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Filamin A organizes γ‑aminobutyric acid type B receptors at the plasma membrane. Nat Commun 2023; 14:34. [PMID: 36596803 PMCID: PMC9810740 DOI: 10.1038/s41467-022-35708-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Accepted: 11/21/2022] [Indexed: 01/05/2023] Open
Abstract
The γ-aminobutyric acid type B (GABAB) receptor is a prototypical family C G protein-coupled receptor (GPCR) that plays a key role in the regulation of synaptic transmission. Although growing evidence suggests that GPCR signaling in neurons might be highly organized in time and space, limited information is available about the mechanisms controlling the nanoscale organization of GABAB receptors and other GPCRs on the neuronal plasma membrane. Using a combination of biochemical assays in vitro, single-particle tracking, and super-resolution microscopy, we provide evidence that the spatial organization and diffusion of GABAB receptors on the plasma membrane are governed by dynamic interactions with filamin A, which tethers the receptors to sub-cortical actin filaments. We further show that GABAB receptors are located together with filamin A in small nanodomains in hippocampal neurons. These interactions are mediated by the first intracellular loop of the GABAB1 subunit and modulate the kinetics of Gαi protein activation in response to GABA stimulation.
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Beopoulos A, Géa M, Fasano A, Iris F. RNA epitranscriptomics dysregulation: A major determinant for significantly increased risk of ASD pathogenesis. Front Neurosci 2023; 17:1101422. [PMID: 36875672 PMCID: PMC9978375 DOI: 10.3389/fnins.2023.1101422] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Accepted: 01/31/2023] [Indexed: 02/18/2023] Open
Abstract
Autism spectrum disorders (ASDs) are perhaps the most severe, intractable and challenging child psychiatric disorders. They are complex, pervasive and highly heterogeneous and depend on multifactorial neurodevelopmental conditions. Although the pathogenesis of autism remains unclear, it revolves around altered neurodevelopmental patterns and their implications for brain function, although these cannot be specifically linked to symptoms. While these affect neuronal migration and connectivity, little is known about the processes that lead to the disruption of specific laminar excitatory and inhibitory cortical circuits, a key feature of ASD. It is evident that ASD has multiple underlying causes and this multigenic condition has been considered to also dependent on epigenetic effects, although the exact nature of the factors that could be involved remains unclear. However, besides the possibility for differential epigenetic markings directly affecting the relative expression levels of individual genes or groups of genes, there are at least three mRNA epitranscriptomic mechanisms, which function cooperatively and could, in association with both genotypes and environmental conditions, alter spatiotemporal proteins expression patterns during brain development, at both quantitative and qualitative levels, in a tissue-specific, and context-dependent manner. As we have already postulated, sudden changes in environmental conditions, such as those conferred by maternal inflammation/immune activation, influence RNA epitranscriptomic mechanisms, with the combination of these processes altering fetal brain development. Herein, we explore the postulate whereby, in ASD pathogenesis, RNA epitranscriptomics might take precedence over epigenetic modifications. RNA epitranscriptomics affects real-time differential expression of receptor and channel proteins isoforms, playing a prominent role in central nervous system (CNS) development and functions, but also RNAi which, in turn, impact the spatiotemporal expression of receptors, channels and regulatory proteins irrespective of isoforms. Slight dysregulations in few early components of brain development, could, depending upon their extent, snowball into a huge variety of pathological cerebral alterations a few years after birth. This may very well explain the enormous genetic, neuropathological and symptomatic heterogeneities that are systematically associated with ASD and psychiatric disorders at large.
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Affiliation(s)
| | - Manuel Géa
- Bio-Modeling Systems, Tour CIT, Paris, France
| | - Alessio Fasano
- Division of Pediatric Gastroenterology and Nutrition, Mucosal Immunology and Biology Research Center, Center for Celiac Research and Treatment, Massachusetts General Hospital for Children, Boston, MA, United States
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Membrane trafficking and positioning of mGluRs at presynaptic and postsynaptic sites of excitatory synapses. Neuropharmacology 2021; 200:108799. [PMID: 34592242 DOI: 10.1016/j.neuropharm.2021.108799] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Revised: 08/31/2021] [Accepted: 09/17/2021] [Indexed: 01/21/2023]
Abstract
The plethora of functions of glutamate in the brain are mediated by the complementary actions of ionotropic and metabotropic glutamate receptors (mGluRs). The ionotropic glutamate receptors carry most of the fast excitatory transmission, while mGluRs modulate transmission on longer timescales by triggering multiple intracellular signaling pathways. As such, mGluRs mediate critical aspects of synaptic transmission and plasticity. Interestingly, at synapses, mGluRs operate at both sides of the cleft, and thus bidirectionally exert the effects of glutamate. At postsynaptic sites, group I mGluRs act to modulate excitability and plasticity. At presynaptic sites, group II and III mGluRs act as auto-receptors, modulating release properties in an activity-dependent manner. Thus, synaptic mGluRs are essential signal integrators that functionally couple presynaptic and postsynaptic mechanisms of transmission and plasticity. Understanding how these receptors reach the membrane and are positioned relative to the presynaptic glutamate release site are therefore important aspects of synapse biology. In this review, we will discuss the currently known mechanisms underlying the trafficking and positioning of mGluRs at and around synapses, and how these mechanisms contribute to synaptic functioning. We will highlight outstanding questions and present an outlook on how recent technological developments will move this exciting research field forward.
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Klotz L, Enz R. MGluR7 is a presynaptic metabotropic glutamate receptor at ribbon synapses of inner hair cells. FASEB J 2021; 35:e21855. [PMID: 34644430 DOI: 10.1096/fj.202100672r] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Revised: 07/15/2021] [Accepted: 07/29/2021] [Indexed: 01/17/2023]
Abstract
Glutamate is the most pivotal excitatory neurotransmitter in the central nervous system. Metabotropic glutamate receptors (mGluRs) dimerize and can couple to inhibitory intracellular signal cascades, thereby protecting glutamatergic neurons from excessive excitation and cell death. MGluR7 is correlated with age-related hearing deficits and noise-induced hearing loss; however its exact localization in the cochlea is unknown. Here, we analyzed the expression and localization of mGluR7a and mGluR7b in mouse cochlear wholemounts in detail, using confocal microscopy and 3D reconstructions. We observed a presynaptic localization of mGluR7a at inner hair cells (IHCs), close to the synaptic ribbon. To detect mGluR7b, newly generated antibodies were characterized and showed co-localization with mGluR7a at IHC ribbon synapses. Compared to the number of synaptic ribbons, the numbers of mGluR7a and mGluR7b puncta were reduced at higher frequencies (48 to 64 kHz) and in older animals (6 and 12 months). Previously, we reported a presynaptic localization of mGluR4 and mGluR8b at this synapse type. This enables the possibility for the formation of homo- and/or heterodimeric receptors composed of mGluR4, mGluR7a, mGluR7b and mGluR8b at IHC ribbon synapses. These receptor complexes might represent new molecular targets suited for pharmacological concepts to protect the cochlea against noxious stimuli and excitotoxicity.
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Affiliation(s)
- Lisa Klotz
- Institute for Biochemistry, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Ralf Enz
- Institute for Biochemistry, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
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5
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Cytohesin-2 mediates group I metabotropic glutamate receptor-dependent mechanical allodynia through the activation of ADP ribosylation factor 6 in the spinal cord. Neurobiol Dis 2021; 159:105466. [PMID: 34390832 DOI: 10.1016/j.nbd.2021.105466] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2021] [Revised: 07/20/2021] [Accepted: 08/02/2021] [Indexed: 01/15/2023] Open
Abstract
Group I metabotropic glutamate receptors (mGluRs), mGluR1 and mGluR5, in the spinal cord are implicated in nociceptive transmission and plasticity through G protein-mediated second messenger cascades leading to the activation of various protein kinases such as extracellular signal-regulated kinase (ERK). In this study, we demonstrated that cytohesin-2, a guanine nucleotide exchange factor for ADP ribosylation factors (Arfs), is abundantly expressed in subsets of excitatory interneurons and projection neurons in the superficial dorsal horn. Cytohesin-2 is enriched in the perisynapse on the postsynaptic membrane of dorsal horn neurons and forms a protein complex with mGluR5 in the spinal cord. Central nervous system-specific cytohesin-2 conditional knockout mice exhibited reduced mechanical allodynia in inflammatory and neuropathic pain models. Pharmacological blockade of cytohesin catalytic activity with SecinH3 similarly reduced mechanical allodynia and inhibited the spinal activation of Arf6, but not Arf1, in both pain models. Furthermore, cytohesin-2 conditional knockout mice exhibited reduced mechanical allodynia and ERK1/2 activation following the pharmacological activation of spinal mGluR1/5 with 3,5-dihydroxylphenylglycine (DHPG). The present study suggests that cytothesin-2 is functionally associated with mGluR5 during the development of mechanical allodynia through the activation of Arf6 in spinal dorsal horn neurons.
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Zhang Z, Li N, Wei X, Chen B, Zhang Y, Zhao Y, Hu X, Hou S. GRM4 inhibits the proliferation, migration, and invasion of human osteosarcoma cells through interaction with CBX4. Biosci Biotechnol Biochem 2020; 84:279-289. [PMID: 31581881 DOI: 10.1080/09168451.2019.1673147] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
ABSTRACT
In recent years, the survey of metabolic glutamate receptor 4 (GRM4) in tumor biology has been gradually concerned. There are currently few studies on GRM4 in osteosarcoma, and the biological function is not clear. Analysis of TCGA database showed that there was no substantial deviation in the expression of GRM4 between osteosarcoma and normal tissues. In the subsequent experiments, there is no significant difference in either mRNA or protein levels among immortalized human osteoblasts and various osteosarcoma cells. With the overexpression of GRM4, cell proliferation, migration and invasion were inhibited obviously. It was further revealed that GRM4 can interact with CBX4 to restrict the nuclear localization of CBX4 and affect the transcriptional activity of HIF-1α. This is the evidence supporting the interaction between GRM4 and CBX4, which could inhibit the malignant behavior of osteosarcoma cells through the GRM4/CBX4/HIF-1α signaling pathway.
