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Zhang Z, Zhou H, Gu W, Wei Y, Mou S, Wang Y, Zhang J, Zhong Q. CGI1746 targets σ 1R to modulate ferroptosis through mitochondria-associated membranes. Nat Chem Biol 2024; 20:699-709. [PMID: 38212578 DOI: 10.1038/s41589-023-01512-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 11/17/2023] [Indexed: 01/13/2024]
Abstract
Ferroptosis is iron-dependent oxidative cell death. Labile iron and polyunsaturated fatty acid (PUFA)-containing lipids are two critical factors for ferroptosis execution. Many processes regulating iron homeostasis and lipid synthesis are critically involved in ferroptosis. However, it remains unclear whether biological processes other than iron homeostasis and lipid synthesis are associated with ferroptosis. Using kinase inhibitor library screening, we discovered a small molecule named CGI1746 that potently blocks ferroptosis. Further studies demonstrate that CGI1746 acts through sigma-1 receptor (σ1R), a chaperone primarily located at mitochondria-associated membranes (MAMs), to inhibit ferroptosis. Suppression of σ1R protects mice from cisplatin-induced acute kidney injury hallmarked by ferroptosis. Mechanistically, CGI1746 treatment or genetic disruption of MAMs leads to defective Ca2+ transfer, mitochondrial reactive oxygen species (ROS) production and PUFA-containing triacylglycerol accumulation. Therefore, we propose a critical role for MAMs in ferroptosis execution.
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Affiliation(s)
- Zili Zhang
- Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Department of Pathophysiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Hong Zhou
- Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Department of Pathophysiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Wenjia Gu
- Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing, China
- Key Laboratory of Cell Proliferation and Regulation Biology, Ministry of Education, College of Life Sciences, Beijing Normal University, Beijing, China
| | - Yuehan Wei
- Department of Nephrology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Shan Mou
- Department of Nephrology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Youjun Wang
- Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing, China.
- Key Laboratory of Cell Proliferation and Regulation Biology, Ministry of Education, College of Life Sciences, Beijing Normal University, Beijing, China.
| | - Jing Zhang
- Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Department of Pathophysiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
| | - Qing Zhong
- Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Department of Pathophysiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
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2
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Capture at the ER-mitochondrial contacts licenses IP 3 receptors to stimulate local Ca 2+ transfer and oxidative metabolism. Nat Commun 2022; 13:6779. [PMID: 36351901 PMCID: PMC9646835 DOI: 10.1038/s41467-022-34365-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Accepted: 10/24/2022] [Indexed: 11/10/2022] Open
Abstract
Endoplasmic reticulum-mitochondria contacts (ERMCs) are restructured in response to changes in cell state. While this restructuring has been implicated as a cause or consequence of pathology in numerous systems, the underlying molecular dynamics are poorly understood. Here, we show means to visualize the capture of motile IP3 receptors (IP3Rs) at ERMCs and document the immediate consequences for calcium signaling and metabolism. IP3Rs are of particular interest because their presence provides a scaffold for ERMCs that mediate local calcium signaling, and their function outside of ERMCs depends on their motility. Unexpectedly, in a cell model with little ERMC Ca2+ coupling, IP3Rs captured at mitochondria promptly mediate Ca2+ transfer, stimulating mitochondrial oxidative metabolism. The Ca2+ transfer does not require linkage with a pore-forming protein in the outer mitochondrial membrane. Thus, motile IP3Rs can traffic in and out of ERMCs, and, when 'parked', mediate calcium signal propagation to the mitochondria, creating a dynamic arrangement that supports local communication.
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3
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Ballesteros A, Fitzgerald TS, Swartz KJ. Expression of a membrane-targeted fluorescent reporter disrupts auditory hair cell mechanoelectrical transduction and causes profound deafness. Hear Res 2021; 404:108212. [PMID: 33667877 PMCID: PMC8035305 DOI: 10.1016/j.heares.2021.108212] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Revised: 02/11/2021] [Accepted: 02/13/2021] [Indexed: 11/22/2022]
Abstract
The reporter mT/mG mice expressing a membrane-targeted fluorescent protein are becoming widely used to study the auditory and vestibular system due to its versatility. Here we show that high expression levels of the fluorescent mtdTomato reporter affect the function of the sensory hair cells and the auditory performance of mT/mG transgenic mice. Auditory brainstem responses and distortion product otoacoustic emissions revealed that adult mT/mG homozygous mice are profoundly deaf, whereas heterozygous mice present high frequency loss. We explore whether this line would be useful for studying and visualizing the membrane of auditory hair cells by airyscan super-resolution confocal microscopy. Membrane localization of the reporter was observed in hair cells of the cochlea, facilitating imaging of both cell bodies and stereocilia bundles without altering cellular architecture or the expression of the integral membrane motor protein prestin. Remarkably, hair cells from mT/mG homozygous mice failed to uptake the FM1-43 dye and to locate TMC1 at the stereocilia, indicating defective mechanotransduction machinery. Our work emphasizes that precautions must be considered when working with reporter mice and highlights the potential role of the cellular membrane in maintaining functional hair cells and ensuring proper hearing.
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Affiliation(s)
- Angela Ballesteros
- Molecular Physiology and Biophysics Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, United States.
| | - Tracy S Fitzgerald
- Mouse Auditory Testing Core, National Institute on Deafness and other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, United States
| | - Kenton J Swartz
- Molecular Physiology and Biophysics Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, United States.
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4
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Jain A, Dadsena S, Holthuis JCM. A switchable ceramide transfer protein for dissecting the mechanism of ceramide‐induced mitochondrial apoptosis. FEBS Lett 2020; 594:3739-3750. [DOI: 10.1002/1873-3468.13956] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2020] [Revised: 10/06/2020] [Accepted: 10/07/2020] [Indexed: 12/17/2022]
Affiliation(s)
- Amrita Jain
- Molecular Cell Biology Division Department of Biology/Chemistry and Center for Cellular Nanoanalytics Osnabrück University of Osnabrück Germany
| | - Shashank Dadsena
- Molecular Cell Biology Division Department of Biology/Chemistry and Center for Cellular Nanoanalytics Osnabrück University of Osnabrück Germany
| | - Joost C. M. Holthuis
- Molecular Cell Biology Division Department of Biology/Chemistry and Center for Cellular Nanoanalytics Osnabrück University of Osnabrück Germany
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5
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Degron-tagged reporters probe membrane topology and enable the specific labelling of membrane-wrapped structures. Nat Commun 2019; 10:3490. [PMID: 31375709 PMCID: PMC6677802 DOI: 10.1038/s41467-019-11442-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Accepted: 07/16/2019] [Indexed: 12/24/2022] Open
Abstract
Visualization of specific organelles in tissues over background fluorescence can be challenging, especially when reporters localize to multiple structures. Instead of trying to identify proteins enriched in specific membrane-wrapped structures, we use a selective degradation approach to remove reporters from the cytoplasm or nucleus of C. elegans embryos and mammalian cells. We demonstrate specific labelling of organelles using degron-tagged reporters, including extracellular vesicles, as well as individual neighbouring membranes. These degron-tagged reporters facilitate long-term tracking of released cell debris and cell corpses, even during uptake and phagolysosomal degradation. We further show that degron protection assays can probe the topology of the nuclear envelope and plasma membrane during cell division, giving insight into protein and organelle dynamics. As endogenous and heterologous degrons are used in bacteria, yeast, plants, and animals, degron approaches can enable the specific labelling and tracking of proteins, vesicles, organelles, cell fragments, and cells in many model systems. Visualising certain organelles and their dynamics is challenging in living cells. Here the authors co-opt selective degradation to label membrane-bound compartments in worm embryos and mammalian cells, revealing membrane topology during cell division.
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6
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Joseph SK, Booth DM, Young MP, Hajnóczky G. Redox regulation of ER and mitochondrial Ca 2+ signaling in cell survival and death. Cell Calcium 2019; 79:89-97. [PMID: 30889512 DOI: 10.1016/j.ceca.2019.02.006] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Revised: 02/12/2019] [Accepted: 02/12/2019] [Indexed: 12/16/2022]
Abstract
Physiological signaling by reactive oxygen species (ROS) and their pathophysiological role in cell death are well recognized. This review focuses on two ROS targets that are key to local Ca2+ signaling at the ER/mitochondrial interface - notably, inositol trisphosphate receptors (IP3Rs) and the mitochondrial calcium uniporter (MCU). Both transport systems are central to molecular mechanisms in cell survival and death. Methods for the measurement of the redox state of these proteins and for the detection of ROS nanodomains are described. Recent results on the redox regulation of these proteins are reviewed.
