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Carricaburu E, Benner O, Burlingham SR, Dos Santos Passos C, Hobaugh N, Karr CH, Chanda S. Gephyrin promotes autonomous assembly and synaptic localization of GABAergic postsynaptic components without presynaptic GABA release. Proc Natl Acad Sci U S A 2024; 121:e2315100121. [PMID: 38889143 PMCID: PMC11214061 DOI: 10.1073/pnas.2315100121] [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: 08/30/2023] [Accepted: 05/17/2024] [Indexed: 06/20/2024] Open
Abstract
Synapses containing γ-aminobutyric acid (GABA) constitute the primary centers for inhibitory neurotransmission in our nervous system. It is unclear how these synaptic structures form and align their postsynaptic machineries with presynaptic terminals. Here, we monitored the cellular distribution of several GABAergic postsynaptic proteins in a purely glutamatergic neuronal culture derived from human stem cells, which virtually lacks any vesicular GABA release. We found that several GABAA receptor (GABAAR) subunits, postsynaptic scaffolds, and major cell-adhesion molecules can reliably coaggregate and colocalize at even GABA-deficient subsynaptic domains, but remain physically segregated from glutamatergic counterparts. Genetic deletions of both Gephyrin and a Gephyrin-associated guanosine di- or triphosphate (GDP/GTP) exchange factor Collybistin severely disrupted the coassembly of these postsynaptic compositions and their proper apposition with presynaptic inputs. Gephyrin-GABAAR clusters, developed in the absence of GABA transmission, could be subsequently activated and even potentiated by delayed supply of vesicular GABA. Thus, molecular organization of GABAergic postsynapses can initiate via a GABA-independent but Gephyrin-dependent intrinsic mechanism.
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Affiliation(s)
- Etta Carricaburu
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO80523
| | - Orion Benner
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO80523
| | - Scott R. Burlingham
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO80523
| | | | - Natalia Hobaugh
- Biological Sciences Division, University of Chicago, Chicago, IL60637
| | - Charles H. Karr
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO80523
| | - Soham Chanda
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO80523
- Molecular, Cellular and Integrated Neurosciences Program, Colorado State University, Fort Collins, CO80523
- Cell and Molecular Biology Program, Colorado State University, Fort Collins, CO80523
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2
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Verma H, Kaur S, Kaur S, Gangwar P, Dhiman M, Mantha AK. Role of Cytoskeletal Elements in Regulation of Synaptic Functions: Implications Toward Alzheimer's Disease and Phytochemicals-Based Interventions. Mol Neurobiol 2024:10.1007/s12035-024-04053-3. [PMID: 38491338 DOI: 10.1007/s12035-024-04053-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Accepted: 02/13/2024] [Indexed: 03/18/2024]
Abstract
Alzheimer's disease (AD), a multifactorial disease, is characterized by the accumulation of neurofibrillary tangles (NFTs) and amyloid beta (Aβ) plaques. AD is triggered via several factors like alteration in cytoskeletal proteins, a mutation in presenilin 1 (PSEN1), presenilin 2 (PSEN2), amyloid precursor protein (APP), and post-translational modifications (PTMs) in the cytoskeletal elements. Owing to the major structural and functional role of cytoskeletal elements, like the organization of axon initial segmentation, dendritic spines, synaptic regulation, and delivery of cargo at the synapse; modulation of these elements plays an important role in AD pathogenesis; like Tau is a microtubule-associated protein that stabilizes the microtubules, and it also causes inhibition of nucleo-cytoplasmic transportation by disrupting the integrity of nuclear pore complex. One of the major cytoskeletal elements, actin and its dynamics, regulate the dendritic spine structure and functions; impairments have been documented towards learning and memory defects. The second major constituent of these cytoskeletal elements, microtubules, are necessary for the delivery of the cargo, like ion channels and receptors at the synaptic membranes, whereas actin-binding protein, i.e., Cofilin's activation form rod-like structures, is involved in the formation of paired helical filaments (PHFs) observed in AD. Also, the glial cells rely on their cytoskeleton to maintain synaptic functionality. Thus, making cytoskeletal elements and their regulation in synaptic structure and function as an important aspect to be focused for better management and targeting AD pathology. This review advocates exploring phytochemicals and Ayurvedic plant extracts against AD by elucidating their neuroprotective mechanisms involving cytoskeletal modulation and enhancing synaptic plasticity. However, challenges include their limited bioavailability due to the poor solubility and the limited potential to cross the blood-brain barrier (BBB), emphasizing the need for targeted strategies to improve therapeutic efficacy.
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Affiliation(s)
- Harkomal Verma
- Department of Zoology, School of Basic Sciences, Central University of Punjab, Village Ghudda, VPO - Ghudda, Bathinda, 151 401, Punjab, India
| | - Sharanjot Kaur
- Department of Microbiology, School of Basic Sciences, Central University of Punjab, Village Ghudda, Bathinda, Punjab, India
| | - Sukhchain Kaur
- Department of Microbiology, School of Basic Sciences, Central University of Punjab, Village Ghudda, Bathinda, Punjab, India
| | - Prabhakar Gangwar
- Department of Zoology, School of Basic Sciences, Central University of Punjab, Village Ghudda, VPO - Ghudda, Bathinda, 151 401, Punjab, India
| | - Monisha Dhiman
- Department of Microbiology, School of Basic Sciences, Central University of Punjab, Village Ghudda, Bathinda, Punjab, India
| | - Anil Kumar Mantha
- Department of Zoology, School of Basic Sciences, Central University of Punjab, Village Ghudda, VPO - Ghudda, Bathinda, 151 401, Punjab, India.
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Triantopoulou N, Vidaki M. Local mRNA translation and cytoskeletal reorganization: Mechanisms that tune neuronal responses. Front Mol Neurosci 2022; 15:949096. [PMID: 35979146 PMCID: PMC9376447 DOI: 10.3389/fnmol.2022.949096] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Accepted: 07/07/2022] [Indexed: 12/31/2022] Open
Abstract
Neurons are highly polarized cells with significantly long axonal and dendritic extensions that can reach distances up to hundreds of centimeters away from the cell bodies in higher vertebrates. Their successful formation, maintenance, and proper function highly depend on the coordination of intricate molecular networks that allow axons and dendrites to quickly process information, and respond to a continuous and diverse cascade of environmental stimuli, often without enough time for communication with the soma. Two seemingly unrelated processes, essential for these rapid responses, and thus neuronal homeostasis and plasticity, are local mRNA translation and cytoskeletal reorganization. The axonal cytoskeleton is characterized by high stability and great plasticity; two contradictory attributes that emerge from the powerful cytoskeletal rearrangement dynamics. Cytoskeletal reorganization is crucial during nervous system development and in adulthood, ensuring the establishment of proper neuronal shape and polarity, as well as regulating intracellular transport and synaptic functions. Local mRNA translation is another mechanism with a well-established role in the developing and adult nervous system. It is pivotal for axonal guidance and arborization, synaptic formation, and function and seems to be a key player in processes activated after neuronal damage. Perturbations in the regulatory pathways of local translation and cytoskeletal reorganization contribute to various pathologies with diverse clinical manifestations, ranging from intellectual disabilities (ID) to autism spectrum disorders (ASD) and schizophrenia (SCZ). Despite the fact that both processes are essential for the orchestration of pathways critical for proper axonal and dendritic function, the interplay between them remains elusive. Here we review our current knowledge on the molecular mechanisms and specific interaction networks that regulate and potentially coordinate these interconnected processes.
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Affiliation(s)
- Nikoletta Triantopoulou
- Division of Basic Sciences, Medical School, University of Crete, Heraklion, Greece
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology Hellas (IMBB-FORTH), Heraklion, Greece
| | - Marina Vidaki
- Division of Basic Sciences, Medical School, University of Crete, Heraklion, Greece
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology Hellas (IMBB-FORTH), Heraklion, Greece
- *Correspondence: Marina Vidaki,
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4
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Complex regulation of Gephyrin splicing is a determinant of inhibitory postsynaptic diversity. Nat Commun 2022; 13:3507. [PMID: 35717442 PMCID: PMC9206673 DOI: 10.1038/s41467-022-31264-w] [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: 11/30/2021] [Accepted: 06/10/2022] [Indexed: 01/05/2023] Open
Abstract
Gephyrin (GPHN) regulates the clustering of postsynaptic components at inhibitory synapses and is involved in pathophysiology of neuropsychiatric disorders. Here, we uncover an extensive diversity of GPHN transcripts that are tightly controlled by splicing during mouse and human brain development. Proteomic analysis reveals at least a hundred isoforms of GPHN incorporated at inhibitory Glycine and gamma-aminobutyric acid A receptors containing synapses. They exhibit different localization and postsynaptic clustering properties, and altering the expression level of one isoform is sufficient to affect the number, size, and density of inhibitory synapses in cerebellar Purkinje cells. Furthermore, we discovered that splicing defects reported in neuropsychiatric disorders are carried by multiple alternative GPHN transcripts, demonstrating the need for a thorough analysis of the GPHN transcriptome in patients. Overall, we show that alternative splicing of GPHN is an important genetic variation to consider in neurological diseases and a determinant of the diversity of postsynaptic inhibitory synapses. The protein gephyrin is involved in organizing synapses. Here, the authors show how different transcripts of gephyrin form and regulate inhibitory synapses.
