1
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Chen S, Wang Y, Cui T, Zheng Y, Zhang F, Ma Q, Zhang C, Liu X. Characterization of three non-canonical N-glycosylation motifs indicates N glyco-A reduces DNA N6-methyladenine and N glyco-D alters G/F actin ratio in Phytophthora sojae. Int J Biol Macromol 2024; 277:133943. [PMID: 39025174 DOI: 10.1016/j.ijbiomac.2024.133943] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2024] [Revised: 07/08/2024] [Accepted: 07/15/2024] [Indexed: 07/20/2024]
Abstract
Asparagine (Asn, N)-linked glycosylation is an abundant post-translational modification in which Asn, typically in Nglyco-X-S/T; X ≠ P motifs, are modified with N-glycans. It has essential regulatory roles in multicellular organisms. In this study, we systematically investigate the function of three N-glycosylation motifs (Nglyco-A, Nglyco-D and Nglyco-S) previously identified in Phytophthora sojae, through site-directed mutagenesis and functional assays. In P. sojae expressing glycosylation-dead variants pre-PsDMAP1N70A (Nglyco-A motif) or PsADFN64A (Nglyco-D motif), zoospore release or cyst germination is impaired. In particular, the pre-PsDMAP1N70A mutant reduces DNA methylation levels, and the PsADFN64A mutant disrupts the actin forms, which could explain the decrease in pathogenicity after N-glycosylation is destroyed. Similarly, P. sojae expressing PsNRXN132A (Nglyco-S motif) shows increased sensitivity to H2O2 and heat. Through autophagy or 26S proteasome pathway inhibition assays, we found that unglycosylated pre-PsDMAP1N70A and PsADFN64A are degraded via the 26S proteasome pathway, while the autophagy pathway is responsible for PsNRXN132A clearance. These findings demonstrate that glycosylation of these motifs regulates the stability and function of glycoproteins necessary for P. sojae growth, reproduction and pathogenicity, which expands the scope of known N-glycosylation regulatory functions in oomycetes.
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Affiliation(s)
- Shanshan Chen
- Department of Plant Pathology, China Agricultural University, Beijing 100193, China
| | - Yuke Wang
- Department of Plant Pathology, China Agricultural University, Beijing 100193, China
| | - Tongshan Cui
- Department of Plant Pathology, China Agricultural University, Beijing 100193, China
| | - Yuxin Zheng
- Department of Plant Pathology, China Agricultural University, Beijing 100193, China
| | - Fan Zhang
- Department of Plant Pathology, China Agricultural University, Beijing 100193, China
| | - Quanhe Ma
- Department of Plant Pathology, China Agricultural University, Beijing 100193, China
| | - Can Zhang
- Department of Plant Pathology, China Agricultural University, Beijing 100193, China.
| | - Xili Liu
- Department of Plant Pathology, China Agricultural University, Beijing 100193, China; State Key Laboratory of Crop Stress Biology for Arid Areas, Northwest A&F University, Yangling 712100, China.
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2
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Ferranti AS, Luessen DJ, Niswender CM. Novel pharmacological targets for GABAergic dysfunction in ADHD. Neuropharmacology 2024; 249:109897. [PMID: 38462041 DOI: 10.1016/j.neuropharm.2024.109897] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2024] [Revised: 02/26/2024] [Accepted: 03/04/2024] [Indexed: 03/12/2024]
Abstract
Attention deficit/hyperactivity disorder (ADHD) is a neurodevelopment disorder that affects approximately 5% of the population. The disorder is characterized by impulsivity, hyperactivity, and deficits in attention and cognition, although symptoms vary across patients due to the heterogenous and polygenic nature of the disorder. Stimulant medications are the standard of care treatment for ADHD patients, and their effectiveness has led to the dopaminergic hypothesis of ADHD in which deficits in dopaminergic signaling, especially in cortical brain regions, mechanistically underly ADHD pathophysiology. Despite their effectiveness in many individuals, almost one-third of patients do not respond to stimulant treatments and the long-term negative side effects of these medications remain unclear. Emerging clinical evidence is beginning to highlight an important role of dysregulated excitatory/inhibitory (E/I) balance in ADHD. These deficits in E/I balance are related to functional abnormalities in glutamate and Gamma-Aminobutyric Acid (GABA) signaling in the brain, with increasing emphasis placed on GABAergic interneurons driving specific aspects of ADHD pathophysiology. Recent genome-wide association studies (GWAS) have also highlighted how genes associated with GABA function are mutated in human populations with ADHD, resulting in the generation of several new genetic mouse models of ADHD. This review will discuss how GABAergic dysfunction underlies ADHD pathophysiology, and how specific receptors/proteins related to GABAergic interneuron dysfunction may be pharmacologically targeted to treat ADHD in subpopulations with specific comorbidities and symptom domains. This article is part of the Special Issue on "PFC circuit function in psychiatric disease and relevant models".
