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Furlan S, Paradiso B, Greotti E, Volpe P, Nori A. Calsequestrin in Purkinje cells of mammalian cerebellum. Acta Histochem 2023; 125:152001. [PMID: 36669254 DOI: 10.1016/j.acthis.2023.152001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 01/11/2023] [Accepted: 01/16/2023] [Indexed: 01/21/2023]
Abstract
Cerebellum is devoted to motor coordination and cognitive functions. Endoplasmic reticulum is the largest intracellular calcium store involved in all neuronal functions. Intralumenal calcium binding proteins play a pivotal role in calcium storage and contribute to both calcium release and uptake. Calsequestrin, a key calcium binding protein of sarco-endoplasmic reticulum in skeletal and cardiac muscles, was identified in chicken and fish cerebellum Purkinje cells, but its expression in mammals and human counterpart has not been studied in depth. Aim of the present paper was to investigate expression and localization of Calsequestrin in mammalian cerebellum. Calsequestrin was found to be expressed at low level in cerebellum, but specifically concentrated in Calbindin D28- and zebrin- immunopositive-Purkinje cells. Two additional fundamental calcium store markers, sarco-endoplasmic calcium pump isoform 2, SERCA2, and Inositol-trisphosphate receptor isoform 1, IP3R1, were found to be co-expressed in the region, with some localization peculiarities. In conclusion, a new marker was identified for Purkinje cells in adult mammals, including humans. Such a marker might help in staminal neuronal cells specification and in dissection of still unknown neurodegeneration and physio-pathological effects of dysregulated calcium homeostasis.
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Affiliation(s)
- Sandra Furlan
- National Research Council, Institute of Neuroscience, 35121 Padova, Italy
| | - Beatrice Paradiso
- General Pathology Unit, Dolo Hospital, Riviera XXIX Aprile, 2, 30031 Dolo, Venice, Italy
| | - Elisa Greotti
- National Research Council, Institute of Neuroscience, 35121 Padova, Italy; University of Padova, Department of Biomedical Sciences and Interdepartmental Research Center of Myology (cirMYO), 35131 Padova, Italy; Padova Neuroscience Center (PNC), University of Padova, Padua, Italy
| | - Pompeo Volpe
- University of Padova, Department of Biomedical Sciences and Interdepartmental Research Center of Myology (cirMYO), 35131 Padova, Italy
| | - Alessandra Nori
- University of Padova, Department of Biomedical Sciences and Interdepartmental Research Center of Myology (cirMYO), 35131 Padova, Italy.
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Zheng L, Lindsay A, McSweeney K, Aplin J, Forbes K, Smith S, Tunwell R, Mackrill JJ. Ryanodine receptor calcium release channels in trophoblasts and their role in cell migration. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2021; 1869:119139. [PMID: 34624436 DOI: 10.1016/j.bbamcr.2021.119139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 09/03/2021] [Accepted: 09/19/2021] [Indexed: 10/20/2022]
Abstract
Trophoblasts are specialized epithelial cells of the placenta that are involved in invasion, communication and the exchange of materials between the mother and fetus. Cytoplasmic Ca2+ ([Ca2+]c) plays critical roles in regulating such processes in other cell types, but relatively little is known about the mechanisms that control this second messenger in trophoblasts. In the current study, the presence of RyRs and their accessory proteins in placental tissues and in the BeWo choriocarcinoma, a model trophoblast cell-line, were examined using immunohistochemistry and Western immunoblotting. Contributions of RyRs to Ca2+ signalling and to random migration in BeWo cells were investigated using fura-2 fluorescent and brightfield videomicroscopy. The effect of RyR inhibition on reorganization of the F-actin cytoskeleton elicited by the hormone angiotensin II, was determined using phalloidin-labelling and confocal microscopy. RyR1 and RyR3 proteins were detected in trophoblasts of human first trimester and term placental villi, along with the accessory proteins triadin and calsequestrin. Similarly, RyR1, RyR3, triadin and calsequestrin were detected in BeWo cells. In this cell-line, activation of RyRs with micromolar ryanodine increased [Ca2+]c, whereas pharmacological inhibition of these channels reduced Ca2+ transients elicited by the peptide hormones angiotensin II, arginine vasopressin and endothelin 1. Angiotensin II increased the velocity, total distance and Euclidean distance of random migration by BeWo cells and these effects were significantly reduced by tetracaine and by inhibitory concentrations of ryanodine. RyRs contribute to reorganization of the F-actin cytoskeleton elicited by angiotensin II, since inhibition of these channels restores the parallelness of these structures to control levels. These findings demonstrate that trophoblasts contain a suite of proteins similar to those in other cell types possessing highly developed Ca2+ signal transduction systems, such as skeletal muscle. They also indicate that these channels regulate the migration of trophoblast cells, a process that plays a key role in development of the placenta.
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Affiliation(s)
- Limian Zheng
- Department of Physiology, University College Cork, Ireland
| | - Andrew Lindsay
- School of Biochemistry and Cell Biology, University College Cork, Ireland
| | - Kate McSweeney
- Department of Physiology, University College Cork, Ireland
| | - John Aplin
- Maternal and Fetal Health Research Centre, University of Manchester, UK
| | - Karen Forbes
- Maternal and Fetal Health Research Centre, University of Manchester, UK; Leeds Centre for Reproduction and Early Development, University of Leeds, UK
| | - Samantha Smith
- Maternal and Fetal Health Research Centre, University of Manchester, UK
| | - Richard Tunwell
- Division of Biosciences, University College London, Gower Street, London, UK
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Furlan S, Campione M, Murgia M, Mosole S, Argenton F, Volpe P, Nori A. Calsequestrins New Calcium Store Markers of Adult Zebrafish Cerebellum and Optic Tectum. Front Neuroanat 2020; 14:15. [PMID: 32372920 PMCID: PMC7188384 DOI: 10.3389/fnana.2020.00015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Accepted: 03/18/2020] [Indexed: 12/26/2022] Open
Abstract
Calcium stores in neurons are heterogeneous in compartmentalization and molecular composition. Danio rerio (zebrafish) is an animal model with a simply folded cerebellum similar in cellular organization to that of mammals. The aim of the study was to identify new endoplasmic reticulum (ER) calcium store markers in zebrafish adult brain with emphasis on cerebellum and optic tectum. By quantitative polymerase chain reaction, we found three RNA transcripts coding for the intra-ER calcium binding protein calsequestrin: casq1a, casq1b, and casq2. In brain homogenates, two isoforms were detected by mass spectrometry and western blotting. Fractionation experiments of whole brain revealed that Casq1a and Casq2 were enriched in a heavy fraction containing ER microsomes and synaptic membranes. By in situ hybridization, we found the heterogeneous expression of casq1a and casq2 mRNA to be compatible with the cellular localization of calsequestrins investigated by immunofluorescence. Casq1 was expressed in neurogenic differentiation 1 expressing the granule cells of the cerebellum and the periventricular zone of the optic tectum. Casq2 was concentrated in parvalbumin expressing Purkinje cells. At a subcellular level, Casq1 was restricted to granular cell bodies, and Casq2 was localized in cell bodies, dendrites, and axons. Data are discussed in relation to the differential cellular and subcellular distribution of other cerebellum calcium store markers and are evaluated with respect to the putative relevance of calsequestrins in the neuron-specific functional activity.
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Affiliation(s)
- Sandra Furlan
- Consiglio Nazionale delle Ricerche, Institute of Neuroscience, Padova, Italy
| | - Marina Campione
- Consiglio Nazionale delle Ricerche, Institute of Neuroscience, Padova, Italy
| | - Marta Murgia
- Department of Biomedical Sciences, University of Padova, Istituto Interuniversitario di Miologia, Padova, Italy.,Department of Proteomics and Signal Transduction, Max-Planck-Institute of Biochemistry, Martinsried, Germany
| | - Simone Mosole
- Institute of Oncology Research (IOR), Bellinzona, Switzerland
| | | | - Pompeo Volpe
- Department of Biomedical Sciences, University of Padova, Istituto Interuniversitario di Miologia, Padova, Italy
| | - Alessandra Nori
- Department of Biomedical Sciences, University of Padova, Istituto Interuniversitario di Miologia, Padova, Italy
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Chakravarty H, Bal C, Yadav M, Jena N, Bal NC, Sharon A. First Insight on Small Molecules as Cardiac Calsequestrin Stabilizers. ACS OMEGA 2019; 4:11508-11514. [PMID: 31460256 PMCID: PMC6682146 DOI: 10.1021/acsomega.9b01113] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Accepted: 06/19/2019] [Indexed: 06/10/2023]
Abstract
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is caused by mutations of cardiac calsequestrin (CASQ2) that impair its characteristic ability of Ca2+-induced polymerization-depolymerization. However, stabilizing the CASQ2 polymer by pharmacological agents to treat CPVT has not been reported so far. Here, we tested whether small molecules can stabilize CASQ2 polymers. We synthesized 24 glycinate/alaninate/acetate α-pyranone analogs and conducted the CASQ2 depolymerization assay. Most of the molecules of this class of compounds inhibited the depolymerization of the protein upon Ca2+ chelation by ethylene glycol tetraacetic acid. Structure-activity relationship studies revealed that the compounds with the 4-fluoro-phenyl group at the C-6 position of the pyranone ring and open-chain primary amine at C-4 are the most active of the class. This is the first report of an α-pyranone class of compounds with the ability to stabilize CASQ2 polymers and opens up the possibility to target Ca2+-release disorders via modulation of CASQ2 polymerization.