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Deng C, Reinhard S, Hennlein L, Eilts J, Sachs S, Doose S, Jablonka S, Sauer M, Moradi M, Sendtner M. Impaired dynamic interaction of axonal endoplasmic reticulum and ribosomes contributes to defective stimulus-response in spinal muscular atrophy. Transl Neurodegener 2022; 11:31. [PMID: 35650592 PMCID: PMC9161492 DOI: 10.1186/s40035-022-00304-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Accepted: 04/28/2022] [Indexed: 11/19/2022] Open
Abstract
Background Axonal degeneration and defects in neuromuscular neurotransmission represent a pathological hallmark in spinal muscular atrophy (SMA) and other forms of motoneuron disease. These pathological changes do not only base on altered axonal and presynaptic architecture, but also on alterations in dynamic movements of organelles and subcellular structures that are not necessarily reflected by static histopathological changes. The dynamic interplay between the axonal endoplasmic reticulum (ER) and ribosomes is essential for stimulus-induced local translation in motor axons and presynaptic terminals. However, it remains enigmatic whether the ER and ribosome crosstalk is impaired in the presynaptic compartment of motoneurons with Smn (survival of motor neuron) deficiency that could contribute to axonopathy and presynaptic dysfunction in SMA. Methods Using super-resolution microscopy, proximity ligation assay (PLA) and live imaging of cultured motoneurons from a mouse model of SMA, we investigated the dynamics of the axonal ER and ribosome distribution and activation. Results We observed that the dynamic remodeling of ER was impaired in axon terminals of Smn-deficient motoneurons. In addition, in axon terminals of Smn-deficient motoneurons, ribosomes failed to respond to the brain-derived neurotrophic factor stimulation, and did not undergo rapid association with the axonal ER in response to extracellular stimuli. Conclusions These findings implicate impaired dynamic interplay between the ribosomes and ER in axon terminals of motoneurons as a contributor to the pathophysiology of SMA and possibly also other motoneuron diseases. Supplementary Information The online version contains supplementary material available at 10.1186/s40035-022-00304-2.
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Affiliation(s)
- Chunchu Deng
- Institute of Clinical Neurobiology, University Hospital Wuerzburg, 97078, Würzburg, Germany
| | - Sebastian Reinhard
- Department of Biotechnology and Biophysics, Biocenter, Julius-Maximilians-University Wuerzburg, 97074, Würzburg, Germany
| | - Luisa Hennlein
- Institute of Clinical Neurobiology, University Hospital Wuerzburg, 97078, Würzburg, Germany
| | - Janna Eilts
- Department of Biotechnology and Biophysics, Biocenter, Julius-Maximilians-University Wuerzburg, 97074, Würzburg, Germany
| | - Stefan Sachs
- Department of Biotechnology and Biophysics, Biocenter, Julius-Maximilians-University Wuerzburg, 97074, Würzburg, Germany
| | - Sören Doose
- Department of Biotechnology and Biophysics, Biocenter, Julius-Maximilians-University Wuerzburg, 97074, Würzburg, Germany
| | - Sibylle Jablonka
- Institute of Clinical Neurobiology, University Hospital Wuerzburg, 97078, Würzburg, Germany
| | - Markus Sauer
- Department of Biotechnology and Biophysics, Biocenter, Julius-Maximilians-University Wuerzburg, 97074, Würzburg, Germany
| | - Mehri Moradi
- Institute of Clinical Neurobiology, University Hospital Wuerzburg, 97078, Würzburg, Germany.
| | - Michael Sendtner
- Institute of Clinical Neurobiology, University Hospital Wuerzburg, 97078, Würzburg, Germany.
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Kudryashova IV. Inhibitory Control of Short-Term Plasticity during Paired Pulse Stimulation Depends on Actin Polymerization. NEUROCHEM J+ 2022. [DOI: 10.1134/s1819712422020106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Murk K, Ornaghi M, Schiweck J. Profilin Isoforms in Health and Disease - All the Same but Different. Front Cell Dev Biol 2021; 9:681122. [PMID: 34458253 PMCID: PMC8387879 DOI: 10.3389/fcell.2021.681122] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 07/12/2021] [Indexed: 12/11/2022] Open
Abstract
Profilins are small actin binding proteins, which are structurally conserved throughout evolution. They are probably best known to promote and direct actin polymerization. However, they also participate in numerous cell biological processes beyond the roles typically ascribed to the actin cytoskeleton. Moreover, most complex organisms express several profilin isoforms. Their cellular functions are far from being understood, whereas a growing number of publications indicate that profilin isoforms are involved in the pathogenesis of various diseases. In this review, we will provide an overview of the profilin family and "typical" profilin properties including the control of actin dynamics. We will then discuss the profilin isoforms of higher animals in detail. In terms of cellular functions, we will focus on the role of Profilin 1 (PFN1) and Profilin 2a (PFN2a), which are co-expressed in the central nervous system. Finally, we will discuss recent findings that link PFN1 and PFN2a to neurological diseases, such as amyotrophic lateral sclerosis (ALS), Fragile X syndrome (FXS), Huntington's disease and spinal muscular atrophy (SMA).
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Affiliation(s)
- Kai Murk
- Institute of Biochemistry, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Marta Ornaghi
- Institute of Biochemistry, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Juliane Schiweck
- Institute of Biochemistry, Charité Universitätsmedizin Berlin, Berlin, Germany
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8
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George S, Chiou TT, Kanamalla K, De Blas AL. Recruitment of Plasma Membrane GABA-A Receptors by Submembranous Gephyrin/Collybistin Clusters. Cell Mol Neurobiol 2021; 42:1585-1604. [PMID: 33547626 DOI: 10.1007/s10571-021-01050-1] [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: 08/20/2020] [Accepted: 01/23/2021] [Indexed: 11/29/2022]
Abstract
It has been shown that subunit composition is the main determinant of the synaptic or extrasynaptic localization of GABAA receptors (GABAARs). Synaptic and extrasynaptic GABAARs are involved in phasic and tonic inhibition, respectively. It has been proposed that synaptic GABAARs bind to the postsynaptic gephyrin/collybistin (Geph/CB) lattice, but not the typically extrasynaptic GABAARs. Nevertheless, there are no studies of the direct binding of various types of GABAARs with the submembranous Geph/CB lattice in the absence of other synaptic proteins, some of which are known to interact with GABAARs. We have reconstituted GABAARs of various subunit compositions, together with the Geph/CB scaffold, in HEK293 cells, and have investigated the recruitment of surface GABAARs by submembranous Geph/CB clusters. Results show that the typically synaptic α1β3γ2 GABAARs were trapped by submembranous Geph/CB clusters. The α5β3γ2 GABAARs, which are both synaptic and extrasynaptic, were also trapped by Geph/CB clusters. Extrasynaptic α4β3δ GABAARs consistently showed little or no trapping by the Geph/CB clusters. However, the extrasynaptic α6β3δ, α1β3, α6β3 (and less α4β3) GABAARs were highly trapped by the Geph/CB clusters. AMPA and NMDA glutamate receptors were not trapped. The results suggest: (I) in the absence of other synaptic molecules, the Geph/CB lattice has the capacity to trap not only synaptic but also several typically extrasynaptic GABAARs; (II) the Geph/CB lattice is important but does not play a decisive role in the synaptic localization of GABAARs; and (III) in neurons there must be mechanisms preventing the trapping of several typically extrasynaptic GABAARs by the postsynaptic Geph/CB lattice.
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Affiliation(s)
- Shanu George
- Department of Physiology and Neurobiology, University of Connecticut, 75 North Eagleville Road, U-3156, Storrs, CT, 06269-3156, USA
| | - Tzu-Ting Chiou
- Department of Physiology and Neurobiology, University of Connecticut, 75 North Eagleville Road, U-3156, Storrs, CT, 06269-3156, USA
| | - Karthik Kanamalla
- Department of Physiology and Neurobiology, University of Connecticut, 75 North Eagleville Road, U-3156, Storrs, CT, 06269-3156, USA
| | - Angel L De Blas
- Department of Physiology and Neurobiology, University of Connecticut, 75 North Eagleville Road, U-3156, Storrs, CT, 06269-3156, USA.
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9
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Pizzarelli R, Griguoli M, Zacchi P, Petrini EM, Barberis A, Cattaneo A, Cherubini E. Tuning GABAergic Inhibition: Gephyrin Molecular Organization and Functions. Neuroscience 2020; 439:125-136. [PMID: 31356900 PMCID: PMC7351109 DOI: 10.1016/j.neuroscience.2019.07.036] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Revised: 07/16/2019] [Accepted: 07/17/2019] [Indexed: 01/15/2023]
Abstract
To be highly reliable, synaptic transmission needs postsynaptic receptors (Rs) in precise apposition to the presynaptic release sites. At inhibitory synapses, the postsynaptic protein gephyrin self-assembles to form a scaffold that anchors glycine and GABAARs to the cytoskeleton, thus ensuring the accurate accumulation of postsynaptic receptors at the right place. This protein undergoes several post-translational modifications which control protein-protein interaction and downstream signaling pathways. In addition, through the constant exchange of scaffolding elements and receptors in and out of synapses, gephyrin dynamically regulates synaptic strength and plasticity. The aim of the present review is to highlight recent findings on the functional role of gephyrin at GABAergic inhibitory synapses. We will discuss different approaches used to interfere with gephyrin in order to unveil its function. In addition, we will focus on the impact of gephyrin structure and distribution at the nanoscale level on the functional properties of inhibitory synapses as well as the implications of this scaffold protein in synaptic plasticity processes. Finally, we will emphasize how gephyrin genetic mutations or alterations in protein expression levels are implicated in several neuropathological disorders, including autism spectrum disorders, schizophrenia, temporal lobe epilepsy and Alzheimer's disease, all associated with severe deficits of GABAergic signaling. This article is part of a Special Issue entitled: Honoring Ricardo Miledi - outstanding neuroscientist of XX-XXI centuries.
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Affiliation(s)
- Rocco Pizzarelli
- European Brain Research Institute (EBRI), Fondazione Rita Levi-Montalcini, Roma, Italy
| | - Marilena Griguoli
- European Brain Research Institute (EBRI), Fondazione Rita Levi-Montalcini, Roma, Italy
| | - Paola Zacchi
- Department of Life Sciences, University of Trieste, Trieste, Italy
| | - Enrica Maria Petrini
- Fondazione Istituto Italiano di Tecnologia (IIT), Department of Neuroscience and Brain Technologies, Plasticity of inhibitory networks Unit, Genoa, Italy
| | - Andrea Barberis
- Fondazione Istituto Italiano di Tecnologia (IIT), Department of Neuroscience and Brain Technologies, Plasticity of inhibitory networks Unit, Genoa, Italy
| | - Antonino Cattaneo
- European Brain Research Institute (EBRI), Fondazione Rita Levi-Montalcini, Roma, Italy; Scuola Normale Superiore, Pisa, Italy
| | - Enrico Cherubini
- European Brain Research Institute (EBRI), Fondazione Rita Levi-Montalcini, Roma, Italy; Scuola Internazionale Superiore di Studi Avanzati, Trieste, Italy.