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Affiliation(s)
- Anthony S Ferranti
- Department of Pharmacology, Vanderbilt University, Nashville, TN, 37232, USA; Warren Center for Neuroscience Drug Discovery, Nashville, TN, 37232, USA
| | - Deborah J Luessen
- Department of Pharmacology, Vanderbilt University, Nashville, TN, 37232, USA; Warren Center for Neuroscience Drug Discovery, Nashville, TN, 37232, USA
| | - Colleen M Niswender
- Department of Pharmacology, Vanderbilt University, Nashville, TN, 37232, USA; Warren Center for Neuroscience Drug Discovery, Nashville, TN, 37232, USA; Vanderbilt Kennedy Center, Vanderbilt University Medical Center, Nashville, TN, 37232, USA; Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN, 37232, USA; Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, TN, 37232, USA.
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3
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Parent HH, Niswender CM. Therapeutic Potential for Metabotropic Glutamate Receptor 7 Modulators in Cognitive Disorders. Mol Pharmacol 2024; 105:348-358. [PMID: 38423750 PMCID: PMC11026152 DOI: 10.1124/molpharm.124.000874] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2024] [Revised: 02/05/2024] [Accepted: 02/12/2024] [Indexed: 03/02/2024] Open
Abstract
Metabotropic glutamate receptor 7 (mGlu7) is the most highly conserved and abundantly expressed mGlu receptor in the human brain. The presynaptic localization of mGlu7, coupled with its low affinity for its endogenous agonist, glutamate, are features that contribute to the receptor's role in modulating neuronal excitation and inhibition patterns, including long-term potentiation, in various brain regions. These characteristics suggest that mGlu7 modulation may serve as a novel therapeutic strategy in disorders of cognitive dysfunction, including neurodevelopmental disorders that cause impairments in learning, memory, and attention. Primary mutations in the GRM7 gene have recently been identified as novel causes of neurodevelopmental disorders, and these patients exhibit profound intellectual and cognitive disability. Pharmacological tools, such as agonists, antagonists, and allosteric modulators, have been the mainstay for targeting mGlu7 in its endogenous homodimeric form to probe effects of its function and modulation in disease models. However, recent research has identified diversity in dimerization, as well as trans-synaptic interacting proteins, that also play a role in mGlu7 signaling and pharmacological properties. These novel findings represent exciting opportunities in the field of mGlu receptor drug discovery and highlight the importance of further understanding the functions of mGlu7 in complex neurologic conditions at both the molecular and physiologic levels. SIGNIFICANCE STATEMENT: Proper expression and function of mGlu7 is essential for learning, attention, and memory formation at the molecular level within neural circuits. The pharmacological targeting of mGlu7 is undergoing a paradigm shift by incorporating an understanding of receptor interaction with other cis- and trans- acting synaptic proteins, as well as various intracellular signaling pathways. Based upon these new findings, mGlu7's potential as a drug target in the treatment of cognitive disorders and learning impairments is primed for exploration.
