimal extracellular glutamic levels, thus preventing accumulation in the synaptic cleft and ensuing excitotoxicity. Growing evidence has shown that excitotoxicity is associated with various neurological disorders, including amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD), Parkinson's disease (PD), manganism, ischemia, schizophrenia, epilepsy, and autism. While the mechanisms of neurological disorders are not well understood, the dysregulation of GLAST/GLT-1 may play a significant role in excitotoxicity and associated neuropathogenesis. The expression and function of GLAST/GLT-1 may be dysregulated at the genetic, epigenetic, transcriptional or translational levels, leading to high levels of extracellular glutamate and excitotoxicity. Consequently, understanding the regulatory mechanisms of GLAST/GLT-1 has been an area of interest in developing therapeutics for the treatment of neurological disorders. Pharmacological agents including β-lactam antibiotics, estrogen/selective estrogen receptor modulators (SERMs), growth factors, histone deacetylase inhibitors (HDACi), and translational activators have shown significant efficacy in enhancing the expression and function of GLAST/GLT-1 and glutamate uptake both in vitro and in vivo. This comprehensive review will discuss the regulatory mechanisms of GLAST/GLT-1, their association with neurological disorders, and the pharmacological agents which mediate their expression and function. This article is part of the issue entitled 'Special Issue on Neurotransmitter Transporters'.
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Affiliation(s)
- Edward Pajarillo
- Department of Pharmaceutical Sciences, College of Pharmacy, Florida A&M University, Tallahassee, FL, 32301, USA
| | - Asha Rizor
- Department of Pharmaceutical Sciences, College of Pharmacy, Florida A&M University, Tallahassee, FL, 32301, USA
| | - Jayden Lee
- Department of Speech, Language & Hearing Sciences, Boston University, Boston, MA, 02215, USA
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, 10461, USA
| | - Eunsook Lee
- Department of Pharmaceutical Sciences, College of Pharmacy, Florida A&M University, Tallahassee, FL, 32301, USA.
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28
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Barthelemy C, André B. Ubiquitylation and endocytosis of the human LAT1/SLC7A5 amino acid transporter. Sci Rep 2019; 9:16760. [PMID: 31728037 PMCID: PMC6856120 DOI: 10.1038/s41598-019-53065-w] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Accepted: 10/22/2019] [Indexed: 12/11/2022] Open
Abstract
The human L-type amino acid transporter 1 (LAT1), also known as SLC7A5, catalyzes the transport of large neutral amino acids across the plasma membrane. As the main transporter of several essential amino acids, notably leucine, LAT1 plays an important role in mTORC1 activation. Furthermore, it is overexpressed in various types of cancer cells, where it contributes importantly to sustained growth. Despite the importance of LAT1 in normal and tumor cells, little is known about the mechanisms that might control its activity, for example by promoting its downregulation via endocytosis. Here we report that in HeLa cells, activation of protein kinase C by phorbol 12-myristate 13-acetate (PMA) triggers efficient endocytosis and degradation of LAT1. Under these conditions we found LAT1 downregulation to correlate with increased LAT1 ubiquitylation. This modification was considerably reduced in cells depleted of the Nedd4-2 ubiquitin ligase. By systematically mutagenizing the residues of the LAT1 cytosolic tails, we identified a group of three close lysines (K19, K25, K30) in the N-terminal tail that are important for PMA-induced ubiquitylation and downregulation. Our study thus unravels a mechanism of induced endocytosis of LAT1 elicited by Nedd4-2-mediated ubiquitylation of the transporter's N-terminal tail.
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Affiliation(s)
- Céline Barthelemy
- Molecular Physiology of the Cell, Université libre de Bruxelles (ULB), IBMM (Biopark), Gosselies, Belgium
| | - Bruno André
- Molecular Physiology of the Cell, Université libre de Bruxelles (ULB), IBMM (Biopark), Gosselies, Belgium.
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29
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Peterson AR, Binder DK. Post-translational Regulation of GLT-1 in Neurological Diseases and Its Potential as an Effective Therapeutic Target. Front Mol Neurosci 2019; 12:164. [PMID: 31338020 PMCID: PMC6629900 DOI: 10.3389/fnmol.2019.00164] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Accepted: 06/14/2019] [Indexed: 12/12/2022] Open
Abstract
Glutamate transporter-1 (GLT-1) is a Na+-dependent transporter that plays a key role in glutamate homeostasis by removing excess glutamate in the central nervous system (CNS). GLT-1 dysregulation occurs in various neurological diseases including Huntington's disease (HD), Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and epilepsy. Downregulation or dysfunction of GLT-1 has been a common finding across these diseases but how this occurs is still under investigation. This review aims to highlight post-translational regulation of GLT-1 which leads to its downregulation including sumoylation, palmitoylation, nitrosylation, ubiquitination, and subcellular localization. Various therapeutic interventions to restore GLT-1, their proposed mechanism of action and functional effects will be examined as potential treatments to attenuate the neurological symptoms associated with loss or downregulation of GLT-1.