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Affiliation(s)
- Suresh K Joseph
- MitoCare, Department of Pathology and Cell Biology, Thomas Jefferson University, Philadelphia, PA, 19107, USA.
| | - David M Booth
- MitoCare, Department of Pathology and Cell Biology, Thomas Jefferson University, Philadelphia, PA, 19107, USA
| | - Michael P Young
- MitoCare, Department of Pathology and Cell Biology, Thomas Jefferson University, Philadelphia, PA, 19107, USA
| | - György Hajnóczky
- MitoCare, Department of Pathology and Cell Biology, Thomas Jefferson University, Philadelphia, PA, 19107, USA
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7
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Park S, Lim JM, Park SH, Kim S, Heo S, Balla T, Jeong W, Rhee SG, Kang D. Inactivation of the PtdIns(4)P phosphatase Sac1 at the Golgi by H 2O 2 produced via Ca 2+-dependent Duox in EGF-stimulated cells. Free Radic Biol Med 2019; 131:40-49. [PMID: 30476538 DOI: 10.1016/j.freeradbiomed.2018.11.021] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Revised: 11/19/2018] [Accepted: 11/19/2018] [Indexed: 11/27/2022]
Abstract
Binding of epidermal growth factor (EGF) to its cell surface receptor induces production of H2O2, which serves as an intracellular messenger. We have shown that exogenous H2O2 reversibly inactivates the phosphatidylinositol 4-phosphate [PtdIns(4)P] phosphatase Sac1 (suppressor of actin 1) at the Golgi complex of mammalian cells by oxidizing its catalytic cysteine residue and thereby increases both the amount of Golgi PtdIns(4)P and the rate of protein secretion. Here we investigated the effects of EGF on Sac1 oxidation and PtdIns(4)P abundance at the Golgi in A431 cells. EGF induced a transient increase in Golgi PtdIns(4)P as well as a transient oxidation of Sac1 in a manner dependent on elevation of the intracellular Ca2+ concentration and on H2O2. Oxidation of Sac1 occurred at the Golgi, as revealed with the use of the Golgi-confined Sac1-K2A mutant. Knockdown of Duox enzymes implicated these Ca2+-dependent members of the NADPH oxidase family as the major source of H2O2 for Sac1 oxidation. Expression of a Golgi-targeted H2O2 probe revealed transient EGF-induced H2O2 production at this organelle. Our findings have thus uncovered a previously unrecognized EGF signaling pathway that links intracellular Ca2+ mobilization to events at the Golgi including Duox activation, H2O2 production, Sac1 oxidation, and PtdIns(4)P accumulation.
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Affiliation(s)
- Sujin Park
- Department of Life Science, Ewha Womans University, Seoul 03760, Republic of Korea
| | - Jung Mi Lim
- Department of Life Science, Ewha Womans University, Seoul 03760, Republic of Korea
| | - Seon Hwa Park
- Department of Life Science, Ewha Womans University, Seoul 03760, Republic of Korea
| | - Suree Kim
- Department of Life Science, Ewha Womans University, Seoul 03760, Republic of Korea
| | - Sukyeong Heo
- Department of Life Science, Ewha Womans University, Seoul 03760, Republic of Korea
| | - Tamas Balla
- Section on Molecular Signal Transduction, National Institutes of Health, Bethesda, MD 20892, USA
| | - Woojin Jeong
- Department of Life Science and the Research Center for Cellular Homeostasis, Ewha Womans University, Seoul 03760, Republic of Korea
| | - Sue Goo Rhee
- Yonsei Biomedical Research Institute, Yonsei University, Seoul 03722, Republic of Korea.
| | - Dongmin Kang
- Department of Life Science, Ewha Womans University, Seoul 03760, Republic of Korea.
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8
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Lim JM, Park S, Lee MS, Balla T, Kang D, Rhee SG. Accumulation of PtdIns(4)P at the Golgi mediated by reversible oxidation of the PtdIns(4)P phosphatase Sac1 by H 2O 2. Free Radic Biol Med 2019; 130:426-435. [PMID: 30448513 DOI: 10.1016/j.freeradbiomed.2018.11.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Revised: 11/08/2018] [Accepted: 11/09/2018] [Indexed: 12/27/2022]
Abstract
Phosphatidylinositol 4-phosphate [PtdIns(4)P] plays a key role in the biogenesis of transport vesicles at the Golgi complex by recruiting coat proteins and their accessory factors. The PtdIns(4)P content of the Golgi is determined by the concerted action of PtdIns 4-kinase (PI4K) and PtdIns(4)P phosphatase enzymes. Sac1 (suppressor of actin 1) is the major PtdIns(4)P phosphatase and is localized to the Golgi and endoplasmic reticulum. The targeting of both PI4Ks and Sac1 to the Golgi membrane is extensively regulated, as is the catalytic activity of PI4Ks at the Golgi. However, regulation of the catalytic activity of Sac1 has been largely unexplored. Here we show that Sac1undergoes reversible inactivation in mammalian cells when its catalytic Cys389 residue is oxidized by exogenous H2O2 to form an intramolecular disulfide with Cys392. The oxidative inactivation of Sac1 results in the accumulation of PtdIns(4)P at the Golgi, with this effect also being supported by the H2O2-induced activation of p38 mitogen-activated protein kinase (MAPK), which was previously shown to promote the translocation of Sac1 from the Golgi to the endoplasmic reticulum. The increase in Golgi PtdIns(4)P due to Sac1 inactivation, however, is faster than that due to Sac1 translocation. Exposure of cells to H2O2 also increased membrane protein trafficking from the Golgi to the plasma membrane as well as protein secretion.
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Affiliation(s)
- Jung Mi Lim
- Department of Life Science, Ewha Womans University, Seoul 03760, Republic of Korea
| | - Sujin Park
- Department of Life Science, Ewha Womans University, Seoul 03760, Republic of Korea
| | - Mi-Sook Lee
- Department of Life Science, Ewha Womans University, Seoul 03760, Republic of Korea
| | - Tamas Balla
- Section on Molecular Signal Transduction, NICHD, National Institutes of Health, Bethesda, MD 20892, USA
| | - Dongmin Kang
- Department of Life Science, Ewha Womans University, Seoul 03760, Republic of Korea.
| | - Sue Goo Rhee
- Yonsei Biomedical Research Institute, Yonsei University, Seoul 03722, Republic of Korea.
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9
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Ishibashi Y, Ito M, Hirabayashi Y. Regulation of glucosylceramide synthesis by Golgi-localized phosphoinositide. Biochem Biophys Res Commun 2018; 499:1011-1018. [DOI: 10.1016/j.bbrc.2018.04.039] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2018] [Accepted: 04/04/2018] [Indexed: 10/17/2022]
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10
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Yang Z, Zhao X, Xu J, Shang W, Tong C. A novel fluorescent reporter detects plastic remodeling of mitochondria-ER contact sites. J Cell Sci 2018; 131:jcs.208686. [PMID: 29158224 DOI: 10.1242/jcs.208686] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Accepted: 11/13/2017] [Indexed: 12/21/2022] Open
Abstract
Mitochondria-ER contact sites (MERCs) enable communication between the ER and mitochondria and serve as platforms for many cellular events, including autophagy. Nonetheless, the molecular organization of MERCs is not known, and there is no bona fide marker of these contact sites in mammalian cells. In this study, we designed a genetically encoded reporter using split GFP protein for labeling MERCs. We subsequently analyzed its distribution and dynamics during the cell cycle and under stressful cellular conditions such as starvation, apoptosis and ER stress. We found that MERCs are dynamic structures that undergo remodeling within minutes. Mitochondrial morphology, but not ER morphology, affected the distribution of MERCs. We also found that carbonyl cyanidem-chlorophenyl hydrazone (CCCP) and oligomycin A treatment enhanced MERC formation. The stimulations that led to apoptosis or autophagy increased the MERC signal. By contrast, increasing cellular lipid droplet load did not change the pattern of MERCs.
