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Pilch KS, Ramgoolam KH, Dolphin AC. Involvement of Ca V 2.2 channels and α 2 δ-1 in homeostatic synaptic plasticity in cultured hippocampal neurons. J Physiol 2022; 600:5333-5351. [PMID: 36377048 PMCID: PMC10107484 DOI: 10.1113/jp283600] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Accepted: 11/08/2022] [Indexed: 11/16/2022] Open
Abstract
In the mammalian brain, presynaptic CaV 2 channels play a pivotal role in synaptic transmission by mediating fast neurotransmitter exocytosis via influx of Ca2+ into the active zone of presynaptic terminals. However, the distribution and modulation of CaV 2.2 channels at plastic hippocampal synapses remains to be elucidated. Here, we assess CaV 2.2 channels during homeostatic synaptic plasticity, a compensatory form of homeostatic control preventing excessive or insufficient neuronal activity during which extensive active zone remodelling has been described. We show that chronic silencing of neuronal activity in mature hippocampal cultures resulted in elevated presynaptic Ca2+ transients, mediated by increased levels of CaV 2.2 channels at the presynaptic site. This work focused further on the role of α2 δ-1 subunits, important regulators of synaptic transmission and CaV 2.2 channel abundance at the presynaptic membrane. We found that α2 δ-1 overexpression reduces the contribution of CaV 2.2 channels to total Ca2+ flux without altering the amplitude of the Ca2+ transients. Levels of endogenous α2 δ-1 decreased during homeostatic synaptic plasticity, whereas the overexpression of α2 δ-1 prevented homeostatic synaptic plasticity in hippocampal neurons. Together, this study reveals a key role for CaV 2.2 channels and novel roles for α2 δ-1 during synaptic plastic adaptation. KEY POINTS: The roles of CaV 2.2 channels and α2 δ-1 in homeostatic synaptic plasticity in hippocampal neurons in culture were examined. Chronic silencing of neuronal activity resulted in elevated presynaptic Ca2+ transients, mediated by increased levels of CaV 2.2 channels at presynaptic sites. The level of endogenous α2 δ-1 decreased during homeostatic synaptic plasticity, whereas overexpression of α2 δ-1 prevented homeostatic synaptic plasticity in hippocampal neurons. Together, this study reveals a key role for CaV 2.2 channels and novel roles for α2 δ-1 during synaptic plastic adaptation.
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Affiliation(s)
- Kjara S. Pilch
- Department of NeurosciencePhysiology and PharmacologyUniversity College LondonLondonUK
| | - Krishma H. Ramgoolam
- Department of NeurosciencePhysiology and PharmacologyUniversity College LondonLondonUK
| | - Annette C. Dolphin
- Department of NeurosciencePhysiology and PharmacologyUniversity College LondonLondonUK
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2
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Kumari A, Rahaman A, Zeng XA, Farooq MA, Huang Y, Yao R, Ali M, Ishrat R, Ali R. Temporal Cortex Microarray Analysis Revealed Impaired Ribosomal Biogenesis and Hyperactivity of the Glutamatergic System: An Early Signature of Asymptomatic Alzheimer's Disease. Front Neurosci 2022; 16:966877. [PMID: 35958988 PMCID: PMC9359077 DOI: 10.3389/fnins.2022.966877] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2022] [Accepted: 06/23/2022] [Indexed: 11/21/2022] Open
Abstract
Pathogenic aging is regarded as asymptomatic AD when there is no cognitive deficit except for neuropathology consistent with Alzheimer's disease. These individuals are highly susceptible to developing AD. Braak and Braak's theory specific to tau pathology illustrates that the brain's temporal cortex region is an initiation site for early AD progression. So, the hub gene analysis of this region may reveal early altered biological cascades that may be helpful to alleviate AD in an early stage. Meanwhile, cognitive processing also drags its attention because cognitive impairment is the ultimate result of AD. Therefore, this study aimed to explore changes in gene expression of aged control, asymptomatic AD (AsymAD), and symptomatic AD (symAD) in the temporal cortex region. We used microarray data sets to identify differentially expressed genes (DEGs) with the help of the R programming interface. Further, we constructed the protein-protein interaction (PPI) network by performing the STRING plugin in Cytoscape and determined the hub genes via the CytoHubba plugin. Furthermore, we conducted Gene Ontology (GO) enrichment analysis via Bioconductor's cluster profile package. Resultant, the AsymAD transcriptome revealed the early-stage changes of glutamatergic hyperexcitability. Whereas the connectivity of major hub genes in this network indicates a shift from initially reduced rRNA biosynthesis in the AsymAD group to impaired protein synthesis in the symAD group. Both share the phenomenon of breaking tight junctions and others. In conclusion, this study offers new understandings of the early biological vicissitudes that occur in the brain before the manifestation of symAD and gives new promising therapeutic targets for early AD intervention.
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Affiliation(s)
- Ankita Kumari
- School of Food Science and Engineering, South China University of Technology, Guangzhou, China
- Guangdong Key Laboratory of Food Intelligent Manufacturing, Foshan University, Foshan, China
- Overseas Expertise Introduction Centre for Discipline Innovation of Food Nutrition and Human Health (111 Centre), Guangzhou, China
| | - Abdul Rahaman
- School of Food Science and Engineering, South China University of Technology, Guangzhou, China
- Guangdong Key Laboratory of Food Intelligent Manufacturing, Foshan University, Foshan, China
- Overseas Expertise Introduction Centre for Discipline Innovation of Food Nutrition and Human Health (111 Centre), Guangzhou, China
- Abdul Rahaman
| | - Xin-An Zeng
- School of Food Science and Engineering, South China University of Technology, Guangzhou, China
- Guangdong Key Laboratory of Food Intelligent Manufacturing, Foshan University, Foshan, China
- Overseas Expertise Introduction Centre for Discipline Innovation of Food Nutrition and Human Health (111 Centre), Guangzhou, China
- *Correspondence: Xin-An Zeng
| | - Muhammad Adil Farooq
- Institute of Food Science and Technology, Khwaja Fareed University of Engineering and Information Technology, Rahim Yar Khan, Pakistan
| | - Yanyan Huang
- Guangdong Key Laboratory of Food Intelligent Manufacturing, Foshan University, Foshan, China
| | - Runyu Yao
- School of Food Science and Engineering, South China University of Technology, Guangzhou, China
- Overseas Expertise Introduction Centre for Discipline Innovation of Food Nutrition and Human Health (111 Centre), Guangzhou, China
| | - Murtaza Ali
- School of Food Science and Engineering, South China University of Technology, Guangzhou, China
- Guangdong Key Laboratory of Food Intelligent Manufacturing, Foshan University, Foshan, China
- Overseas Expertise Introduction Centre for Discipline Innovation of Food Nutrition and Human Health (111 Centre), Guangzhou, China
| | - Romana Ishrat
- Center for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi, India
- Romana Ishrat
| | - Rafat Ali
- Center for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi, India
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Lu H, Liu L, Han S, Wang B, Qin J, Bu K, Zhang Y, Li Z, Ma L, Tian J, Zhang K, Li T, Cui H, Liu X. Expression of tiRNA and tRF in APP/PS1 transgenic mice and the change of related proteins expression. ANNALS OF TRANSLATIONAL MEDICINE 2021; 9:1457. [PMID: 34734009 PMCID: PMC8506760 DOI: 10.21037/atm-21-4318] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Accepted: 09/09/2021] [Indexed: 12/13/2022]
Abstract
Background Transcriptomics, such as that of non-coding RNA (ncRNA), which include microRNA (miRNA), circular RNA, and the transfer RNA (tRNA)-derived fragments (tiRNA and tRF) in Alzheimer's disease (AD) have attracted much attention recently. The tiRNA and tRFs are produced when the tRNA splits at specific sites. The expression change and related function of tiRNA and tRFs in AD has not been fully investigated. Methods In our study, APP/PS1 transgenic mice (AD mice model) and healthy control mice were used to discover the differentially expressed tiRNA and tRFs with high-throughput sequencing. Among the differentially expressed tiRNA and tRFs, we chose two tRFs (tRF-Thr-CGT-003 and tRF-Leu-CAA-004) and predicted the target messenger RNAs (mRNAs) with miRanda and Target Scan. The target mRNAs of tRF-related function and pathways were analyzed, then we performed quantitative reverse transcription polymerase chain reaction (RT-qPCR) and western blot to validate the related target mRNAs and pathways. Results A total of 27 significantly different tiRNA and tRFs were detected between wild type (WT) and APP/PS1 groups, including 14 up-regulated and 13 down-regulated. Through analyzing the target mRNAs of all differentially expressed tiRNA and tRFs with GO enrichment, we found the target mRNAs could take part in the learning and memory biological process, synapse organization, cognition biological process, synaptic transmission, amyloid-β (Aβ) metabolic process, and so on. We then chose three differentially expressed tRFs for further qPCR validation and passed two tRFs: tRF-Thr-CGT-003 and tRF-Leu-CAA-004, that were found to regulate the calcium regulation-related proteins (the voltage-gated calcium channel γ2 subunit and the RYR1 endoplasmic reticulum calcium released protein) and the retinol metabolism-related proteins (retinoic acid metabolic enzymes CYP2S1, CYP2C68, CYP2S1). Conclusions The APP expression and presenilin mutation in APP/PS1 mice could cause tiRNA and tRFs expression change. Among the differentially expressed tiRNA and tRFs, we found some tRFs took part in the voltage-gated calcium channel γ2 subunit expression and regulation, influencing the neuron calcium homeostasis. Moreover, we also found the tRFs may participate in the regulation of retinol metabolism. Our findings suggest that the dysregulated tiRNA and tRFs may be beneficially exploited as potential diagnostic biomarkers and/or therapeutic targets of AD.