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Affiliation(s)
- Harrison H Parent
- Department of Pharmacology (H.H.P., C.M.N.), Warren Center for Neuroscience Drug Discovery (H.H.P., C.M.N.), Vanderbilt Brain Institute (C.M.N.), and Vanderbilt Institute for Chemical Biology (C.M.N.), Vanderbilt University, Nashville, Tennessee; and Vanderbilt Kennedy Center, Vanderbilt University Medical Center, Nashville, Tennessee (C.M.N.)
| | - Colleen M Niswender
- Department of Pharmacology (H.H.P., C.M.N.), Warren Center for Neuroscience Drug Discovery (H.H.P., C.M.N.), Vanderbilt Brain Institute (C.M.N.), and Vanderbilt Institute for Chemical Biology (C.M.N.), Vanderbilt University, Nashville, Tennessee; and Vanderbilt Kennedy Center, Vanderbilt University Medical Center, Nashville, Tennessee (C.M.N.)
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4
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Miller ML, Pindwarawala M, Agosto MA. Complex N-glycosylation of mGluR6 is required for trans-synaptic interaction with ELFN adhesion proteins. J Biol Chem 2024; 300:107119. [PMID: 38428819 PMCID: PMC10973816 DOI: 10.1016/j.jbc.2024.107119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Revised: 01/30/2024] [Accepted: 02/16/2024] [Indexed: 03/03/2024] Open
Abstract
Synaptic transmission from retinal photoreceptors to downstream ON-type bipolar cells (BCs) depends on the postsynaptic metabotropic glutamate receptor mGluR6, located at the BC dendritic tips. Glutamate binding to mGluR6 initiates G-protein signaling that ultimately leads to BC depolarization in response to light. The mGluR6 receptor also engages in trans-synaptic interactions with presynaptic ELFN adhesion proteins. The roles of post-translational modifications in mGluR6 trafficking and function are unknown. Treatment with glycosidase enzymes PNGase F and Endo H demonstrated that both endogenous and heterologously expressed mGluR6 contain complex N-glycosylation acquired in the Golgi. Pull-down experiments with ELFN1 and ELFN2 extracellular domains revealed that these proteins interact exclusively with the complex glycosylated form of mGluR6. Mutation of the four predicted N-glycosylation sites, either singly or in combination, revealed that all four sites are glycosylated. Single mutations partially reduced, but did not abolish, surface expression in heterologous cells, while triple mutants had little or no surface expression, indicating that no single glycosylation site is necessary or sufficient for plasma membrane trafficking. Mutation at N445 severely impaired both ELFN1 and ELFN2 binding. All single mutants exhibited dendritic tip enrichment in rod BCs, as did the triple mutant with N445 as the sole N-glycosylation site, demonstrating that glycosylation at N445 is sufficient but not necessary for dendritic tip localization. The quadruple mutant was completely mislocalized. These results reveal a key role for complex N-glycosylation in regulating mGluR6 trafficking and ELFN binding, and by extension, function of the photoreceptor synapses.
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Affiliation(s)
- Michael L Miller
- Faculty of Science, Medical Sciences Program, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Mustansir Pindwarawala
- Faculty of Science, Medical Sciences Program, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Melina A Agosto
- Retina and Optic Nerve Research Laboratory, Dalhousie University, Halifax, Nova Scotia, Canada; Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia, Canada; Department of Ophthalmology and Visual Sciences, Dalhousie University, Halifax, Nova Scotia, Canada.