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10
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McNeill EM, Thompson C, Berke B, Chou VT, Rusch J, Duckworth A, DeProto J, Taylor A, Gates J, Gertler F, Keshishian H, Van Vactor D. Drosophila enabled promotes synapse morphogenesis and regulates active zone form and function. Neural Dev 2020; 15:4. [PMID: 32183907 PMCID: PMC7076993 DOI: 10.1186/s13064-020-00141-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2020] [Accepted: 02/25/2020] [Indexed: 11/10/2022] Open
Abstract
Background Recent studies of synapse form and function highlight the importance of the actin cytoskeleton in regulating multiple aspects of morphogenesis, neurotransmission, and neural plasticity. The conserved actin-associated protein Enabled (Ena) is known to regulate development of the Drosophila larval neuromuscular junction through a postsynaptic mechanism. However, the functions and regulation of Ena within the presynaptic terminal has not been determined. Methods Here, we use a conditional genetic approach to address a presynaptic role for Ena on presynaptic morphology and ultrastructure, and also examine the pathway in which Ena functions through epistasis experiments. Results We find that Ena is required to promote the morphogenesis of presynaptic boutons and branches, in contrast to its inhibitory role in muscle. Moreover, while postsynaptic Ena is regulated by microRNA-mediated mechanisms, presynaptic Ena relays the output of the highly conserved receptor protein tyrosine phosphatase Dlar and associated proteins including the heparan sulfate proteoglycan Syndecan, and the non-receptor Abelson tyrosine kinase to regulate addition of presynaptic varicosities. Interestingly, Ena also influences active zones, where it restricts active zone size, regulates the recruitment of synaptic vesicles, and controls the amplitude and frequency of spontaneous glutamate release. Conclusion We thus show that Ena, under control of the Dlar pathway, is required for presynaptic terminal morphogenesis and bouton addition and that Ena has active zone and neurotransmission phenotypes. Notably, in contrast to Dlar, Ena appears to integrate multiple pathways that regulate synapse form and function.
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Affiliation(s)
- Elizabeth M McNeill
- Department of Food Science and Human Nutrition, Iowa State University, Ames, IA, USA.
| | - Cheryl Thompson
- Department of Cell Biology and Program in Neuroscience, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
| | - Brett Berke
- Department of Biology, Yale University, New Haven, CT, USA
| | - Vivian T Chou
- Department of Cell Biology and Program in Neuroscience, Blavatnik Institute, Harvard Medical School, Boston, MA, USA.
| | - Jannette Rusch
- Department of Cell Biology and Program in Neuroscience, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
| | - April Duckworth
- Department of Cell Biology and Program in Neuroscience, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
| | - Jamin DeProto
- Department of Cell Biology and Program in Neuroscience, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
| | - Alicia Taylor
- Department of Food Science and Human Nutrition, Iowa State University, Ames, IA, USA.,Department of Cell Biology and Program in Neuroscience, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
| | - Julie Gates
- Department of Biology, Bucknell University, Lewisburg, PA, USA
| | - Frank Gertler
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, England
| | | | - David Van Vactor
- Department of Cell Biology and Program in Neuroscience, Blavatnik Institute, Harvard Medical School, Boston, MA, USA.
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11
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Maynard SA, Triller A. Inhibitory Receptor Diffusion Dynamics. Front Mol Neurosci 2019; 12:313. [PMID: 31920541 PMCID: PMC6930922 DOI: 10.3389/fnmol.2019.00313] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Accepted: 12/04/2019] [Indexed: 11/13/2022] Open
Abstract
The dynamic modulation of receptor diffusion-trapping at inhibitory synapses is crucial to synaptic transmission, stability, and plasticity. In this review article, we will outline the progression of understanding of receptor diffusion dynamics at the plasma membrane. We will discuss how regulation of reversible trapping of receptor-scaffold interactions in combination with theoretical modeling approaches can be used to quantify these chemical interactions at the postsynapse of living cells.
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Affiliation(s)
- Stephanie A Maynard
- Institute of Biology of Ecole Normale Supérieure (IBENS), PSL Research University, CNRS, Inserm, Paris, France
| | - Antoine Triller
- Institute of Biology of Ecole Normale Supérieure (IBENS), PSL Research University, CNRS, Inserm, Paris, France
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12
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Bucher M, Fanutza T, Mikhaylova M. Cytoskeletal makeup of the synapse: Shaft versus spine. Cytoskeleton (Hoboken) 2019; 77:55-64. [PMID: 31762205 DOI: 10.1002/cm.21583] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Revised: 11/20/2019] [Accepted: 11/21/2019] [Indexed: 12/13/2022]
Abstract
The ability of neurons to communicate and store information depends on the activity of synapses which can be located on small protrusions (dendritic spines) or directly on the dendritic shaft. The formation, plasticity, and stability of synapses are regulated by the neuronal cytoskeleton. Actin filaments together with microtubules, neurofilaments, septins, and scaffolding proteins orchestrate the structural organization of both shaft and spine synapses, enabling their efficacy in response to synaptic activation. Synapses critically depend on several factors, which are also mediated by the cytoskeleton, including transport and delivery of proteins from the soma, protein synthesis, as well as surface diffusion of membrane proteins. In this minireview, we focus on recent progress made in the field of cytoskeletal elements of the postsynapse and discuss the differences and similarities between synapses located in the spines versus dendritic shaft.
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Affiliation(s)
- Michael Bucher
- DFG Emmy Noether Group 'Neuronal Protein Transport', Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Tomas Fanutza
- DFG Emmy Noether Group 'Neuronal Protein Transport', Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Marina Mikhaylova
- DFG Emmy Noether Group 'Neuronal Protein Transport', Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
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13
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Shen ZC, Wu PF, Wang F, Xia ZX, Deng Q, Nie TL, Zhang SQ, Zheng HL, Liu WH, Lu JJ, Gao SQ, Yao XP, Long LH, Hu ZL, Chen JG. Gephyrin Palmitoylation in Basolateral Amygdala Mediates the Anxiolytic Action of Benzodiazepine. Biol Psychiatry 2019; 85:202-213. [PMID: 30454851 DOI: 10.1016/j.biopsych.2018.09.024] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2018] [Revised: 08/31/2018] [Accepted: 09/04/2018] [Indexed: 11/25/2022]
Abstract
BACKGROUND Benzodiazepines (BZDs) have been used to treat anxiety disorders for more than five decades as the allosteric modulator of the gamma-aminobutyric acid A receptor (GABAAR). Little is known about other mechanisms of BZDs. Here, we describe how the rapid stabilization of postsynaptic GABAAR is essential and sufficient for the anxiolytic effect of BZDs via a palmitoylation-dependent mechanism. METHODS Palmitoylated proteins in the basolateral amygdala (BLA) of rats with different anxious states were assessed by a biotin exchange protocol. Both pharmacological and genetic approaches were used to investigate the role of palmitoylation in anxiety behavior. Electrophysiological recording, reverse transcription polymerase chain reaction, Western blotting, and coimmunoprecipitation were used to investigate the mechanisms. RESULTS Highly anxious rats were accompanied by the deficiency of gephyrin palmitoylation and decreased the synaptic function of GABAAR in the BLA. We then identified that the dysfunction of DHHC12, a palmitoyl acyltransferase that specifically palmitoylates gephyrin, contributed to the high-anxious state. Furthermore, diazepam, as an anxiolytic drug targeting GABAARs, was found to increase gephyrin palmitoylation in the BLA via a GABAAR-dependent manner to activate DHHC12. The anxiolytic effect of diazepam was nearly abolished by the DHHC12 knockdown. Specifically, similar to the effect of BZD, the overexpression of DHHC12 in the BLA exerted a significant anxiolytic action, which was prevented by flumazenil. CONCLUSIONS Our results support the view that the strength of inhibitory synapse was controlled by gephyrin palmitoylation in vivo and proposes a previously unknown palmitoylation-centered mode of BZD's action.
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Affiliation(s)
- Zu-Cheng Shen
- 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, 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; Key Laboratory of Neurological Diseases, Ministry of Education of China, 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, 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; Collaborative-Innovation Center for Brain Science, Wuhan, China; Key Laboratory of Neurological Diseases, Ministry of Education of China, Wuhan, China.
| | - Zhi-Xuan Xia
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Qiao Deng
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Tai-Lei Nie
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Shao-Qi Zhang
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Hui-Ling Zheng
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Wen-Hui Liu
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Jia-Jing Lu
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Shuang-Qi Gao
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Xia-Ping Yao
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, 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, 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; Key Laboratory of Neurological Diseases, Ministry of Education of China, 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, 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; Key Laboratory of Neurological Diseases, Ministry of Education of China, 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, 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; Collaborative-Innovation Center for Brain Science, Wuhan, China; Key Laboratory of Neurological Diseases, Ministry of Education of China, Wuhan, China.