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Affiliation(s)
- Zhaoying Yang
- Life Sciences Institute and Innovation Center for Cell Signaling Network, Zhejiang University, Hangzhou 310058, China
| | - Xiaocui Zhao
- Life Sciences Institute and Innovation Center for Cell Signaling Network, Zhejiang University, Hangzhou 310058, China
| | - Jiashen Xu
- Life Sciences Institute and Innovation Center for Cell Signaling Network, Zhejiang University, Hangzhou 310058, China
| | - Weina Shang
- Life Sciences Institute and Innovation Center for Cell Signaling Network, Zhejiang University, Hangzhou 310058, China
| | - Chao Tong
- Life Sciences Institute and Innovation Center for Cell Signaling Network, Zhejiang University, Hangzhou 310058, China
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11
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12
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Várnai P, Gulyás G, Tóth DJ, Sohn M, Sengupta N, Balla T. Quantifying lipid changes in various membrane compartments using lipid binding protein domains. Cell Calcium 2016; 64:72-82. [PMID: 28088320 DOI: 10.1016/j.ceca.2016.12.008] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Revised: 12/28/2016] [Accepted: 12/29/2016] [Indexed: 11/30/2022]
Abstract
One of the largest challenges in cell biology is to map the lipid composition of the membranes of various organelles and define the exact location of processes that control the synthesis and distribution of lipids between cellular compartments. The critical role of phosphoinositides, low-abundant lipids with rapid metabolism and exceptional regulatory importance in the control of almost all aspects of cellular functions created the need for tools to visualize their localizations and dynamics at the single cell level. However, there is also an increasing need for methods to determine the cellular distribution of other lipids regulatory or structural, such as diacylglycerol, phosphatidic acid, or other phospholipids and cholesterol. This review will summarize recent advances in this research field focusing on the means by which changes can be described in more quantitative terms.
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Affiliation(s)
- Péter Várnai
- Department of Physiology, Faculty of Medicine, Semmelweis University, Budapest, Hungary
| | - Gergő Gulyás
- Department of Physiology, Faculty of Medicine, Semmelweis University, Budapest, Hungary
| | - Dániel J Tóth
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, United States; Department of Physiology, Faculty of Medicine, Semmelweis University, Budapest, Hungary
| | - Mira Sohn
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, United States
| | - Nivedita Sengupta
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, United States
| | - Tamas Balla
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, United States.
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13
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Poteser M, Leitinger G, Pritz E, Platzer D, Frischauf I, Romanin C, Groschner K. Live-cell imaging of ER-PM contact architecture by a novel TIRFM approach reveals extension of junctions in response to store-operated Ca 2+-entry. Sci Rep 2016; 6:35656. [PMID: 27759093 PMCID: PMC5069484 DOI: 10.1038/srep35656] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Accepted: 09/29/2016] [Indexed: 01/16/2023] Open
Abstract
Nanometer-spaced appositions between endoplasmic reticulum and plasma membrane (ER-PM junctions) stabilized by membrane-joining protein complexes are critically involved in cellular Ca2+-handling and lipid trafficking. ER-PM junctional architecture and plasticity associated with inter-membrane communication are as yet barely understood. Here, we introduce a method to precisely characterize ER-PM junction morphology and dynamics with high temporal resolution and minimal disturbance of junctional intermembrane communication. We show that expression of soluble cytosolic fluorophores in combination with TIRFM enables to delineate ER and PM distance in the range of 10-150 nm. Live-cell imaging of sub-plasmalemmal structures in RBL-2H3 mast cells by this method, designated as fluorescence density mapping (FDM), revealed profound dynamics of ER-PM contact sites in response to store-depletion. We report the existence of a Ca2+-dependent process that expands the junctional ER to enlarge its contact surface with the PM, thereby promoting and stabilizing STIM1-Orai1 competent ER-PM junctions.
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Affiliation(s)
- Michael Poteser
- Institute of Biophysics, Medical University of Graz, Harrachgasse 21/4, 8010 Graz, Austria
| | - Gerd Leitinger
- Institute of Cell Biology, Histology and Embryology Research Unit "Electron Microscopic Techniques", Medical University of Graz, Harrachgasse 21/7, 8010 Graz, Austria
| | - Elisabeth Pritz
- Institute of Cell Biology, Histology and Embryology Research Unit "Electron Microscopic Techniques", Medical University of Graz, Harrachgasse 21/7, 8010 Graz, Austria
| | - Dieter Platzer
- Institute of Biophysics, Medical University of Graz, Harrachgasse 21/4, 8010 Graz, Austria
| | - Irene Frischauf
- Institute of Biophysics, Johannes Kepler University of Linz, Austria, Gruberstrasse 40, 4020 Linz, Austria
| | - Christoph Romanin
- Institute of Biophysics, Johannes Kepler University of Linz, Austria, Gruberstrasse 40, 4020 Linz, Austria
| | - Klaus Groschner
- Institute of Biophysics, Medical University of Graz, Harrachgasse 21/4, 8010 Graz, Austria
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14
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Redox Nanodomains Are Induced by and Control Calcium Signaling at the ER-Mitochondrial Interface. Mol Cell 2016; 63:240-248. [PMID: 27397688 DOI: 10.1016/j.molcel.2016.05.040] [Citation(s) in RCA: 216] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Revised: 01/27/2016] [Accepted: 05/26/2016] [Indexed: 02/06/2023]
Abstract
The ER-mitochondrial interface is central to calcium signaling, organellar dynamics, and lipid biosynthesis. The ER and mitochondrial membranes also host sources and targets of reactive oxygen species (ROS), but their local dynamics and relevance remained elusive since measurement and perturbation of ROS at the organellar interface has proven difficult. Employing drug-inducible synthetic ER-mitochondrial linkers, we overcame this problem and demonstrate that the ER-mitochondrial interface hosts a nanodomain of H2O2, which is induced by cytoplasmic [Ca(2+)] spikes and exerts a positive feedback on calcium oscillations. H2O2 nanodomains originate from the mitochondrial cristae, which are compressed upon calcium signal propagation to the mitochondria, likely due to Ca(2+)-induced K(+) and concomitant water influx to the matrix. Thus, ER-mitochondrial H2O2 nanodomains represent a component of inter-organelle communication, regulating calcium signaling and mitochondrial activities.
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15
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Kittelberger N, Breunig M, Martin R, Knölker HJ, Miklavc P. The role of myosin 1c and myosin 1b in surfactant exocytosis. J Cell Sci 2016; 129:1685-96. [PMID: 26940917 PMCID: PMC4852769 DOI: 10.1242/jcs.181313] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Accepted: 02/25/2016] [Indexed: 12/19/2022] Open
Abstract
Actin and actin-associated proteins have a pivotal effect on regulated exocytosis in secretory cells and influence pre-fusion as well as post-fusion stages of exocytosis. Actin polymerization on secretory granules during the post-fusion phase (formation of an actin coat) is especially important in cells with large secretory vesicles or poorly soluble secretions. Alveolar type II (ATII) cells secrete hydrophobic lipo-protein surfactant, which does not easily diffuse from fused vesicles. Previous work showed that compression of actin coat is necessary for surfactant extrusion. Here, we investigate the role of class 1 myosins as possible linkers between actin and membranes during exocytosis. Live-cell microscopy showed translocation of fluorescently labeled myosin 1b and myosin 1c to the secretory vesicle membrane after fusion. Myosin 1c translocation was dependent on its pleckstrin homology domain. Expression of myosin 1b and myosin 1c constructs influenced vesicle compression rate, whereas only the inhibition of myosin 1c reduced exocytosis. These findings suggest that class 1 myosins participate in several stages of ATII cell exocytosis and link actin coats to the secretory vesicle membrane to influence vesicle compression.
