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Mizejewski GJ. The Role of Ion Channels and Chemokines in Cancer Growth and Metastasis: A Proposed Mode of Action Using Peptides in Cancer Therapy. Cancers (Basel) 2024; 16:1531. [PMID: 38672613 PMCID: PMC11048196 DOI: 10.3390/cancers16081531] [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: 01/22/2024] [Revised: 04/12/2024] [Accepted: 04/12/2024] [Indexed: 04/28/2024] Open
Abstract
Metastasis (Met) largely contributes to the major cause of cancer deaths throughout the world, rather than the growth of the tumor mass itself. The present report brings together several of the pertinent contributors to cancer growth and metastatic processes from an activity standpoint. Such biological activities include the following: (1) cell adherence and detachment; (2) cell-to-cell contact; (3) contact inhibition; (4) the cell interfacing with the extracellular matrix (ECM); (5) tumor cell-to-stroma communication networks; (6) chemotaxis; and (7) cell membrane potential. Moreover, additional biochemical factors that contribute to cancer growth and metastasis have been shown to comprise the following: (a) calcium levels in the extracellular matrix and in intracellular compartments; (b) cation voltage and ATP-regulated potassium channels; (c) selective and non-selective cation channels; and (d) chemokines (cytokines) and their receptors, such as CXCL12 (SDF-1) and its receptor/binding partner, CXCR4. These latter molecular components represent a promising group of an interacting and synchronized set of candidates ideal for peptide therapeutic targeting for cancer growth and metastasis. Such peptides can be obtained from naturally occurring proteins such as alpha-fetoprotein (AFP), an onco-fetal protein and clinical biomarker.
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Affiliation(s)
- Gerald J. Mizejewski
- Division of Translational Medicine, Molecular Diagnostics Laboratory, Albany, NY 12201, USA; ; Tel.: +518-486-5900; Fax: +518-402-5002
- Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY 12201, USA
- Biggs Laboratory, Empire State Plaza, Albany, NY 12237, USA
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2
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Liu Y, Ma Y, Xu J, Zhang G, Zhao X, He Z, Wang L, Yin N, Peng M. VMP1 prevents Ca2+ overload in endoplasmic reticulum and maintains naive T cell survival. J Exp Med 2023; 220:e20221068. [PMID: 36971758 PMCID: PMC10060355 DOI: 10.1084/jem.20221068] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2022] [Revised: 01/11/2023] [Accepted: 03/10/2023] [Indexed: 03/29/2023] Open
Abstract
Ca2+ in endoplasmic reticulum (ER) dictates T cell activation, proliferation, and function via store-operated Ca2+ entry. How naive T cells maintain an appropriate level of Ca2+ in ER remains poorly understood. Here, we show that the ER transmembrane protein VMP1 is essential for maintaining ER Ca2+ homeostasis in naive T cells. VMP1 promotes Ca2+ release from ER under steady state, and its deficiency leads to ER Ca2+ overload, ER stress, and secondary Ca2+ overload in mitochondria, resulting in massive apoptosis of naive T cells and defective T cell response. Aspartic acid 272 (D272) of VMP1 is critical for its ER Ca2+ releasing activity, and a knockin mouse strain with D272 mutated to asparagine (D272N) demonstrates all functions of VMP1 in T cells in vivo depend on its regulation of ER Ca2+. These data uncover an indispensable role of VMP1 in preventing ER Ca2+ overload and maintaining naive T cell survival.
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Affiliation(s)
- Ying Liu
- Department of Basic Medical Sciences, School of Medicine, Tsinghua University, Beijing, China
- Institute for Immunology, Tsinghua University, Beijing, China
| | - Yuying Ma
- Department of Basic Medical Sciences, School of Medicine, Tsinghua University, Beijing, China
- Institute for Immunology, Tsinghua University, Beijing, China
| | - Jing Xu
- Department of Basic Medical Sciences, School of Medicine, Tsinghua University, Beijing, China
- Institute for Immunology, Tsinghua University, Beijing, China
| | - Guangyue Zhang
- Department of Basic Medical Sciences, School of Medicine, Tsinghua University, Beijing, China
- Institute for Immunology, Tsinghua University, Beijing, China
- Tsinghua-Peking Center for Life Sciences, Beijing, China
| | - Xiaocui Zhao
- Department of Basic Medical Sciences, School of Medicine, Tsinghua University, Beijing, China
- Institute for Immunology, Tsinghua University, Beijing, China
- Tsinghua-Peking Center for Life Sciences, Beijing, China
| | - Zihao He
- Department of Basic Medical Sciences, School of Medicine, Tsinghua University, Beijing, China
- Institute for Immunology, Tsinghua University, Beijing, China
| | - Lixia Wang
- Department of Basic Medical Sciences, School of Medicine, Tsinghua University, Beijing, China
- Institute for Immunology, Tsinghua University, Beijing, China
- Tsinghua-Peking Center for Life Sciences, Beijing, China
| | - Na Yin
- Department of Basic Medical Sciences, School of Medicine, Tsinghua University, Beijing, China
- Institute for Immunology, Tsinghua University, Beijing, China
| | - Min Peng
- Department of Basic Medical Sciences, School of Medicine, Tsinghua University, Beijing, China
- Institute for Immunology, Tsinghua University, Beijing, China
- Tsinghua-Peking Center for Life Sciences, Beijing, China
- Beijing Key Laboratory for Immunological Research on Chronic Diseases, Tsinghua University, Beijing, China
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3
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Parys JB, Van Coppenolle F. Sec61 complex/translocon: The role of an atypical ER Ca 2+-leak channel in health and disease. Front Physiol 2022; 13:991149. [PMID: 36277220 PMCID: PMC9582130 DOI: 10.3389/fphys.2022.991149] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Accepted: 09/20/2022] [Indexed: 11/02/2023] Open
Abstract
The heterotrimeric Sec61 protein complex forms the functional core of the so-called translocon that forms an aqueous channel in the endoplasmic reticulum (ER). The primary role of the Sec61 complex is to allow protein import in the ER during translation. Surprisingly, a completely different function in intracellular Ca2+ homeostasis has emerged for the Sec61 complex, and the latter is now accepted as one of the major Ca2+-leak pathways of the ER. In this review, we first discuss the structure of the Sec61 complex and focus on the pharmacology and regulation of the Sec61 complex as a Ca2+-leak channel. Subsequently, we will pay particular attention to pathologies that are linked to Sec61 mutations, such as plasma cell deficiency and congenital neutropenia. Finally, we will explore the relevance of the Sec61 complex as a Ca2+-leak channel in various pathophysiological (ER stress, apoptosis, ischemia-reperfusion) and pathological (type 2 diabetes, cancer) settings.
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Affiliation(s)
- Jan B. Parys
- Laboratory for Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine & Leuven Kanker Instituut, KU Leuven, Leuven, Belgium
| | - Fabien Van Coppenolle
- CarMeN Laboratory, INSERM, INRA, INSA Lyon, Université Claude Bernard Lyon 1, Lyon, France
- Groupement Hospitalier EST, Department of Cardiology, Hospices Civils de Lyon, Lyon, France
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4
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Dagnino-Acosta A, Guerrero-Hernandez A. PKC Inhibits Sec61 Translocon-Mediated Sarcoplasmic Reticulum Ca2+ Leak in Smooth Muscle Cells. Front Physiol 2022; 13:925023. [PMID: 35837019 PMCID: PMC9275787 DOI: 10.3389/fphys.2022.925023] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Accepted: 06/03/2022] [Indexed: 01/13/2023] Open
Abstract
PKC inhibitors stimulate Ca2+ release from internal stores in diverse cell types. Our data indicate that this action cannot be explained by an increased agonist-induced IP3 production or an overloaded SR Ca2+ pool in smooth muscle cells from guinea pig urinary bladder. The incubation of these cells with three different PKC inhibitors, such as Go6976, Go6983, and BIM 1, resulted in a higher SR Ca2+ leak revealed by inhibition of the SERCA pump with thapsigargin. This SR Ca2+ leakage was sensitive to protein translocation inhibitors such as emetine and anisomycin. Since this increased SR Ca2+ leak did not result in a depleted SR Ca2+ store, we have inferred there was a compensatory increase in SERCA pump activity, resulting in a higher steady-state. This new steady-state increased the frequency of Spontaneous Transient Outward Currents (STOCs), which reflect the activation of high conductance, Ca2+-sensitive potassium channels in response to RyR-mediated Ca2+ sparks. This increased STOC frequency triggered by PKC inhibition was restored to normal by inhibiting translocon-mediated Ca2+ leak with emetine. These results suggest a critical role of PKC-mediated translocon phosphorylation in regulating SR Ca2+ steady-state, which, in turn, alters SR Ca2+ releasing activity.
