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McMann E, Gorski SM. Last but not least: emerging roles of the autophagy-related protein ATG4D. Autophagy 2024:1-12. [PMID: 38920354 DOI: 10.1080/15548627.2024.2369436] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Accepted: 06/13/2024] [Indexed: 06/27/2024] Open
Abstract
The evolutionarily conserved ATG4 cysteine proteases regulate macroautophagy/autophagy through the priming and deconjugation of the Atg8-family proteins. In mammals there are four ATG4 family members (ATG4A, ATG4B, ATG4C, ATG4D) but ATG4D has been relatively understudied. Heightened interest in ATG4D has been stimulated by recent links to human disease. Notably, genetic variations in human ATG4D were implicated in a heritable neurodevelopmental disorder. Genetic analyses in dogs, along with loss-of-function zebrafish and mouse models, further support a neuroprotective role for ATG4D. Here we discuss the evidence connecting ATG4D to neurological diseases and other pathologies and summarize its roles in both autophagy-dependent and autophagy-independent cellular processes.Abbrevation: ATG: autophagy related; BafA1: bafilomycin A1; BCL2: BCL2 apoptosis regulator; BH3: BCL2 homology region 3; CASP3: caspase 3; EV: extracellular vesicle; GABA: gamma aminobutyric acid; GABARAP: GABA type A receptor-associated protein; GABARAPL1: GABA type A receptor associated protein like 1; GABARAPL2: GABA type A receptor associated protein like 2; GFP: green fluorescent protein; LIR: LC3-interacting region; MAP1LC3: microtubule associated protein 1 light chain 3; MEF: mouse embryonic fibroblast; MYC: MYC proto-oncogene, bHLH transcription factor; PE: phosphatidylethanolamine; PS: phosphatidylserine; QKO: quadruple knockout; SDS-PAGE: sodium dodecyl sulfate-polyacrylamide gel; SQSTM1: sequestosome 1.
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Affiliation(s)
- Emily McMann
- Canada's Michael Smith Genome Sciences Centre at BC Cancer, Vancouver, British Columbia, Canada
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Sharon M Gorski
- Canada's Michael Smith Genome Sciences Centre at BC Cancer, Vancouver, British Columbia, Canada
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
- Centre for Cell Biology, Development and Disease, Simon Fraser University, Burnaby, British Columbia, Canada
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2
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Nakashima A, Furuta A, Yamada K, Yoshida-Kawaguchi M, Yamaki-Ushijima A, Yasuda I, Ito M, Yamashita S, Tsuda S, Yoneda S, Cheng S, Sharma S, Shima T. The Role of Autophagy in the Female Reproduction System: For Beginners to Experts in This Field. BIOLOGY 2023; 12:biology12030373. [PMID: 36979065 PMCID: PMC10045718 DOI: 10.3390/biology12030373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2023] [Revised: 02/21/2023] [Accepted: 02/24/2023] [Indexed: 03/02/2023]
Abstract
Autophagy is a fundamental process involved in regulating cellular homeostasis. Autophagy has been classically discovered as a cellular process that degrades cytoplasmic components non-selectively to produce energy. Over the past few decades, this process has been shown to work in energy production, as well as in the reduction of excessive proteins, damaged organelles, and membrane trafficking. It contributes to many human diseases, such as neurodegenerative diseases, carcinogenesis, diabetes mellitus, development, longevity, and reproduction. In this review, we provide important information for interpreting results related to autophagic experiments and present the role of autophagy in this field.
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Affiliation(s)
- Akitoshi Nakashima
- Department of Obstetrics and Gynecology, Toyama Autophagy Team in Gynecology and Obstetrics, University of Toyama, Toyama 930-0194, Japan
- Correspondence: ; Tel.: +81-76-434-7357
| | - Atsushi Furuta
- Department of Obstetrics and Gynecology, Toyama Autophagy Team in Gynecology and Obstetrics, University of Toyama, Toyama 930-0194, Japan
| | - Kiyotaka Yamada
- Department of Obstetrics and Gynecology, Toyama Autophagy Team in Gynecology and Obstetrics, University of Toyama, Toyama 930-0194, Japan
| | - Mihoko Yoshida-Kawaguchi
- Department of Obstetrics and Gynecology, Toyama Autophagy Team in Gynecology and Obstetrics, University of Toyama, Toyama 930-0194, Japan
| | - Akemi Yamaki-Ushijima
- Department of Obstetrics and Gynecology, Toyama Autophagy Team in Gynecology and Obstetrics, University of Toyama, Toyama 930-0194, Japan
| | - Ippei Yasuda
- Department of Obstetrics and Gynecology, Toyama Autophagy Team in Gynecology and Obstetrics, University of Toyama, Toyama 930-0194, Japan
| | - Masami Ito
- Department of Obstetrics and Gynecology, Toyama Autophagy Team in Gynecology and Obstetrics, University of Toyama, Toyama 930-0194, Japan
| | - Satoshi Yamashita
- Department of Obstetrics and Gynecology, Toyama Autophagy Team in Gynecology and Obstetrics, University of Toyama, Toyama 930-0194, Japan
| | - Sayaka Tsuda
- Department of Obstetrics and Gynecology, Toyama Autophagy Team in Gynecology and Obstetrics, University of Toyama, Toyama 930-0194, Japan
| | - Satoshi Yoneda
- Department of Obstetrics and Gynecology, Toyama Autophagy Team in Gynecology and Obstetrics, University of Toyama, Toyama 930-0194, Japan
| | - Shibin Cheng
- Departments of Pediatrics, Women and Infants Hospital of Rhode Island, Warren Alpert Medical School of Brown University, Providence, RI 02905, USA
| | - Surendra Sharma
- Departments of Pediatrics, Women and Infants Hospital of Rhode Island, Warren Alpert Medical School of Brown University, Providence, RI 02905, USA
| | - Tomoko Shima
- Department of Obstetrics and Gynecology, Toyama Autophagy Team in Gynecology and Obstetrics, University of Toyama, Toyama 930-0194, Japan
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Chan JCY, Gorski SM. Unlocking the gate to GABARAPL2. Biol Futur 2022; 73:157-169. [PMID: 35486231 DOI: 10.1007/s42977-022-00119-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Accepted: 04/08/2022] [Indexed: 10/18/2022]
Abstract
GABARAPL2 was initially characterized for its involvement in protein transport and membrane fusion events, but has since gained notoriety for its role in autophagy. GABARAPL2 is frequently studied alongside its GABARAP subfamily members, GABARAP and GABARAPL1. Although functional redundancy exists among the subfamily members, a complex network of molecular interactions, physiological processes and pathologies can be primarily related to GABARAPL2. GABARAPL2 has a multifaceted role, ranging from cellular differentiation to intracellular degradation. Much of what we know about GABARAPL2 is gained through identifying its interacting partners-a list that is constantly growing. In this article, we review both the autophagy-dependent and autophagy-independent roles of GABARAPL2, and emphasize their implications for both health and disease.
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Affiliation(s)
- Jennifer C Y Chan
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, V5A 1S6, Canada.,Canada's Michael Smith Genome Sciences Centre at BC Cancer, Vancouver, BC, V5Z 1L3, Canada
| | - Sharon M Gorski
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, V5A 1S6, Canada. .,Canada's Michael Smith Genome Sciences Centre at BC Cancer, Vancouver, BC, V5Z 1L3, Canada. .,Centre for Cell Biology, Development and Disease, Simon Fraser University, Burnaby, BC, V5A 1S6, Canada.
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4
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Does GEC1 Enhance Expression and Forward Trafficking of the Kappa Opioid Receptor (KOR) via Its Ability to Interact with NSF Directly? Handb Exp Pharmacol 2022; 271:83-96. [PMID: 33404775 PMCID: PMC9126001 DOI: 10.1007/164_2020_398] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
We reported previously that GEC1 (glandular epithelial cell 1), a member of microtubule-associated proteins (MAPs), interacted directly with the C-tail of KOR (KCT) and tubulin and enhanced cell surface expression of KOR in CHO cells by facilitating its trafficking along the export pathway. Two GEC1 analogs (GABARAP and GATE16) were also shown to increase KOR expression. In addition, to understand the underlying mechanism, we demonstrated that N-ethylmaleimide-sensitive factor (NSF), an essential component for membrane fusion, co-immunoprecipitated with GEC1 from brain extracts. In this study, using pull-down techniques, we have found that (1) GEC1 interacts with NSF directly and prefers the ADP-bound NSF to the ATP-bound NSF; (2) D1 and/or D2 domain(s) of NSF interact with GEC1, but the N domain of NSF does not; (3) NSF does not interact with KCT directly, but forms a protein complex with KCT via GEC1; (4) NSF and/or α-SNAP do not affect KCT-GEC1 interaction. Thus, GEC1 (vs the α-SNAP/SNAREs complex) binds to NSF in distinctive ways in terms of the ADP- or ATP-bound form and domains of NSF involved. In conclusion, GEC1 may, via its direct interactions with KOR, NSF, and tubulin, enhance trafficking and fusion of KOR-containing vesicles selectively along the export pathway, which leads to increase in surface expression of KOR. GABARAP and GATE16 may enhance KOR expression in a similar way.
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Nguyen N, Olivas TJ, Mires A, Jin J, Yu S, Luan L, Nag S, Kauffman KJ, Melia TJ. The insufficiency of ATG4A in macroautophagy. J Biol Chem 2020; 295:13584-13600. [PMID: 32732290 DOI: 10.1074/jbc.ra120.013897] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 07/21/2020] [Indexed: 12/17/2022] Open
Abstract
During autophagy, LC3 and GABARAP proteins become covalently attached to phosphatidylethanolamine on the growing autophagosome. This attachment is also reversible. Deconjugation (or delipidation) involves the proteolytic cleavage of an isopeptide bond between LC3 or GABARAP and the phosphatidylethanolamine headgroup. This cleavage is carried about by the ATG4 family of proteases (ATG4A, B, C, and D). Many studies have established that ATG4B is the most active of these proteases and is sufficient for autophagy progression in simple cells. Here we examined the second most active protease, ATG4A, to map out key regulatory motifs on the protein and to establish its activity in cells. We utilized fully in vitro reconstitution systems in which we controlled the attachment of LC3/GABARAP members and discovered a role for a C-terminal LC3-interacting region on ATG4A in regulating its access to LC3/GABARAP. We then used a gene-edited cell line in which all four ATG4 proteases have been knocked out to establish that ATG4A is insufficient to support autophagy and is unable to support GABARAP proteins removal from the membrane. As a result, GABARAP proteins accumulate on membranes other than mature autophagosomes. These results suggest that to support efficient production and consumption of autophagosomes, additional factors are essential including possibly ATG4B itself or one of its proteolytic products in the LC3 family.
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Affiliation(s)
- Nathan Nguyen
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Taryn J Olivas
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Antonio Mires
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut, USA; National Agrarian University-La Molina, Lima, Peru
| | - Jiaxin Jin
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut, USA; Lanzhou University Second Hospital, Lanzhou, Gansu Province, China
| | - Shenliang Yu
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Lin Luan
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Shanta Nag
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Karlina J Kauffman
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Thomas J Melia
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut, USA.
