1
|
Twelvetrees AE, Lesept F, Holzbaur ELF, Kittler JT. The adaptor proteins HAP1a and GRIP1 collaborate to activate the kinesin-1 isoform KIF5C. J Cell Sci 2019; 132:jcs.215822. [PMID: 31757889 PMCID: PMC6955223 DOI: 10.1242/jcs.215822] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Accepted: 11/19/2019] [Indexed: 11/29/2022] Open
Abstract
Binding of motor proteins to cellular cargoes is regulated by adaptor proteins. HAP1 and GRIP1 are kinesin-1 adaptors that have been implicated individually in the transport of vesicular cargoes in the dendrites of neurons. We find that HAP1a and GRIP1 form a protein complex in the brain, and co-operate to activate the kinesin-1 subunit KIF5C in vitro. Based upon this co-operative activation of kinesin-1, we propose a modification to the kinesin activation model that incorporates stabilisation of the central hinge region known to be critical to autoinhibition of kinesin-1. Summary: The adaptor proteins HAP1a and GRIP1 form a protein complex in the brain, and co-operate to activate the kinesin-1 subunit KIF5C in vitro.
Collapse
Affiliation(s)
- Alison E Twelvetrees
- Sheffield Institute for Translational Neuroscience, Department of Neuroscience, University of Sheffield, Sheffield S10 2HQ, UK
| | - Flavie Lesept
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK
| | - Erika L F Holzbaur
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6085, USA
| | - Josef T Kittler
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK
| |
Collapse
|
2
|
Bissen D, Foss F, Acker-Palmer A. AMPA receptors and their minions: auxiliary proteins in AMPA receptor trafficking. Cell Mol Life Sci 2019; 76:2133-2169. [PMID: 30937469 PMCID: PMC6502786 DOI: 10.1007/s00018-019-03068-7] [Citation(s) in RCA: 63] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Revised: 02/12/2019] [Accepted: 03/07/2019] [Indexed: 12/12/2022]
Abstract
To correctly transfer information, neuronal networks need to continuously adjust their synaptic strength to extrinsic stimuli. This ability, termed synaptic plasticity, is at the heart of their function and is, thus, tightly regulated. In glutamatergic neurons, synaptic strength is controlled by the number and function of AMPA receptors at the postsynapse, which mediate most of the fast excitatory transmission in the central nervous system. Their trafficking to, at, and from the synapse, is, therefore, a key mechanism underlying synaptic plasticity. Intensive research over the last 20 years has revealed the increasing importance of interacting proteins, which accompany AMPA receptors throughout their lifetime and help to refine the temporal and spatial modulation of their trafficking and function. In this review, we discuss the current knowledge about the roles of key partners in regulating AMPA receptor trafficking and focus especially on the movement between the intracellular, extrasynaptic, and synaptic pools. We examine their involvement not only in basal synaptic function, but also in Hebbian and homeostatic plasticity. Included in our review are well-established AMPA receptor interactants such as GRIP1 and PICK1, the classical auxiliary subunits TARP and CNIH, and the newest additions to AMPA receptor native complexes.
Collapse
Affiliation(s)
- Diane Bissen
- Institute of Cell Biology and Neuroscience and Buchmann Institute for Molecular Life Sciences (BMLS), University of Frankfurt, Max-von-Laue-Str. 15, 60438, Frankfurt am Main, Germany
- Max Planck Institute for Brain Research, Max von Laue Str. 4, 60438, Frankfurt am Main, Germany
| | - Franziska Foss
- Institute of Cell Biology and Neuroscience and Buchmann Institute for Molecular Life Sciences (BMLS), University of Frankfurt, Max-von-Laue-Str. 15, 60438, Frankfurt am Main, Germany
| | - Amparo Acker-Palmer
- Institute of Cell Biology and Neuroscience and Buchmann Institute for Molecular Life Sciences (BMLS), University of Frankfurt, Max-von-Laue-Str. 15, 60438, Frankfurt am Main, Germany.
- Max Planck Institute for Brain Research, Max von Laue Str. 4, 60438, Frankfurt am Main, Germany.
