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Wang X, Yue M, Cheung JPY, Cheung PWH, Fan Y, Wu M, Wang X, Zhao S, Khanshour AM, Rios JJ, Chen Z, Wang X, Tu W, Chan D, Yuan Q, Qin D, Qiu G, Wu Z, Zhang TJ, Ikegawa S, Wu N, Wise CA, Hu Y, Luk KDK, Song YQ, Gao B. Impaired glycine neurotransmission causes adolescent idiopathic scoliosis. J Clin Invest 2024; 134:e168783. [PMID: 37962965 PMCID: PMC10786698 DOI: 10.1172/jci168783] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Accepted: 11/08/2023] [Indexed: 11/16/2023] Open
Abstract
Adolescent idiopathic scoliosis (AIS) is the most common form of spinal deformity, affecting millions of adolescents worldwide, but it lacks a defined theory of etiopathogenesis. Because of this, treatment of AIS is limited to bracing and/or invasive surgery after onset. Preonset diagnosis or preventive treatment remains unavailable. Here, we performed a genetic analysis of a large multicenter AIS cohort and identified disease-causing and predisposing variants of SLC6A9 in multigeneration families, trios, and sporadic patients. Variants of SLC6A9, which encodes glycine transporter 1 (GLYT1), reduced glycine-uptake activity in cells, leading to increased extracellular glycine levels and aberrant glycinergic neurotransmission. Slc6a9 mutant zebrafish exhibited discoordination of spinal neural activities and pronounced lateral spinal curvature, a phenotype resembling human patients. The penetrance and severity of curvature were sensitive to the dosage of functional glyt1. Administration of a glycine receptor antagonist or a clinically used glycine neutralizer (sodium benzoate) partially rescued the phenotype. Our results indicate a neuropathic origin for "idiopathic" scoliosis, involving the dysfunction of synaptic neurotransmission and central pattern generators (CPGs), potentially a common cause of AIS. Our work further suggests avenues for early diagnosis and intervention of AIS in preadolescents.
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Affiliation(s)
- Xiaolu Wang
- Department of Orthopaedics and Traumatology, School of Clinical Medicine, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong, China
- School of Biomedical Sciences, Faculty of Medicine, Chinese University of Hong Kong, Shatin, Hong Kong, China
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong, China
| | - Ming Yue
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong, China
| | - Jason Pui Yin Cheung
- Department of Orthopaedics and Traumatology, School of Clinical Medicine, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong, China
- Department of Orthopaedics and Traumatology, University of Hong Kong–Shenzhen Hospital, Shenzhen, China
| | - Prudence Wing Hang Cheung
- Department of Orthopaedics and Traumatology, School of Clinical Medicine, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong, China
| | - Yanhui Fan
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong, China
| | - Meicheng Wu
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong, China
| | - Xiaojun Wang
- Department of Orthopaedics and Traumatology, School of Clinical Medicine, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong, China
| | - Sen Zhao
- Department of Orthopaedic Surgery, Department of Medical Research Center, Key Laboratory of Big Data for Spinal Deformities, State Key Laboratory of Complex Severe and Rare Diseases, Beijing Key Laboratory for Genetic Research of Skeletal Deformity, Peking Union Medical College Hospital (PUMCH) and Chinese Academy of Medical Sciences, Beijing, China
| | - Anas M. Khanshour
- Center for Pediatric Bone Biology and Translational Research, Scottish Rite for Children (SRC), Dallas, Texas, USA
| | - Jonathan J. Rios
- Center for Pediatric Bone Biology and Translational Research, Scottish Rite for Children (SRC), Dallas, Texas, USA
- Eugene McDermott Center for Human Growth and Development, Departments of Orthopaedic Surgery and Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Zheyi Chen
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong, China
| | - Xiwei Wang
- Department of Paediatrics and Adolescent Medicine, School of Clinical Medicine, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong, China
| | - Wenwei Tu
- Department of Paediatrics and Adolescent Medicine, School of Clinical Medicine, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong, China
| | - Danny Chan
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong, China
| | - Qiuju Yuan
- Centre for Regenerative Medicine and Health, Hong Kong Institute of Science & Innovation, Chinese Academy of Sciences, Tai Po, Hong Kong, China
| | - Dajiang Qin
- Centre for Regenerative Medicine and Health, Hong Kong Institute of Science & Innovation, Chinese Academy of Sciences, Tai Po, Hong Kong, China
| | - Guixing Qiu
- Department of Orthopaedic Surgery, Department of Medical Research Center, Key Laboratory of Big Data for Spinal Deformities, State Key Laboratory of Complex Severe and Rare Diseases, Beijing Key Laboratory for Genetic Research of Skeletal Deformity, Peking Union Medical College Hospital (PUMCH) and Chinese Academy of Medical Sciences, Beijing, China
| | - Zhihong Wu
- Department of Orthopaedic Surgery, Department of Medical Research Center, Key Laboratory of Big Data for Spinal Deformities, State Key Laboratory of Complex Severe and Rare Diseases, Beijing Key Laboratory for Genetic Research of Skeletal Deformity, Peking Union Medical College Hospital (PUMCH) and Chinese Academy of Medical Sciences, Beijing, China
| | - Terry Jianguo Zhang
- Department of Orthopaedic Surgery, Department of Medical Research Center, Key Laboratory of Big Data for Spinal Deformities, State Key Laboratory of Complex Severe and Rare Diseases, Beijing Key Laboratory for Genetic Research of Skeletal Deformity, Peking Union Medical College Hospital (PUMCH) and Chinese Academy of Medical Sciences, Beijing, China
| | - Shiro Ikegawa
- Laboratory of Bone and Joint Diseases, RIKEN Center for Integrative Medical Sciences, Tokyo, Japan
| | - Nan Wu
- Department of Orthopaedic Surgery, Department of Medical Research Center, Key Laboratory of Big Data for Spinal Deformities, State Key Laboratory of Complex Severe and Rare Diseases, Beijing Key Laboratory for Genetic Research of Skeletal Deformity, Peking Union Medical College Hospital (PUMCH) and Chinese Academy of Medical Sciences, Beijing, China
| | - Carol A. Wise
- Center for Pediatric Bone Biology and Translational Research, Scottish Rite for Children (SRC), Dallas, Texas, USA
- Eugene McDermott Center for Human Growth and Development, Departments of Orthopaedic Surgery and Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Yong Hu