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14
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Groeneweg FL, Trattnig C, Kuhse J, Nawrotzki RA, Kirsch J. Gephyrin: a key regulatory protein of inhibitory synapses and beyond. Histochem Cell Biol 2018; 150:489-508. [DOI: 10.1007/s00418-018-1725-2] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/07/2018] [Indexed: 12/26/2022]
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15
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Kasaragod VB, Schindelin H. Structure-Function Relationships of Glycine and GABA A Receptors and Their Interplay With the Scaffolding Protein Gephyrin. Front Mol Neurosci 2018; 11:317. [PMID: 30258351 PMCID: PMC6143783 DOI: 10.3389/fnmol.2018.00317] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Accepted: 08/16/2018] [Indexed: 12/03/2022] Open
Abstract
Glycine and γ-aminobutyric acid (GABA) are the major determinants of inhibition in the central nervous system (CNS). These neurotransmitters target glycine and GABAA receptors, respectively, which both belong to the Cys-loop superfamily of pentameric ligand-gated ion channels (pLGICs). Interactions of the neurotransmitters with the cognate receptors result in receptor opening and a subsequent influx of chloride ions, which, in turn, leads to hyperpolarization of the membrane potential, thus counteracting excitatory stimuli. The majority of glycine receptors and a significant fraction of GABAA receptors (GABAARs) are recruited and anchored to the post-synaptic membrane by the central scaffolding protein gephyrin. This ∼93 kDa moonlighting protein is structurally organized into an N-terminal G-domain (GephG) connected to a C-terminal E-domain (GephE) via a long unstructured linker. Both inhibitory neurotransmitter receptors interact via a short peptide motif located in the large cytoplasmic loop located in between transmembrane helices 3 and 4 (TM3-TM4) of the receptors with a universal receptor-binding epitope residing in GephE. Gephyrin engages in nearly identical interactions with the receptors at the N-terminal end of the peptide motif, and receptor-specific interaction toward the C-terminal region of the peptide. In addition to its receptor-anchoring function, gephyrin also interacts with a rather large collection of macromolecules including different cytoskeletal elements, thus acting as central scaffold at inhibitory post-synaptic specializations. Dysfunctions in receptor-mediated or gephyrin-mediated neurotransmission have been identified in various severe neurodevelopmental disorders. Although biochemical, cellular and electrophysiological studies have helped to understand the physiological and pharmacological roles of the receptors, recent high resolution structures of the receptors have strengthened our understanding of the receptors and their gating mechanisms. Besides that, multiple crystal structures of GephE in complex with receptor-derived peptides have shed light into receptor clustering by gephyrin at inhibitory post-synapses. This review will highlight recent biochemical and structural insights into gephyrin and the GlyRs as well as GABAA receptors, which provide a deeper understanding of the molecular machinery mediating inhibitory neurotransmission.
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Affiliation(s)
- Vikram B Kasaragod
- Institute of Structural Biology, Rudolf Virchow Center for Experimental Biomedicine, University of Würzburg, Würzburg, Germany
| | - Hermann Schindelin
- Institute of Structural Biology, Rudolf Virchow Center for Experimental Biomedicine, University of Würzburg, Würzburg, Germany
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16
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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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17
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Wu CH, Giampetruzzi A, Tran H, Fallini C, Gao FB, Landers JE. A Drosophila model of ALS reveals a partial loss of function of causative human PFN1 mutants. Hum Mol Genet 2017; 26:2146-2155. [PMID: 28379367 DOI: 10.1093/hmg/ddx112] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Accepted: 03/16/2017] [Indexed: 01/04/2023] Open
Abstract
Mutations in the profilin 1 (PFN1) gene are causative for familial amyotrophic lateral sclerosis (fALS). However, it is still not fully understood how these mutations lead to neurodegeneration. To address this question, we generated a novel Drosophila model expressing human wild-type and ALS-causative PFN1 mutants. We show that at larval neuromuscular junctions (NMJ), motor neuron expression of wild-type human PFN1 increases the number of ghost boutons, active zone density, F-actin content, and the formation of filopodia. In contrast, the expression of ALS-causative human PFN1 mutants causes a less pronounced phenotype, suggesting a loss of function of these mutants in promoting NMJ remodeling. Importantly, expression of human PFN1 in motor neurons results in progressive locomotion defects and shorter lifespan in adult flies, while ALS-causative PFN1 mutants display a less toxic effect. In summary, our study provides evidence that PFN1 is important in regulating NMJ morphology and influences survival and locomotion in Drosophila. Furthermore, our results suggest ALS-causative human PFN1 mutants display a partial loss of function relative to wild-type hPFN1 that may contribute to human disease pathogenesis.
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Affiliation(s)
- Chi-Hong Wu
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Anthony Giampetruzzi
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Helene Tran
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Claudia Fallini
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Fen-Biao Gao
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - John E Landers
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA 01605, USA
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18
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Vidaki M, Drees F, Saxena T, Lanslots E, Taliaferro MJ, Tatarakis A, Burge CB, Wang ET, Gertler FB. A Requirement for Mena, an Actin Regulator, in Local mRNA Translation in Developing Neurons. Neuron 2017; 95:608-622.e5. [PMID: 28735747 DOI: 10.1016/j.neuron.2017.06.048] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Revised: 05/17/2017] [Accepted: 06/29/2017] [Indexed: 12/16/2022]
Abstract
During neuronal development, local mRNA translation is required for axon guidance and synaptogenesis, and dysregulation of this process contributes to multiple neurodevelopmental and cognitive disorders. However, regulation of local protein synthesis in developing axons remains poorly understood. Here, we uncover a novel role for the actin-regulatory protein Mena in the formation of a ribonucleoprotein complex that involves the RNA-binding proteins HnrnpK and PCBP1 and regulates local translation of specific mRNAs in developing axons. We find that translation of dyrk1a, a Down syndrome- and autism spectrum disorders-related gene, is dependent on Mena, both in steady-state conditions and upon BDNF stimulation. We identify hundreds of additional mRNAs that associate with the Mena complex, suggesting that it plays broader role(s) in post-transcriptional gene regulation. Our work establishes a dual role for Mena in neurons, providing a potential link between regulation of actin dynamics and local translation.
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Affiliation(s)
- Marina Vidaki
- The Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
| | - Frauke Drees
- The Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Tanvi Saxena
- The Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Erwin Lanslots
- The Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Matthew J Taliaferro
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Antonios Tatarakis
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Christopher B Burge
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Eric T Wang
- The Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Frank B Gertler
- The Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
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19
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Hensel N, Claus P. The Actin Cytoskeleton in SMA and ALS: How Does It Contribute to Motoneuron Degeneration? Neuroscientist 2017; 24:54-72. [PMID: 28459188 DOI: 10.1177/1073858417705059] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA) are neurodegenerative diseases with overlapping clinical phenotypes based on impaired motoneuron function. However, the pathomechanisms of both diseases are largely unknown, and it is still unclear whether they converge on the molecular level. SMA is a monogenic disease caused by low levels of functional Survival of Motoneuron (SMN) protein, whereas ALS involves multiple genes as well as environmental factors. Recent evidence argues for involvement of actin regulation as a causative and dysregulated process in both diseases. ALS-causing mutations in the actin-binding protein profilin-1 as well as the ability of the SMN protein to directly bind to profilins argue in favor of a common molecular mechanism involving the actin cytoskeleton. Profilins are major regulat ors of actin-dynamics being involved in multiple neuronal motility and transport processes as well as modulation of synaptic functions that are impaired in models of both motoneuron diseases. In this article, we review the current literature in SMA and ALS research with a focus on the actin cytoskeleton. We propose a common molecular mechanism that explains the degeneration of motoneurons for SMA and some cases of ALS.
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Affiliation(s)
- Niko Hensel
- 1 Institute of Neuroanatomy and Cell Biology, Hannover Medical School, Hannover, Germany.,2 Niedersachsen Network on Neuroinfectiology (N-RENNT), Hannover, Germany
| | - Peter Claus
- 1 Institute of Neuroanatomy and Cell Biology, Hannover Medical School, Hannover, Germany.,2 Niedersachsen Network on Neuroinfectiology (N-RENNT), Hannover, Germany.,3 Center for Systems Neuroscience (ZSN), Hannover, Germany
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20
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Santiago-Medina M, Yang J. MENA Promotes Tumor-Intrinsic Metastasis through ECM Remodeling and Haptotaxis. Cancer Discov 2017; 6:474-6. [PMID: 27138561 DOI: 10.1158/2159-8290.cd-16-0231] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Oudin and colleagues report a novel and specific function of MENA in mediating directional migration of breast cancer cells toward a fibronectin gradient of increasing concentration. This MENA-mediated haptotactic response depends on the binding of MENA to the α5β1 integrin receptor, adhesion protein signaling, and fibronectin fibrillogenesis. Cancer Discov; 6(5); 474-6. ©2016 AACRSee related article by Oudin et al., p. 516.
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Affiliation(s)
- Miguel Santiago-Medina
- Department of Pharmacology, University of California, San Diego, La Jolla, California. Moores Cancer Center, University of California, San Diego, La Jolla, California.
| | - Jing Yang
- Department of Pharmacology, University of California, San Diego, La Jolla, California. Moores Cancer Center, University of California, San Diego, La Jolla, California. Department of Pediatrics, University of California, San Diego, La Jolla, California.
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21
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Uezu A, Kanak DJ, Bradshaw TWA, Soderblom EJ, Catavero CM, Burette AC, Weinberg RJ, Soderling SH. Identification of an elaborate complex mediating postsynaptic inhibition. Science 2017; 353:1123-9. [PMID: 27609886 DOI: 10.1126/science.aag0821] [Citation(s) in RCA: 217] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Accepted: 07/25/2016] [Indexed: 12/13/2022]
Abstract
Inhibitory synapses dampen neuronal activity through postsynaptic hyperpolarization. The composition of the inhibitory postsynapse and the mechanistic basis of its regulation, however, remain poorly understood. We used an in vivo chemico-genetic proximity-labeling approach to discover inhibitory postsynaptic proteins. Quantitative mass spectrometry not only recapitulated known inhibitory postsynaptic proteins but also revealed a large network of new proteins, many of which are either implicated in neurodevelopmental disorders or are of unknown function. Clustered regularly interspaced short palindromic repeats (CRISPR) depletion of one of these previously uncharacterized proteins, InSyn1, led to decreased postsynaptic inhibitory sites, reduced the frequency of miniature inhibitory currents, and increased excitability in the hippocampus. Our findings uncover a rich and functionally diverse assemblage of previously unknown proteins that regulate postsynaptic inhibition and might contribute to developmental brain disorders.
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Affiliation(s)
- Akiyoshi Uezu
- The Department of Cell Biology, Duke University Medical School, Durham, NC 27703, USA
| | - Daniel J Kanak
- The Department of Cell Biology, Duke University Medical School, Durham, NC 27703, USA
| | - Tyler W A Bradshaw
- The Department of Cell Biology, Duke University Medical School, Durham, NC 27703, USA
| | - Erik J Soderblom
- The Department of Cell Biology, Duke University Medical School, Durham, NC 27703, USA. Duke Proteomics and Metabolomics Shared Resource and Duke Center for Genomic and Computational Biology, Duke University Medical School, Durham, NC 27703, USA
| | - Christina M Catavero
- The Department of Cell Biology, Duke University Medical School, Durham, NC 27703, USA
| | - Alain C Burette
- Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC 27599, USA. Neuroscience Center, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Richard J Weinberg
- Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC 27599, USA. Neuroscience Center, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Scott H Soderling
- The Department of Cell Biology, Duke University Medical School, Durham, NC 27703, USA. The Department of Neurobiology, Duke University Medical School, Durham, NC 27703, USA.