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Suomi F, McWilliams T. Autophagy in the mammalian nervous system: a primer for neuroscientists. Neuronal Signal 2019; 3:NS20180134. [PMID: 32269837 PMCID: PMC7104325 DOI: 10.1042/ns20180134] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2019] [Revised: 07/06/2019] [Accepted: 08/05/2019] [Indexed: 12/12/2022] Open
Abstract
Autophagy refers to the lysosomal degradation of damaged or superfluous components and is essential for metabolic plasticity and tissue integrity. This evolutionarily conserved process is particularly vital to mammalian post-mitotic cells such as neurons, which face unique logistical challenges and must sustain homoeostasis over decades. Defective autophagy has pathophysiological importance, especially for human neurodegeneration. The present-day definition of autophagy broadly encompasses two distinct yet related phenomena: non-selective and selective autophagy. In this minireview, we focus on established and emerging concepts in the field, paying particular attention to the physiological significance of macroautophagy and the burgeoning world of selective autophagy pathways in the context of the vertebrate nervous system. By highlighting established basics and recent breakthroughs, we aim to provide a useful conceptual framework for neuroscientists interested in autophagy, in addition to autophagy enthusiasts with an eye on the nervous system.
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Affiliation(s)
- Fumi Suomi
- Translational Stem Cell Biology and Metabolism Program, Research Programs Unit, Faculty of Medicine, Biomedicum Helsinki, University of Helsinki, Haartmaninkatu 8, Helsinki 00290, Finland
| | - Thomas G. McWilliams
- Translational Stem Cell Biology and Metabolism Program, Research Programs Unit, Faculty of Medicine, Biomedicum Helsinki, University of Helsinki, Haartmaninkatu 8, Helsinki 00290, Finland
- Department of Anatomy, Faculty of Medicine, Biomedicum Helsinki, University of Helsinki, Haartmaninkatu 8, Helsinki 00290, Finland
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7
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Hui KK, Takashima N, Watanabe A, Chater TE, Matsukawa H, Nekooki-Machida Y, Nilsson P, Endo R, Goda Y, Saido TC, Yoshikawa T, Tanaka M. GABARAPs dysfunction by autophagy deficiency in adolescent brain impairs GABA A receptor trafficking and social behavior. SCIENCE ADVANCES 2019; 5:eaau8237. [PMID: 30989111 PMCID: PMC6457945 DOI: 10.1126/sciadv.aau8237] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Accepted: 02/20/2019] [Indexed: 05/02/2023]
Abstract
Dysfunctional mTOR signaling is associated with the pathogenesis of neurodevelopmental and neuropsychiatric disorders. However, it is unclear what molecular mechanisms and pathogenic mediators are involved and whether mTOR-regulated autophagy continues to be crucial beyond neurodevelopment. Here, we selectively deleted Atg7 in forebrain GABAergic interneurons in adolescent mice and unexpectedly found that these mice showed a set of behavioral deficits similar to Atg7 deletion in forebrain excitatory neurons. By unbiased quantitative proteomic analysis, we identified γ-aminobutyric acid receptor-associated protein-like 2 (GABARAPL2) to differentially form high-molecular weight species in autophagy-deficient brains. Further functional analyses revealed a novel pathogenic mechanism involving the p62-dependent sequestration of GABARAP family proteins, leading to the reduction of surface GABAA receptor levels. Our work demonstrates a novel physiological role for autophagy in regulating GABA signaling beyond postnatal neurodevelopment, providing a potential mechanism for the reduced inhibitory inputs observed in neurodevelopmental and neuropsychiatric disorders with mTOR hyperactivation.
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Affiliation(s)
- Kelvin K. Hui
- Laboratory for Protein Conformation Diseases, RIKEN Center for Brain Science, Wako, Saitama 351-0198, Japan
| | - Noriko Takashima
- Laboratory for Protein Conformation Diseases, RIKEN Center for Brain Science, Wako, Saitama 351-0198, Japan
| | - Akiko Watanabe
- Laboratory for Molecular Psychiatry, RIKEN Center for Brain Science, Wako, Saitama 351-0198, Japan
| | - Thomas E. Chater
- Laboratory for Synaptic Plasticity and Connectivity, RIKEN Center for Brain Science, Wako, Saitama 351-0198, Japan
| | - Hiroshi Matsukawa
- Laboratory for Protein Conformation Diseases, RIKEN Center for Brain Science, Wako, Saitama 351-0198, Japan
- Laboratory for Behavioral Genetics, RIKEN Center for Brain Science, Wako, Saitama 351-0198, Japan
| | - Yoko Nekooki-Machida
- Laboratory for Protein Conformation Diseases, RIKEN Center for Brain Science, Wako, Saitama 351-0198, Japan
| | - Per Nilsson
- Laboratory for Proteolytic Neuroscience, RIKEN Center for Brain Science, Wako, Saitama 351-0198, Japan
- Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, Huddinge 141 57, Sweden
| | - Ryo Endo
- Laboratory for Protein Conformation Diseases, RIKEN Center for Brain Science, Wako, Saitama 351-0198, Japan
| | - Yukiko Goda
- Laboratory for Synaptic Plasticity and Connectivity, RIKEN Center for Brain Science, Wako, Saitama 351-0198, Japan
| | - Takaomi C. Saido
- Laboratory for Proteolytic Neuroscience, RIKEN Center for Brain Science, Wako, Saitama 351-0198, Japan
| | - Takeo Yoshikawa
- Laboratory for Molecular Psychiatry, RIKEN Center for Brain Science, Wako, Saitama 351-0198, Japan
| | - Motomasa Tanaka
- Laboratory for Protein Conformation Diseases, RIKEN Center for Brain Science, Wako, Saitama 351-0198, Japan
- Corresponding author.
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8
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Li K, Chen HS, Li D, Li HH, Wang J, Jia L, Wu PF, Long LH, Hu ZL, Chen JG, Wang F. SAR405, a Highly Specific VPS34 Inhibitor, Disrupts Auditory Fear Memory Consolidation of Mice via Facilitation of Inhibitory Neurotransmission in Basolateral Amygdala. Biol Psychiatry 2019; 85:214-225. [PMID: 30253884 DOI: 10.1016/j.biopsych.2018.07.026] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Revised: 07/18/2018] [Accepted: 07/29/2018] [Indexed: 12/20/2022]
Abstract
BACKGROUND Autophagy has been demonstrated to play an important role in memory deficits as well as the degradation of neurotransmitter receptors. SAR405 is a newly discovered inhibitor that can specifically inhibit vacuolar sorting protein 34 and prevent autophagosome biogenesis. However, the effects of SAR405 on memory processes remain largely unknown. METHODS Western blotting, immunofluorescence, and transmission electron microscopy were used to assess the level of autophagy after fear conditioning and SAR405 treatment. Behavioral tests, biotinylation assay, electrophysiology, and co-immunoprecipitation were used to unravel the mechanisms of SAR405 in memory consolidation. RESULTS SAR405 infusion into the basolateral amygdala impaired long-term memory through autophagy inhibition. Furthermore, the trafficking of gamma-aminobutyric acid type A receptors (GABAARs) following fear conditioning was disrupted by SAR405, and the decreased frequency and amplitude of miniature inhibitory postsynaptic currents induced by fear conditioning were also reversed by SAR405, suggesting that SAR405 disrupted memory consolidation through blockade of the downregulated inhibitory neurotransmission in basolateral amygdala. GABAAR-associated protein (GABARAP) and its interaction with GABAAR γ2 subunit were found to be upregulated after fear conditioning, and SAR405 could suppress this increased interaction. Moreover, disruption of the GABARAP-GABAAR binding by a trans-activating transcriptional activator-GABARAP inhibitory peptide blocked the decrease in surface expression of GABAARs and attenuated long-term memory. CONCLUSIONS The present study suggests that SAR405 can prevent the memory consolidation via intervening autophagy and GABAAR trafficking and has a potential therapeutic value for disorders characterized by exaggerated fear memories, such as posttraumatic stress disorder.
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Affiliation(s)
- Kuan Li
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Hong-Sheng Chen
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Di Li
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Hou-Hong Li
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Ji Wang
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Lei Jia
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Peng-Fei Wu
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China; Laboratory of Neuropsychiatric Diseases, the Institute of Brain Research, Huazhong University of Science and Technology, Wuhan, China; Key Laboratory for Drug Target Researches and Pharmacodynamic Evaluation of Hubei Province, Wuhan, China
| | - Li-Hong Long
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China; Laboratory of Neuropsychiatric Diseases, the Institute of Brain Research, Huazhong University of Science and Technology, Wuhan, China; Key Laboratory of Neurological Diseases, Ministry of Education of China, Wuhan, China; Key Laboratory for Drug Target Researches and Pharmacodynamic Evaluation of Hubei Province, Wuhan, China
| | - Zhuang-Li Hu
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China; Laboratory of Neuropsychiatric Diseases, the Institute of Brain Research, Huazhong University of Science and Technology, Wuhan, China; Key Laboratory for Drug Target Researches and Pharmacodynamic Evaluation of Hubei Province, Wuhan, China
| | - Jian-Guo Chen
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China; Laboratory of Neuropsychiatric Diseases, the Institute of Brain Research, Huazhong University of Science and Technology, Wuhan, China; Key Laboratory of Neurological Diseases, Ministry of Education of China, Wuhan, China; Key Laboratory for Drug Target Researches and Pharmacodynamic Evaluation of Hubei Province, Wuhan, China; Collaborative Innovation Center for Brain Science, Wuhan, China.
| | - Fang Wang
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China; Laboratory of Neuropsychiatric Diseases, the Institute of Brain Research, Huazhong University of Science and Technology, Wuhan, China; Key Laboratory of Neurological Diseases, Ministry of Education of China, Wuhan, China; Key Laboratory for Drug Target Researches and Pharmacodynamic Evaluation of Hubei Province, Wuhan, China; Collaborative Innovation Center for Brain Science, Wuhan, China.
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9
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Fan J, Li D, Chen HS, Huang JG, Xu JF, Zhu WW, Chen JG, Wang F. Metformin produces anxiolytic-like effects in rats by facilitating GABA A receptor trafficking to membrane. Br J Pharmacol 2018; 176:297-316. [PMID: 30318707 DOI: 10.1111/bph.14519] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2018] [Revised: 09/15/2018] [Accepted: 09/19/2018] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND AND PURPOSE Altered function or expression of GABAA receptors contributes to anxiety disorders. Benzodiazepines are widely prescribed for the treatment of anxiety. However, the long-term use of benzodiazepines increases the risk of developing drug dependence and tolerance. Thus, it is urgent to explore new therapeutic approaches. Metformin is widely used to treat Type 2 diabetes and other metabolic syndromes. However, the role of metformin in psychiatric disorders, especially anxiety, remains largely unknown. EXPERIMENTAL APPROACH We examined the effects of metformin on anxiety-like behaviour of rats in open field test and elevated plus maze test. We also observed the effect of metformin (10 μM, in vitro; 100 mg·kg-1 , in vivo) on the trafficking of GABAA receptors, as mechanisms underlying the anxiolytic effects of metformin. KEY RESULTS Metformin (100 mg·kg-1 , i.p. 30 min) displayed a robust and rapid anxiolytic effect, without tolerance. Metformin up-regulated the surface expression of GABAA receptors and increased miniature inhibitory postsynaptic currents (mIPSCs). AMP-activated protein kinase (AMPK) activated by metformin-induced stimulation of forkhead box O3a (FoxO3a) transcriptional activity, followed by increased expression of GABAA receptor-associated protein (GABARAP) and its binding to GABAA receptors finally resulted in the membrane insertion of GABAA receptors. CONCLUSIONS AND IMPLICATIONS Metformin increased mIPSCs by up-regulating the membrane insertion of GABAA receptors, via a pathway involving AMPK, FoxO3a, and the GABAA receptor-associated protein. Thus metformin has a potential new use in the treatment of anxiety disorders.