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Affiliation(s)
- Zengliang Zhang
- Department of orthopaedics, Fourth Medical Center of PLA General Hospital, Beijing, China
- Chinese PLA Medical School, Beijing, China
| | - Nan Li
- Department of orthopaedics, Fourth Medical Center of PLA General Hospital, Beijing, China
| | - Xing Wei
- Aerospace Center Hospital, Beijing, China
| | - Bingyao Chen
- Department of orthopaedics, Fourth Medical Center of PLA General Hospital, Beijing, China
| | - Yinglong Zhang
- Department of orthopaedics, Fourth Medical Center of PLA General Hospital, Beijing, China
| | - Yantao Zhao
- Department of orthopaedics, Fourth Medical Center of PLA General Hospital, Beijing, China
- Beijing Engineering Research Center of Orthopaedic Implants, Beijing, China
| | - Xiantong Hu
- Department of orthopaedics, Fourth Medical Center of PLA General Hospital, Beijing, China
- Beijing Engineering Research Center of Orthopaedic Implants, Beijing, China
| | - Shuxun Hou
- Department of orthopaedics, Fourth Medical Center of PLA General Hospital, Beijing, China
- Orthopedic Institute of PLA, Beijing, China
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León-Navarro DA, Albasanz JL, Martín M. Functional Cross-Talk between Adenosine and Metabotropic Glutamate Receptors. Curr Neuropharmacol 2019; 17:422-437. [PMID: 29663888 PMCID: PMC6520591 DOI: 10.2174/1570159x16666180416093717] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Revised: 03/19/2018] [Accepted: 04/13/2018] [Indexed: 12/14/2022] Open
Abstract
Abstract: G-protein coupled receptors are transmembrane proteins widely expressed in cells and their transduction pathways are mediated by controlling second messenger levels through different G-protein interactions. Many of these receptors have been described as involved in the physiopathology of neurodegenerative diseases and even considered as potential targets for the design of novel therapeutic strategies. Endogenous and synthetic allosteric and orthosteric selective ligands are able to modulate GPCRs at both gene and protein expression levels and can also modify their physiological function. GPCRs that coexist in the same cells can homo- and heteromerize, therefore, modulating their function. Adenosine receptors are GPCRs which stimulate or inhibit adenylyl cyclase activity through Gi/Gs protein and are involved in the control of neurotransmitter release as glutamate. In turn, metabotropic glutamate receptors are also GPCRs which inhibit adenylyl cyclase or stimulate phospholipase C activities through Gi or Gq proteins, respectively. In recent years, evidence of crosstalk mechanisms be-tween different GPCRs have been described. The aim of the present review was to summarize the described mechanisms of interaction and crosstalking between adenosine and metabotropic glutamate receptors, mainly of group I, in both in vitro and in vivo systems, and their possible use for the design of novel ligands for the treatment of neurodegenerative diseases.
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Affiliation(s)
- David Agustín León-Navarro
- Departamento de Quimica Inorganica, Organica y Bioquimica. CRIB, Universidad de Castilla-La Mancha, Spain.,Facultad de Ciencias y Tecnologías Químicas, Avenida Camilo José Cela, 10, 13071 Ciudad Real, Spain
| | - José Luis Albasanz
- Departamento de Quimica Inorganica, Organica y Bioquimica. CRIB, Universidad de Castilla-La Mancha, Spain.,Facultad de Ciencias y Tecnologías Químicas, Avenida Camilo José Cela, 10, 13071 Ciudad Real, Spain.,Facultad de Medicina de Ciudad Real, Camino Moledores s/n. 13071 Ciudad Real, Spain
| | - Mairena Martín
- Departamento de Quimica Inorganica, Organica y Bioquimica. CRIB, Universidad de Castilla-La Mancha, Spain.,Facultad de Ciencias y Tecnologías Químicas, Avenida Camilo José Cela, 10, 13071 Ciudad Real, Spain.,Facultad de Medicina de Ciudad Real, Camino Moledores s/n. 13071 Ciudad Real, Spain
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8
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Scheefhals N, MacGillavry HD. Functional organization of postsynaptic glutamate receptors. Mol Cell Neurosci 2018; 91:82-94. [PMID: 29777761 PMCID: PMC6276983 DOI: 10.1016/j.mcn.2018.05.002] [Citation(s) in RCA: 90] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Revised: 04/16/2018] [Accepted: 05/07/2018] [Indexed: 01/28/2023] Open
Abstract
Glutamate receptors are the most abundant excitatory neurotransmitter receptors in the brain, responsible for mediating the vast majority of excitatory transmission in neuronal networks. The AMPA- and NMDA-type ionotropic glutamate receptors (iGluRs) are ligand-gated ion channels that mediate the fast synaptic responses, while metabotropic glutamate receptors (mGluRs) are coupled to downstream signaling cascades that act on much slower timescales. These functionally distinct receptor sub-types are co-expressed at individual synapses, allowing for the precise temporal modulation of postsynaptic excitability and plasticity. Intriguingly, these receptors are differentially distributed with respect to the presynaptic release site. While iGluRs are enriched in the core of the synapse directly opposing the release site, mGluRs reside preferentially at the border of the synapse. As such, to understand the differential contribution of these receptors to synaptic transmission, it is important to not only consider their signaling properties, but also the mechanisms that control the spatial segregation of these receptor types within synapses. In this review, we will focus on the mechanisms that control the organization of glutamate receptors at the postsynaptic membrane with respect to the release site, and discuss how this organization could regulate synapse physiology.
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Affiliation(s)
- Nicky Scheefhals
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, The Netherlands
| | - Harold D MacGillavry
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, The Netherlands.
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9
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Tirupula KC, Ithychanda SS, Mohan ML, Naga Prasad SV, Qin J, Karnik SS. G protein-coupled receptors directly bind filamin A with high affinity and promote filamin phosphorylation. Biochemistry 2015; 54:6673-83. [PMID: 26460884 PMCID: PMC4642222 DOI: 10.1021/acs.biochem.5b00975] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Although interaction of a few G protein-coupled receptors (GPCRs) with Filamin A, a key actin cross-linking and biomechanical signal transducer protein, has been observed, a comprehensive structure-function analysis of this interaction is lacking. Through a systematic sequence-based analysis, we found that a conserved filamin binding motif is present in the cytoplasmic domains of >20% of the 824 GPCRs encoded in the human genome. Direct high-affinity interaction of filamin binding motif peptides of select GPCRs with the Ig domain of Filamin A was confirmed by nuclear magnetic resonance spectroscopy and isothermal titration calorimetric experiments. Engagement of the filamin binding motif with the Filamin A Ig domain induced the phosphorylation of filamin by protein kinase A in vitro. In transfected cells, agonist activation as well as constitutive activation of representative GPCRs dramatically elicited recruitment and phosphorylation of cellular Filamin A, a phenomenon long known to be crucial for regulating the structure and dynamics of the cytoskeleton. Our data suggest a molecular mechanism for direct GPCR-cytoskeleton coupling via filamin. Until now, GPCR signaling to the cytoskeleton was predominantly thought to be indirect, through canonical G protein-mediated signaling cascades involving GTPases, adenylyl cyclases, phospholipases, ion channels, and protein kinases. We propose that the GPCR-induced filamin phosphorylation pathway is a conserved, novel biochemical signaling paradigm.
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Affiliation(s)
- Kalyan C Tirupula
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic , Cleveland, Ohio 44195, United States
| | - Sujay S Ithychanda
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic , Cleveland, Ohio 44195, United States
| | - Maradumane L Mohan
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic , Cleveland, Ohio 44195, United States
| | - Sathyamangla V Naga Prasad
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic , Cleveland, Ohio 44195, United States
| | - Jun Qin
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic , Cleveland, Ohio 44195, United States
| | - Sadashiva S Karnik
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic , Cleveland, Ohio 44195, United States
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Jong YJI, Sergin I, Purgert CA, O'Malley KL. Location-dependent signaling of the group 1 metabotropic glutamate receptor mGlu5. Mol Pharmacol 2014; 86:774-85. [PMID: 25326002 DOI: 10.1124/mol.114.094763] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Although G protein-coupled receptors are primarily known for converting extracellular signals into intracellular responses, some receptors, such as the group 1 metabotropic glutamate receptor, mGlu5, are also localized on intracellular membranes where they can mediate both overlapping and unique signaling effects. Thus, besides "ligand bias," whereby a receptor's signaling modality can shift from G protein dependence to independence, canonical mGlu5 receptor signaling can also be influenced by "location bias" (i.e., the particular membrane and/or cell type from which it signals). Because mGlu5 receptors play important roles in both normal development and in disorders such as Fragile X syndrome, autism, epilepsy, addiction, anxiety, schizophrenia, pain, dyskinesias, and melanoma, a large number of drugs are being developed to allosterically target this receptor. Therefore, it is critical to understand how such drugs might be affecting mGlu5 receptor function on different membranes and in different brain regions. Further elucidation of the site(s) of action of these drugs may determine which signal pathways mediate therapeutic efficacy.