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Affiliation(s)
- Allison R Peterson
- Center for Glial-Neuronal Interactions, Division of Biomedical Sciences, School of Medicine, University of California, Riverside, Riverside, CA, United States
| | - Devin K Binder
- Center for Glial-Neuronal Interactions, Division of Biomedical Sciences, School of Medicine, University of California, Riverside, Riverside, CA, United States
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30
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Bartolomé-Martín D, Ibáñez I, Piniella D, Martínez-Blanco E, Pelaz SG, Zafra F. Identification of potassium channel proteins Kv7.2/7.3 as common partners of the dopamine and glutamate transporters DAT and GLT-1. Neuropharmacology 2019; 161:107568. [PMID: 30885609 DOI: 10.1016/j.neuropharm.2019.03.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2018] [Revised: 02/19/2019] [Accepted: 03/06/2019] [Indexed: 12/12/2022]
Abstract
Dopamine and glutamate transporters (DAT and GLT-1, respectively) share some biophysical characteristics, as both are secondary active carriers coupled to electrochemical ion gradients. In order to identify common or specific components of their respective proteomes, we performed a proximity labelling assay (BioID) in the hippocampal cell line HT22. While most of the identified proteins were specific for each transporter (and will be analyzed elsewhere), we detected two membrane proteins in the shared interactome of GLT-1 and DAT: the transmembrane protein 263 (Tmem263) and the potassium channel protein Kv7.3. However, only Kv7.3 formed immunoprecipitable complexes with GLT-1 and DAT in lysates of transfected HEK293 cells. Moreover, either DAT or GLT-1 co-clustered with Kv7.2/7.3 along the axonal tracts in co-transfected primary neurons, indicating a close spatial proximity between these proteins. Kv7.3, forming heterotetramers with the closely related subunit Kv7.2, underlies the M-currents that control the resting membrane potential and spiking activity in neurons. To investigate whether the presence of the potassium channel affected DAT or GLT-1 function, we performed uptake determinations using radioactive substrate and electrophysiological measurements. Uptake through both transporters was mildly stimulated by the presence of the channel, an effect that was reversed by the potassium channel blocker XE-991. Electrophysiological recording (in transfected HT22 and differentiated SH-SY5Y cells) indicated that the depolarizing effect induced by the presence of the neurotransmitter was reverted by the activity of the potassium channel. Altogether, these data suggest a tight spatial and functional relationship between the DAT/GLT-1 transporters and the Kv7.2/7.3 potassium channel that immediately readjusts the membrane potential of the neuron, probably to limit the neurotransmitter-mediated neuronal depolarization. This article is part of the issue entitled 'Special Issue on Neurotransmitter Transporters'.
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Affiliation(s)
- David Bartolomé-Martín
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Madrid, Spain; IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
| | - Ignacio Ibáñez
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Madrid, Spain; IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
| | - Dolores Piniella
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Madrid, Spain; IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
| | - Elena Martínez-Blanco
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Madrid, Spain; IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
| | - Sara G Pelaz
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Madrid, Spain
| | - Francisco Zafra
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Madrid, Spain; IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain.
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Wang H, Zhang J, You G. The mechanistic links between insulin and human organic anion transporter 4. Int J Pharm 2019; 555:165-174. [PMID: 30453017 DOI: 10.1016/j.ijpharm.2018.11.040] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Revised: 11/10/2018] [Accepted: 11/15/2018] [Indexed: 11/18/2022]
Abstract
Human organic anion transporter 4 (hOAT4) belongs to a class of organic anion transporters that exert critical function in the secretion, absorption, and distribution of numerous drugs in the body, such as anti-viral drugs, anti-cancer therapeutics, antibiotics, antihypertensive medicine, and anti-inflammatory drugs. hOAT4 is richly existent in the kidney and placenta. We previously established that serum- and glucocorticoid-inducible kinases (sgk) stimulate hOAT4 expression and transport activity by abrogating the inhibitory effect of a ubiquitin ligase Nedd4-2. Insulin is one of the upstream signaling molecules for sgk. We therefore investigated the effect of insulin on hOAT4 function. We showed that insulin stimulated hOAT4 expression and transport activity, and the action of insulin was abolished in cells overexpressing Nedd4-2-specific siRNA to knockdown the endogenous Nedd4-2. We further showed that insulin phosphorylated serine 327 on Nedd4-2 and weakened the interaction between hOAT4 and Nedd4-2. Interestingly, in cells overexpressing sgk2, the stimulatory effect of insulin on hOAT4 was diminished. In addition, the stimulatory effect of insulin on hOAT4 was blocked by wortmannin and buparlisib, two PI3K inhibitors. In conclusion, our study demonstrated that insulin stimulates hOAT4 expression and transport activity by abrogating the inhibition effect of Nedd4-2 on the transporter. Moreover, insulin regulates hOAT4 by competing with sgk2 rather than through sgk2.
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Affiliation(s)
- Haoxun Wang
- Department of Pharmaceutics, Rutgers, The State University of New Jersey, Piscataway, NJ, USA
| | - Jinghui Zhang
- Department of Pharmaceutics, Rutgers, The State University of New Jersey, Piscataway, NJ, USA
| | - Guofeng You
- Department of Pharmaceutics, Rutgers, The State University of New Jersey, Piscataway, NJ, USA.
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Cabrera-Pastor A, Arenas YM, Taoro-Gonzalez L, Montoliu C, Felipo V. Chronic hyperammonemia alters extracellular glutamate, glutamine and GABA and membrane expression of their transporters in rat cerebellum. Modulation by extracellular cGMP. Neuropharmacology 2019; 161:107496. [PMID: 30641078 DOI: 10.1016/j.neuropharm.2019.01.011] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Revised: 12/15/2018] [Accepted: 01/10/2019] [Indexed: 12/14/2022]
Abstract
Trafficking of glutamate, glutamine and GABA between astrocytes and neurons is essential to maintain proper neurotransmission. Chronic hyperammonemia alters neurotransmission and cognitive function. The aims of this work were to analyze in cerebellum of rats the effects of chronic hyperammonemia on: a) extracellular glutamate, glutamine and GABA concentrations; b) membrane expression of glutamate, glutamine and GABA transporters; c) how they are modulated by extracellular cGMP. Hyperammonemic rats show increased levels of extracellular glutamate, glutamine, GABA and citrulline in cerebellum in vivo. Hyperammonemic rats show: a) increased membrane expression of the astrocytic glutamine transporter SNAT3 and reduced membrane expression of the neuronal transporter SNAT1; b) reduced membrane expression of the neuronal GABA transporter GAT1 and increased membrane expression of the astrocytic GAT3 transporter; c) reduced membrane expression of the astrocytic glutamate transporters GLAST and GLT-1 and of the neuronal transporter EAAC1. Increasing extracellular cGMP normalizes membrane expression of SNAT3, GAT3, GAT1 and GLAST and extracellular glutamate, glutamine, GABA and citrulline hyperammonemic rats. Extracellular cGMP also modulates membrane expression of most transporters in control rats, reducing membrane expression of SNAT1, GLT-1 and EAAC1 and increasing that of GAT1 and GAT3. Modulation of SNAT3, SNAT1, GLT-1 and EAAC1 by extracellular cGMP would be mediated by inhibition of glycine receptors. These data suggest that, in pathological situations such as hyperammonemia, hepatic encephalopathy or Alzheimer's disease, reduced levels of extracellular cGMP contribute to alterations in membrane expression of glutamine, glutamate and GABA transporters, in the extracellular levels of glutamine, glutamate and GABA and in neurotransmission. This article is part of the issue entitled 'Special Issue on Neurotransmitter Transporters'.