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Affiliation(s)
- Jun Fan
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Di Li
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Hong-Sheng Chen
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Jian-Geng Huang
- Department of Pharmaceutics, School of Pharmacy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Jun-Feng Xu
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Wen-Wen Zhu
- Department of Pharmaceutics, School of Pharmacy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Jian-Guo Chen
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.,The Key Laboratory of Neurological Diseases (HUST), Ministry of Education of China, Wuhan, China.,Hubei Key Laboratory of Drug Target Research and Pharmacodynamic Evaluation (HUST), Wuhan, China.,Laboratory of Neuropsychiatric Diseases, The Institute of Brain Research, Huazhong University of Science and Technology, Wuhan, China.,The Collaborative-Innovation Center for Brain Science, Wuhan, China
| | - Fang Wang
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.,The Key Laboratory of Neurological Diseases (HUST), Ministry of Education of China, Wuhan, China.,Hubei Key Laboratory of Drug Target Research and Pharmacodynamic Evaluation (HUST), Wuhan, China.,Laboratory of Neuropsychiatric Diseases, The Institute of Brain Research, Huazhong University of Science and Technology, Wuhan, China.,The Collaborative-Innovation Center for Brain Science, Wuhan, China
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10
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Lorenz-Guertin JM, Bambino MJ, Jacob TC. γ2 GABA AR Trafficking and the Consequences of Human Genetic Variation. Front Cell Neurosci 2018; 12:265. [PMID: 30190672 PMCID: PMC6116786 DOI: 10.3389/fncel.2018.00265] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Accepted: 08/02/2018] [Indexed: 11/13/2022] Open
Abstract
GABA type A receptors (GABAARs) mediate the majority of fast inhibitory neurotransmission in the central nervous system (CNS). Most prevalent as heteropentamers composed of two α, two β, and a γ2 subunit, these ligand-gated ionotropic chloride channels are capable of extensive genetic diversity (α1-6, β1-3, γ1-3, δ, 𝜀, 𝜃, π, ρ1-3). Part of this selective GABAAR assembly arises from the critical role for γ2 in maintaining synaptic receptor localization and function. Accordingly, mutations in this subunit account for over half of the known epilepsy-associated genetic anomalies identified in GABAARs. Fundamental structure-function studies and cellular pathology investigations have revealed dynamic GABAAR trafficking and synaptic scaffolding as critical regulators of GABAergic inhibition. Here, we introduce in vitro and in vivo findings regarding the specific role of the γ2 subunit in receptor trafficking. We then examine γ2 subunit human genetic variation and assess disease related phenotypes and the potential role of altered GABAAR trafficking. Finally, we discuss new-age imaging techniques and their potential to provide novel insight into critical regulatory mechanisms of GABAAR function.
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Affiliation(s)
- Joshua M Lorenz-Guertin
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, United States
| | - Matthew J Bambino
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, United States
| | - Tija C Jacob
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, United States
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11
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Lorenz-Guertin JM, Jacob TC. GABA type a receptor trafficking and the architecture of synaptic inhibition. Dev Neurobiol 2018; 78:238-270. [PMID: 28901728 PMCID: PMC6589839 DOI: 10.1002/dneu.22536] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 09/08/2017] [Accepted: 09/08/2017] [Indexed: 12/21/2022]
Abstract
Ubiquitous expression of GABA type A receptors (GABAA R) in the central nervous system establishes their central role in coordinating most aspects of neural function and development. Dysregulation of GABAergic neurotransmission manifests in a number of human health disorders and conditions that in certain cases can be alleviated by drugs targeting these receptors. Precise changes in the quantity or activity of GABAA Rs localized at the cell surface and at GABAergic postsynaptic sites directly impact the strength of inhibition. The molecular mechanisms constituting receptor trafficking to and from these compartments therefore dictate the efficacy of GABAA R function. Here we review the current understanding of how GABAA Rs traffic through biogenesis, plasma membrane transport, and degradation. Emphasis is placed on discussing novel GABAergic synaptic proteins, receptor and scaffolding post-translational modifications, activity-dependent changes in GABAA R confinement, and neuropeptide and neurosteroid mediated changes. We further highlight modern techniques currently advancing the knowledge of GABAA R trafficking and clinically relevant neurodevelopmental diseases connected to GABAergic dysfunction. © 2017 Wiley Periodicals, Inc. Develop Neurobiol 78: 238-270, 2018.
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Affiliation(s)
- Joshua M Lorenz-Guertin
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, 15261
| | - Tija C Jacob
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, 15261
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12
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Abstract
Discovery of yeast autophagy-related (ATG) genes and subsequent identification of their homologs in other organisms have enabled researchers to investigate physiological functions of macroautophagy/autophagy using genetic techniques. Specific identification of autophagy-related structures is important to evaluate autophagic activity, and specific ablation of autophagy-related genes is a critical means to determine the requirements of autophagy. Here, we review currently available mouse models, particularly focusing on autophagy (and mitophagy) indicator models and systemic autophagy-related gene-knockout mouse models.
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Affiliation(s)
- Akiko Kuma
- Department of Biochemistry and Molecular Biology, Graduate School and Faculty of Medicine, The University of Tokyo, Tokyo, Japan
- Division of Cancer Biology, National Cancer Center Research Institute, Tokyo, Japan
- CONTACT Akiko Kuma Division of Cancer Biology, National Cancer Center Research Institute, 5-1-1 Tsukiji Chuo-ku, Tokyo 104-0045 Japan
| | - Masaaki Komatsu
- Department of Biochemistry, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Noboru Mizushima
- Department of Biochemistry and Molecular Biology, Graduate School and Faculty of Medicine, The University of Tokyo, Tokyo, Japan
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13
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Vien TN, Moss SJ, Davies PA. Regulating the Efficacy of Inhibition Through Trafficking of γ-Aminobutyric Acid Type A Receptors. Anesth Analg 2017; 123:1220-1227. [PMID: 27285004 DOI: 10.1213/ane.0000000000001349] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Trafficking of anesthetic-sensitive receptors within the plasma membrane, or from one cellular component to another, occurs continuously. Changes in receptor trafficking have implications in altering anesthetic sensitivity. γ-Aminobutyric acid type A receptors (GABAARs) are anion-permeable ion channels and are the major class of receptor in the adult mammalian central nervous system that mediates inhibition. GABAergic signaling allows for precise synchronized firing of action potentials within brain circuits that is critical for cognition, behavior, and consciousness. This precision depends upon tightly controlled trafficking of GABAARs into the membrane. General anesthetics bind to and allosterically enhance GABAARs by prolonging the open state of the receptor and thereby altering neuronal and brain circuit activity. Subunit composition and GABAAR localization strongly influence anesthetic end points; therefore, changes in GABAAR trafficking could have significant consequences to anesthetic sensitivity. GABAARs are not static membrane structures but are in a constant state of flux between extrasynaptic and synaptic locations and are continually endocytosed and recycled from and to the membrane. Neuronal activity, posttranslational modifications, and some naturally occurring and synthetic compounds can influence the expression and trafficking of GABAARs. In this article, we review GABAARs, their trafficking, and how phosphorylation of GABAAR subunits can influence the surface expression and function of the receptor. Ultimately, alterations of GABAAR trafficking could modify anesthetic end points, both unintentionally through pathologic processes but potentially as a therapeutic target to adjust anesthetic-sensitive GABAARs.
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Affiliation(s)
- Thuy N Vien
- From the *Department of Neuroscience, Tufts University School of Medicine, Sackler School of Graduate Biomedical Sciences, Boston, Massachusetts; and †Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts
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14
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Keulers TG, Schaaf MBE, Rouschop KMA. Autophagy-Dependent Secretion: Contribution to Tumor Progression. Front Oncol 2016; 6:251. [PMID: 27933272 PMCID: PMC5122571 DOI: 10.3389/fonc.2016.00251] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2016] [Accepted: 11/10/2016] [Indexed: 12/14/2022] Open
Abstract
Autophagy is best known as a lysosomal degradation and recycling pathway to maintain cellular homeostasis. During autophagy, cytoplasmic content is recognized and packed in autophagic vacuoles, or autophagosomes, and targeted for degradation. However, during the last years, it has become evident that the role of autophagy is not restricted to degradation alone but also mediates unconventional forms of secretion. Furthermore, cells with defects in autophagy apparently are able to reroute their cargo, like mitochondria, to the extracellular environment; effects that contribute to an array of pathologies. In this review, we discuss the current knowledge of the physiological roles of autophagy-dependent secretion, i.e., the effect on inflammation and insulin/hormone secretion. Finally, we focus on the effects of autophagy-dependent secretion on the tumor microenvironment (TME) and tumor progression. The autophagy-mediated secreted factors may stimulate cellular proliferation via auto- and paracrine signaling. The autophagy-mediated release of immune modulating proteins changes the immunosuppresive TME and may promote an invasive phenotype. These effects may be either direct or indirect through facilitating formation of the mobilized vesicle, aid in anterograde trafficking, or alterations in homeostasis and/or autonomous cell signaling.
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Affiliation(s)
- Tom G Keulers
- Maastricht Radiation Oncology (MaastRO) Lab, GROW - School for Oncology and Developmental Biology, Maastricht University Medical Center , Maastricht , Netherlands
| | - Marco B E Schaaf
- Cell Death Research and Therapy (CDRT) Laboratory, Department Cellular and Molecular Medicine, KU Leuven, University of Leuven , Leuven , Belgium
| | - Kasper M A Rouschop
- Maastricht Radiation Oncology (MaastRO) Lab, GROW - School for Oncology and Developmental Biology, Maastricht University Medical Center , Maastricht , Netherlands
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15
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Autophagy in kidney disease and aging: lessons from rodent models. Kidney Int 2016; 90:950-964. [DOI: 10.1016/j.kint.2016.04.014] [Citation(s) in RCA: 96] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2015] [Revised: 04/17/2016] [Accepted: 04/20/2016] [Indexed: 12/14/2022]
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16
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Schaaf MBE, Keulers TG, Vooijs MA, Rouschop KMA. LC3/GABARAP family proteins: autophagy-(un)related functions. FASEB J 2016; 30:3961-3978. [PMID: 27601442 DOI: 10.1096/fj.201600698r] [Citation(s) in RCA: 399] [Impact Index Per Article: 49.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Accepted: 08/22/2016] [Indexed: 01/01/2023]
Abstract
From yeast to mammals, autophagy is an important mechanism for sustaining cellular homeostasis through facilitating the degradation and recycling of aged and cytotoxic components. During autophagy, cargo is captured in double-membraned vesicles, the autophagosomes, and degraded through lysosomal fusion. In yeast, autophagy initiation, cargo recognition, cargo engulfment, and vesicle closure is Atg8 dependent. In higher eukaryotes, Atg8 has evolved into the LC3/GABARAP protein family, consisting of 7 family proteins [LC3A (2 splice variants), LC3B, LC3C, GABARAP, GABARAPL1, and GABARAPL2]. LC3B, the most studied family protein, is associated with autophagosome development and maturation and is used to monitor autophagic activity. Given the high homology, the other LC3/GABARAP family proteins are often presumed to fulfill similar functions. Nevertheless, substantial evidence shows that the LC3/GABARAP family proteins are unique in function and important in autophagy-independent mechanisms. In this review, we discuss the current knowledge and functions of the LC3/GABARAP family proteins. We focus on processing of the individual family proteins and their role in autophagy initiation, cargo recognition, vesicle closure, and trafficking, a complex and tightly regulated process that requires selective presentation and recruitment of these family proteins. In addition, functions unrelated to autophagy of the LC3/GABARAP protein family members are discussed.-Schaaf, M. B. E., Keulers, T. G, Vooijs, M. A., Rouschop, K. M. A. LC3/GABARAP family proteins: autophagy-(un)related functions.