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Affiliation(s)
- Honglin Lu
- Department of Neurology, The Second Hospital of Hebei Medical University, Shijiazhuang, China
| | - Lin Liu
- Department of Neurology, The Second Hospital of Hebei Medical University, Shijiazhuang, China
| | - Shu Han
- Department of Electrocardiogram, The Second Hospital of Hebei Medical University, Shijiazhuang, China
| | - Binbin Wang
- Department of Neurology, The Second Hospital of Hebei Medical University, Shijiazhuang, China
| | - Jin Qin
- Department of Neurology, The Second Hospital of Hebei Medical University, Shijiazhuang, China
| | - Kailin Bu
- Department of Neurology, The Second Hospital of Hebei Medical University, Shijiazhuang, China
| | - Yingzhen Zhang
- Department of Neurology, The Second Hospital of Hebei Medical University, Shijiazhuang, China
| | - Zhongzhong Li
- Department of Neurology, The Second Hospital of Hebei Medical University, Shijiazhuang, China
| | - Lina Ma
- Department of Neurology, The Second Hospital of Hebei Medical University, Shijiazhuang, China
| | - Jing Tian
- Department of Neurology, The Second Hospital of Hebei Medical University, Shijiazhuang, China
| | - Kun Zhang
- Department of Neurology, The Second Hospital of Hebei Medical University, Shijiazhuang, China
| | - Tong Li
- Department of Neurology, The Second Hospital of Hebei Medical University, Shijiazhuang, China
| | - Huixian Cui
- Department of Anatomy, Hebei Medical University, Shijiazhuang, China
| | - Xiaoyun Liu
- Department of Neurology, The Second Hospital of Hebei Medical University, Shijiazhuang, China
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Ferron L, Novazzi CG, Pilch KS, Moreno C, Ramgoolam K, Dolphin AC. FMRP regulates presynaptic localization of neuronal voltage gated calcium channels. Neurobiol Dis 2020; 138:104779. [PMID: 31991246 PMCID: PMC7152798 DOI: 10.1016/j.nbd.2020.104779] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Revised: 01/09/2020] [Accepted: 01/24/2020] [Indexed: 12/31/2022] Open
Abstract
Fragile X syndrome (FXS), the most common form of inherited intellectual disability and autism, results from the loss of fragile X mental retardation protein (FMRP). We have recently identified a direct interaction of FMRP with voltage-gated Ca2+ channels that modulates neurotransmitter release. In the present study we used a combination of optophysiological tools to investigate the impact of FMRP on the targeting of voltage-gated Ca2+ channels to the active zones in neuronal presynaptic terminals. We monitored Ca2+ transients at synaptic boutons of dorsal root ganglion (DRG) neurons using the genetically-encoded Ca2+ indicator GCaMP6f tagged to synaptophysin. We show that knock-down of FMRP induces an increase of the amplitude of the Ca2+ transient in functionally-releasing presynaptic terminals, and that this effect is due to an increase of N-type Ca2+ channel contribution to the total Ca2+ transient. Dynamic regulation of CaV2.2 channel trafficking is key to the function of these channels in neurons. Using a CaV2.2 construct with an α-bungarotoxin binding site tag, we further investigate the impact of FMRP on the trafficking of CaV2.2 channels. We show that forward trafficking of CaV2.2 channels from the endoplasmic reticulum to the plasma membrane is reduced when co-expressed with FMRP. Altogether our data reveal a critical role of FMRP on localization of CaV channels to the presynaptic terminals and how its defect in a context of FXS can profoundly affect synaptic transmission. Loss of FMRP increases presynaptic Ca2+ transients. FMRP is a negative regulator of presynaptic Cav2.2 channel abundance. FMRP reduces the forward trafficking of Cav2.2 channels from ER to plasma membrane. Distal part of FMRP carboxy terminus is key for interaction with Cav2.2 channels.
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Affiliation(s)
- Laurent Ferron
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK.
| | - Cesare G Novazzi
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Kjara S Pilch
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Cristian Moreno
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Krishma Ramgoolam
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Annette C Dolphin
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
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5
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Dahimene S, Page KM, Kadurin I, Ferron L, Ho DY, Powell GT, Pratt WS, Wilson SW, Dolphin AC. The α 2δ-like Protein Cachd1 Increases N-type Calcium Currents and Cell Surface Expression and Competes with α 2δ-1. Cell Rep 2019; 25:1610-1621.e5. [PMID: 30404013 PMCID: PMC6231325 DOI: 10.1016/j.celrep.2018.10.033] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Revised: 08/31/2018] [Accepted: 10/05/2018] [Indexed: 12/28/2022] Open
Abstract
Voltage-gated calcium channel auxiliary α2δ subunits are important for channel trafficking and function. Here, we compare the effects of α2δ-1 and an α2δ-like protein called Cachd1 on neuronal N-type (CaV2.2) channels, which are important in neurotransmission. Previous structural studies show the α2δ-1 VWA domain interacting with the first loop in CaV1.1 domain-I via its metal ion-dependent adhesion site (MIDAS) motif and additional Cache domain interactions. Cachd1 has a disrupted MIDAS motif. However, Cachd1 increases CaV2.2 currents substantially (although less than α2δ-1) and increases CaV2.2 cell surface expression by reducing endocytosis. Although the effects of α2δ-1 are abolished by mutation of Asp122 in CaV2.2 domain-I, which mediates interaction with its VWA domain, the Cachd1 responses are unaffected. Furthermore, Cachd1 co-immunoprecipitates with CaV2.2 and inhibits co-immunoprecipitation of α2δ-1 by CaV2.2. Cachd1 also competes with α2δ-1 for effects on trafficking. Thus, Cachd1 influences both CaV2.2 trafficking and function and can inhibit responses to α2δ-1. Cachd1 enhances CaV2.2 currents and increases CaV2.2 surface expression Effects of Cachd1 are not prevented by mutation in CaV2.2 VWA interaction site The effects of α2δ-1 are prevented by the same mutation in CaV2.2 Cachd1 competes with α2δ-1 for its effects on CaV2.2
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Affiliation(s)
- Shehrazade Dahimene
- Department of Neuroscience, Physiology and Pharmacology, Division of Biosciences, University College London, London WC1E 6BT, UK
| | - Karen M Page
- Department of Neuroscience, Physiology and Pharmacology, Division of Biosciences, University College London, London WC1E 6BT, UK
| | - Ivan Kadurin
- Department of Neuroscience, Physiology and Pharmacology, Division of Biosciences, University College London, London WC1E 6BT, UK
| | - Laurent Ferron
- Department of Neuroscience, Physiology and Pharmacology, Division of Biosciences, University College London, London WC1E 6BT, UK
| | - Dominique Y Ho
- Department of Neuroscience, Physiology and Pharmacology, Division of Biosciences, University College London, London WC1E 6BT, UK
| | - Gareth T Powell
- Department of Cell and Developmental Biology, Division of Biosciences, University College London, London WC1E 6BT, UK
| | - Wendy S Pratt
- Department of Neuroscience, Physiology and Pharmacology, Division of Biosciences, University College London, London WC1E 6BT, UK
| | - Stephen W Wilson
- Department of Cell and Developmental Biology, Division of Biosciences, University College London, London WC1E 6BT, UK
| | - Annette C Dolphin
- Department of Neuroscience, Physiology and Pharmacology, Division of Biosciences, University College London, London WC1E 6BT, UK.
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Andries L, De Groef L, Moons L. Neuroinflammation and Optic Nerve Regeneration: Where Do We Stand in Elucidating Underlying Cellular and Molecular Players? Curr Eye Res 2019; 45:397-409. [PMID: 31567007 DOI: 10.1080/02713683.2019.1669664] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Neurodegenerative diseases and central nervous system (CNS) trauma are highly irreversible, in part because adult mammals lack a robust regenerative capacity. A multifactorial problem underlies the limited axonal regeneration potential. Strikingly, neuroinflammation seems able to induce axonal regrowth in the adult mammalian CNS. It is increasingly clear that both blood-borne and resident inflammatory cells as well as reactivated glial cells affect axonal regeneration. The scope of this review is to give a comprehensive overview of the knowledge that links inflammation (with a focus on the innate immune system) to axonal regeneration and to critically reflect on the controversy that still prevails about the cells, molecules and pathways that are dominating the scene. Also, a brief overview is given of what is already known about the crosstalk between and the heterogeneity of cell types that might play a role in axonal regeneration. Recent research indicates that inflammation-induced axonal regrowth is not solely driven by a single-cell population but probably relies on the crosstalk between multiple cell types and the strong regulation of these cell populations in time and space. Moreover, there is growing evidence that the different cell populations are highly heterogeneous and as such can react differently upon injury. This could explain the controversial results that have been obtained over the past years. The primary focus of this manuscript is the retinofugal system of adult mammals, however, when relevant, insights or examples of the spontaneous regenerating zebrafish model and spinal cord research are added.