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Affiliation(s)
- Adan Dagnino-Acosta
- Centro Universitario de Investigaciones Biomédicas, CONACYT-Universidad de Colima, Colima, Mexico
| | - Agustín Guerrero-Hernandez
- Departamento de Bioquímica, Centro de Investigación y de Estudios Avanzados, Mexico City, Mexico
- *Correspondence: Agustín Guerrero-Hernandez,
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Pick T, Beck A, Gamayun I, Schwarz Y, Schirra C, Jung M, Krause E, Niemeyer BA, Zimmermann R, Lang S, Anken EV, Cavalié A. Remodelling of Ca 2+ homeostasis is linked to enlarged endoplasmic reticulum in secretory cells. Cell Calcium 2021; 99:102473. [PMID: 34560367 DOI: 10.1016/j.ceca.2021.102473] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Revised: 08/27/2021] [Accepted: 09/08/2021] [Indexed: 11/30/2022]
Abstract
The endoplasmic reticulum (ER) is extensively remodelled during the development of professional secretory cells to cope with high protein production. Since ER is the principal Ca2+ store in the cell, we characterised the Ca2+ homeostasis in NALM-6 and RPMI 8226 cells, which are commonly used as human pre-B and antibody secreting plasma cell models, respectively. Expression levels of Sec61 translocons and the corresponding Sec61-mediated Ca2+ leak from ER, Ca2+ storage capacity and store-operated Ca2+ entry were significantly enlarged in the secretory RPMI 8226 cell line. Using an immunoglobulin M heavy chain producing HeLa cell model, we found that the enlarged Ca2+ storage capacity and Ca2+ leak from ER are linked to ER expansion. Our data delineates a developmental remodelling of Ca2+ homeostasis in professional secretory cells in which a high Sec61-mediated Ca2+ leak and, thus, a high Ca2+ turnover in the ER is backed up by enhanced store-operated Ca2+ entry.
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Affiliation(s)
- Tillman Pick
- Experimental and Clinical Pharmacology and Toxicology, Pre-clinical Center for Molecular Signalling (PZMS), Saarland University, 66421 Homburg, Germany.
| | - Andreas Beck
- Experimental and Clinical Pharmacology and Toxicology, Pre-clinical Center for Molecular Signalling (PZMS), Saarland University, 66421 Homburg, Germany
| | - Igor Gamayun
- Experimental and Clinical Pharmacology and Toxicology, Pre-clinical Center for Molecular Signalling (PZMS), Saarland University, 66421 Homburg, Germany
| | - Yvonne Schwarz
- Molecular Neurophysiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, 66421 Homburg, Germany
| | - Claudia Schirra
- Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, 66421 Homburg, Germany
| | - Martin Jung
- Medical Biochemistry and Molecular Biology, Pre-clinical Centre for Molecular Signalling (PZMS), Saarland University, 66421 Homburg, Germany
| | - Elmar Krause
- Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, 66421 Homburg, Germany
| | - Barbara A Niemeyer
- Molecular Biophysics, Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, 66421 Homburg, Germany
| | - Richard Zimmermann
- Medical Biochemistry and Molecular Biology, Pre-clinical Centre for Molecular Signalling (PZMS), Saarland University, 66421 Homburg, Germany
| | - Sven Lang
- Medical Biochemistry and Molecular Biology, Pre-clinical Centre for Molecular Signalling (PZMS), Saarland University, 66421 Homburg, Germany
| | - Eelco van Anken
- Division of Genetics and Cell Biology, San Raffaele Scientific Institute and Università Vita-Salute San Raffaele, Milan, Italy
| | - Adolfo Cavalié
- Experimental and Clinical Pharmacology and Toxicology, Pre-clinical Center for Molecular Signalling (PZMS), Saarland University, 66421 Homburg, Germany.
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Sicking M, Lang S, Bochen F, Roos A, Drenth JPH, Zakaria M, Zimmermann R, Linxweiler M. Complexity and Specificity of Sec61-Channelopathies: Human Diseases Affecting Gating of the Sec61 Complex. Cells 2021; 10:1036. [PMID: 33925740 PMCID: PMC8147068 DOI: 10.3390/cells10051036] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 04/15/2021] [Accepted: 04/17/2021] [Indexed: 12/14/2022] Open
Abstract
The rough endoplasmic reticulum (ER) of nucleated human cells has crucial functions in protein biogenesis, calcium (Ca2+) homeostasis, and signal transduction. Among the roughly one hundred components, which are involved in protein import and protein folding or assembly, two components stand out: The Sec61 complex and BiP. The Sec61 complex in the ER membrane represents the major entry point for precursor polypeptides into the membrane or lumen of the ER and provides a conduit for Ca2+ ions from the ER lumen to the cytosol. The second component, the Hsp70-type molecular chaperone immunoglobulin heavy chain binding protein, short BiP, plays central roles in protein folding and assembly (hence its name), protein import, cellular Ca2+ homeostasis, and various intracellular signal transduction pathways. For the purpose of this review, we focus on these two components, their relevant allosteric effectors and on the question of how their respective functional cycles are linked in order to reconcile the apparently contradictory features of the ER membrane, selective permeability for precursor polypeptides, and impermeability for Ca2+. The key issues are that the Sec61 complex exists in two conformations: An open and a closed state that are in a dynamic equilibrium with each other, and that BiP contributes to its gating in both directions in cooperation with different co-chaperones. While the open Sec61 complex forms an aqueous polypeptide-conducting- and transiently Ca2+-permeable channel, the closed complex is impermeable even to Ca2+. Therefore, we discuss the human hereditary and tumor diseases that are linked to Sec61 channel gating, termed Sec61-channelopathies, as disturbances of selective polypeptide-impermeability and/or aberrant Ca2+-permeability.
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Affiliation(s)
- Mark Sicking
- Department of Medical Biochemistry & Molecular Biology, Saarland University, D-66421 Homburg, Germany;
| | - Sven Lang
- Department of Medical Biochemistry & Molecular Biology, Saarland University, D-66421 Homburg, Germany;
| | - Florian Bochen
- Department of Otorhinolaryngology, Head and Neck Surgery, Saarland University Medical Center, D-66421 Homburg, Germany; (F.B.); (M.L.)
| | - Andreas Roos
- Department of Neuropediatrics, Essen University Hospital, D-45147 Essen, Germany;
| | - Joost P. H. Drenth
- Department of Molecular Gastroenterology and Hepatology, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands;
| | - Muhammad Zakaria
- Department of Genetics, Hazara University, Mansehra 21300, Pakistan;
| | - Richard Zimmermann
- Department of Medical Biochemistry & Molecular Biology, Saarland University, D-66421 Homburg, Germany;
| | - Maximilian Linxweiler
- Department of Otorhinolaryngology, Head and Neck Surgery, Saarland University Medical Center, D-66421 Homburg, Germany; (F.B.); (M.L.)
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7
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Al-Mawla R, Ducrozet M, Tessier N, Païta L, Pillot B, Gouriou Y, Villedieu C, Harhous Z, Paccalet A, Crola Da Silva C, Ovize M, Bidaux G, Ducreux S, Van Coppenolle F. Acute Induction of Translocon-Mediated Ca 2+ Leak Protects Cardiomyocytes Against Ischemia/Reperfusion Injury. Cells 2020; 9:cells9051319. [PMID: 32466308 PMCID: PMC7290748 DOI: 10.3390/cells9051319] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 05/14/2020] [Accepted: 05/21/2020] [Indexed: 12/13/2022] Open
Abstract
During myocardial infarction, dysregulation of Ca2+ homeostasis between the reticulum, mitochondria, and cytosol occurs in cardiomyocytes and leads to cell death. Ca2+ leak channels are thought to be key regulators of the reticular Ca2+ homeostasis and cell survival. The present study aimed to determine whether a particular reticular Ca2+ leak channel, the translocon, also known as translocation channel, could be a relevant target against ischemia/reperfusion-mediated heart injury. To achieve this objective, we first used an intramyocardial adenoviral strategy to express biosensors in order to assess Ca2+ variations in freshly isolated adult mouse cardiomyocytes to show that translocon is a functional reticular Ca2+ leak channel. Interestingly, translocon activation by puromycin mobilized a ryanodine receptor (RyR)-independent reticular Ca2+ pool and did not affect the excitation–concentration coupling. Second, puromycin pretreatment decreased mitochondrial Ca2+ content and slowed down the mitochondrial permeability transition pore (mPTP) opening and the rate of cytosolic Ca2+ increase during hypoxia. Finally, this translocon pre-activation also protected cardiomyocytes after in vitro hypoxia reoxygenation and reduced infarct size in mice submitted to in vivo ischemia-reperfusion. Altogether, our report emphasizes the role of translocon in cardioprotection and highlights a new paradigm in cardioprotection by functionally uncoupling the RyR-dependent Ca2+ stores and translocon-dependent Ca2+ stores.