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Affiliation(s)
- Marco B E Schaaf
- Department of Radiation Oncology (Maastro Lab), GROW School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Tom G Keulers
- Department of Radiation Oncology (Maastro Lab), GROW School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Marc A Vooijs
- Department of Radiation Oncology (Maastro Lab), GROW School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Kasper M A Rouschop
- Department of Radiation Oncology (Maastro Lab), GROW School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands
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17
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Characterization of the γ-aminobutyric acid signaling system in the zebrafish (Danio rerio Hamilton) central nervous system by reverse transcription-quantitative polymerase chain reaction. Neuroscience 2016; 343:300-321. [PMID: 27453477 DOI: 10.1016/j.neuroscience.2016.07.018] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2016] [Revised: 07/11/2016] [Accepted: 07/11/2016] [Indexed: 11/20/2022]
Abstract
In the vertebrate brain, inhibition is largely mediated by γ-aminobutyric acid (GABA). This neurotransmitter comprises a signaling machinery of GABAA, GABAB receptors, transporters, glutamate decarboxylases (gads) and 4-aminobutyrate aminotransferase (abat), and associated proteins. Chloride is intimately related to GABAA receptor conductance, GABA uptake, and GADs activity. The response of target neurons to GABA stimuli is shaped by chloride-cation co-transporters (CCCs), which strictly control Cl- gradient across plasma membranes. This research profiled the expression of forty genes involved in GABA signaling in the zebrafish (Danio rerio) brain, grouped brain regions and retinas. Primer pairs were developed for reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The mRNA levels of the zebrafish GABA system share similarities with that of mammals, and confirm previous studies in non-mammalian species. Proposed GABAA receptors are α1β2γ2, α1β2δ, α2bβ3γ2, α2bβ3δ, α4β2γ2, α4β2δ, α6bβ2γ2 and α6bβ2δ. Regional brain differences were documented. Retinal hetero- or homomeric ρ-composed GABAA receptors could exist, accompanying α1βyγ2, α1βyδ, α6aβyγ2, α6aβyδ. Expression patterns of α6a and α6b were opposite, with the former being more abundant in retinas, the latter in brains. Given the stoichiometry α6wβyγz, α6a- or α6b-containing receptors likely have different regulatory mechanisms. Different gene isoforms could originate after the rounds of genome duplication during teleost evolution. This research depicts that one isoform is generally more abundantly expressed than the other. Such observations also apply to GABAB receptors, GABA transporters, GABA-related enzymes, CCCs and GABAA receptor-associated proteins, whose presence further strengthens the proof of a GABA system in zebrafish.
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18
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Salah FS, Ebbinghaus M, Muley VY, Zhou Z, Al-Saadi KRD, Pacyna-Gengelbach M, O'Sullivan GA, Betz H, König R, Wang ZQ, Bräuer R, Petersen I. Tumor suppression in mice lacking GABARAP, an Atg8/LC3 family member implicated in autophagy, is associated with alterations in cytokine secretion and cell death. Cell Death Dis 2016; 7:e2205. [PMID: 27124579 PMCID: PMC4855672 DOI: 10.1038/cddis.2016.93] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2015] [Revised: 03/11/2016] [Accepted: 03/15/2016] [Indexed: 01/04/2023]
Abstract
GABARAP belongs to an evolutionary highly conserved gene family that has a fundamental role in autophagy. There is ample evidence for a crosstalk between autophagy and apoptosis as well as the immune response. However, the molecular details for these interactions are not fully characterized. Here, we report that the ablation of murine GABARAP, a member of the Atg8/LC3 family that is central to autophagosome formation, suppresses the incidence of tumor formation mediated by the carcinogen DMBA and results in an enhancement of the immune response through increased secretion of IL-1β, IL-6, IL-2 and IFN-γ from stimulated macrophages and lymphocytes. In contrast, TGF-β1 was significantly reduced in the serum of these knockout mice. Further, DMBA treatment of these GABARAP knockout mice reduced the cellularity of the spleen and the growth of mammary glands through the induction of apoptosis. Gene expression profiling of mammary glands revealed significantly elevated levels of Xaf1, an apoptotic inducer and tumor-suppressor gene, in knockout mice. Furthermore, DMBA treatment triggered the upregulation of pro-apoptotic (Bid, Apaf1, Bax), cell death (Tnfrsf10b, Ripk1) and cell cycle inhibitor (Cdkn1a, Cdkn2c) genes in the mammary glands. Finally, tumor growth of B16 melanoma cells after subcutaneous inoculation was inhibited in GABARAP-deficient mice. Together, these data provide strong evidence for the involvement of GABARAP in tumorigenesis in vivo by delaying cell death and its associated immune-related response.
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Affiliation(s)
- F S Salah
- Institute of Pathology, University Hospital - Friedrich Schiller University Jena, Ziegelmühlenweg 1, Jena D-07743, Germany.,Iraqi Centre for Cancer and Medical Genetics Research, Al-Mustansiriya University, Baghdad, Iraq
| | - M Ebbinghaus
- Institute of Physiology 1, University Hospital - Friedrich Schiller University Jena, Teichgraben 8, Jena D-07743, Germany
| | - V Y Muley
- Leibniz Institute for Natural Product Research and Infection Biology, Hans Knöll Institute (HKI), Beutenbergstrasse 11, Jena D-07745, Germany.,Integrated Research and Treatment Center, Center for Sepsis Control and Care (CSCC), Jena University Hospital, Erlanger Allee 101, Jena D-07747, Germany
| | - Z Zhou
- Leibniz Institute for Age Research - Fritz Lipmann Institute (FLI), Beutenbergstrasse 11, Jena D-07745, Germany
| | - K R D Al-Saadi
- Iraqi Centre for Cancer and Medical Genetics Research, Al-Mustansiriya University, Baghdad, Iraq
| | - M Pacyna-Gengelbach
- Institute of Pathology, University Medicine Berlin, Campus Charité Mitte, Berlin D-10098, Germany
| | - G A O'Sullivan
- Department of Neurochemistry, Max-Planck Institute for Brain Research, Deutschordenstrasse 46, Frankfurt D-60528, Germany
| | - H Betz
- Department of Neurochemistry, Max-Planck Institute for Brain Research, Deutschordenstrasse 46, Frankfurt D-60528, Germany.,Max-Planck Institute for Medical Research, Jahnstrasse 29, Heidelberg D-69120, Germany
| | - R König
- Leibniz Institute for Natural Product Research and Infection Biology, Hans Knöll Institute (HKI), Beutenbergstrasse 11, Jena D-07745, Germany.,Integrated Research and Treatment Center, Center for Sepsis Control and Care (CSCC), Jena University Hospital, Erlanger Allee 101, Jena D-07747, Germany
| | - Z-Q Wang
- Leibniz Institute for Age Research - Fritz Lipmann Institute (FLI), Beutenbergstrasse 11, Jena D-07745, Germany.,Faculty of Biology and Pharmacy, Friedrich Schiller University Jena, Bachstrasse 18k, Jena D-07743, Germany
| | - R Bräuer
- Institute of Pathology, University Hospital - Friedrich Schiller University Jena, Ziegelmühlenweg 1, Jena D-07743, Germany
| | - I Petersen
- Institute of Pathology, University Hospital - Friedrich Schiller University Jena, Ziegelmühlenweg 1, Jena D-07743, Germany
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19
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Choii G, Ko J. Gephyrin: a central GABAergic synapse organizer. Exp Mol Med 2015; 47:e158. [PMID: 25882190 DOI: 10.1038/emm.2015.5] [Citation(s) in RCA: 91] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2014] [Accepted: 12/18/2014] [Indexed: 01/22/2023] Open
Abstract
Gephyrin is a central element that anchors, clusters and stabilizes glycine and γ-aminobutyric acid type A receptors at inhibitory synapses of the mammalian brain. It self-assembles into a hexagonal lattice and interacts with various inhibitory synaptic proteins. Intriguingly, the clustering of gephyrin, which is regulated by multiple posttranslational modifications, is critical for inhibitory synapse formation and function. In this review, we summarize the basic properties of gephyrin and describe recent findings regarding its roles in inhibitory synapse formation, function and plasticity. We will also discuss the implications for the pathophysiology of brain disorders and raise the remaining open questions in this field.
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Affiliation(s)
- Gayoung Choii
- Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul, Korea
| | - Jaewon Ko
- 1] Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul, Korea [2] Department of Psychiatry, Yonsei University College of Medicine, Seoul, Korea
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20
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Giant ankyrin-G stabilizes somatodendritic GABAergic synapses through opposing endocytosis of GABAA receptors. Proc Natl Acad Sci U S A 2014; 112:1214-9. [PMID: 25552561 DOI: 10.1073/pnas.1417989112] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
GABAA-receptor-based interneuron circuitry is essential for higher order function of the human nervous system and is implicated in schizophrenia, depression, anxiety disorders, and autism. Here we demonstrate that giant ankyrin-G (480-kDa ankyrin-G) promotes stability of somatodendritic GABAergic synapses in vitro and in vivo. Moreover, giant ankyrin-G forms developmentally regulated and cell-type-specific micron-scale domains within extrasynaptic somatodendritic plasma membranes of pyramidal neurons. We further find that giant ankyrin-G promotes GABAergic synapse stability through opposing endocytosis of GABAA receptors, and requires a newly described interaction with GABARAP, a GABAA receptor-associated protein. We thus present a new mechanism for stabilization of GABAergic interneuron synapses and micron-scale organization of extrasynaptic membrane that provides a rationale for studies linking ankyrin-G genetic variation with psychiatric disease and abnormal neurodevelopment.
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21
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22
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Boyer-Guittaut M, Poillet L, Liang Q, Bôle-Richard E, Ouyang X, Benavides GA, Chakrama FZ, Fraichard A, Darley-Usmar VM, Despouy G, Jouvenot M, Delage-Mourroux R, Zhang J. The role of GABARAPL1/GEC1 in autophagic flux and mitochondrial quality control in MDA-MB-436 breast cancer cells. Autophagy 2014; 10:986-1003. [PMID: 24879149 PMCID: PMC4091181 DOI: 10.4161/auto.28390] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2013] [Revised: 02/18/2014] [Accepted: 02/28/2014] [Indexed: 12/14/2022] Open
Abstract
GABARAPL1/GEC1 is an early estrogen-induced gene which encodes a protein highly conserved from C. elegans to humans. Overexpressed GABARAPL1 interacts with GABAA or kappa opioid receptors, associates with autophagic vesicles, and inhibits breast cancer cell proliferation. However, the function of endogenous GABARAPL1 has not been extensively studied. We hypothesized that GABARAPL1 is required for maintaining normal autophagic flux, and plays an important role in regulating cellular bioenergetics and metabolism. To test this hypothesis, we knocked down GABARAPL1 expression in the breast cancer MDA-MB-436 cell line by shRNA. Decreased expression of GABARAPL1 activated procancer responses of the MDA-MB-436 cells including increased proliferation, colony formation, and invasion. In addition, cells with decreased expression of GABARAPL1 exhibited attenuated autophagic flux and a decreased number of lysosomes. Moreover, decreased GABARAPL1 expression led to cellular bioenergetic changes including increased basal oxygen consumption rate, increased intracellular ATP, increased total glutathione, and an accumulation of damaged mitochondria. Taken together, our results demonstrate that GABARAPL1 plays an important role in cell proliferation, invasion, and autophagic flux, as well as in mitochondrial homeostasis and cellular metabolic programs.