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Affiliation(s)
- Lien Andries
- Department of Biology, Neural Circuit Development and Regeneration Research Group, KU Leuven, Leuven, Belgium
| | - Lies De Groef
- Department of Biology, Neural Circuit Development and Regeneration Research Group, KU Leuven, Leuven, Belgium
| | - Lieve Moons
- Department of Biology, Neural Circuit Development and Regeneration Research Group, KU Leuven, Leuven, Belgium
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7
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Gedvilaite G, Vilkeviciute A, Kriauciuniene L, Asmoniene V, Liutkeviciene R. Does CETP rs5882, rs708272, SIRT1 rs12778366, FGFR2 rs2981582, STAT3 rs744166, VEGFA rs833068, IL6 rs1800795 polymorphisms play a role in optic neuritis development? Ophthalmic Genet 2019; 40:219-226. [DOI: 10.1080/13816810.2019.1622022] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Greta Gedvilaite
- Lithuanian University of Health Sciences, Medical Academy, Kaunas, Lithuania
- Neuroscience Institute, Lithuanian University of Health Sciences, Medical Academy, Kaunas, Lithuania
| | - Alvita Vilkeviciute
- Neuroscience Institute, Lithuanian University of Health Sciences, Medical Academy, Kaunas, Lithuania
| | - Loresa Kriauciuniene
- Neuroscience Institute, Lithuanian University of Health Sciences, Medical Academy, Kaunas, Lithuania
- Department of Ophthalmology, Lithuanian University of Health Sciences, Medical Academy, Kaunas, Lithuania
| | - Virginija Asmoniene
- Department of genetics and molecular medicine, Lithuanian University of Health Sciences, Medical Academy, Kaunas, Lithuania
| | - Rasa Liutkeviciene
- Neuroscience Institute, Lithuanian University of Health Sciences, Medical Academy, Kaunas, Lithuania
- Department of Ophthalmology, Lithuanian University of Health Sciences, Medical Academy, Kaunas, Lithuania
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8
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Ansado J, Blunt A, Chen JK, Koski L, Ptito A. Impact of non-invasive brain stimulation on transcallosal modulation in mild traumatic brain injury: a multimodal pilot investigation. Brain Inj 2019; 33:1021-1031. [DOI: 10.1080/02699052.2019.1605620] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Jennyfer Ansado
- Cognitive Neuroscience Unit, Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | - Aaron Blunt
- Cognitive Neuroscience Unit, Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | - Jen-Kai Chen
- Cognitive Neuroscience Unit, Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | - Lisa Koski
- Cognitive Neuroscience Unit, Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | - Alain Ptito
- Cognitive Neuroscience Unit, Montreal Neurological Institute, McGill University, Montreal, QC, Canada
- Department of Psychology, McGill University Health Centre, Montreal, QC, Canada
- Department of Neurology and Neurosurgery, McGill University, Montreal, QC, Canada
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9
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Bissen D, Foss F, Acker-Palmer A. AMPA receptors and their minions: auxiliary proteins in AMPA receptor trafficking. Cell Mol Life Sci 2019; 76:2133-2169. [PMID: 30937469 PMCID: PMC6502786 DOI: 10.1007/s00018-019-03068-7] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Revised: 02/12/2019] [Accepted: 03/07/2019] [Indexed: 12/12/2022]
Abstract
To correctly transfer information, neuronal networks need to continuously adjust their synaptic strength to extrinsic stimuli. This ability, termed synaptic plasticity, is at the heart of their function and is, thus, tightly regulated. In glutamatergic neurons, synaptic strength is controlled by the number and function of AMPA receptors at the postsynapse, which mediate most of the fast excitatory transmission in the central nervous system. Their trafficking to, at, and from the synapse, is, therefore, a key mechanism underlying synaptic plasticity. Intensive research over the last 20 years has revealed the increasing importance of interacting proteins, which accompany AMPA receptors throughout their lifetime and help to refine the temporal and spatial modulation of their trafficking and function. In this review, we discuss the current knowledge about the roles of key partners in regulating AMPA receptor trafficking and focus especially on the movement between the intracellular, extrasynaptic, and synaptic pools. We examine their involvement not only in basal synaptic function, but also in Hebbian and homeostatic plasticity. Included in our review are well-established AMPA receptor interactants such as GRIP1 and PICK1, the classical auxiliary subunits TARP and CNIH, and the newest additions to AMPA receptor native complexes.
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Affiliation(s)
- Diane Bissen
- Institute of Cell Biology and Neuroscience and Buchmann Institute for Molecular Life Sciences (BMLS), University of Frankfurt, Max-von-Laue-Str. 15, 60438, Frankfurt am Main, Germany
- Max Planck Institute for Brain Research, Max von Laue Str. 4, 60438, Frankfurt am Main, Germany
| | - Franziska Foss
- Institute of Cell Biology and Neuroscience and Buchmann Institute for Molecular Life Sciences (BMLS), University of Frankfurt, Max-von-Laue-Str. 15, 60438, Frankfurt am Main, Germany
| | - Amparo Acker-Palmer
- Institute of Cell Biology and Neuroscience and Buchmann Institute for Molecular Life Sciences (BMLS), University of Frankfurt, Max-von-Laue-Str. 15, 60438, Frankfurt am Main, Germany.
- Max Planck Institute for Brain Research, Max von Laue Str. 4, 60438, Frankfurt am Main, Germany.
- Cardio-Pulmonary Institute (CPI), Max-von-Laue-Str. 15, 60438, Frankfurt am Main, Germany.
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Haworth AS, Brackenbury WJ. Emerging roles for multifunctional ion channel auxiliary subunits in cancer. Cell Calcium 2019; 80:125-140. [PMID: 31071485 PMCID: PMC6553682 DOI: 10.1016/j.ceca.2019.04.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Revised: 04/16/2019] [Accepted: 04/16/2019] [Indexed: 02/07/2023]
Abstract
Several superfamilies of plasma membrane channels which regulate transmembrane ion flux have also been shown to regulate a multitude of cellular processes, including proliferation and migration. Ion channels are typically multimeric complexes consisting of conducting subunits and auxiliary, non-conducting subunits. Auxiliary subunits modulate the function of conducting subunits and have putative non-conducting roles, further expanding the repertoire of cellular processes governed by ion channel complexes to processes such as transcellular adhesion and gene transcription. Given this expansive influence of ion channels on cellular behaviour it is perhaps no surprise that aberrant ion channel expression is a common occurrence in cancer. This review will focus on the conducting and non-conducting roles of the auxiliary subunits of various Ca2+, K+, Na+ and Cl- channels and the burgeoning evidence linking such auxiliary subunits to cancer. Several subunits are upregulated (e.g. Cavβ, Cavγ) and downregulated (e.g. Kvβ) in cancer, while other subunits have been functionally implicated as oncogenes (e.g. Navβ1, Cavα2δ1) and tumour suppressor genes (e.g. CLCA2, KCNE2, BKγ1) based on in vivo studies. The strengthening link between ion channel auxiliary subunits and cancer has exposed these subunits as potential biomarkers and therapeutic targets. However further mechanistic understanding is required into how these subunits contribute to tumour progression before their therapeutic potential can be fully realised.
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Affiliation(s)
- Alexander S Haworth
- Department of Biology, University of York, Heslington, York, YO10 5DD, UK; York Biomedical Research Institute, University of York, Heslington, York, YO10 5DD, UK
| | - William J Brackenbury
- Department of Biology, University of York, Heslington, York, YO10 5DD, UK; York Biomedical Research Institute, University of York, Heslington, York, YO10 5DD, UK.
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11
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Sun L, Zhang Y, Liu E, Ma Q, Anatol M, Han H, Yan J. The roles of astrocyte in the brain pathologies following ischemic stroke. Brain Inj 2018; 33:712-716. [PMID: 30335519 DOI: 10.1080/02699052.2018.1531311] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Aim: In this work, we systematically explored the physiological functions of astrocytes and their roles following ischemic stroke, additionally, the potential therapy strategy targeting the astrocytes was also discussed. Methods: This work searched the PubMed database (including MEDLINE) until 14 Feb 2018, and furthermore, the studies were identified through cross-referencing and by consulting the experts in this field. Results: This study indicated that the astrocytes can not only play harmful roles following ischemic stroke through release of inflammatory factors and formation of glial scar but also have protective effects through quenching glutamate excitotoxicity and maintaining the clearance function of glymphatic system in brain. Conclusion: Owing to their important roles in physiological functions of brain and in the pathological conditions following ischemic stroke, the astrocytes might be a potential but promising therapeutic target for treating the ischemic stroke in the future.