- Department of Orthopaedics and Traumatology, School of Clinical Medicine, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong, China
- Department of Orthopaedics and Traumatology, University of Hong Kong–Shenzhen Hospital, Shenzhen, China
| | - Keith Dip Kei Luk
- Department of Orthopaedics and Traumatology, School of Clinical Medicine, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong, China
| | - You-Qiang Song
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong, China
- Department of Medicine, University of Hong Kong–Shenzhen Hospital, Shenzhen, China
- State Key Laboratory of Brain and Cognitive Sciences, University of Hong Kong, Pokfulam, Hong Kong, China
| | - Bo Gao
- School of Biomedical Sciences, Faculty of Medicine, Chinese University of Hong Kong, Shatin, Hong Kong, China
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong, China
- Department of Orthopaedics and Traumatology, University of Hong Kong–Shenzhen Hospital, Shenzhen, China
- Centre for Translational Stem Cell Biology, Tai Po, Hong Kong, China
- Key Laboratory of Regenerative Medicine, Ministry of Education, School of Biomedical Sciences, Faculty of Medicine, Chinese University of Hong Kong, Shatin, Hong Kong, China
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2
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Morita A, Satouh Y, Kosako H, Kobayashi H, Iwase A, Sato K. Clathrin-mediated endocytosis is essential for the selective degradation of maternal membrane proteins and preimplantation development. Development 2021; 148:270925. [PMID: 34269385 DOI: 10.1242/dev.199461] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Accepted: 06/23/2021] [Indexed: 11/20/2022]
Abstract
Fertilization triggers significant cellular remodeling through the oocyte-to-embryo transition. In this transition, the ubiquitin-proteasome system and autophagy are essential for the degradation of maternal components; however, the significance of degradation of cell surface components remains unknown. In this study, we show that multiple maternal plasma membrane proteins, such as the glycine transporter GlyT1a, are selectively internalized from the plasma membrane to endosomes in mouse embryos by the late two-cell stage and then transported to lysosomes for degradation at the later stages. During this process, large amounts of ubiquitylated proteins accumulated on endosomes. Furthermore, the degradation of GlyT1a with mutations in potential ubiquitylation sites was delayed, suggesting that ubiquitylation may be involved in GlyT1a degradation. The clathrin inhibitor blocked GlyT1a internalization. Strikingly, the protein kinase C (PKC) activator triggered the heterochronic internalization of GlyT1a; the PKC inhibitor markedly blocked GlyT1a endocytosis. Lastly, clathrin inhibition completely blocked embryogenesis at the two-cell stage and inhibited cell division after the four-cell stage. These findings demonstrate that PKC-dependent clathrin-mediated endocytosis is essential for the selective degradation of maternal membrane proteins during oocyte-to-embryo transition and early embryogenesis.
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Affiliation(s)
- Akihito Morita
- Laboratory of Molecular Traffic, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, 371-8512, Japan.,Department of Obstetrics and Gynecology, Gunma University Graduate School of Medicine, Maebashi, 371-8511, Japan
| | - Yuhkoh Satouh
- Laboratory of Molecular Traffic, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, 371-8512, Japan
| | - Hidetaka Kosako
- Division of Cell Signaling, Fujii Memorial Institute of Medical Sciences, Institute of Advanced Medical Sciences, Tokushima University, Tokushima, 770-8503, Japan
| | - Hisae Kobayashi
- Laboratory of Molecular Traffic, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, 371-8512, Japan
| | - Akira Iwase
- Department of Obstetrics and Gynecology, Gunma University Graduate School of Medicine, Maebashi, 371-8511, Japan
| | - Ken Sato
- Laboratory of Molecular Traffic, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, 371-8512, Japan
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3
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Jiménez E, Piniella D, Giménez C, Zafra F. Regulation of the Glycine Transporter GLYT1 by microRNAs. Neurochem Res 2021; 47:138-147. [PMID: 33484385 DOI: 10.1007/s11064-021-03228-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 12/18/2020] [Accepted: 01/02/2021] [Indexed: 12/28/2022]
Abstract
The glycine transporter GLYT1 participates in inhibitory and excitatory neurotransmission by controlling the reuptake of this neuroactive substance from synapses. Over the past few years, microRNAs have emerged as potent negative regulators of gene expression. In this report, we investigate the possible regulation of GLYT1 by microRNAs. TargetScan software predicted the existence of multiple targets for microRNAs within the 3' UTR of the human GLYT1 (miR-7, miR-30, miR-96, miR-137 and miR-141), and as they are all conserved among mammalian orthologues, their effects on GLYT1 expression were determined experimentally. Dual reporter bioluminescent assays showed that only miR-96 and miR-137 down-regulated expression of the Renilla reporter fused to the 3' UTR of GLYT1. Mutations introduced into the target sequences blocked this inhibitory effect. Consistently, these two microRNAs downregulated the uptake of [3H]glycine into glial C6 cells, a cell line where GLYT1 is the main carrier for glycine. Moreover, the expression of endogenous GLYT1 in primary mixed cultures from rat spinal cord was decreased upon lentiviral expression of miR-96 and miR-137. Although the bulk of GLYT1 is glial, it is abundantly expressed in glycinergic neurons of the retina and in smaller amounts in glutamatergic neurons though the brain. Since miR-96 in the retina is strongly downregulated by light exposure, when rats were maintained in darkness for a few hours we observed a concomitant increase of GLYT1 expression, suggesting that at least miR-96 might be an important negative regulator of GLYT1 under physiological conditions.
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Affiliation(s)
- Esperanza Jiménez
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, C / Nicolás Cabrera 1, Madrid, 28049, 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, C / Nicolás Cabrera 1, Madrid, 28049, Spain.,IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
| | - Cecilio Giménez
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, C / Nicolás Cabrera 1, Madrid, 28049, Spain.,IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
| | - Francisco Zafra
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, C / Nicolás Cabrera 1, Madrid, 28049, Spain. .,IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain.