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Affiliation(s)
| | - Chandralata Bal
- Department
of Chemistry, Birla Institute of Technology,
Mesra, Ranchi 835215, India
| | - Monika Yadav
- Department
of Chemistry, Birla Institute of Technology,
Mesra, Ranchi 835215, India
| | - Nivedita Jena
- KIIT Technology Business Incubator and KIIT School of Biotechnology, KIIT University, Bhubaneswar 751021 India
| | - Naresh C. Bal
- KIIT Technology Business Incubator and KIIT School of Biotechnology, KIIT University, Bhubaneswar 751021 India
| | - Ashoke Sharon
- Department
of Chemistry, Birla Institute of Technology,
Mesra, Ranchi 835215, India
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Filadi R, Basso E, Lefkimmiatis K, Pozzan T. Beyond Intracellular Signaling: The Ins and Outs of Second Messengers Microdomains. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 981:279-322. [PMID: 29594866 DOI: 10.1007/978-3-319-55858-5_12] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
A typical characteristic of eukaryotic cells compared to prokaryotes is represented by the spatial heterogeneity of the different structural and functional components: for example, most of the genetic material is surrounded by a highly specific membrane structure (the nuclear membrane), continuous with, yet largely different from, the endoplasmic reticulum (ER); oxidative phosphorylation is carried out by organelles enclosed by a double membrane, the mitochondria; in addition, distinct domains, enriched in specific proteins, are present in the plasma membrane (PM) of most cells. Less obvious, but now generally accepted, is the notion that even the concentration of small molecules such as second messengers (Ca2+ and cAMP in particular) can be highly heterogeneous within cells. In the case of most organelles, the differences in the luminal levels of second messengers depend either on the existence on their membrane of proteins that allow the accumulation/release of the second messenger (e.g., in the case of Ca2+, pumps, exchangers or channels), or on the synthesis and degradation of the specific molecule within the lumen (the autonomous intramitochondrial cAMP system). It needs stressing that the existence of a surrounding membrane does not necessarily imply the existence of a gradient between the cytosol and the organelle lumen. For example, the nuclear membrane is highly permeable to both Ca2+ and cAMP (nuclear pores are permeable to solutes up to 50 kDa) and differences in [Ca2+] or [cAMP] between cytoplasm and nucleoplasm are not seen in steady state and only very transiently during cell activation. A similar situation has been observed, as far as Ca2+ is concerned, in peroxisomes.
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Affiliation(s)
- Riccardo Filadi
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Emy Basso
- Institute of Neuroscience, Padova Section, National Research Council, Padova, Italy
| | - Konstantinos Lefkimmiatis
- Institute of Neuroscience, Padova Section, National Research Council, Padova, Italy
- Venetian Institute of Molecular Medicine, Padova, Italy
| | - Tullio Pozzan
- Department of Biomedical Sciences, University of Padova, Padova, Italy.
- Institute of Neuroscience, Padova Section, National Research Council, Padova, Italy.
- Venetian Institute of Molecular Medicine, Padova, Italy.
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Ethanol-Induced Alterations in Purkinje Neuron Dendrites in Adult and Aging Rats: a Review. THE CEREBELLUM 2016; 14:466-73. [PMID: 25648753 DOI: 10.1007/s12311-014-0636-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Uncomplicated alcoholics suffer from discrete motor dysfunctions that become more pronounced with age. These deficits involve the structure and function of Purkinje neurons (PN), the sole output neurons from the cerebellar cortex. This review focuses on alterations to the PN dendritic arbor in the adult and aging Fischer 344 rat following lengthy alcohol consumption. It describes seminal studies using the Golgi-Cox method which proposed a model for ethanol-induced dendritic regression. Subsequent ultrastructural studies of PN dendrites showed dilation of the extensive smooth endoplasmic reticulum (SER) which preceded and accompanied dendritic regression. The component of the SER that was most affected by ethanol was the sarco/endoplasmic reticulum Ca(2+) ATPase pump (SERCA) responsible for resequestration of calcium into the SER. Ethanol-induced decreases in SERCA pump levels, similar to the finding of SER dilation, preceded and occurred concomitantly with dendritic regression. Discrete ethanol-induced deficits in balance also accompanied these decreases. Ethanol-induced ER stress within the SER of PN dendrites was proposed as an underlying cause of dendritic regression. It was recently shown that increased activation of caspase 12, inherent to the ER, occurred in PN of acute slices in ethanol-fed rats and was most pronounced following 40 weeks of ethanol treatment. These findings shed new light into alcohol-induced disruption in PN dendrites providing a new model for the discrete but critical changes in motor function in aging, adult alcoholics.
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Ko AR, Kim JY, Hyun HW, Kim JE. Endothelial NOS activation induces the blood-brain barrier disruption via ER stress following status epilepticus. Brain Res 2015; 1622:163-73. [PMID: 26115585 DOI: 10.1016/j.brainres.2015.06.020] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Revised: 06/03/2015] [Accepted: 06/06/2015] [Indexed: 11/19/2022]
Abstract
The blood-brain barrier (BBB) maintains the unique brain microenvironment, which is separated from the systemic circulating system. Since the endoplasmic reticulum (ER) is an important cell organelle that is responsible for protein synthesis, the correct folding and sorting of proteins contributing to cell survivals, ER stress is a potential cause of cell damage in various diseases. Therefore, it would be worthy to explore the the relationship between the ER stress and BBB disruption during vasogenic edema formation induced by epileptogenic insults. In the present study, we investigated the roles of ER stress in vasogenic edema and its related events in rat epilepsy models provoked by pilocarpine-induced status epilepticus (SE). SE-induced eNOS activation induces BBB breakdown via up-regulation of GRP78 expression and dysfunction of SMI-71 (an endothelial BBB marker) in the piriform cortex (PC). In addition, caveolin-1 peptide (an eNOS inhibitor) effectively attenuated GRP78 expression and down-regulation of SMI-71. Taken together, our findings suggest that eNOS-mediated ER stress may participate in SE-induced vasogenic edema formation. Therefore, the modulation of ER stress may be a considerable strategy for therapy in impairments of endothelial cell function.
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Affiliation(s)
- Ah-Reum Ko
- Department of Anatomy and Neurobiology, Institute of Epilepsy Research, College of Medicine, Hallym University, Chuncheon, Kangwon-Do 200702, South Korea
| | - Ji Yang Kim
- Department of Anatomy and Neurobiology, Institute of Epilepsy Research, College of Medicine, Hallym University, Chuncheon, Kangwon-Do 200702, South Korea
| | - Hye-Won Hyun
- Department of Anatomy and Neurobiology, Institute of Epilepsy Research, College of Medicine, Hallym University, Chuncheon, Kangwon-Do 200702, South Korea
| | - Ji-Eun Kim
- Department of Anatomy and Neurobiology, Institute of Epilepsy Research, College of Medicine, Hallym University, Chuncheon, Kangwon-Do 200702, South Korea.
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Stirling DP, Cummins K, Wayne Chen SR, Stys P. Axoplasmic reticulum Ca(2+) release causes secondary degeneration of spinal axons. Ann Neurol 2014; 75:220-9. [PMID: 24395428 DOI: 10.1002/ana.24099] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Revised: 11/29/2013] [Accepted: 12/26/2013] [Indexed: 12/11/2022]
Abstract
OBJECTIVE Transected axons of the central nervous system fail to regenerate and instead die back away from the lesion site, resulting in permanent disability. Although both intrinsic (eg, microtubule instability, calpain activation) and extrinsic (ie, macrophages) processes are implicated in axonal dieback, the underlying mechanisms remain uncertain. Furthermore, the precise mechanisms that cause delayed "bystander" loss of spinal axons, that is, ones that were not directly damaged by the initial insult, but succumbed to secondary degeneration, remain unclear. Our goal was to evaluate the role of intra-axonal Ca(2+) stores in secondary axonal degeneration following spinal cord injury. METHODS We developed a 2-photon laser-induced spinal cord injury model to follow morphological and Ca(2+) changes in live myelinated spinal axons acutely following injury. RESULTS Transected axons "died back" within swollen myelin or underwent synchronous pan-fragmentation associated with robust Ca(2+) increases. Spared fibers underwent delayed secondary bystander degeneration. Reducing Ca(2+) release from axonal stores mediated by ryanodine and inositol triphosphate receptors significantly decreased axonal dieback and bystander injury. Conversely, a gain-of-function ryanodine receptor 2 mutant or pharmacological treatments that promote axonal store Ca(2+) release worsened these events. INTERPRETATION Ca(2+) release from intra-axonal Ca(2+) stores, distributed along the length of the axon, contributes significantly to secondary degeneration of axons. This refocuses our approach to protecting spinal white matter tracts, where emphasis has been placed on limiting Ca(2+) entry from the extracellular space across cell membranes, and emphasizes that modulation of axonal Ca(2+) stores may be a key pharmacotherapeutic goal in spinal cord injury.
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Affiliation(s)
- David P Stirling
- Department of Clinical Neurosciences, Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada; Kentucky Spinal Cord Injury Research Center and Departments of Neurological Surgery, Microbiology and Immunology, University of Louisville, Louisville, KY
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Cassidy LL, Dlugos FF, Dlugos CA. Time course of SERCA 2b and calreticulin expression in Purkinje neurons of ethanol-fed rats with behavioral correlates. Alcohol Alcohol 2013; 48:667-78. [PMID: 23884168 PMCID: PMC3799558 DOI: 10.1093/alcalc/agt062] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
UNLABELLED Chronic ethanol consumption for 40 weeks in adult rats results in dilation of the extensive smooth endoplasmic reticulum (SER), a major component of the calcium homeostatic system within Purkinje neuron (PN) dendrites. AIMS The aim of the present study was to determine whether chronic ethanol consumption results in alterations of the sarco/endoplasmic reticulum Ca(2+) ATPase pump (SERCA) on the SER membrane of PN dendrites. The density of calreticulin, a calcium chaperone, was also investigated in the PN along with balancing ability. METHODS Ninety 8-month-old rats were exposed to rat chow, the AIN-93 M liquid control or ethanol diets (30/diet) for a duration of 10, 20 or 40 weeks (30/duration). Age changes relative to the rat chow controls were assessed with 3-month-old control rats (n = 10). Balance was assessed prior to euthanasia. Quantitative immunocytochemistry was used to determine the density of SERCA 2b + dendrites and calreticulin + PN soma and nuclei. Molecular layer volumes were also determined. RESULTS Following 40 weeks of ethanol treatment, there were ethanol-induced decreases in SERCA 2b densities within the dendritic arbor and decreased balancing ability on the more difficult round rod balance test. There were no ethanol-induced changes in calreticulin densities. CONCLUSION It can be concluded that ethanol-induced decreases in the SERCA pump accompany SER dilation and contribute to previously reported ethanol-induced dendritic regression in PN. Ethanol-induced changes in balance also occurred. Chronic ethanol consumption does not alter calreticulin expression in PN.