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MESH Headings
- Adaptor Proteins, Signal Transducing/antagonists & inhibitors
- Adaptor Proteins, Signal Transducing/genetics
- Adaptor Proteins, Signal Transducing/metabolism
- Aldehydes/pharmacology
- Apoptosis Regulatory Proteins/metabolism
- Autophagy/genetics
- Autophagy/physiology
- Beclin-1
- Breast Neoplasms/genetics
- Breast Neoplasms/metabolism
- Breast Neoplasms/pathology
- Cell Line, Tumor
- Cell Proliferation
- Cell Survival/drug effects
- DNA Damage
- DNA, Mitochondrial/genetics
- DNA, Mitochondrial/metabolism
- Energy Metabolism
- Female
- Gene Knockdown Techniques
- Humans
- Lysosomal Membrane Proteins/genetics
- Lysosomal Membrane Proteins/metabolism
- Lysosomes/metabolism
- Lysosomes/pathology
- Membrane Potential, Mitochondrial
- Membrane Proteins/metabolism
- Microtubule-Associated Proteins/antagonists & inhibitors
- Microtubule-Associated Proteins/genetics
- Microtubule-Associated Proteins/metabolism
- Mitophagy/genetics
- Mitophagy/physiology
- Neoplasm Invasiveness
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Neoplasm/genetics
- RNA, Neoplasm/metabolism
- RNA, Small Interfering/genetics
- Sequestosome-1 Protein
- Tumor Stem Cell Assay
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Affiliation(s)
- Michaël Boyer-Guittaut
- Université de Franche-Comté; Laboratoire de Biochimie; EA3922 Estrogènes; Expression Génique et Pathologies du Système Nerveux Central; Sciences et Techniques; Besançon, France
- Department of Pathology; University of Alabama at Birmingham; Birmingham, AL USA
- Center for Free Radical Biology; University of Alabama at Birmingham; Birmingham, AL USA
| | - Laura Poillet
- Université de Franche-Comté; Laboratoire de Biochimie; EA3922 Estrogènes; Expression Génique et Pathologies du Système Nerveux Central; Sciences et Techniques; Besançon, France
| | - Qiuli Liang
- Department of Pathology; University of Alabama at Birmingham; Birmingham, AL USA
- Center for Free Radical Biology; University of Alabama at Birmingham; Birmingham, AL USA
| | - Elodie Bôle-Richard
- Université de Franche-Comté; Laboratoire de Biochimie; EA3922 Estrogènes; Expression Génique et Pathologies du Système Nerveux Central; Sciences et Techniques; Besançon, France
| | - Xiaosen Ouyang
- Department of Pathology; University of Alabama at Birmingham; Birmingham, AL USA
- Center for Free Radical Biology; University of Alabama at Birmingham; Birmingham, AL USA
- Department of Veterans Affairs; Birmingham VA Medical Center; Birmingham, AL USA
| | - Gloria A Benavides
- Department of Pathology; University of Alabama at Birmingham; Birmingham, AL USA
- Center for Free Radical Biology; University of Alabama at Birmingham; Birmingham, AL USA
| | - Fatima-Zahra Chakrama
- Université de Franche-Comté; Laboratoire de Biochimie; EA3922 Estrogènes; Expression Génique et Pathologies du Système Nerveux Central; Sciences et Techniques; Besançon, France
| | - Annick Fraichard
- Université de Franche-Comté; Laboratoire de Biochimie; EA3922 Estrogènes; Expression Génique et Pathologies du Système Nerveux Central; Sciences et Techniques; Besançon, France
| | - Victor M Darley-Usmar
- Department of Pathology; University of Alabama at Birmingham; Birmingham, AL USA
- Center for Free Radical Biology; University of Alabama at Birmingham; Birmingham, AL USA
| | - Gilles Despouy
- Université de Franche-Comté; Laboratoire de Biochimie; EA3922 Estrogènes; Expression Génique et Pathologies du Système Nerveux Central; Sciences et Techniques; Besançon, France
| | - Michèle Jouvenot
- Université de Franche-Comté; Laboratoire de Biochimie; EA3922 Estrogènes; Expression Génique et Pathologies du Système Nerveux Central; Sciences et Techniques; Besançon, France
| | - Régis Delage-Mourroux
- Université de Franche-Comté; Laboratoire de Biochimie; EA3922 Estrogènes; Expression Génique et Pathologies du Système Nerveux Central; Sciences et Techniques; Besançon, France
| | - Jianhua Zhang
- Department of Pathology; University of Alabama at Birmingham; Birmingham, AL USA
- Center for Free Radical Biology; University of Alabama at Birmingham; Birmingham, AL USA
- Department of Veterans Affairs; Birmingham VA Medical Center; Birmingham, AL USA
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23
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Abstract
The neurotransmitters GABA and glycine mediate fast synaptic inhibition by activating ligand-gated chloride channels--namely, type A GABA (GABA(A)) and glycine receptors. Both types of receptors are anchored postsynaptically by gephyrin, which self-assembles into a scaffold and interacts with the cytoskeleton. Current research indicates that postsynaptic gephyrin clusters are dynamic assemblies that are held together and regulated by multiple protein-protein interactions. Moreover, post-translational modifications of gephyrin regulate the formation and plasticity of GABAergic synapses by altering the clustering properties of postsynaptic scaffolds and thereby the availability and function of receptors and other signalling molecules. Here, we discuss the formation and regulation of the gephyrin scaffold, its role in GABAergic and glycinergic synaptic function and the implications for the pathophysiology of brain disorders caused by abnormal inhibitory neurotransmission.
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24
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Le Grand JN, Bon K, Fraichard A, Zhang J, Jouvenot M, Risold PY, Boyer-Guittaut M, Delage-Mourroux R. Specific distribution of the autophagic protein GABARAPL1/GEC1 in the developing and adult mouse brain and identification of neuronal populations expressing GABARAPL1/GEC1. PLoS One 2013; 8:e63133. [PMID: 23690988 PMCID: PMC3655077 DOI: 10.1371/journal.pone.0063133] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2012] [Accepted: 03/27/2013] [Indexed: 12/19/2022] Open
Abstract
Macroautophagy is a highly conserved cellular degradation process, regulated by autophagy-related (atg) factors, in which a double membrane autophagosome engulfs cytoplasmic components to target them for degradation. In yeast, the Atg8 protein is indispensable for autophagosome formation. In mammals, this is complicated by the presence of six Atg8 homologues grouped into the GABARAP and MAP1LC3 subfamilies. Although these proteins share a high similarity, their transcript expression, regulation and protein interactions differ, suggesting they may display individual properties and specific functions. GABARAPL1/GEC1 is a member of the GABARAP subfamily and its mRNA is the most highly expressed Atg8 homologue in the central nervous system. Consequently, we performed an in depth study of GABARAPL1 distribution in the developing and adult murine brain. Our results show that GABARAPL1 brain expression is visible as early as embryonic day 11 and progressively increases to a maximum level in the adult. Immunohistochemical staining was detected in both fibers and immature neurons in embryos but was restrained to neurons in adult tissue. By E17, intense punctate-like structures were visible and these accumulated in cortical primary neurons treated with the autophagosome/lysosome fusion inhibitor Bafilomycin A1 (Baf A1), suggesting that they represent autophagosomes. Finally, GABARAPL1 expression was particularly intense in motoneurons in the embryo and in neurons involved in somatomotor and neuroendocrine functions in the adult, particularly in the substantia nigra pars compacta, a region affected in Parkinson's disease. Our study of cerebral GABARAPL1 protein expression provides insight into its role in the development and homeostasis of the mouse brain.
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Affiliation(s)
- Jaclyn Nicole Le Grand
- Université de Franche-Comté, Laboratoire de Biochimie, EA3922 Estrogènes, Expression Génique et Pathologies du Système Nerveux Central, SFR IBCT FED 4234, U.F.R. Sciences et Techniques, Besançon, Doubs, France
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Koike M, Tanida I, Nanao T, Tada N, Iwata JI, Ueno T, Kominami E, Uchiyama Y. Enrichment of GABARAP relative to LC3 in the axonal initial segments of neurons. PLoS One 2013; 8:e63568. [PMID: 23671684 PMCID: PMC3650058 DOI: 10.1371/journal.pone.0063568] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Accepted: 04/03/2013] [Indexed: 01/19/2023] Open
Abstract
GABAA receptor-associated protein (GABARAP) was initially identified as a protein that interacts with GABAA receptor. Although LC3 (microtubule-associated protein 1 light chain 3), a GABARAP homolog, has been localized in the dendrites and cell bodies of neurons under normal conditions, the subcellular distribution of GABARAP in neurons remains unclear. Subcellular fractionation indicated that endogenous GABARAP was localized to the microsome-enriched and synaptic vesicle-enriched fractions of mouse brain as GABARAP-I, an unlipidated form. To investigate the distribution of GABARAP in neurons, we generated GFP-GABARAP transgenic mice. Immunohistochemistry in these transgenic mice showed that positive signals for GFP-GABARAP were widely distributed in neurons in various brain regions, including the hippocampus and cerebellum. Interestingly, intense diffuse and/or fibrillary expression of GFP-GABARAP was detected along the axonal initial segments (AIS) of hippocampal pyramidal neurons and cerebellar Purkinje cells, in addition to the cell bodies and dendrites of these neurons. In contrast, only slight amounts of LC3 were detected along the AIS of these neurons, while diffuse and/or fibrillary staining for LC3 was mainly detected in their cell bodies and dendrites. These results indicated that, compared with LC3, GABARAP is enriched in the AIS, in addition to the cell bodies and dendrites, of these hippocampal pyramidal neurons and cerebellar Purkinje cells.
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Affiliation(s)
- Masato Koike
- Department of Cell Biology and Neuroscience, Juntendo University School of Medicine, Tokyo, Japan
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Zhang Z, Xu X, Ma J, Wu J, Wang Y, Zhou R, Han J. Gene deletion of Gabarap enhances Nlrp3 inflammasome-dependent inflammatory responses. THE JOURNAL OF IMMUNOLOGY 2013; 190:3517-24. [PMID: 23427251 DOI: 10.4049/jimmunol.1202628] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The γ-aminobutyric acid A receptor-associated protein (Gabarap) functions in γ-aminobutyric acid A receptor trafficking and postsynaptic localization in neurons, but its physiological roles in other systems have not been studied. In this study, we report that Gabarap-deficient mice are more susceptible to mortality in two sepsis models. An underlying mechanism of this higher mortality rate in Gabarap(-/-) septic mice is the higher level of proinflammatory cytokine expression in Gabarap(-/-) mice versus wild-type mice. In vitro studies show that Nlrp3 inflammasome activation is enhanced by Gabarap deficiency, as evidenced by more casapse-1 activation, more IL-1β, and more IL-18 secretion in LPS- and ATP-treated Gabarap(-/-) macrophages. The Gabarap deficiency led to inefficient clearance of damaged mitochondria in LPS plus ATP-treated macrophages, resulting in more mitochondrial ROS and the release of mitochondrial DNA into cytosol. Both ROS and mitochondrial DNA are known to promote inflammasome activation. These results demonstrate that Gabarap functions in the immune system. It is involved in mitochondrial quality control in macrophages, and thus it influences Nlrp3 inflammasome-dependent inflammatory responses.