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Affiliation(s)
- Nadine Kittelberger
- Institute of General Physiology, Ulm University, Albert-Einstein Allee 11, Ulm 89081, Germany
| | - Markus Breunig
- Institute of General Physiology, Ulm University, Albert-Einstein Allee 11, Ulm 89081, Germany
| | - René Martin
- Department of Chemistry, Technische Universität Dresden, Bergstr. 66, Dresden 01069, Germany
| | - Hans-Joachim Knölker
- Department of Chemistry, Technische Universität Dresden, Bergstr. 66, Dresden 01069, Germany
| | - Pika Miklavc
- Institute of General Physiology, Ulm University, Albert-Einstein Allee 11, Ulm 89081, Germany
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16
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Lamellipodin Is Important for Cell-to-Cell Spread and Actin-Based Motility in Listeria monocytogenes. Infect Immun 2015; 83:3740-8. [PMID: 26169271 PMCID: PMC4534642 DOI: 10.1128/iai.00193-15] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Accepted: 07/05/2015] [Indexed: 12/13/2022] Open
Abstract
Listeria monocytogenes is a foodborne pathogen capable of invading a broad range of cell types and replicating within the host cell cytoplasm. This paper describes the colocalization of host cell lamellipodin (Lpd) with intracellular L. monocytogenes detectable 6 h postinfection of epithelial cells. The association was mediated via interactions between both the peckstrin homology (PH) domain in Lpd and phosphatidylinositol (3,4)-bisphosphate [PI(3,4)P2] on the bacterial surface and by interactions between the C-terminal EVH1 (Ena/VASP [vasodilator-stimulated phosphoprotein] homology domain 1) binding domains of Lpd and the host VASP (vasodilator-stimulated phosphoprotein) recruited to the bacterial cell surface by the listerial ActA protein. Depletion of Lpd by short interfering RNA (siRNA) resulted in reduced plaque size and number, indicating a role for Lpd in cell-to-cell spread. In contrast, overexpression of Lpd resulted in an increase in the number of L. monocytogenes-containing protrusions (listeriopods). Manipulation of the levels of Lpd within the cell also affected the intracellular velocity of L. monocytogenes, with a reduction in Lpd corresponding to an increase in intracellular velocity. These data, together with the observation that Lpd accumulated at the interface between the bacteria and the developing actin tail at the initiation of actin-based movement, indicate a possible role for Lpd in the actin-based movement and the cell-to-cell spread of L. monocytogenes.
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18
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Mori MX, Inoue R. New experimental trends for phosphoinositides research on ion transporter/channel regulation. J Pharmacol Sci 2014; 126:186-97. [PMID: 25367262 DOI: 10.1254/jphs.14r14cp] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
Abstract
Phosphoinositides(4,5)-bisphosphates [PI(4,5)P2] critically controls membrane excitability, the disruption of which leads to pathophysiological states. PI(4,5)P2 plays a primary role in regulating the conduction and gating properties of ion channels/transporters, through electrostatic and hydrophobic interactions that allow direct associations. In recent years, the development of many molecular tools have brought deep insights into the mechanisms underlying PI(4,5)P2-mediated regulation. This review summarizes the methods currently available to manipulate the cell membrane PI(4,5)P2 level including pharmacological interventions as well as newly designed molecular tools. We concisely introduce materials and experimental designs suitable for the study of PI(4,5)P2-mediated regulation of ion-conducting molecules, in order to assist researchers who are interested in this area. It is our further hope that the knowledge introduced in this review will help to promote our understanding about the pathology of diseases such as cardiac arrhythmias, bipolar disorders, and Alzheimer's disease which are somehow associated with a disruption of PI(4,5)P2 metabolism.
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Affiliation(s)
- Masayuki X Mori
- Department of Synthetic Chemistry and Biological Chemistry, School of Engineering, Kyoto University, Japan
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19
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Jiang Z, Redfern RE, Isler Y, Ross AH, Gericke A. Cholesterol stabilizes fluid phosphoinositide domains. Chem Phys Lipids 2014; 182:52-61. [PMID: 24556334 DOI: 10.1016/j.chemphyslip.2014.02.003] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Revised: 02/06/2014] [Accepted: 02/07/2014] [Indexed: 11/19/2022]
Abstract
Local accumulation of phosphoinositides (PIPs) is an important factor for a broad range of cellular events including membrane trafficking and cell signaling. The negatively charged phosphoinositide headgroups can interact with cations or cationic proteins and this electrostatic interaction has been identified as the main phosphoinositide clustering mechanism. However, an increasing number of reports show that phosphoinositide-mediated signaling events are at least in some cases cholesterol dependent, suggesting other possible contributors to the segregation of phosphoinositides. Using fluorescence microscopy on giant unilamellar vesicles and monolayers at the air/water interface, we present data showing that cholesterol stabilizes fluid phosphoinositide-enriched phases. The interaction with cholesterol is observed for all investigated phosphoinositides (PI(4)P, PI(3,4)P2, PI(3,5)P2, PI(4,5)P2 and PI(3,4,5)P3) as well as phosphatidylinositol. We find that cholesterol is present in the phosphoinositide-enriched phase and that the resulting phase is fluid. Cholesterol derivatives modified at the hydroxyl group (cholestenone, cholesteryl ethyl ether) do not promote formation of phosphoinositide domains, suggesting an instrumental role of the cholesterol hydroxyl group in the observed cholesterol/phosphoinositide interaction. This leads to the hypothesis that cholesterol participates in an intermolecular hydrogen bond network formed among the phosphoinositide lipids. We had previously reported that the intra- and intermolecular hydrogen bond network between the phosphoinositide lipids leads to a reduction of the charge density at the phosphoinositide phosphomonoester groups (Kooijman et al., 2009). We believe that cholesterol acts as a spacer between the phosphoinositide lipids, thereby reducing the electrostatic repulsion, while participating in the hydrogen bond network, leading to its further stabilization. To illustrate the effect of phosphoinositide segregation on protein binding, we show that binding of the tumor suppressor protein PTEN to PI(5)P and PI(4,5)P2 is enhanced in the presence of cholesterol. These results provide new insights into how phosphoinositides mediate important cellular events.
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Affiliation(s)
- Zhiping Jiang
- Laboratory of Molecular Biophysics, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, United States
| | - Roberta E Redfern
- ProMedica Research Department, ProMedica Health System, Toledo, OH 43606, United States
| | - Yasmin Isler
- Academic Health Center BioRepository, ProMedica Health System, Toledo, OH 43606, United States
| | - Alonzo H Ross
- University of Massachusetts Medical School, Worcester, MA 01605, United States
| | - Arne Gericke
- Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, 100 Institute Rd., Worcester, MA 01609, United States.
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20
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Kapus A, Janmey P. Plasma membrane--cortical cytoskeleton interactions: a cell biology approach with biophysical considerations. Compr Physiol 2013; 3:1231-81. [PMID: 23897686 DOI: 10.1002/cphy.c120015] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
From a biophysical standpoint, the interface between the cell membrane and the cytoskeleton is an intriguing site where a "two-dimensional fluid" interacts with an exceedingly complex three-dimensional protein meshwork. The membrane is a key regulator of the cytoskeleton, which not only provides docking sites for cytoskeletal elements through transmembrane proteins, lipid binding-based, and electrostatic interactions, but also serves as the source of the signaling events and molecules that control cytoskeletal organization and remolding. Conversely, the cytoskeleton is a key determinant of the biophysical and biochemical properties of the membrane, including its shape, tension, movement, composition, as well as the mobility, partitioning, and recycling of its constituents. From a cell biological standpoint, the membrane-cytoskeleton interplay underlies--as a central executor and/or regulator--a multitude of complex processes including chemical and mechanical signal transduction, motility/migration, endo-/exo-/phagocytosis, and other forms of membrane traffic, cell-cell, and cell-matrix adhesion. The aim of this article is to provide an overview of the tight structural and functional coupling between the membrane and the cytoskeleton. As biophysical approaches, both theoretical and experimental, proved to be instrumental for our understanding of the membrane/cytoskeleton interplay, this review will "oscillate" between the cell biological phenomena and the corresponding biophysical principles and considerations. After describing the types of connections between the membrane and the cytoskeleton, we will focus on a few key physical parameters and processes (force generation, curvature, tension, and surface charge) and will discuss how these contribute to a variety of fundamental cell biological functions.
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Affiliation(s)
- András Kapus
- Keenan Research Center, Li Ka Shing Knowledge Institute, St. Michael's Hospital and Department of Surgery, University of Toronto, Ontario, Canada.