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4
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Marques BL, Oliveira-Lima OC, Carvalho GA, de Almeida Chiarelli R, Ribeiro RI, Parreira RC, da Madeira Freitas EM, Resende RR, Klempin F, Ulrich H, Gomez RS, Pinto MCX. Neurobiology of glycine transporters: From molecules to behavior. Neurosci Biobehav Rev 2020; 118:97-110. [PMID: 32712279 DOI: 10.1016/j.neubiorev.2020.07.025] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 07/07/2020] [Accepted: 07/17/2020] [Indexed: 12/16/2022]
Abstract
Glycine transporters (GlyTs) are Na+/Cl--dependent neurotransmitter transporters, responsible for l-glycine uptake into the central nervous system. GlyTs are members of the solute carrier family 6 (SLC6) and comprise glycine transporter type 1 (SLC6A9; GlyT1) and glycine transporter type 2 (SLC6A5; Glyt2). GlyT1 and GlyT2 are expressed on both astrocytes and neurons, but their expression pattern in brain tissue is foremost related to neurotransmission. GlyT2 is markedly expressed in brainstem, spinal cord and cerebellum, where it is responsible for glycine uptake into glycinergic and GABAergic terminals. GlyT1 is abundant in neocortex, thalamus and hippocampus, where it is expressed in astrocytes, and involved in glutamatergic neurotransmission. Consequently, inhibition of GlyT1 transporters can modulate glutamatergic neurotransmission through NMDA receptors, suggesting an alternative therapeutic strategy. In this review, we focus on recent progress in the understanding of GlyTs role in brain function and in various diseases, such as epilepsy, hyperekplexia, neuropathic pain, drug addiction, schizophrenia and stroke, as well as in neurodegenerative disorders.
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Affiliation(s)
- Bruno Lemes Marques
- Laboratório de Neuroquímica e Neurofarmacologia - Neurolab, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil
| | - Onésia Cristina Oliveira-Lima
- Laboratório de Neuroquímica e Neurofarmacologia - Neurolab, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil
| | - Gustavo Almeida Carvalho
- Laboratório de Neuroquímica e Neurofarmacologia - Neurolab, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil
| | - Raphaela de Almeida Chiarelli
- Laboratório de Neuroquímica e Neurofarmacologia - Neurolab, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil
| | - Raul Izidoro Ribeiro
- Laboratório de Neuroquímica e Neurofarmacologia - Neurolab, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil
| | - Ricardo Cambraia Parreira
- Laboratório de Neuroquímica e Neurofarmacologia - Neurolab, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil
| | - Elis Marra da Madeira Freitas
- Laboratório de Neuroquímica e Neurofarmacologia - Neurolab, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil
| | - Rodrigo Ribeiro Resende
- Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | | | - Henning Ulrich
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, SP, Brazil
| | - Renato Santiago Gomez
- Departamento de Cirurgia, Faculdade de Medicina, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Mauro Cunha Xavier Pinto
- Laboratório de Neuroquímica e Neurofarmacologia - Neurolab, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil.
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5
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Zafra F, Ibáñez I, Bartolomé-Martín D, Piniella D, Arribas-Blázquez M, Giménez C. Glycine Transporters and Its Coupling with NMDA Receptors. ADVANCES IN NEUROBIOLOGY 2018; 16:55-83. [PMID: 28828606 DOI: 10.1007/978-3-319-55769-4_4] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Glycine plays two roles in neurotransmission. In caudal areas like the spinal cord and the brainstem, it acts as an inhibitory neurotransmitter, but in all regions of the CNS, it also works as a co-agonist with L-glutamate at N-methyl-D-aspartate receptors (NMDARs). The glycine fluxes in the CNS are regulated by two specific transporters for glycine, GlyT1 and GlyT2, perhaps with the cooperation of diverse neutral amino acid transporters like Asc-1 or SNAT5/SN2. While GlyT2 and Asc-1 are neuronal proteins, GlyT1 and SNAT5 are mainly astrocytic, although neuronal forms of GlyT1 also exist. GlyT1 has attracted considerable interest from the medical community and the pharmaceutical industry since compelling evidence indicates a clear association with the functioning of NMDARs, whose activity is decreased in various psychiatric illnesses. By controlling extracellular glycine, transporter inhibitors might potentiate the activity of NMDARs without activating excitotoxic processes. Physiologically, GlyT1 is a central actor in the cross talk between glutamatergic, glycinergic, dopaminergic, and probably other neurotransmitter systems. Many of these relationships begin to be unraveled by studies performed in recent years using genetic and pharmacological models. These studies are also clarifying the interactions between glycine, glycine transporters, and other co-agonists of the glycine site of NMDARs like D-serine. These findings are also relevant to understand the pathophysiology of devastating diseases like schizophrenia, depression, anxiety, epilepsy, stroke, and chronic pain.