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Affiliation(s)
- Andrea Cabrera-Pastor
- Laboratory of Neurobiology, Centro de Investigación Principe Felipe, Valencia, Spain; Fundacion Investigacion Hospital Clinico Valencia, Instituto de Investigacion Sanitaria INCLIVA, Valencia, Spain
| | - Yaiza M Arenas
- Laboratory of Neurobiology, Centro de Investigación Principe Felipe, Valencia, Spain
| | - Lucas Taoro-Gonzalez
- Laboratory of Neurobiology, Centro de Investigación Principe Felipe, Valencia, Spain
| | - Carmina Montoliu
- Fundacion Investigacion Hospital Clinico Valencia, Instituto de Investigacion Sanitaria INCLIVA, Valencia, Spain
| | - Vicente Felipo
- Laboratory of Neurobiology, Centro de Investigación Principe Felipe, Valencia, Spain.
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Lafora Disease: A Ubiquitination-Related Pathology. Cells 2018; 7:cells7080087. [PMID: 30050012 PMCID: PMC6116066 DOI: 10.3390/cells7080087] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Revised: 07/23/2018] [Accepted: 07/24/2018] [Indexed: 11/17/2022] Open
Abstract
Lafora disease (LD, OMIM254780) is a rare and fatal form of progressive myoclonus epilepsy (PME). Among PMEs, LD is unique because of the rapid neurological deterioration of the patients and the appearance in brain and peripheral tissues of insoluble glycogen-like (polyglucosan) inclusions, named Lafora bodies (LBs). LD is caused by mutations in the EPM2A gene, encoding the dual phosphatase laforin, or the EPM2B gene, encoding the E3-ubiquitin ligase malin. Laforin and malin form a functional complex that is involved in the regulation of glycogen synthesis. Thus, in the absence of a functional complex glycogen accumulates in LBs. In addition, it has been suggested that the laforin-malin complex participates in alternative physiological pathways, such as intracellular protein degradation, oxidative stress, and the endoplasmic reticulum unfolded protein response. In this work we review the possible cellular functions of laforin and malin with a special focus on their role in the ubiquitination of specific substrates. We also discuss here the pathological consequences of defects in laforin or malin functions, as well as the therapeutic strategies that are being explored for LD.
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Abstract
Drug transporter proteins are critical to the distribution of a wide range of endogenous compounds and xenobiotics such as hormones, bile acids, peptides, lipids, sugars, and drugs. There are two classes of drug transporters- the solute carrier (SLC) transporters and ATP-binding cassette (ABC) transporters -which predominantly differ in the energy source utilized to transport substrates across a membrane barrier. Despite their hydrophobic nature and residence in the membrane bilayer, drug transporters have dynamic structures and adopt many conformations during the translocation process. Whereas there is significant literature evidence for the substrate specificity and structure-function relationship for clinically relevant drug transporters proteins, there is less of an understanding in the regulatory mechanisms that contribute to the functional expression of these proteins. Post-translational modifications have been shown to modulate drug transporter functional expression via a wide range of molecular mechanisms. These modifications commonly occur through the addition of a functional group (e.g. phosphorylation), a small protein (e.g. ubiquitination), sugar chains (e.g. glycosylation), or lipids (e.g. palmitoylation) on solvent accessible amino acid residues. These covalent additions often occur as a result of a signaling cascade and may be reversible depending on the type of modification and the intended fate of the signaling event. Here, we review the significant role in which post-translational modifications contribute to the dynamic regulation and functional consequences of SLC and ABC drug transporters and highlight recent progress in understanding their roles in transporter structure, function, and regulation.
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Affiliation(s)
- Lindsay C Czuba
- Department of Pharmaceutical Sciences, University of Maryland, 20 Penn Street, Baltimore, MD 21201, USA
| | | | - Peter W Swaan
- Department of Pharmaceutical Sciences, University of Maryland, 20 Penn Street, Baltimore, MD 21201, USA.