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Affiliation(s)
- Zhirong Zhang
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, 361005 Xiamen, Fujian, China
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Nakajima K, Yin X, Takei Y, Seog DH, Homma N, Hirokawa N. Molecular Motor KIF5A Is Essential for GABAA Receptor Transport, and KIF5A Deletion Causes Epilepsy. Neuron 2012; 76:945-61. [DOI: 10.1016/j.neuron.2012.10.012] [Citation(s) in RCA: 110] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/08/2012] [Indexed: 11/26/2022]
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Tretter V, Mukherjee J, Maric HM, Schindelin H, Sieghart W, Moss SJ. Gephyrin, the enigmatic organizer at GABAergic synapses. Front Cell Neurosci 2012; 6:23. [PMID: 22615685 PMCID: PMC3351755 DOI: 10.3389/fncel.2012.00023] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2011] [Accepted: 04/23/2012] [Indexed: 11/17/2022] Open
Abstract
GABAA receptors are clustered at synaptic sites to achieve a high density of postsynaptic receptors opposite the input axonal terminals. This allows for an efficient propagation of GABA mediated signals, which mostly result in neuronal inhibition. A key organizer for inhibitory synaptic receptors is the 93 kDa protein gephyrin that forms oligomeric superstructures beneath the synaptic area. Gephyrin has long been known to be directly associated with glycine receptor β subunits that mediate synaptic inhibition in the spinal cord. Recently, synaptic GABAA receptors have also been shown to directly interact with gephyrin and interaction sites have been identified and mapped within the intracellular loops of the GABAA receptor α1, α2, and α3 subunits. Gephyrin-binding to GABAA receptors seems to be at least one order of magnitude weaker than to glycine receptors (GlyRs) and most probably is regulated by phosphorylation. Gephyrin not only has a structural function at synaptic sites, but also plays a crucial role in synaptic dynamics and is a platform for multiple protein-protein interactions, bringing receptors, cytoskeletal proteins and downstream signaling proteins into close spatial proximity.
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Affiliation(s)
- Verena Tretter
- Department of Biochemistry and Molecular Biology, Center for Brain Research, Medical University Vienna Vienna, Austria
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Enoch MA, Zhou Z, Kimura M, Mash DC, Yuan Q, Goldman D. GABAergic gene expression in postmortem hippocampus from alcoholics and cocaine addicts; corresponding findings in alcohol-naïve P and NP rats. PLoS One 2012; 7:e29369. [PMID: 22253714 PMCID: PMC3258238 DOI: 10.1371/journal.pone.0029369] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Accepted: 11/27/2011] [Indexed: 01/02/2023] Open
Abstract
BACKGROUND By performing identical studies in humans and rats, we attempted to distinguish vulnerability factors for addiction from neurobiological effects of chronic drug exposure. We focused on the GABAergic system within the hippocampus, a brain region that is a constituent of the memory/conditioning neuronal circuitry of addiction that is considered to be important in drug reinforcement behaviors in animals and craving and relapse in humans. METHODOLOGY Using RNA-Seq we quantified mRNA transcripts in postmortem total hippocampus from alcoholics, cocaine addicts and controls and also from alcohol-naïve, alcohol preferring (P) and non-preferring (NP) rats selectively bred for extremes of alcohol-seeking behavior that also show a general addictive tendency. A pathway-targeted analysis of 25 GABAergic genes encoding proteins implicated in GABA synthesis, metabolism, synaptic transmission and re-uptake was undertaken. PRINCIPAL FINDINGS Directionally consistent and biologically plausible overlapping and specific changes were detected: 14/25 of the human genes and 12/25 of the rat genes showed nominally significant differences in gene expression (global p values: 9×10⁻¹⁴, 7×10⁻¹¹ respectively). Principal FDR-corrected findings were that GABBR1 was down-regulated in alcoholics, cocaine addicts and P rats with congruent findings in NSF, implicated in GABAB signaling efficacy, potentially resulting in increased synaptic GABA. GABRG2, encoding the gamma2 subunit required for postsynaptic clustering of GABAA receptors together with GPHN, encoding the associated scaffolding protein gephryin, were both down-regulated in alcoholics and cocaine addicts but were both up-regulated in P rats. There were also expression changes specific to cocaine addicts (GAD1, GAD2), alcoholics (GABRA2) and P rats (ABAT, GABRG3). CONCLUSIONS/SIGNIFICANCE Our study confirms the involvement of the GABAergic system in alcoholism but also reveals a hippocampal GABA input in cocaine addiction. Congruent findings in human addicts and P rats provide clues to predisposing factors for alcohol and drug addiction. Finally, the results of this study have therapeutic implications.
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Affiliation(s)
- Mary-Anne Enoch
- National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland, United States of America.
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Zhou Z, Wang L, Kong P, Qiu L, Zhang H, Gao Y, Yang J, Song L. A γ-aminobutyrate type A receptor-associated protein involved in the immune response of Eriocheir sinensis. Int J Immunogenet 2011; 39:46-54. [DOI: 10.1111/j.1744-313x.2011.01044.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Vithlani M, Terunuma M, Moss SJ. The dynamic modulation of GABA(A) receptor trafficking and its role in regulating the plasticity of inhibitory synapses. Physiol Rev 2011; 91:1009-22. [PMID: 21742794 DOI: 10.1152/physrev.00015.2010] [Citation(s) in RCA: 148] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Inhibition in the adult mammalian central nervous system (CNS) is mediated by γ-aminobutyric acid (GABA). The fast inhibitory actions of GABA are mediated by GABA type A receptors (GABA(A)Rs); they mediate both phasic and tonic inhibition in the brain and are the principle sites of action for anticonvulsant, anxiolytic, and sedative-hypnotic agents that include benzodiazepines, barbiturates, neurosteroids, and some general anesthetics. GABA(A)Rs are heteropentameric ligand-gated ion channels that are found concentrated at inhibitory postsynaptic sites where they mediate phasic inhibition and at extrasynaptic sites where they mediate tonic inhibition. The efficacy of inhibition and thus neuronal excitability is critically dependent on the accumulation of specific GABA(A)R subtypes at inhibitory synapses. Here we evaluate how neurons control the number of GABA(A)Rs on the neuronal plasma membrane together with their selective stabilization at synaptic sites. We then go on to examine the impact that these processes have on the strength of synaptic inhibition and behavior.
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Affiliation(s)
- Mansi Vithlani
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts, USA
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Luscher B, Fuchs T, Kilpatrick CL. GABAA receptor trafficking-mediated plasticity of inhibitory synapses. Neuron 2011; 70:385-409. [PMID: 21555068 DOI: 10.1016/j.neuron.2011.03.024] [Citation(s) in RCA: 316] [Impact Index Per Article: 24.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/30/2011] [Indexed: 12/22/2022]
Abstract
Proper developmental, neural cell-type-specific, and activity-dependent regulation of GABAergic transmission is essential for virtually all aspects of CNS function. The number of GABA(A) receptors in the postsynaptic membrane directly controls the efficacy of GABAergic synaptic transmission. Thus, regulated trafficking of GABA(A) receptors is essential for understanding brain function in both health and disease. Here we summarize recent progress in the understanding of mechanisms that allow dynamic adaptation of cell surface expression and postsynaptic accumulation and function of GABA(A) receptors. This includes activity-dependent and cell-type-specific changes in subunit gene expression, assembly of subunits into receptors, as well as exocytosis, endocytic recycling, diffusion dynamics, and degradation of GABA(A) receptors. In particular, we focus on the roles of receptor-interacting proteins, scaffold proteins, synaptic adhesion proteins, and enzymes that regulate the trafficking and function of receptors and associated proteins. In addition, we review neuropeptide signaling pathways that affect neural excitability through changes in GABA(A)R trafficking.
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Affiliation(s)
- Bernhard Luscher
- Department of Biology, Pennsylvania State University, University Park, PA 16802, USA.
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Fleming A, Rubinsztein DC. Zebrafish as a model to understand autophagy and its role in neurological disease. BIOCHIMICA ET BIOPHYSICA ACTA 2011; 1812:520-6. [PMID: 21256213 PMCID: PMC3060341 DOI: 10.1016/j.bbadis.2011.01.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/01/2009] [Revised: 11/10/2010] [Accepted: 01/03/2011] [Indexed: 12/16/2022]
Abstract
In the past decade, the zebrafish (Danio rerio) has become a popular model system for the study of vertebrate development, since the embryos and larvae of this species are small, transparent and undergo rapid development ex utero, allowing in vivo analysis of embryogenesis and organogenesis. These characteristics can also be exploited by researchers interested in signaling pathways and disease processes and, accordingly, there is a growing literature on the use of zebrafish to model human disease. This model holds great potential for exploring how autophagy, an evolutionarily conserved mechanism for protein degradation, influences the pathogeneses of a range of different human diseases and for the evaluation of this pathway as a potential therapeutic strategy. Here we summarize what is known about the regulation of autophagy in eukaryotic cells and its role in neurodegenerative disease and highlight how research using zebrafish has helped further our understanding of these processes.
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Affiliation(s)
- Angeleen Fleming
- Department of Medical Genetics, University of Cambridge, Cambridge Institute for Medical Research, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0XY, UK
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK
| | - David C. Rubinsztein
- Department of Medical Genetics, University of Cambridge, Cambridge Institute for Medical Research, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0XY, UK
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Chen C, Wang Y, Huang P, Liu-Chen LY. Effects of C-terminal modifications of GEC1 protein and gamma-aminobutyric acid type A (GABA(A)) receptor-associated protein (GABARAP), two microtubule-associated proteins, on kappa opioid receptor expression. J Biol Chem 2011; 286:15106-15. [PMID: 21388957 DOI: 10.1074/jbc.m111.230896] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
We demonstrated previously that GEC1, a member of the microtubule-associated protein (MAP) family, bound to the human κ opioid receptor (hKOPR) and promoted hKOPR cell surface expression by facilitating its trafficking along the secretory pathway. GABA(A) receptor-associated protein (GABARAP), a GEC1 analog, also enhanced KOPR expression, but to a lesser extent. The MAP family proteins undergo cleavage of their C-terminal residue(s), and the exposed conserved glycine forms conjugates with phosphatidylethanolamine, which associate with membranes. Here, we examined whether such modifications were required for GEC1 and GABARAP to enhance hKOPR expression. When transiently transfected into CHO or Neuro2A cells, GEC1 and GABARAP were cleaved at the C termini. G116A mutation alone or combined with deletion of Lys(117) in GEC1 (GEC1-A) or Leu(117) in GABARAP (GABARAP-A) blocked their C-terminal cleavage, indicating that the conserved Gly(116) is necessary for C-terminal modification. The two GEC1 mutants enhanced hKOPR expression to similar extents as the wild-type GEC1; however, the two GABARAP mutants did not. Immunofluorescence studies showed that HA-GEC1, HA-GEC1-A, and HA-GABARAP were distributed in a punctate manner and co-localized with KOPR-EGFP in the Golgi apparatus, whereas HA-GABARAP-A did not. Pulldown assay of GST-KOPR-C-tail with HA-GEC1 or HA-GABARAP revealed that GEC1 had stronger association with KOPR-C-tail than GABARAP. These results suggest that because of its stronger binding for hKOPR, GEC1 is able to be recruited by hKOPR sufficiently without membrane association via its C-terminal modification; however, due to its weaker affinity for the hKOPR, GABARAP appears to require C-terminal modifications to enhance KOPR expression.