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Affiliation(s)
- Ribal Al-Mawla
- Univ Lyon, CarMeN Laboratory, INSERM, INRA, INSA Lyon, Université Claude Bernard Lyon 1, 69500 Bron, France; (R.A.-M.); (M.D.); (N.T.); (L.P.); (B.P.); (Y.G.); (C.V.); (Z.H.); (A.P.); (C.C.D.S.); (M.O.); (G.B.); (F.V.C.)
- Hospices Civils de Lyon, Groupement Hospitalier EST, Département de Cardiologie, IHU-OPERA Bâtiment B13, 69500 Bron, France
| | - Mallory Ducrozet
- Univ Lyon, CarMeN Laboratory, INSERM, INRA, INSA Lyon, Université Claude Bernard Lyon 1, 69500 Bron, France; (R.A.-M.); (M.D.); (N.T.); (L.P.); (B.P.); (Y.G.); (C.V.); (Z.H.); (A.P.); (C.C.D.S.); (M.O.); (G.B.); (F.V.C.)
- Hospices Civils de Lyon, Groupement Hospitalier EST, Département de Cardiologie, IHU-OPERA Bâtiment B13, 69500 Bron, France
| | - Nolwenn Tessier
- Univ Lyon, CarMeN Laboratory, INSERM, INRA, INSA Lyon, Université Claude Bernard Lyon 1, 69500 Bron, France; (R.A.-M.); (M.D.); (N.T.); (L.P.); (B.P.); (Y.G.); (C.V.); (Z.H.); (A.P.); (C.C.D.S.); (M.O.); (G.B.); (F.V.C.)
- Hospices Civils de Lyon, Groupement Hospitalier EST, Département de Cardiologie, IHU-OPERA Bâtiment B13, 69500 Bron, France
| | - Lucille Païta
- Univ Lyon, CarMeN Laboratory, INSERM, INRA, INSA Lyon, Université Claude Bernard Lyon 1, 69500 Bron, France; (R.A.-M.); (M.D.); (N.T.); (L.P.); (B.P.); (Y.G.); (C.V.); (Z.H.); (A.P.); (C.C.D.S.); (M.O.); (G.B.); (F.V.C.)
- Hospices Civils de Lyon, Groupement Hospitalier EST, Département de Cardiologie, IHU-OPERA Bâtiment B13, 69500 Bron, France
| | - Bruno Pillot
- Univ Lyon, CarMeN Laboratory, INSERM, INRA, INSA Lyon, Université Claude Bernard Lyon 1, 69500 Bron, France; (R.A.-M.); (M.D.); (N.T.); (L.P.); (B.P.); (Y.G.); (C.V.); (Z.H.); (A.P.); (C.C.D.S.); (M.O.); (G.B.); (F.V.C.)
- Hospices Civils de Lyon, Groupement Hospitalier EST, Département de Cardiologie, IHU-OPERA Bâtiment B13, 69500 Bron, France
| | - Yves Gouriou
- Univ Lyon, CarMeN Laboratory, INSERM, INRA, INSA Lyon, Université Claude Bernard Lyon 1, 69500 Bron, France; (R.A.-M.); (M.D.); (N.T.); (L.P.); (B.P.); (Y.G.); (C.V.); (Z.H.); (A.P.); (C.C.D.S.); (M.O.); (G.B.); (F.V.C.)
- Hospices Civils de Lyon, Groupement Hospitalier EST, Département de Cardiologie, IHU-OPERA Bâtiment B13, 69500 Bron, France
| | - Camille Villedieu
- Univ Lyon, CarMeN Laboratory, INSERM, INRA, INSA Lyon, Université Claude Bernard Lyon 1, 69500 Bron, France; (R.A.-M.); (M.D.); (N.T.); (L.P.); (B.P.); (Y.G.); (C.V.); (Z.H.); (A.P.); (C.C.D.S.); (M.O.); (G.B.); (F.V.C.)
- Hospices Civils de Lyon, Groupement Hospitalier EST, Département de Cardiologie, IHU-OPERA Bâtiment B13, 69500 Bron, France
| | - Zeina Harhous
- Univ Lyon, CarMeN Laboratory, INSERM, INRA, INSA Lyon, Université Claude Bernard Lyon 1, 69500 Bron, France; (R.A.-M.); (M.D.); (N.T.); (L.P.); (B.P.); (Y.G.); (C.V.); (Z.H.); (A.P.); (C.C.D.S.); (M.O.); (G.B.); (F.V.C.)
- Hospices Civils de Lyon, Groupement Hospitalier EST, Département de Cardiologie, IHU-OPERA Bâtiment B13, 69500 Bron, France
| | - Alexandre Paccalet
- Univ Lyon, CarMeN Laboratory, INSERM, INRA, INSA Lyon, Université Claude Bernard Lyon 1, 69500 Bron, France; (R.A.-M.); (M.D.); (N.T.); (L.P.); (B.P.); (Y.G.); (C.V.); (Z.H.); (A.P.); (C.C.D.S.); (M.O.); (G.B.); (F.V.C.)
- Hospices Civils de Lyon, Groupement Hospitalier EST, Département de Cardiologie, IHU-OPERA Bâtiment B13, 69500 Bron, France
| | - Claire Crola Da Silva
- Univ Lyon, CarMeN Laboratory, INSERM, INRA, INSA Lyon, Université Claude Bernard Lyon 1, 69500 Bron, France; (R.A.-M.); (M.D.); (N.T.); (L.P.); (B.P.); (Y.G.); (C.V.); (Z.H.); (A.P.); (C.C.D.S.); (M.O.); (G.B.); (F.V.C.)
- Hospices Civils de Lyon, Groupement Hospitalier EST, Département de Cardiologie, IHU-OPERA Bâtiment B13, 69500 Bron, France
| | - Michel Ovize
- Univ Lyon, CarMeN Laboratory, INSERM, INRA, INSA Lyon, Université Claude Bernard Lyon 1, 69500 Bron, France; (R.A.-M.); (M.D.); (N.T.); (L.P.); (B.P.); (Y.G.); (C.V.); (Z.H.); (A.P.); (C.C.D.S.); (M.O.); (G.B.); (F.V.C.)
- Hospices Civils de Lyon, Groupement Hospitalier EST, Département de Cardiologie, IHU-OPERA Bâtiment B13, 69500 Bron, France
- Cardiovascular functional explorations, Louis Pradel hospital, Hospices Civils de Lyon, 69677 Lyon, France
| | - Gabriel Bidaux
- Univ Lyon, CarMeN Laboratory, INSERM, INRA, INSA Lyon, Université Claude Bernard Lyon 1, 69500 Bron, France; (R.A.-M.); (M.D.); (N.T.); (L.P.); (B.P.); (Y.G.); (C.V.); (Z.H.); (A.P.); (C.C.D.S.); (M.O.); (G.B.); (F.V.C.)
- Hospices Civils de Lyon, Groupement Hospitalier EST, Département de Cardiologie, IHU-OPERA Bâtiment B13, 69500 Bron, France
| | - Sylvie Ducreux
- Univ Lyon, CarMeN Laboratory, INSERM, INRA, INSA Lyon, Université Claude Bernard Lyon 1, 69500 Bron, France; (R.A.-M.); (M.D.); (N.T.); (L.P.); (B.P.); (Y.G.); (C.V.); (Z.H.); (A.P.); (C.C.D.S.); (M.O.); (G.B.); (F.V.C.)
- Hospices Civils de Lyon, Groupement Hospitalier EST, Département de Cardiologie, IHU-OPERA Bâtiment B13, 69500 Bron, France
- Correspondence:
| | - Fabien Van Coppenolle
- Univ Lyon, CarMeN Laboratory, INSERM, INRA, INSA Lyon, Université Claude Bernard Lyon 1, 69500 Bron, France; (R.A.-M.); (M.D.); (N.T.); (L.P.); (B.P.); (Y.G.); (C.V.); (Z.H.); (A.P.); (C.C.D.S.); (M.O.); (G.B.); (F.V.C.)