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Affiliation(s)
- Yuh-Jiin I Jong
- Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri
| | - Ismail Sergin
- Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri
| | - Carolyn A Purgert
- Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri
| | - Karen L O'Malley
- Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri
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11
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Motawea HKB, Jeyaraj SC, Eid AH, Mitra S, Unger NT, Ahmed AAE, Flavahan NA, Chotani MA. Cyclic AMP-Rap1A signaling mediates cell surface translocation of microvascular smooth muscle α2C-adrenoceptors through the actin-binding protein filamin-2. Am J Physiol Cell Physiol 2013; 305:C829-45. [PMID: 23864608 DOI: 10.1152/ajpcell.00221.2012] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The second messenger cyclic AMP (cAMP) plays a vital role in vascular physiology, including vasodilation of large blood vessels. We recently demonstrated cAMP activation of Epac-Rap1A and RhoA-Rho-associated kinase (ROCK)-F-actin signaling in arteriolar-derived smooth muscle cells increases expression and cell surface translocation of functional α2C-adrenoceptors (α2C-ARs) that mediate vasoconstriction in small blood vessels (arterioles). The Ras-related small GTPAse Rap1A increased expression of α2C-ARs and also increased translocation of perinuclear α2C-ARs to intracellular F-actin and to the plasma membrane. This study examined the mechanism of translocation to better understand the role of these newly discovered mediators of blood flow control, potentially activated in peripheral vascular disorders. We utilized a yeast two-hybrid screen with human microvascular smooth muscle cells (microVSM) cDNA library and the α2C-AR COOH terminus to identify a novel interaction with the actin cross-linker filamin-2. Yeast α-galactosidase assays, site-directed mutagenesis, and coimmunoprecipitation experiments in heterologous human embryonic kidney (HEK) 293 cells and in human microVSM demonstrated that α2C-ARs, but not α2A-AR subtype, interacted with filamin. In Rap1-stimulated human microVSM, α2C-ARs colocalized with filamin on intracellular filaments and at the plasma membrane. Small interfering RNA-mediated knockdown of filamin-2 inhibited Rap1-induced redistribution of α2C-ARs to the cell surface and inhibited receptor function. The studies suggest that cAMP-Rap1-Rho-ROCK signaling facilitates receptor translocation and function via phosphorylation of filamin-2 Ser(2113). Together, these studies extend our previous findings to show that functional rescue of α2C-ARs is mediated through Rap1-filamin signaling. Perturbation of this signaling pathway may lead to alterations in α2C-AR trafficking and physiological function.
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Affiliation(s)
- Hanaa K B Motawea
- Center for Cardiovascular and Pulmonary Research, The Research Institute at Nationwide Children's Hospital, Columbus, Ohio
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Tariq A, Jantsch MF. Transcript diversification in the nervous system: a to I RNA editing in CNS function and disease development. Front Neurosci 2012; 6:99. [PMID: 22787438 PMCID: PMC3391646 DOI: 10.3389/fnins.2012.00099] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2012] [Accepted: 06/14/2012] [Indexed: 12/16/2022] Open
Abstract
RNA editing by adenosine deaminases that act on RNA converts adenosines to inosines in coding and non-coding regions of mRNAs. Inosines are interpreted as guanosines and hence, this type of editing can change codons, alter splice patterns, or influence the fate of an RNA. A to I editing is most abundant in the central nervous system (CNS). Here, targets for this type of nucleotide modification frequently encode receptors and channels. In many cases, the editing-induced amino acid exchanges alter the properties of the receptors and channels. Consistently, changes in editing patterns are frequently found associated with diseases of the CNS. In this review we describe the mechanisms of RNA editing and focus on target mRNAs of editing that are functionally relevant to normal and aberrant CNS activity.
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Affiliation(s)
- Aamira Tariq
- Max F. Perutz Laboratories, Department of Chromosome Biology, University of Vienna Vienna, Austria
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Diversity of metabotropic glutamate receptor-interacting proteins and pathophysiological functions. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 970:63-79. [PMID: 22351051 DOI: 10.1007/978-3-7091-0932-8_3] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
In the mammalian brain, the large majority of excitatory synapses express pre- and postsynaptic glutamate receptors. These are ion channels and G protein-coupled membrane proteins that are organized into functional signaling complexes. Here, we will review the nature and pathophysiological functions of the scaffolding proteins associated to these receptors, focusing on the G protein-coupled subtypes.
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SUMO E3 ligases are expressed in the retina and regulate SUMOylation of the metabotropic glutamate receptor 8b. Biochem J 2011; 435:365-71. [PMID: 21288202 DOI: 10.1042/bj20101854] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The central nervous system regulates neuronal excitability by macromolecular signalling complexes that consist of functionally related proteins, including neurotransmitter receptors, enzymes and scaffolds. The composition of these signal complexes is regulated by post-translational modifications, such as phosphorylation and SUMOylation (SUMO is small ubiquitin-related modifier). In the present study, we searched for proteins interacting with the intracellular C-termini of the metabotropic glutamate receptors mGluR8a and mGluR8b and identified proteins of the SUMOylation and NEDDylation machinery. The SUMO E3 ligases Pias1 [Pias is protein inhibitor of activated STAT (signal transducer and activator of transcription)] and Pias3L interacted strongly with mGluR8b, and were co-localized with the E2-conjugating Ubc9, SUMO1 and mGluR8b in cell bodies present in the ganglion cell layer of the mammalian retina. SUMO1 conjugation of Lys882, present in a bona fide consensus sequence for SUMOylation (VKSE) in the mGluR8b C-terminus, was enhanced by addition of Pias1, consistent with an interaction between both proteins. Mutation of Lys882 to arginine reduced, but did not abolish, mGluR8b SUMOylation. Co-mutating a second lysine residue (Lys903) located in the mGluR8b isoform-specific C-terminus largely prevented SUMO1 conjugation by Ubc9. Modelling studies suggested that Lys903 contacts Ubc9 and thus is part of the non-canonical SUMOylation site VKSG. In summary, the results of the present study show in vivo SUMOylation of the complete mGluR8b and co-localize proteins of the SUMOylation machinery in the retina.
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Maurice P, Guillaume JL, Benleulmi-Chaachoua A, Daulat AM, Kamal M, Jockers R. GPCR-Interacting Proteins, Major Players of GPCR Function. PHARMACOLOGY OF G PROTEIN COUPLED RECEPTORS 2011; 62:349-80. [DOI: 10.1016/b978-0-12-385952-5.00001-4] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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Abstract
Our laboratory embarked on research to discover proteins the interaction of which with the mu opioid receptor (MOPr) is required for its function and regulation. We performed yeast two-hybrid screens, using the carboxy tail of the human MOPr as bait and a human brain library. This yielded a number of proteins that seemed to bind to the MOPr C-tail. The one we chose to study in detail was filamin A (FLNA). Evidence was obtained that there was indeed protein-protein binding between the C-tail of MOPr and FLNA. A human melanoma cell line (M2) lacking the gene for FLNA and a control cell line (A7) which differed from M2 only in having been transfected with the gene for FLNA and expressing the FLNA protein were made available to us. We transfected these cell lines with the gene for MOPr and used them in our studies. The absence of FLNA strongly reduced MOPr downregulation as well as desensitization of adenylyl cyclase inhibition and G protein activation. A recent finding, published here for the first time, is that FLNA is required for the activation by mu opioid agonists of the MAP kinase p38. Deletion studies indicated that the MOPr binding site on FLNA is in the 24th repeat, close to its C-terminal. It was further found that FLNA lacking the N-terminal actin binding domain is as capable as full length FLNA to restore cells to control status, suggesting that actin binding is not required. A surprising finding was that upregulation of MOPr by morphine and some agonist analogs occurs in M2 cells lacking FLNA, whereas normal receptor downregulation takes place in A7 cells.
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Huang Y, Zhou Y, Wong HC, Castiblanco A, Chen Y, Brown EM, Yang JJ. Calmodulin regulates Ca2+-sensing receptor-mediated Ca2+ signaling and its cell surface expression. J Biol Chem 2010; 285:35919-31. [PMID: 20826781 DOI: 10.1074/jbc.m110.147918] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The Ca(2+)-sensing receptor (CaSR) is a member of family C of the GPCRs responsible for sensing extracellular Ca(2+) ([Ca(2+)](o)) levels, maintaining extracellular Ca(2+) homeostasis, and transducing Ca(2+) signaling from the extracellular milieu to the intracellular environment. In the present study, we have demonstrated a Ca(2+)-dependent, stoichiometric interaction between CaM and a CaM-binding domain (CaMBD) located within the C terminus of CaSR (residues 871-898). Our studies suggest a wrapping around 1-14-like mode of interaction that involves global conformational changes in both lobes of CaM with concomitant formation of a helical structure in the CaMBD. More importantly, the Ca(2+)-dependent association between CaM and the C terminus of CaSR is critical for maintaining proper responsiveness of intracellular Ca(2+) responses to changes in extracellular Ca(2+) and regulating cell surface expression of the receptor.
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Affiliation(s)
- Yun Huang
- Department of Chemistry, Center for Drug Design and Advanced Biotechnology, Georgia State University, Atlanta, Georgia 30303, USA
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18
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Abstract
The chemokine (C-C motif) receptor 2B (CCR2B) is one of the two isoforms of the receptor for monocyte chemoattractant protein-1 (CCL2), the major chemoattractant for monocytes, involved in an array of chronic inflammatory diseases. Employing the yeast two-hybrid system, we identified the actin-binding protein filamin A (FLNa) as a protein that associates with the carboxyl-terminal tail of CCR2B. Co-immunoprecipitation experiments and in vitro pull down assays demonstrated that FLNa binds constitutively to CCR2B. The colocalization of endogenous CCR2B and filamin A was detected at the surface and in internalized vesicles of THP-1 cells. In addition, CCR2B and FLNa were colocalized in lamellipodia structures of CCR2B-expressing A7 cells. Expression of the receptor in filamin-deficient M2 cells together with siRNA experiments knocking down FLNa in HEK293 cells, demonstrated that lack of FLNa delays the internalization of the receptor. Furthermore, depletion of FLNa in THP-1 monocytes by RNA interference reduced the migration of cells in response to MCP-1. Therefore, FLNa emerges as an important protein for controlling the internalization and spatial localization of the CCR2B receptor in different dynamic membrane structures.