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Affiliation(s)
- Francisco Zafra
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, C / Nicolás Cabrera, 1, 28049, Madrid, Spain. .,Centro de Investigación Biomédica en Red de Enfermedades Raras and 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, C / Nicolás Cabrera, 1, 28049, Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras and IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
| | - David Bartolomé-Martín
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, C / Nicolás Cabrera, 1, 28049, Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras and 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, C / Nicolás Cabrera, 1, 28049, Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras and IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
| | - Marina Arribas-Blázquez
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, C / Nicolás Cabrera, 1, 28049, Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras and IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
| | - Cecilio Giménez
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, C / Nicolás Cabrera, 1, 28049, Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras and IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
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6
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Barrera SP, Castrejon-Tellez V, Trinidad M, Robles-Escajeda E, Vargas-Medrano J, Varela-Ramirez A, Miranda M. PKC-Dependent GlyT1 Ubiquitination Occurs Independent of Phosphorylation: Inespecificity in Lysine Selection for Ubiquitination. PLoS One 2015; 10:e0138897. [PMID: 26418248 PMCID: PMC4587969 DOI: 10.1371/journal.pone.0138897] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Accepted: 09/06/2015] [Indexed: 01/08/2023] Open
Abstract
Neurotransmitter transporter ubiquitination is emerging as the main mechanism for endocytosis and sorting of cargo into lysosomes. In this study, we demonstrate PKC-dependent ubiquitination of three different isoforms of the glycine transporter 1 (GlyT1). Incubation of cells expressing transporter with the PKC activator phorbol ester induced a dramatic, time-dependent increase in GlyT1 ubiquitination, followed by accumulation of GlyT1 in EEA1 positive early endosomes. This occurred via a mechanism that was abolished by inhibition of PKC. GlyT1 endocytosis was confirmed in both retinal sections and primary cultures of mouse amacrine neurons. Replacement of only all lysines in the N-and C-termini to arginines prevented ubiquitination and endocytosis, displaying redundancy in the mechanism of ubiquitination. Interestingly, a 40–50% reduction in glycine uptake was detected in phorbol-ester stimulated cells expressing the WT-GlyT1, whereas no significant change was for the mutant protein, demonstrating that endocytosis participates in the reduction of uptake. Consistent with previous findings for the dopamine transporter DAT, ubiquitination of GlyT1 tails functions as sorting signal to deliver transporter into the lysosome and removal of ubiquitination sites dramatically attenuated the rate of GlyT1 degradation. Finally, we showed for the first time that PKC-dependent GlyT1 phosphorylation was not affected by removal of ubiquitination sites, suggesting separate PKC-dependent signaling events for these posttranslational modifications.
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Affiliation(s)
- Susana P. Barrera
- Department of Biological Sciences and Border Biomedical Research Center, University of Texas at El Paso, El Paso, TX, 79968, United States of America
| | - Vicente Castrejon-Tellez
- Department of Biological Sciences and Border Biomedical Research Center, University of Texas at El Paso, El Paso, TX, 79968, United States of America
| | - Margarita Trinidad
- Department of Biological Sciences and Border Biomedical Research Center, University of Texas at El Paso, El Paso, TX, 79968, United States of America
| | - Elisa Robles-Escajeda
- Department of Biological Sciences and Border Biomedical Research Center, University of Texas at El Paso, El Paso, TX, 79968, United States of America
| | - Javier Vargas-Medrano
- Department of Biological Sciences and Border Biomedical Research Center, University of Texas at El Paso, El Paso, TX, 79968, United States of America
| | - Armando Varela-Ramirez
- Department of Biological Sciences and Border Biomedical Research Center, University of Texas at El Paso, El Paso, TX, 79968, United States of America
| | - Manuel Miranda
- Department of Biological Sciences and Border Biomedical Research Center, University of Texas at El Paso, El Paso, TX, 79968, United States of America
- * E-mail:
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7
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Mihalikova A, Baliova M, Jursky F. Calcium dependent interaction of calmodulin with the GlyT1 C-terminus. Neurochem Res 2014; 39:2225-33. [PMID: 25168305 DOI: 10.1007/s11064-014-1424-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2014] [Revised: 08/19/2014] [Accepted: 08/21/2014] [Indexed: 11/25/2022]
Abstract
The cytoplasmic regions of neurotransmitter transporters play an important role in their trafficking. This process is, to a high extent, tuned by calcium and calcium binding proteins, but the exact molecular connection are still not fully understood. In this work we found that the C-terminal region of the mouse glycine transporter GlyT1b is able to specifically interact with calmodulin in the presence of calcium. We found that several GlyT1 C-terminal mutations, including those in the ER retention signal, either eliminate or increase calmodulin interaction in vitro. In tissue-culture-expressed GlyT1 at least two of these mutations altered the sensitivity of GlyT1 surface expression and glycine uptake to calmodulin antagonists. These results suggest the possible involvement of calmodulin or calmodulin-like interactions in the regulation of GlyT1C-mediated transporter trafficking.
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Affiliation(s)
- Andrea Mihalikova
- Laboratory of Neurobiology, Institute of Molecular Biology, Slovak Academy of Sciences, Dubravska cesta 21, 845 51, Bratislava, Slovakia
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8
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Pinto MCX, Simão F, da Costa FLP, Rosa DV, de Paiva MJN, Resende RR, Romano-Silva MA, Gomez MV, Gomez RS. Sarcosine preconditioning induces ischemic tolerance against global cerebral ischemia. Neuroscience 2014; 271:160-9. [PMID: 24797328 DOI: 10.1016/j.neuroscience.2014.04.054] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Revised: 04/09/2014] [Accepted: 04/24/2014] [Indexed: 02/01/2023]
Abstract
Brain ischemic tolerance is an endogenous protective mechanism activated by a preconditioning stimulus that is closely related to N-methyl-d-aspartate receptor (NMDAR). Glycine transporter type 1 (GlyT-1) inhibitors potentiate NMDAR and suggest an alternative strategy for brain preconditioning. The aim of this work was to evaluate the effects of brain preconditioning induced by sarcosine, a GlyT-1 inhibitor, against global cerebral ischemia and its relation to NMDAR. Sarcosine was administered over 7 days (300 or 500 mg/kg/day, ip) before the induction of a global cerebral ischemia model in Wistar rats (male, 8-week-old). It was observed that sarcosine preconditioning reduced cell death in rat hippocampi submitted to cerebral ischemia. Hippocampal levels of glycine were decreased in sarcosine-treated animals, which was associated with a reduction of [(3)H] glycine uptake and a decrease in glycine transporter expression (GlyT-1 and GlyT-2). The expression of glycine receptors and the NR1 and NR2A subunits of NMDAR were not affected by sarcosine preconditioning. However, sarcosine preconditioning reduced the expression of the NR2B subunits of NMDAR. In conclusion, these data demonstrate that sarcosine preconditioning induces ischemic tolerance against global cerebral ischemia and this neuroprotective state is associated with changes in glycine transport and reduction of NR2B-containing NMDAR expression.