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Affiliation(s)
- Linlin Sun
- a Department of Anatomy and Histology, School of Basic Medical Sciences , Peking University , Beijing , China
| | - Yixuan Zhang
- a Department of Anatomy and Histology, School of Basic Medical Sciences , Peking University , Beijing , China
| | - E Liu
- a Department of Anatomy and Histology, School of Basic Medical Sciences , Peking University , Beijing , China
| | - Qingyi Ma
- b Center for Perinatal Biology, School of Medicine , Loma Linda University , Loma Linda , USA
| | - Manaenko Anatol
- c Departments of Neurology , University of Erlangen-Nuremberg , Erlangen , Germany
| | - Hongbin Han
- d Beijing Key Lab of Magnetic Resonance Imaging Technology , Beijing , China
| | - Junhao Yan
- a Department of Anatomy and Histology, School of Basic Medical Sciences , Peking University , Beijing , China.,d Beijing Key Lab of Magnetic Resonance Imaging Technology , Beijing , China
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Santos-Cortez RLP, Khan V, Khan FS, Mughal ZUN, Chakchouk I, Lee K, Rasheed M, Hamza R, Acharya A, Ullah E, Saqib MAN, Abbe I, Ali G, Hassan MJ, Khan S, Azeem Z, Ullah I, Bamshad MJ, Nickerson DA, Schrauwen I, Ahmad W, Ansar M, Leal SM. Novel candidate genes and variants underlying autosomal recessive neurodevelopmental disorders with intellectual disability. Hum Genet 2018; 137:735-752. [PMID: 30167849 PMCID: PMC6201268 DOI: 10.1007/s00439-018-1928-6] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Accepted: 08/10/2018] [Indexed: 01/30/2023]
Abstract
Identification of Mendelian genes for neurodevelopmental disorders using exome sequencing to study autosomal recessive (AR) consanguineous pedigrees has been highly successful. To identify causal variants for syndromic and non-syndromic intellectual disability (ID), exome sequencing was performed using DNA samples from 22 consanguineous Pakistani families with ARID, of which 21 have additional phenotypes including microcephaly. To aid in variant identification, homozygosity mapping and linkage analysis were performed. DNA samples from affected family member(s) from every pedigree underwent exome sequencing. Identified rare damaging exome variants were tested for co-segregation with ID using Sanger sequencing. For seven ARID families, variants were identified in genes not previously associated with ID, including: EI24, FXR1 and TET3 for which knockout mouse models have brain defects; and CACNG7 and TRAPPC10 where cell studies suggest roles in important neural pathways. For two families, the novel ARID genes CARNMT1 and GARNL3 lie within previously reported ID microdeletion regions. We also observed homozygous variants in two ID candidate genes, GRAMD1B and TBRG1, for which each has been previously reported in a single family. An additional 14 families have homozygous variants in established ID genes, of which 11 variants are novel. All ARID genes have increased expression in specific structures of the developing and adult human brain and 91% of the genes are differentially expressed in utero or during early childhood. The identification of novel ARID candidate genes and variants adds to the knowledge base that is required to further understand human brain function and development.
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Affiliation(s)
- Regie Lyn P Santos-Cortez
- Department of Molecular and Human Genetics, Center for Statistical Genetics, Baylor College of Medicine, 1 Baylor Plaza 700D, Houston, TX, 77030, USA
- Department of Otolaryngology, University of Colorado School of Medicine, 12700 E. 19th Ave., Aurora, CO, 80045, USA
| | - Valeed Khan
- Department of Biochemistry, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad, 45320, Pakistan
| | - Falak Sher Khan
- Department of Biochemistry, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad, 45320, Pakistan
| | - Zaib-Un-Nisa Mughal
- Department of Biochemistry, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad, 45320, Pakistan
| | - Imen Chakchouk
- Department of Molecular and Human Genetics, Center for Statistical Genetics, Baylor College of Medicine, 1 Baylor Plaza 700D, Houston, TX, 77030, USA
| | - Kwanghyuk Lee
- Department of Molecular and Human Genetics, Center for Statistical Genetics, Baylor College of Medicine, 1 Baylor Plaza 700D, Houston, TX, 77030, USA
| | - Memoona Rasheed
- Department of Biochemistry, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad, 45320, Pakistan
| | - Rifat Hamza
- Department of Biochemistry, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad, 45320, Pakistan
| | - Anushree Acharya
- Department of Molecular and Human Genetics, Center for Statistical Genetics, Baylor College of Medicine, 1 Baylor Plaza 700D, Houston, TX, 77030, USA
| | - Ehsan Ullah
- Department of Biochemistry, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad, 45320, Pakistan
| | - Muhammad Arif Nadeem Saqib
- Department of Biochemistry, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad, 45320, Pakistan
- Pakistan Health Research Council, Shahrah-e-Jamhuriat, G-5/2, Islamabad, Pakistan
| | - Izoduwa Abbe
- Department of Molecular and Human Genetics, Center for Statistical Genetics, Baylor College of Medicine, 1 Baylor Plaza 700D, Houston, TX, 77030, USA
| | - Ghazanfar Ali
- Department of Biotechnology, University of Azad Jammu and Kashmir, Muzaffarabad, Pakistan
| | - Muhammad Jawad Hassan
- Department of Healthcare Biotechnology, Atta-ur-Rahman School of Applied Biosciences, National University of Sciences and Technology, Islamabad, Pakistan
| | - Saadullah Khan
- Department of Biotechnology and Genetic Engineering, Kohat University of Science and Technology, Kohat, KPK, Pakistan
| | - Zahid Azeem
- Department of Biochemistry, Azad Jammu and Kashmir Medical College, Muzaffarabad, Pakistan
| | - Irfan Ullah
- Department of Biochemistry, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad, 45320, Pakistan
| | - Michael J Bamshad
- Department of Genome Sciences, University of Washington, Foege Building S-250, 3720 15th Ave. NE, Seattle, WA, 98195, USA
- Department of Pediatrics, University of Washington, 1959 NE Pacific St., Seattle, WA, 98195, USA
| | - Deborah A Nickerson
- Department of Genome Sciences, University of Washington, Foege Building S-250, 3720 15th Ave. NE, Seattle, WA, 98195, USA
| | - Isabelle Schrauwen
- Department of Molecular and Human Genetics, Center for Statistical Genetics, Baylor College of Medicine, 1 Baylor Plaza 700D, Houston, TX, 77030, USA
| | - Wasim Ahmad
- Department of Biochemistry, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad, 45320, Pakistan
| | - Muhammad Ansar
- Department of Biochemistry, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad, 45320, Pakistan
| | - Suzanne M Leal
- Department of Molecular and Human Genetics, Center for Statistical Genetics, Baylor College of Medicine, 1 Baylor Plaza 700D, Houston, TX, 77030, USA.
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13
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Mehta A. Storing and retrieving long-term memories: cooperation and competition in synaptic dynamics. ADVANCES IN PHYSICS: X 2018. [DOI: 10.1080/23746149.2018.1480415] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022] Open
Affiliation(s)
- Anita Mehta
- Max Planck Institute for Mathematics in the Sciences, Leipzig, Germany
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14
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HRPU-2, a Homolog of Mammalian hnRNP U, Regulates Synaptic Transmission by Controlling the Expression of SLO-2 Potassium Channel in Caenorhabditis elegans. J Neurosci 2017; 38:1073-1084. [PMID: 29217678 DOI: 10.1523/jneurosci.1991-17.2017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Revised: 11/27/2017] [Accepted: 12/02/2017] [Indexed: 12/22/2022] Open
Abstract
Slo2 channels are large-conductance potassium channels abundantly expressed in the nervous system. However, it is unclear how their expression level in neurons is regulated. Here we report that HRPU-2, an RNA-binding protein homologous to mammalian heterogeneous nuclear ribonucleoprotein U (hnRNP U), plays an important role in regulating the expression of SLO-2 (a homolog of mammalian Slo2) in Caenorhabditis elegans Loss-of-function (lf) mutants of hrpu-2 were isolated in a genetic screen for suppressors of a sluggish phenotype caused by a hyperactive SLO-2. In hrpu-2(lf) mutants, SLO-2-mediated delayed outward currents in neurons are greatly decreased, and neuromuscular synaptic transmission is enhanced. These mutant phenotypes can be rescued by expressing wild-type HRPU-2 in neurons. HRPU-2 binds to slo-2 mRNA, and hrpu-2(lf) mutants show decreased SLO-2 protein expression. In contrast, hrpu-2(lf) does not alter the expression of either the BK channel SLO-1 or the Shaker type potassium channel SHK-1. hrpu-2(lf) mutants are indistinguishable from wild type in gross motor neuron morphology and locomotion behavior. Together, these observations suggest that HRPU-2 plays important roles in SLO-2 function by regulating SLO-2 protein expression, and that SLO-2 is likely among a restricted set of proteins regulated by HRPU-2. Mutations of human Slo2 channel and hnRNP U are strongly linked to epileptic disorders and intellectual disability. The findings of this study suggest a potential link between these two molecules in human patients.SIGNIFICANCE STATEMENT Heterogeneous nuclear ribonucleoprotein U (hnRNP U) belongs to a family of RNA-binding proteins that play important roles in controlling gene expression. Recent studies have established a strong link between mutations of hnRNP U and human epilepsies and intellectual disability. However, it is unclear how mutations of hnRNP U may cause such disorders. This study shows that mutations of HRPU-2, a worm homolog of mammalian hnRNP U, result in dysfunction of a Slo2 potassium channel, which is critical to neuronal function. Because mutations of Slo2 channels are also strongly associated with epileptic encephalopathies and intellectual disability in humans, the findings of this study point to a potential mechanism underlying neurological disorders caused by hnRNP U mutations.
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15
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Trafficking of neuronal calcium channels. Neuronal Signal 2017; 1:NS20160003. [PMID: 32714572 PMCID: PMC7373241 DOI: 10.1042/ns20160003] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2017] [Revised: 01/20/2017] [Accepted: 01/19/2017] [Indexed: 12/18/2022] Open
Abstract
Neuronal voltage-gated calcium channels (VGCCs) serve complex yet essential physiological functions via their pivotal role in translating electrical signals into intracellular calcium elevations and associated downstream signalling pathways. There are a number of regulatory mechanisms to ensure a dynamic control of the number of channels embedded in the plasma membrane, whereas alteration of the surface expression of VGCCs has been linked to various disease conditions. Here, we provide an overview of the mechanisms that control the trafficking of VGCCs to and from the plasma membrane, and discuss their implication in pathophysiological conditions and their potential as therapeutic targets.