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35
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Wang D, Wang X. GLT-1 mediates exercise-induced fatigue through modulation of glutamate and lactate in rats. Neuropathology 2018; 38:237-246. [DOI: 10.1111/neup.12465] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Revised: 02/26/2018] [Accepted: 02/26/2018] [Indexed: 12/31/2022]
Affiliation(s)
- Dongmei Wang
- Physical Education and Sports College; Beijing Normal University; Beijing China
- College of Sports Medicine and Rehabilitation; Taishan Medical University; Tai’an China
| | - Xingtong Wang
- College of Sports Medicine and Rehabilitation; Taishan Medical University; Tai’an China
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Dong W, Todd AC, Bröer A, Hulme SR, Bröer S, Billups B. PKC-Mediated Modulation of Astrocyte SNAT3 Glutamine Transporter Function at Synapses in Situ. Int J Mol Sci 2018; 19:ijms19040924. [PMID: 29561757 PMCID: PMC5979592 DOI: 10.3390/ijms19040924] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Revised: 03/07/2018] [Accepted: 03/15/2018] [Indexed: 01/13/2023] Open
Abstract
Astrocytes are glial cells that have an intimate physical and functional association with synapses in the brain. One of their main roles is to recycle the neurotransmitters glutamate and gamma-aminobutyric acid (GABA), as a component of the glutamate/GABA-glutamine cycle. They perform this function by sequestering neurotransmitters and releasing glutamine via the neutral amino acid transporter SNAT3. In this way, astrocytes regulate the availability of neurotransmitters and subsequently influence synaptic function. Since many plasma membrane transporters are regulated by protein kinase C (PKC), the aim of this study was to understand how PKC influences SNAT3 glutamine transport in astrocytes located immediately adjacent to synapses. We studied SNAT3 transport by whole-cell patch-clamping and fluorescence pH imaging of single astrocytes in acutely isolated brainstem slices, adjacent to the calyx of the Held synapse. Activation of SNAT3-mediated glutamine transport in these astrocytes was reduced to 77 ± 6% when PKC was activated with phorbol 12-myristate 13-acetate (PMA). This effect was very rapid (within ~20 min) and eliminated by application of bisindolylmaleimide I (Bis I) or 7-hydroxystaurosporine (UCN-01), suggesting that activation of conventional isoforms of PKC reduces SNAT3 function. In addition, cell surface biotinylation experiments in these brain slices show that the amount of SNAT3 in the plasma membrane is reduced by a comparable amount (to 68 ± 5%) upon activation of PKC. This indicates a role for PKC in dynamically controlling the trafficking of SNAT3 transporters in astrocytes in situ. These data demonstrate that PKC rapidly regulates the astrocytic glutamine release mechanism, which would influence the glutamine availability for adjacent synapses and control levels of neurotransmission.
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Affiliation(s)
- Wuxing Dong
- Eccles Institute of Neuroscience, The John Curtin School of Medical Research, The Australian National University, 131 Garran Road, Canberra ACT 2601, Australia.
| | - Alison C Todd
- Eccles Institute of Neuroscience, The John Curtin School of Medical Research, The Australian National University, 131 Garran Road, Canberra ACT 2601, Australia.
- Centre for Discovery Brain Sciences, School of Biomedical Sciences, University of Edinburgh, Edinburgh EH8 9XD, UK.
| | - Angelika Bröer
- Research School of Biology, The Australian National University, Linnaeus Way 134, Canberra ACT 2601, Australia.
| | - Sarah R Hulme
- Eccles Institute of Neuroscience, The John Curtin School of Medical Research, The Australian National University, 131 Garran Road, Canberra ACT 2601, Australia.
| | - Stefan Bröer
- Research School of Biology, The Australian National University, Linnaeus Way 134, Canberra ACT 2601, Australia.
| | - Brian Billups
- Eccles Institute of Neuroscience, The John Curtin School of Medical Research, The Australian National University, 131 Garran Road, Canberra ACT 2601, Australia.
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Activity dependent internalization of the glutamate transporter GLT-1 requires calcium entry through the NCX sodium/calcium exchanger. Neurochem Int 2018; 123:125-132. [PMID: 29574129 DOI: 10.1016/j.neuint.2018.03.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Revised: 03/20/2018] [Accepted: 03/20/2018] [Indexed: 12/13/2022]
Abstract
GLT-1 is the main glutamate transporter in the brain and its trafficking controls its availability at the cell surface, thereby shaping glutamatergic neurotransmission under physiological and pathological conditions. Extracellular glutamate is known to trigger ubiquitin-dependent GLT-1 internalization from the surface of the cell to the intracellular compartment, yet here we show that internalization also requires the participation of calcium ions. Consistent with previous studies, the addition of glutamate (1 mM) to mixed primary cultures (containing neurons and astrocytes) promotes GLT-1 internalization, an effect that was suppressed in the absence of extracellular Ca2+. The pathways of Ca2+ mobilization by astrocytes were analyzed in these mixed cultures using the genetically encoded calcium sensor GCaMP6f. A complex pattern of calcium entry was activated by glutamate, with a dramatic and rapid rise in the intracellular Ca2+ concentration partially driven by glutamate transporters, especially in the initial stages after exposure to glutamate. The Na+/Ca2+ exchanger (NCX) plays a dominant role in this Ca2+ mobilization and its blockade suppresses the glutamate induced internalization of GLT-1, both in astrocytes and in a more straightforward experimental system like HEK293 cells transiently transfected with GLT-1. This regulatory mechanism might be relevant to control the amount of GLT-1 transporter at the cell surface in conditions like ischemia or traumatic brain injury, where extracellular concentrations of glutamate are persistently elevated and they promote rapid Ca2+ mobilization.