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5
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Shimohata A, Rai D, Akagi T, Usui S, Ogiwara I, Kaneda M. The intracellular C-terminal domain of mGluR6 contains ER retention motifs. Mol Cell Neurosci 2023; 126:103875. [PMID: 37352898 DOI: 10.1016/j.mcn.2023.103875] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Revised: 06/15/2023] [Accepted: 06/19/2023] [Indexed: 06/25/2023] Open
Abstract
Metabotropic glutamate receptor 6 (mGluR6) predominantly localizes to the postsynaptic sites of retinal ON-bipolar cells, at which it recognizes glutamate released from photoreceptors. The C-terminal domain (CTD) of mGluR6 contains a cluster of basic amino acids resembling motifs for endoplasmic reticulum (ER) retention. We herein investigated whether these basic residues are involved in regulating the subcellular localization of mGluR6 in 293T cells expressing mGluR6 CTD mutants using immunocytochemistry, immunoprecipitation, and flow cytometry. We showed that full-length mGluR6 localized to the ER and cell surface, whereas mGluR6 mutants with 15- and 20-amino acid deletions from the C terminus localized to the ER, but were deficient at the cell surface. We also demonstrated that the cell surface deficiency of mGluR6 mutants was rescued by introducing an alanine substitution at basic residues within the CTD. The surface-deficient mGluR6 mutant still did not localize to the cell surface and was retained in the ER when co-expressed with surface-expressible constructs, including full-length mGluR6, even though surface-deficient and surface-expressible constructs formed heteromeric complexes. The co-expression of the surface-deficient mGluR6 mutant reduced the surface levels of surface-expressible constructs. These results indicate that basic residues in the mGluR6 CTD served as ER retention signals. We suggest that exposed ER retention motifs in the aberrant assembly containing truncated or misfolded mGluR6 prevent these protein complexes from being transported to the cell surface.
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Affiliation(s)
- Atsushi Shimohata
- Department of Physiology, Nippon Medical School, Tokyo 113-8602, Japan
| | - Dilip Rai
- Department of Physiology, Nippon Medical School, Tokyo 113-8602, Japan
| | - Takumi Akagi
- Department of Physiology, Nippon Medical School, Tokyo 113-8602, Japan
| | - Sumiko Usui
- Department of Physiology, Nippon Medical School, Tokyo 113-8602, Japan
| | - Ikuo Ogiwara
- Department of Physiology, Nippon Medical School, Tokyo 113-8602, Japan.
| | - Makoto Kaneda
- Department of Physiology, Nippon Medical School, Tokyo 113-8602, Japan
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6
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Zhang B, Li S, Shui W. Post-Translational Modifications of G Protein–Coupled Receptors Revealed by Proteomics and Structural Biology. Front Chem 2022; 10:843502. [PMID: 35355784 PMCID: PMC8960047 DOI: 10.3389/fchem.2022.843502] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2021] [Accepted: 02/16/2022] [Indexed: 01/20/2023] Open
Abstract
G protein–coupled receptors (GPCRs) are a protein superfamily comprising >800 members that regulate numerous cellular and physiologic responses. GPCRs represent the largest class of therapeutic targets with implications in various diseases. Although advances in GPCR structural and pharmacological research have significantly improved our knowledge of GPCR signaling mechanisms, mapping diverse post-translational modifications (PTMs) of GPCR proteins and understanding their regulatory roles have received much less attention. Mass spectrometry-based proteomics has become the most popular technology for profiling protein PTMs in a systematic manner. Herein we provide an overview of PTM types, locations, crosstalk and dynamic regulation for different GPCRs that are characterized using proteomic and/or biochemical approaches. Our main focus is on glycosylation, phosphorylation, ubiquitination and palmitoylation that are known to modulate receptor folding, biosynthesis, trafficking, dimerization and signaling. Furthermore, we discuss the locations of specific PTM sites in the structure of a given GPCR and its signaling complex to highlight the importance of PTM regulation in the molecular basis of GPCRs, which may shed new light on structure-based drug discovery.