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16
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Stockley J, Markert E, Zhou Y, Robson CN, Elliott DJ, Lindberg J, Leung HY, Rajan P. The RNA-binding protein Sam68 regulates expression and transcription function of the androgen receptor splice variant AR-V7. Sci Rep 2015; 5:13426. [PMID: 26310125 PMCID: PMC4550848 DOI: 10.1038/srep13426] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Accepted: 07/27/2015] [Indexed: 12/02/2022] Open
Abstract
Castration-resistant (CR) prostate cancer (PCa) partly arises due to persistence of androgen receptor (AR) transcriptional activity in the absence of cognate ligand. An emerging mechanism underlying the CRPCa phenotype and predicting response to therapy is the expression of the constitutively-active AR-V7 splice variant generated by AR cryptic exon 3b inclusion. Here, we explore the role of the RNA-binding protein (RBP) Sam68 (encoded by KHDRBS1), which is over-expressed in clinical PCa, on AR-V7 expression and transcription function. Using a minigene reporter, we show that Sam68 controls expression of exon 3b resulting in an increase in endogenous AR-V7 mRNA and protein expression in RNA-binding-dependent manner. We identify a novel protein-protein interaction between Sam68 and AR-V7 mediated by a common domain shared with full-length AR, and observe these proteins in the cell nucleoplasm. Using a luciferase reporter, we demonstrate that Sam68 co-activates ligand-independent AR-V7 transcriptional activity in an RNA-binding-independent manner, and controls expression of the endogenous AR-V7-specific gene target UBE2C. Our data suggest that Sam68 has separable effects on the regulation of AR-V7 expression and transcriptional activity, through its RNA-binding capacity. Sam68 and other RBPs may control expression of AR-V7 and other splice variants as well as their downstream functions in CRPCa.
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MESH Headings
- Adaptor Proteins, Signal Transducing/genetics
- Adaptor Proteins, Signal Transducing/metabolism
- Alternative Splicing/genetics
- Cell Line, Tumor
- DNA-Binding Proteins/genetics
- DNA-Binding Proteins/metabolism
- Exons/genetics
- Gene Expression Regulation, Neoplastic
- HEK293 Cells
- Humans
- Male
- Models, Biological
- Prostatic Neoplasms/genetics
- Protein Binding
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA-Binding Proteins/genetics
- RNA-Binding Proteins/metabolism
- Receptors, Androgen/chemistry
- Receptors, Androgen/genetics
- Transcription, Genetic
- Ubiquitin-Conjugating Enzymes/genetics
- Ubiquitin-Conjugating Enzymes/metabolism
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Affiliation(s)
| | - Elke Markert
- Institute of Cancer Sciences, University of Glasgow, Glasgow, UK
| | - Yan Zhou
- Cancer Research UK Beatson Institute, Glasgow, UK
| | - Craig N. Robson
- Northern Institute for Cancer Research, Newcastle University, Newcastle-upon-Tyne, UK
| | - David J. Elliott
- Institute of Genetic Medicine, Newcastle University, Newcastle-upon-Tyne, UK
| | - Johan Lindberg
- Department of Molecular Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden
| | - Hing Y. Leung
- Institute of Cancer Sciences, University of Glasgow, Glasgow, UK
- Cancer Research UK Beatson Institute, Glasgow, UK
| | - Prabhakar Rajan
- Institute of Cancer Sciences, University of Glasgow, Glasgow, UK
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17
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Barceló C, Etchin J, Mansour MR, Sanda T, Ginesta MM, Sanchez-Arévalo Lobo VJ, Real FX, Capellà G, Estanyol JM, Jaumot M, Look AT, Agell N. Ribonucleoprotein HNRNPA2B1 interacts with and regulates oncogenic KRAS in pancreatic ductal adenocarcinoma cells. Gastroenterology 2014; 147:882-892.e8. [PMID: 24998203 DOI: 10.1053/j.gastro.2014.06.041] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Revised: 06/26/2014] [Accepted: 06/29/2014] [Indexed: 12/20/2022]
Abstract
BACKGROUND & AIMS Development of pancreatic ductal adenocarcinoma (PDAC) involves activation of c-Ki-ras2 Kirsten rat sarcoma oncogene homolog (KRAS) signaling, but little is known about the roles of proteins that regulate the activity of oncogenic KRAS. We investigated the activities of proteins that interact with KRAS in PDAC cells. METHODS We used mass spectrometry to demonstrate that heterogeneous nuclear ribonucleoproteins (HNRNP) A2 and B1 (encoded by the gene HNRNPA2B1) interact with KRAS G12V. We used co-immunoprecipitation analyses to study interactions between HNRNPA2B1 and KRAS in KRAS-dependent and KRAS-independent PDAC cell lines. We knocked down HNRNPA2B1 using small hairpin RNAs and measured viability, anchorage-independent proliferation, and growth of xenograft tumors in mice. We studied KRAS phosphorylation using the Phos-tag system. RESULTS We found that interactions between HRNPA2B1 and KRAS correlated with KRAS-dependency of some human PDAC cell lines. Knock down of HNRNPA2B1 significantly reduced viability, anchorage-independent proliferation, and formation of xenograft tumors by KRAS-dependent PDAC cells. HNRNPA2B1 knock down also increased apoptosis of KRAS-dependent PDAC cells, inactivated c-akt murine thymoma oncogene homolog 1 signaling via mammalian target of rapamycin, and reduced interaction between KRAS and phosphatidylinositide 3-kinase. Interaction between HNRNPA2B1 and KRAS required KRAS phosphorylation at serine 181. CONCLUSIONS In KRAS-dependent PDAC cell lines, HNRNPA2B1 interacts with and regulates the activity of KRAS G12V and G12D. HNRNPA2B1 is required for KRAS activation of c-akt murine thymoma oncogene homolog 1-mammalian target of rapamycin signaling, interaction with phosphatidylinositide 3-kinase, and PDAC cell survival and tumor formation in mice. HNRNPA2B1 might be a target for treatment of pancreatic cancer.
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Affiliation(s)
- Carles Barceló
- Departament de Biologia Cellular, Immunologia i Neurociències, Facultat de Medicina, IDIBAPS, Universitat de Barcelona, Barcelona, Spain
| | - Julia Etchin
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts
| | - Marc R Mansour
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts
| | - Takaomi Sanda
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts; Cancer Science Institute of Singapore, National University of Singapore, Singapore
| | - Mireia M Ginesta
- Hereditary Cancer Program, Translational Research Laboratory, Catalan Institute of Oncology, ICO-IDIBELL, Hospitalet de Llobregat, Barcelona, Spain
| | - Victor J Sanchez-Arévalo Lobo
- Grupo de Carcinogénesis Epitelial, Programa de Patología Molecular, CNIO-Spanish National Cancer Research Center, Madrid, Spain
| | - Francisco X Real
- Grupo de Carcinogénesis Epitelial, Programa de Patología Molecular, CNIO-Spanish National Cancer Research Center, Madrid, Spain
| | - Gabriel Capellà
- Hereditary Cancer Program, Translational Research Laboratory, Catalan Institute of Oncology, ICO-IDIBELL, Hospitalet de Llobregat, Barcelona, Spain
| | - Josep M Estanyol
- Centres Científics i Tecnològics-UB (CCiTUB), Universitat de Barcelona, Barcelona, Spain
| | - Montserrat Jaumot
- Departament de Biologia Cellular, Immunologia i Neurociències, Facultat de Medicina, IDIBAPS, Universitat de Barcelona, Barcelona, Spain
| | - A Thomas Look
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts
| | - Neus Agell
- Departament de Biologia Cellular, Immunologia i Neurociències, Facultat de Medicina, IDIBAPS, Universitat de Barcelona, Barcelona, Spain.
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18
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Neely A, Hidalgo P. Structure-function of proteins interacting with the α1 pore-forming subunit of high-voltage-activated calcium channels. Front Physiol 2014; 5:209. [PMID: 24917826 PMCID: PMC4042065 DOI: 10.3389/fphys.2014.00209] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Accepted: 05/15/2014] [Indexed: 11/13/2022] Open
Abstract
Openings of high-voltage-activated (HVA) calcium channels lead to a transient increase in calcium concentration that in turn activate a plethora of cellular functions, including muscle contraction, secretion and gene transcription. To coordinate all these responses calcium channels form supramolecular assemblies containing effectors and regulatory proteins that couple calcium influx to the downstream signal cascades and to feedback elements. According to the original biochemical characterization of skeletal muscle Dihydropyridine receptors, HVA calcium channels are multi-subunit protein complexes consisting of a pore-forming subunit (α1) associated with four additional polypeptide chains β, α2, δ, and γ, often referred to as accessory subunits. Twenty-five years after the first purification of a high-voltage calcium channel, the concept of a flexible stoichiometry to expand the repertoire of mechanisms that regulate calcium channel influx has emerged. Several other proteins have been identified that associate directly with the α1-subunit, including calmodulin and multiple members of the small and large GTPase family. Some of these proteins only interact with a subset of α1-subunits and during specific stages of biogenesis. More strikingly, most of the α1-subunit interacting proteins, such as the β-subunit and small GTPases, regulate both gating and trafficking through a variety of mechanisms. Modulation of channel activity covers almost all biophysical properties of the channel. Likewise, regulation of the number of channels in the plasma membrane is performed by altering the release of the α1-subunit from the endoplasmic reticulum, by reducing its degradation or enhancing its recycling back to the cell surface. In this review, we discuss the structural basis, interplay and functional role of selected proteins that interact with the central pore-forming subunit of HVA calcium channels.