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21
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Gyombolai P, Boros E, Hunyady L, Turu G. Differential β-arrestin2 requirements for constitutive and agonist-induced internalization of the CB1 cannabinoid receptor. Mol Cell Endocrinol 2013; 372:116-27. [PMID: 23541635 DOI: 10.1016/j.mce.2013.03.013] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Revised: 02/06/2013] [Accepted: 03/15/2013] [Indexed: 01/13/2023]
Abstract
CB1 cannabinoid receptor (CB1R) undergoes both constitutive and agonist-induced internalization, but the underlying mechanisms of these processes and the role of β-arrestins in the regulation of CB1R function are not completely understood. In this study, we followed CB1R internalization using confocal microscopy and bioluminescence resonance energy transfer measurements in HeLa and Neuro-2a cells. We found that upon activation CB1R binds β-arrestin2 (β-arr2), but not β-arrestin1. Furthermore, both the expression of dominant-negative β-arr2 (β-arr2-V54D) and siRNA-mediated knock-down of β-arr2 impaired the agonist-induced internalization of CB1R. In contrast, neither β-arr2-V54D nor β-arr2-specific siRNA had a significant effect on the constitutive internalization of CB1R. However, both constitutive and agonist-induced internalization of CB1R were impaired by siRNA-mediated depletion of clathrin heavy chain. We conclude that although clathrin is required for both constitutive and agonist-stimulated internalization of CB1R, β-arr2 binding is only required for agonist-induced internalization of the receptor suggesting that the molecular mechanisms underlying constitutive and agonist-induced internalization of CB1R are different.
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Affiliation(s)
- Pál Gyombolai
- Department of Physiology, Faculty of Medicine, Semmelweis University, Budapest, Hungary.
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22
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Wawrzyniak AM, Kashyap R, Zimmermann P. Phosphoinositides and PDZ domain scaffolds. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 991:41-57. [PMID: 23775690 DOI: 10.1007/978-94-007-6331-9_4] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The discovery that PSD-95/Discs large/ZO-1 (PDZ) domains can function as lipid-binding modules, in particular interacting with phosphoinositides (PIs), was made more than 10 years ago (Mol Cell 9(6): 1215-1225, 2002). Confirmatory studies and a series of functional follow-ups established PDZ domains as dual specificity modules displaying both peptide and lipid binding, and prompted a rethinking of the mode of action of PDZ domains in the control of cell signaling. In this chapter, after introducing PDZ domains, PIs and methods for studying protein-lipid interactions, we focus on (i) the prevalence and the specificity of PDZ-PIs interactions, (ii) the molecular determinants of PDZ-PIs interactions, (iii) the integration of lipid and peptide binding by PDZ domains, (iv) the common features of PIs interacting PDZ domains and (v) the regulation and functional significance of PDZ-PIs interactions.
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23
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Phua SC, Pohlmeyer C, Inoue T. Rapidly relocating molecules between organelles to manipulate small GTPase activity. ACS Chem Biol 2012; 7:1950-5. [PMID: 22999378 DOI: 10.1021/cb300280k] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Chemically inducible rapid manipulation of small GTPase activity has proven a powerful approach to dissect complex spatiotemporal signaling of these molecular switches. However, overexpression of these synthetic molecular probes freely in the cytosol often results in elevated background activity before chemical induction, which perturbs the cellular basal state and thereby limits their wide application. As a fundamental solution, we have rationally designed and newly developed a strategy to remove unwanted background activity without compromising the extent of induced activation. By exploiting interaction between a membrane lipid and its binding protein, target proteins were translocated from one organelle to another on a time scale of seconds. This improved strategy now allows for rapid manipulation of small GTPases under a physiological state, thus enabling fine dissection of sophisticated signaling processes shaped by these molecules.
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Affiliation(s)
- Siew Cheng Phua
- Department of Cell
Biology,
Center for Cell Dynamics, Johns Hopkins University, Baltimore, Maryland 21205, United States
| | - Christopher Pohlmeyer
- Department of Cell
Biology,
Center for Cell Dynamics, Johns Hopkins University, Baltimore, Maryland 21205, United States
| | - Takanari Inoue
- Department of Cell
Biology,
Center for Cell Dynamics, Johns Hopkins University, Baltimore, Maryland 21205, United States
- PRESTO Investigator, JST, 4-1-8 Honcho Kawaguchi, Saitama 332-0012, Japan
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24
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Amoasii L, Bertazzi DL, Tronchère H, Hnia K, Chicanne G, Rinaldi B, Cowling BS, Ferry A, Klaholz B, Payrastre B, Laporte J, Friant S. Phosphatase-dead myotubularin ameliorates X-linked centronuclear myopathy phenotypes in mice. PLoS Genet 2012; 8:e1002965. [PMID: 23071445 PMCID: PMC3469422 DOI: 10.1371/journal.pgen.1002965] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Accepted: 08/08/2012] [Indexed: 12/27/2022] Open
Abstract
Myotubularin MTM1 is a phosphoinositide (PPIn) 3-phosphatase mutated in X-linked centronuclear myopathy (XLCNM; myotubular myopathy). We investigated the involvement of MTM1 enzymatic activity on XLCNM phenotypes. Exogenous expression of human MTM1 in yeast resulted in vacuolar enlargement, as a consequence of its phosphatase activity. Expression of mutants from patients with different clinical progression and determination of PtdIns3P and PtdIns5P cellular levels confirmed the link between vacuolar morphology and MTM1 phosphatase activity, and showed that some disease mutants retain phosphatase activity. Viral gene transfer of phosphatase-dead myotubularin mutants (MTM1(C375S) and MTM1(S376N)) significantly improved most histological signs of XLCNM displayed by a Mtm1-null mouse, at similar levels as wild-type MTM1. Moreover, the MTM1(C375S) mutant improved muscle performance and restored the localization of nuclei, triad alignment, and the desmin intermediate filament network, while it did not normalize PtdIns3P levels, supporting phosphatase-independent roles of MTM1 in maintaining normal muscle performance and organelle positioning in skeletal muscle. Among the different XLCNM signs investigated, we identified only triad shape and fiber size distribution as being partially dependent on MTM1 phosphatase activity. In conclusion, this work uncovers MTM1 roles in the structural organization of muscle fibers that are independent of its enzymatic activity. This underlines that removal of enzymes should be used with care to conclude on the physiological importance of their activity.
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MESH Headings
- Animals
- Desmin/metabolism
- Disease Models, Animal
- Enzyme Activation/genetics
- Gene Expression
- Humans
- Male
- Mice
- Mice, Knockout
- Muscle Strength/genetics
- Muscle, Skeletal/metabolism
- Muscle, Skeletal/pathology
- Muscle, Skeletal/ultrastructure
- Mutation
- Myopathies, Structural, Congenital/genetics
- Myopathies, Structural, Congenital/metabolism
- Phenotype
- Phosphatidylinositol Phosphates/metabolism
- Phosphoric Monoester Hydrolases/metabolism
- Protein Tyrosine Phosphatases, Non-Receptor/genetics
- Protein Tyrosine Phosphatases, Non-Receptor/metabolism
- Saccharomyces cerevisiae/genetics
- Saccharomyces cerevisiae/metabolism
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Affiliation(s)
- Leonela Amoasii
- Department of Translational Medecine, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), INSERM U964, CNRS UMR7104, Université de Strasbourg, Collège de France, Illkirch, France
| | - Dimitri L. Bertazzi
- Department of Molecular and Cellular Genetics, UMR7156, Université de Strasbourg and CNRS, Strasbourg, France
| | | | - Karim Hnia
- Department of Translational Medecine, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), INSERM U964, CNRS UMR7104, Université de Strasbourg, Collège de France, Illkirch, France
| | - Gaëtan Chicanne
- INSERM, U1048 and Université Toulouse 3, I2MC, Toulouse, France
| | - Bruno Rinaldi
- Department of Molecular and Cellular Genetics, UMR7156, Université de Strasbourg and CNRS, Strasbourg, France
| | - Belinda S. Cowling
- Department of Translational Medecine, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), INSERM U964, CNRS UMR7104, Université de Strasbourg, Collège de France, Illkirch, France
| | - Arnaud Ferry
- UMRS974, Université Pierre et Marie Curie, Paris, France
| | - Bruno Klaholz
- Department of Integrated Structural Biology, IGBMC, INSERM U964, CNRS UMR7104, Université de Strasbourg, Illkirch, France
| | - Bernard Payrastre
- INSERM, U1048 and Université Toulouse 3, I2MC, Toulouse, France
- CHU de Toulouse, Laboratoire d'Hématologie, Toulouse, France
- * E-mail: (SF); (JL); (BP)
| | - Jocelyn Laporte
- Department of Translational Medecine, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), INSERM U964, CNRS UMR7104, Université de Strasbourg, Collège de France, Illkirch, France
- * E-mail: (SF); (JL); (BP)
| | - Sylvie Friant
- Department of Molecular and Cellular Genetics, UMR7156, Université de Strasbourg and CNRS, Strasbourg, France
- * E-mail: (SF); (JL); (BP)
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25
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Phosphatidylinositol-4,5-bisphosphate ionization and domain formation in the presence of lipids with hydrogen bond donor capabilities. Chem Phys Lipids 2012; 165:696-704. [DOI: 10.1016/j.chemphyslip.2012.07.003] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2012] [Revised: 07/06/2012] [Accepted: 07/07/2012] [Indexed: 01/29/2023]
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26
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Hille B. Diversity of phosphoinositide signaling. BIOCHEMISTRY MOSCOW SUPPLEMENT SERIES A-MEMBRANE AND CELL BIOLOGY 2012. [DOI: 10.1134/s1990747812010059] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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27
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Lohse MJ, Nuber S, Hoffmann C. Fluorescence/bioluminescence resonance energy transfer techniques to study G-protein-coupled receptor activation and signaling. Pharmacol Rev 2012; 64:299-336. [PMID: 22407612 DOI: 10.1124/pr.110.004309] [Citation(s) in RCA: 251] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Fluorescence and bioluminescence resonance energy transfer (FRET and BRET) techniques allow the sensitive monitoring of distances between two labels at the nanometer scale. Depending on the placement of the labels, this permits the analysis of conformational changes within a single protein (for example of a receptor) or the monitoring of protein-protein interactions (for example, between receptors and G-protein subunits). Over the past decade, numerous such techniques have been developed to monitor the activation and signaling of G-protein-coupled receptors (GPCRs) in both the purified, reconstituted state and in intact cells. These techniques span the entire spectrum from ligand binding to the receptors down to intracellular second messengers. They allow the determination and the visualization of signaling processes with high temporal and spatial resolution. With these techniques, it has been demonstrated that GPCR signals may show spatial and temporal patterning. In particular, evidence has been provided for spatial compartmentalization of GPCRs and their signals in intact cells and for distinct physiological consequences of such spatial patterning. We review here the FRET and BRET technologies that have been developed for G-protein-coupled receptors and their signaling proteins (G-proteins, effectors) and the concepts that result from such experiments.