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22
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Mele M, Leal G, Duarte CB. Role of GABAAR trafficking in the plasticity of inhibitory synapses. J Neurochem 2016; 139:997-1018. [DOI: 10.1111/jnc.13742] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Revised: 07/12/2016] [Accepted: 07/13/2016] [Indexed: 12/22/2022]
Affiliation(s)
- Miranda Mele
- Center for Neuroscience and Cell Biology; University of Coimbra; Coimbra Portugal
| | - Graciano Leal
- Center for Neuroscience and Cell Biology; University of Coimbra; Coimbra Portugal
| | - Carlos B. Duarte
- Center for Neuroscience and Cell Biology; University of Coimbra; Coimbra Portugal
- Department of Life Sciences; University of Coimbra; Coimbra Portugal
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23
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Alvarez FJ. Gephyrin and the regulation of synaptic strength and dynamics at glycinergic inhibitory synapses. Brain Res Bull 2016; 129:50-65. [PMID: 27612963 DOI: 10.1016/j.brainresbull.2016.09.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Revised: 08/23/2016] [Accepted: 09/05/2016] [Indexed: 01/23/2023]
Abstract
Glycinergic synapses predominate in brainstem and spinal cord where they modulate motor and sensory processing. Their postsynaptic mechanisms have been considered rather simple because they lack a large variety of glycine receptor isoforms and have relatively simple postsynaptic densities at the ultrastructural level. However, this simplicity is misleading being their postsynaptic regions regulated by a variety of complex mechanisms controlling the efficacy of synaptic inhibition. Early studies suggested that glycinergic inhibitory strength and dynamics depend largely on structural features rather than on molecular complexity. These include regulation of the number of postsynaptic glycine receptors, their localization and the amount of co-localized GABAA receptors and GABA-glycine co-transmission. These properties we now know are under the control of gephyrin. Gephyrin is the first postsynaptic scaffolding protein ever discovered and it was recently found to display a large degree of variation and regulation by splice variants, posttranslational modifications, intracellular trafficking and interactions with the underlying cytoskeleton. Many of these mechanisms are governed by converging excitatory activity and regulate gephyrin oligomerization and receptor binding, the architecture of the postsynaptic density (and by extension the whole synaptic complex), receptor retention and stability. These newly uncovered molecular mechanisms define the size and number of gephyrin postsynaptic regions and the numbers and proportions of glycine and GABAA receptors contained within. All together, they control the emergence of glycinergic synapses of different strength and temporal properties to best match the excitatory drive received by each individual neuron or local dendritic compartment.
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Affiliation(s)
- Francisco J Alvarez
- Department of Physiology, Emory University, Atlanta, GA 30322-3110, United States.
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24
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Kang J, Park H, Kim E. IRSp53/BAIAP2 in dendritic spine development, NMDA receptor regulation, and psychiatric disorders. Neuropharmacology 2015; 100:27-39. [PMID: 26275848 DOI: 10.1016/j.neuropharm.2015.06.019] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Revised: 06/26/2015] [Accepted: 06/28/2015] [Indexed: 01/08/2023]
Abstract
IRSp53 (also known as BAIAP2) is a multi-domain scaffolding and adaptor protein that has been implicated in the regulation of membrane and actin dynamics at subcellular structures, including filopodia and lamellipodia. Accumulating evidence indicates that IRSp53 is an abundant component of the postsynaptic density at excitatory synapses and an important regulator of actin-rich dendritic spines. In addition, IRSp53 has been implicated in diverse psychiatric disorders, including autism spectrum disorders, schizophrenia, and attention deficit/hyperactivity disorder. Mice lacking IRSp53 display enhanced NMDA (N-methyl-d-aspartate) receptor function accompanied by social and cognitive deficits, which are reversed by pharmacological suppression of NMDA receptor function. These results suggest the hypothesis that defective actin/membrane modulation in IRSp53-deficient dendritic spines may lead to social and cognitive deficits through NMDA receptor dysfunction. This article is part of the Special Issue entitled 'Synaptopathy--from Biology to Therapy'.
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Affiliation(s)
- Jaeseung Kang
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, South Korea
| | - Haram Park
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, South Korea
| | - Eunjoon Kim
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, South Korea; Center for Synaptic Brain Dysfunctions, Institute for Basic Science (IBS), Daejeon 305-701, South Korea.
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25
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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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26
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Protein kinase C-dependent growth-associated protein 43 phosphorylation regulates gephyrin aggregation at developing GABAergic synapses. Mol Cell Biol 2015; 35:1712-26. [PMID: 25755278 DOI: 10.1128/mcb.01332-14] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2014] [Accepted: 02/24/2015] [Indexed: 11/20/2022] Open
Abstract
Growth-associated protein 43 (GAP43) is known to regulate axon growth, but whether it also plays a role in synaptogenesis remains unclear. Here, we found that GAP43 regulates the aggregation of gephyrin, a pivotal protein for clustering postsynaptic GABA(A) receptors (GABA(A)Rs), in developing cortical neurons. Pharmacological blockade of either protein kinase C (PKC) or neuronal activity increased both GAP43-gephyrin association and gephyrin misfolding-induced aggregation, suggesting the importance of PKC-dependent regulation of GABAergic synapses. Furthermore, we found that PKC phosphorylation-resistant GAP43(S41A), but not PKC phosphorylation-mimicking GAP43(S41D), interacted with cytosolic gephyrin to trigger gephyrin misfolding and its sequestration into aggresomes. In contrast, GAP43(S41D), but not GAP43(S41A), inhibited the physiological aggregation/clustering of gephyrin, reduced surface GABA(A)Rs under physiological conditions, and attenuated gephyrin misfolding under transient oxygen-glucose deprivation (tOGD) that mimics pathological neonatal hypoxia. Calcineurin-mediated GAP43 dephosphorylation that accompanied tOGD also led to GAP43-gephyrin association and gephyrin misfolding. Thus, PKC-dependent phosphorylation of GAP43 plays a critical role in regulating postsynaptic gephyrin aggregation in developing GABAergic synapses.
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Molecular basis of the alternative recruitment of GABAA versus glycine receptors through gephyrin. Nat Commun 2014; 5:5767. [DOI: 10.1038/ncomms6767] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Accepted: 11/04/2014] [Indexed: 01/17/2023] Open
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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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Del Pino I, Koch D, Schemm R, Qualmann B, Betz H, Paarmann I. Proteomic analysis of glycine receptor β subunit (GlyRβ)-interacting proteins: evidence for syndapin I regulating synaptic glycine receptors. J Biol Chem 2014; 289:11396-11409. [PMID: 24509844 DOI: 10.1074/jbc.m113.504860] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Glycine receptors (GlyRs) mediate inhibitory neurotransmission in spinal cord and brainstem. They are clustered at inhibitory postsynapses via a tight interaction of their β subunits (GlyRβ) with the scaffolding protein gephyrin. In an attempt to isolate additional proteins interacting with GlyRβ, we performed pulldown experiments with rat brain extracts using a glutathione S-transferase fusion protein encompassing amino acids 378-455 of the large intracellular loop of GlyRβ as bait. This identified syndapin I (SdpI) as a novel interaction partner of GlyRβ that coimmunoprecipitates with native GlyRs from brainstem extracts. Both SdpI and SdpII bound efficiently to the intracellular loop of GlyRβ in vitro and colocalized with GlyRβ upon coexpression in COS-7 cells. The SdpI-binding site was mapped to a proline-rich sequence of 22 amino acids within the intracellular loop of GlyRβ. Deletion and point mutation analysis disclosed that SdpI binding to GlyRβ is Src homology 3 domain-dependent. In cultured rat spinal cord neurons, SdpI immunoreactivity was found to partially colocalize with marker proteins of inhibitory and excitatory synapses. When SdpI was acutely knocked down in cultured spinal cord neurons by viral miRNA expression, postsynaptic GlyR clusters were significantly reduced in both size and number. Similar changes in GlyR cluster properties were found in spinal cultures from SdpI-deficient mice. Our results are consistent with a role of SdpI in the trafficking and/or cytoskeletal anchoring of synaptic GlyRs.
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Affiliation(s)
- Isabel Del Pino
- Department of Neurochemistry, Max-Planck-Institute for Brain Research, D-60438 Frankfurt/Main
| | - Dennis Koch
- Institute for Biochemistry I, Jena University Hospital, Friedrich Schiller University Jena, D-07743 Jena
| | - Rudolf Schemm
- Department for Theoretical and Computational Biophysics, Max-Planck-Institute for Biophysical Chemistry, D-37077 Göttingen, and
| | - Britta Qualmann
- Institute for Biochemistry I, Jena University Hospital, Friedrich Schiller University Jena, D-07743 Jena
| | - Heinrich Betz
- Department of Neurochemistry, Max-Planck-Institute for Brain Research, D-60438 Frankfurt/Main,; Max-Planck Institute for Medical Research, 69120 Heidelberg, Germany.
| | - Ingo Paarmann
- Department of Neurochemistry, Max-Planck-Institute for Brain Research, D-60438 Frankfurt/Main,.
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Collybistin activation by GTP-TC10 enhances postsynaptic gephyrin clustering and hippocampal GABAergic neurotransmission. Proc Natl Acad Sci U S A 2013; 110:20795-800. [PMID: 24297911 DOI: 10.1073/pnas.1309078110] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
In many brain regions, gephyrin and GABAA receptor clustering at developing inhibitory synapses depends on the guanine nucleotide exchange factor collybistin (Cb). The vast majority of Cb splice variants contain an autoinhibitory src homology 3 domain, and several synaptic proteins are known to bind to this SH3 domain and to thereby activate gephyrin clustering. However, many functional GABAergic synapses form independently of the known Cb-activating proteins, indicating that additional Cb activators must exist. Here we show that the small Rho-like GTPase TC10 stimulates Cb-dependent gephyrin clustering by binding in its active, GTP-bound state to the pleckstrin homology domain of Cb. Overexpression of a constitutively active TC10 variant in neurons causes an increase in the density of synaptic gephyrin clusters and mean miniature inhibitory postsynaptic current amplitudes, whereas a dominant negative TC10 variant has opposite effects. The enhancement of Cb-induced gephyrin clustering by GTP-TC10 does not depend on the guanine nucleotide exchange activity of Cb but involves an interaction that resembles reported interactions of other small GTPases with their effectors. Our data indicate that GTP-TC10 activates the major src homology 3 domain-containing Cb variants by relieving autoinhibition and thus define an alternative GTPase-driven signaling pathway in the genesis of inhibitory synapses.