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19
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Rose M, Dütting E, Enz R. Band 4.1 proteins are expressed in the retina and interact with both isoforms of the metabotropic glutamate receptor type 8. J Neurochem 2010; 105:2375-87. [PMID: 18373558 DOI: 10.1111/j.1471-4159.2008.05331.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The function of the CNS depends on the correct regulation of neurotransmitter receptors by interacting proteins. Here, we screened a retinal cDNA library for proteins interacting with the intracellular C-terminus of the metabotropic glutamate receptor isoform 8a (mGluR8a). The band 4.1B protein binds to the C-termini of mGluR8a and mGluR8b, co-localizes with these glutamate receptors in transfected mammalian cells, facilitates their cell surface expression and inhibits the mGluR8 mediated reduction of intracellular cAMP concentrations. In contrast, no interaction with 4.1B was observed for other mGluRs tested. Amino acids encoded by exons 19 and 20 of 4.1B and a stretch of four basic amino acids present in the mGluR8 C-termini mediate the protein interaction. Besides binding to 4.1B, mGluR8 isoforms interact with 4.1G, 4.1N, and 4.1R. Because band 4.1 transcripts undergo extensive alternative splicing, we analyzed the splicing pattern of interacting regions and detected a 4.1B isoform expressed specifically in the retina. Within this tissue, mGluR8 and 4.1B, 4.1G, 4.1N, and 4.1R show a comparable distribution, being expressed in both synaptic layers and in somata of the ganglion cell layer. In summary, our studies identified band 4.1 proteins as new players for the mGluR8 mediated signal transduction.
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Affiliation(s)
- Melanie Rose
- Institut für Biochemie (Emil-Fischer-Zentrum), Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
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20
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Seebahn A, Rose M, Enz R. RanBPM is expressed in synaptic layers of the mammalian retina and binds to metabotropic glutamate receptors. FEBS Lett 2008; 582:2453-7. [PMID: 18555800 DOI: 10.1016/j.febslet.2008.06.010] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2008] [Revised: 05/30/2008] [Accepted: 06/02/2008] [Indexed: 11/20/2022]
Abstract
In the central nervous system, synaptic signal transduction depends on the regulation of neurotransmitter receptors by interacting proteins. Here, we searched for proteins interacting with two metabotropic glutamate receptor type 8 isoforms (mGlu8a and mGlu8b) and identified RanBPM. RanBPM is expressed in several brain regions, including the retina. There, RanBPM is restricted to the inner plexiform layer where it co-localizes with the mGlu8b isoform and processes of cholinergic amacrine cells expressing mGlu2 receptors. RanBPM interacts with mGlu2 and other group II and group III receptors, except mGlu6. Our data suggest that RanBPM might be associated with mGlu receptors at synaptic sites.
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Affiliation(s)
- Angela Seebahn
- Institut für Biochemie (Emil-Fischer-Zentrum), Friedrich-Alexander-Universität Erlangen-Nürnberg, Fahrstr. 17, 91054 Erlangen, Germany
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21
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Onoprishvili I, Ali S, Andria ML, Shpigel A, Simon EJ. Filamin A mutant lacking actin-binding domain restores mu opioid receptor regulation in melanoma cells. Neurochem Res 2008; 33:2054-61. [PMID: 18404377 DOI: 10.1007/s11064-008-9684-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2008] [Accepted: 03/25/2008] [Indexed: 10/22/2022]
Abstract
We have previously reported that the protein filamin A (FLA) binds to the carboxyl tail of the mu opioid receptor (MOPr). Using human melanoma cells, which do not express filamin A, we showed that receptor down-regulation, functional desensitization and trafficking are deficient in the absence of FLA (Onoprishvili et al. Mol Pharmacol 64:1092-1100, 2003). Since FLA has a binding domain for actin and is a member of the family of actin cytoskeleton proteins, it is usually assumed that FLA functions via the actin cytoskeleton. We decided to test this hypothesis by preparing cDNA coding for mutant FLA lacking the actin binding domain (FLA-ABD) and expressing FLA-ABD in the human melanoma cell line M2 (M2-ABD cell line). We report here that this mutant is capable of restoring almost as well as full length FLA the down-regulation of the human MOPr. It is similarly very effective in restoring functional desensitization of MOPr, as assessed by the decrease in G-protein activation after chronic exposure of M2-ABD cells to the mu agonist DAMGO. We also found that A7 cells, expressing wild type FLA, exhibit rapid activation of the MAP kinases, ERK 1 and 2, by DAMGO, as shown by a rise in the level of phospho-ERK 1 and 2. This is followed by rapid dephosphorylation (inactivation), which reaches basal level between 30 and 60 min after DAMGO treatment. M2 cells show normal activation of ERK 1 and 2 in the presence of DAMGO, but very slow inactivation. The rapid rate of MAPK inactivation is partially restored by FLA-ABD. We conclude that some functions of FLA do not act via the actin cytoskeleton. It is likely that other functions, not studied here, may require functional binding of the MOPr-FLA complex to actin.
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Affiliation(s)
- Irma Onoprishvili
- Department of Psychiatry, New York University School of Medicine, 550 First Avenue, New York, NY 10016, USA
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22
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Cho EY, Cho DI, Park JH, Kurose H, Caron MG, Kim KM. Roles of Protein Kinase C and Actin-Binding Protein 280 in the Regulation of Intracellular Trafficking of Dopamine D3 Receptor. Mol Endocrinol 2007; 21:2242-54. [PMID: 17536008 DOI: 10.1210/me.2007-0202] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
AbstractD3 dopamine receptor (D3R) is expressed mainly in parts of the brain that control the emotional behaviors. It is believed that the improper regulation of D3R is involved in the etiology of schizophrenia. Desensitization of D3R is weakly associated with G protein-coupled receptor kinase (GRK)/β-arrestin-directed internalization. This suggests that there might be an alternative pathway that regulates D3R signaling. This report shows that D3R undergoes robust protein kinase C (PKC)-dependent sequestration that is accompanied by receptor phosphorylation and the desensitization of signaling. PKC-dependent D3R sequestration, which was enhanced by PKC-β or -δ, was dynamin dependent but independent of GRK, β-arrestin, or caveolin 1. Site-directed mutagenesis of all possible phosphorylation sites within the intracellular loops of D3R identified serine residues at positions 229 and 257 as the critical amino acids responsible for phorbol-12-myristate-13-acetate (PMA)-induced D3R phosphorylation, sequestration, and desensitization. In addition, the LxxY endocytosis motif, which is located between residues 252 and 255, was found to play accommodating roles for PMA-induced D3R sequestration. A continuous interaction with the actin-binding protein 280 (filamin A), which was previously known to interact with D3R, is required for PMA-induced D3R sequestration. In conclusion, the PKC-dependent but GRK-/β-arrestin-independent phosphorylation of D3R is the main pathway responsible for the sequestration and desensitization of D3R. Filamin A is essential for both the efficient signaling and sequestration of D3R.
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Affiliation(s)
- Eun-Young Cho
- Department of Pharmacology, College of Pharmacy, Chonnam National University, Kwang-Ju 500-757, Korea
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23
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Onoprishvili I, Simon EJ. Chronic morphine treatment up-regulates mu opioid receptor binding in cells lacking filamin A. Brain Res 2007; 1177:9-18. [PMID: 17897634 PMCID: PMC2175075 DOI: 10.1016/j.brainres.2007.08.020] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2007] [Revised: 05/31/2007] [Accepted: 08/09/2007] [Indexed: 11/19/2022]
Abstract
We investigated the effects of morphine and other agonists on the human mu opioid receptor (MOP) expressed in M2 melanoma cells, lacking the actin cytoskeleton protein filamin A and in A7, a subclone of the M2 melanoma cells, stably transfected with filamin A cDNA. The results of binding experiments showed that after chronic morphine treatment (24 h) of A7 cells, MOP-binding sites were down-regulated to 63% of control, whereas, unexpectedly, in M2 cells, MOP binding was up-regulated to 188% of control naive cells. Similar up-regulation was observed with the agonists methadone and levorphanol. The presence of antagonists (naloxone or CTAP) during chronic morphine treatment inhibited MOP down-regulation in A7 cells. In contrast, morphine-induced up-regulation of MOP in M2 cells was further increased by these antagonists. Chronic morphine desensitized MOP in A7 cells, i.e., it decreased DAMGO-induced stimulation of GTPgammaS binding. In M2 cells DAMGO stimulation of GTPgammaS binding was significantly greater than in A7 cells and was not desensitized by chronic morphine. Pertussis toxin treatment abolished morphine-induced receptor up-regulation in M2 cells, whereas it had no effect on morphine-induced down-regulation in A7 cells. These results indicate that, in the absence of filamin A, chronic treatment with morphine, methadone or levorphanol leads to up-regulation of MOP, to our knowledge, the first instance of opioid receptor up-regulation by agonists in cell culture.
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MESH Headings
- Blotting, Western
- Cell Line
- Cell Line, Tumor
- Contractile Proteins/deficiency
- Contractile Proteins/physiology
- Data Interpretation, Statistical
- Diprenorphine/pharmacology
- Enkephalin, Ala(2)-MePhe(4)-Gly(5)-/pharmacology
- Filamins
- Guanosine 5'-O-(3-Thiotriphosphate)/metabolism
- Humans
- Ligands
- Melanoma/genetics
- Melanoma/pathology
- Microfilament Proteins/deficiency
- Microfilament Proteins/physiology
- Morphine/pharmacology
- Narcotic Antagonists/metabolism
- Narcotic Antagonists/pharmacology
- Narcotics/pharmacology
- Pertussis Toxin/pharmacology
- Radioligand Assay
- Receptors, Opioid, mu/agonists
- Receptors, Opioid, mu/drug effects
- Receptors, Opioid, mu/metabolism
- Tubulin/pharmacology
- Up-Regulation/drug effects
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Affiliation(s)
- Irma Onoprishvili
- Department of Psychiatry, New York University School of Medicine, New York, NY
| | - Eric J. Simon
- Department of Psychiatry, New York University School of Medicine, New York, NY
- Department of Pharmacology, New York University School of Medicine, New York, NY
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24
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Kim EY, Ridgway LD, Dryer SE. Interactions with filamin A stimulate surface expression of large-conductance Ca2+-activated K+ channels in the absence of direct actin binding. Mol Pharmacol 2007; 72:622-30. [PMID: 17586600 DOI: 10.1124/mol.107.038026] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Large-conductance Ca(2+)-activated K(+) (BK(Ca)) channels play an important role in the regulation of cell physiology in a wide variety of excitable and nonexcitable tissues. Filamin A is a conserved and ubiquitous actin-binding protein that forms perpendicular actin cross-links and contributes to changes in cell shape, stiffness, and motility. A variety of membrane proteins bind to filamin A, which regulates their trafficking in and out of the plasma membrane. Filamin A is therefore believed to couple membrane dynamics with those of the underlying cytoskeleton. Filamin A was identified in a yeast two-hybrid screen of a neuronal transcriptome using a subunit of BK(Ca) channels as bait, and the interaction was confirmed by a variety of biochemical assays in native neuronal cells and in human embryonic kidney 293T cells expressing BK(Ca) channels. BK(Ca) channels do not traffic to the plasma membrane in M2 melanoma cells, which lack filamin A, but normal trafficking is seen in A7 cells, which express filamin A, or in M2 cells transiently transfected with filamin A. It is noteworthy that stimulation of plasma membrane expression of BK(Ca) channels also occurs when M2 cells are transfected with filamin A constructs that lack the actin binding domain and that do not bind actin in vivo or in vitro. Filamin A is necessary for normal trafficking of BK(Ca) channels to the plasma membrane, but this effect does not require interactions with actin microfilaments, and it is possible that other actions of the filamin family of scaffolding proteins are independent of effects on actin.