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Affiliation(s)
- Bingjie Zhang
- iHuman Institute, ShanghaiTech University, Shanghai, China
| | - Shanshan Li
- iHuman Institute, ShanghaiTech University, Shanghai, China
| | - Wenqing Shui
- iHuman Institute, ShanghaiTech University, Shanghai, China
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
- *Correspondence: Wenqing Shui,
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7
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Membrane trafficking and positioning of mGluRs at presynaptic and postsynaptic sites of excitatory synapses. Neuropharmacology 2021; 200:108799. [PMID: 34592242 DOI: 10.1016/j.neuropharm.2021.108799] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Revised: 08/31/2021] [Accepted: 09/17/2021] [Indexed: 01/21/2023]
Abstract
The plethora of functions of glutamate in the brain are mediated by the complementary actions of ionotropic and metabotropic glutamate receptors (mGluRs). The ionotropic glutamate receptors carry most of the fast excitatory transmission, while mGluRs modulate transmission on longer timescales by triggering multiple intracellular signaling pathways. As such, mGluRs mediate critical aspects of synaptic transmission and plasticity. Interestingly, at synapses, mGluRs operate at both sides of the cleft, and thus bidirectionally exert the effects of glutamate. At postsynaptic sites, group I mGluRs act to modulate excitability and plasticity. At presynaptic sites, group II and III mGluRs act as auto-receptors, modulating release properties in an activity-dependent manner. Thus, synaptic mGluRs are essential signal integrators that functionally couple presynaptic and postsynaptic mechanisms of transmission and plasticity. Understanding how these receptors reach the membrane and are positioned relative to the presynaptic glutamate release site are therefore important aspects of synapse biology. In this review, we will discuss the currently known mechanisms underlying the trafficking and positioning of mGluRs at and around synapses, and how these mechanisms contribute to synaptic functioning. We will highlight outstanding questions and present an outlook on how recent technological developments will move this exciting research field forward.
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8
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Conroy LR, Hawkinson TR, Young LEA, Gentry MS, Sun RC. Emerging roles of N-linked glycosylation in brain physiology and disorders. Trends Endocrinol Metab 2021; 32:980-993. [PMID: 34756776 PMCID: PMC8589112 DOI: 10.1016/j.tem.2021.09.006] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Revised: 09/10/2021] [Accepted: 09/23/2021] [Indexed: 11/15/2022]
Abstract
N-linked glycosylation is a complex, co- and post-translational series of events that connects metabolism to signaling in almost all cells. Metabolic assembly of N-linked glycans spans multiple cellular compartments, and early N-linked glycan biosynthesis is a central mediator of protein folding and the unfolded protein response (UPR). In the brain, N-linked glycosylated proteins participate in a myriad of processes, from electrical gradients to neurotransmission. However, it is less clear how perturbations in N-linked glycosylation impact and even potentially drive aspects of neurological disorders. In this review, we discuss our current understanding of the metabolic origins of N-linked glycans in the brain, their role in modulating neuronal function, and how aberrant N-linked glycosylation can drive neurological disorders.
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Affiliation(s)
- Lindsey R Conroy
- Department of Neuroscience, University of Kentucky College of Medicine, Lexington, KY 40508-0536, USA; Markey Cancer Center, Lexington, KY 40508-0536, USA
| | - Tara R Hawkinson
- Department of Neuroscience, University of Kentucky College of Medicine, Lexington, KY 40508-0536, USA
| | - Lyndsay E A Young
- Department of Molecular and Cellular Biochemistry University of Kentucky College of Medicine, Lexington, KY 40508-0536, USA
| | - Matthew S Gentry
- Department of Molecular and Cellular Biochemistry University of Kentucky College of Medicine, Lexington, KY 40508-0536, USA
| | - Ramon C Sun
- Department of Neuroscience, University of Kentucky College of Medicine, Lexington, KY 40508-0536, USA; Markey Cancer Center, Lexington, KY 40508-0536, USA; Sanders Brown Center for Aging, Lexington, KY 40508-0536, USA.
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9
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Li Y, Li S, Liu J, Huo Y, Luo XJ. The schizophrenia susceptibility gene NAGA regulates dendritic spine density: further evidence for the dendritic spine pathology of schizophrenia. Mol Psychiatry 2021; 26:7102-7104. [PMID: 34376824 DOI: 10.1038/s41380-021-01261-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Revised: 07/28/2021] [Accepted: 07/30/2021] [Indexed: 11/09/2022]
Affiliation(s)
- Yifan Li
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences & Yunnan Province, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan, China.,Kunming College of Life Science, University of Chinese Academy of Sciences, Kunming, Yunnan, China
| | - Shiwu Li
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences & Yunnan Province, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan, China
| | - Jiewei Liu
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences & Yunnan Province, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan, China
| | - Yongxia Huo
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences & Yunnan Province, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan, China
| | - Xiong-Jian Luo
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences & Yunnan Province, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan, China. .,Kunming College of Life Science, University of Chinese Academy of Sciences, Kunming, Yunnan, China. .,Center for Excellence in Animal Evolution and Genetics, Chinese Academy of Sciences, Kunming, Yunnan, China. .,KIZ-CUHK Joint Laboratory of Bioresources and Molecular Research in Common Diseases, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan, China.