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Affiliation(s)
- Alan Neely
- Centro Interdisciplinario de Neurociencia de Valparaíso and Facultad de Ciencias, Universidad de Valparaíso Valparaíso, Chile
| | - Patricia Hidalgo
- Forschungszentrum Jülich, Institute of Complex Systems 4, Zelluläre Biophysik Jülich, Germany
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19
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Stockley J, Villasevil MEM, Nixon C, Ahmad I, Leung HY, Rajan P. The RNA-binding protein hnRNPA2 regulates β-catenin protein expression and is overexpressed in prostate cancer. RNA Biol 2014; 11:755-65. [PMID: 24823909 PMCID: PMC4156506 DOI: 10.4161/rna.28800] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2014] [Revised: 03/25/2014] [Accepted: 04/06/2014] [Indexed: 01/22/2023] Open
Abstract
INTRODUCTION The RNA-binding protein hnRNPA2 (HNRNPA2B1) is upregulated in cancer, where it controls alternative pre-mRNA splicing of cancer-relevant genes. Cytoplasmic hnRNPA2 is reported in aggressive cancers, but is functionally uncharacterized. We explored the role of hnRNPA2 in prostate cancer (PCa). METHODS hnRNPA2 function/localization/expression in PCa was determined using biochemical approaches (colony forming/proliferation/luciferase reporter assays/flow cytometry/immunohistocytochemistry). Binding of hnRNPA2 within cancer-relevant 3'-UTR mRNAs was identified by bioinformatics. RESULTS RNAi-mediated knockdown of hnRNPA2 reduced colony forming and proliferation, while hnRNPA2 overexpression increased proliferation of PCa cells. Nuclear hnRNPA2 is overexpressed in high-grade clinical PCa, and is also observed in the cytoplasm in some cases. Ectopic expression of a predominantly cytoplasmic variant hnRNPA2-ΔRGG also increased PCa cell proliferation, suggesting that cytoplasmic hnRNPA2 may also be functionally relevant in PCa. Consistent with its known cytoplasmic roles, hnRNPA2 was associated with 3'-UTR mRNAs of several cancer-relevant mRNAs including β-catenin (CTNNB1). Both wild-type hnRNPA2 and hnRNPA2-ΔRGG act on CTNNB1 3'-UTR mRNA, increasing endogenous CTNNB1 mRNA expression and β-catenin protein expression and nuclear localization. CONCLUSION Nuclear and cytoplasmic hnRNPA2 are present in PCa and appear to be functionally important. Cytoplasmic hnRNPA2 may affect the cancer cell phenotype through 3'-UTR mRNA-mediated regulation of β-catenin expression and other cancer-relevant genes.
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Affiliation(s)
- Jacqueline Stockley
- Institute of Cancer Sciences; College of Medical, Veterinary, and Life Sciences; University of Glasgow; Cancer Research UK Beatson Institute; Bearsden, UK
| | - M Eugenia M Villasevil
- Institute of Cancer Sciences; College of Medical, Veterinary, and Life Sciences; University of Glasgow; Cancer Research UK Beatson Institute; Bearsden, UK
| | - Colin Nixon
- Cancer Research UK Beatson Institute; The Beatson Institute for Cancer Research; Bearsden, UK
| | - Imran Ahmad
- Institute of Cancer Sciences; College of Medical, Veterinary, and Life Sciences; University of Glasgow; Cancer Research UK Beatson Institute; Bearsden, UK
| | - Hing Y Leung
- Institute of Cancer Sciences; College of Medical, Veterinary, and Life Sciences; University of Glasgow; Cancer Research UK Beatson Institute; Bearsden, UK
- Cancer Research UK Beatson Institute; The Beatson Institute for Cancer Research; Bearsden, UK
| | - Prabhakar Rajan
- Institute of Cancer Sciences; College of Medical, Veterinary, and Life Sciences; University of Glasgow; Cancer Research UK Beatson Institute; Bearsden, UK
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20
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Fragile X mental retardation protein controls synaptic vesicle exocytosis by modulating N-type calcium channel density. Nat Commun 2014; 5:3628. [PMID: 24709664 PMCID: PMC3982139 DOI: 10.1038/ncomms4628] [Citation(s) in RCA: 98] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2013] [Accepted: 03/12/2014] [Indexed: 12/25/2022] Open
Abstract
Fragile X syndrome (FXS), the most common heritable form of mental retardation, is
characterized by synaptic dysfunction. Synaptic transmission depends critically on
presynaptic calcium entry via voltage-gated calcium (CaV) channels. Here
we show that the functional expression of neuronal N-type CaV channels
(CaV2.2) is
regulated by fragile X mental retardation
protein (FMRP).
We find that FMRP knockdown in
dorsal root ganglion neurons increases CaV channel density in somata and
in presynaptic terminals. We then show that FMRP controls CaV2.2 surface expression by targeting the channels
to the proteasome for degradation. The interaction between FMRP and CaV2.2 occurs between the carboxy-terminal domain
of FMRP and domains of
CaV2.2 known to
interact with the neurotransmitter release machinery. Finally, we show that
FMRP controls synaptic
exocytosis via CaV2.2
channels. Our data indicate that FMRP is a potent regulator of presynaptic activity, and its loss
is likely to contribute to synaptic dysfunction in FXS. Mutations in the fragile X mental retardation protein are
implicated in synaptic dysfunction in fragile X syndrome. Here, Ferron et al.
show that fragile X mental retardation protein maintains proper neurotransmission by
regulating the density of N-type calcium channels in the presynaptic terminal.
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α2δ-1 gene deletion affects somatosensory neuron function and delays mechanical hypersensitivity in response to peripheral nerve damage. J Neurosci 2013; 33:16412-26. [PMID: 24133248 DOI: 10.1523/jneurosci.1026-13.2013] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The α2δ-1 subunit of voltage-gated calcium channels is upregulated after sensory nerve injury and is also the therapeutic target of gabapentinoid drugs. It is therefore likely to play a key role in the development of neuropathic pain. In this study, we have examined mice in which α2δ-1 gene expression is disrupted, to determine whether α2δ-1 is involved in various modalities of nociception, and for the development of behavioral hypersensitivity after partial sciatic nerve ligation (PSNL). We find that naive α2δ-1(-/-) mice show a marked behavioral deficit in mechanical and cold sensitivity, but no change in thermal nociception threshold. The lower mechanical sensitivity is mirrored by a reduced in vivo electrophysiological response of dorsal horn wide dynamic range neurons. The CaV2.2 level is reduced in brain and spinal cord synaptosomes from α2δ-1(-/-) mice, and α2δ-1(-/-) DRG neurons exhibit lower calcium channel current density. Furthermore, a significantly smaller number of DRG neurons respond to the TRPM8 agonist menthol. After PSNL, α2δ-1(-/-) mice show delayed mechanical hypersensitivity, which only develops at 11 d after surgery, whereas in wild-type littermates it is maximal at the earliest time point measured (3 d). There is no compensatory upregulation of α2δ-2 or α2δ-3 after PSNL in α2δ-1(-/-) mice, and other transcripts, including neuropeptide Y and activating transcription factor-3, are upregulated normally. Furthermore, the ability of pregabalin to alleviate mechanical hypersensitivity is lost in PSNL α2δ-1(-/-) mice. Thus, α2δ-1 is essential for rapid development of mechanical hypersensitivity in a nerve injury model of neuropathic pain.
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22
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TARP γ-7 selectively enhances synaptic expression of calcium-permeable AMPARs. Nat Neurosci 2013; 16:1266-74. [PMID: 23872597 PMCID: PMC3858651 DOI: 10.1038/nn.3473] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Accepted: 06/13/2013] [Indexed: 12/14/2022]
Abstract
Regulation of calcium-permeable AMPA receptors (CP-AMPARs) is crucial in normal synaptic function and neurological disease states. Although transmembrane AMPAR regulatory proteins (TARPs) such as stargazin (γ-2) modulate the properties of calcium-impermeable AMPARs (CI-AMPARs) and promote their synaptic targeting, the TARP-specific rules governing CP-AMPAR synaptic trafficking remain unclear. We used RNA interference to manipulate AMPAR-subunit and TARP expression in γ-2-lacking stargazer cerebellar granule cells--the classic model of TARP deficiency. We found that TARP γ-7 selectively enhanced the synaptic expression of CP-AMPARs and suppressed CI-AMPARs, identifying a pivotal role of γ-7 in regulating the prevalence of CP-AMPARs. In the absence of associated TARPs, both CP-AMPARs and CI-AMPARs were able to localize to synapses and mediate transmission, although their properties were altered. Our results also establish that TARPed synaptic receptors in granule cells require both γ-2 and γ-7 and reveal an unexpected basis for the loss of AMPAR-mediated transmission in stargazer mice.
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23
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Expression and pharmacology of endogenous Cav channels in SH-SY5Y human neuroblastoma cells. PLoS One 2013; 8:e59293. [PMID: 23536870 PMCID: PMC3607609 DOI: 10.1371/journal.pone.0059293] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2012] [Accepted: 02/13/2013] [Indexed: 12/24/2022] Open
Abstract
SH-SY5Y human neuroblastoma cells provide a useful in vitro model to study the mechanisms underlying neurotransmission and nociception. These cells are derived from human sympathetic neuronal tissue and thus, express a number of the Cav channel subtypes essential for regulation of important physiological functions, such as heart contraction and nociception, including the clinically validated pain target Cav2.2. We have detected mRNA transcripts for a range of endogenous expressed subtypes Cav1.3, Cav2.2 (including two Cav1.3, and three Cav2.2 splice variant isoforms) and Cav3.1 in SH-SY5Y cells; as well as Cav auxiliary subunits α2δ1–3, β1, β3, β4, γ1, γ4–5, and γ7. Both high- and low-voltage activated Cav channels generated calcium signals in SH-SY5Y cells. Pharmacological characterisation using ω-conotoxins CVID and MVIIA revealed significantly (∼ 10-fold) higher affinity at human versus rat Cav2.2, while GVIA, which interacts with Cav2.2 through a distinct pharmacophore had similar affinity for both species. CVID, GVIA and MVIIA affinity was higher for SH-SY5Y membranes vs whole cells in the binding assays and functional assays, suggesting auxiliary subunits expressed endogenously in native systems can strongly influence Cav2.2 channels pharmacology. These results may have implications for strategies used to identify therapeutic leads at Cav2.2 channels.