- Cardio-Pulmonary Institute (CPI), Max-von-Laue-Str. 15, 60438, Frankfurt am Main, Germany.
| |
Collapse
|
3
|
Fernández-Montoya J, Buendia I, Martin YB, Egea J, Negredo P, Avendaño C. Sensory Input-Dependent Changes in Glutamatergic Neurotransmission- Related Genes and Proteins in the Adult Rat Trigeminal Ganglion. Front Mol Neurosci 2016; 9:132. [PMID: 27965535 PMCID: PMC5124698 DOI: 10.3389/fnmol.2016.00132] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2016] [Accepted: 11/11/2016] [Indexed: 11/13/2022] Open
Abstract
Experience-dependent plasticity induces lasting changes in the structure of synapses, dendrites, and axons at both molecular and anatomical levels. Whilst relatively well studied in the cortex, little is known about the molecular changes underlying experience-dependent plasticity at peripheral levels of the sensory pathways. Given the importance of glutamatergic neurotransmission in the somatosensory system and its involvement in plasticity, in the present study, we investigated gene and protein expression of glutamate receptor subunits and associated molecules in the trigeminal ganglion (TG) of young adult rats. Microarray analysis of naïve rat TG revealed significant differences in the expression of genes, coding for various glutamate receptor subunits and proteins involved in clustering and stabilization of AMPA receptors, between left and right ganglion. Long-term exposure to sensory-enriched environment increased this left–right asymmetry in gene expression. Conversely, unilateral whisker trimming on the right side almost eliminated the mentioned asymmetries. The above manipulations also induced side-specific changes in the protein levels of glutamate receptor subunits. Our results show that sustained changes in sensory input induce modifications in glutamatergic transmission-related gene expression in the TG, thus supporting a role for this early sensory-processing node in experience-dependent plasticity.
Collapse
Affiliation(s)
- Julia Fernández-Montoya
- Departamento de Anatomía, Histología y Neurociencia, Universidad Autónoma de Madrid Madrid, Spain
| | - Izaskun Buendia
- Instituto de Investigación Sanitaria, Hospital Universitario de La PrincesaMadrid, Spain; Departamento de Farmacología y Terapéutica, Instituto Teófilo Hernando, Universidad Autónoma de MadridMadrid, Spain
| | - Yasmina B Martin
- Departamento de Anatomía, Histología y Neurociencia, Universidad Autónoma de MadridMadrid, Spain; Departamento de Anatomía, Universidad Francisco de VitoriaMadrid, Spain
| | - Javier Egea
- Instituto de Investigación Sanitaria, Hospital Universitario de La PrincesaMadrid, Spain; Departamento de Farmacología y Terapéutica, Instituto Teófilo Hernando, Universidad Autónoma de MadridMadrid, Spain
| | - Pilar Negredo
- Departamento de Anatomía, Histología y Neurociencia, Universidad Autónoma de Madrid Madrid, Spain
| | - Carlos Avendaño
- Departamento de Anatomía, Histología y Neurociencia, Universidad Autónoma de Madrid Madrid, Spain
| |
Collapse
|
4
|
Modjeski KL, Ture SK, Field DJ, Cameron SJ, Morrell CN. Glutamate Receptor Interacting Protein 1 Mediates Platelet Adhesion and Thrombus Formation. PLoS One 2016; 11:e0160638. [PMID: 27631377 PMCID: PMC5025166 DOI: 10.1371/journal.pone.0160638] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Accepted: 07/23/2016] [Indexed: 01/08/2023] Open
Abstract
Thrombosis-associated pathologies, such as myocardial infarction and stroke, are major causes of morbidity and mortality worldwide. Because platelets are necessary for hemostasis and thrombosis, platelet directed therapies must balance inhibiting platelet function with bleeding risk. Glutamate receptor interacting protein 1 (GRIP1) is a large scaffolding protein that localizes and organizes interacting proteins in other cells, such as neurons. We have investigated the role of GRIP1 in platelet function to determine its role as a molecular scaffold in thrombus formation. Platelet-specific GRIP1-/- mice were used to determine the role of GRIP1 in platelets. GRIP1-/- mice had normal platelet counts, but a prolonged bleeding time and delayed thrombus formation in a FeCl3-induced vessel injury model. In vitro stimulation of WT and GRIP1-/- platelets with multiple agonists showed no difference in platelet activation. However, in vivo platelet rolling velocity after endothelial stimulation was significantly greater in GRIP1-/- platelets compared to WT platelets, indicating a potential platelet adhesion defect. Mass spectrometry analysis of GRIP1 platelet immunoprecipitation revealed enrichment of GRIP1 binding to GPIb-IX complex proteins. Western blots confirmed the mass spectrometry findings that GRIP1 interacts with GPIbα, GPIbβ, and 14-3-3. Additionally, in resting GRIP1-/- platelets, GPIbα and 14-3-3 have increased interaction compared to WT platelets. GRIP1 interactions with the GPIb-IX binding complex are necessary for normal platelet adhesion to a stimulated endothelium.