- Hospices Civils de Lyon, Groupement Hospitalier EST, Département de Cardiologie, IHU-OPERA Bâtiment B13, 69500 Bron, France
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8
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Lizák B, Szarka A, Kim Y, Choi KS, Németh CE, Marcolongo P, Benedetti A, Bánhegyi G, Margittai É. Glucose Transport and Transporters in the Endomembranes. Int J Mol Sci 2019; 20:ijms20235898. [PMID: 31771288 PMCID: PMC6929180 DOI: 10.3390/ijms20235898] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 11/16/2019] [Accepted: 11/21/2019] [Indexed: 12/18/2022] Open
Abstract
Glucose is a basic nutrient in most of the creatures; its transport through biological membranes is an absolute requirement of life. This role is fulfilled by glucose transporters, mediating the transport of glucose by facilitated diffusion or by secondary active transport. GLUT (glucose transporter) or SLC2A (Solute carrier 2A) families represent the main glucose transporters in mammalian cells, originally described as plasma membrane transporters. Glucose transport through intracellular membranes has not been elucidated yet; however, glucose is formed in the lumen of various organelles. The glucose-6-phosphatase system catalyzing the last common step of gluconeogenesis and glycogenolysis generates glucose within the lumen of the endoplasmic reticulum. Posttranslational processing of the oligosaccharide moiety of glycoproteins also results in intraluminal glucose formation in the endoplasmic reticulum (ER) and Golgi. Autophagic degradation of polysaccharides, glycoproteins, and glycolipids leads to glucose accumulation in lysosomes. Despite the obvious necessity, the mechanism of glucose transport and the molecular nature of mediating proteins in the endomembranes have been hardly elucidated for the last few years. However, recent studies revealed the intracellular localization and functional features of some glucose transporters; the aim of the present paper was to summarize the collected knowledge.
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Affiliation(s)
- Beáta Lizák
- Department of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University, 1094 Budapest, Hungary; (B.L.); (C.E.N.); (G.B.)
| | - András Szarka
- Laboratory of Biochemistry and Molecular Biology, Department of Applied Biotechnology and Food Science, Budapest University of Technology and Economics, 1111 Budapest, Hungary;
| | - Yejin Kim
- Institute of Translational Medicine, Semmelweis University, 1094 Budapest, Hungary; (Y.K.); (K.-s.C.)
| | - Kyu-sung Choi
- Institute of Translational Medicine, Semmelweis University, 1094 Budapest, Hungary; (Y.K.); (K.-s.C.)
| | - Csilla E. Németh
- Department of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University, 1094 Budapest, Hungary; (B.L.); (C.E.N.); (G.B.)
| | - Paola Marcolongo
- Department of Molecular and Developmental Medicine, University of Siena, 53100 Siena, Italy; (P.M.); (A.B.)
| | - Angelo Benedetti
- Department of Molecular and Developmental Medicine, University of Siena, 53100 Siena, Italy; (P.M.); (A.B.)
| | - Gábor Bánhegyi
- Department of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University, 1094 Budapest, Hungary; (B.L.); (C.E.N.); (G.B.)
| | - Éva Margittai
- Institute of Translational Medicine, Semmelweis University, 1094 Budapest, Hungary; (Y.K.); (K.-s.C.)
- Correspondence: ; Tel.: +36-459-1500 (ext. 60311); Fax: +36-1-2662615
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9
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Bachmann K, Bockhorn M, Mann O, Gebauer F, Blessmann M, Izbicki JR, Grupp K. Aberrant expression of Sec61α in esophageal cancers. J Cancer Res Clin Oncol 2019; 145:2039-2044. [PMID: 31197453 DOI: 10.1007/s00432-019-02955-7] [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: 05/08/2019] [Accepted: 06/11/2019] [Indexed: 11/29/2022]
Abstract
INTRODUCTION The heterotrimeric Sec61α translocon complex is topological located in the membrane of the endoplasmic reticulum (ER) and allows protein transport and calcium across the membrane. Recently, aberrant expression of Sec proteins was linked to carcinogenesis and prognosis of patients. MATERIALS AND METHODS Here, we analysed the role of Sec61α in esophageal cancer, and we analysed Sec61α staining on a tissue microarray containing more than 600 esophageal cancer specimens by immunohistochemistry. RESULTS Sec61α staining was always strong in benign esophagus, but was only found in 5% of interpretable esophageal adenocarcinomas (EACs) and 14.5% of squamous cell carcinomas (ESCCs). Reduced Sec61α staining was not strongly linked to tumor phenotype in both subgroups of esophageal cancers and was unrelated to clinical outcome of patients (EACs: p = 0.8051 and ESCCs: p = 0.2751). CONCLUSIONS Thus, Sec61α measurement has not an additional prognostic benefit for the patients.
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Affiliation(s)
- Kai Bachmann
- General, Visceral and Thoracic Surgery Department and Clinic, University Medical Center Hamburg-Eppendorf, 20251, Hamburg, Germany
| | - Maximillian Bockhorn
- General, Visceral and Thoracic Surgery Department and Clinic, University Medical Center Hamburg-Eppendorf, 20251, Hamburg, Germany
| | - Oliver Mann
- General, Visceral and Thoracic Surgery Department and Clinic, University Medical Center Hamburg-Eppendorf, 20251, Hamburg, Germany
| | - Florian Gebauer
- General, Visceral and Thoracic Surgery Department and Clinic, University Medical Center Hamburg-Eppendorf, 20251, Hamburg, Germany
| | - Marco Blessmann
- Department of Plastic, Reconstructive and Aesthetic Surgery, University Medical Center Hamburg-Eppendorf, 20251, Hamburg, Germany
| | - Jakob Robert Izbicki
- General, Visceral and Thoracic Surgery Department and Clinic, University Medical Center Hamburg-Eppendorf, 20251, Hamburg, Germany
| | - Katharina Grupp
- General, Visceral and Thoracic Surgery Department and Clinic, University Medical Center Hamburg-Eppendorf, 20251, Hamburg, Germany. .,Department of Plastic, Reconstructive and Aesthetic Surgery, University Medical Center Hamburg-Eppendorf, 20251, Hamburg, Germany.
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10
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Lang S, Nguyen D, Pfeffer S, Förster F, Helms V, Zimmermann R. Functions and Mechanisms of the Human Ribosome-Translocon Complex. Subcell Biochem 2019; 93:83-141. [PMID: 31939150 DOI: 10.1007/978-3-030-28151-9_4] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The membrane of the endoplasmic reticulum (ER) in human cells harbors the protein translocon, which facilitates membrane insertion and translocation of almost every newly synthesized polypeptide targeted to organelles of the secretory pathway. The translocon comprises the polypeptide-conducting Sec61 channel and several additional proteins, which are associated with the heterotrimeric Sec61 complex. This ensemble of proteins facilitates ER targeting of precursor polypeptides, Sec61 channel opening and closing, and modification of precursor polypeptides in transit through the Sec61 complex. Recently, cryoelectron tomography of translocons in native ER membranes has given unprecedented insights into the architecture and dynamics of the native, ribosome-associated translocon and the Sec61 channel. These structural data are discussed in light of different Sec61 channel activities including ribosome receptor function, membrane insertion or translocation of newly synthesized polypeptides as well as the possible roles of the Sec61 channel as a passive ER calcium leak channel and regulator of ATP/ADP exchange between cytosol and ER.