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Vink S, Alewood PF. Targeting voltage-gated calcium channels: developments in peptide and small-molecule inhibitors for the treatment of neuropathic pain. Br J Pharmacol 2013; 167:970-89. [PMID: 22725651 DOI: 10.1111/j.1476-5381.2012.02082.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Chronic pain affects approximately 20% of people worldwide and places a large economic and social burden on society. Despite the availability of a range of analgesics, this condition is inadequately treated, with complete alleviation of symptoms rarely occurring. In the past 30 years, the voltage-gated calcium channels (VGCCs) have been recognized as potential targets for analgesic development. Although the majority of the research has been focused on Ca(v) 2.2 in particular, other VGCC subtypes such as Ca(v) 3.2 have recently come to the forefront of analgesic research. Venom peptides from marine cone snails have been proven to be a valuable tool in neuroscience, playing a major role in the identification and characterization of VGCC subtypes and producing the first conotoxin-based drug on the market, the ω-conotoxin, ziconotide. This peptide potently and selectively inhibits Ca(v) 2.2, resulting in analgesia in chronic pain states. However, this drug is only available via intrathecal administration, and adverse effects and a narrow therapeutic window have limited its use in the clinic. Other Ca(v) 2.2 inhibitors are currently in development and offer the promise of an improved route of administration and safety profile. This review assesses the potential of targeting VGCCs for analgesic development, with a main focus on conotoxins that block Ca(v) 2.2 and the developments made to transform them into therapeutics.
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Affiliation(s)
- S Vink
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, The University of Queensland, Brisbane, Australia
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Thompson WR, Majid AS, Czymmek KJ, Ruff AL, García J, Duncan RL, Farach-Carson MC. Association of the α(2)δ(1) subunit with Ca(v)3.2 enhances membrane expression and regulates mechanically induced ATP release in MLO-Y4 osteocytes. J Bone Miner Res 2011; 26:2125-39. [PMID: 21638318 PMCID: PMC4478606 DOI: 10.1002/jbmr.437] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Voltage-sensitive calcium channels (VSCCs) mediate signaling events in bone cells in response to mechanical loading. Osteoblasts predominantly express L-type VSCCs composed of the α(1) pore-forming subunit and several auxiliary subunits. Osteocytes, in contrast, express T-type VSCCs and a relatively small amount of L-type α(1) subunits. Auxiliary VSCC subunits have several functions, including modulating gating kinetics, trafficking of the channel, and phosphorylation events. The influence of the α(2)δ auxiliary subunit on T-type VSCCs and the physiologic consequences of that association are incompletely understood and have yet to be investigated in bone. In this study we postulated that the auxiliary α(2) δ subunit of the VSCC complex modulates mechanically regulated ATP release in osteocytes via its association with the T-type Ca(v) 3.2 (α(1H) ) subunit. We demonstrated by reverse-transcriptase polymerase chain reaction, Western blotting, and immunostaining that MLO-Y4 osteocyte-like cells express the T-type Ca(v)3.2(α(1H)) subunit more abundantly than the L-type Ca(v)1.2 (α(1C)) subunit. We also demonstrated that the α(2) δ(1) subunit, previously described as an L-type auxiliary subunit, complexes with the T-type Ca(v)3.2 (α(1H)) subunit in MLO-Y4 cells. Interestingly, siRNA-mediated knockdown of α(2) δ(1) completely abrogated ATP release in response to membrane stretch in MLO-Y4 cells. Additionally, knockdown of the α(2)δ(1) subunit resulted in reduced ERK1/2 activation. Together these data demonstrate a functional VSCC complex. Immunocytochemistry following α(2)δ(1) knockdown showed decreased membrane localization of Ca(v) 3.2 (α(1H)) at the plasma membrane, suggesting that the diminished ATP release and ERK1/2 activation in response to membrane stretch resulted from a lack of Ca(v) 3.2 (α(1H)) at the cell membrane.
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Affiliation(s)
- William R Thompson
- Biomechanics and Movement Science Program, University of Delaware, Newark, DE 19716, USA.
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Waithe D, Ferron L, Dolphin AC. Stargazin-related protein γ₇ is associated with signalling endosomes in superior cervical ganglion neurons and modulates neurite outgrowth. J Cell Sci 2011; 124:2049-57. [PMID: 21610096 DOI: 10.1242/jcs.084988] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The role(s) of the newly discovered stargazin-like γ-subunit proteins remains unclear; although they are now widely accepted to be transmembrane AMPA receptor regulatory proteins (TARPs), rather than Ca²⁺ channel subunits, it is possible that they have more general roles in trafficking within neurons. We previously found that γ₇ subunit is associated with vesicles when it is expressed in neurons and other cells. Here, we show that γ₇ is present mainly in retrogradely transported organelles in sympathetic neurons, where it colocalises with TrkA-YFP, and with the early endosome marker EEA1, suggesting that γ₇ localises to signalling endosomes. It was not found to colocalise with markers of the endoplasmic reticulum, mitochondria, lysosomes or late endosomes. Furthermore, knockdown of endogenous γ₇ by short hairpin RNA transfection into sympathetic neurons reduced neurite outgrowth. The same was true in the PC12 neuronal cell line, where neurite outgrowth was restored by overexpression of human γ₇. These findings open the possibility that γ₇ has an essential trafficking role in relation to neurite outgrowth as a component of endosomes involved in neurite extension and growth cone remodelling.
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Affiliation(s)
- Dominic Waithe
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
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Waithe D, Ferron L, Page KM, Chaggar K, Dolphin AC. Beta-subunits promote the expression of Ca(V)2.2 channels by reducing their proteasomal degradation. J Biol Chem 2011; 286:9598-611. [PMID: 21233207 PMCID: PMC3059031 DOI: 10.1074/jbc.m110.195909] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2010] [Revised: 12/22/2010] [Indexed: 02/03/2023] Open
Abstract
The β-subunits of voltage-gated calcium channels regulate their functional expression and properties. Two mechanisms have been proposed for this, an effect on gating and an enhancement of expression. With respect to the effect on expression, β-subunits have been suggested to enhance trafficking by masking an unidentified endoplasmic reticulum (ER) retention signal. Here we have investigated whether, and how, β-subunits affect the level of Ca(V)2.2 channels within somata and neurites of cultured sympathetic neurons. We have used YFP-Ca(V)2.2 containing a mutation (W391A), that prevents binding of β-subunits to its I-II linker and found that expression of this channel was much reduced compared with WT CFP-Ca(V)2.2 when both were expressed in the same neuron. This effect was particularly evident in neurites and growth cones. The difference between the levels of YFP-Ca(V)2.2(W391A) and CFP-Ca(V)2.2(WT) was lost in the absence of co-expressed β-subunits. Furthermore, the relative reduction of expression of Ca(V)2.2(W391A) compared with the WT channel was reversed by exposure to two proteasome inhibitors, MG132 and lactacystin, particularly in the somata. In further experiments in tsA-201 cells, we found that proteasome inhibition did not augment the cell surface Ca(V)2.2(W391A) level but resulted in the observation of increased ubiquitination, particularly of mutant channels. In contrast, we found no evidence for selective retention of Ca(V)2.2(W391A) in the ER, in either the soma or growth cones. In conclusion, there is a marked effect of β-subunits on Ca(V)2.2 expression, particularly in neurites, but our results point to protection from proteasomal degradation rather than masking of an ER retention signal.
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Affiliation(s)
- Dominic Waithe
- From the Department of Neuroscience, Physiology and Pharmacology, University College London, Gower St., London WC1E 6BT, United Kingdom
| | - Laurent Ferron
- From the Department of Neuroscience, Physiology and Pharmacology, University College London, Gower St., London WC1E 6BT, United Kingdom
| | - Karen M. Page
- From the Department of Neuroscience, Physiology and Pharmacology, University College London, Gower St., London WC1E 6BT, United Kingdom
| | - Kanchan Chaggar
- From the Department of Neuroscience, Physiology and Pharmacology, University College London, Gower St., London WC1E 6BT, United Kingdom
| | - Annette C. Dolphin
- From the Department of Neuroscience, Physiology and Pharmacology, University College London, Gower St., London WC1E 6BT, United Kingdom
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Yang L, Katchman A, Morrow JP, Doshi D, Marx SO. Cardiac L-type calcium channel (Cav1.2) associates with gamma subunits. FASEB J 2010; 25:928-36. [PMID: 21127204 DOI: 10.1096/fj.10-172353] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The cardiac voltage-gated Ca(2+) channel, Ca(v)1.2, mediates excitation-contraction coupling in the heart. The molecular composition of the channel includes the pore-forming α1 subunit and auxiliary α2/δ-1 and β subunits. Ca(2+) channel γ subunits, of which there are 8 isoforms, consist of 4 transmembrane domains with intracellular N- and C-terminal ends. The γ1 subunit was initially detected in the skeletal muscle Ca(v)1.1 channel complex, modulating current amplitude and activation and inactivation properties. The γ1 subunit also shifts the steady-state inactivation to more negative membrane potentials, accelerates current inactivation, and increases peak currents, when coexpressed with the cardiac α1c subunit in Xenopus oocytes and human embryonic kidney (HEK) 293 cells. The γ1 subunit is not expressed, however, in cardiac muscle. We sought to determine whether γ subunits that are expressed in cardiac tissue physically associate with and modulate Ca(v)1.2 function. We now demonstrate that γ4, γ6, γ7, and γ8 subunits physically interact with the Ca(v)1.2 complex. The γ subunits differentially modulate Ca(2+) channel function when coexpressed with the β1b and α2/δ-1 subunits in HEK cells, altering both activation and inactivation properties. The effects of γ on Ca(v)1.2 function are dependent on the subtype of β subunit. Our results identify new members of the cardiac Ca(v)1.2 macromolecular complex and identify a mechanism by which to increase the functional diversity of Ca(v)1.2 channels.