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Affiliation(s)
- M C X Pinto
- INCT de Medicina Molecular, Faculdade de Medicina, Universidade Federal de Minas Gerais, Avenida Alfredo Balena 190, 30130-100 Belo Horizonte, MG, Brazil; Departamento de Cirurgia, Faculdade de Medicina, Universidade Federal de Minas Gerais, Avenida Alfredo Balena, 190, 30130-100 Belo Horizonte, MG, Brazil.
| | - F Simão
- Laboratório de Neurociências, Instituto de Pesquisas Biomédicas, Pontifícia Universidade Católica do Rio Grande do Sul, Avenida Ipiranga 6690, 90610-000 Porto Alegre, RS, Brazil
| | - F L P da Costa
- INCT de Medicina Molecular, Faculdade de Medicina, Universidade Federal de Minas Gerais, Avenida Alfredo Balena 190, 30130-100 Belo Horizonte, MG, Brazil; Departamento de Cirurgia, Faculdade de Medicina, Universidade Federal de Minas Gerais, Avenida Alfredo Balena, 190, 30130-100 Belo Horizonte, MG, Brazil
| | - D V Rosa
- INCT de Medicina Molecular, Faculdade de Medicina, Universidade Federal de Minas Gerais, Avenida Alfredo Balena 190, 30130-100 Belo Horizonte, MG, Brazil
| | - M J N de Paiva
- Departamento de Bioquímica e Imunologia, Instituto de Ciência Biológicas, Universidade Federal de Minas Gerais, Avenida Antônio Carlos, 6627, 31270-901 Belo Horizonte, MG, Brazil
| | - R R Resende
- Departamento de Bioquímica e Imunologia, Instituto de Ciência Biológicas, Universidade Federal de Minas Gerais, Avenida Antônio Carlos, 6627, 31270-901 Belo Horizonte, MG, Brazil
| | - M A Romano-Silva
- INCT de Medicina Molecular, Faculdade de Medicina, Universidade Federal de Minas Gerais, Avenida Alfredo Balena 190, 30130-100 Belo Horizonte, MG, Brazil
| | - M V Gomez
- Instituto de Ensino e Pesquisa da Santa Casa de Belo Horizonte, R. Domingos Vieira, 590, Belo Horizonte, MG, Brazil
| | - R S Gomez
- Departamento de Cirurgia, Faculdade de Medicina, Universidade Federal de Minas Gerais, Avenida Alfredo Balena, 190, 30130-100 Belo Horizonte, MG, Brazil.
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9
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Sorkina T, Caltagarone J, Sorkin A. Flotillins regulate membrane mobility of the dopamine transporter but are not required for its protein kinase C dependent endocytosis. Traffic 2013; 14:709-24. [PMID: 23418867 DOI: 10.1111/tra.12059] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Revised: 02/13/2013] [Accepted: 02/18/2013] [Indexed: 12/15/2022]
Abstract
Flotillins were proposed to mediate clathrin-independent endocytosis, and recently, flotillin-1 was implicated in the protein kinase C (PKC)-triggered endocytosis of the dopamine transporter (DAT). Since endocytosis of DAT was previously shown to be clathrin-mediated, we re-examined the role of clathrin coat proteins and flotillin in DAT endocytosis using DAT tagged with the hemagglutinin epitope (HA) in the extracellular loop and a quantitative HA antibody uptake assay. Depletion of flotillin-1, flotillin-2 or both flotillins together by small interfering RNAs (siRNAs) did not inhibit PKC-dependent internalization and degradation of HA-DAT. In contrast, siRNAs to clathrin heavy chain and μ2 subunit of clathrin adaptor complex AP-2 as well as a dynamin inhibitor Dyngo-4A significantly decreased PKC-dependent endocytosis of HA-DAT. Similarly, endocytosis and degradation of DAT that is not epitope-tagged were highly sensitive to the clathrin siRNAs and dynamin inhibition but were not affected by flotillin knockdown. Very little co-localization of DAT with flotillins was observed in cells ectopically expressing DAT and in cultured mouse dopaminergic neurons. Depletion of flotillins increased diffusion rates of HA-DAT in the plasma membrane, suggesting that flotillin-organized microdomains may regulate the lateral mobility of DAT. We propose that clathrin-mediated endocytosis is the major pathway of PKC-dependent internalization of DAT, and that flotillins may modulate functional association of DAT with plasma membrane rafts rather than mediate DAT endocytosis.
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Affiliation(s)
- Tatiana Sorkina
- Department of Cell Biology, University of Pittsburgh, School of Medicine, Pittsburgh, PA, USA
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10
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de Juan-Sanz J, Núñez E, López-Corcuera B, Aragón C. Constitutive endocytosis and turnover of the neuronal glycine transporter GlyT2 is dependent on ubiquitination of a C-terminal lysine cluster. PLoS One 2013; 8:e58863. [PMID: 23484054 PMCID: PMC3590132 DOI: 10.1371/journal.pone.0058863] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Accepted: 02/07/2013] [Indexed: 12/13/2022] Open
Abstract
Inhibitory glycinergic neurotransmission is terminated by sodium and chloride-dependent plasma membrane glycine transporters (GlyTs). The mainly glial glycine transporter GlyT1 is primarily responsible for the completion of inhibitory neurotransmission and the neuronal glycine transporter GlyT2 mediates the reuptake of the neurotransmitter that is used to refill synaptic vesicles in the terminal, a fundamental role in the physiology and pathology of glycinergic neurotransmission. Indeed, inhibitory glycinergic neurotransmission is modulated by the exocytosis and endocytosis of GlyT2. We previously reported that constitutive and Protein Kinase C (PKC)-regulated endocytosis of GlyT2 is mediated by clathrin and that PKC accelerates GlyT2 endocytosis by increasing its ubiquitination. However, the role of ubiquitination in the constitutive endocytosis and turnover of this protein remains unexplored. Here, we show that ubiquitination of a C-terminus four lysine cluster of GlyT2 is required for constitutive endocytosis, sorting into the slow recycling pathway and turnover of the transporter. Ubiquitination negatively modulates the turnover of GlyT2, such that increased ubiquitination driven by PKC activation accelerates transporter degradation rate shortening its half-life while decreased ubiquitination increases transporter stability. Finally, ubiquitination of GlyT2 in neurons is highly responsive to the free pool of ubiquitin, suggesting that the deubiquitinating enzyme (DUB) ubiquitin C-terminal hydrolase-L1 (UCHL1), as the major regulator of neuronal ubiquitin homeostasis, indirectly modulates the turnover of GlyT2. Our results contribute to the elucidation of the mechanisms underlying the dynamic trafficking of this important neuronal protein which has pathological relevance since mutations in the GlyT2 gene (SLC6A5) are the second most common cause of human hyperekplexia.