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Affiliation(s)
- Sven Lang
- Competence Center for Molecular Medicine, Saarland University Medical School, Building 44, 66421, Homburg, Germany.
| | - Duy Nguyen
- Center for Bioinformatics, Saarland University, 66041, Saarbrücken, Germany
| | - Stefan Pfeffer
- Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, 82152, Martinsried, Germany
- ZMBH, 69120, Heidelberg, Germany
| | - Friedrich Förster
- Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, 82152, Martinsried, Germany
- Center for Biomolecular Research, Utrecht University, 3584 CH, Utrecht, The Netherlands
| | - Volkhard Helms
- Center for Bioinformatics, Saarland University, 66041, Saarbrücken, Germany
| | - Richard Zimmermann
- Competence Center for Molecular Medicine, Saarland University Medical School, Building 44, 66421, Homburg, Germany
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11
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Estrada AL, Hudson WM, Kim PY, Stewart CM, Peelor FF, Wei Y, Wang D, Hamilton KL, Miller BF, Pagliassotti MJ. Short-term changes in diet composition do not affect in vivo hepatic protein synthesis in rats. Am J Physiol Endocrinol Metab 2018; 314:E241-E250. [PMID: 28851736 PMCID: PMC5899216 DOI: 10.1152/ajpendo.00209.2017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/23/2017] [Revised: 08/22/2017] [Accepted: 08/23/2017] [Indexed: 11/22/2022]
Abstract
Protein synthesis is critical to protein homeostasis (proteostasis), and modifications in protein synthesis influence lifespan and the development of comorbidities associated with obesity. In the present study, we examined the acute response of liver protein synthesis to either high-fat or high-sucrose diets in order to elucidate nutrient-mediated regulation of hepatic protein synthesis in the absence of body fat accumulation. Total and endoplasmic reticulum-associated protein syntheses were assessed by use of the stable isotope, deuterium oxide (2H2O), in rats provided a control diet or diets enriched in polyunsaturated fat, saturated fat, or sucrose for 2, 4, or 7 days. The three experimental diets increased hepatic triglycerides 46-91% on day 7 and fasting insulin levels 83-117% on day 7, but did not result in differences in body weight when compared with control ( n = 6/diet/time). The fraction of newly synthesized proteins in total liver lysates and microsomes was not significantly different among dietary groups ( n = 3/diet/time). To determine whether the experimental diets provoked a transcriptional response to enhance the capacity for protein synthesis, we also measured a panel of genes linked to amino acid transport, synthesis, and processing. There were no significant differences in any of the genes measured among groups. Therefore, dietary treatments that have been linked to impaired proteostasis and that promote hepatic steatosis and insulin resistance, did not result in significant changes in total or ER-associated protein synthesis in the liver over a 7-day period.
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Affiliation(s)
- Andrea Lee Estrada
- Department of Food Science and Human Nutrition, Colorado State University , Fort Collins, Colorado
| | - William Max Hudson
- Department of Food Science and Human Nutrition, Colorado State University , Fort Collins, Colorado
| | - Paul Y Kim
- Department of Biology, Grambling State University, Grambling, Louisiana
| | - Claire Marie Stewart
- Department of Food Science and Human Nutrition, Colorado State University , Fort Collins, Colorado
| | - Frederick F Peelor
- Department of Health and Exercise Science, Colorado State University , Fort Collins, Colorado
| | - Yuren Wei
- Department of Food Science and Human Nutrition, Colorado State University , Fort Collins, Colorado
| | - Dong Wang
- Department of Food Science and Human Nutrition, Colorado State University , Fort Collins, Colorado
| | - Karyn L Hamilton
- Department of Health and Exercise Science, Colorado State University , Fort Collins, Colorado
| | - Benjamin F Miller
- Department of Health and Exercise Science, Colorado State University , Fort Collins, Colorado
| | - Michael J Pagliassotti
- Department of Food Science and Human Nutrition, Colorado State University , Fort Collins, Colorado
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12
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Abstract
Many proteins are translocated across the endoplasmic reticulum (ER) membrane in eukaryotes or the plasma membrane in prokaryotes. These proteins use hydrophobic signal sequences or transmembrane (TM) segments to trigger their translocation through the protein-conducting Sec61/SecY channel. Substrates are first directed to the channel by cytosolic targeting factors, which use hydrophobic pockets to bind diverse signal and TM sequences. Subsequently, these hydrophobic sequences insert into the channel, docking into a groove on the outside of the lateral gate of the channel, where they also interact with lipids. Structural data and biochemical experiments have elucidated how channel partners, the ribosome in cotranslational translocation, and the eukaryotic ER chaperone BiP or the prokaryotic cytosolic SecA ATPase in posttranslational translocation move polypeptides unidirectionally across the membrane. Structures of auxiliary components of the bacterial translocon, YidC and SecD/F, provide additional insight. Taken together, these recent advances result in mechanistic models of protein translocation.
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Affiliation(s)
- Tom A Rapoport
- Department of Cell Biology, Howard Hughes Medical Institute and Harvard Medical School, Boston, Massachusetts 02115; ,
| | - Long Li
- Department of Cell Biology, Howard Hughes Medical Institute and Harvard Medical School, Boston, Massachusetts 02115; ,
| | - Eunyong Park
- The Rockefeller University and Howard Hughes Medical Institute, New York, NY 10065;
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13
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Let's talk about Secs: Sec61, Sec62 and Sec63 in signal transduction, oncology and personalized medicine. Signal Transduct Target Ther 2017; 2:17002. [PMID: 29263911 PMCID: PMC5661625 DOI: 10.1038/sigtrans.2017.2] [Citation(s) in RCA: 91] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Revised: 01/11/2017] [Accepted: 01/17/2017] [Indexed: 12/11/2022] Open
Abstract
The heterotrimeric Sec61 complex and the dimeric Sec62/Sec63 complex are located in the membrane of the human endoplasmic reticulum (ER) and play a central role in translocation of nascent and newly synthesized precursor polypeptides into the ER. This process involves targeting of the precursors to the membrane and opening of the polypeptide conducting Sec61 channel for translocation. Apart from this central role in the intracellular transport of polypeptides, several studies of the last decade uncovered additional functions of Sec proteins in intracellular signaling: Sec62 can induce ER-phagy in the process of recovery of cells from ER stress and the Sec61 channel can also act as a passive ER calcium leak channel. Furthermore, mutations, amplifications and an overexpression of the SEC genes were linked to various diseases including kidney and liver diseases, diabetes and human cancer. Studies of the last decade could not only elucidate the functional role of Sec proteins in the pathogenesis of these diseases, but also demonstrate a relevance of Sec62 as a prognostic and predictive biomarker in head and neck cancer, prostate and lung cancer including a basis for new therapeutic strategies. In this article, we review the current understanding of protein transport across the ER membrane as central function of Sec proteins and further focus on recent studies that gave first insights into the functional role and therapeutic relevance of Sec61, Sec62 and Sec63 in human diseases.
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14
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Ion channel expression as promising cancer biomarker. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1848:2685-702. [PMID: 25542783 DOI: 10.1016/j.bbamem.2014.12.016] [Citation(s) in RCA: 131] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Revised: 12/10/2014] [Accepted: 12/16/2014] [Indexed: 12/11/2022]
Abstract
Cancer is a disease with marked heterogeneity in both response to therapy and survival. Clinical and histopathological characteristics have long determined prognosis and therapy. The introduction of molecular diagnostics has heralded an explosion in new prognostic factors. Overall, histopathology, immunohistochemistry and molecular biology techniques have described important new prognostic subgroups in the different cancer categories. Ion channels and transporters (ICT) are a new class of membrane proteins which are aberrantly expressed in several types of human cancers. Besides regulating different aspect of cancer cell behavior, ICT can now represent novel cancer biomarkers. A summary of the data obtained so far and relative to breast, prostate, lung, colorectal, esophagus, pancreatic and gastric cancers are reported. Special emphasis is given to those studies aimed at relating specific ICT or a peculiar ICT profile with current diagnostic methods. Overall, we are close to exploit ICTs for diagnostic, prognostic or predictive purposes in cancer. This article is part of a Special Issue entitled: Membrane channels and transporters in cancers.
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15
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Zampese E, Pizzo P. Intracellular organelles in the saga of Ca2+ homeostasis: different molecules for different purposes? Cell Mol Life Sci 2012; 69:1077-104. [PMID: 21968921 PMCID: PMC11114864 DOI: 10.1007/s00018-011-0845-9] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2011] [Revised: 09/15/2011] [Accepted: 09/19/2011] [Indexed: 11/28/2022]
Abstract
An increase in the concentration of cytosolic free Ca(2+) is a key component regulating different cellular processes ranging from egg fertilization, active secretion and movement, to cell differentiation and death. The multitude of phenomena modulated by Ca(2+), however, do not simply rely on increases/decreases in its concentration, but also on specific timing, shape and sub-cellular localization of its signals that, combined together, provide a huge versatility in Ca(2+) signaling. Intracellular organelles and their Ca(2+) handling machineries exert key roles in this complex and precise mechanism, and this review will try to depict a map of Ca(2+) routes inside cells, highlighting the uniqueness of the different Ca(2+) toolkit components and the complexity of the interactions between them.