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Affiliation(s)
- Linda L Cassidy
- Corresponding author: Department of Pathology and Anatomical Sciences, 206 Farber Hall, School of Medicine and Biomedical Sciences, Main Street, Buffalo, NY 14214, USA
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Perni S, Close M, Franzini-Armstrong C. Novel details of calsequestrin gel conformation in situ. J Biol Chem 2013; 288:31358-62. [PMID: 24025332 DOI: 10.1074/jbc.m113.507749] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Calsequestrin (CASQ) is the major component of the sarcoplasmic reticulum (SR) lumen in skeletal and cardiac muscles. This calcium-binding protein localizes to the junctional SR (jSR) cisternae, where it is responsible for the storage of large amounts of Ca(2+), whereas it is usually absent, at least in its polymerized form, in the free SR. The retention of CASQ inside the jSR is due partly to its association with other jSR proteins, such as junctin and triadin, and partly to its ability to polymerize, in a high Ca(2+) environment, into an intricate gel that holds the protein in place. In this work, we shed some light on the still poorly described in situ structure of polymerized CASQ using detailed EM images from thin sections, with and without tilting, and from deep-etched rotary-shadowed replicas. The latter directly illustrate the fundamental network nature of polymerized CASQ, revealing repeated nodal points connecting short segments of the linear polymer.
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Affiliation(s)
- Stefano Perni
- From the Department of Cell Developmental Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6058 and
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11
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Kucharz K, Wieloch T, Toresson H. Fission and Fusion of the Neuronal Endoplasmic Reticulum. Transl Stroke Res 2013; 4:652-62. [DOI: 10.1007/s12975-013-0279-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Accepted: 07/24/2013] [Indexed: 10/26/2022]
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12
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Cox DJ, Racca C. Differential dendritic targeting of AMPA receptor subunit mRNAs in adult rat hippocampal principal neurons and interneurons. J Comp Neurol 2013; 521:1954-2007. [DOI: 10.1002/cne.23292] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2011] [Revised: 12/13/2012] [Accepted: 12/14/2012] [Indexed: 12/19/2022]
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13
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Dekki N, Refai E, Holmberg R, Köhler M, Jörnvall H, Berggren PO, Juntti-Berggren L. Transthyretin binds to glucose-regulated proteins and is subjected to endocytosis by the pancreatic β-cell. Cell Mol Life Sci 2012; 69:1733-43. [PMID: 22183612 PMCID: PMC11114638 DOI: 10.1007/s00018-011-0899-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2010] [Revised: 11/08/2011] [Accepted: 11/28/2011] [Indexed: 12/17/2022]
Abstract
Transthyretin (TTR) is a functional protein in the pancreatic β-cell. It promotes insulin release and protects against β-cell death. We now demonstrate by ligand blotting, adsorption to specific magnetic beads, and surface plasmon resonance that TTR binds to glucose-regulated proteins (Grps)78, 94, and 170, which are members of the endoplasmic reticulum chaperone family, but Grps78 and 94 have also been found at the plasma membrane. The effect of TTR on changes in cytoplasmic free Ca(2+) concentration ([Ca(2+)](i)) was abolished if the cells were treated with either dynasore, a specific inhibitor of dynamin GTPase that blocks clathrin-mediated endocytosis, or an antibody against Grp78, that prevents TTR from binding to Grp78. The conclusion is that TTR binds to Grp78 at the plasma membrane, is internalized into the β-cell via a clathrin-dependent pathway, and that this internalization is necessary for the effects of TTR on β-cell function.
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Affiliation(s)
- Nancy Dekki
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden
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14
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Lynes EM, Simmen T. Urban planning of the endoplasmic reticulum (ER): how diverse mechanisms segregate the many functions of the ER. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2011; 1813:1893-905. [PMID: 21756943 PMCID: PMC7172674 DOI: 10.1016/j.bbamcr.2011.06.011] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Revised: 06/22/2011] [Accepted: 06/23/2011] [Indexed: 12/21/2022]
Abstract
The endoplasmic reticulum (ER) is the biggest organelle in most cell types, but its characterization as an organelle with a continuous membrane belies the fact that the ER is actually an assembly of several, distinct membrane domains that execute diverse functions. Almost 20 years ago, an essay by Sitia and Meldolesi first listed what was known at the time about domain formation within the ER. In the time that has passed since, additional ER domains have been discovered and characterized. These include the mitochondria-associated membrane (MAM), the ER quality control compartment (ERQC), where ER-associated degradation (ERAD) occurs, and the plasma membrane-associated membrane (PAM). Insight has been gained into the separation of nuclear envelope proteins from the remainder of the ER. Research has also shown that the biogenesis of peroxisomes and lipid droplets occurs on specialized membranes of the ER. Several studies have shown the existence of specific marker proteins found on all these domains and how they are targeted there. Moreover, a first set of cytosolic ER-associated sorting proteins, including phosphofurin acidic cluster sorting protein 2 (PACS-2) and Rab32 have been identified. Intra-ER targeting mechanisms appear to be superimposed onto ER retention mechanisms and rely on transmembrane and cytosolic sequences. The crucial roles of ER domain formation for cell physiology are highlighted with the specific targeting of the tumor metastasis regulator gp78 to ERAD-mediating membranes or of the promyelocytic leukemia protein to the MAM.
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Affiliation(s)
- Emily M Lynes
- Department of Cell Biology, University of Alberta, Alberta, Canada
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15
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Kucharz K, Wieloch T, Toresson H. Potassium-induced structural changes of the endoplasmic reticulum in pyramidal neurons in murine organotypic hippocampal slices. J Neurosci Res 2011; 89:1150-9. [PMID: 21538461 DOI: 10.1002/jnr.22646] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2010] [Revised: 02/08/2011] [Accepted: 02/09/2011] [Indexed: 12/15/2022]
Abstract
The endoplasmic reticulum (ER) structure is of central importance for the regulation of cellular anabolism, stress response, and signal transduction. Generally continuous, the ER can temporarily undergo dramatic structural rearrangements resulting in a fragmented appearance. In this study we assess the dynamic nature of ER fission in pyramidal neurons in organotypic hippocampal slice cultures stimulated by depolarizing concentration of potassium (50 mM). The slices were obtained from transgenic mice expressing fluorescent ER-targeted DsRed2 protein. We employed live tissue confocal microscopy imaging with fluorescence recovery after photobleaching (FRAP) to monitor the extent of structural rearrangements of the ER. In control slices, the ER structure was continuous. Potassium stimulation resulted in extensive fragmentation (fission), whereas return to basal potassium levels (2.5 mM) led to ER fusion and normalization of ER structure. This ER fission/fusion could be repeated several times in the same neuron, demonstrating the reversibility of the process. Blockade of the N-methyl-D-aspartate receptor (NMDAR) with the antagonist D-AP5 or removal of extracellular Ca(2+) prevented depolarization-induced ER fission. ER fission is sensitive to temperature, and decreasing temperature from 35°C to 30°C augments fission, implying that the altering of ER continuity may be a protective response against damage. We conclude that events that generate membrane depolarisation in brain tissue lead to the release of endogenous glutamate that may regulate neuronal ER continuity. The rapid and reversible NMDAR-mediated changes in ER structure reflect an adaptive, innate property of the ER for synaptic activation as well as response to tissue stress, injury, and disease.
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Affiliation(s)
- Krzysztof Kucharz
- Laboratory for Experimental Brain Research, Department of Clinical Sciences Lund, Lund University, Lund, Sweden
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Hartmann J, Henning HA, Konnerth A. mGluR1/TRPC3-mediated Synaptic Transmission and Calcium Signaling in Mammalian Central Neurons. Cold Spring Harb Perspect Biol 2011; 3:cshperspect.a006726. [PMID: 21441586 DOI: 10.1101/cshperspect.a006726] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Metabotropic glutamate receptors type 1 (mGluR1s) are required for a normal function of the mammalian brain. They are particularly important for synaptic signaling and plasticity in the cerebellum. Unlike ionotropic glutamate receptors that mediate rapid synaptic transmission, mGluR1s produce in cerebellar Purkinje cells a complex postsynaptic response consisting of two distinct signal components, namely a local dendritic calcium signal and a slow excitatory postsynaptic potential. The basic mechanisms underlying these synaptic responses were clarified in recent years. First, the work of several groups established that the dendritic calcium signal results from IP(3) receptor-mediated calcium release from internal stores. Second, it was recently found that mGluR1-mediated slow excitatory postsynaptic potentials are mediated by the transient receptor potential channel TRPC3. This surprising finding established TRPC3 as a novel postsynaptic channel for glutamatergic synaptic transmission.
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Affiliation(s)
- Jana Hartmann
- Institute of Neuroscience and Center for Integrated Protein Science, Technical University of Munich, Germany.