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Affiliation(s)
- Jaime de Juan-Sanz
- Centro de Biología Molecular ‘‘Severo Ochoa’’, Universidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas, Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), ISCIII, Madrid, Spain
- IdiPAZ-Hospital Universitario La Paz, Madrid, Spain
| | - Enrique Núñez
- Centro de Biología Molecular ‘‘Severo Ochoa’’, Universidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas, Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), ISCIII, Madrid, Spain
- IdiPAZ-Hospital Universitario La Paz, Madrid, Spain
| | - Beatriz López-Corcuera
- Centro de Biología Molecular ‘‘Severo Ochoa’’, Universidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas, Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), ISCIII, Madrid, Spain
- IdiPAZ-Hospital Universitario La Paz, Madrid, Spain
| | - Carmen Aragón
- Centro de Biología Molecular ‘‘Severo Ochoa’’, Universidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas, Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), ISCIII, Madrid, Spain
- IdiPAZ-Hospital Universitario La Paz, Madrid, Spain
- * E-mail:
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11
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Ubiquitination of neurotransmitter receptors and postsynaptic scaffolding proteins. Neural Plast 2013; 2013:432057. [PMID: 23431475 PMCID: PMC3574743 DOI: 10.1155/2013/432057] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Accepted: 12/26/2012] [Indexed: 12/19/2022] Open
Abstract
The human brain is made up of an extensive network of neurons that communicate by forming specialized connections called synapses. The amount, location, and dynamic turnover of synaptic proteins, including neurotransmitter receptors and synaptic scaffolding molecules, are under complex regulation and play a crucial role in synaptic connectivity and plasticity, as well as in higher brain functions. An increasing number of studies have established ubiquitination and proteasome-mediated degradation as universal mechanisms in the control of synaptic protein homeostasis. In this paper, we focus on the role of the ubiquitin-proteasome system (UPS) in the turnover of major neurotransmitter receptors, including glutamatergic and nonglutamatergic receptors, as well as postsynaptic receptor-interacting proteins.
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12
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Schaeuble K, Hauser MA, Rippl AV, Bruderer R, Otero C, Groettrup M, Legler DF. Ubiquitylation of the chemokine receptor CCR7 enables efficient receptor recycling and cell migration. J Cell Sci 2012; 125:4463-74. [PMID: 22797918 DOI: 10.1242/jcs.097519] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The chemokine receptor CCR7 is essential for lymphocyte and dendritic cell homing to secondary lymphoid organs. Owing to the ability to induce directional migration, CCR7 and its ligands CCL19 and CCL21 are pivotal for the regulation of the immune system. Here, we identify a novel function for receptor ubiquitylation in the regulation of the trafficking process of this G-protein-coupled seven transmembrane receptor. We discovered that CCR7 is ubiquitylated in a constitutive, ligand-independent manner and that receptor ubiquitylation regulates the basal trafficking of CCR7 in the absence of chemokine. Upon CCL19 binding, we show that internalized CCR7 recycles back to the plasma membrane via the trans-Golgi network. An ubiquitylation-deficient CCR7 mutant internalized normally after ligand binding, but inefficiently recycled in immune cells and was transiently retarded in the trans-Golgi network compartment of HEK293 transfectants. Finally, we demonstrate that the lack of CCR7 ubiquitylation profoundly impairs immune cell migration. Our results provide evidence for a novel function of receptor ubiquitylation in the regulation of CCR7 recycling and immune cell migration.
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Affiliation(s)
- Karin Schaeuble
- Biotechnology Institute Thurgau (BITg) at the University of Konstanz, Unterseestrasse 47, CH-8280 Kreuzlingen, Switzerland
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13
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Martínez-Villarreal J, García Tardón N, Ibáñez I, Giménez C, Zafra F. Cell surface turnover of the glutamate transporter GLT-1 is mediated by ubiquitination/deubiquitination. Glia 2012; 60:1356-65. [PMID: 22593014 DOI: 10.1002/glia.22354] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2012] [Accepted: 04/23/2012] [Indexed: 11/11/2022]
Abstract
The main glutamate transporter in the brain, GLT-1, mediates glutamatergic neurotransmission in both physiological and pathological conditions. GLT-1 activity is controlled by both constitutive and regulated trafficking, and although recent evidence indicates that the turnover of this protein in the plasma membrane is accelerated by protein kinase C via an ubiquitin-dependent process, the mechanisms driving the constitutive trafficking of GLT-1 remain unexplored. Here, we used a heterologous system and primary astrocytes to investigate the turnover of GLT-1 and the role of ubiquitin attachment in this process. We show that GLT-1 is endocytosed constitutively in a clathrin-dependent manner, recycling the transporter into endosomes containing EEA1 and Rab4, a marker of rapidly recycling endosomes, and not Rab11 or Rab7, markers of the slow recycling and late endosomal compartments, respectively. We also show that this process is dependent on ubiquitination, because the inhibitor of the ubiquitin-activating enzyme E1, 4[4-(5-nitro-furan-2-ylmethylene)-3,5-dioxo-pyrazolidin-1-yl]-benzoic acid ethyl ester, promotes the retention of GLT-1 at the plasma membrane. Moreover, site-directed mutagenesis demonstrated the involvement of lysines 517 and 526 of GLT-1 in the constitutive internalization of the transporter. The translocation of GLT-1 from the recycling endosomes to the plasma membrane was blocked by LDN-57444, a specific inhibitor to the deubiquitinating enzyme (DUB) ubiquitin C-terminal hydrolase-L1, but not by an inhibitor of the related DUB ubiquitin C-terminal hydrolase-L3, supporting the existence of specific ubiquitination/deubiquitination cycles that ensure the correct concentrations of GLT-1 at the cell surface.