Collapse
Affiliation(s)
- Kristina L. Modjeski
- Aab Cardiovascular Research Institute, University of Rochester Medical Center, Rochester, NY, United States of America
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, NY, United States of America
| | - Sara K. Ture
- Aab Cardiovascular Research Institute, University of Rochester Medical Center, Rochester, NY, United States of America
| | - David J. Field
- Aab Cardiovascular Research Institute, University of Rochester Medical Center, Rochester, NY, United States of America
| | - Scott J. Cameron
- Aab Cardiovascular Research Institute, University of Rochester Medical Center, Rochester, NY, United States of America
| | - Craig N. Morrell
- Aab Cardiovascular Research Institute, University of Rochester Medical Center, Rochester, NY, United States of America
- * E-mail:
| |
Collapse
|
5
|
Jin H, Chiou TT, Serwanski DR, Miralles CP, Pinal N, De Blas AL. Ring finger protein 34 (RNF34) interacts with and promotes γ-aminobutyric acid type-A receptor degradation via ubiquitination of the γ2 subunit. J Biol Chem 2014; 289:29420-36. [PMID: 25193658 DOI: 10.1074/jbc.m114.603068] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
We have found that the large intracellular loop of the γ2 GABAA receptor (R) subunit (γ2IL) interacts with RNF34 (an E3 ubiquitin ligase), as shown by yeast two-hybrid and in vitro pulldown assays. In brain extracts, RNF34 co-immunoprecipitates with assembled GABAARs. In co-transfected HEK293 cells, RNF34 reduces the expression of the γ2 GABAAR subunit by increasing the ratio of ubiquitinated/nonubiquitinated γ2. Mutating several lysines of the γ2IL into arginines makes the γ2 subunit resistant to RNF34-induced degradation. RNF34 also reduces the expression of the γ2 subunit when α1 and β3 subunits are co-assembled with γ2. This effect is partially reversed by leupeptin or MG132, indicating that both the lysosomal and proteasomal degradation pathways are involved. Immunofluorescence of cultured hippocampal neurons shows that RNF34 forms clusters and that a subset of these clusters is associated with GABAergic synapses. This association is also observed in the intact rat brain by electron microscopy immunocytochemistry. RNF34 is not expressed until the 2nd postnatal week of rat brain development, being highly expressed in some interneurons. Overexpression of RNF34 in hippocampal neurons decreases the density of γ2 GABAAR clusters and the number of GABAergic contacts that these neurons receive. Knocking down endogenous RNF34 with shRNA leads to increased γ2 GABAAR cluster density and GABAergic innervation. The results indicate that RNF34 regulates postsynaptic γ2-GABAAR clustering and GABAergic synaptic innervation by interacting with and ubiquitinating the γ2-GABAAR subunit promoting GABAAR degradation.