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Affiliation(s)
- Enrico Zampese
- Department of Biomedical Sciences, University of Padova, Viale G. Colombo 3, 35121 Padova, Italy
| | - Paola Pizzo
- Department of Biomedical Sciences, University of Padova, Viale G. Colombo 3, 35121 Padova, Italy
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16
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Harsman A, Bartsch P, Hemmis B, Krüger V, Wagner R. Exploring protein import pores of cellular organelles at the single molecule level using the planar lipid bilayer technique. Eur J Cell Biol 2012; 90:721-30. [PMID: 21684628 DOI: 10.1016/j.ejcb.2011.04.012] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Proteins of living cells carry out their specialized functions within various subcellular membranes or aqueous spaces. Approximately half of all the proteins of a typical cell are transported into or across membranes. Targeting and transport to their correct subcellular destinations are essential steps in protein biosynthesis. In eukaryotic cells secretory proteins are transported into the endoplasmic reticulum before they are transported in vesicles to the plasma membrane. Virtually all proteins of the endosymbiotic organelles, chloroplasts and mitochondria, are synthesized on cytosolic ribosomes and posttranslationally imported. Genetic and biochemical techniques led to rather detailed knowledge on the subunit composition of the various protein transport complexes which carry out the membrane transport of the preproteins. Conclusive concepts on targeting and cytosolic transport of polypeptides emerged, while still few details on the molecular nature and mechanisms of the channel moieties of protein translocation complexes have been achieved. In this paper we will describe the history of how the individual subunits forming the channel pores of the chloroplast, mitochondrial and endoplasmic reticulum protein import machineries were identified and characterized by single channel electrophysiological techniques in planar bilayers. We will also highlight recent developments in the exploration of the molecular properties of protein translocating channels and the regulation of the diverse protein translocation systems using the planar bilayer technique.
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Affiliation(s)
- Anke Harsman
- University of Osnabrück, Faculty of Biology and Chemistry, Department of Biophysics, Barbarastr. 13, 49076 Osnabrück, Germany
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17
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Preserving the membrane barrier for small molecules during bacterial protein translocation. Nature 2011; 473:239-42. [PMID: 21562565 PMCID: PMC3093665 DOI: 10.1038/nature10014] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2011] [Accepted: 03/22/2011] [Indexed: 01/03/2023]
Abstract
Many proteins are translocated through the SecY channel in bacteria and archaea and through the related Sec61 channel in eukaryotes. The channel has an hourglass shape with a narrow constriction approximately halfway across the membrane, formed by a pore ring of amino acids. While the cytoplasmic cavity of the channel is empty, the extracellular cavity is filled with a short helix called the plug, which moves out of the way during protein translocation. The mechanism by which the channel transports large polypeptides and yet prevents the passage of small molecules, such as ions or metabolites, has been controversial. Here, we have addressed this issue in intact Escherichia coli cells by testing the permeation of small molecules through wild-type and mutant SecY channels, which are either in the resting state or contain a defined translocating polypeptide chain. We show that in the resting state, the channel is sealed by both the pore ring and the plug domain. During translocation, the pore ring forms a 'gasket-like' seal around the polypeptide chain, preventing the permeation of small molecules. The structural conservation of the channel in all organisms indicates that this may be a universal mechanism by which the membrane barrier is maintained during protein translocation.
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18
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Erdmann F, Schäuble N, Lang S, Jung M, Honigmann A, Ahmad M, Dudek J, Benedix J, Harsman A, Kopp A, Helms V, Cavalié A, Wagner R, Zimmermann R. Interaction of calmodulin with Sec61α limits Ca2+ leakage from the endoplasmic reticulum. EMBO J 2010; 30:17-31. [PMID: 21102557 DOI: 10.1038/emboj.2010.284] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2010] [Accepted: 10/22/2010] [Indexed: 12/31/2022] Open
Abstract
In eukaryotes, protein transport into the endoplasmic reticulum (ER) is facilitated by a protein-conducting channel, the Sec61 complex. The presence of large, water-filled pores with uncontrolled ion permeability, as formed by Sec61 complexes in the ER membrane, would seriously interfere with the regulated release of calcium from the ER lumen into the cytosol, an essential mechanism for intracellular signalling. We identified a calmodulin (CaM)-binding motif in the cytosolic N-terminus of mammalian Sec61α that bound CaM but not Ca2+-free apocalmodulin with nanomolar affinity and sequence specificity. In single-channel measurements, CaM potently mediated Sec61-channel closure in Ca2+-dependent manner. At the cellular level, two different CaM antagonists stimulated calcium release from the ER through Sec61 channels. However, protein transport into microsomes was not modulated by Ca2+-CaM. Molecular modelling of the ribosome/Sec61/CaM complexes supports the view that simultaneous ribosome and CaM binding to the Sec61 complex may be possible. Overall, CaM is involved in limiting Ca2+ leakage from the ER.
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Affiliation(s)
- Frank Erdmann
- Biophysics, Osnabrück University, Osnabrück, Germany
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19
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Lizák B, Csala M, Benedetti A, Bánhegyi G. The translocon and the non-specific transport of small molecules in the endoplasmic reticulum (Review). Mol Membr Biol 2009; 25:95-101. [DOI: 10.1080/09687680701670481] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Affiliation(s)
- Beáta Lizák
- Department of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University, Budapest, Hungary
- the Pathobiochemistry Research Group of the Hungarian Academy of Sciences, Semmelweis University, Budapest, Hungary
| | - Miklós Csala
- Department of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University, Budapest, Hungary
- the Pathobiochemistry Research Group of the Hungarian Academy of Sciences, Semmelweis University, Budapest, Hungary
| | - Angelo Benedetti
- Department of Pathophysiology, Experimental Medicine and Public Health, University of Siena, Siena, Italy
| | - Gábor Bánhegyi
- Department of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University, Budapest, Hungary
- the Pathobiochemistry Research Group of the Hungarian Academy of Sciences, Semmelweis University, Budapest, Hungary
- Department of Pathophysiology, Experimental Medicine and Public Health, University of Siena, Siena, Italy
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20
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Brunello L, Zampese E, Florean C, Pozzan T, Pizzo P, Fasolato C. Presenilin-2 dampens intracellular Ca2+ stores by increasing Ca2+ leakage and reducing Ca2+ uptake. J Cell Mol Med 2009; 13:3358-69. [PMID: 19382908 PMCID: PMC4516491 DOI: 10.1111/j.1582-4934.2009.00755.x] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
We have previously shown that familial Alzheimer’s disease mutants of presenilin-2 (PS2) and, to a lesser extent, of presenilin-1 (PS1) lower the Ca2+ concentration of intracellular stores. We here examined the mechanism by which wild-type and mutant PS2 affect store Ca2+ handling. By using HeLa, SH-SY5Y and MEFs as model cells, and recombinant aequorins as Ca2+ probes, we show evidence that transient expression of either wild-type or mutant PS2 increases the passive Ca2+ leakage: both ryanodine- and IP3-receptors contribute to Ca2+ exit out of the ER, whereas the ribosome translocon complex is not involved. In SH-SY5Y cells and MEFs, wild-type and mutant PS2 potently reduce the uptake of Ca2+ inside the stores, an effect that can be counteracted by over-expression of SERCA-2B. On this line, in wild-type MEFs, lowering the endogenous level of PS2 by RNA interference, increases the Ca2+-loading capability of intracellular stores. Furthermore, we show that in PS double knockout MEFs, reduction of Ca2+ stores is mimicked by the expression of PS2-D366A, a loss-of-function mutant, uncleaved because also devoid of presenilinase activity but not by co-expression of the two catalytic active fragments of PS2. In summary, both physiological and increased levels of wild-type and mutant PS2 reduce the Ca2+ uptake by intracellular stores. To exert this newly described function, PS2 needs to be in its full-length form, even if it can subsequently be cleaved.
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Affiliation(s)
- Lucia Brunello
- Department of Biomedical Sciences, University of Padova, Padova, Italy
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21
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Amer MS, Li J, O'Regan DJ, Steele DS, Porter KE, Sivaprasadarao A, Beech DJ. Translocon closure to Ca2+ leak in proliferating vascular smooth muscle cells. Am J Physiol Heart Circ Physiol 2009; 296:H910-6. [PMID: 19218505 DOI: 10.1152/ajpheart.00984.2008] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Vascular smooth muscle cells have a proliferative phenotype that is important in vascular development, adaptation, and disease. Intracellular calcium handling is thought to play pivotal roles in determining the properties of these cells, and thus previously unrecognized mechanisms for transmembrane calcium movement are of potential interest. An unsolved question is the mechanism of constitutive (passive) calcium leak from the intracellular stores. Studies of other cell types have suggested that the translocon is a calcium leak pathway. Here we investigated the contribution of the translocon in proliferating vascular smooth muscle cells. Calcium leak into the cytoplasm was measured using fura-2, and protein synthesis was measured using radioactive methionine. Puromycin, emetine, and anisomycin are chemicals that inhibit protein synthesis, acting via the translocon; all three agents strongly inhibited protein synthesis in the smooth muscle cells within 1 h. Puromycin, which opens the translocon, evoked a transient increase in cytoplasmic calcium that was similar in amplitude to the calcium rise evoked by thapsigargin. The puromycin effect was abolished by thapsigargin. The treatment of cells for 1 h with emetine or anisomycin, which close the translocon, inhibited the calcium release evoked by puromycin but not the calcium release evoked by extracellular ATP, endothelin-1, or the calcium ionophore ionomycin. Thapsigargin-evoked calcium rises were slightly suppressed by emetine but unaffected by puromycin or anisomycin. The data suggest that the translocon has the capacity to act as a calcium leak pathway in the ribosomal endoplasmic reticulum but that it is normally closed and lacks relevance to physiological calcium leak mechanisms.