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10
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Jullié D, Valbret Z, Stoeber M. Optical tools to study the subcellular organization of GPCR neuromodulation. J Neurosci Methods 2021; 366:109408. [PMID: 34763022 DOI: 10.1016/j.jneumeth.2021.109408] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Revised: 10/11/2021] [Accepted: 11/03/2021] [Indexed: 12/29/2022]
Abstract
Modulation of neuronal circuit activity is key to information processing in the brain. G protein-coupled receptors (GPCRs), the targets of most neuromodulatory ligands, show extremely diverse expression patterns in neurons and receptors can be localized in various sub-neuronal membrane compartments. Upon activation, GPCRs promote signaling cascades that alter the level of second messengers, drive phosphorylation changes, modulate ion channel function, and influence gene expression, all of which critically impact neuron physiology. Because of its high degree of complexity, this form of interneuronal communication has remained challenging to integrate into our conceptual understanding of brain function. Recent technological advances in fluorescence microscopy and the development of optical biosensors now allow investigating neuromodulation with unprecedented resolution on the level of individual cells. In this review, we will highlight recent imaging techniques that enable determining the precise localization of GPCRs in neurons, with specific focus on the subcellular and nanoscale level. Downstream of receptors, we describe novel conformation-specific biosensors that allow for real-time monitoring of GPCR activation and of distinct signal transduction events in neurons. Applying these new tools has the potential to provide critical insights into the function and organization of GPCRs in neuronal cells and may help decipher the molecular and cellular mechanisms that underlie neuromodulation.
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Affiliation(s)
- Damien Jullié
- Department of Psychiatry, University of California San Francisco, San Francisco, USA.
| | - Zoé Valbret
- Department of Cell Physiology and Metabolism, University of Geneva, Geneva, Switzerland
| | - Miriam Stoeber
- Department of Cell Physiology and Metabolism, University of Geneva, Geneva, Switzerland.
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11
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Kang M, Lee D, Song JM, Park S, Park DH, Lee S, Suh YH. Neddylation is required for presynaptic clustering of mGlu7 and maturation of presynaptic terminals. Exp Mol Med 2021; 53:457-467. [PMID: 33767338 PMCID: PMC8080653 DOI: 10.1038/s12276-021-00585-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 01/31/2021] [Accepted: 02/09/2021] [Indexed: 12/17/2022] Open
Abstract
Neddylation is a posttranslational modification in which NEDD8 is conjugated to a target substrate by cellular processes similar to those involved in ubiquitination. Recent studies have identified PSD-95 and cofilin as substrates for neddylation in the brain and have shown that neddylation modulates the maturation and stability of dendritic spines in developing neurons. However, the precise substrates and functional consequences of neddylation at presynaptic terminals remain elusive. Here, we provide evidence that the mGlu7 receptor is a target of neddylation in heterologous cells and rat primary cultured neurons. We found that mGlu7 neddylation is reduced by agonist treatment and is required for the clustering of mGlu7 in the presynaptic active zone. In addition, we observed that neddylation is not required for the endocytosis of mGlu7, but it facilitates the ubiquitination of mGlu7 and stabilizes mGlu7 protein expression. Finally, we demonstrate that neddylation is necessary for the maturation of excitatory presynaptic terminals, providing a key role for neddylation in synaptic function.