Collapse
Affiliation(s)
- Hongbing Jin
- From the Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut 06269
| | - Tzu-Ting Chiou
- From the Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut 06269
| | - David R Serwanski
- From the Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut 06269
| | - Celia P Miralles
- From the Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut 06269
| | - Noelia Pinal
- From the Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut 06269
| | - Angel L De Blas
- From the Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut 06269
| |
Collapse
|
6
|
Romand S, Wang Y, Toledo-Rodriguez M, Markram H. Morphological development of thick-tufted layer v pyramidal cells in the rat somatosensory cortex. Front Neuroanat 2011; 5:5. [PMID: 21369363 PMCID: PMC3043270 DOI: 10.3389/fnana.2011.00005] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2010] [Accepted: 01/19/2011] [Indexed: 11/13/2022] Open
Abstract
The thick-tufted layer V pyramidal (TTL5) neuron is a key neuron providing output from the neocortex. Although it has been extensively studied, principles governing its dendritic and axonal arborization during development are still not fully quantified. Using 3-D model neurons reconstructed from biocytin-labeled cells in the rat somatosensory cortex, this study provides a detailed morphological analysis of TTL5 cells at postnatal day (P) 7, 14, 21, 36, and 60. Three developmental periods were revealed, which were characterized by distinct growing rates and properties of alterations in different compartments. From P7 to P14, almost all compartments grew fast, and filopodia-like segments along apical dendrite disappeared; From P14 to P21, the growth was localized on specified segments of each compartment, and the densities of spines and boutons were significantly increased; From P21 to P60, the number of basal dendritic segments was significantly increased at specified branch orders, and some basal and oblique dendritic segments were lengthened or thickened. Development changes were therefore seen in two modes: the fast overall growth during the first period and the slow localized growth (thickening mainly on intermediates or lengthening mainly on terminals) at the subsequent stages. The lengthening may be accompanied by the retraction on different segments. These results reveal a differential regulation in the arborization of neuronal compartments during development, supporting the notion of functional compartmental development. This quantification provides new insight into the potential value of the TTL5 morphology for information processing, and for other purposes as well.
Collapse
Affiliation(s)
- Sandrine Romand
- Blue Brain Project, École Polytechnique Fédérale de LausanneLausanne, Switzerland
| | - Yun Wang
- School of Optometry and Ophthalmology, Wenzhou Medical CollegeWenzhou, Zhejiang, People's Republic of China
- Neurology Research, Caritas St. Elizabeth's Medical Center, Tufts UniversityBoston, MA, USA
| | | | - Henry Markram
- Blue Brain Project, École Polytechnique Fédérale de LausanneLausanne, Switzerland
| |
Collapse
|
7
|
Laezza F, Dingledine R. Induction and expression rules of synaptic plasticity in hippocampal interneurons. Neuropharmacology 2010; 60:720-9. [PMID: 21195098 DOI: 10.1016/j.neuropharm.2010.12.016] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Revised: 11/30/2010] [Accepted: 12/15/2010] [Indexed: 12/13/2022]
Abstract
The knowledge that excitatory synapses on aspiny hippocampal interneurons can develop genuine forms of activity-dependent remodeling, independently from the surrounding network of principal cells, is a relatively new concept. Cumulative evidence has now unequivocally demonstrated that, despite the absence of specialized postsynaptic spines that serve as compartmentalized structure for intracellular signaling in principal cell plasticity, excitatory inputs onto interneurons can undergo forms of synaptic plasticity that are induced and expressed autonomously from principal cells. Yet, the rules for induction and expression of interneuron plasticity are much more heterogeneous than in principal neurons. Long-term plasticity in interneurons is not necessarily dependent upon postsynaptic activation of NMDA receptors nor relies on the same postsynaptic membrane potential requirements as principal cells. Plasticity in interneurons rather requires activation of Ca(2+)-permeable AMPA receptors and/or metabotropic glutamate receptors and is triggered by postsynaptic hyperpolarization. In this review we will outline these distinct features of interneuron plasticity and identify potential critical candidate molecules that might be important for sustaining long-lasting changes in synaptic strength at excitatory inputs onto interneurons. This article is part of a Special Issue entitled 'Synaptic Plasticity & Interneurons'.