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Affiliation(s)
- Mohamed S Amer
- Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, United Kingdom
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22
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Marjanovic JA, Stojanovic A, Brovkovych VM, Skidgel RA, Du X. Signaling-mediated functional activation of inducible nitric-oxide synthase and its role in stimulating platelet activation. J Biol Chem 2008; 283:28827-34. [PMID: 18753139 DOI: 10.1074/jbc.m801646200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Nitric oxide (NO) is a short lived secondary messenger, synthesized by nitric-oxide synthases (NOS). It is believed that the activity of inducible NOS (iNOS) is regulated primarily at the transcription level by inducing expression of iNOS mRNA and protein, which then continuously produces NO, until its degradation. Platelets do not have the nuclear transcriptional regulatory mechanisms of the iNOS gene and are believed to generate NO in response to agonist stimulation via endothelial NOS (eNOS). However, here we show that agonist-induced NO production is only partially eNOS-dependent and is also mediated by iNOS. Platelet agonist-induced NO production is significantly reduced in iNOS-knockout platelets. Platelet NO production occurs within seconds after agonist addition and is not accompanied by changes in iNOS protein levels, indicating a signaling-mediated functional activation mechanism of iNOS. Importantly, iNOS knock-out and iNOS inhibitors reduce agonist-induced platelet secretion and aggregation and cGMP levels, indicating that iNOS activation is important in stimulating platelets via the newly identified NO-cGMP-dependent platelet secretion pathway. Furthermore, iNOS knock-out mice have prolonged bleeding time, suggesting that this novel mode of regulation of iNOS activity plays a physiologically relevant role in hemostasis.
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Affiliation(s)
- Jasna A Marjanovic
- Department of Pharmacology, University of Illinois College of Medicine, Chicago, IL 60612, USA
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23
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Constitutive, translation-independent opening of the protein-conducting channel in the endoplasmic reticulum. Pflugers Arch 2008; 457:917-30. [DOI: 10.1007/s00424-008-0545-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2008] [Revised: 05/18/2008] [Accepted: 06/10/2008] [Indexed: 10/21/2022]
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24
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Puhka M, Vihinen H, Joensuu M, Jokitalo E. Endoplasmic reticulum remains continuous and undergoes sheet-to-tubule transformation during cell division in mammalian cells. ACTA ACUST UNITED AC 2007; 179:895-909. [PMID: 18056408 PMCID: PMC2099207 DOI: 10.1083/jcb.200705112] [Citation(s) in RCA: 187] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
The endoplasmic reticulum (ER) is a multifaceted cellular organelle both structurally and functionally, and its cell cycle–dependent morphological changes are poorly understood. Our quantitative confocal and EM analyses show that the ER undergoes dramatic reorganization during cell division in cultured mammalian cells as mitotic ER profiles become shorter and more branched. 3D modeling by electron tomography reveals that the abundant interphase structures, sheets, are lost and subsequently transform into a branched tubular network that remains continuous. This is confirmed by observing the most prominent ER subdomain, the nuclear envelope (NE). A NE marker protein spreads to the mitotic ER tubules, although it does not show a homogenous distribution within the network. We mimicked the mitotic ER reorganization using puromycin to strip the membrane-bound ribosomes from the interphase ER corresponding to the observed loss of ribosomes normally occurring during mitosis. We propose that the structural changes in mitotic ER are linked to ribosomal action on the ER membranes.
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Affiliation(s)
- Maija Puhka
- Electron Microscopy Unit, Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland
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25
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Csala M, Marcolongo P, Lizák B, Senesi S, Margittai E, Fulceri R, Magyar JE, Benedetti A, Bánhegyi G. Transport and transporters in the endoplasmic reticulum. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1768:1325-41. [PMID: 17466261 DOI: 10.1016/j.bbamem.2007.03.009] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2006] [Revised: 03/08/2007] [Accepted: 03/15/2007] [Indexed: 12/12/2022]
Abstract
Enzyme activities localized in the luminal compartment of the endoplasmic reticulum are integrated into the cellular metabolism by transmembrane fluxes of their substrates, products and/or cofactors. Most compounds involved are bulky, polar or even charged; hence, they cannot be expected to diffuse through lipid bilayers. Accordingly, transport processes investigated so far have been found protein-mediated. The selective and often rate-limiting transport processes greatly influence the activity, kinetic features and substrate specificity of the corresponding luminal enzymes. Therefore, the phenomenological characterization of endoplasmic reticulum transport contributes largely to the understanding of the metabolic functions of this organelle. Attempts to identify the transporter proteins have only been successful in a few cases, but recent development in molecular biology promises a better progress in this field.
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Affiliation(s)
- Miklós Csala
- Department of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University, Budapest, Hungary
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26
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Ong HL, Liu X, Sharma A, Hegde RS, Ambudkar IS. Intracellular Ca(2+) release via the ER translocon activates store-operated calcium entry. Pflugers Arch 2006; 453:797-808. [PMID: 17171366 DOI: 10.1007/s00424-006-0163-5] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2006] [Revised: 08/02/2006] [Accepted: 08/14/2006] [Indexed: 11/29/2022]
Abstract
Store-operated Ca(2+) entry (SOCE) is activated in response to depletion of intracellular Ca(2+) from the endoplasmic reticulum (ER). A variety of agonists stimulate SOCE via IP(3)-dependent Ca(2+) depletion. SOCE is also activated by thapsigargin, an inhibitor of Ca(2+) reuptake into the ER that induces a net Ca(2+) loss from the ER by unmasking a Ca(2+) "leak" pathway. The molecular identity of this Ca(2+) leak channel and the physiological conditions under which such agonist-independent Ca(2+) depletion might occur remain poorly characterized. In this study, we report that inhibition of the initiation step of protein synthesis (with pactamycin) resulted in detectable Ca(2+) depletion in ER and activation of SOCE. This was completely prevented if the ribosome-nascent chain complexes were first stabilized with an irreversible inhibitor of translational elongation (emetine), suggesting that ER Ca(2+) depletion had occurred through open translocons at the ER. Notably, emetine pretreatment also attenuated thapsigargin-mediated Ca(2+) release and SOCE. Furthermore, both pactamycin and thapsigargin stimulated translocation of STIM1, a protein required for activation of SOCE, to the subplasma membrane region and activated the SOCE-associated current, I (SOC). In aggregate, these data reveal an agonist-independent mechanism for internal Ca(2+) store depletion and activation of SOCE. We suggest that the functional coupling between SOCE and protein synthesis is likely to be critical for maintaining [Ca(2+)](ER) within a range that is required to prevent ER stress during changes in cellular translational activity.
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Affiliation(s)
- Hwei L Ong
- Secretory Physiology Section, Gene Therapy and Therapeutics Branch, National Institute of Dental and Craniofacial Research, Bethesda, MD 20892, USA
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27
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Lizák B, Czegle I, Csala M, Benedetti A, Mandl J, Bánhegyi G. Translocon pores in the endoplasmic reticulum are permeable to small anions. Am J Physiol Cell Physiol 2006; 291:C511-7. [PMID: 16611737 DOI: 10.1152/ajpcell.00274.2005] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Contribution of translocon peptide channels to the permeation of low molecular mass anions was investigated in rat liver microsomes. Puromycin, which purges translocon pores of nascent polypeptides, creating additional empty pores, raised the microsomal uptake of radiolabeled UDP-glucuronic acid, while it did not increase the uptake of glucose-6-phosphate or glutathione. The role of translocon pores in the transport of small anions was also investigated by measuring the effect of puromycin on the activity of microsomal enzymes with intraluminal active sites. The mannose-6-phosphatase activity of glucose-6-phosphatase and the activity of UDP-glucuronosyltransferase were elevated upon addition of puromycin, but glucose-6-phosphatase and beta-glucuronidase activities were not changed. The increase in enzyme activities was due to a better access of the substrates to the luminal compartment rather than to activation of the enzymes. Antibody against Sec61 translocon component decreased the activity of UDP-glucuronosyltransferase and antagonized the effect of puromycin. Similarly, the addition of the puromycin antagonist anisomycin or treatments of microsomes, resulting in the release of attached ribosomes, prevented the puromycin-dependent increase in the activity. Mannose-6-phosphatase and UDP-glucuronosyltransferase activities of smooth microsomal vesicles showed higher basal latencies that were not affected by puromycin. In conclusion, translationally inactive, ribosome-bound translocons allow small anions to cross the endoplasmic reticulum membrane. This pathway can contribute to the nonspecific substrate supply of enzymes with intraluminal active centers.