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Weddell JC, Imoukhuede PI. Integrative meta-modeling identifies endocytic vesicles, late endosome and the nucleus as the cellular compartments primarily directing RTK signaling. Integr Biol (Camb) 2018; 9:464-484. [PMID: 28436498 DOI: 10.1039/c7ib00011a] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Recently, intracellular receptor signaling has been identified as a key component mediating cell responses for various receptor tyrosine kinases (RTKs). However, the extent each endocytic compartment (endocytic vesicle, early endosome, recycling endosome, late endosome, lysosome and nucleus) contributes to receptor signaling has not been quantified. Furthermore, our understanding of endocytosis and receptor signaling is complicated by cell- or receptor-specific endocytosis mechanisms. Therefore, towards understanding the differential endocytic compartment signaling roles, and identifying how to achieve signal transduction control for RTKs, we delineate how endocytosis regulates RTK signaling. We achieve this via a meta-analysis across eight RTKs, integrating computational modeling with experimentally derived cell (compartment volume, trafficking kinetics and pH) and ligand-receptor (ligand/receptor concentration and interaction kinetics) physiology. Our simulations predict the abundance of signaling from eight RTKs, identifying the following hierarchy in RTK signaling: PDGFRβ > IGFR1 > EGFR > PDGFRα > VEGFR1 > VEGFR2 > Tie2 > FGFR1. We find that endocytic vesicles are the primary cell signaling compartment; over 43% of total receptor signaling occurs within the endocytic vesicle compartment for these eight RTKs. Mechanistically, we found that high RTK signaling within endocytic vesicles may be attributed to their low volume (5.3 × 10-19 L) which facilitates an enriched ligand concentration (3.2 μM per ligand molecule within the endocytic vesicle). Under the analyzed physiological conditions, we identified extracellular ligand concentration as the most sensitive parameter to change; hence the most significant one to modify when regulating absolute compartment signaling. We also found that the late endosome and nucleus compartments are important contributors to receptor signaling, where 26% and 18%, respectively, of average receptor signaling occurs across the eight RTKs. Conversely, we found very low membrane-based receptor signaling, exhibiting <1% of the total receptor signaling for these eight RTKs. Moreover, we found that nuclear translocation, mechanistically, requires late endosomal transport; when we blocked receptor trafficking from late endosomes to the nucleus we found a 57% reduction in nuclear translocation. In summary, our research has elucidated the significance of endocytic vesicles, late endosomes and the nucleus in RTK signal propagation.
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Affiliation(s)
- Jared C Weddell
- Department of Bioengineering, University of Illinois at Urbana-Champaign, 1304 W Springfield Ave., 3233 Digital Computer Laboratory, Urbana, IL 61801, USA.
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39
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Cheng X, Zheng J, Li G, Göbel V, Zhang H. Degradation for better survival? Role of ubiquitination in epithelial morphogenesis. Biol Rev Camb Philos Soc 2018; 93:1438-1460. [PMID: 29493067 DOI: 10.1111/brv.12404] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Revised: 01/31/2018] [Accepted: 02/05/2018] [Indexed: 02/06/2023]
Abstract
As a prevalent post-translational modification, ubiquitination is essential for many developmental processes. Once covalently attached to the small and conserved polypeptide ubiquitin (Ub), a substrate protein can be directed to perform specific biological functions via its Ub-modified form. Three sequential catalytic reactions contribute to this process, among which E3 ligases serve to identify target substrates and promote the activated Ub to conjugate to substrate proteins. Ubiquitination has great plasticity, with diverse numbers, topologies and modifications of Ub chains conjugated at different substrate residues adding a layer of complexity that facilitates a huge range of cellular functions. Herein, we highlight key advances in the understanding of ubiquitination in epithelial morphogenesis, with an emphasis on the latest insights into its roles in cellular events involved in polarized epithelial tissue, including cell adhesion, asymmetric localization of polarity determinants and cytoskeletal organization. In addition, the physiological roles of ubiquitination are discussed for typical examples of epithelial morphogenesis, such as lung branching, vascular development and synaptic formation and plasticity. Our increased understanding of ubiquitination in epithelial morphogenesis may provide novel insights into the molecular mechanisms underlying epithelial regeneration and maintenance.
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Affiliation(s)
- Xiaoxiang Cheng
- Faculty of Health Sciences, University of Macau, Avenida da Universidade, Taipa, Macau 999078, China
| | - Jun Zheng
- Faculty of Health Sciences, University of Macau, Avenida da Universidade, Taipa, Macau 999078, China
| | - Gang Li
- Faculty of Health Sciences, University of Macau, Avenida da Universidade, Taipa, Macau 999078, China
| | - Verena Göbel
- Department of Pediatrics, Mucosal Immunology and Biology Research Center, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114,, U.S.A
| | - Hongjie Zhang
- Faculty of Health Sciences, University of Macau, Avenida da Universidade, Taipa, Macau 999078, China
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40
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Domith I, Socodato R, Portugal CC, Munis AF, Duarte-Silva AT, Paes-de-Carvalho R. Vitamin C modulates glutamate transport and NMDA receptor function in the retina. J Neurochem 2017; 144:408-420. [PMID: 29164598 DOI: 10.1111/jnc.14260] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Revised: 11/09/2017] [Accepted: 11/11/2017] [Indexed: 12/27/2022]
Abstract
Vitamin C (in the reduced form ascorbate or in the oxidized form dehydroascorbate) is implicated in signaling events throughout the central nervous system (CNS). In the retina, a high-affinity transport system for ascorbate has been described and glutamatergic signaling has been reported to control ascorbate release. Here, we investigated the modulatory role played by vitamin C upon glutamate uptake and N-methyl-d-aspartate (NMDA) receptor activation in cultured retinal cells or in intact retinal tissue using biochemical and imaging techniques. We show that both forms of vitamin C, ascorbate or dehydroascorbate, promote an accumulation of extracellular glutamate by a mechanism involving the inhibition of glutamate uptake. This inhibition correlates with the finding that ascorbate promotes a decrease in cell surface levels of the neuronal glutamate transporter excitatory amino acid transporter 3 in retinal neuronal cultures. Interestingly, vitamin C is prone to increase the activity of NMDA receptors but also promotes a decrease in glutamate-stimulated [3 H] MK801 binding and decreases cell membrane content of NMDA receptor glutamate ionotropic receptor subunit 1 (GluN1) subunits. Both compounds were also able to increase cAMP response element-binding protein phosphorylation in neuronal nuclei in a glutamate receptor and calcium/calmodulin kinase-dependent manner. Moreover, the effect of ascorbate is not blocked by sulfinpyrazone and then does not depend on its uptake by retinal cells. Overall, these data indicate a novel molecular and functional target for vitamin C impacting on glutamate signaling in retinal neurons.