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Han K, Holder JL, Schaaf CP, Lu H, Chen H, Kang H, Tang J, Wu Z, Hao S, Cheung SW, Yu P, Sun H, Breman AM, Patel A, Lu HC, Zoghbi HY. SHANK3 overexpression causes manic-like behaviour with unique pharmacogenetic properties. Nature 2013; 503:72-7. [PMID: 24153177 PMCID: PMC3923348 DOI: 10.1038/nature12630] [Citation(s) in RCA: 262] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2013] [Accepted: 09/02/2013] [Indexed: 02/07/2023]
Abstract
Mutations in SHANK3 and large duplications of the region spanning SHANK3 both cause a spectrum of neuropsychiatric disorders, indicating that proper SHANK3 dosage is critical for normal brain function. However, SHANK3 overexpression per se has not been established as a cause of human disorders because 22q13 duplications involve several genes. Here we report that Shank3 transgenic mice modelling a human SHANK3 duplication exhibit manic-like behaviour and seizures consistent with synaptic excitatory/inhibitory imbalance. We also identified two patients with hyperkinetic disorders carrying the smallest SHANK3-spanning duplications reported so far. These findings indicate that SHANK3 overexpression causes a hyperkinetic neuropsychiatric disorder. To probe the mechanism underlying the phenotype, we generated a Shank3 in vivo interactome and found that Shank3 directly interacts with the Arp2/3 complex to increase F-actin levels in Shank3 transgenic mice. The mood-stabilizing drug valproate, but not lithium, rescues the manic-like behaviour of Shank3 transgenic mice raising the possibility that this hyperkinetic disorder has a unique pharmacogenetic profile.
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Affiliation(s)
- Kihoon Han
- 1] Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA [2] Howard Hughes Medical Institute, Baylor College of Medicine, Houston, Texas 77030, USA [3] Jan and Dan Duncan Neurological Research Institute at Texas Children's Hospital, Houston, Texas 77030, USA
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Effects of two elongation factor 1A isoforms on the formation of gephyrin clusters at inhibitory synapses in hippocampal neurons. Histochem Cell Biol 2013; 140:603-9. [DOI: 10.1007/s00418-013-1122-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/15/2013] [Indexed: 10/26/2022]
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Murk K, Wittenmayer N, Michaelsen-Preusse K, Dresbach T, Schoenenberger CA, Korte M, Jockusch BM, Rothkegel M. Neuronal profilin isoforms are addressed by different signalling pathways. PLoS One 2012; 7:e34167. [PMID: 22470532 PMCID: PMC3314592 DOI: 10.1371/journal.pone.0034167] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Accepted: 02/23/2012] [Indexed: 01/29/2023] Open
Abstract
Profilins are prominent regulators of actin dynamics. While most mammalian cells express only one profilin, two isoforms, PFN1 and PFN2a are present in the CNS. To challenge the hypothesis that the expression of two profilin isoforms is linked to the complex shape of neurons and to the activity-dependent structural plasticity, we analysed how PFN1 and PFN2a respond to changes of neuronal activity. Simultaneous labelling of rodent embryonic neurons with isoform-specific monoclonal antibodies revealed both isoforms in the same synapse. Immunoelectron microscopy on brain sections demonstrated both profilins in synapses of the mature rodent cortex, hippocampus and cerebellum. Both isoforms were significantly more abundant in postsynaptic than in presynaptic structures. Immunofluorescence showed PFN2a associated with gephyrin clusters of the postsynaptic active zone in inhibitory synapses of embryonic neurons. When cultures were stimulated in order to change their activity level, active synapses that were identified by the uptake of synaptotagmin antibodies, displayed significantly higher amounts of both isoforms than non-stimulated controls. Specific inhibition of NMDA receptors by the antagonist APV in cultured rat hippocampal neurons resulted in a decrease of PFN2a but left PFN1 unaffected. Stimulation by the brain derived neurotrophic factor (BDNF), on the other hand, led to a significant increase in both synaptic PFN1 and PFN2a. Analogous results were obtained for neuronal nuclei: both isoforms were localized in the same nucleus, and their levels rose significantly in response to KCl stimulation, whereas BDNF caused here a higher increase in PFN1 than in PFN2a. Our results strongly support the notion of an isoform specific role for profilins as regulators of actin dynamics in different signalling pathways, in excitatory as well as in inhibitory synapses. Furthermore, they suggest a functional role for both profilins in neuronal nuclei.
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Affiliation(s)
- Kai Murk
- Cellular Neurobiology, Zoological Institute, TU Braunschweig, Braunschweig, Germany
| | - Nina Wittenmayer
- Department of Anatomy and Cell Biology, Center of Anatomy, Georg August University Göttingen, Göttingen, Germany
| | | | - Thomas Dresbach
- Department of Anatomy and Cell Biology, Center of Anatomy, Georg August University Göttingen, Göttingen, Germany
| | | | - Martin Korte
- Cellular Neurobiology, Zoological Institute, TU Braunschweig, Braunschweig, Germany
| | | | - Martin Rothkegel
- Cellular Neurobiology, Zoological Institute, TU Braunschweig, Braunschweig, Germany
- * E-mail:
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Herweg J, Schwarz G. Splice-specific glycine receptor binding, folding, and phosphorylation of the scaffolding protein gephyrin. J Biol Chem 2012; 287:12645-56. [PMID: 22351777 DOI: 10.1074/jbc.m112.341826] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The multimeric scaffolding protein gephyrin forms post-synaptic clusters at inhibitory sites, thereby anchoring inhibitory glycine (GlyR) and subsets of γ-aminobutyric acid type A (GABAA) receptors. Gephyrin is composed of three domains, the conserved N-terminal G- and C-terminal E-domain, connected by the central (C-) domain. In this study we investigated the oligomerization, folding and stability, GlyR β-loop binding, and phosphorylation of three gephyrin splice variants (Geph, Geph-C3, Geph-C4) after expression and purification from insect cells (Sf9). In contrast to Escherichia coli-derived trimeric gephyrin, we found that Sf9 gephyrins form hexamers as basic oligomeric form. In the case of Geph and Geph-C4, also high-oligomeric forms (∼900 kDa) were isolated. Partial proteolysis revealed a compact folding of the Gephyrin G and C domain in one complex, whereas a much lower stability for the E domain was found. After GlyR β-loop binding, the stability of the E domain increased in Geph and Geph-C4 significantly. In contrast, the E domain in Geph-C3 is less stable and binds the GlyR β-loop with one order of magnitude lower affinity. Finally, we identified 18 novel phosphorylation sites in gephyrin, of which all except one are located within the C domain. We propose two models for the domain arrangement in hexameric gephyrin based on the oligomerization of either the E or C domains, with the latter being crucial for the regulation of gephyrin clustering.
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Affiliation(s)
- Jens Herweg
- Institute of Biochemistry, Department of Chemistry and Center for Molecular Medicine, University of Cologne, 50674 Cologne, Germany
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Expression and subcellular distribution of gephyrin in non-neuronal tissues and cells. Histochem Cell Biol 2012; 137:471-82. [PMID: 22270318 DOI: 10.1007/s00418-012-0914-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/05/2012] [Indexed: 10/14/2022]
Abstract
Gephyrin is a scaffolding protein required for the accumulation of inhibitory neurotransmitter receptors at neuronal postsynaptic membranes. In non-neuronal tissues, gephyrin is indispensible for the biosynthesis of molybdenum cofactor, the prosthetic group of oxidoreductases including sulfite oxidase and xanthine oxidase. However, the molecular and cellular basis of gephyrin's non-neuronal function is poorly understood; in particular, the roles of its splice variants remain enigmatic. Here, we used cDNA screening as well as Northern and immunoblot analyses to show that mammalian liver contains only a limited number of gephyrin splice variants, with the C3-containing variant being the predominant isoform. Using new and established anti-gephyrin antibodies in immunofluorescence and subcellular fractionation studies, we report that gephyrin localizes to the cytoplasm of both tissue hepatocytes and cultured immortalized cells. These findings were corroborated by RNA interference studies in which the cytosolic distribution was found to be abolished. Finally, by blue-native PAGE we show that cytoplasmic gephyrin is part of a ~600 kDa protein complex of yet unknown composition. Our data suggest that the expression pattern of non-neuronal gephyrin is simpler than indicated by previous evidence. In addition, gephyrin's presence in a cytosolic 600 kDa protein complex suggests that its metabolic and/or other non-neuronal functions are exerted in the cytoplasm and are not confined to a particular subcellular compartment.
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Maric HM, Mukherjee J, Tretter V, Moss SJ, Schindelin H. Gephyrin-mediated γ-aminobutyric acid type A and glycine receptor clustering relies on a common binding site. J Biol Chem 2011; 286:42105-42114. [PMID: 22006921 DOI: 10.1074/jbc.m111.303412] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Gephyrin is the major protein determinant for the clustering of inhibitory neurotransmitter receptors. Earlier analyses revealed that gephyrin tightly binds to residues 398-410 of the glycine receptor β subunit (GlyR β) and, as demonstrated only recently, also interacts with GABA(A) receptors (GABA(A)Rs) containing the α1, α2, and α3 subunits. Here, we dissect the molecular basis underlying the interactions between gephyrin and GABA(A)Rs containing these α-subunits and compare them to the crystal structure of the gephyrin-GlyR β complex. Biophysical and biochemical assays revealed that, in contrast to its tight interaction with GlyR β, gephyrin only loosely interacts with GABA(A)R α2, whereas it has an intermediate affinity for the GABA(A)R α1 and α3 subunits. Despite the wide variation in affinities and the low overall sequence homology among the identified receptor subunits, competition assays confirmed the receptor-gephyrin interaction to be a mutually exclusive process. Selected gephyrin point mutants that critically weaken complex formation with GlyR β also abolished the GABA(A)R α1 and α3 interactions. Additionally, we identified a common binding motif with two conserved aromatic residues that are central for gephyrin binding. Consistent with the biochemical data, mutations of the corresponding residues within the cytoplasmic domain of α2 subunit-containing GABA(A)Rs attenuated clustering of these receptors at postsynaptic sites in hippocampal neurons. Taken together, our experiments provide key insights regarding similarities and differences in the complex formation between gephyrin and GABA(A)Rs compared with GlyRs and, hence, the accumulation of these receptors at postsynaptic sites.