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Affiliation(s)
- Jaime Martínez-Villarreal
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Madrid, Spain
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14
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de Juan-Sanz J, Zafra F, López-Corcuera B, Aragón C. Endocytosis of the neuronal glycine transporter GLYT2: role of membrane rafts and protein kinase C-dependent ubiquitination. Traffic 2011; 12:1850-67. [PMID: 21910806 DOI: 10.1111/j.1600-0854.2011.01278.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Glycinergic neurotransmission is terminated by sodium- and chloride-dependent plasma membrane transporters. The neuronal glycine transporter 2 (GLYT2) supplies the terminal with substrate to refill synaptic vesicles containing glycine. This crucial process is defective in human hyperekplexia, a condition that can be caused by mutations in GLYT2. Inhibitory glycinergic neurotransmission is modulated by the GLYT2 exocytosis/endocytosis equilibrium, although the mechanisms underlying the turnover of this transporter remain elusive. We studied GLYT2 internalization pathways and the role of ubiquitination and membrane raft association of the transporter in its endocytosis. Using pharmacological tools, dominant-negative mutants and small-interfering RNAs, we show that the clathrin-mediated pathway is the primary mechanism for constitutive and regulated GLYT2 endocytosis in heterologous cells and neurons. We show that GLYT2 is constitutively internalized from cell surface lipid rafts, remaining associated with rafts in subcellular recycling structures. Protein kinase C (PKC) negatively modulates GLYT2 via rapid and dynamic redistribution of GLYT2 from raft to non-raft membrane subdomains and increasing ubiquitinated GLYT2 endocytosis. This biphasic mechanism is a versatile means to modulate GLYT2 behavior and hence, inhibitory glycinergic neurotransmission. These findings may reveal new therapeutic targets to address glycinergic pathologies associated with alterations in GLYT2 trafficking.
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Affiliation(s)
- Jaime de Juan-Sanz
- Departamento de Biología Molecular and Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid, Madrid, Spain
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15
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Lei JT, Mazumdar T, Martinez-Moczygemba M. Three lysine residues in the common β chain of the interleukin-5 receptor are required for Janus kinase (JAK)-dependent receptor ubiquitination, endocytosis, and signaling. J Biol Chem 2011; 286:40091-103. [PMID: 21965659 DOI: 10.1074/jbc.m111.273482] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Eosinophils are multifunctional leukocytes implicated in the pathogenesis of numerous inflammatory diseases including allergic asthma and hypereosinophilic syndrome. Eosinophil physiology is critically dependent on IL-5 and the IL-5 receptor (IL-5R), composed of a ligand binding α chain (IL-5Rα), and a common β chain, βc. Previously, we demonstrated that the βc cytoplasmic tail is ubiquitinated and degraded by proteasomes following IL-5 stimulation. However, a complete understanding of the role of βc ubiquitination in IL-5R biology is currently lacking. By using a well established, stably transduced HEK293 cell model system, we show here that in the absence of ubiquitination, βc subcellular localization, IL-5-induced endocytosis, turnover, and IL-5R signaling were significantly impaired. Whereas ubiquitinated IL-5Rs internalized into trafficking endosomes for their degradation, ubiquitination-deficient IL-5Rs accumulated on the cell surface and displayed blunted signaling even after IL-5 stimulation. Importantly, we identified a cluster of three membrane-proximal βc lysine residues (Lys(457), Lys(461), and Lys(467)) whose presence was required for both JAK1/2 binding to βc and receptor ubiquitination. These findings establish that JAK kinase binding to βc requires the presence of three critical βc lysine residues, and this binding event is essential for receptor ubiquitination, endocytosis, and signaling.
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Affiliation(s)
- Jonathan T Lei
- Department of Microbial and Molecular Pathogenesis, College of Medicine, Texas A&M Health Science Center, Houston, Texas 77030, USA
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16
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Kristensen AS, Andersen J, Jørgensen TN, Sørensen L, Eriksen J, Loland CJ, Strømgaard K, Gether U. SLC6 neurotransmitter transporters: structure, function, and regulation. Pharmacol Rev 2011; 63:585-640. [PMID: 21752877 DOI: 10.1124/pr.108.000869] [Citation(s) in RCA: 591] [Impact Index Per Article: 45.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The neurotransmitter transporters (NTTs) belonging to the solute carrier 6 (SLC6) gene family (also referred to as the neurotransmitter-sodium-symporter family or Na(+)/Cl(-)-dependent transporters) comprise a group of nine sodium- and chloride-dependent plasma membrane transporters for the monoamine neurotransmitters serotonin (5-hydroxytryptamine), dopamine, and norepinephrine, and the amino acid neurotransmitters GABA and glycine. The SLC6 NTTs are widely expressed in the mammalian brain and play an essential role in regulating neurotransmitter signaling and homeostasis by mediating uptake of released neurotransmitters from the extracellular space into neurons and glial cells. The transporters are targets for a wide range of therapeutic drugs used in treatment of psychiatric diseases, including major depression, anxiety disorders, attention deficit hyperactivity disorder and epilepsy. Furthermore, psychostimulants such as cocaine and amphetamines have the SLC6 NTTs as primary targets. Beginning with the determination of a high-resolution structure of a prokaryotic homolog of the mammalian SLC6 transporters in 2005, the understanding of the molecular structure, function, and pharmacology of these proteins has advanced rapidly. Furthermore, intensive efforts have been directed toward understanding the molecular and cellular mechanisms involved in regulation of the activity of this important class of transporters, leading to new methodological developments and important insights. This review provides an update of these advances and their implications for the current understanding of the SLC6 NTTs.
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Affiliation(s)
- Anders S Kristensen
- Department of Medicinal Chemistry, Faculty of Pharmaceutical Sciences, University of Copenhagen, Copenhagen, Denmark.