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Affiliation(s)
- Ivan Domith
- Program of Neurosciences, Institute of Biology, Fluminense Federal University, Niterói, RJ, Brazil
| | - Renato Socodato
- Instituto de Investigação e Inovação em Saúde and Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Porto, Portugal
| | - Camila C Portugal
- Instituto de Investigação e Inovação em Saúde and Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Porto, Portugal
| | - Andressa F Munis
- Program of Neurosciences, Institute of Biology, Fluminense Federal University, Niterói, RJ, Brazil
| | - Aline T Duarte-Silva
- Program of Neurosciences, Institute of Biology, Fluminense Federal University, Niterói, RJ, Brazil
| | - Roberto Paes-de-Carvalho
- Program of Neurosciences, Institute of Biology, Fluminense Federal University, Niterói, RJ, Brazil.,Department of Neurobiology, Institute of Biology, Fluminense Federal University, Niterói, RJ, Brazil
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41
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Bai W, Zhou YG. Homeostasis of the Intraparenchymal-Blood Glutamate Concentration Gradient: Maintenance, Imbalance, and Regulation. Front Mol Neurosci 2017; 10:400. [PMID: 29259540 PMCID: PMC5723322 DOI: 10.3389/fnmol.2017.00400] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Accepted: 11/20/2017] [Indexed: 12/25/2022] Open
Abstract
It is widely accepted that glutamate is the most important excitatory neurotransmitter in the central nervous system (CNS). However, there is also a large amount of glutamate in the blood. Generally, the concentration gradient of glutamate between intraparenchymal and blood environments is stable. However, this gradient is dramatically disrupted under a variety of pathological conditions, resulting in an amplifying cascade that causes a series of pathological reactions in the CNS and peripheral organs. This eventually seriously worsens a patient’s prognosis. These two “isolated” systems are rarely considered as a whole even though they mutually influence each other. In this review, we summarize what is currently known regarding the maintenance, imbalance and regulatory mechanisms that control the intraparenchymal-blood glutamate concentration gradient, discuss the interrelationships between these systems and further explore their significance in clinical practice.
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Affiliation(s)
- Wei Bai
- Molecular Biology Center, State Key Laboratory of Trauma, Burn, and Combined Injury, Research Institute of Surgery and Daping Hospital, Third Military Medical University, Chongqing, China
| | - Yuan-Guo Zhou
- Molecular Biology Center, State Key Laboratory of Trauma, Burn, and Combined Injury, Research Institute of Surgery and Daping Hospital, Third Military Medical University, Chongqing, China
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42
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Sonic hedgehog induces GLT-1 degradation via PKC delta to suppress its transporter activities. Neuroscience 2017; 365:217-225. [PMID: 28993237 DOI: 10.1016/j.neuroscience.2017.09.051] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Revised: 09/25/2017] [Accepted: 09/26/2017] [Indexed: 01/20/2023]
Abstract
GLT-1 is mainly expressed in astrocytes and has a crucial role in glutamate uptake. Sonic hedgehog (SHH) can inhibit glutamate uptake and its pathway is activated in many brain diseases related with glutamate excitotoxicity. However, whether SHH regulates GLT-1 to affect glutamate uptake is not clear. Here, we use pharmacological and genetic methods to show that SHH induces GLT-1 degradation in astrocytes in a manner that is dependent on PKC delta (PKCδ) to regulate GLT-1 activities. GLT-1 protein levels are reduced as early as 2 hs in astrocytes after incubation with SHH, whereas its mRNA levels are not changed. This reduction is recapitulated when astrocytes are transfected with SmoA1, a constitutively active form of Smoothened (Smo), the mediator of SHH pathway. The reduction of GLT-1 and inhibition of aspartate current are not observed when staurosporine (STP) and BisindolylmaleimideII (BisII), agents known as PKC inhibitors, are present. Further, when PKCδ is knocked down in astrocytes, SHH cannot reduce GLT-1 protein levels. Therefore, SHH induces degradation of GLT-1 through PKCδ to regulate its activities.
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43
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Regulation of glutamate transporter 1 (GLT-1) gene expression by cocaine self-administration and withdrawal. Neuropharmacology 2017; 128:1-10. [PMID: 28919080 DOI: 10.1016/j.neuropharm.2017.09.019] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2017] [Revised: 09/06/2017] [Accepted: 09/11/2017] [Indexed: 12/24/2022]
Abstract
Downregulation of the astroglial glutamate transporter GLT-1 is observed in the nucleus accumbens (NAc) following administration of multiple drugs of abuse. The decrease in GLT-1 protein expression following cocaine self-administration is dependent on both the amount of cocaine self-administered and the length of withdrawal, with longer access to cocaine and longer withdrawal periods leading to greater decreases in GLT-1 protein. However, the mechanism(s) by which cocaine downregulates GLT-1 protein remains unknown. We used qRT-PCR to examine gene expression of GLT-1 splice isoforms (GLT-1A, GLT-1B) in the NAc, prelimbic cortex (PL) and basolateral amygdala (BLA) of rats, following two widely used models of cocaine self-administration: short-access (ShA) self-administration, and the long-access (LgA) self-administration/incubation model. While downregulation of GLT-1 protein is observed following ShA cocaine self-administration and extinction, this model did not lead to a change in GLT-1A or GLT-1B gene expression in any brain region examined. Forced abstinence following ShA cocaine self-administration also was without effect. In contrast, LgA cocaine self-administration and prolonged abstinence significantly decreased GLT-1A gene expression in the NAc and BLA, and significantly decreased GLT-1B gene expression in the PL. No change was observed in NAc GLT-1A gene expression one day after LgA cocaine self-administration, indicating withdrawal-induced decreases in GLT-1A mRNA. In addition, LgA cocaine self-administration and withdrawal induced hypermethylation of the GLT-1 gene in the NAc. These results indicate that a decrease in NAc GLT-1 mRNA is only observed after extended access to cocaine combined with protracted abstinence, and that epigenetic mechanisms likely contribute to this effect.