Collapse
Affiliation(s)
- Fernanda Laezza
- University Texas Medical Branch, Department of Pharmacology & Toxicology, 301 University Boulevard, Galveston, TX 77555, USA.
| | | |
Collapse
|
8
|
Yu W, Charych EI, Serwanski DR, Li RW, Ali R, Bahr BA, De Blas AL. Gephyrin interacts with the glutamate receptor interacting protein 1 isoforms at GABAergic synapses. J Neurochem 2010; 105:2300-14. [PMID: 18315564 DOI: 10.1111/j.1471-4159.2008.05311.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
We have previously shown that the glutamate receptor interacting protein 1 (GRIP1) splice forms GRIP1a/b and GRIP1c4-7 are present at the GABAergic post-synaptic complex. Nevertheless, the role that these GRIP1 protein isoforms play at the GABAergic post-synaptic complex is not known. We are now showing that GRIP1c4-7 and GRIP1a/b interact with gephyrin, the main post-synaptic scaffold protein of GABAergic and glycinergic synapses. Gephyrin coprecipitates with GRIP1c4-7 or GRIP1a/b from rat brain extracts and from extracts of human embryonic kidney 293 cells that have been cotransfected with gephyrin and one of the GRIP1 protein isoforms. Moreover, purified gephyrin binds to purified GRIP1c4-7 or GRIP1a/b, indicating that gephyrin directly interacts with the common region of these GRIP1 proteins, which includes PDZ domains 4-7. An engineered deletion construct of GRIP1a/b (GRIP1a4-7), which both contains the aforementioned common region and binds to gephyrin, targets to the post-synaptic GABAergic complex of transfected cultured hippocampal neurons. In these hippocampal cultures, endogenous gephyrin colocalizes with endogenous GRIP1c4-7 and GRIP1a/b in over 90% of the GABAergic synapses. Double-labeling electron microscopy immunogold reveals that in the rat brain GRIP1c4-7 and GRIP1a/b colocalize with gephyrin at the post-synaptic complex of individual synapses. These results indicate that GRIP1c4-7 and GRIP1a/b colocalize and interact with gephyrin at the GABAergic post-synaptic complex and suggest that this interaction plays a role in GABAergic synaptic function.
Collapse
Affiliation(s)
- Wendou Yu
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut 06269-3156, USA
| | | | | | | | | | | | | |
Collapse
|
9
|
Mohrlüder J, Schwarten M, Willbold D. Structure and potential function of gamma-aminobutyrate type A receptor-associated protein. FEBS J 2009; 276:4989-5005. [PMID: 19674112 DOI: 10.1111/j.1742-4658.2009.07207.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The gamma-aminobutyrate type A receptor-associated protein (GABARAP) is a ubiquitin-like modifier, and is implicated in a variety of membrane trafficking and fusion events that are crucial to synaptic plasticity, autophagy and apoptosis. However, important aspects of GABARAP function and regulation remain poorly understood. We review the current state of knowledge about GABARAP, highlighting newly-identified GABARAP ligands, and discuss the possible physiological relevance of each ligand interaction.
Collapse
Affiliation(s)
- Jeannine Mohrlüder
- Institut für Strukturbiologie und Biophysik (ISB-3), Forschungszentrum Jülich, Germany.
| | | | | |
Collapse
|
10
|
Wu Z, Jia X, de la Cruz L, Su XC, Marzolf B, Troisch P, Zak D, Hamilton A, Whittle B, Yu D, Sheahan D, Bertram E, Aderem A, Otting G, Goodnow CC, Hoyne GF. Memory T cell RNA rearrangement programmed by heterogeneous nuclear ribonucleoprotein hnRNPLL. Immunity 2009; 29:863-75. [PMID: 19100700 DOI: 10.1016/j.immuni.2008.11.004] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2008] [Revised: 09/16/2008] [Accepted: 11/04/2008] [Indexed: 11/26/2022]
Abstract
Differentiation of memory cells involves DNA-sequence changes in B lymphocytes but is less clearly defined in T cells. RNA rearrangement is identified here as a key event in memory T cell differentiation by analysis of a mouse mutation that altered the proportions of naive and memory T cells and crippled the process of Ptprc exon silencing needed to generate CD45RO in memory T cells. A single substitution in a memory-induced RNA-binding protein, hnRNPLL, destabilized an RNA-recognition domain that bound with micromolar affinity to RNA containing the Ptprc exon-silencing sequence. Hnrpll mutation selectively diminished T cell accumulation in peripheral lymphoid tissues but not proliferation. Exon-array analysis of Hnrpll mutant naive and memory T cells revealed an extensive program of alternative mRNA splicing in memory T cells, coordinated by hnRNPLL. A remarkable overlap with alternative splicing in neural tissues may reflect a co-opted strategy for diversifying memory T cells.