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17
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The deubiquitinating enzyme DUB2A enhances CSF3 signalling by attenuating lysosomal routing of the CSF3 receptor. Biochem J 2011; 434:343-51. [PMID: 21155715 DOI: 10.1042/bj20101628] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Ubiquitination of the CSF3R [CSF3 (colony-stimulating factor 3) receptor] occurs after activated CSF3Rs are internalized and reside in early endosomes. CSF3R ubiquitination is crucial for lysosomal routing and degradation. The E3 ligase SOCS3 (suppressor of cytokine signalling 3) has been shown to play a major role in this process. Deubiquitinating enzymes remove ubiquitin moieties from target proteins by proteolytic cleavage. Two of these enzymes, AMSH [associated molecule with the SH3 domain of STAM (signal transducing adaptor molecule)] and UBPY (ubiquitin isopeptidase Y), interact with the general endosomal sorting machinery. Whether deubiquitinating enzymes control CSF3R trafficking from early towards late endosomes is unknown. In the present study, we asked whether AMSH, UBPY or a murine family of deubiquitinating enzymes could fulfil such a role. This DUB family (deubiquitin enzyme family) comprises four members (DUB1, DUB1A, DUB2 and DUB2A), which were originally described as being haematopoietic-specific and cytokine-inducible, but their function in cytokine receptor routing and signalling has remained largely unknown. We show that DUB2A expression is induced by CSF3 in myeloid 32D cells and that DUB2 decreases ubiquitination and lysosomal degradation of the CSF3R, leading to prolonged signalling. These results support a model in which CSF3R ubiquitination is dynamically controlled at the early endosome by feedback mechanisms involving CSF3-induced E3 ligase (SOCS3) and deubiquitinase (DUB2A) activities.
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18
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Labrie V, Wong AHC, Roder JC. Contributions of the D-serine pathway to schizophrenia. Neuropharmacology 2011; 62:1484-503. [PMID: 21295046 DOI: 10.1016/j.neuropharm.2011.01.030] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2010] [Revised: 01/16/2011] [Accepted: 01/19/2011] [Indexed: 01/30/2023]
Abstract
The glutamate neurotransmitter system is one of the major candidate pathways for the pathophysiology of schizophrenia, and increased understanding of the pharmacology, molecular biology and biochemistry of this system may lead to novel treatments. Glutamatergic hypofunction, particularly at the NMDA receptor, has been hypothesized to underlie many of the symptoms of schizophrenia, including psychosis, negative symptoms and cognitive impairment. This review will focus on D-serine, a co-agonist at the NMDA receptor that in combination with glutamate, is required for full activation of this ion channel receptor. Evidence implicating D-serine, NMDA receptors and related molecules, such as D-amino acid oxidase (DAO), G72 and serine racemase (SRR), in the etiology or pathophysiology of schizophrenia is discussed, including knowledge gained from mouse models with altered D-serine pathway genes and from preliminary clinical trials with D-serine itself or compounds modulating the D-serine pathway. Abnormalities in D-serine availability may underlie glutamatergic dysfunction in schizophrenia, and the development of new treatments acting through the D-serine pathway may significantly improve outcomes for many schizophrenia patients.
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Affiliation(s)
- Viviane Labrie
- Krembil Family Epigenetics Laboratory, Centre for Addiction and Mental Health, 250 College St, Toronto, ON M5T 1R8, Canada.
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19
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Vina-Vilaseca A, Bender-Sigel J, Sorkina T, Closs EI, Sorkin A. Protein kinase C-dependent ubiquitination and clathrin-mediated endocytosis of the cationic amino acid transporter CAT-1. J Biol Chem 2011; 286:8697-8706. [PMID: 21212261 DOI: 10.1074/jbc.m110.186858] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Cationic amino acid transporter 1 (CAT-1) is responsible for the bulk of the uptake of cationic amino acids in most mammalian cells. Activation of protein kinase C (PKC) leads to down-regulation of the cell surface CAT-1. To examine the mechanisms of PKC-induced down-regulation of CAT-1, a functional mutant of CAT-1 (CAT-1-HA-GFP) was generated in which a hemagglutinin antigen (HA) epitope tag was introduced into the second extracellular loop and GFP was attached to the carboxyl terminus. CAT-1-HA-GFP was stably expressed in porcine aorthic endothelial and human epithelial kidney (HEK) 293 cells. Using the HA antibody internalization assay we have demonstrated that PKC-dependent endocytosis was strongly inhibited by siRNA depletion of clathrin heavy chain, indicating that CAT-1-HA-GFP internalization requires clathrin-coated pits. Internalized CAT-1-HA-GFP was accumulated in early, recycling, and late endosomes. PKC activation also resulted in ubiquitination of CAT-1. CAT-1 ubiquitination and endocytosis in phorbol ester-stimulated porcine aorthic endothelial and HEK293 cells were inhibited by siRNA knockdown of NEDD4-2 and NEDD4-1 E3 ubiquitin ligases, respectively. In contrast, ubiquitination and endocytosis of the dopamine transporter was dependent on NEDD4-2 in all cell types tested. Altogether, our data suggest that ubiquitination mediated by NEDD4-2 or NEDD4-1 leading to clathrin-mediated endocytosis is the common mode of regulation of various transporter proteins by PKC.
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Affiliation(s)
- Arnau Vina-Vilaseca
- From the Department of Pharmacology, Anschutz Medical Center, University of Colorado Denver, Aurora, Colorado 80010
| | - Julia Bender-Sigel
- the Department of Pharmacology, University Medical Center of the Johannes Gutenberg University Mainz, Mainz 55101, Germany
| | - Tatiana Sorkina
- the Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, and
| | - Ellen Ildicho Closs
- the Department of Pharmacology, University Medical Center of the Johannes Gutenberg University Mainz, Mainz 55101, Germany
| | - Alexander Sorkin
- From the Department of Pharmacology, Anschutz Medical Center, University of Colorado Denver, Aurora, Colorado 80010,; the Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, and.
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20
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Howard A, Hirst BH. The Glycine Transporter GLYT1 in Human Intestine: Expression and Function. Biol Pharm Bull 2011; 34:784-8. [DOI: 10.1248/bpb.34.784] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Alison Howard
- Epithelial Research Group, Institute for Cell and Molecular Biosciences, Faculty of Medical Sciences, Newcastle University
| | - Barry Hugo Hirst
- Epithelial Research Group, Institute for Cell and Molecular Biosciences, Faculty of Medical Sciences, Newcastle University
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