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17
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Lee H, Choi J, Shin H, Jeon Y, Jeong B, Lee H, Kim J, Choi E, Carp R, Kim Y. Altered expression of type 1 inositol 1,4,5-trisphosphate receptor in the Ngsk Prnp deficient mice. Neuroscience 2010; 167:799-808. [DOI: 10.1016/j.neuroscience.2010.02.052] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2009] [Revised: 02/18/2010] [Accepted: 02/19/2010] [Indexed: 10/19/2022]
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18
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Veiga-da-Cunha M, Tyteca D, Stroobant V, Courtoy PJ, Opperdoes FR, Van Schaftingen E. Molecular identification of NAT8 as the enzyme that acetylates cysteine S-conjugates to mercapturic acids. J Biol Chem 2010; 285:18888-98. [PMID: 20392701 DOI: 10.1074/jbc.m110.110924] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Our goal was to identify the reaction catalyzed by NAT8 (N-acetyltransferase 8), a putative N-acetyltransferase homologous to the enzyme (NAT8L) that produces N-acetylaspartate in brain. The almost exclusive expression of NAT8 in kidney and liver and its predicted association with the endoplasmic reticulum suggested that it was cysteinyl-S-conjugate N-acetyltransferase, the microsomal enzyme that catalyzes the last step of mercapturic acid formation. In agreement, HEK293T extracts of cells overexpressing NAT8 catalyzed the N-acetylation of S-benzyl-L-cysteine and leukotriene E(4), two cysteine conjugates, but were inactive on other physiological amines or amino acids. Confocal microscopy indicated that NAT8 was associated with the endoplasmic reticulum. Neither of the two frequent single nucleotide polymorphisms found in NAT8, E104K nor F143S, changed the enzymatic activity or the expression of the protein by >or=2-fold, whereas a mutation (R149K) replacing an extremely conserved arginine suppressed the activity. Sequencing of genomic DNA and EST clones corresponding to the NAT8B gene, which resulted from duplication of the NAT8 gene in the primate lineage, disclosed the systematic presence of a premature stop codon at codon 16. Furthermore, truncated NAT8B and NAT8 proteins starting from the following methionine (Met-25) showed no cysteinyl-S-conjugate N-acetyltransferase activity when transfected in HEK293T cells. Taken together, these findings indicate that NAT8 is involved in mercapturic acid formation and confirm that NAT8B is an inactive gene in humans. NAT8 homologues are found in all vertebrate genomes, where they are often encoded by multiple, tandemly repeated genes as many other genes encoding xenobiotic metabolism enzymes.
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Affiliation(s)
- Maria Veiga-da-Cunha
- Laboratory of Physiological Chemistry, de Duve Institute and Université Catholique de Louvain, Avenue Hippocrate 75, B-1200 Brussels, Belgium.
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19
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Molecular identification of aspartate N-acetyltransferase and its mutation in hypoacetylaspartia. Biochem J 2009; 425:127-36. [PMID: 19807691 DOI: 10.1042/bj20091024] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The brain-specific compound NAA (N-acetylaspartate) occurs almost exclusively in neurons, where its concentration reaches approx. 20 mM. Its abundance is determined in patients by MRS (magnetic resonance spectroscopy) to assess neuronal density and health. The molecular identity of the NAT (N-acetyltransferase) that catalyses NAA synthesis has remained unknown, because the enzyme is membrane-bound and difficult to purify. Database searches indicated that among putative NATs (i.e. proteins homologous with known NATs, but with uncharacterized catalytic activity) encoded by the human and mouse genomes two were almost exclusively expressed in brain, NAT8L and NAT14. Transfection studies in HEK-293T [human embryonic kidney-293 cells expressing the large T-antigen of SV40 (simian virus 40)] indicated that NAT8L, but not NAT14, catalysed the synthesis of NAA from L-aspartate and acetyl-CoA. The specificity of NAT8L, its Km for aspartate and its sensitivity to detergents are similar to those described for brain Asp-NAT. Confocal microscopy analysis of CHO (Chinese-hamster ovary) cells and neurons expressing recombinant NAT8L indicates that it is associated with the ER (endoplasmic reticulum), but not with mitochondria. A mutation search in the NAT8L gene of the only patient known to be deficient in NAA disclosed the presence of a homozygous 19 bp deletion, resulting in a change in reading frame and the absence of production of a functional protein. We conclude that NAT8L, a neuron-specific protein, is responsible for NAA synthesis and is mutated in primary NAA deficiency (hypoacetylaspartia). The molecular identification of this enzyme will lead to new perspectives in the clarification of the function of this most abundant amino acid derivative in neurons and for the diagnosis of hypoacetylaspartia in other patients.
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20
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Hartmann J, Konnerth A. Mechanisms of metabotropic glutamate receptor-mediated synaptic signalling in cerebellar Purkinje cells. Acta Physiol (Oxf) 2009. [DOI: 10.1111/j.1748-1716.2008.01923.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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21
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Rizzuto R, Pozzan T. Microdomains of intracellular Ca2+: molecular determinants and functional consequences. Physiol Rev 2006; 86:369-408. [PMID: 16371601 DOI: 10.1152/physrev.00004.2005] [Citation(s) in RCA: 876] [Impact Index Per Article: 48.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Calcium ions are ubiquitous and versatile signaling molecules, capable of decoding a variety of extracellular stimuli (hormones, neurotransmitters, growth factors, etc.) into markedly different intracellular actions, ranging from contraction to secretion, from proliferation to cell death. The key to this pleiotropic role is the complex spatiotemporal organization of the [Ca(2+)] rise evoked by extracellular agonists, which allows selected effectors to be recruited and specific actions to be initiated. In this review, we discuss the structural and functional bases that generate the subcellular heterogeneity in cellular Ca(2+) levels at rest and under stimulation. This complex choreography requires the concerted action of many different players; the central role is, of course, that of the calcium ion, with the main supporting characters being all the entities responsible for moving Ca(2+) between different compartments, while the cellular architecture provides a determining framework within which all the players have their exits and their entrances. In particular, we concentrate on the molecular mechanisms that lead to the generation of cytoplasmic Ca(2+) microdomains, focusing on their different subcellular location, mechanism of generation, and functional role.
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Affiliation(s)
- Rosario Rizzuto
- Department of Experimental and Diagnostic Medicine, and Interdisciplinary Center for the Study of Inflammation, University of Ferrara, Ferrara, Italy
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22
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Ginzburg L, Futerman AH. Defective calcium homeostasis in the cerebellum in a mouse model of Niemann-Pick A disease. J Neurochem 2005; 95:1619-28. [PMID: 16277603 DOI: 10.1111/j.1471-4159.2005.03534.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We recently demonstrated that calcium homeostasis is altered in mouse models of two sphingolipid storage diseases, Gaucher and Sandhoff diseases, owing to modulation of the activities of a calcium-release channel (the ryanodine receptor) and of the sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) respectively, by the accumulating sphingolipids. We now demonstrate that calcium homeostasis is also altered in a mouse model of Niemann-Pick A disease, the acid sphingomyelinase (A-SMase)-deficient mouse (ASM-/-), with reduced rates of calcium uptake via SERCA in the cerebellum of 6-7-month-old mice. However, the mechanism responsible for defective calcium homeostasis is completely different from that observed in the other two disease models. Thus, levels of SERCA expression are significantly reduced in the ASM-/- cerebellum by 6-7 months of age, immediately before death of the mice, as are levels of the inositol 1,4,5-triphosphate receptor (IP3R), the major calcium-release channel in the cerebellum. Systematic analyses of the time course of loss of SERCA and IP3R expression revealed that loss of the IP3R preceeded that of SERCA, with essentially no IP3R remaining by 4 months of age, whereas SERCA was still present even after 6 months. Expression of zebrin II (aldolase C), a protein found in about half of the Purkinje cells in the adult mouse cerebellum, was essentially unchanged during development. We discuss possible pathological mechanisms related to calcium dysfunction that may cause Purkinje cell degeneration, and as a result, the onset of neuropathology in Niemann-Pick A disease.
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Affiliation(s)
- Luba Ginzburg
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, Israel
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23
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Rong Y, Wang T, Morgan JI. Identification of candidate Purkinje cell-specific markers by gene expression profiling in wild-type and pcd(3J) mice. ACTA ACUST UNITED AC 2005; 132:128-45. [PMID: 15582153 DOI: 10.1016/j.molbrainres.2004.10.015] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/07/2004] [Indexed: 10/26/2022]
Abstract
The identification of mRNAs that have restricted expression patterns in the brain represents powerful tools with which to characterize and manipulate the nervous system. Here, we describe a strategy using microarray technology (Affymetrix Mouse Genome 430 2.0 Arrays) to identify mRNA transcripts that are candidate markers of cerebellar Purkinje neurons. Initially, gene expression profiles were compared between cerebella of 4-month-old Purkinje cell degeneration (pcd(3J)) mice, in which most Purkinje cells had already degenerated and wild-type littermates with a normal complement of Purkinje neurons. Of 14,563 probe sets expressed in wild-type cerebellum, 797 showed a significant (p<0.0001) reduction in pcd(3J) mice. These probes could represent transcripts with varying levels of specificity for Purkinje cells as well as transcripts in other cell types that decline as a secondary consequence of Purkinje cell loss. Ranking of the probe signals revealed that well-known Purkinje cell-specific transcripts such as calbindin and L7/pcp2 clustered in a group that was <33% of wild-type levels. Therefore, to identify potentially new Purkinje cell-specific transcripts that cluster with the known markers, more stringent selection criteria were applied (<33% of wild-type signal and p<0.0001). With these criteria, 55 independent transcripts were identified of which 33 were annotated genes and 22 were ESTs and RIKEN cDNAs. A literature search revealed that 25 of the 33 annotated genes were expressed in Purkinje cells, with no data being available on the other 8. Thus, the additional 8 annotated and 22 un-annotated genes are clustered with many genes expressed in Purkinje cells making them candidate markers. To confirm the microarray data, eight representative annotated genes were selected including five reported to be in Purkinje neurons and three for which no data was available. Semi-quantitative RT-PCR demonstrated reduced expression of all eight transcripts in cerebella from pcd(3J) mice. The promoters of genes expressed selectively in subsets of neurons can be used to direct heterologous gene expression in transgenic mice and the more restricted the expression pattern the greater their utility. Therefore, microarray analysis was used to assess expression levels of all 55 transcripts in cerebral cortex, striatum, substantia nigra and ventral tegmental area. This permitted the identification of a set of genes whose promoters might have utility for selectively targeting gene expression to cerebellar Purkinje cells.