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Affiliation(s)
- Eun Young Kim
- Department of Biology and Biochemistry, University of Houston, Houston, TX 77204-5001, USA
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25
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Scheschonka A, Tang Z, Betz H. Sumoylation in neurons: nuclear and synaptic roles? Trends Neurosci 2007; 30:85-91. [PMID: 17241677 DOI: 10.1016/j.tins.2007.01.003] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2006] [Revised: 12/04/2006] [Accepted: 01/15/2007] [Indexed: 01/09/2023]
Abstract
Sumoylation is a post-translational modification that was originally thought to only target nuclear proteins. Evidence has emerged, however, that the role of sumoylation is much more diverse: three plasma membrane proteins belonging to different protein families (glucose transporters, K(+) channels and metabotropic glutamate receptors) have been shown to be sumoylated. In addition, sumoylation of transcription factors, such as myocyte enhancer factor 2 (MEF2), was found to regulate synapse formation. A major role of sumoylation in other systems is to modify protein-protein interactions, and because protein interactions are particularly elaborate in the nervous system and crucial for synapse formation and function, sumoylation could constitute a major regulatory mechanism in neurons. In this review, we evaluate the available data and discuss possible roles for sumoylation in the regulation of crucial neurobiological processes, such as neuronal development and synaptic transmission.
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Affiliation(s)
- Astrid Scheschonka
- Department of Neurochemistry, Max-Planck Institute for Brain Research, Deutschordenstrasse 46, 60528 Frankfurt am Main, Germany.
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26
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Cabello N, Remelli R, Canela L, Soriguera A, Mallol J, Canela EI, Robbins MJ, Lluis C, Franco R, McIlhinney RAJ, Ciruela F. Actin-binding protein alpha-actinin-1 interacts with the metabotropic glutamate receptor type 5b and modulates the cell surface expression and function of the receptor. J Biol Chem 2007; 282:12143-53. [PMID: 17311919 DOI: 10.1074/jbc.m608880200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Receptors for neurotransmitters require scaffolding proteins for membrane microdomain targeting and for regulating receptor function. Using a yeast two-hybrid screen, alpha-actinin-1, a major F-actin cross-linking protein, was identified as a binding partner for the C-terminal domain of metabotropic glutamate receptor type 5b (mGlu(5b) receptor). Co-expression, co-immunoprecipitation, and pull-down experiments showed a close and specific interaction between mGlu(5b) receptor and alpha-actinin-1 in both transfected HEK-293 cells and rat striatum. The interaction of alpha-actinin-1 with mGlu(5b) receptor modulated the cell surface expression of the receptor. This was dependent on the binding of alpha-actinin-1 to the actin cytoskeleton. In addition, the alpha-actinin-1/mGlu(5b) receptor interaction regulated receptor-mediated activation of the mitogen-activated protein kinase pathway. Together, these findings indicate that there is an alpha-actinin-1-dependent mGlu(5b) receptor association with the actin cytoskeleton modulating receptor cell surface expression and functioning.
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Affiliation(s)
- Nuria Cabello
- Institut d'Investigacions Biomèdiques August Pi i Sunyer and Department of Biochemistry and Molecular Biology, University of Barcelona, Facultat de Biologia, Avda. Diagonal 645, Barcelona 08028, Spain
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27
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Enz R. The trick of the tail: protein-protein interactions of metabotropic glutamate receptors. Bioessays 2007; 29:60-73. [PMID: 17187376 DOI: 10.1002/bies.20518] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
It was initially believed that G-protein-coupled receptors, such as metabotropic glutamate receptors, could simply be described as individual proteins that are associated with intracellular signal cascades via G-proteins. This view is no longer tenable. Today we know that metabotropic glutamate receptors (mGluRs) can dimerize and bind to a variety of proteins in addition to trimeric G-proteins. These newly identified protein interactions led to the discovery of new regulatory mechanisms that are independent of and sometimes synergistic with the classical G-protein-coupled second messenger pathways. Notably, several of these mechanisms connect mGluR-mediated signaling to other receptor classes, thereby creating a network of different receptor types and associated signal cascades. The intracellular C-termini of mGluRs play a key role in the regulation of these networks, and various new protein interactions of these domains were described recently. Because mGluRs are involved in a variety of physiological and pathophysiological processes, some of the proteins interacting with this receptor class have potential as valuable pharmaceutical targets. This review will give a comprehensive overview of proteins interacting with mGluR C-termini, highlight new evolving regulatory mechanisms for glutamatergic signal transduction and discuss possibilities for future drug development.
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Affiliation(s)
- Ralf Enz
- Emil-Fischer-Zentrum, Institut für Biochemie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Fahrstrasse 17, 91054 Erlangen, Germany.
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28
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Marie-Claire C, Courtin C, Robert A, Gidrol X, Roques BP, Noble F. Sensitization to the conditioned rewarding effects of morphine modulates gene expression in rat hippocampus. Neuropharmacology 2006; 52:430-5. [PMID: 17014870 PMCID: PMC1976342 DOI: 10.1016/j.neuropharm.2006.08.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2006] [Revised: 07/21/2006] [Accepted: 08/16/2006] [Indexed: 01/17/2023]
Abstract
Opiates addiction is characterized by its long-term persistence. In order to study the enduring changes in long-term memory in hippocampus, a pivotal region for this process, we used suppression subtractive hybridization to compare hippocampal gene expression in morphine and saline-treated rats. Animals were subjected to an extended place preference paradigm consisting of four conditioning phases. Sensitization to the reinforcing effects of the drug occurred after three conditioning phases. After 25 days of treatment rats were euthanized and the complementary DNA (cDNA) from the hippocampus of morphine-dependent and saline-treated animals were then screened for differentially expressed cDNAs. The selected 177 clones were then subjected to a microarray procedure and 20 clones were found differentially regulated. The pattern of regulated genes suggests impairments in neurotransmitter release and the activation of neuroprotective pathways.
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Affiliation(s)
- Cynthia Marie-Claire
- Neuropsychopharmacologie des addictions. Vulnérabilité et variabilité expérimentale et clinique
CNRS : UMR7157 INSERM : U705 IFR71Université René Descartes - Paris V Université Denis Diderot - Paris VIIFaculté de Pharmacie
4 avenue de l'Observatoire
75006 PARIS,FR
| | - Cindie Courtin
- Neuropsychopharmacologie des addictions. Vulnérabilité et variabilité expérimentale et clinique
CNRS : UMR7157 INSERM : U705 IFR71Université René Descartes - Paris V Université Denis Diderot - Paris VIIFaculté de Pharmacie
4 avenue de l'Observatoire
75006 PARIS,FR
| | - Amelie Robert
- Service de génomique fonctionnelle
CEAGenopole d'Evry
91057 Evry Cedex,FR
| | - Xavier Gidrol
- Service de génomique fonctionnelle
CEAGenopole d'Evry
91057 Evry Cedex,FR
| | - Bernard P. Roques
- Pharmacochimie moléculaire et structurale
CNRS : FRE2463Université René Descartes - Paris V4 Av de l'Observatoire
75270 PARIS CEDEX 06,FR
| | - Florence Noble
- Neuropsychopharmacologie des addictions. Vulnérabilité et variabilité expérimentale et clinique
CNRS : UMR7157 INSERM : U705 IFR71Université René Descartes - Paris V Université Denis Diderot - Paris VIIFaculté de Pharmacie
4 avenue de l'Observatoire
75006 PARIS,FR
- * Correspondence should be adressed to: Florence Noble
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29
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Ferraguti F, Shigemoto R. Metabotropic glutamate receptors. Cell Tissue Res 2006; 326:483-504. [PMID: 16847639 DOI: 10.1007/s00441-006-0266-5] [Citation(s) in RCA: 388] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2006] [Accepted: 05/31/2006] [Indexed: 12/22/2022]
Abstract
Metabotropic glutamate receptors (mGlus) are a family of G-protein-coupled receptors activated by the neurotransmitter glutamate. Molecular cloning has revealed eight different subtypes (mGlu1-8) with distinct molecular and pharmacological properties. Multiplicity in this receptor family is further generated through alternative splicing. mGlus activate a multitude of signalling pathways important for modulating neuronal excitability, synaptic plasticity and feedback regulation of neurotransmitter release. In this review, we summarize anatomical findings (from our work and that of other laboratories) describing their distribution in the central nervous system. Recent evidence regarding the localization of these receptors in peripheral tissues will also be examined. The distinct regional, cellular and subcellular distribution of mGlus in the brain will be discussed in view of their relationship to neurotransmitter release sites and of possible functional implications.