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Affiliation(s)
- Chongguang Chen
- Department of Pharmacology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA
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Qian Z, Yakhnitsa V, Barmack NH. Climbing fiber-evoked Purkinje cell discharge reduces expression of GABA(A) receptor-associated protein and decreases its interaction with GABA(A) receptors. J Neurochem 2011; 117:197-208. [PMID: 21105873 DOI: 10.1111/j.1471-4159.2010.07119.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Sustained neuronal activity induces synaptic remodeling, in part, by altering gene expression. We have used a major climbing fiber pathway onto cerebellar Purkinje cells to investigate the effects of sustained climbing fiber-evoked glutamatergic synaptic transmission on transcription, expression and phosphorylation of proteins related to the regulation of inhibitory GABA(A) receptor function. Binocular horizontal optokinetic stimulation was used to modulate climbing fiber signals to Purkinje cells in the flocculus and nodulus of rabbits and mice. Purkinje cells in the flocculus and nodulus ipsilateral to the eye stimulated in the Posterior→Anterior direction received increased climbing fiber activity. Purkinje cells in flocculus and nodulus ipsilateral to the eye stimulated in the Anterior→Posterior direction received decreased climbing fiber activity. We identified changes in levels of gene transcripts in floccular and nodular Purkinje cells with the technique of differential display RT-PCR. Increased climbing fiber input reduced transcript levels and expression of GABA receptor-associated protein (GABARAP). Using a protein 'pull down' technique, we showed that GABARAP interacts with serine phosphorylated GABA(A)γ2, gephyrin and β-tubulin. Serine de-phosphorylation of GABA(A)γ2 reduced association of GABARAP with GABA(A)γ2. Climbing fiber activity did not influence the expression of GABA(A)γ2. Rather, it decreased its serine phosphorylation. Climbing fiber discharge decreased both expression of GABARAP and serine phosphorylation of GABA(A)γ2. Consequently, climbing fiber activity may reduce the surface expression of GABA(A) receptors in Purkinje cells rendering Purkinje cells less susceptible to interneuronal GABAergic inhibition.
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Affiliation(s)
- Zuyuan Qian
- Department of Physiology and Pharmacology, Oregon Health & Science University, Portland, Oregon 97239, USA.
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Abstract
It has been known for many decades that autophagy, a conserved lysosomal degradation pathway, is highly active during differentiation and development. However, until the discovery of the autophagy-related (ATG) genes in the 1990s, the functional significance of this activity was unknown. Initially, genetic knockout studies of ATG genes in lower eukaryotes revealed an essential role for the autophagy pathway in differentiation and development. In recent years, the analyses of systemic and tissue-specific knockout models of ATG genes in mice has led to an explosion of knowledge about the functions of autophagy in mammalian development and differentiation. Here we review the main advances in our understanding of these functions.
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Yu W, Charych EI, Serwanski DR, Li RW, Ali R, Bahr BA, De Blas AL. Gephyrin interacts with the glutamate receptor interacting protein 1 isoforms at GABAergic synapses. J Neurochem 2010; 105:2300-14. [PMID: 18315564 DOI: 10.1111/j.1471-4159.2008.05311.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
We have previously shown that the glutamate receptor interacting protein 1 (GRIP1) splice forms GRIP1a/b and GRIP1c4-7 are present at the GABAergic post-synaptic complex. Nevertheless, the role that these GRIP1 protein isoforms play at the GABAergic post-synaptic complex is not known. We are now showing that GRIP1c4-7 and GRIP1a/b interact with gephyrin, the main post-synaptic scaffold protein of GABAergic and glycinergic synapses. Gephyrin coprecipitates with GRIP1c4-7 or GRIP1a/b from rat brain extracts and from extracts of human embryonic kidney 293 cells that have been cotransfected with gephyrin and one of the GRIP1 protein isoforms. Moreover, purified gephyrin binds to purified GRIP1c4-7 or GRIP1a/b, indicating that gephyrin directly interacts with the common region of these GRIP1 proteins, which includes PDZ domains 4-7. An engineered deletion construct of GRIP1a/b (GRIP1a4-7), which both contains the aforementioned common region and binds to gephyrin, targets to the post-synaptic GABAergic complex of transfected cultured hippocampal neurons. In these hippocampal cultures, endogenous gephyrin colocalizes with endogenous GRIP1c4-7 and GRIP1a/b in over 90% of the GABAergic synapses. Double-labeling electron microscopy immunogold reveals that in the rat brain GRIP1c4-7 and GRIP1a/b colocalize with gephyrin at the post-synaptic complex of individual synapses. These results indicate that GRIP1c4-7 and GRIP1a/b colocalize and interact with gephyrin at the GABAergic post-synaptic complex and suggest that this interaction plays a role in GABAergic synaptic function.
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Affiliation(s)
- Wendou Yu
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut 06269-3156, USA
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Hernando N, Gisler SM, Reining SC, Déliot N, Capuano P, Biber J, Murer H. NaPi-IIa interacting proteins and regulation of renal reabsorption of phosphate. ACTA ACUST UNITED AC 2010; 38:271-6. [PMID: 20665015 DOI: 10.1007/s00240-010-0304-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2010] [Accepted: 07/08/2010] [Indexed: 11/29/2022]
Abstract
Control of phosphate (P(i)) homeostasis is essential for many biologic functions and inappropriate low levels of P(i) in plasma have been suggested to associate with several pathological states, including renal stone formation and stone recurrence. P(i) homeostasis is achieved mainly by adjusting the renal reabsorption of P(i) to the body's requirements. This task is performed to a major extent by the Na/Pi cotransporter NaPi-IIa that is specifically expressed in the brush border membrane of renal proximal tubules. While the presence of tight junctions in epithelial cells prevents the diffusion and mixing of the apical and basolateral components, the location of a protein within a particular membrane subdomain (i.e., the presence of NaPi-IIa at the tip of the apical microvilli) often requires its association with scaffolding elements which directly or indirectly connect the protein with the underlying cellular cytoskeleton. NaPi-IIa interacts with the four members of the Na(+)/H(+) exchanger regulatory factor family as well as with the GABA(A)-receptor associated protein . Here we will discuss the most relevant findings regarding the role of these proteins on the expression and regulation of the cotransporter, as well as the impact that their absence has in P(i) homeostasis.
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Affiliation(s)
- Nati Hernando
- Institute of Physiology and Zurich Center for Integrative Human Physiology (ZIHP), University of Zurich, Winterthurerstr. 190, 8057 Zurich, Switzerland.
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Reining SC, Liesegang A, Betz H, Biber J, Murer H, Hernando N. Expression of renal and intestinal Na/Pi cotransporters in the absence of GABARAP. Pflugers Arch 2010; 460:207-17. [PMID: 20354864 DOI: 10.1007/s00424-010-0832-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2009] [Revised: 03/12/2010] [Accepted: 03/17/2010] [Indexed: 12/20/2022]
Abstract
We have recently shown that the abundance of the renal sodium (Na)/inorganic phosphate (Pi) cotransporter NaPi-IIa is increased in the absence of the GABA(A) receptor-associated protein (GABARAP). Accordingly, GABARAP-deficient mice have a reduced urinary excretion of Pi. However, their circulating levels of Pi do not differ from wild-type animals, suggesting the presence of a compensatory mechanism responsible for keeping serum Pi values constant. Here, we aimed first to identify the molecular basis of this compensation by analyzing the expression of Na/Pi cotransporters known to be expressed in the kidney and intestine. We found that, in the kidney, the upregulation of NaPi-IIa is not accompanied by changes on the expression of either NaPi-IIc or PiT2, the other cotransporters known to participate in renal Pi reabsorption. In contrast, the intestinal expression of NaPi-IIb is downregulated in mutant animals, suggesting that a reduced intestinal absorption of Pi could contribute to maintain a normophosphatemic status despite the increased renal retention. The second goal of this work was to study whether the alterations on the expression of NaPi-IIa induced by chronic dietary Pi are impaired in the absence of GABARAP. Our data indicate that, in response to high Pi diets, GABARAP-deficient mice downregulate the expression of NaPi-IIa to levels comparable to those seen in wild-type animals. However, in response to low Pi diets, the upregulation of NaPi-IIa is greater in the mutant mice. Thus, both the basal expression and the dietary-induced upregulation of NaPi-IIa are increased in the absence of GABARAP.
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Affiliation(s)
- Sonja C Reining
- Institute of Physiology, University of Zurich, Winterthurerstr. 190, 8057, Zurich, Switzerland
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Regulation of postsynaptic gephyrin cluster size by protein phosphatase 1. Mol Cell Neurosci 2010; 44:201-9. [PMID: 20206270 DOI: 10.1016/j.mcn.2010.02.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2009] [Revised: 02/22/2010] [Accepted: 02/23/2010] [Indexed: 01/21/2023] Open
Abstract
The scaffolding protein gephyrin is essential for the clustering of glycine and GABA(A) receptors (GABA(A)Rs) at inhibitory synapses. Here, we provide evidence that the size of the postsynaptic gephyrin scaffold is controlled by dephosphorylation reactions. Treatment of cultured hippocampal neurons with the protein phosphatase inhibitors calyculin A and okadaic acid reduced the size of postsynaptic gephyrin clusters and increased cytoplasmic gephyrin staining. Protein phosphatase 1 (PP1) was found to colocalize with gephyrin at selected postsynaptic sites and to interact with gephyrin in transfected cells and brain extracts. Alanine or glutamate substitution of the two established serine/threonine phosphorylation sites in gephyrin failed to affect its clustering at inhibitory synapses and its ability to recruit gamma2 subunit containing GABA(A)Rs. Our data are consistent with the postsynaptic gephyrin scaffold acting as a platform for PP1, which regulates gephyrin cluster size by dephosphorylation of gephyrin- or cytoskeleton-associated proteins.
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Mansuy V, Risold PY, Glauser M, Fraichard A, Pralong FP. Expression of the GABAA receptor associated protein Gec1 is circadian and dependent upon the cellular clock machinery in GnRH secreting GnV-3 cells. Mol Cell Endocrinol 2009; 307:68-76. [PMID: 19524128 DOI: 10.1016/j.mce.2009.02.029] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/03/2008] [Revised: 02/25/2009] [Accepted: 02/25/2009] [Indexed: 11/23/2022]
Abstract
The timely regulation of gonadotropin-releasing hormone (GnRH) secretion requires a GABAergic signal. We hypothesized that GEC1, a protein promoting the transport of GABA(A) receptors, could represent a circadian effector in GnRH neurons. First, we demonstrated that gec1 is co-expressed with the GABA(A) receptor in hypothalamic rat GnRH neurons. We also confirmed that the clock genes per1, cry1 and bmal1 are expressed and oscillate in GnRH secreting GnV-3 cells. Then we could show that gec1 is expressed in GnV-3 cells, and oscillates in a manner temporally related to the oscillations of the clock transcription factors. Furthermore, we could demonstrate that these oscillations depend upon Per1 expression. Finally, we observed that GABA(A) receptor levels at the GnV-3 cell membrane are timely modulated following serum shock. Together, these data demonstrate that gec1 expression is dependent upon the circadian clock machinery in GnRH-expressing neurons, and suggest for the first time that the level of GABA(A) receptor at the cell membrane may be under timely regulation. Overall, they provide a potential mechanism for the circadian regulation of GnRH secretion by GABA, and may also be relevant to the general understanding of circadian rhythms.
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Affiliation(s)
- Virginie Mansuy
- Services of Endocrinology, Diabetology, and Metabolism of the University Hospital of Lausanne, Switzerland
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Mohrlüder J, Schwarten M, Willbold D. Structure and potential function of gamma-aminobutyrate type A receptor-associated protein. FEBS J 2009; 276:4989-5005. [PMID: 19674112 DOI: 10.1111/j.1742-4658.2009.07207.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The gamma-aminobutyrate type A receptor-associated protein (GABARAP) is a ubiquitin-like modifier, and is implicated in a variety of membrane trafficking and fusion events that are crucial to synaptic plasticity, autophagy and apoptosis. However, important aspects of GABARAP function and regulation remain poorly understood. We review the current state of knowledge about GABARAP, highlighting newly-identified GABARAP ligands, and discuss the possible physiological relevance of each ligand interaction.