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Spencer S, Kalivas PW. Glutamate Transport: A New Bench to Bedside Mechanism for Treating Drug Abuse. Int J Neuropsychopharmacol 2017; 20:797-812. [PMID: 28605494 PMCID: PMC5632313 DOI: 10.1093/ijnp/pyx050] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Accepted: 06/09/2017] [Indexed: 02/06/2023] Open
Abstract
Drug addiction has often been described as a "hijacking" of the brain circuits involved in learning and memory. Glutamate is the principal excitatory neurotransmitter in the brain, and its contribution to synaptic plasticity and learning processes is well established in animal models. Likewise, over the past 20 years the addiction field has ascribed a critical role for glutamatergic transmission in the development of addiction. Chronic drug use produces enduring neuroadaptations in corticostriatal projections that are believed to contribute to a maladaptive deficit in inhibitory control over behavior. Much of this research focuses on the role played by ionotropic glutamate receptors directly involved in long-term potentiation and depression or metabotropic receptors indirectly modulating synaptic plasticity. Importantly, the balance between glutamate release and clearance tightly regulates the patterned activation of these glutamate receptors, emphasizing an important role for glutamate transporters in maintaining extracellular glutamate levels. Five excitatory amino acid transporters participate in active glutamate reuptake. Recent evidence suggests that these glutamate transporters can be modulated by chronic drug use at a variety of levels. In this review, we synopsize the evidence and mechanisms associated with drug-induced dysregulation of glutamate transport. We then summarize the preclinical and clinical data suggesting that glutamate transporters offer an effective target for the treatment of drug addiction. In particular, we focus on the role that altered glutamate transporters have in causing drug cues and contexts to develop an intrusive quality that guides maladaptive drug seeking behaviors.
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Affiliation(s)
- Sade Spencer
- Department of Neurosciences, Medical University of South Carolina, Charleston, South Carolina.,Correspondence: Sade Spencer, PhD, Medical University of South Carolina, 173 Ashley Avenue, BSB, 403- MSC 510, Charleston, SC 29425 ()
| | - Peter W Kalivas
- Department of Neurosciences, Medical University of South Carolina, Charleston, South Carolina.
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Xu D, Zhang J, Zhang Q, Fan Y, Liu C, You G. PKC/Nedd4-2 Signaling Pathway Regulates the Cell Surface Expression of Drug Transporter hOAT1. Drug Metab Dispos 2017; 45:887-895. [PMID: 28572241 DOI: 10.1124/dmd.117.075861] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Accepted: 05/26/2017] [Indexed: 12/23/2022] Open
Abstract
Human organic anion transporter-1 (hOAT1) regulates the absorption, distribution, and excretion of a wide range of clinically important drugs. Our previous work demonstrated that hOAT1 is a dynamic membrane transporter, constitutively internalizing from and recycling back to the cell plasma membrane. Short-term activation (<30 minutes) of protein kinase C (PKC) promotes the attachment of a lysine 48-linked polyubiquitin chain to hOAT1, a process catalyzed by ubiquitin ligase neural precursor cell expressed developmentally down-regulated 4-2 (Nedd4-2). The ubiquitination of hOAT1 then triggers an accelerated endocytosis of the transporter from plasma membrane, which results in reduced hOAT1 expression at the cell surface and decreased hOAT1 transport activity. In the present study, we investigated the long-term effect of PKC on hOAT1. We showed that long-term activation (>2 hours) of PKC significantly enhanced hOAT1 degradation, and such action was partially blocked by ubiquitin mutant Ub-K48R, which has its lysine (K) 48 mutated to arginine (R) and is incapable of forming a K48-linked polyubiquitin chain. The ubiquitin ligase Nedd4-2 was also found to augment hOAT1 degradation. These results suggest that PKC-regulated and Nedd4-2-catalyzed attachment of a lysine 48-linked polyubiquitin chain to hOAT1 is important for hOAT1 stability. We further showed through coimmunoprecipitation experiments that there was a direct association between hOAT1 and Nedd4-2, and such interaction was weakened when the WW3 and WW4 domains of the ligase were mutated. Mutating WW3 and WW4 domains of the ligase also impaired its ability to ubiquitinate hOAT1. Therefore, WW3 and WW4 domains of Nedd4-2 are critical for its association with and modulation of the transporter.