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Affiliation(s)
- Martin J Lohse
- Institute of Pharmacology and Toxicology, Versbacher Str. 9, 97078 Würzburg, Germany.
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28
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Tóth DJ, Tóth JT, Gulyás G, Balla A, Balla T, Hunyady L, Várnai P. Acute depletion of plasma membrane phosphatidylinositol 4,5-bisphosphate impairs specific steps in endocytosis of the G-protein-coupled receptor. J Cell Sci 2012; 125:2185-97. [PMID: 22357943 DOI: 10.1242/jcs.097279] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Receptor endocytosis plays an important role in regulating the responsiveness of cells to specific ligands. Phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P(2)] has been shown to be crucial for endocytosis of some cell surface receptors, such as EGF and transferrin receptors, but its role in G-protein-coupled receptor internalization has not been investigated. By using luciferase-labeled type 1 angiotensin II (AT1R), type 2C serotonin (5HT2CR) or β(2) adrenergic (β2AR) receptors and fluorescently tagged proteins (β-arrestin-2, plasma-membrane-targeted Venus, Rab5) we were able to follow the sequence of molecular interactions along the endocytic route of the receptors in HEK293 cells using the highly sensitive method of bioluminescence resonance energy transfer and confocal microscopy. To study the role of plasma membrane PtdIns(4,5)P(2) in receptor endocytosis, we used our previously developed rapamycin-inducible heterodimerization system, in which the recruitment of a 5-phosphatase domain to the plasma membrane degrades PtdIns(4,5)P(2). Here we show that ligand-induced interaction of AT1, 5HT2C and β(2)A receptors with β-arrestin-2 was unaffected by PtdIns(4,5)P(2) depletion. However, trafficking of the receptors to Rab5-positive early endosomes was completely abolished in the absence of PtdIns(4,5)P(2). Remarkably, removal of the receptors from the plasma membrane was reduced but not eliminated after PtdIns(4,5)P(2) depletion. Under these conditions, stimulated AT1 receptors clustered along the plasma membrane, but did not enter the cells. Our data suggest that in the absence of PtdIns(4,5)P(2), these receptors move into clathrin-coated membrane structures, but these are not cleaved efficiently and hence cannot reach the early endosomal compartment.
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Affiliation(s)
- Dániel J Tóth
- Department of Physiology, Semmelweis University, Faculty of Medicine, Budapest, Hungary
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29
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Chang-Ileto B, Frere SG, Di Paolo G. Acute manipulation of phosphoinositide levels in cells. Methods Cell Biol 2012; 108:187-207. [PMID: 22325604 DOI: 10.1016/b978-0-12-386487-1.00010-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Phosphoinositides are membrane-bound signaling phospholipids that function in a myriad of cellular processes, including membrane trafficking, cytoskeletal dynamics, ion channel and transporter function, and signal transduction. In order to better understand the role of phosphoinositides in cellular processes, different approaches to study the effects of the presence or absence of these lipids must be devised. Conventional approaches of manipulating phosphoinositide levels such as over-expression or genetic ablation of lipid enzymes cause prolonged exposure of the cells to changes in lipid levels that could result in compensatory actions by the cell or downstream alterations in cell physiology. In this chapter we present an approach used recently by various laboratories, including our own, to acutely manipulate phosphoinositide levels at target locations using chemically induced dimerization (CID) that can be spatially and temporally controlled. We discuss considerations when designing expression constructs for targeting specific cellular compartment membranes and present examples from the literature on different ways of perturbing phosphoinositide levels at particular organelle membranes using CID. In addition, we provide details on image acquisition, data collection, and data interpretation. CID technology can be applied to many lipid enzymes to broaden the understanding of the role lipid signaling plays in cell physiology.
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Affiliation(s)
- Belle Chang-Ileto
- Department of Pathology and Cell Biology, Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Columbia University Medical Center, New York, USA
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30
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Sellin ME, Holmfeldt P, Stenmark S, Gullberg M. Microtubules support a disk-like septin arrangement at the plasma membrane of mammalian cells. Mol Biol Cell 2011; 22:4588-601. [PMID: 21998205 PMCID: PMC3226477 DOI: 10.1091/mbc.e11-09-0754] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Septin assemblies during the interphase of animal cells remain poorly defined and are the topic of this report. The data point to a general model for assembly of higher-order septin arrangements at locations providing the greatest opportunity for binding cooperativity, which depends on both the cell type and external cues. Septin family proteins oligomerize through guanosine 5′-triphosphate–binding domains into core heteromers, which in turn polymerize at the cleavage furrow of dividing fungal and animal cells. Septin assemblies during the interphase of animal cells remain poorly defined and are the topic of this report. In this study, we developed protocols for visualization of authentic higher-order assemblies using tagged septins to effectively replace the endogenous gene product within septin core heteromers in human cells. Our analysis revealed that septins assemble into microtubule-supported, disk-like structures at the plasma membrane. In the absence of cell substrate adhesion, this is the predominant higher-order arrangement in interphase cells and each of the seven to eight septin family members expressed by the two analyzed cell types appears equally represented. However, studies of myeloid and lymphoid cell model systems revealed cell type–specific alterations of higher-order septin arrangements in response to substrate adhesion. Live-cell observations suggested that all higher-order septin assemblies are mutually exclusive with plasma membrane regions undergoing remodeling. The combined data point to a mechanism by which densely arranged cortical microtubules, which are typical for nonadhered spherical cells, support plasma membrane–bound, disk-like septin assemblies.
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Affiliation(s)
- Mikael E Sellin
- Department of Molecular Biology, Umeå University, SE-901 87 Umeå, Sweden.
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31
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Optical probing of a dynamic membrane interaction that regulates the TREK1 channel. Proc Natl Acad Sci U S A 2011; 108:2605-10. [PMID: 21262820 DOI: 10.1073/pnas.1015788108] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
TREK channels produce background currents that regulate cell excitability. These channels are sensitive to a wide variety of stimuli including polyunsaturated fatty acids (PUFAs), phospholipids, mechanical stretch, and intracellular acidification. They are inhibited by neurotransmitters, hormones, and pharmacological agents such as the antidepressant fluoxetine. TREK1 knockout mice have impaired PUFA-mediated neuroprotection to ischemia, reduced sensitivity to volatile anesthetics, altered perception of pain, and a depression-resistant phenotype. Here, we investigate TREK1 regulation by Gq-coupled receptors (GqPCR) and phospholipids. Several reports indicate that the C-terminal domain of TREK1 is a key regulatory domain. We developed a fluorescent-based technique that monitors the plasma membrane association of the C terminus of TREK1 in real time. Our fluorescence and functional experiments link the modulation of TREK1 channel function by internal pH, phospholipid, and GqPCRs to TREK1-C-terminal domain association to the plasma membrane, where increased association results in greater activity. In keeping with this relation, inhibition of TREK1 current by fluoxetine is found to be accompanied by dissociation of the C-terminal domain from the membrane.