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Affiliation(s)
- Jeannine Mohrlüder
- Institut für Strukturbiologie und Biophysik (ISB-3), Forschungszentrum Jülich, Germany.
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Reining SC, Gisler SM, Fuster D, Moe OW, O'Sullivan GA, Betz H, Biber J, Murer H, Hernando N. GABARAP deficiency modulates expression of NaPi-IIa in renal brush-border membranes. Am J Physiol Renal Physiol 2009; 296:F1118-28. [PMID: 19225049 PMCID: PMC2681362 DOI: 10.1152/ajprenal.90492.2008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2008] [Accepted: 02/13/2009] [Indexed: 01/04/2023] Open
Abstract
Renal reabsorption of inorganic phosphate (P(i)) is mainly mediated by the Na(+)-dependent P(i)-cotransporter NaPi-IIa that is expressed in the brush-border membrane (BBM) of renal proximal tubules. Regulation and apical expression of NaPi-IIa are known to depend on a network of interacting proteins. Most of the interacting partners identified so far associate with the COOH-terminal PDZ-binding motif (TRL) of NaPi-IIa. In this study GABA(A) receptor-associated protein (GABARAP) was identified as a novel interacting partner of NaPi-IIa applying a membrane yeast-two-hybrid system (MYTH 2.0) to screen a mouse kidney library with the TRL-truncated cotransporter as bait. GABARAP mRNA and protein are present in renal tubules, and the interaction of NaPi-IIa and GABARAP was confirmed by using glutathione S-transferase pulldowns from BBM and coimmunoprecipitations from transfected HEK293 cells. Amino acids 36-68 of GABARAP were identified as the determinant for the described interaction. The in vivo effects of this interaction were studied in a murine model. GABARAP(-/-) mice have reduced urinary excretion of P(i), higher Na(+)-dependent (32)P(i) uptake in BBM vesicles, and increased expression of NaPi-IIa in renal BBM compared with GABARAP(+/+) mice. The expression of Na(+)/H(+) exchanger regulatory factor (NHERF)1, an important scaffold for the apical expression of NaPi-IIa, is also increased in GABARAP(-/-) mice. The absence of GABARAP does not interfere with the regulation of the cotransporter by either parathyroid hormone or acute changes of dietary P(i) content.
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Affiliation(s)
- Sonja C Reining
- Institute of Physiology and Zurich Center for Integrative Human Physiology (ZIHP University of Zurich, Winterthurerstr. 190, 8057 Zurich, Switzerland
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Chen Y, Chen C, Kotsikorou E, Lynch DL, Reggio PH, Liu-Chen LY. GEC1-kappa opioid receptor binding involves hydrophobic interactions: GEC1 has chaperone-like effect. J Biol Chem 2008; 284:1673-85. [PMID: 19001416 DOI: 10.1074/jbc.m808303200] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We demonstrated previously that the protein GEC1 (glandular epithelial cell 1) bound to the human kappa opioid receptor (hKOPR) and promoted cell surface expression of the receptor by facilitating its trafficking along the secretory pathway. Here we showed that three hKOPR residues (Phe345, Pro346, and Met350) and seven GEC1 residues (Tyr49, Val51, Leu55, Thr56, Val57, Phe60, and Ile64) are indispensable for the interaction. Modeling studies revealed that the interaction was mediated via direct contacts between the kinked hydrophobic fragment in hKOPR C-tail and the curved hydrophobic surface in GEC1 around the S2 beta-strand. Intramolecular Leu44-Tyr109 interaction in GEC1 was important, likely by maintaining its structural integrity. Microtubule binding mediated by the GEC1 N-terminal domain was essential for the GEC1 effect. Expression of GEC1 also increased cell surface levels of the GluR1 subunit and the prostaglandin EP3.f receptor, which have FPXXM and FPXM sequences, respectively. With its widespread distribution in the nervous system and its predominantly hydrophobic interactions, GEC1 may have chaperone-like effects for many cell surface proteins along the biosynthesis pathway.
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Affiliation(s)
- Yong Chen
- Department of Pharmacology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA
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Bruneau EG, Esteban JA, Akaaboune M. Receptor-associated proteins and synaptic plasticity. FASEB J 2008; 23:679-88. [PMID: 18978155 DOI: 10.1096/fj.08-107946] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Changes in synaptic strength are important for synaptic development and synaptic plasticity. Most directly responsible for these synaptic changes are alterations in synaptic receptor number and density. Although alterations in receptor density mediated by the insertion, lateral mobility, removal, and recycling of receptors have been extensively studied, the dynamics and regulators of intracellular scaffolding proteins have only recently begun to be illuminated. In particular, a closer look at the receptor-associated proteins, which bind to receptors and are necessary for their synaptic localization and clustering, has revealed broader functions than previously thought and some rather unexpected thematic similarities. More than just "placeholders" or members of a passive protein "scaffold," receptor-associated proteins in every synapse studied have been shown to provide a number of signaling roles. In addition, the most recent state-of-the-art imaging has revealed that receptor-associated proteins are highly dynamic and are involved in regulating synaptic receptor density. Together, these results challenge the view that receptor-associated proteins are members of a static and stable scaffold and argue that their dynamic mobility may be essential for regulating activity-dependent changes in synaptic strength.
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Affiliation(s)
- Emile G Bruneau
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan 48109, USA
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46
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Ligand Binding Mode of GABAA Receptor-Associated Protein. J Mol Biol 2008; 381:1320-31. [DOI: 10.1016/j.jmb.2008.06.086] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2008] [Revised: 06/27/2008] [Accepted: 06/30/2008] [Indexed: 12/22/2022]
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Tretter V, Moss SJ. GABA(A) Receptor Dynamics and Constructing GABAergic Synapses. Front Mol Neurosci 2008; 1:7. [PMID: 18946540 PMCID: PMC2526003 DOI: 10.3389/neuro.02.007.2008] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2008] [Accepted: 05/16/2008] [Indexed: 12/04/2022] Open
Abstract
GABAA receptors are located on the majority of neurons in the central and peripheral nervous system, where they mediate important actions of the neurotransmitter gamma-aminobutyric acid. Early in development the trophic properties of GABA allow a healthy development of the nervous system. Most neurons have a high intracellular Cl-concentration early in life due to the late functional expression of the Cl-pump KCC2, therefore GABA has excitatory effects at this stage. Upon higher expression and activation of KCC2 GABA takes on its inhibitory effects while glutamate functions as the major excitatory neurotransmitter. Like all multisubunit membrane proteins the GABAA receptor is assembled in the ER and travels through the Golgi and remaining secretory pathway to the cell surface, where it mediates GABA actions either directly at the synapses or at extrasynaptic sites responding to ambient GABA to provide a basal tonic inhibitory state. In order to adapt to changing needs and information states, the GABAergic system is highly dynamic. That includes subtype specific trafficking to different locations in the cell, regulation of mobility by interaction with scaffold molecules, posttranslational modifications, that either directly affect channel function or the interaction with other proteins and finally the dynamic exchange between surface and intracellular receptor pools, that either prepare receptors for recycling to the surface or degradation. Here we give an overview of the current understanding of GABAA receptor functional and molecular dynamics that play a major part in maintaining the balance between excitation and inhibition and in changes in network activity.
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Affiliation(s)
- Verena Tretter
- Department of Neuroscience, University of Pennsylvania Philadelphia, PA, USA
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48
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Gephyrin: where do we stand, where do we go? Trends Neurosci 2008; 31:257-64. [DOI: 10.1016/j.tins.2008.02.006] [Citation(s) in RCA: 257] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2007] [Revised: 02/17/2008] [Accepted: 02/19/2008] [Indexed: 11/24/2022]
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Jacob TC, Moss SJ, Jurd R. GABA(A) receptor trafficking and its role in the dynamic modulation of neuronal inhibition. Nat Rev Neurosci 2008; 9:331-43. [PMID: 18382465 PMCID: PMC2709246 DOI: 10.1038/nrn2370] [Citation(s) in RCA: 465] [Impact Index Per Article: 29.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
GABA (gamma-aminobutyric acid) type A receptors (GABA(A)Rs) mediate most fast synaptic inhibition in the mammalian brain, controlling activity at both the network and the cellular levels. The diverse functions of GABA in the CNS are matched not just by the heterogeneity of GABA(A)Rs, but also by the complex trafficking mechanisms and protein-protein interactions that generate and maintain an appropriate receptor cell-surface localization. In this Review, we discuss recent progress in our understanding of the dynamic regulation of GABA(A)R composition, trafficking to and from the neuronal surface, and lateral movement of receptors between synaptic and extrasynaptic locations. Finally, we highlight a number of neurological disorders, including epilepsy and schizophrenia, in which alterations in GABA(A)R trafficking occur.
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Affiliation(s)
- Tija C. Jacob
- Department of Neuroscience, University of Pennsylvania, Philadelphia, Pennsylvania, 19104, USA
| | - Stephen J. Moss
- Department of Neuroscience, University of Pennsylvania, Philadelphia, Pennsylvania, 19104, USA
- Department of Pharmacology, University College London, WC1E 6BT, UK
| | - Rachel Jurd
- Department of Neuroscience, University of Pennsylvania, Philadelphia, Pennsylvania, 19104, USA
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Marsden KC, Beattie JB, Friedenthal J, Carroll RC. NMDA receptor activation potentiates inhibitory transmission through GABA receptor-associated protein-dependent exocytosis of GABA(A) receptors. J Neurosci 2007; 27:14326-37. [PMID: 18160640 PMCID: PMC6673443 DOI: 10.1523/jneurosci.4433-07.2007] [Citation(s) in RCA: 140] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2007] [Revised: 11/02/2007] [Accepted: 11/10/2007] [Indexed: 11/21/2022] Open
Abstract
The trafficking of postsynaptic AMPA receptors (AMPARs) is a powerful mechanism for regulating the strength of excitatory synapses. It has become clear that the surface levels of inhibitory GABA(A) receptors (GABA(A)Rs) are also subject to regulation and that GABA(A)R trafficking may contribute to inhibitory plasticity, although the underlying mechanisms are not fully understood. Here, we report that NMDA receptor activation, which has been shown to drive excitatory long-term depression through AMPAR endocytosis, simultaneously increases expression of GABA(A)Rs at the dendritic surface of hippocampal neurons. This NMDA stimulus increases miniature IPSC amplitudes and requires the activity of Ca2+ calmodulin-dependent kinase II and the trafficking proteins N-ethylmaleimide-sensitive factor, GABA receptor-associated protein (GABARAP), and glutamate receptor interacting protein (GRIP). These data demonstrate for the first time that endogenous GABARAP and GRIP contribute to the regulated trafficking of GABA(A)Rs. In addition, they reveal that the bidirectional trafficking of AMPA and GABA(A) receptors can be driven by a single glutamatergic stimulus, providing a potent postsynaptic mechanism for modulating neuronal excitability.
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Affiliation(s)
- Kurt C. Marsden
- Dominick P. Purpura Department of Neuroscience, Rose Kennedy Center for Mental Retardation, Albert Einstein College of Medicine of Yeshiva University, Bronx, New York 10461, and
| | - Jennifer B. Beattie
- Dominick P. Purpura Department of Neuroscience, Rose Kennedy Center for Mental Retardation, Albert Einstein College of Medicine of Yeshiva University, Bronx, New York 10461, and
| | - Jenna Friedenthal
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520
| | - Reed C. Carroll
- Dominick P. Purpura Department of Neuroscience, Rose Kennedy Center for Mental Retardation, Albert Einstein College of Medicine of Yeshiva University, Bronx, New York 10461, and
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