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Affiliation(s)
- Francesco Ferraguti
- Department of Pharmacology, Innsbruck Medical University, Peter Mayr Strasse 1a, A-6020, Innsbruck, Austria
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30
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Popowicz GM, Schleicher M, Noegel AA, Holak TA. Filamins: promiscuous organizers of the cytoskeleton. Trends Biochem Sci 2006; 31:411-9. [PMID: 16781869 DOI: 10.1016/j.tibs.2006.05.006] [Citation(s) in RCA: 226] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 04/28/2006] [Accepted: 05/25/2006] [Indexed: 01/14/2023]
Abstract
Filamins are elongated homodimeric proteins that crosslink F-actin. Each monomer chain of filamin comprises an actin-binding domain, and a rod segment consisting of six (Dictyostelium filamin) up to 24 (human filamin) highly homologous repeats of approximately 96 amino acid residues, which adopt an immunoglobulin-like fold. Two hinges in the rod segment, together with the reversible unfolding of single repeats, might be the structural basis for the intrinsic flexibility of the actin networks generated by filamins. There are numerous filamin-binding proteins that associate, in most cases, along the repeats of the rod repeats. This rather promiscuous behaviour renders filamin a versatile scaffold between the actin network and finely tuned molecular cascades from the membrane to the cytoskeleton.
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31
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Tang Z, El Far O, Betz H, Scheschonka A. Pias1 Interaction and Sumoylation of Metabotropic Glutamate Receptor 8. J Biol Chem 2005; 280:38153-9. [PMID: 16144832 DOI: 10.1074/jbc.m508168200] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Group III presynaptic metabotropic glutamate receptors (mGluRs) play a central role in regulating presynaptic activity through G-protein effects on ion channels and signal transducing enzymes. Like all Class C G-protein-coupled receptors, mGluR8 has an extended intracellular C-terminal domain (CTD) presumed to allow for modulation of downstream signaling. In a yeast two-hybrid screen of an adult rat brain cDNA library with the CTDs of mGluR8a and 8b (mGluR8-C) as baits, we identified sumo1 and four different components of the sumoylation cascade (ube2a, Pias1, Piasgamma, Piasxbeta) as interacting proteins. Binding assays using recombinant GST fusion proteins confirmed that Pias1 interacts not only with mGluR8-C but also with all group III mGluR CTDs. Pias1 binding to mGluR8-C required a region N-terminal to a consensus sumoylation motif and was not affected by arginine substitution of the conserved lysine 882 within this motif. Co-transfection of fluorescently tagged mGluR8a-C, sumo1, and enzymes of the sumoylation cascade into HEK293 cells showed that mGluR8a-C can be sumoylated in vivo. Arginine substitution of lysine 882 within the consensus sumoylation motif, but not other conserved lysines within the CTD, abolished in vivo sumoylation. Our results are consistent with post-translational sumoylation providing a novel mechanism of group III mGluR regulation.
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Affiliation(s)
- Zhongshu Tang
- Department of Neurochemistry, Max-Planck-Institute for Brain Research, 60528 Frankfurt, Germany
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32
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Rajasekaran AK, Anilkumar G, Christiansen JJ. Is prostate-specific membrane antigen a multifunctional protein? Am J Physiol Cell Physiol 2005; 288:C975-81. [PMID: 15840561 DOI: 10.1152/ajpcell.00506.2004] [Citation(s) in RCA: 153] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Prostate-specific membrane antigen (PSMA) is a metallopeptidase expressed predominantly in prostate cancer (PCa) cells. PSMA is considered a biomarker for PCa and is under intense investigation for use as an imaging and therapeutic target. Although the clinical utility of PSMA in the detection and treatment of PCa is evident and is being pursued, very little is known about its basic biological function in PCa cells. The purpose of this review is to highlight the possibility that PSMA might be a multifunctional protein. We suggest that PSMA may function as a receptor internalizing a putative ligand, an enzyme playing a role in nutrient uptake, and a peptidase involved in signal transduction in prostate epithelial cells. Insights into the possible functions of PSMA should improve the diagnostic and therapeutic values of this clinically important molecule.
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Affiliation(s)
- Ayyappan K Rajasekaran
- Dept. of Pathology and Laboratory Medicine, David Geffen School of Medicine, Univ. of California, Los Angeles, 10833 Le Conte Ave., Rm. 13-344, CHS, Los Angeles, CA 90095, USA.
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Cranmer SL, Pikovski I, Mangin P, Thompson PE, Domagala T, Frazzetto M, Salem HH, Jackson SP. Identification of a unique filamin A binding region within the cytoplasmic domain of glycoprotein Ibalpha. Biochem J 2005; 387:849-58. [PMID: 15574123 PMCID: PMC1135017 DOI: 10.1042/bj20041836] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2004] [Accepted: 12/02/2004] [Indexed: 11/17/2022]
Abstract
Binding of the platelet GPIb/V/IX (glycoprotein Ib/V/IX) receptor to von Willebrand factor is critical for platelet adhesion and aggregation under conditions of rapid blood flow. The adhesive function of GPIbalpha is regulated by its anchorage to the membrane skeleton through a specific interaction with filamin A. In the present study, we examined the amino acid residues within the cytoplasmic tail of GPIbalpha, which are critical for association with filamin A, using a series of 25-mer synthetic peptides that mimic the cytoplasmic tail sequences of wild-type and mutant forms of GPIbalpha. Peptide binding studies of purified human filamin A have demonstrated a major role for the conserved hydrophobic stretch L567FLWV571 in mediating this interaction. Progressive alanine substitutions of triple, double and single amino acid residues within the Pro561-Arg572 region suggested an important role for Trp570 and Phe568 in promoting GPIbalpha binding to filamin A. The importance of these two residues in promoting filamin A binding to GPIbalpha in vivo was confirmed from the study of Chinese-hamster ovary cells expressing GPIbalpha Trp570-->Ala and Phe568-->Ala substitutions. Phenotypic analysis of these cell lines in flow-based adhesion studies revealed a critical role for these residues in maintaining receptor anchorage to the membrane skeleton and in maintaining cell adhesion to a von Willebrand factor matrix under high-shear conditions. These studies demonstrate a novel filamin A binding motif in the cytoplasmic tail of GPIbalpha, which is critically dependent on both Trp570 and Phe568.
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Affiliation(s)
- Susan L Cranmer
- Australian Centre for Blood Diseases, Monash University, Alfred Medical Research and Education Precinct, Commercial Road, Prahran, Victoria 3181, Australia.
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Zhang M, Breitwieser GE. High Affinity Interaction with Filamin A Protects against Calcium-sensing Receptor Degradation. J Biol Chem 2005; 280:11140-6. [PMID: 15657061 DOI: 10.1074/jbc.m412242200] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Calcium-sensing receptors (CaR) regulate cell proliferation, differentiation, and apoptosis through the MAPK pathway. MAPK pathway activation requires the cytoskeletal scaffold protein filamin A. Here we examine the interactions of CaR with filamin A in HEK-293 and M2 or A7 melanoma cells to determine how interactions with filamin A facilitate signaling. Filamin A interacts with CaR through two predicted beta-strands from residues 962 to 981; interactions between filamin A and CaR are greatly enhanced by exposure to 5 mM Ca2+. Truncations or deletions (from 972 to 997 or 962 to 981) of the CaR carboxyl terminus eliminate high affinity interactions with filamin A, but CaR-mediated MAPK pathway activation still occurs. CaR-mediated ERK phosphorylation can be localized to a predicted alpha-helix proximal to the membrane, which has been shown to be important for G protein-mediated signaling (residues 868-879). In M2 cells (-filamin A), CaR expression levels are very low; cotransfection of CaR with filamin A increases total cellular CaR and increases plasma membrane localization of CaR, facilitating CaR signaling to the MAPK pathway; similar results were obtained in HEK-293 cells. Interaction with filamin A increases cellular CaR by preventing CaR degradation, thereby facilitating CaR signaling. In addition, filamin A facilitates signaling to the MAPK pathway even by CaR truncations or deletion mutants that cannot engage in high affinity interactions with filamin A, suggesting the targeting of critical signaling proteins to CaR.
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Affiliation(s)
- Mingliang Zhang
- Department of Biology, Syracuse University, Syracuse, New York 13244, USA
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Turvey MR, Fogarty KE, Thorn P. Inositol (1,4,5)-trisphosphate receptor links to filamentous actin are important for generating local Ca2+ signals in pancreatic acinar cells. J Cell Sci 2005; 118:971-80. [PMID: 15713744 DOI: 10.1242/jcs.01693] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We explored a potential structural and functional link between filamentous actin (F-actin) and inositol (1,4,5)-trisphosphate receptors (IP3Rs) in mouse pancreatic acinar cells. Using immunocytochemistry, F-actin and type 2 and 3 IP3Rs (IP3R2 and IP3R3) were identified in a cellular compartment immediately beneath the apical plasma membrane. In an effort to demonstrate that IP3R distribution is dependent on an intact F-actin network in the apical subplasmalemmal region, cells were treated with the actin-depolymerising agent latrunculin B. Immunocytochemistry indicated that latrunculin B treatment reduced F-actin in the basolateral subplasmalemmal compartment, and reduced and fractured F-actin in the apical subplasmalemmal compartment. This latrunculin-B-induced loss of F-actin in the apical region coincided with a reduction in IP3R2 and IP3R3, with the remaining IP3Rs localized with the remaining F-actin. Experiments using western blot analysis showed that IP3R3s are resistant to extraction by detergents, which indicates a potential interaction with the cytoskeleton. Latrunculin B treatment in whole-cell patch-clamped cells inhibited Ca2+-dependent Cl– current spikes evoked by inositol (2,4,5)-trisphosphate; this is due to an inhibition of the underlying local Ca2+ signal. Based on these findings, we suggest that IP3Rs form links with F-actin in the apical domain and that these links are essential for the generation of local Ca2+ spikes.