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Affiliation(s)
- Yongqi Rong
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, 332 N. Lauderdale Street, Memphis, TN 38105, United States
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Beard NA, Laver DR, Dulhunty AF. Calsequestrin and the calcium release channel of skeletal and cardiac muscle. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2004; 85:33-69. [PMID: 15050380 DOI: 10.1016/j.pbiomolbio.2003.07.001] [Citation(s) in RCA: 201] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Calsequestrin is by far the most abundant Ca(2+)-binding protein in the sarcoplasmic reticulum (SR) of skeletal and cardiac muscle. It allows the Ca2+ required for contraction to be stored at total concentrations of up to 20mM, while the free Ca2+ concentration remains at approximately 1mM. This storage capacity confers upon muscle the ability to contract frequently with minimal run-down in tension. Calsequestrin is highly acidic, containing up to 50 Ca(2+)-binding sites, which are formed simply by clustering of two or more acidic residues. The Kd for Ca2+ binding is between 1 and 100 microM, depending on the isoform, species and the presence of other cations. Calsequestrin monomers have a molecular mass of approximately 40 kDa and contain approximately 400 residues. The monomer contains three domains each with a compact alpha-helical/beta-sheet thioredoxin fold which is stable in the presence of Ca2+. The protein polymerises when Ca2+ concentrations approach 1mM. The polymer is anchored at one end to ryanodine receptor (RyR) Ca2+ release channels either via the intrinsic membrane proteins triadin and junctin or by binding directly to the RyR. It is becoming clear that calsequestrin has several functions in the lumen of the SR in addition to its well-recognised role as a Ca2+ buffer. Firstly, it is a luminal regulator of RyR activity. When triadin and junctin are present, calsequestrin maximally inhibits the Ca2+ release channel when the free Ca2+ concentration in the SR lumen is 1mM. The inhibition is relieved when the Ca2+ concentration alters, either because of small changes in the conformation of calsequestrin or its dissociation from the junctional face membrane. These changes in calsequestrin's association with the RyR amplify the direct effects of luminal Ca2+ concentration on RyR activity. In addition, calsequestrin activates purified RyRs lacking triadin and junctin. Further roles for calsequestrin are indicated by the kinase activity of the protein, its thioredoxin-like structure and its influence over store operated Ca2+ entry. Clearly, calsequestrin plays a major role in calcium homeostasis that extends well beyond its ability to buffer Ca2+ ions.
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Affiliation(s)
- N A Beard
- John Curtin School of Medical Research, Australian National University, PO Box 334, Canberra 2601, Australia
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25
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González B, Manso R. Induction, modification and accumulation of HSP70s in the rat liver after acute exercise: early and late responses. J Physiol 2004; 556:369-85. [PMID: 14754995 PMCID: PMC1664938 DOI: 10.1113/jphysiol.2003.058420] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Liver cells synthesize HSP72, the cytosolic highly stress-inducible member of the 70 kDa family of heat-shock proteins (HSP70s), in response to acute exercise. This study was aimed at obtaining further insight into the physiological relevance of the hepatic stress response to exercise by investigating the induction and long-term maintenance of increased levels of HSP70s of the HSP and glucose-regulated protein (GRP) families, their post-translational modifications during or after exercise and the possible relation of HSP induction to oxidative stress. In a running rat model, acute exercise activated the synthesis and accumulation of HSP72, GRP75 and GRP78 in liver cells, pointing towards a multifactorial origin of this response. A peak HSP72 accumulation was observed shortly after exercise as a result of transcriptional activation. HSP72 was reduced shortly after exercise preceding the disappearance of its mRNA. Two further waves of HSP72 accumulation peaked 8 and 48 h after exercise without transcriptional activation. A transient increase in the proportion of acidic variants of HSP72 and HSP73 was also observed shortly after exercise as a result, at least in part, of protein phosphorylation. Free and protein-bound lipid peroxidation derivatives (TBARS) showed a tendency to increase in the early post-exercise and the free-to-protein-bound TBARS ratio decreased significantly after 2 h. During the early post-exercise period, protein-bound TBARS correlated positively with HSP72 and 73, but not with GRP75 or GRP78. Altogether, the reported results indicate that the early induction and post-translational modification of HSP70s in liver cells following exercise is a preliminary step of a series of long-lasting HSP70-related events, possibly designed to preserve liver cell homeostasis and to help provide a concerted response of the whole organism to physical stress.
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Affiliation(s)
- Beatriz González
- Centro de Biología Molecular 'Severo Ochoa' (CSIC-UAM), Universidad Autónoma de Madrid, E-28049 Cantoblanco, Madrid, Spain.
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26
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Bannai H, Inoue T, Nakayama T, Hattori M, Mikoshiba K. Kinesin dependent, rapid, bi-directional transport of ER sub-compartment in dendrites of hippocampal neurons. J Cell Sci 2004; 117:163-75. [PMID: 14676272 DOI: 10.1242/jcs.00854] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Although spatially restricted Ca2+ release from the endoplasmic reticulum (ER) through intracellular Ca2+ channels plays important roles in various neuronal activities, the accurate distribution and dynamics of ER in the dendrite of living neurons still remain unknown. To elucidate these, we expressed fluorescent protein-tagged ER proteins in cultured mouse hippocampal neurons, and monitored their movements using time-lapse microscopy. We report here that a sub-compartment of ER forms in relatively large vesicles that are capable, similarly to the reticular ER, of taking up and releasing Ca2+. The vesicular sub-compartment of ER moved rapidly along the dendrites in both anterograde and retrograde directions at a velocity of 0.2-0.3 μm/second. Depletion of microtubules, overexpression of dominant-negative kinesin and kinesin depletion by antisense DNA reduced the number and velocity of the moving vesicles, suggesting that kinesin may drive the transport of the vesicular sub-compartment of ER along microtubules in the dendrite. Rapid transport of the Ca2+-releasable sub-compartment of ER might contribute to rapid supply of fresh ER proteins to the distal part of the dendrite, or to the spatial regulation of intracellular Ca2+ signaling.
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Affiliation(s)
- Hiroko Bannai
- Laboratory for Developmental Neurobiology, Brain Science Institute, RIKEN, Saitama 351-0198, Japan
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27
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Ying M, Sannerud R, Flatmark T, Saraste J. Colocalization of Ca2+-ATPase and GRP94 with p58 and the effects of thapsigargin on protein recycling suggest the participation of the pre-Golgi intermediate compartment in intracellular Ca2+ storage. Eur J Cell Biol 2002; 81:469-83. [PMID: 12416724 DOI: 10.1078/0171-9335-00266] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
We have studied the localization of functional components of cellular Ca2+ transport and storage and the effects of thapsigargin (TG), a specific inhibitor of the sarco-endoplasmic reticulum Ca2+-ATPase (SERCA), with respect to the p58-containing pre-Golgi intermediate compartment (IC). The depletion of Ca2+ stores in normal rat kidney (NRK) cells by TG abolished the retention of the KDEL-containing, Ca2+-binding, luminal ER chaperones GRP94/endoplasmin and GRP78/BiP, and resulted in the appearance of the proteins in the culture medium before inducing their synthesis. Immunolocalization of GRP94 in TG-treated cells showed that the protein was transported to the Golgi complex and, in parallel, the KDEL receptor was redistributed from the Golgi to p58-positive IC structures, but was not transported further to the ER. Similarly, p58 that normally cycles between the ER, IC, and cis-Golgi, was largely depleted from the cell periphery and arrested in large-sized IC elements and numerous vesicles or buds in the Golgi region, showing that TG selectively blocks its recycling from the IC back to the ER. Importantly, cell fractionation analyses and confocal fluorescence microscopy provided evidence that the IC elements in unperturbed cells contain SERCA and a considerable pool of GRP94. Thus, the observed effects of TG on protein retention and recycling can be explained by a change in the luminal Ca2+ concentration of the IC. Moreover, the compositional properties of the IC elements suggest that they participate in intracellular Ca2+ storage.
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Affiliation(s)
- Ming Ying
- Department of Biochemistry and Molecular Biology, University of Bergen, Norway
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28
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Antonucci DE, Lim ST, Vassanelli S, Trimmer JS. Dynamic localization and clustering of dendritic Kv2.1 voltage-dependent potassium channels in developing hippocampal neurons. Neuroscience 2002; 108:69-81. [PMID: 11738132 DOI: 10.1016/s0306-4522(01)00476-6] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Dendritic excitability is modulated by the highly variable spatial and temporal expression pattern of voltage-dependent potassium channels. Somatodendritic Kv2.1 channels contribute a major component of delayed rectifier potassium current in cultured hippocampal neurons, where Kv2.1 is localized to large clusters on the soma and proximal dendrites. Here we found that dramatic differences exist in the clustering of endogenous Kv2.1 in cultured rat hippocampal GABAergic interneurons and glutamatergic pyramidal neurons. Studies on neurons developing in culture revealed that while a similar sequence of Kv2.1 localization and clustering occurred in both cell types, the process was temporally delayed in pyramidal cells. Localization and clustering of recombinant green fluorescent protein-tagged Kv2.1 occurred by the same sequence of events, and imaging of GFP-Kv2.1 clustering in living neurons revealed dynamic fusion events that underlie cluster formation. Overexpression of GFP-Kv2.1 accelerated the clustering program in pyramidal neurons such that the observed differences in Kv2.1 clustering in pyramidal neurons and interneurons were eliminated. Confocal imaging showed a preferential association of Kv2.1 with the basal membrane in cultured neurons, and electrophysiological recordings from neurons cultured on transistors revealed that Kv2.1 contributed the bulk of a previously described adherens junction delayed rectifier potassium conductance. Finally, Kv2.1 clusters were found spatially associated with ryanodine receptor intracellular Ca(2+) ([Ca(2+)](i)) release channels. These findings reveal a stepwise assembly of Kv2.1 potassium channels into membrane clusters during development, and an association of these clusters with Ca(2+) signaling apparatus. Together these data suggest that the restricted localization of Kv2.1 may play an important role in the previously observed contribution of this potassium channel in regulating dendritic [Ca(2+)](i) transients.