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Affiliation(s)
- Minji Kang
- Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, 03080, Republic of Korea.,Neuroscience Research Institute, Seoul National University College of Medicine, Seoul, 03080, Republic of Korea.,Transplantation Research Institute, Seoul National University College of Medicine, Seoul, 03080, Republic of Korea
| | - DoEun Lee
- Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, 03080, Republic of Korea.,Neuroscience Research Institute, Seoul National University College of Medicine, Seoul, 03080, Republic of Korea.,Transplantation Research Institute, Seoul National University College of Medicine, Seoul, 03080, Republic of Korea
| | - Jae-Man Song
- Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, 03080, Republic of Korea.,Neuroscience Research Institute, Seoul National University College of Medicine, Seoul, 03080, Republic of Korea.,Transplantation Research Institute, Seoul National University College of Medicine, Seoul, 03080, Republic of Korea
| | - Sunha Park
- Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, 03080, Republic of Korea.,Neuroscience Research Institute, Seoul National University College of Medicine, Seoul, 03080, Republic of Korea.,Transplantation Research Institute, Seoul National University College of Medicine, Seoul, 03080, Republic of Korea
| | - Da-Ha Park
- Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, 03080, Republic of Korea.,Neuroscience Research Institute, Seoul National University College of Medicine, Seoul, 03080, Republic of Korea.,Transplantation Research Institute, Seoul National University College of Medicine, Seoul, 03080, Republic of Korea
| | - Sanghyeon Lee
- Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, 03080, Republic of Korea.,Neuroscience Research Institute, Seoul National University College of Medicine, Seoul, 03080, Republic of Korea.,Transplantation Research Institute, Seoul National University College of Medicine, Seoul, 03080, Republic of Korea
| | - Young Ho Suh
- Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, 03080, Republic of Korea. .,Neuroscience Research Institute, Seoul National University College of Medicine, Seoul, 03080, Republic of Korea. .,Transplantation Research Institute, Seoul National University College of Medicine, Seoul, 03080, Republic of Korea.
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12
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Fisher NM, AlHashim A, Buch AB, Badivuku H, Samman MM, Weiss KM, Cestero GI, Does MD, Rook JM, Lindsley CW, Conn PJ, Gogliotti RG, Niswender CM. A GRM7 mutation associated with developmental delay reduces mGlu7 expression and produces neurological phenotypes. JCI Insight 2021; 6:143324. [PMID: 33476302 PMCID: PMC7934925 DOI: 10.1172/jci.insight.143324] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Accepted: 01/13/2021] [Indexed: 12/29/2022] Open
Abstract
The metabotropic glutamate receptor 7 (mGlu7) is a G protein–coupled receptor that has been recently linked to neurodevelopmental disorders. This association is supported by the identification of GRM7 variants in patients with autism spectrum disorder, attention deficit hyperactivity disorder, and severe developmental delay. One GRM7 mutation previously reported in 2 patients results in a single amino acid change, I154T, within the mGlu7 ligand-binding domain. Here, we report 2 new patients with this mutation who present with severe developmental delay and epilepsy. Functional studies of the mGlu7-I154T mutant reveal that this substitution resulted in significant loss of mGlu7 protein expression in HEK293A cells and in mice. We show that this occurred posttranscriptionally at the level of protein expression and trafficking. Similar to mGlu7–global KO mice, mGlu7-I154T animals exhibited reduced motor coordination, deficits in contextual fear learning, and seizures. This provides functional evidence that a disease-associated mutation affecting the mGlu7 receptor was sufficient to cause neurological dysfunction in mice and further validates GRM7 as a disease-causing gene in the human population.