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Affiliation(s)
- Matthew R Turvey
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 IPD, UK
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Kim KM, Gainetdinov RR, Laporte SA, Caron MG, Barak LS. G protein-coupled receptor kinase regulates dopamine D3 receptor signaling by modulating the stability of a receptor-filamin-beta-arrestin complex. A case of autoreceptor regulation. J Biol Chem 2005; 280:12774-80. [PMID: 15687500 DOI: 10.1074/jbc.m408901200] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In addition to its postsynaptic role, the dopamine D3 receptor (D3R) serves as a presynaptic autoreceptor, where it provides continuous feedback regulation of dopamine release at nerve terminals for processes as diverse as emotional tone and locomotion. D3R signaling ability is supported by an association with filamin (actin-binding protein 280), which localizes the receptor with G proteins in plasma membrane lipid rafts but is not appreciably antagonized in a classical sense by the ligand-mediated activation of G protein-coupled receptor kinases (GRKs) and beta-arrestins. In this study, we investigate GRK-mediated regulation of D3R.filamin complex stability and its effect on D3R.G protein signaling potential. Studies in HEK-293 cells show that in the absence of agonist the D3R immunoprecipitates in a complex containing both filamin A and beta-arrestin2. Moreover, the filamin directly interacts with beta-arrestin2 as assessed by immunoprecipitation and yeast two-hybrid studies. With reductions in basal GRK2/3 activity, an increase in the basal association of filamin A and beta-arrestin2 with D3R is observed. Conversely, increases in the basal GRK2/3 activity result in a reduction in the interaction between the D3R and filamin but a relative increase in the agonist-mediated interaction between beta-arrestin2 and the D3R. Our data suggest that the D3R, filamin A, and beta-arrestin form a signaling complex that is destabilized by agonist- or expression-mediated increases in GRK2/3 activity. These findings provide a novel GRK-based mechanism for regulating D3R signaling potential and provide insight for interpreting D3R autoreceptor behavior.
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Affiliation(s)
- Kyeong-Man Kim
- Department of Pharmacology, College of Pharmacy, Chonnam National University, Kwang-Ju, Korea
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Abstract
G protein-coupled receptors (GPCR) interact not only with heterotrimeric G proteins but also with accessory proteins called GPCR interacting proteins (GIP). These proteins have important functions. They are implicated in GPCR targeting to specific cellular compartments, in their assembling into large functional complexes called "receptosomes," in their trafficking to and from the plasma membrane, and in the fine-tuning of their signaling properties. There are several types of GIPs. Some are transmembrane proteins such as another GPCR (homodimerization and heterodimerization), ionic channels, ionotropic receptors, and single transmembrane proteins. The latter is implicated in the fine-tuning of receptor pharmacology or signaling. Other GIPs are soluble proteins interacting mainly with the "magic" C-terminal tail. Among them, PDZ domain-containing proteins are the most abundant. They generally, but not always, interact with the extreme C-terminal domain of GPCRs. Some GIPs interact with specific sequences of the C-terminal such as the Homer binding sequence (-PPxxFR-), the dopamine receptor interacting protein (DRIP) binding sequence (-FxxxFxxxF-), etc. Finally, only few GIPs have been found thus far to interact with the third intracellular loop of GPCRs. The future will tell us if this situation is only due to technical reasons.
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Affiliation(s)
- Joël Bockaert
- UPR CNRS 2580, CCIPE, 141 Rue de la Cardonille, 34094 Montpellier Cedex 5, France.
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Fagni L, Ango F, Perroy J, Bockaert J. Identification and functional roles of metabotropic glutamate receptor-interacting proteins. Semin Cell Dev Biol 2004; 15:289-98. [PMID: 15125892 DOI: 10.1016/j.semcdb.2003.12.018] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
In the mammalian brain, a majority of excitatory synapses use glutamate as a neurotransmitter. Glutamate activates ligand-gated channels (ionotropic receptors) and G protein-coupled (metabotropic) receptors. During the past decade, a number of intracellular proteins have been described to interact with these receptors. These proteins not only scaffold the glutamate receptors at the pre- and post-synaptic membranes, but also regulate their subcellular targeting and intracellular signaling. Thus, identification of these proteins has been essential for further understanding the functions of glutamate receptors. Here we will focus on those proteins that interact with the subgroup of metabotropic glutamate (mGlu) receptors, and review the methods used for their identification, as well as their functional roles in neurons.
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Affiliation(s)
- Laurent Fagni
- Laboratory of Functional Genomics, CNRS UPR 2580, CCIPE, 141 Rue de la Cardonille, 34094 Montpellier Cedex 05, France.
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Croci C, Sticht H, Brandstätter JH, Enz R. Group I Metabotropic Glutamate Receptors Bind to Protein Phosphatase 1C. J Biol Chem 2003; 278:50682-90. [PMID: 14519764 DOI: 10.1074/jbc.m305764200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The modulation of neurotransmitter receptors by kinases and phosphatases represents a key mechanism in controlling synaptic signal transduction. However, molecular determinants involved in the specific targeting and interactions of these enzymes are largely unknown. Here, we identified both catalytic gamma-isoforms of protein phosphatase 1C (PP1gamma1 and PP1gamma2) as binding partners of the group I metabotropic glutamate receptors type 1a, 5a, and 5b in yeast cells and pull-down assays, using recombinant and native protein preparations. The tissue distribution of interacting proteins was compared, and protein phosphatase 1C was detected in dendrites of retinal bipolar cells expressing the respective interacting glutamate receptors. We mapped interacting domains within binding partners and identified five amino acids in the intracellular C termini of the metabotropic glutamate receptors type 1a, 5a, 5b, and 7b being both necessary and sufficient to bind protein phosphatase 1C. Furthermore, we show a dose-dependent competition of these C termini in binding the enzyme. Based on our data, we investigated the structure of the identified amino acids bound to protein phosphatase 1C by homology-based molecular modeling. In summary, these results provide a molecular description of the interaction between protein phosphatase 1C and metabotropic glutamate receptors and thereby increase our understanding of glutamatergic signal transduction.
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Affiliation(s)
- Cristina Croci
- Emil-Fischer-Zentrum, Institut für Biochemie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Fahrstr. 17, Erlangen 91054, Germany
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Onoprishvili I, Andria ML, Kramer HK, Ancevska-Taneva N, Hiller JM, Simon EJ. Interaction between the mu opioid receptor and filamin A is involved in receptor regulation and trafficking. Mol Pharmacol 2003; 64:1092-100. [PMID: 14573758 DOI: 10.1124/mol.64.5.1092] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The carboxyl tail of the human mu opioid receptor was shown to bind the carboxyl terminal region of human filamin A, a protein known to couple membrane proteins to actin. Results from yeast two-hybrid screening were confirmed by direct protein-protein binding and by coimmunoprecipitation of filamin and mu opioid receptor from cell lysates. To investigate the role of filamin A in opioid receptor function and regulation, we used the melanoma cell line M2, which does not express filamin A, and its subclone A7, transfected with human filamin A cDNA. Both cell lines were stably transfected with cDNA encoding myc-tagged human mu opioid receptor. Fluorescent studies, using confocal microscopy, provided evidence that filamin and mu opioid receptors were extensively colocalized on the membranes of filamin-expressing melanoma cells. The immunostaining of mu opioid receptors indicated that the lack of filamin had no detectable effect on membrane localization of the receptors. Moreover, mu opioid receptors function normally in the absence of filamin A, as evidenced by studies of opioid binding and DAMGO inhibition of forskolin-stimulated adenylyl cyclase. However, agonist-induced receptor down-regulation and functional desensitization were virtually abolished in cells lacking filamin A. The level of internalized mu-opioid receptors, after 30-min exposure to agonist, was greatly reduced, suggesting a role for filamin in mu opioid receptor trafficking. During these studies, we observed that forskolin activation of adenylyl cyclase was greatly reduced in filamin-lacking cells. An even more unexpected finding was the ability of long-term treatment with [d-Ala2,N-Me-Phe4,Gly5-ol]-enkephalin of M2 cells, containing mu opioid receptors, to restore normal forskolin activation. The mechanism of this effect is currently unknown. It is postulated that the observed effects on mu opioid receptor regulation by filamin A and, by implication, of the actin cytoskeleton may be the result of its role in mu opioid receptor trafficking.
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Affiliation(s)
- Irma Onoprishvili
- Department of Psychiatry, New York University School of Medicine, 550 First Ave., New York, NY 10016, USA
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Wang Z, Eldstrom JR, Jantzi J, Moore ED, Fedida D. Increased focal Kv4.2 channel expression at the plasma membrane is the result of actin depolymerization. Am J Physiol Heart Circ Physiol 2003; 286:H749-59. [PMID: 14551056 DOI: 10.1152/ajpheart.00398.2003] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Voltage-dependent potassium channel trafficking and localization are regulated by proteins of the cytoskeleton, but the mechanisms by which these occur are still unclear. Using human embryonic kidney (HEK) cells as a heterologous expression system, we tested the role of the actin cytoskeleton in modulating the function of Kv4.2 channels. Pretreatment (>or=1 h) of HEK cells with 5 microM cytochalasin D to disrupt the actin microfilaments greatly augmented whole cell Kv4.2 currents at potentials positive to -20 mV. However, no changes in the voltage dependence of activation and inactivation of macroscopic currents were observed to account for this increase. Similarly, single channel recordings failed to reveal any significant changes in the single channel conductance, open probability, and kinetics. However, the mean patch current was increased from 0.9 +/- 0.2 pA in control to 6.7 +/- 3.0 pA in the presence of cytochalasin D. Imaging experiments revealed a clear increase in the surface expression of the channels and the appearance of "bright spot" features, suggesting that large numbers of channels were being grouped at specific sites. Our data provide clear evidence that increased numbers and altered distribution of Kv4.2 channels at the cell surface are primarily the result of reorganization of the actin cytoskeleton.