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Affiliation(s)
- Hans-Michael Maric
- Rudolf Virchow Center for Experimental Biomedicine, Institute of Structural Biology, University of Würzburg, Josef-Schneider-Strasse 2, 97080 Würzburg, Germany
| | - Jayanta Mukherjee
- Department of Neuroscience, Tufts University, Boston, Massachusetts 02111
| | - Verena Tretter
- Department of Biochemistry and Molecular Biology, Medical University Vienna/Center for Brain Research, Spitalgasse 4, 1090 Vienna, Austria
| | - Stephen J Moss
- Department of Neuroscience, Tufts University, Boston, Massachusetts 02111
| | - Hermann Schindelin
- Rudolf Virchow Center for Experimental Biomedicine, Institute of Structural Biology, University of Würzburg, Josef-Schneider-Strasse 2, 97080 Würzburg, Germany.
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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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The biological role of the glycinergic synapse in early zebrafish motility. Neurosci Res 2011; 71:1-11. [PMID: 21712054 DOI: 10.1016/j.neures.2011.06.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2011] [Revised: 04/08/2011] [Accepted: 04/15/2011] [Indexed: 01/09/2023]
Abstract
Glycine mediates fast inhibitory neurotransmission in the spinal cord, brainstem and retina. Loss of synaptic glycinergic transmission in vertebrates leads to a severe locomotion defect characterized by an exaggerated startle response accompanied by transient muscle rigidity in response to sudden acoustic or tactile stimuli. Several molecular components of the glycinergic synapse have been characterized as an outcome of genetic and physiological analyses of synaptogenesis in mammals. Recently, the glycinergic synapse has been studied using a forward genetic approach in zebrafish. This review aims to discuss molecular components of the glycinergic synapse, such as glycine receptor subunits, gephyrin, gephyrin-binding proteins and glycine transporters, as well as recent studies relevant to the genetic analysis of the glycinergic synapse in zebrafish.
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Fukaya M, Kamata A, Hara Y, Tamaki H, Katsumata O, Ito N, Takeda S, Hata Y, Suzuki T, Watanabe M, Harvey RJ, Sakagami H. SynArfGEF is a guanine nucleotide exchange factor for Arf6 and localizes preferentially at post-synaptic specializations of inhibitory synapses. J Neurochem 2011; 116:1122-37. [PMID: 21198641 DOI: 10.1111/j.1471-4159.2010.07167.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
SynArfGEF, also known as BRAG3 or IQSEC3, is a member of the brefeldin A-resistant Arf-GEF/IQSEC family and was originally identified by screening for mRNA species associated with the post-synaptic density fraction. In this study, we demonstrate that synArfGEF activates Arf6, using Arf pull down and transferrin incorporation assays. Immunohistochemical analysis reveals that synArfGEF is present in somata and dendrites as puncta in close association with inhibitory synapses, whereas immunoelectron microscopic analysis reveals that synArfGEF localizes preferentially at post-synaptic specializations of symmetric synapses. Using yeast two-hybrid and pull down assays, we show that synArfGEF is able to bind utrophin/dystrophin and S-SCAM/MAGI-2 scaffolding proteins that localize at inhibitory synapses. Double immunostaining reveals that synArfGEF co-localizes with dystrophin and S-SCAM in cultured hippocampal neurons and cerebellar cortex, respectively. Both β-dystroglycan and S-SCAM were immunoprecipitated from brain lysates using anti-synArfGEF IgG. Taken together, these findings suggest that synArfGEF functions as a novel regulator of Arf6 at inhibitory synapses and associates with the dystrophin-associated glycoprotein complex and S-SCAM.
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Affiliation(s)
- Masahiro Fukaya
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara, Kanagawa, Japan
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Mondin M, Carta M, Normand E, Mulle C, Coussen F. Profilin II regulates the exocytosis of kainate glutamate receptors. J Biol Chem 2010; 285:40060-71. [PMID: 20937818 PMCID: PMC3000988 DOI: 10.1074/jbc.m110.140442] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2010] [Revised: 10/01/2010] [Indexed: 11/06/2022] Open
Abstract
The trafficking of ionotropic glutamate receptors to and from synaptic sites is regulated by proteins that interact with their cytoplasmic C-terminal domain. Profilin IIa (PfnIIa), an actin-binding protein expressed in the brain and recruited to synapses in an activity-dependent manner, was shown previously to interact with the C-terminal domain of the GluK2b subunit splice variant of kainate receptors (KARs). Here, we characterize this interaction and examine the role of PfnIIa in the regulation of KAR trafficking. PfnIIa directly and specifically binds to the C-terminal domain of GluK2b through a diproline motif. Expression of PfnIIa in transfected COS-7 cells and in cultured hippocampal neurons from PfnII-deficient mice decreases the level of extracellular of homomeric GluK2b as well as heteromeric GluK2a/GluK2b KARs. Our data suggest a novel mechanism by which PfnIIa exerts a dual role on the trafficking of KARs, by a generic inhibition of clathrin-mediated endocytosis through its interaction with dynamin-1, and by controlling KARs exocytosis through a direct and specific interaction with GluK2b.
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Affiliation(s)
- Magali Mondin
- From the Laboratoire Physiologie Cellulaire de la Synapse, CNRS UMR 5091, University of Bordeaux, 146 rue Léo Saignat, 33077 Bordeaux Cedex, France
| | - Mario Carta
- From the Laboratoire Physiologie Cellulaire de la Synapse, CNRS UMR 5091, University of Bordeaux, 146 rue Léo Saignat, 33077 Bordeaux Cedex, France
| | - Elisabeth Normand
- From the Laboratoire Physiologie Cellulaire de la Synapse, CNRS UMR 5091, University of Bordeaux, 146 rue Léo Saignat, 33077 Bordeaux Cedex, France
| | - Christophe Mulle
- From the Laboratoire Physiologie Cellulaire de la Synapse, CNRS UMR 5091, University of Bordeaux, 146 rue Léo Saignat, 33077 Bordeaux Cedex, France
| | - Françoise Coussen
- From the Laboratoire Physiologie Cellulaire de la Synapse, CNRS UMR 5091, University of Bordeaux, 146 rue Léo Saignat, 33077 Bordeaux Cedex, France
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Ogino K, Ramsden SL, Keib N, Schwarz G, Harvey RJ, Hirata H. Duplicated gephyrin genes showing distinct tissue distribution and alternative splicing patterns mediate molybdenum cofactor biosynthesis, glycine receptor clustering, and escape behavior in zebrafish. J Biol Chem 2010; 286:806-17. [PMID: 20843816 DOI: 10.1074/jbc.m110.125500] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Gephyrin mediates the postsynaptic clustering of glycine receptors (GlyRs) and GABA(A) receptors at inhibitory synapses and molybdenum-dependent enzyme (molybdoenzyme) activity in non-neuronal tissues. Gephyrin knock-out mice show a phenotype resembling both defective glycinergic transmission and molybdenum cofactor (Moco) deficiency and die within 1 day of birth due to starvation and dyspnea resulting from deficits in motor and respiratory networks, respectively. To address whether gephyrin function is conserved among vertebrates and whether gephyrin deficiency affects molybdoenzyme activity and motor development, we cloned and characterized zebrafish gephyrin genes. We report here that zebrafish have two gephyrin genes, gphna and gphnb. The former is expressed in all tissues and has both C3 and C4 cassette exons, and the latter is expressed predominantly in the brain and spinal cord and harbors only C4 cassette exons. We confirmed that all of the gphna and gphnb splicing isoforms have Moco synthetic activity. Antisense morpholino knockdown of either gphna or gphnb alone did not disturb synaptic clusters of GlyRs in the spinal cord and did not affect touch-evoked escape behaviors. However, on knockdown of both gphna and gphnb, embryos showed impairments in GlyR clustering in the spinal cord and, as a consequence, demonstrated touch-evoked startle response behavior by contracting antagonistic muscles simultaneously, instead of displaying early coiling and late swimming behaviors, which are executed by side-to-side muscle contractions. These data indicate that duplicated gephyrin genes mediate Moco biosynthesis and control postsynaptic clustering of GlyRs, thereby mediating key escape behaviors in zebrafish.
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Affiliation(s)
- Kazutoyo Ogino
- Center for Frontier Research, National Institute of Genetics, 1111 Yata, Mishima 411-8540, Japan
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Fukatsu K, Bannai H, Inoue T, Mikoshiba K. Lateral diffusion of inositol 1,4,5-trisphosphate receptor type 1 in Purkinje cells is regulated by calcium and actin filaments. J Neurochem 2010; 114:1720-33. [PMID: 20626556 DOI: 10.1111/j.1471-4159.2010.06885.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Inositol 1,4,5-trisphosphate receptor type 1 (IP(3) R1) is an intracellular Ca(2+) release channel that plays crucial roles in the functions of Purkinje cells. The dynamics of IP(3) R1 on the endoplasmic reticulum membrane and the distribution of IP(3) R1 in neurons are thought to be important for the spatial regulation of Ca(2+) release. In this study, we analyzed the lateral diffusion of IP(3) R1 in Purkinje cells in cerebellar slice cultures using fluorescence recovery after photobleaching. In the dendrites of Purkinje cells, IP(3) R1 showed lateral diffusion with an effective diffusion constant of approximately 0.30 μm(2) /s, and the diffusion of IP(3) R1 was negatively regulated by actin filaments. We found that actin filaments were also involved in the regulation of IP(3) R1 diffusion in the spine of Purkinje cells. Glutamate or quisqualic acid stimulation, which activates glutamate receptors and leads to a Ca(2+) transient in Purkinje cells, decreased the diffusion of IP(3) R1 and increased the density of actin in spines. These findings indicate that the neuronal activity-dependent augmentation of actin contributes to the stabilization of IP(3) R1 in spines.