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Affiliation(s)
- Lin Yang
- Division of Cardiology, Department of Medicine, Columbia University, College of Physicians and Surgeons, 622 W. 168th St., New York, NY 10032, USA
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Abstract
Calcium regulates a wide spectrum of physiological processes such as heartbeat, muscle contraction, neuronal communication, hormone release, cell division, and gene transcription. Major entryways for Ca(2+) in excitable cells are high-voltage activated (HVA) Ca(2+) channels. These are plasma membrane proteins composed of several subunits, including α(1), α(2)δ, β, and γ. Although the principal α(1) subunit (Ca(v)α(1)) contains the channel pore, gating machinery and most drug binding sites, the cytosolic auxiliary β subunit (Ca(v)β) plays an essential role in regulating the surface expression and gating properties of HVA Ca(2+) channels. Ca(v)β is also crucial for the modulation of HVA Ca(2+) channels by G proteins, kinases, and the Ras-related RGK GTPases. New proteins have emerged in recent years that modulate HVA Ca(2+) channels by binding to Ca(v)β. There are also indications that Ca(v)β may carry out Ca(2+) channel-independent functions, including directly regulating gene transcription. All four subtypes of Ca(v)β, encoded by different genes, have a modular organization, consisting of three variable regions, a conserved guanylate kinase (GK) domain, and a conserved Src-homology 3 (SH3) domain, placing them into the membrane-associated guanylate kinase (MAGUK) protein family. Crystal structures of Ca(v)βs reveal how they interact with Ca(v)α(1), open new research avenues, and prompt new inquiries. In this article, we review the structure and various biological functions of Ca(v)β, with both a historical perspective as well as an emphasis on recent advances.
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Affiliation(s)
- Zafir Buraei
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
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Tselnicker I, Tsemakhovich VA, Dessauer CW, Dascal N. Stargazin modulates neuronal voltage-dependent Ca(2+) channel Ca(v)2.2 by a Gbetagamma-dependent mechanism. J Biol Chem 2010; 285:20462-71. [PMID: 20435886 DOI: 10.1074/jbc.m110.121277] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Loss of neuronal protein stargazin (gamma(2)) is associated with recurrent epileptic seizures and ataxia in mice. Initially, due to homology to the skeletal muscle calcium channel gamma(1) subunit, stargazin and other family members (gamma(3-8)) were classified as gamma subunits of neuronal voltage-gated calcium channels (such as Ca(V)2.1-Ca(V)2.3). Here, we report that stargazin interferes with G protein modulation of Ca(V)2.2 (N-type) channels expressed in Xenopus oocytes. Stargazin counteracted the Gbetagamma-induced inhibition of Ca(V)2.2 channel currents, caused either by coexpression of the Gbetagamma dimer or by activation of a G protein-coupled receptor. Expression of high doses of Gbetagamma overcame the effects of stargazin. High affinity Gbetagamma scavenger proteins m-cbetaARK and m-phosducin produced effects similar to stargazin. The effects of stargazin and m-cbetaARK were not additive, suggesting a common mechanism of action, and generally independent of the presence of the Ca(V)beta(3) subunit. However, in some cases, coexpression of Ca(V)beta(3) blunted the modulation by stargazin. Finally, the Gbetagamma-opposing action of stargazin was not unique to Ca(V)2.2, as stargazin also inhibited the Gbetagamma-mediated activation of the G protein-activated K(+) channel. Purified cytosolic C-terminal part of stargazin bound Gbetagamma in vitro. Our results suggest that the regulation by stargazin of biophysical properties of Ca(V)2.2 are not exerted by direct modulation of the channel but via a Gbetagamma-dependent mechanism.
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Affiliation(s)
- Isabella Tselnicker
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel.
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31
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Gronich N, Kumar A, Zhang Y, Efimov IR, Soldatov NM. Molecular remodeling of ion channels, exchangers and pumps in atrial and ventricular myocytes in ischemic cardiomyopathy. Channels (Austin) 2010; 4:101-7. [PMID: 20090424 PMCID: PMC2891309 DOI: 10.4161/chan.4.2.10975] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Existing molecular knowledge base of cardiovascular diseases is rudimentary because of lack of specific attribution to cell type and function. The aim of this study was to investigate cell-specific molecular remodeling in human atrial and ventricular myocytes associated with ischemic cardiomyopathy. Our strategy combines two technological innovations, laser-capture microdissection of identified cardiac cells in selected anatomical regions of the heart and splice microarray of a narrow catalog of the functionally most important genes regulating ion homeostasis. We focused on expression of a principal family of genes coding for ion channels, exchangers and pumps (CE&P genes) that are involved in electrical, mechanical and signaling functions of the heart and constitute the most utilized drug targets. We found that (1) CE&P genes remodel in a cell-specific manner: ischemic cardiomyopathy affected 63 CE&P genes in ventricular myocytes and 12 essentially different genes in atrial myocytes. (2) Only few of the identified CE&P genes were previously linked to human cardiac disfunctions. (3) The ischemia-affected CE&P genes include nuclear chloride channels, adrenoceptors, cyclic nucleotide-gated channels, auxiliary subunits of Na(+), K(+) and Ca(2+) channels, and cell-surface CE&Ps. (4) In both atrial and ventricular myocytes ischemic cardiomyopathy reduced expression of CACNG7 and induced overexpression of FXYD1, the gene crucial for Na(+) and K(+) homeostasis. Thus, our cell-specific molecular profiling defined new landmarks for correct molecular modeling of ischemic cardiomyopathy and development of underlying targeted therapies.
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Affiliation(s)
- Naomi Gronich
- National Institute on Aging; National Institutes of health; Baltimore, MD USA
| | - Azad Kumar
- National Institute on Aging; National Institutes of health; Baltimore, MD USA
| | - Yuwei Zhang
- National Institute on Aging; National Institutes of health; Baltimore, MD USA
| | | | - Nikolai M. Soldatov
- National Institute on Aging; National Institutes of health; Baltimore, MD USA
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Calcium channel diversity: multiple roles of calcium channel subunits. Curr Opin Neurobiol 2009; 19:237-44. [PMID: 19559597 DOI: 10.1016/j.conb.2009.06.006] [Citation(s) in RCA: 172] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2009] [Revised: 05/31/2009] [Accepted: 06/05/2009] [Indexed: 12/21/2022]
Abstract
Until recently we held the simple view that voltage-gated calcium channels consisted of an alpha1 subunit, usually associated with auxiliary beta subunits and alpha(2)delta subunits and that skeletal muscle calcium channels were also associated with a gamma subunit. However, as discussed here, there is now evidence that the auxiliary subunits may also perform other roles unrelated to voltage-gated calcium entry. In the past students were taught the simplistic view that second messenger signaling to voltage-gated calcium channels involved mainly phosphorylation of L-type calcium channels, Ca(2+)-dependent inactivation via calmodulin, and direct G-protein-mediated inhibition of the neuronal N and P/Q channels. However, it is now clear that there are many other means of modulating calcium channel activity, including receptor-mediated internalization, proteolytic cleavage, phosphorylation of beta subunits, and interaction of calcium channels with other proteins, including enzymes masquerading as scaffold proteins.
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Coombs ID, Cull-Candy SG. Transmembrane AMPA receptor regulatory proteins and AMPA receptor function in the cerebellum. Neuroscience 2009; 162:656-65. [PMID: 19185052 PMCID: PMC3217091 DOI: 10.1016/j.neuroscience.2009.01.004] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2008] [Accepted: 01/05/2009] [Indexed: 11/16/2022]
Abstract
Heterogeneity among AMPA receptor (AMPAR) subtypes is thought to be one of the key postsynaptic factors giving rise to diversity in excitatory synaptic signaling in the CNS. Recently, compelling evidence has emerged that ancillary AMPAR subunits—the so-called transmembrane AMPA receptor regulatory proteins (TARPs)—also play a vital role in influencing the variety of postsynaptic signaling. This TARP family of molecules controls both trafficking and functional properties of AMPARs at most, if not all, excitatory central synapses. Furthermore, individual TARPs differ in their effects on the biophysical and pharmacological properties of AMPARs. The critical importance of TARPs in synaptic transmission was first revealed in experiments on cerebellar granule cells from stargazer mice. These lack the prototypic TARP stargazin, present in granule cells from wild-type animals, and consequently lack synaptic transmission at the mossy fibre-to-granule cell synapse. Subsequent work has identified many other members of the stargazin family which act as functional TARPs. It has also provided valuable information about specific TARPs present in many central neurons. Because much of the initial work on TARPs was carried out on stargazer granule cells, the important functional properties of TARPs present throughout the cerebellum have received particular attention. Here we discuss some of these recent findings in relation to the main TARPs and the AMPAR subunits identified in cerebellar neurons and glia.
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Affiliation(s)
- I D Coombs
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK
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