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32
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Bohdanowicz M, Fairn GD. Rapamycin-based inducible translocation systems for studying phagocytosis. Methods Mol Biol 2011; 748:183-93. [PMID: 21701975 DOI: 10.1007/978-1-61779-139-0_13] [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: 12/12/2022]
Abstract
Phagocytosis is an immune receptor-mediated process whereby cells engulf large particles. The process is dynamic and requires several localized factors acting in concert with and sequentially after the engagement of immune receptors to envelope the particle. Once the particle is internalized, the nascent -phagosome undergoes a series of events leading to its maturation to the microbicidal phagolysosome. Investigating these dynamic and temporally controlled series of events in live cells requires noninvasive methods. The ability to rapidly recruit the proteins of interest to the sites of phagocytosis or to nascent phagosomes would help dissect the regulatory mechanisms involved during phagocytosis. Here, we describe a general approach to express in RAW264.7 murine macrophages, a genetically encoded rapamycin--induced heterodimerization system. In the presence of rapamycin, tight association between FK506-binding protein (FKBP) and FKBP rapamycin-binding protein (FRB) is observed. Based on this principle, a synthetic system consisting of a targeting domain attached to FKBP can recruit a protein of interest fused to FRB upon the addition of rapamycin. Previously, this technique has been used to target lipid-modifying enzymes and small GTPases to the phagosome or plasma membrane. The recruitment of the FRB module can be monitored by fluorescent microscopy if a fluorescent protein is fused to the FRB sequence. While the focus of this chapter is on phagocytic events, this method can be employed to study any organelle of interest when the appropriate targeting sequence is used.
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Affiliation(s)
- Michal Bohdanowicz
- Program in Cell Biology, The Hospital for Sick Children,Toronto, Ontario, Canada
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Balla A, Erdélyi LS, Soltész-Katona E, Balla T, Várnai P, Hunyady L. Demonstration of angiotensin II-induced Ras activation in the trans-Golgi network and endoplasmic reticulum using bioluminescence resonance energy transfer-based biosensors. J Biol Chem 2010; 286:5319-27. [PMID: 21062747 DOI: 10.1074/jbc.m110.176933] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Previous studies have demonstrated that molecules of the Ras signaling pathway are present in intracellular compartments, including early endosomes, the endoplasmic reticulum (ER), and the Golgi, and suggested that mitogens can regulate Ras activity in these endomembranes. In this study, we investigated the effect of angiotensin II (AngII) on intracellular Ras activity in living HEK293 cells expressing angiotensin type 1 receptors (AT(1)-Rs) using newly developed bioluminescence resonance energy transfer biosensors. To investigate the subcellular localization of AngII-induced Ras activation, we targeted our probes to various intracellular compartments, such as the trans-Golgi network (TGN), the ER, and early endosomes. Using these biosensors, we detected AngII-induced Ras activation in the TGN and ER, but not in early endosomes. In cells expressing a cytoplasmic tail deletion AT(1)-R mutant, the AngII-induced response was enhanced, suggesting that receptor internalization and β-arrestin binding are not required for AngII-induced Ras activation in endomembranes. Although we were able to demonstrate EGF-induced Ras activation in the plasma membrane and TGN, but not in other endomembranes, AG1478, an EGF receptor inhibitor, did not affect the AngII-induced response, suggesting that the latter is independent of EGF receptor transactivation. AngII was unable to stimulate Ras activity in the studied compartments in cells expressing a G protein coupling-deficient AT(1)-R mutant ((125)DRY(127) to (125)AAY(127)). These data suggest that AngII can stimulate Ras activity in the TGN and ER with a G protein-dependent mechanism, which does not require β-arrestin-mediated signaling, receptor internalization, and EGF receptor transactivation.
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Affiliation(s)
- András Balla
- Department of Physiology, Faculty of Medicine, Semmelweis University, H-1444 Budapest, Hungary
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Csordás G, Várnai P, Golenár T, Roy S, Purkins G, Schneider TG, Balla T, Hajnóczky G. Imaging interorganelle contacts and local calcium dynamics at the ER-mitochondrial interface. Mol Cell 2010; 39:121-32. [PMID: 20603080 DOI: 10.1016/j.molcel.2010.06.029] [Citation(s) in RCA: 555] [Impact Index Per Article: 39.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2009] [Revised: 04/09/2010] [Accepted: 06/14/2010] [Indexed: 12/11/2022]
Abstract
The ER-mitochondrial junction provides a local calcium signaling domain that is critical for both matching energy production with demand and the control of apoptosis. Here, we visualize ER-mitochondrial contact sites and monitor the localized [Ca(2+)] changes ([Ca(2+)](ER-mt)) using drug-inducible fluorescent interorganelle linkers. We show that all mitochondria have contacts with the ER, but plasma membrane (PM)-mitochondrial contacts are less frequent because of interleaving ER stacks in both RBL-2H3 and H9c2 cells. Single mitochondria display discrete patches of ER contacts and show heterogeneity in the ER-mitochondrial Ca(2+) transfer. Pericam-tagged linkers revealed IP(3)-induced [Ca(2+)](ER-mt) signals that exceeded 9 microM and endured buffering bulk cytoplasmic [Ca(2+)] increases. Altering linker length to modify the space available for the Ca(2+) transfer machinery had a biphasic effect on [Ca(2+)](ER-mt) signals. These studies provide direct evidence for the existence of high-Ca(2+) microdomains between the ER and mitochondria and suggest an optimal gap width for efficient Ca(2+) transfer.
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Affiliation(s)
- György Csordás
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA
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Falkenburger BH, Jensen JB, Dickson EJ, Suh BC, Hille B. Phosphoinositides: lipid regulators of membrane proteins. J Physiol 2010; 588:3179-85. [PMID: 20519312 DOI: 10.1113/jphysiol.2010.192153] [Citation(s) in RCA: 163] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Phosphoinositides are a family of minority acidic phospholipids in cell membranes. Their principal role is instructional: they interact with proteins. Each cellular membrane compartment uses a characteristic species of phosphoinositide. This signature phosphoinositide attracts a specific complement of functionally important, loosely attached peripheral proteins to that membrane. For example, the phosphatidylinositol 4,5-bisphosphate (PIP(2)) of the plasma membrane attracts phospholipase C, protein kinase C, proteins involved in membrane budding and fusion, proteins regulating the actin cytoskeleton, and others. Phosphoinositides also regulate the activity level of the integral membrane proteins. Many ion channels of the plasma membrane need the plasma-membrane-specific PIP(2) to function. Their activity decreases when the abundance of this lipid falls, as for example after activation of phospholipase C. This behaviour is illustrated by the suppression of KCNQ K(+) channel current by activation of M(1) muscarinic receptors; KCNQ channels require PIP(2) for their activity. In summary, phosphoinositides contribute to the selection of peripheral proteins for each membrane and regulate the activity of the integral proteins.
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Affiliation(s)
- Björn H Falkenburger
- University of Washington School of Medicine, Department of Physiology and Biophysics, Campus Box 357290, 1705 NE Pacific Street, Room G424 Health Sciences Bldg, Seattle, WA 98195-7290, USA
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Pals1 is a major regulator of the epithelial-like polarization and the extension of the myelin sheath in peripheral nerves. J Neurosci 2010; 30:4120-31. [PMID: 20237282 DOI: 10.1523/jneurosci.5185-09.2010] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Diameter, organization, and length of the myelin sheath are important determinants of the nerve conduction velocity, but the basic molecular mechanisms that control these parameters are only partially understood. Cell polarization is an essential feature of differentiated cells, and relies on a set of evolutionarily conserved cell polarity proteins. We investigated the molecular nature of myelin sheath polarization in connection with the functional role of the cell polarity protein pals1 (Protein Associated with Lin Seven 1) during peripheral nerve myelin sheath extension. We found that, in regard to epithelial polarity, the Schwann cell outer abaxonal domain represents a basolateral-like domain, while the inner adaxonal domain and Schmidt-Lanterman incisures form an apical-like domain. Silencing of pals1 in myelinating Schwann cells in vivo resulted in a severe reduction of myelin sheath thickness and length. Except for some infoldings, the structure of compact myelin was not fundamentally affected, but cells produced less myelin turns. In addition, pals1 is required for the normal polarized localization of the vesicular markers sec8 and syntaxin4, and for the distribution of E-cadherin and myelin proteins PMP22 and MAG at the plasma membrane. Our data show that the polarity protein pals1 plays an essential role in the radial and longitudinal extension of the myelin sheath, likely involving a functional role in membrane protein trafficking. We conclude that regulation of epithelial-like polarization is a critical determinant of myelin sheath structure and function.