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Affiliation(s)
- Da Xu
- Department of Pharmaceutics, Rutgers University, Piscataway, New Jersey
| | - Jinghui Zhang
- Department of Pharmaceutics, Rutgers University, Piscataway, New Jersey
| | - Qiang Zhang
- Department of Pharmaceutics, Rutgers University, Piscataway, New Jersey
| | - Yunzhou Fan
- Department of Pharmaceutics, Rutgers University, Piscataway, New Jersey
| | - Chenchang Liu
- Department of Pharmaceutics, Rutgers University, Piscataway, New Jersey
| | - Guofeng You
- Department of Pharmaceutics, Rutgers University, Piscataway, New Jersey
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46
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Amyloid-beta peptide decreases expression and function of glutamate transporters in nervous system cells. Int J Biochem Cell Biol 2017; 85:75-84. [DOI: 10.1016/j.biocel.2017.01.017] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Revised: 12/26/2016] [Accepted: 01/29/2017] [Indexed: 12/26/2022]
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47
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Huang HT, Liao CK, Chiu WT, Tzeng SF. Ligands of peroxisome proliferator-activated receptor-alpha promote glutamate transporter-1 endocytosis in astrocytes. Int J Biochem Cell Biol 2017; 86:42-53. [PMID: 28323206 DOI: 10.1016/j.biocel.2017.03.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2016] [Revised: 02/14/2017] [Accepted: 03/14/2017] [Indexed: 02/05/2023]
Abstract
Astrocytes, a stellate-shape glial population in the central nervous system (CNS), maintain glutamate homeostasis in adult CNS by undergoing glutamate uptake at the synapse through their glutamate transporter-1 (GLT-1). Peroxisome proliferator-activated receptor-α (PPARα) can be activated by endogenous saturated fatty acids to regulate astrocytic lipid metabolism and functions. However, it is unclear if PPARα can exert the regulatory action on GLT-1 expression in astrocytes. This study showed that treatment with palmitic acid (PA) and the other two PPARα agonists (GW 7647 and WY 14,643) caused no change in the morphology of astrocytes, whereas membranous GLT-1 protein levels in astrocytes were significantly decreased by PA and PPARα agonists. Through lentivirus-mediated overexpression of GLT-1 tagged with red fluorescent protein (GLT-1-RFP), we also observed that GLT-1-RFP puncta in the processes of astrocytes were inhibited by the PPARα agonists. This reduction was prevented by the addition of the PPARα antagonist, GW6471. GLT-1-RFP was co-localized to the early endosome marker-EEA1 in astrocytes treated with the PPARα agonists. Moreover, PPARα-induced inhibition in membranous GLT-1 expression was abolished by the addition of dynamin inhibitor (dynasore). Furthermore, the co-treatment of astrocytes with PPARα agonists and dynasore, or with PPARα agonists and protein kinase C (PKC) inhibitor bis-indolylmaleimide 1 (BIS1), prevented the endocytosis of GLT-1-RFP. Based on the results, we conclude that the PPARα agonists increased GLT-1 endocytosis in astrocytes possibly through the PKC signaling pathway. In addition, our findings provide important information of PPARα involvement in the downregulation of astrocytic glutamate uptake via the promoted GLT-1 endocytosis.
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Affiliation(s)
- Hui-Ting Huang
- Institute of Life Sciences, College of Bioscience and Biotechnology, National Cheng Kung University, Tainan, Taiwan
| | - Chih-Kai Liao
- Institute of Life Sciences, College of Bioscience and Biotechnology, National Cheng Kung University, Tainan, Taiwan
| | - Wen-Tai Chiu
- Department of Biomedical Engineering, National Cheng Kung University, Tainan, Taiwan
| | - Shun-Fen Tzeng
- Institute of Life Sciences, College of Bioscience and Biotechnology, National Cheng Kung University, Tainan, Taiwan.
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48
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Rapamycin upregulates glutamate transporter and IL-6 expression in astrocytes in a mouse model of Parkinson's disease. Cell Death Dis 2017; 8:e2611. [PMID: 28182002 PMCID: PMC5386462 DOI: 10.1038/cddis.2016.491] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Revised: 11/22/2016] [Accepted: 12/15/2016] [Indexed: 02/06/2023]
Abstract
Rapamycin protects mice against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced loss of dopaminergic neurons, which is an established model for Parkinson's disease. We demonstrated that rapamycin preserves astrocytic expression of glutamate transporters and glutamate reuptake. The protective effect was also observed in astrocyte cultures, indicating that rapamycin acts directly on astrocytes. In the MPTP model, rapamycin caused reduced expression of the E3 ubiquitin ligase Nedd4-2 (neuronal precursor cell expressed developmentally downregulated 4-2) and reduced colocalization of glutamate transporters with ubiquitin. Rapamycin increased interleukin-6 (IL-6) expression, which was associated with reduced expression of inflammatory cytokines, indicating anti-inflammatory properties of IL-6 in the MPTP model. NF-κB was shown to be a key mediator for rapamycin, whereas Janus kinase 2, signal transducer and activator of transcription 3, phosphoinositide 3-kinase, and Akt partially mediated rapamycin effects in astrocytes. These results demonstrate for the first time in a Parkinson's disease animal model that the neuroprotective effects of rapamycin are associated with glial and anti-inflammatory effects.
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Regulation of glutamate transporter trafficking by Nedd4-2 in a Parkinson's disease model. Cell Death Dis 2017; 8:e2574. [PMID: 28151476 PMCID: PMC5386455 DOI: 10.1038/cddis.2016.454] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Revised: 11/05/2016] [Accepted: 12/07/2016] [Indexed: 01/06/2023]
Abstract
Glutamate transporters play a key role in glutamate clearance and protect the central nervous system from glutamate excitotoxicity. Dysfunctional glutamate transporters contribute to the pathogenesis of Parkinson's disease (PD); however, the mechanisms that underlie the regulation of glutamate transporters in PD are still not well characterized. Here we report that Nedd4-2 mediates the ubiquitination of glutamate transporters in 1-methyl-4- phenylpyridinium (MPP+)-treated astrocytes and in the midbrain of 1-methyl-4-phenyl-1,2,3,6- tetrahydropyridine (MPTP)-constructed PD model mice. Nedd4-2-mediated ubiquitination induces abnormal glutamate transporter trafficking between the membrane and cytoplasm and consequently decreases the expression and function of glutamate transporters in the membrane. Conversely, Nedd4-2 knockdown decreases glutamate transporter ubiquitination, promotes glutamate uptake and increases glutamate transporter expression in vitro and in vivo. We report for the first time that Nedd4-2 knockdown ameliorates movement disorders in PD mice and increases tyrosine hydroxylase expression in the midbrain and striatum of PD mice; Nedd4-2 knockdown also attenuates astrogliosis and reactive microgliosis in the MPTP model that may be associated with glutamate excitotoxicity. Furthermore, the SGK/PKC pathway is regulated downstream of Nedd4-2 in MPTP-treated mice. These findings indicate that Nedd4-2 may serve as a potential therapeutic target for the treatment of PD.
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Zafra F, Ibáñez I, Giménez C. Glutamate transporters: The arrestin connection. Oncotarget 2017; 8:5664-5665. [PMID: 28086208 PMCID: PMC5351570 DOI: 10.18632/oncotarget.13999] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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