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Affiliation(s)
- Beáta Lizák
- Department of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University, PO Box 260, 1444 Budapest, Hungary
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28
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Flourakis M, Van Coppenolle F, Lehen'kyi V, Beck B, Skryma R, Prevarskaya N. Passive calcium leak via translocon is a first step for iPLA2-pathway regulated store operated channels activation. FASEB J 2006; 20:1215-7. [PMID: 16611832 DOI: 10.1096/fj.05-5254fje] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Calcium concentration within the endoplasmic reticulum (ER) plays an essential role in cell physiopathology. One of the most enigmatic mechanisms responsible for Ca2+ concentration in the ER is passive calcium leak. Previous studies have shown that the translocon complex is permeable to calcium. However, the involvement of the translocon in the passive calcium leak has not been directly demonstrated. Furthermore, the question whether the passive store depletion via the translocon could activate SOC (store operated channels) replenishing the ER, remains still unresolved. In this study, for the first time, we show that thapsigargin and calcium chelators deplete ER via translocon. Indeed, using confocal imaging, we demonstrate that when the number of opened translocons was lowered neither thapsigargin nor calcium chelators could induce ER store depletion. We also demonstrate that calcium leakage occurring via the translocon activates store-operated current, which is, by its kinetic and pharmacology, similar to that evoked by thapsigargin and EGTA (but not IP3), thus highlighting our hypothesis that calcium leakage via the translocon is a first step for activation of the specific iPLA2-regulated SOC. As the translocon is present in yeast and mammalian cells, our findings suggest that translocon-related calcium signaling is a common phenomenon.
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Affiliation(s)
- Matthieu Flourakis
- Laboratoire de Physiologie Cellulaire, INSERM U800, Bâtiment SN3, Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq Cedex, France.
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29
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Csala M, Bánhegyi G, Benedetti A. Endoplasmic reticulum: a metabolic compartment. FEBS Lett 2006; 580:2160-5. [PMID: 16580671 DOI: 10.1016/j.febslet.2006.03.050] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2006] [Revised: 03/07/2006] [Accepted: 03/15/2006] [Indexed: 01/12/2023]
Abstract
Several biochemical reactions and processes of cell biology are compartmentalized in the endoplasmic reticulum (ER). The view that the ER membrane is basically a scaffold for ER proteins, which is permeable to small molecules, is inconsistent with recent findings. The luminal micro-environment is characteristically different from the cytosol; its protein and glutathione thiols are remarkably more oxidized, and it contains a separate pyridine nucleotide pool. The substrate specificity and activity of certain luminal enzymes are dependent on selective transport of possible substrates and co-factors from the cytosol. Abundant biochemical, pharmacological, clinical and genetic data indicate that the barrier function of the lipid bilayer and specific transport activities in the membrane make the ER a separate metabolic compartment.
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Affiliation(s)
- Miklós Csala
- Department of Medical Chemistry, Semmelweis University and Endoplasmic Reticulum Research Group of the Hungarian Academy of Sciences, 1444 Budapest, Hungary
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30
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. JT, . ML, . WN, . RZ. Calumenin and Reticulocalbin are Associated with the Protein Translocase of the Mammalian Endoplasmic Reticulum. ACTA ACUST UNITED AC 2004. [DOI: 10.3923/jbs.2005.70.75] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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31
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Snapp EL, Reinhart GA, Bogert BA, Lippincott-Schwartz J, Hegde RS. The organization of engaged and quiescent translocons in the endoplasmic reticulum of mammalian cells. ACTA ACUST UNITED AC 2004; 164:997-1007. [PMID: 15051734 PMCID: PMC2172055 DOI: 10.1083/jcb.200312079] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Protein translocons of the mammalian endoplasmic reticulum are composed of numerous functional components whose organization during different stages of the transport cycle in vivo remains poorly understood. We have developed generally applicable methods based on fluorescence resonance energy transfer (FRET) to probe the relative proximities of endogenously expressed translocon components in cells. Examination of substrate-engaged translocons revealed oligomeric assemblies of the Sec61 complex that were associated to varying degrees with other essential components including the signal recognition particle receptor TRAM and the TRAP complex. Remarkably, these components not only remained assembled but also had a similar, yet distinguishable, organization both during and after nascent chain translocation. The persistence of preassembled and complete translocons between successive rounds of transport may facilitate highly efficient translocation in vivo despite temporal constraints imposed by ongoing translation and a crowded cellular environment.
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Affiliation(s)
- Erik L Snapp
- Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, 18 Library Dr., Bldg. 18, Rm. 101, Bethesda, MD 20892, USA
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32
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Van Coppenolle F, Vanden Abeele F, Slomianny C, Flourakis M, Hesketh J, Dewailly E, Prevarskaya N. Ribosome-translocon complex mediates calcium leakage from endoplasmic reticulum stores. J Cell Sci 2004; 117:4135-42. [PMID: 15280427 DOI: 10.1242/jcs.01274] [Citation(s) in RCA: 108] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Under resting conditions, the endoplasmic reticulum (ER) intraluminal free calcium concentration ([Ca(2+)](ER)) reflects a balance between active uptake by Ca(2+)-ATPases and passive efflux via 'leak channels'. Despite their physiological importance and ubiquitous leak pathway mechanism, very little is known about the molecular nature of these channels. As it has been suggested that the open translocon pore complex of the ER is permeable to ions and neutral molecules, we hypothesized that the ribosome-bound translocon would be permeable to calcium after treatment with puromycin, a translation inhibitor that specifically releases polypeptide chains. At this time, the translocon channel is left open. We measured the fluctuations in cytoplasmic and luminal calcium concentrations using fluorescent dyes (fura-2 and magfura-2, respectively). The calcium release induced by thapsigargin (a Ca(2+)-ATPase inhibitor) was lower after puromycin treatment. Puromycin also reduced the [Ca(2+)](ER) level when perfused into the medium, but was ineffective after anisomycin pre-treatment (an inhibitor of the peptidyl transferase). Puromycin had a similar effect in the presence of heparin and ryanodine. This puromycin-evoked [Ca(2+)](ER) decrease was specific to the translocon. We conclude that the translocon complex is a major calcium leak channel. This work reveals a new role for the translocon which is involved in the control of the [Ca(2+)](ER) and could therefore supervise many physiological processes, including gene expression and apoptosis.
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Affiliation(s)
- Fabien Van Coppenolle
- Laboratoire de Physiologie Cellulaire, INSERM EMI 0228, Université de Lille 1, Bâtiment SN3, 59655 Villeneuve d'Ascq CEDEX, France.
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33
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Le Gall S, Neuhof A, Rapoport T. The endoplasmic reticulum membrane is permeable to small molecules. Mol Biol Cell 2003; 15:447-55. [PMID: 14617815 PMCID: PMC329208 DOI: 10.1091/mbc.e03-05-0325] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The lumen of the endoplasmic reticulum (ER) differs from the cytosol in its content of ions and other small molecules, but it is unclear whether the ER membrane is as impermeable as other membranes in the cell. Here, we have tested the permeability of the ER membrane to small, nonphysiological molecules. We report that isolated ER vesicles allow different chemical modification reagents to pass from the outside into the lumen with little hindrance. In permeabilized cells, the ER membrane allows the passage of a small, charged modification reagent that is unable to cross the plasma membrane or the lysosomal and trans-Golgi membranes. A larger polar reagent of approximately 5 kDa is unable to pass through the ER membrane. Permeation of the small molecules is passive because it occurs at low temperature in the absence of energy. These data indicate that the ER membrane is significantly more leaky than other cellular membranes, a property that may be required for protein folding and other functions of the ER.
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Affiliation(s)
- Sylvie Le Gall
- Department of Cell Biology, Howard Hughes Medical Institute/Harvard Medical School, Boston, Massachusetts 02115-6091, USA
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