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Dippold HC, Ng MM, Farber-Katz SE, Lee SK, Kerr ML, Peterman MC, Sim R, Wiharto PA, Galbraith KA, Madhavarapu S, Fuchs GJ, Meerloo T, Farquhar MG, Zhou H, Field SJ. GOLPH3 bridges phosphatidylinositol-4- phosphate and actomyosin to stretch and shape the Golgi to promote budding. Cell 2009; 139:337-51. [PMID: 19837035 DOI: 10.1016/j.cell.2009.07.052] [Citation(s) in RCA: 471] [Impact Index Per Article: 31.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2008] [Revised: 04/13/2009] [Accepted: 07/31/2009] [Indexed: 11/15/2022]
Abstract
Golgi membranes, from yeast to humans, are uniquely enriched in phosphatidylinositol-4-phosphate (PtdIns(4)P), although the role of this lipid remains poorly understood. Using a proteomic lipid-binding screen, we identify the Golgi protein GOLPH3 (also called GPP34, GMx33, MIDAS, or yeast Vps74p) as a PtdIns(4)P-binding protein that depends on PtdIns(4)P for its Golgi localization. We further show that GOLPH3 binds the unconventional myosin MYO18A, thus connecting the Golgi to F-actin. We demonstrate that this linkage is necessary for normal Golgi trafficking and morphology. The evidence suggests that GOLPH3 binds to PtdIns(4)P-rich trans-Golgi membranes and MYO18A conveying a tensile force required for efficient tubule and vesicle formation. Consequently, this tensile force stretches the Golgi into the extended ribbon observed by fluorescence microscopy and the familiar flattened form observed by electron microscopy.
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Affiliation(s)
- Holly C Dippold
- Division of Endocrinology and Metabolism, Department of Medicine, University of California, San Diego, La Jolla, CA 92093-0707, USA
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Phosphatidylinositol 4,5-bisphosphate-dependent interaction of myelin basic protein with the plasma membrane in oligodendroglial cells and its rapid perturbation by elevated calcium. J Neurosci 2009; 29:4794-807. [PMID: 19369548 DOI: 10.1523/jneurosci.3955-08.2009] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Myelin basic protein (MBP) is an essential structural component of CNS myelin. The electrostatic association of this positively charged protein with myelin-forming membranes is a crucial step in myelination, but the mechanism that regulates myelin membrane targeting is not known. Here, we demonstrate that phosphatidylinositol 4,5-bisphosphate (PIP2) is important for the stable association of MBP with cellular membranes. In oligodendrocytes, overexpression of synaptojanin 1-derived phosphoinositide 5-phosphatase, which selectively hydrolyzes membrane PIP2, causes the detachment of MBP from the plasma membrane. In addition, constitutively active Arf6/Q67L induces the formation of PIP2-enriched endosomal vacuoles, leading to the redistribution of MBP to intracellular vesicles. Fluorescence resonance energy transfer imaging revealed an interaction of the PIP2 sensing probe PH-PLCdelta1 with wild-type MBP, but not with a mutant MBP isoform that fails to associate with the plasma membrane. Moreover, increasing intracellular Ca(2+), followed by phospholipase C-mediated PIP2 hydrolysis, as well as reduction of the membrane charge by ATP depletion, resulted in the dissociation of MBP from the glial plasma membrane. When the corpus callosum of mice was analyzed in acute brain slices by electron microscopy, the reduction of membrane surface charge led to the loss of myelin compaction and rapid vesiculation. Together, these results establish that PIP2 is an essential determinant for stable membrane binding of MBP and provide a novel link between glial phosphoinositol metabolism and MBP function in development and disease.
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Sample V, Newman RH, Zhang J. The structure and function of fluorescent proteins. Chem Soc Rev 2009; 38:2852-64. [DOI: 10.1039/b913033k] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Thole JM, Vermeer JEM, Zhang Y, Gadella TWJ, Nielsen E. Root hair defective4 encodes a phosphatidylinositol-4-phosphate phosphatase required for proper root hair development in Arabidopsis thaliana. THE PLANT CELL 2008; 20:381-95. [PMID: 18281508 PMCID: PMC2276440 DOI: 10.1105/tpc.107.054304] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Polarized expansion of root hair cells in Arabidopsis thaliana is improperly controlled in root hair-defective rhd4-1 mutant plants, resulting in root hairs that are shorter and randomly form bulges along their length. Using time-lapse fluorescence microscopy in rhd4-1 root hairs, we analyzed membrane dynamics after labeling with RabA4b, a marker for polarized membrane trafficking in root hairs. This revealed stochastic loss and recovery of the RabA4b compartment in the tips of growing root hairs, consistent with a role for the RHD4 protein in regulation of polarized membrane trafficking in these cells. The wild-type RHD4 gene was identified by map-based cloning and was found to encode a Sac1p-like phosphoinositide phosphatase. RHD4 displayed a preference for phosphatidylinositol-4-phosphate [PI(4)P] in vitro, and rhd4-1 roots accumulated higher levels of PI(4)P in vivo. In wild-type root hairs, PI(4)P accumulated primarily in a tip-localized plasma membrane domain, but in rhd4-1 mutants, significant levels of PI(4)P were detected associated with internal membranes. A fluorescent RHD4 fusion protein localized to membranes at the tips of growing root hairs. We propose that RHD4 is selectively recruited to RabA4b-labeled membranes that are involved in polarized expansion of root hair cells and that, in conjunction with the phosphoinositide kinase PI-4Kbeta1, RHD4 regulates the accumulation of PI(4)P on membrane compartments at the tips of growing root hairs.
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Affiliation(s)
- Julie M Thole
- Department of Biology, Washington University, St. Louis, Missouri 63130, USA
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Suzuki T, Matsuzaki T, Hagiwara H, Aoki T, Takata K. Recent advances in fluorescent labeling techniques for fluorescence microscopy. Acta Histochem Cytochem 2007; 40:131-7. [PMID: 18224244 PMCID: PMC2156041 DOI: 10.1267/ahc.07023] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2007] [Accepted: 11/13/2007] [Indexed: 01/19/2023] Open
Abstract
Tremendous progress in recent computer-controlled systems for fluorescence and laser-confocal microscopy has provided us with powerful tools to visualize and analyze molecular events in the cells. Various fluorescent staining and labeling techniques have also been developed to be used with these powerful instruments. Fluorescent proteins such as green fluorescent protein (GFP) allow us to directly label particular proteins of interest in living cells. This technique has been extended over a large area of cell biology, and a variety of fluorescent protein-derived techniques have been developed to visualize the functions and conditions of the molecules within living cells. In this review, we summarize the techniques for fluorescent staining and labeling for recent fluorescence microscopy.
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Affiliation(s)
- Takeshi Suzuki
- Department of Anatomy and Cell Biology, Gunma University Graduate School of Medicine, Maebashi, Gunma 371–8511, Japan
| | - Toshiyuki Matsuzaki
- Department of Anatomy and Cell Biology, Gunma University Graduate School of Medicine, Maebashi, Gunma 371–8511, Japan
| | - Haruo Hagiwara
- Department of Anatomy and Cell Biology, Gunma University Graduate School of Medicine, Maebashi, Gunma 371–8511, Japan
| | - Takeo Aoki
- Department of Anatomy and Cell Biology, Gunma University Graduate School of Medicine, Maebashi, Gunma 371–8511, Japan
| | - Kuniaki Takata
- Department of Anatomy and Cell Biology, Gunma University Graduate School of Medicine, Maebashi, Gunma 371–8511, Japan
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