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Affiliation(s)
- Kazumi Fukatsu
- Laboratory for Developmental Neurobiology, Brain Science Institute RIKEN, Wako, Saitama, Japan
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Gerrow K, Triller A. Synaptic stability and plasticity in a floating world. Curr Opin Neurobiol 2010; 20:631-9. [PMID: 20655734 DOI: 10.1016/j.conb.2010.06.010] [Citation(s) in RCA: 143] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2010] [Revised: 06/11/2010] [Accepted: 06/28/2010] [Indexed: 11/27/2022]
Abstract
A fundamental feature of membranes is the lateral diffusion of lipids and proteins. Control of lateral diffusion provides a mechanism for regulating the structure and function of synapses. Single-particle tracking (SPT) has emerged as a powerful way to directly visualize these movements. SPT can reveal complex diffusive behaviors, which can be regulated by neuronal activity over time and space. Such is the case for neurotransmitter receptors, which are transiently stabilized at synapses by scaffolding molecules. This regulation provides new insight into mechanisms by which the dynamic equilibrium of receptor-scaffold assembly can be regulated. We will briefly review here recent data on this mechanism, which ultimately tunes the number of receptors at synapses and therefore synaptic strength.
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Affiliation(s)
- Kimberly Gerrow
- Biologie Cellulaire de la Synapse, Institute de Biologie de l'Ecole Normale Supérieure, 46 rue d'Ulm, 75005 Paris, France
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Thomson AM, Jovanovic JN. Mechanisms underlying synapse-specific clustering of GABA(A) receptors. Eur J Neurosci 2010; 31:2193-203. [PMID: 20550567 DOI: 10.1111/j.1460-9568.2010.07252.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A principle that arises from a body of previous work is that each presynaptic terminal recognises its postsynaptic partner and that each postsynaptic site recognises the origin of the synaptic bouton innervating it. In response, the presynaptic terminal sequesters the proteins whose interactions result in the dynamic transmitter release pattern and chemical modulation appropriate for that connection. In parallel, the postsynaptic site sequesters, inserts or captures the receptors and postsynaptic density proteins appropriate for that type of synapse. The focus of this review is the selective clustering of GABA(A) receptors (GABA(A)R) at synapses made by each class of inhibitory interneurone. This provides a system in which the mechanisms underlying transynaptic recognition can be explored. There are many synaptic proteins, often with several isoforms created by post-translational modifications. Complex cascades of interactions between these proteins, on either side of the synaptic cleft, are essential for normal function, normal transmitter release and postsynaptic responsiveness. Interactions between presynaptic and postsynaptic proteins that have binding domains in the synaptic cleft are proposed here to result in a local cleft structure that captures and stabilises only the appropriate subtype of GABA(A)Rs, allowing others to drift away from that synapse, either to be captured by another synapse, or internalised.
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Affiliation(s)
- Alex M Thomson
- The School of Pharmacy, London University, 29-39 Brunswick Square, London WC1N 1AX, UK.
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Franco DL, Rezával C, Cáceres A, Schinder AF, Ceriani MF. ENA/VASP downregulation triggers cell death by impairing axonal maintenance in hippocampal neurons. Mol Cell Neurosci 2010; 44:154-64. [PMID: 20230896 DOI: 10.1016/j.mcn.2010.03.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2009] [Revised: 01/28/2010] [Accepted: 03/05/2010] [Indexed: 11/28/2022] Open
Abstract
Neurodegenerative diseases encompass a broad variety of motor and cognitive disorders that are accompanied by death of specific neuronal populations or brain regions. Cellular and molecular mechanisms underlying these complex disorders remain largely unknown. In a previous work we searched for novel Drosophila genes relevant for neurodegeneration and singled out enabled (ena), which encodes a protein involved in cytoskeleton remodeling. To extend our understanding on the mechanisms of ENA-triggered degeneration we now investigated the effect of silencing ena ortholog genes in mouse hippocampal neurons. We found that ENA/VASP downregulation led to neurite retraction and concomitant neuronal cell death through an apoptotic pathway. Remarkably, this retraction initially affected the axonal structure, showing no effect on dendrites. Reduction in ENA/VASP levels blocked the neuritogenic effect of a specific RhoA kinase (ROCK) inhibitor, thus suggesting that these proteins could participate in the Rho-signaling pathway. Altogether these observations demonstrate that ENA/VASP proteins are implicated in the establishment and maintenance of the axonal structure and that a change on their expression levels triggers neuronal degeneration.
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Affiliation(s)
- D Lorena Franco
- Laboratorio de Genética del Comportamiento, Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas-Buenos Aires (IIB-BA, CONICET), Argentina
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46
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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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Flavell SW, Kim TK, Gray JM, Harmin DA, Hemberg M, Hong EJ, Markenscoff-Papadimitriou E, Bear DM, Greenberg ME. Genome-wide analysis of MEF2 transcriptional program reveals synaptic target genes and neuronal activity-dependent polyadenylation site selection. Neuron 2009; 60:1022-38. [PMID: 19109909 DOI: 10.1016/j.neuron.2008.11.029] [Citation(s) in RCA: 359] [Impact Index Per Article: 23.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2008] [Revised: 06/20/2008] [Accepted: 11/13/2008] [Indexed: 01/17/2023]
Abstract
Although many transcription factors are known to control important aspects of neural development, the genome-wide programs that are directly regulated by these factors are not known. We have characterized the genetic program that is activated by MEF2, a key regulator of activity-dependent synapse development. These MEF2 target genes have diverse functions at synapses, revealing a broad role for MEF2 in synapse development. Several of the MEF2 targets are mutated in human neurological disorders including epilepsy and autism spectrum disorders, suggesting that these disorders may be caused by disruption of an activity-dependent gene program that controls synapse development. Our analyses also reveal that neuronal activity promotes alternative polyadenylation site usage at many of the MEF2 target genes, leading to the production of truncated mRNAs that may have different functions than their full-length counterparts. Taken together, these analyses suggest that the ubiquitously expressed transcription factor MEF2 regulates an intricate transcriptional program in neurons that controls synapse development.
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Affiliation(s)
- Steven W Flavell
- FM Kirby Neurobiology Center, Children's Hospital, and Department of Neurology and Neurobiology, Harvard Medical School, Boston, MA 02115, USA
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Higashi M, Ishikawa C, Yu J, Toyoda A, Kawana H, Kurokawa K, Matsuda M, Kitagawa M, Harigaya K. Human Mena associates with Rac1 small GTPase in glioblastoma cell lines. PLoS One 2009; 4:e4765. [PMID: 19277120 PMCID: PMC2651628 DOI: 10.1371/journal.pone.0004765] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2008] [Accepted: 02/06/2009] [Indexed: 11/18/2022] Open
Abstract
Mammarian enabled (Mena), a member of the Enabled (Ena)/Vasodilator-stimulated phosphoprotein (VASP) family of proteins, has been implicated in cell motility through regulation of the actin cytoskeleton assembly, including lamellipodial protrusion. Rac1, a member of the Rho family GTPases, also plays a pivotal role in the formation of lamellipodia. Here we report that human Mena (hMena) colocalizes with Rac1 in lamellipodia, and using an unmixing assisted acceptor depletion fluorescence resonance energy transfer (u-adFRET) analysis that hMena associates with Rac1 in vivo in the glioblastoma cell line U251MG. Depletion of hMena by siRNA causes cells to be highly spread with the formation of lamellipodia. This cellular phenotype is canceled by introduction of a dominant negative form of Rac1. A Rac activity assay and FRET analysis showed that hMena knock-down cells increased the activation of Rac1 at the lamellipodia. These results suggest that hMena possesses properties which help to regulate the formation of lamellipodia through the modulation of the activity of Rac1.
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Affiliation(s)
- Morihiro Higashi
- Molecular and Tumor Pathology, Chiba University Graduate School of Medicine, Chuo-ku, Chiba, Japan
| | - Chieko Ishikawa
- Molecular and Tumor Pathology, Chiba University Graduate School of Medicine, Chuo-ku, Chiba, Japan
| | - Jianyong Yu
- Molecular and Tumor Pathology, Chiba University Graduate School of Medicine, Chuo-ku, Chiba, Japan
| | - Akihiro Toyoda
- Molecular and Tumor Pathology, Chiba University Graduate School of Medicine, Chuo-ku, Chiba, Japan
| | - Hidetada Kawana
- Molecular and Tumor Pathology, Chiba University Graduate School of Medicine, Chuo-ku, Chiba, Japan
| | - Kazuo Kurokawa
- Molecular Membrane Biology Laboratory, RIKEN Discovery Research Institute, Wako, Saitama, Japan
| | - Michiyuki Matsuda
- Department of Pathology and Biology of Diseases, Graduate School of Medicine, Kyoto University, Konoe-cho, Yoshida Sakyo-ku, Kyoto, Japan
| | - Motoo Kitagawa
- Molecular and Tumor Pathology, Chiba University Graduate School of Medicine, Chuo-ku, Chiba, Japan
| | - Kenichi Harigaya
- Molecular and Tumor Pathology, Chiba University Graduate School of Medicine, Chuo-ku, Chiba, Japan
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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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Abstract
Thirty years after its initial characterization and more than 1000 publications listed in PubMed describing its properties, the small (ca 15 kDa) protein profilin continues to surprise us with new, recently discovered functions. Originally described as an actin-binding protein, profilin has now been shown to interact with more than a dozen proteins in mammalian cells. Some of the more recently described and intriguing interactions are within neurons involving a neuronal profilin family member. Profilin is now regarded as a regulator of various cellular processes such as cytoskeletal dynamics, membrane trafficking and nuclear transport. Profilin is a necessary element in key steps of neuronal differentiation and synaptic plasticity, and embodies properties postulated for a synaptic tag. These findings identify profilin as an important factor linking cellular and behavioural plasticity in neural circuits.
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Affiliation(s)
- Andreas Birbach
- Medical University of Vienna, Währingerstrasse 13a, A-1090 Vienna, Austria.
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