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Affiliation(s)
- D E Antonucci
- Department of Biochemistry, State University of New York at Stony Brook, 11794-5215, USA
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29
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Baumann O, Walz B. Endoplasmic reticulum of animal cells and its organization into structural and functional domains. INTERNATIONAL REVIEW OF CYTOLOGY 2001; 205:149-214. [PMID: 11336391 DOI: 10.1016/s0074-7696(01)05004-5] [Citation(s) in RCA: 335] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/07/2022]
Abstract
The endoplasmic reticulum (ER) in animal cells is an extensive, morphologically continuous network of membrane tubules and flattened cisternae. The ER is a multifunctional organelle; the synthesis of membrane lipids, membrane and secretory proteins, and the regulation of intracellular calcium are prominent among its array of functions. Many of these functions are not homogeneously distributed throughout the ER but rather are confined to distinct ER subregions or domains. This review describes the structural and functional organization of the ER and highlights the dynamic properties of the ER network and the mechanisms that support the positioning of ER membranes within the cell. Furthermore, we outline processes involved in the establishment and maintenance of an anisotropic distribution of ER-resident proteins and, thus, in the organization of the ER into functionally and morphologically different subregions.
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Affiliation(s)
- O Baumann
- Institut für Biochemie und Biologie, Zoophysiologie, Universität Potsdam, Germany
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30
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Blaustein MP, Golovina VA. Structural complexity and functional diversity of endoplasmic reticulum Ca(2+) stores. Trends Neurosci 2001; 24:602-8. [PMID: 11576675 DOI: 10.1016/s0166-2236(00)01891-9] [Citation(s) in RCA: 140] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Considerable evidence, including recent direct observations, suggest that endoplasmic reticulum (ER) Ca(2+) stores in neurons, glia, and other cell types, consists of spatially-distinct compartments that can be individually loaded and unloaded. In addition, sub-plasmalemmal ('junctional') components of the ER (jER) are functionally coupled to the overlying plasmalemmal (PL) microdomains in PL-jER units named 'PLasmERosomes'. The PL microdomains and the jER contain clusters of specific transport proteins that regulate Na(+) and Ca(2+) concentrations in the tiny cytosolic space between the PL and jER. This organization helps the ER to produce the many types of complex local and global Ca(2+) signals that are responsible for the simultaneous control of numerous neuronal and glial functions.
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Affiliation(s)
- M P Blaustein
- Department of Physiology, University of Maryland School of Medicine, 655 W. Baltimore Street, Baltimore, MD 21201, USA.
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31
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Meldolesi J. Rapidly exchanging Ca2+ stores in neurons: molecular, structural and functional properties. Prog Neurobiol 2001; 65:309-38. [PMID: 11473791 DOI: 10.1016/s0301-0082(01)00004-1] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- J Meldolesi
- DIBIT, Scientific Institute S. Raffaele, Vita-Salute University, Via Olgettina, 58, 20132, Milan, Italy.
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32
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Gardiol A, Racca C, Triller A. RNA transport and local protein synthesis in the dendritic compartment. Results Probl Cell Differ 2001; 34:105-28. [PMID: 11288671 DOI: 10.1007/978-3-540-40025-7_7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Affiliation(s)
- A Gardiol
- Laboratoire de Biologie Cellulaire de la Synapse N&P INSERM U497 Ecole Normale Supérieure, 46 rue d'Ulm, 75005 Paris, France
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Gatti G, Trifari S, Mesaeli N, Parker JM, Michalak M, Meldolesi J. Head-to-tail oligomerization of calsequestrin: a novel mechanism for heterogeneous distribution of endoplasmic reticulum luminal proteins. J Cell Biol 2001; 154:525-34. [PMID: 11489915 PMCID: PMC2196414 DOI: 10.1083/jcb.200103002] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Many proteins retained within the endo/sarcoplasmic reticulum (ER/SR) lumen express the COOH-terminal tetrapeptide KDEL, by which they continuously recycle from the Golgi complex; however, others do not express the KDEL retrieval signal. Among the latter is calsequestrin (CSQ), the major Ca2+-binding protein condensed within both the terminal cisternae of striated muscle SR and the ER vacuolar domains of some neurons and smooth muscles. To reveal the mechanisms of condensation and establish whether it also accounts for ER/SR retention of CSQ, we generated a variety of constructs: chimeras with another similar protein, calreticulin (CRT); mutants truncated of COOH- or NH2-terminal domains; and other mutants deleted or point mutated at strategic sites. By transfection in L6 myoblasts and HeLa cells we show here that CSQ condensation in ER-derived vacuoles requires two amino acid sequences, one at the NH2 terminus, the other near the COOH terminus. Experiments with a green fluorescent protein GFP/CSQ chimera demonstrate that the CSQ-rich vacuoles are long-lived organelles, unaffected by Ca2+ depletion, whose almost complete lack of movement may depend on a direct interaction with the ER. CSQ retention within the ER can be dissociated from condensation, the first identified process by which ER luminal proteins assume a heterogeneous distribution. A model is proposed to explain this new process, that might also be valid for other luminal proteins.
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Affiliation(s)
- G Gatti
- Department of Pharmacology, University of Milan, 20129 Milan, Italy
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Petersen OH, Tepikin A, Park MK. The endoplasmic reticulum: one continuous or several separate Ca(2+) stores? Trends Neurosci 2001; 24:271-6. [PMID: 11311379 DOI: 10.1016/s0166-2236(00)01787-2] [Citation(s) in RCA: 123] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The Ca2+ store and sink in the endoplasmic reticulum (ER) is important for Ca2+ signal integration and for conveyance of information in spatial and temporal domains. Textbooks regard the ER as one continuous network, but biochemical and biophysical studies revealed apparently discrete ER Ca2+ stores. Recent direct studies of ER lumenal Ca2+ movements show that this organelle system is one continuous Ca2+ store, which can function as a Ca2+ tunnel. The concept of a fully connected ER network is entirely compatible with evidence indicating that the distribution of Ca2+ -release channels in the ER membrane is discontinuous with clustering in certain localities.
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Affiliation(s)
- O H Petersen
- The MRC Secretory Control Research Group, The Physiological Laboratory, University of Liverpool, Liverpool, UK, L69 3BX.
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35
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Rosenberg LJ, Emery DG, Lucas JH. Effects of sodium and chloride on neuronal survival after neurite transection. J Neuropathol Exp Neurol 2001; 60:33-48. [PMID: 11202174 DOI: 10.1093/jnen/60.1.33] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
An in vitro investigation was undertaken to study the roles of Na+ and Cl- in mammalian spinal cord (SC) neuron deterioration and death after injury involving physical disruption of the plasma membrane. Individual SC neurons in monolayer cultures were subjected to UV laser microbeam transection of a primary dendrite. Neurons lesioned in modified ionic environments (MIEs) where 50%-75% of the NaCl was replaced with sucrose had higher survival (65%-75%) than neurons lesioned in medium with normal (125 mM) NaCl (28%; p < 0.001). Subsequent experiments found a comparable increase in lesioned neuron survival in MIEs in which only Na+ was replaced with specific ionic substitutes; however, replacement of Cl- was not protective. Electron microscope examinations of neurons fixed <16 min after lesioning showed a dramatic decrease in vesiculation of the smooth endoplasmic reticulum and Golgi apparatus in the low NaCl or low Na+ MIEs. It is hypothesized that Na+ entry after membrane disruption may stimulate elevation of [Ca+2]i leading to ultrastructural disruption and death of injured neurons. The results of these studies suggest that a low NaCl MIE may be useful as an irrigant to limit damage spread and cell death within CNS tissues during surgery or after trauma.
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Affiliation(s)
- L J Rosenberg
- Department of Neuroscience, Georgetown University, Washington, DC, USA
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Park MK, Petersen OH, Tepikin AV. The endoplasmic reticulum as one continuous Ca(2+) pool: visualization of rapid Ca(2+) movements and equilibration. EMBO J 2000; 19:5729-39. [PMID: 11060024 PMCID: PMC305795 DOI: 10.1093/emboj/19.21.5729] [Citation(s) in RCA: 187] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We investigated whether the endoplasmic reticulum (ER) is a functionally connected Ca(2+) store or is composed of separate subunits by monitoring movements of Ca(2+) and small fluorescent probes in the ER lumen of pancreatic acinar cells, using confocal microscopy, local bleaching and uncaging. We observed rapid movements and equilibration of Ca(2+) and the probes. The bulk of the ER at the base was not connected to the granules in the apical part, but diffusion into small apical ER extensions occurred. The connectivity of the ER Ca(2+) store was robust, since even supramaximal acetylcholine (ACh) stimulation for 30 min did not result in functional fragmentation. ACh could elicit a uniform decrease in the ER Ca(2+) concentration throughout the cell, but repetitive cytosolic Ca(2+) spikes, induced by a low ACh concentration, hardly reduced the ER Ca(2+) level. We conclude that the ER is a functionally continuous unit, which enables efficient Ca(2+) liberation. Ca(2+) released from the apical ER terminals is quickly replenished from the bulk of the rough ER at the base.
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Affiliation(s)
- M K Park
- MRC Secretory Control Research Group, The Physiological Laboratory, University of Liverpool, Crown Street, PO Box 147, Liverpool L69 3BX, UK
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Baumann O. Association of spectrin with a subcompartment of the endoplasmic reticulum in honeybee photoreceptor cells. CELL MOTILITY AND THE CYTOSKELETON 2000; 41:74-86. [PMID: 9744301 DOI: 10.1002/(sici)1097-0169(1998)41:1<74::aid-cm7>3.0.co;2-f] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The endoplasmic reticulum (ER) in honeybee photoreceptors is organized into structurally distinct subregions. The most prominent of these, the submicrovillar network of ER cisternae, is tightly associated with actin filaments. Electron microscopic techniques have demonstrated that the ER-associated actin filaments are regularly spaced at 60-80 nm and cross-bridged by filamentous structures. A polyclonal antibody against Drosophila alpha-spectrin has been used to examine the distribution of spectrin in the photoreceptors. On Western blots of bee retina, the antibody identifies a 260-kDa protein that exhibits biochemical and immunological properties characteristic of alpha-spectrin. Immunofluorescence microscopy has shown that alpha-spectrin codistributes with the submicrovillar ER but not with other ER subdomains. After cytochalasin-B-induced depolymerization of the ER-associated F-actin system, alpha-spectrin remains colocalized with the ER, indicating that alpha-spectrin is bound to the ER membrane. The F-actin/spectrin system associated with the submicrovillar ER may stabilize the shape of this ER subcompartment and may play a role in maintaining functional ER subregions.