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Affiliation(s)
- Nicole M Fisher
- Department of Pharmacology and.,Warren Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, Tennessee, USA
| | | | - Aditi B Buch
- Department of Pharmacology and.,Warren Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, Tennessee, USA
| | - Hana Badivuku
- Department of Pharmacology and.,Warren Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, Tennessee, USA
| | | | - Kelly M Weiss
- Department of Pharmacology and.,Warren Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, Tennessee, USA
| | - Gabriela I Cestero
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
| | - Mark D Does
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
| | - Jerri M Rook
- Department of Pharmacology and.,Warren Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, Tennessee, USA
| | - Craig W Lindsley
- Department of Pharmacology and.,Warren Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, Tennessee, USA.,Department of Chemistry and.,Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee, USA
| | - P Jeffrey Conn
- Department of Pharmacology and.,Warren Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, Tennessee, USA.,Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee, USA.,Vanderbilt Kennedy Center, Vanderbilt University Medical Center, Nashville, Tennessee USA
| | - Rocco G Gogliotti
- Department of Pharmacology and.,Warren Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, Tennessee, USA.,Department of Molecular Pharmacology and Neuroscience, Loyola University Chicago, Maywood, Illinois, USA
| | - Colleen M Niswender
- Department of Pharmacology and.,Warren Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, Tennessee, USA.,Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee, USA.,Vanderbilt Kennedy Center, Vanderbilt University Medical Center, Nashville, Tennessee USA
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Pathogenic GRM7 Mutations Associated with Neurodevelopmental Disorders Impair Axon Outgrowth and Presynaptic Terminal Development. J Neurosci 2021; 41:2344-2359. [PMID: 33500274 DOI: 10.1523/jneurosci.2108-20.2021] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 01/11/2021] [Accepted: 01/16/2021] [Indexed: 12/18/2022] Open
Abstract
Metabotropic glutamate receptor 7 (mGlu7) is an inhibitory heterotrimeric G-protein-coupled receptor that modulates neurotransmitter release and synaptic plasticity at presynaptic terminals in the mammalian central nervous system. Recent studies have shown that rare mutations in glutamate receptors and synaptic scaffold proteins are associated with neurodevelopmental disorders (NDDs). However, the role of presynaptic mGlu7 in the pathogenesis of NDDs remains largely unknown. Recent whole-exome sequencing (WES) studies in families with NDDs have revealed that several missense mutations (c.1865G>A:p.R622Q; c.461T>C:p.I154T; c.1972C>T:p.R658W and c.2024C>A:p.T675K) or a nonsense mutation (c.1757G>A:p.W586X) in the GRM7 gene may be linked to NDDs. In the present study, we investigated the mechanistic links between GRM7 point mutations and NDD pathology. We find that the pathogenic GRM7 I154T and R658W/T675K mutations lead to the degradation of the mGlu7 protein. In particular, the GRM7 R658W/T675K mutation results in a lack of surface mGlu7 expression in heterologous cells and cultured neurons isolated from male and female rat embryos. We demonstrate that the expression of mGlu7 variants or exposure to mGlu7 antagonists impairs axon outgrowth through the mitogen-activated protein kinase (MAPK)-cAMP-protein kinase A (PKA) signaling pathway during early neuronal development, which subsequently leads to a decrease in the number of presynaptic terminals in mature neurons. Treatment with an mGlu7 agonist restores the pathologic phenotypes caused by mGlu7 I154T but not by mGlu7 R658W/T675K because of its lack of neuronal surface expression. These findings provide evidence that stable neuronal surface expression of mGlu7 is essential for neural development and that mGlu7 is a promising therapeutic target for NDDs.SIGNIFICANCE STATEMENT Neurodevelopmental disorders (NDDs) affect brain development and function by multiple etiologies. Metabotropic glutamate receptor 7 (mGlu7) is a receptor that controls excitatory neurotransmission and synaptic plasticity. Since accumulating evidence indicates that the GRM7 gene locus is associated with NDD risk, we analyzed the functional effects of human GRM7 variants identified in patients with NDDs. We demonstrate that stable neuronal surface expression of mGlu7 is essential for axon outgrowth and presynaptic terminal development in neurons. We found that mitogen-activated protein kinase (MAPK)-cAMP-protein kinase A (PKA) signaling and subsequent cytoskeletal dynamics are defective because of the degradation of mGlu7 variants. Finally, we show that the defects caused by mGlu7 I154T can be reversed by agonists, providing the rationale for proposing mGlu7 as a potential therapeutic target for NDDs.
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