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Affiliation(s)
- Zhuren Wang
- Department of Physiology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3
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42
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Burgueño J, Blake DJ, Benson MA, Tinsley CL, Esapa CT, Canela EI, Penela P, Mallol J, Mayor F, Lluis C, Franco R, Ciruela F. The adenosine A2A receptor interacts with the actin-binding protein alpha-actinin. J Biol Chem 2003; 278:37545-52. [PMID: 12837758 DOI: 10.1074/jbc.m302809200] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Recently, evidence has emerged that heptaspanning membrane or G protein-coupled receptors may be linked to intracellular proteins identified as regulators of receptor anchoring and signaling. Using a yeast two-hybrid screen, we identified alpha-actinin, a major F-actin-cross-linking protein, as a binding partner for the C-terminal domain of the adenosine A2A receptor (A2AR). Colocalization, co-immunoprecipitation, and pull-down experiments showed a close and specific interaction between A2AR and alpha-actinin in transfected HEK-293 cells and also in rat striatal tissue. A2AR activation by agonist induced the internalization of the receptor by a process that involved rapid beta-arrestin translocation from the cytoplasm to the cell surface. In the subsequent receptor traffic from the cell surface, the role of actin organization was shown to be crucial in transiently transfected HEK-293 cells, as actin depolymerization by cytochalasin D prevented its agonist-induced internalization. A2ADeltaCTR, a mutant version of A2AR that lacks the C-terminal domain and does not interact with alpha-actinin, was not able to internalize when activated by agonist. Interestingly, A2ADeltaCTR did not show aggregation or clustering after agonist stimulation, a process readily occurring with the wild-type receptor. These findings suggest an alpha-actinin-dependent association between the actin cytoskeleton and A2AR trafficking.
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Affiliation(s)
- Javier Burgueño
- Department of Biochemistry and Molecular Biology, University of Barcelona, 08028 Barcelona, Spain
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Yamazaki M, Furuike S, Ito T. Mechanical response of single filamin A (ABP-280) molecules and its role in the actin cytoskeleton. J Muscle Res Cell Motil 2003; 23:525-34. [PMID: 12785102 DOI: 10.1023/a:1023418725001] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Filamin A produces isotropic cross-linked three-dimensional orthogonal networks with actin filaments in the cortex and at the leading edge of cells. Filamin A also links the actin cytoskeleton to the plasma membrane via its association with various kinds of membrane proteins. Recent new findings strongly support that filamin A plays important roles in the mechanical stability of plasma membrane and cortex, formation of cell shape, mechanical responses of cells, and cell locomotion. To elucidate the mechanical properties of the actin/filamin A network and the complex of membrane protein-filamin A-actin cytoskeleton, the mechanical properties of single human filamin A (hsFLNa) molecules in aqueous solution were investigated using atomic force microscopy. Ig-fold domains of filamin A can be unfolded by the critical external force (50-220 pN), and this unfolding is reversible, i.e., the refolding of the unfolded chain of the filamin A occurs when the external force is removed. Due to this reversible unfolding of Ig-fold domains, filamin A molecule can be stretched to several times the length of its native state. Based on this new feature of filamin A as the 'large-extensible linker', we describe our hypothesis for the mechanical role of filamin A in the actin cytoskeletons in cells and discuss its biological implications. In this review, function of filamin A in actin cytoskeleton, mechanical properties of single filamin A proteins, and the hypothesis for the mechanical role of filamin A in the actin cytoskeletons are discussed.
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Affiliation(s)
- Masahito Yamazaki
- Graduate School of Science and Engineering, Department of Physics, Faculty of Science, Shizuoka University, Shizuoka 422-8529, Japan.
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Bockaert J, Marin P, Dumuis A, Fagni L. The 'magic tail' of G protein-coupled receptors: an anchorage for functional protein networks. FEBS Lett 2003; 546:65-72. [PMID: 12829238 DOI: 10.1016/s0014-5793(03)00453-8] [Citation(s) in RCA: 174] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
All cell types express a great variety of G protein-coupled receptors (GPCRs) that are coupled to only a limited set of G proteins. This disposition favors cross-talk between transduction pathways. However, GPCRs are organized into functional units. They promote specificity and thus avoid unsuitable cross-talk. New methodologies (mostly yeast two-hybrid screens and proteomics) have been used to discover more than 50 GPCR-associated proteins that are involved in building these units. In addition, these protein networks participate in the trafficking, targeting, signaling, fine-tuning and allosteric regulation of GPCRs. To date, proteins that interact with the GPCR C-terminus are the most abundant and are the focus of this review.
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Affiliation(s)
- Joël Bockaert
- Laboratoire de Génomique Fonctionnelle, UPR CNRS 2580, 141 rue de la Cardonille, 34094 Montpellier Cedex 5, France.
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Pin JP, Galvez T, Prézeau L. Evolution, structure, and activation mechanism of family 3/C G-protein-coupled receptors. Pharmacol Ther 2003; 98:325-54. [PMID: 12782243 DOI: 10.1016/s0163-7258(03)00038-x] [Citation(s) in RCA: 452] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
G-protein-coupled receptors (GPCRs) represent one of the largest gene families in the animal genome. These receptors can be classified into several groups based on the sequence similarity of their common heptahelical domain. The family 3 (or C) GPCRs are receptors for the main neurotransmitters glutamate and gamma-aminobutyric acid, for Ca(2+), for sweet and amino acid taste compounds, and for some pheromone molecules, as well as for odorants in fish. Although none of these family 3 receptors have been found in plants, members have been identified in ancient organisms, such as slime molds (Dictyostelium) and sponges. Like any other GPCRs, family 3 receptors possess a transmembrane heptahelical domain responsible for G-protein activation. However, most of these identified receptors also possess a large extracellular domain that is responsible for ligand recognition, is structurally similar to bacterial periplasmic proteins involved in the transport of small molecules, and is called a Venus Flytrap module. The recent resolution of the structure of this binding domain in one of these receptors, the metabotropic glutamate 1 receptor, together with the recent demonstration that these receptors are dimers, revealed a unique mechanism of activation for these GPCRs. Such data open new possibilities in the development of drugs aimed at modulating these receptors, and raise a number of interesting questions on the activation mechanism of the other GPCRs.
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Affiliation(s)
- Jean-Philippe Pin
- Department of Molecular Pharmacology, CCIPE, 141 rue de la Cardonille, 34094 Montpellier Cedex 5, France.
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46
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Enz R, Croci C. Different binding motifs in metabotropic glutamate receptor type 7b for filamin A, protein phosphatase 1C, protein interacting with protein kinase C (PICK) 1 and syntenin allow the formation of multimeric protein complexes. Biochem J 2003; 372:183-91. [PMID: 12570872 PMCID: PMC1223362 DOI: 10.1042/bj20021750] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2002] [Revised: 02/03/2003] [Accepted: 02/05/2003] [Indexed: 11/17/2022]
Abstract
Metabotropic glutamate receptor (mGluR) type 7-mediated neurotransmission depends critically on its regulation by associated molecules, such as kinases, phosphatases and structural proteins. The splice variants mGluR7a and mGluR7b are defined by different intracellular C-termini, and simultaneous or exclusive binding of interacting proteins to these domains modulates mGluR7-mediated signalling. However, molecular determinants defining binding regions for associated proteins within mGluR7 C-termini are mostly unknown. In the present study, we have mapped the binding domains of four proteins [filamin A, protein phosphatase (PP) 1C, protein interacting with protein kinase C (PICK) 1 and syntenin] interacting with the mGluR7b variant, and show that the alternatively spliced distal part of the mGluR7b C-terminus was sufficient for the interactions. By individual substitution of all mGluR7b isoform-specific amino acids with alanine and construction of a series of deletion constructs, residues important for the interactions were identified and binding regions could be defined. Interestingly, mGluR7b contains an unusual PP1C-binding motif, located at the N-terminus of the binding domains for PICK1 and syntenin. Consistently, binding of PP1C and PICK1 or PP1C and syntenin to mGluR7b was not competitive. Furthermore, PICK1, but not PP1C, interacted physically with syntenin. Our results represent a molecular description of the binding mechanisms of four mGluR7-associated proteins, and indicate the formation of ternary protein complexes composed of mGluR7b, PP1C, PICK1 and syntenin.
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Affiliation(s)
- Ralf Enz
- Emil-Fischer Zentrum, Institut für Biochemie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Fahrstrasse 17, D-91054 Erlangen, Germany.
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47
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El Far O, Betz H. G-protein-coupled receptors for neurotransmitter amino acids: C-terminal tails, crowded signalosomes. Biochem J 2002; 365:329-36. [PMID: 12006104 PMCID: PMC1222699 DOI: 10.1042/bj20020481] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2002] [Accepted: 05/08/2002] [Indexed: 11/17/2022]
Abstract
G-protein-coupled receptors (GPCRs) represent a superfamily of highly diverse integral membrane proteins that transduce external signals to different subcellular compartments, including nuclei, via trimeric G-proteins. By differential activation of diffusible G(alpha) and membrane-bound G(beta)gamma subunits, GPCRs might act on both cytoplasmic/intracellular and plasma-membrane-bound effector systems. The coupling efficiency and the plasma membrane localization of GPCRs are regulated by a variety of interacting proteins. In this review, we discuss recently disclosed protein interactions found with the cytoplasmic C-terminal tail regions of two types of presynaptic neurotransmitter receptors, the group III metabotropic glutamate receptors and the gamma-aminobutyric acid type-B receptors (GABA(B)Rs). Calmodulin binding to mGluR7 and other group III mGluRs may provide a Ca(2+)-dependent switch for unidirectional (G(alpha)) versus bidirectional (G(alpha) and G(beta)gamma) signalling to downstream effector proteins. In addition, clustering of mGluR7 by PICK1 (protein interacting with C-kinase 1), a polyspecific PDZ (PSD-95/Dlg1/ZO-1) domain containing synaptic organizer protein, sheds light on how higher-order receptor complexes with regulatory enzymes (or 'signalosomes') could be formed. The interaction of GABA(B)Rs with the adaptor protein 14-3-3 and the transcription factor ATF4 (activating transcription factor 4) suggests novel regulatory pathways for G-protein signalling, cytoskeletal reorganization and nuclear gene expression: processes that may all contribute to synaptic plasticity.
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Affiliation(s)
- Oussama El Far
- Max-Planck Institute for Brain Research, Deutschordenstrasse 46, 60528 Frankfurt/Main, Germany
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