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Affiliation(s)
- O Baumann
- Institut für Zoophysiologie und Zellbiologie, Universität Potsdam, Germany.
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38
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Abstract
The peptide sequence of autocrine motility factor (AMF), a tumor secreted cytokine that induces cell motility, corresponds to that of the previously identified cytokine/enzyme, neuroleukin/glucose-6-phosphate isomerase. Neuroleukin is a neurotrophic factor that promotes neuronal survival and sprouting at the neuromuscular junction. The AMF receptor (AMF-R) has been identified and shown to be highly expressed in malignant tumors with minimal expression in adjacent normal tissue. Neuroleukin mRNA is highly expressed in the cerebellum and we therefore undertook a developmental study of AMF-R expression in rat cerebellum. As determined by immunoblot, AMF-R is expressed at equivalent high levels in brain and cerebellum of postnatal day 5 (P5) and 12 (P12) rats and at significantly reduced levels in the adult. Coimmunofluorescence studies with MAP-2 and gamma-actin revealed that at P12, AMF-R was mainly localized to Purkinje and granule cells. Moreover, the premigratory cells of the external granular layer were also immunoreactive for AMF-R suggesting a role for AMF-R in granule cell migration during cerebellar development in the first two weeks after birth. In the adult, AMF-R distribution was similar to P12, although weaker, and was localized to Purkinje and granule cells. AMF-R labeling of GFAP positive glial processes could not be detected in cerebellar sections although in cerebellar primary cultures, both neurons and glial cells were labeled for AMF-R. In neurons, AMF-R labeling was present in the cell body, neurites and growth cones. These data indicate that regulation of the neurotrophic function of neuroleukin might be regulated spatially and temporally by expression of its receptor, AMF-R, in developing and adult cerebellum.
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Affiliation(s)
- N Leclerc
- Département de pathologie et biologie cellulaire, Université de Montréal, Québec, Canada
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Cancela JM, Gerasimenko OV, Gerasimenko JV, Tepikin AV, Petersen OH. Two different but converging messenger pathways to intracellular Ca(2+) release: the roles of nicotinic acid adenine dinucleotide phosphate, cyclic ADP-ribose and inositol trisphosphate. EMBO J 2000; 19:2549-57. [PMID: 10835353 PMCID: PMC212763 DOI: 10.1093/emboj/19.11.2549] [Citation(s) in RCA: 159] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Hormones and neurotransmitters mobilize Ca(2+) from the endoplasmic reticulum via inositol trisphosphate (IP(3)) receptors, but how a single target cell encodes different extracellular signals to generate specific cytosolic Ca(2+) responses is unknown. In pancreatic acinar cells, acetylcholine evokes local Ca(2+) spiking in the apical granular pole, whereas cholecystokinin elicits a mixture of local and global cytosolic Ca(2+) signals. We show that IP(3), cyclic ADP-ribose and nicotinic acid adenine dinucleotide phosphate (NAADP) evoke cytosolic Ca(2+) spiking by activating common oscillator units composed of IP(3) and ryanodine receptors. Acetylcholine activation of these common oscillator units is triggered via IP(3) receptors, whereas cholecystokinin responses are triggered via a different but converging pathway with NAADP and cyclic ADP-ribose receptors. Cholecystokinin potentiates the response to acetylcholine, making it global rather than local, an effect mediated specifically by cyclic ADP-ribose receptors. In the apical pole there is a common early activation site for Ca(2+) release, indicating that the three types of Ca(2+) release channels are clustered together and that the appropriate receptors are selected at the earliest step of signal generation.
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Affiliation(s)
- J M Cancela
- MRC Secretory Control Research Group, The Physiological Laboratory, University of Liverpool, Liverpool L69 3BX, UK
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40
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Abstract
The purpose of this study was to determine whether the observed swelling of smooth endoplasmic reticulum (SER) profiles in Purkinje dendrites in our old ethanol-fed F344 rats: (1) represented measurable dilatation, (2) was present in dendritic shafts and spines, and (3) was reversed following recovery from ethanol. Of the 45 rats in 3 treatment groups (chow-fed, pair-fed, and ethanol-fed), 30 rats were euthanized after 40 weeks, and 15 were maintained on rat chow for an additional 20-week recovery period. Electron microscopy of cerebellar preparations was used to analyze morphological alterations in SER profile size within the dendritic shafts and spines of Purkinje neurons. Results showed significant SER dilatation following 40 weeks of ethanol consumption, which disappeared after ethanol withdrawal.
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Affiliation(s)
- C A Dlugos
- Department of Anatomy and Cell Biology, School of Medicine and Biomedical Sciences, State University of New York at Buffialo, 14214-3000, USA.
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41
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Michalak M, Corbett EF, Mesaeli N, Nakamura K, Opas M. Calreticulin: one protein, one gene, many functions. Biochem J 1999. [PMID: 10567207 DOI: 10.1042/0264-6021:3440281] [Citation(s) in RCA: 147] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The endoplasmic reticulum (ER) plays a critical role in the synthesis and chaperoning of membrane-associated and secreted proteins. The membrane is also an important site of Ca(2+) storage and release. Calreticulin is a unique ER luminal resident protein. The protein affects many cellular functions, both in the ER lumen and outside of the ER environment. In the ER lumen, calreticulin performs two major functions: chaperoning and regulation of Ca(2+) homoeostasis. Calreticulin is a highly versatile lectin-like chaperone, and it participates during the synthesis of a variety of molecules, including ion channels, surface receptors, integrins and transporters. The protein also affects intracellular Ca(2+) homoeostasis by modulation of ER Ca(2+) storage and transport. Studies on the cell biology of calreticulin revealed that the ER membrane is a very dynamic intracellular compartment affecting many aspects of cell physiology.
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Affiliation(s)
- M Michalak
- MRC Group in Molecular Biology of Membranes, Department of Biochemistry, University of Alberta, 3-56 Medical Sciences Building, Edmonton, Alberta, Canada T6G 2H7.
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42
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van De Water B, Wang Y, Asmellash S, Liu H, Zhan Y, Miller E, Stevens JL. Distinct endoplasmic reticulum signaling pathways regulate apoptotic and necrotic cell death following iodoacetamide treatment. Chem Res Toxicol 1999; 12:943-51. [PMID: 10525270 DOI: 10.1021/tx990054q] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Environmental stress induces the synthesis of glucose-regulated proteins (Grps) in the endoplasmic reticulum (ER) and heat shock proteins (Hsps) in the cytoplasm. Iodoacetamide (IDAM), a prototypical alkyating agent, induces both Grp and Hsp synthesis in renal epithelial cells and causes necrosis which is prevented by prior activation of the ER stress response (pre-ER stress) [Liu, H., et al. (1997) J. Biol. Chem. 272, 21751-21759]. In this study, we examined the biochemical pathways leading to IDAM-induced apoptosis and investigated the role of the ER stress response in apoptotic cell death. The antioxidant N,N'-diphenyl-p-phenylenediamine (DPPD) prevented necrosis after IDAM treatment, but the cells went on to die with hallmarks of apoptosis, i.e., cell detachment, caspase-3 activation, cleavage of poly(ADP-ribose)polymerase (PARP), and DNA-ladder formation, all of which were blocked by the general caspase inhibitor zVAD. As with IDAM-induced necrosis, dithiothreitol protected against apoptosis, but cell permeable calcium chelators did not, suggesting that distinct biochemical pathways mediate these two forms of cell death. Pre-ER stress, but not heat shock, prevented IDAM-induced apoptosis. pkASgrp78 cells are deficient in Grp78 induction due to expression of a grp78 antisense RNA and are more sensitive to necrosis. However, these cells were resistant to IDAM-induced apoptosis and had increased basal levels of Grp94 and a KDEL-containing protein of about 50 kDa. Thus, the expression of grp78 antisense perturbs ER functions and activates expression of other ER stress genes accounting for the resistance to apoptosis. Taken together, the data describe functionally distinct signaling pathways through which the ER regulates apoptosis and necrosis caused by chemical toxicants.
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Affiliation(s)
- B van De Water
- Adirondack Biomedical Research Institute, 10 Old Barn Road, Lake Placid, New York 12946, USA
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43
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Rubio ME, Wenthold RJ. Calnexin and the immunoglobulin binding protein (BiP) coimmunoprecipitate with AMPA receptors. J Neurochem 1999; 73:942-8. [PMID: 10461883 DOI: 10.1046/j.1471-4159.1999.0730942.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
To identify proteins that interact with alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors, we carried out coimmunoprecipitation analyses on detergent-solubilized rat forebrain membranes. Membranes were solubilized with Triton X-100, and immunoprecipitation was done using subunit-specific antibodies to GluR1, GluR2/3, and GluR4 attached to protein Aagarose. Proteins bound to the antibodies were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by silver staining and western blotting. With solubilization in low ionic strength buffer, several coimmunoprecipitating proteins, with Mr = 17,000-100,000, were identified in silver-stained gels. Western blots were then probed with antibodies to a series of candidate proteins that were chosen based on the molecular masses of the copurifying proteins. Two of these were identified as the molecular chaperones calnexin (90 kDa) and the immunoglobulin binding protein (BiP; 78 kDa). Immunoprecipitation with antibodies to calnexin and BiP demonstrated that glycosylated AMPA receptor subunits were associated. The relationship between AMPA receptors and calnexin and BiP was further studied with immunocytochemistry of the hippocampus. Both calnexin and BiP labeling was present not only in the cell body but also in dendrites of hippocampal pyramidal neurons, where double-label immunofluorescence also showed the presence of AMPA receptor subunits.