Collapse
Affiliation(s)
- Zuopeng Wu
- John Curtin School of Medical Research, Australian Phenomics Facility, Australian National University, Canberra ACT 0200, Australia
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
11
|
Yu W, De Blas AL. Gephyrin expression and clustering affects the size of glutamatergic synaptic contacts. J Neurochem 2008; 104:830-45. [PMID: 18199120 DOI: 10.1111/j.1471-4159.2007.05014.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
We have recently shown that disrupting the expression and post-synaptic clustering of gephyrin in cultured hippocampal pyramidal cells, by either gephyrin RNAi (RNA interference) or over-expression of a dominant negative gephyrin-enhanced green fluorescent protein (EGFP) fusion protein, leads to decreased number of post-synaptic gephyrin and GABA(A) receptor clusters and to reduced GABAergic innervation of these cells. On the other hand, increasing gephyrin expression led to a small increase in the number of gephyrin and GABA(A) receptor clusters and to little or no effect on GABAergic innervation. We are now reporting that altering gephyrin expression and clustering affects the size but not the density of glutamatergic synaptic contacts. Knocking down gephyrin with gephyrin RNAi, or preventing gephyrin clustering by over-expression of the dominant negative gephyrin-enhanced green fluorescent protein fusion protein, leads to larger post-synaptic PSD-95 clusters and larger pre-synaptic glutamatergic terminals. On the other hand, over-expression of gephyrin leads to slightly smaller PSD-95 clusters and pre-synaptic glutamatergic terminals. The change in size of PSD-95 clusters were accompanied by a parallel change in the size of NR2-NMDA receptor clusters. It is concluded that the levels of expression and clustering of gephyrin, a protein that concentrates at the post-synaptic complex of the inhibitory synapses, not only has homotypic effects on GABAergic synaptic contacts, but also has heterotypic effects on glutamatergic synaptic contacts. We are proposing that gephyrin is a counterpart of the post-synaptic glutamatergic scaffold protein PSD-95 in regulating the number and/or size of the excitatory and inhibitory synaptic contacts.
Collapse
Affiliation(s)
- Wendou Yu
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut 06269, USA
| | | |
Collapse
|
12
|
Yu W, Jiang M, Miralles CP, Li RW, Chen G, de Blas AL. Gephyrin clustering is required for the stability of GABAergic synapses. Mol Cell Neurosci 2007; 36:484-500. [PMID: 17916433 DOI: 10.1016/j.mcn.2007.08.008] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2007] [Revised: 08/10/2007] [Accepted: 08/16/2007] [Indexed: 12/30/2022] Open
Abstract
Although gephyrin is an important postsynaptic scaffolding protein at GABAergic synapses, the role of gephyrin for GABAergic synapse formation and/or maintenance is still under debate. We report here that knocking down gephyrin expression with small hairpin RNAs (shRNAs) in cultured hippocampal pyramidal cells decreased both the number of gephyrin and GABA(A) receptor clusters. Similar results were obtained by disrupting the clustering of endogenous gephyrin by overexpressing a gephyrin-EGFP fusion protein that formed aggregates with the endogenous gephyrin. Disrupting postsynaptic gephyrin clusters also had transsynaptic effects leading to a significant reduction of GABAergic presynaptic boutons contacting the transfected pyramidal cells. Consistent with the morphological decrease of GABAergic synapses, electrophysiological analysis revealed a significant reduction in both the amplitude and frequency of the spontaneous inhibitory postsynaptic currents (sIPSCs). However, no change in the whole-cell GABA currents was detected, suggesting a selective effect of gephyrin on GABA(A) receptor clustering at postsynaptic sites. It is concluded that gephyrin plays a critical role for the stability of GABAergic synapses.
Collapse
Affiliation(s)
- Wendou Yu
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, CT 06269, USA
| | | | | | | | | | | |
Collapse
|