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Affiliation(s)
- M E Rubio
- Laboratory of Neurochemistry, NIDCD, NIH, Bethesda, Maryland 20892-4162, USA
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Baluska F, Samaj J, Napier R, Volkmann D. Maize calreticulin localizes preferentially to plasmodesmata in root apex. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 1999; 19:481-8. [PMID: 10504570 DOI: 10.1046/j.1365-313x.1999.00530.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Using a polyclonal antibody raised against calreticulin purified and sequenced from maize, we performed an immunocytological study to characterize putative domain-specific subcellular distributions of endoplasmic reticulum (ER)-resident calreticulin in meristematic cells of maize root tip. At the light microscopy level, calreticulin was immunolocalized preferentially at cellular peripheries, in addition to nuclear envelopes and cytoplasmic structures. Punctate labelling at the longitudinal walls and continuous labelling at the transverse walls was characteristic. Immunogold electron microscopy revealed plasmodesmata as the most prominently labelled cell periphery structure. In order to further probe the ER-domain-specific distribution of maize calreticulin at plasmodesmata, root apices were exposed to mannitol-induced osmotic stress. Plasmolysis was associated with prominent accumulations of calreticulin at callose-enriched plasmodesmata and pit fields while the contracting protoplasts were depleted of calreticulin. In contrast, other ER-resident proteins recognized by HDEL peptide and BiP antibodies localized exclusively to contracted protoplasts. This finding reveals that, in plasmolysed cells, calreticulin enriched ER domains at plasmodesmata and pit fields are depleted of other ER-resident proteins containing the HDEL retention peptide.
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Affiliation(s)
- F Baluska
- Institute of Botany, Rheinische Friedrich-Wilhelms University Bonn, Department of Plant Cell Biology, Bonn, Germany.
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45
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Abstract
Glutamate receptors are synthesized in the cell body and transported in intracellular compartments to the target synapse. The objective of the present study was to analyze the intracellular pool of glutamate receptors and determine whether the intracellular pool was related to the synaptic distribution of the receptors. As a model system, we chose the fusiform cell of the dorsal cochlear nucleus for which we have previously demonstrated that receptors are selectively targeted to synapses on apical and basal dendrites. A combination of retrograde tracing and postembedding immunogold labeling was used to quantify intracellular receptors in segments of apical and basal dendrites. Immunolabeling for GluR4 and mGluR1alpha is present at synapses on basal dendrites but not on apical dendrites, whereas immunolabeling for GluR2/3 is present at both populations of synapses. In the analysis of intracellular pools, we find that GluR2/3 is equally distributed in apical and basal dendrites, whereas GluR4 and mGluR1alpha are more concentrated in basal dendrites than in apical dendrites. These findings indicate that the distribution of intracellular receptors is related to that of synaptic receptors and suggest that a mechanism exists in neurons to target proteins to dendritic domains soon after synthesis. We found no evidence for the existence of a pool of intracellular receptors, which could represent a receptor reserve, near the postsynaptic density. Receptors were often found in clusters associated with tubulovesicular membranes of the endoplasmic reticulum, identified with immunoglobulin binding protein (BIP) or calnexin, suggesting that this organelle is involved in receptor transport in dendrites.
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46
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Santalova IM, Moshkov DA, Kositsyn NS. Changes in the ratio of the rough and smooth endoplasmic reticulum in fish Mauthner neurons as a measure of compensatory processes occurring in response to sensory stimulation. NEUROSCIENCE AND BEHAVIORAL PHYSIOLOGY 1999; 29:427-31. [PMID: 10582226 DOI: 10.1007/bf02461080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- I M Santalova
- Neuron Ultrastructure Laboratory, Russian Academy of Sciences, Pushchino, Moscow Region
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47
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Rubio ME, Wenthold RJ. Differential distribution of intracellular glutamate receptors in dendrites. J Neurosci 1999; 19:5549-62. [PMID: 10377362 PMCID: PMC6782302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023] Open
Abstract
Glutamate receptors are synthesized in the cell body and transported in intracellular compartments to the target synapse. The objective of the present study was to analyze the intracellular pool of glutamate receptors and determine whether the intracellular pool was related to the synaptic distribution of the receptors. As a model system, we chose the fusiform cell of the dorsal cochlear nucleus for which we have previously demonstrated that receptors are selectively targeted to synapses on apical and basal dendrites. A combination of retrograde tracing and postembedding immunogold labeling was used to quantify intracellular receptors in segments of apical and basal dendrites. Immunolabeling for GluR4 and mGluR1alpha is present at synapses on basal dendrites but not on apical dendrites, whereas immunolabeling for GluR2/3 is present at both populations of synapses. In the analysis of intracellular pools, we find that GluR2/3 is equally distributed in apical and basal dendrites, whereas GluR4 and mGluR1alpha are more concentrated in basal dendrites than in apical dendrites. These findings indicate that the distribution of intracellular receptors is related to that of synaptic receptors and suggest that a mechanism exists in neurons to target proteins to dendritic domains soon after synthesis. We found no evidence for the existence of a pool of intracellular receptors, which could represent a receptor reserve, near the postsynaptic density. Receptors were often found in clusters associated with tubulovesicular membranes of the endoplasmic reticulum, identified with immunoglobulin binding protein (BIP) or calnexin, suggesting that this organelle is involved in receptor transport in dendrites.
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Affiliation(s)
- M E Rubio
- Laboratory of Neurochemistry, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland 20892, USA
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48
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Lee MG, Wigley WC, Zeng W, Noel LE, Marino CR, Thomas PJ, Muallem S. Regulation of Cl-/ HCO3- exchange by cystic fibrosis transmembrane conductance regulator expressed in NIH 3T3 and HEK 293 cells. J Biol Chem 1999; 274:3414-21. [PMID: 9920885 DOI: 10.1074/jbc.274.6.3414] [Citation(s) in RCA: 115] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A central function of cystic fibrosis transmembrane conductance regulator (CFTR)-expressing tissues is the secretion of fluid containing 100-140 mM HCO3-. High levels of HCO3- maintain secreted proteins such as mucins (all tissues) and digestive enzymes (pancreas) in a soluble and/or inactive state. HCO3- secretion is impaired in CF in all CFTR-expressing, HCO3--secreting tissues examined. The mechanism responsible for this critical problem in CF is unknown. Since a major component of HCO3- secretion in CFTR-expressing cells is mediated by the action of a Cl-/HCO3- exchanger (AE), in the present work we examined the regulation of AE activity by CFTR. In NIH 3T3 cells stably transfected with wild type CFTR and in HEK 293 cells expressing WT and several mutant CFTR, activation of CFTR by cAMP stimulated AE activity. Pharmacological and mutagenesis studies indicated that expression of CFTR in the plasma membrane, but not the Cl- conductive function of CFTR was required for activation of AE. Furthermore, mutations in NBD2 altered regulation of AE activity by CFTR independent of their effect on Cl- channel activity. At very high expression levels CFTR modified the sensitivity of AE to 4,4'-diisothiocyanatostilbene-2, 2'-disulfonate. The novel finding of regulation of Cl-/HCO3- exchange by CFTR reported here may have important physiological implications and explain, at least in part, the impaired HCO3- secretion in CF.
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Affiliation(s)
- M G Lee
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75235, USA
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49
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Abstract
There is a growing body of evidence that local protein synthesis beneath synapses may provide a novel mechanism underlying plastic phenomena. In vivo and in vitro biochemical data show that dendrites can perform translation and glycosylation. Using antibodies directed against the eukaryotic protein synthetic machinery, we sought to identify the structures implicated in nonperinuclear translation, namely dendritic and postsynaptic protein synthesis. We performed a morphological and immunocytochemical analysis of ventromedial horn rat spinal cord neurons using both light and electron microscopy. We show at the cellular level that, in vivo, protein synthesis macrocomplexes (ribosomes and eIF-2) as well as the endomembranous system implicated in cotranslational and posttranslational modifications (endoplasmic reticulum and Golgi cisternae) penetrated some dendrites. Membrane-limited organelles of different shape and size are present close to the postsynaptic differentiations of most synapses, independently of their localization on the neuronal surface. We demonstrate (1) that some cisternae are immunoreactive for antibodies against ribosomal proteins and eIF-2, and (2) that markers of endoplasmic reticulum (BiP), intermediate compartment, and Golgi complex (rab1, CTR433, TGN38) label subsets of these subsynaptic organelles. Therefore, these findings indicate that synapses are equipped with the essential elements required for the synthesis and insertion of a well folded and glycosylated transmembrane protein.
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50
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Gardiol A, Racca C, Triller A. Dendritic and postsynaptic protein synthetic machinery. J Neurosci 1999; 19:168-79. [PMID: 9870948 PMCID: PMC6782360] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023] Open
Abstract
There is a growing body of evidence that local protein synthesis beneath synapses may provide a novel mechanism underlying plastic phenomena. In vivo and in vitro biochemical data show that dendrites can perform translation and glycosylation. Using antibodies directed against the eukaryotic protein synthetic machinery, we sought to identify the structures implicated in nonperinuclear translation, namely dendritic and postsynaptic protein synthesis. We performed a morphological and immunocytochemical analysis of ventromedial horn rat spinal cord neurons using both light and electron microscopy. We show at the cellular level that, in vivo, protein synthesis macrocomplexes (ribosomes and eIF-2) as well as the endomembranous system implicated in cotranslational and posttranslational modifications (endoplasmic reticulum and Golgi cisternae) penetrated some dendrites. Membrane-limited organelles of different shape and size are present close to the postsynaptic differentiations of most synapses, independently of their localization on the neuronal surface. We demonstrate (1) that some cisternae are immunoreactive for antibodies against ribosomal proteins and eIF-2, and (2) that markers of endoplasmic reticulum (BiP), intermediate compartment, and Golgi complex (rab1, CTR433, TGN38) label subsets of these subsynaptic organelles. Therefore, these findings indicate that synapses are equipped with the essential elements required for the synthesis and insertion of a well folded and glycosylated transmembrane protein.
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Affiliation(s)
- A Gardiol
- Laboratoire de Biologie Cellulaire de la Synapse Normale et Pathologique, Institut National de la Santé et de la Recherche Médicale U497, Ecole Normale Supérieure, 75005 Paris, France
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