1
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Zhang X, Liu B, Lal K, Liu H, Tran M, Zhou M, Ezugwu C, Gao X, Dang T, Au ML, Brown E, Wu H, Liao Y. Antioxidant System and Endoplasmic Reticulum Stress in Cataracts. Cell Mol Neurobiol 2023; 43:4041-4058. [PMID: 37874455 PMCID: PMC10842247 DOI: 10.1007/s10571-023-01427-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Accepted: 10/14/2023] [Indexed: 10/25/2023]
Abstract
The primary underlying contributor for cataract, a leading cause of vision impairment and blindness worldwide, is oxidative stress. Oxidative stress triggers protein damage, cell apoptosis, and subsequent cataract formation. The nuclear factor-erythroid 2-related factor 2 (Nrf2) serves as a principal redox transcriptional factor in the lens, offering a line of defense against oxidative stress. In response to oxidative challenges, Nrf2 dissociates from its inhibitor, Kelch-like ECH-associated protein 1 (Keap1), moves to the nucleus, and binds to the antioxidant response element (ARE) to activate the Nrf2-dependent antioxidant system. In parallel, oxidative stress also induces endoplasmic reticulum stress (ERS). Reactive oxygen species (ROS), generated during oxidative stress, can directly damage proteins, causing them to misfold. Initially, the unfolded protein response (UPR) activates to mitigate excessive misfolded proteins. Yet, under persistent or severe stress, the failure to rectify protein misfolding leads to an accumulation of these aberrant proteins, pushing the UPR towards an apoptotic pathway, further contributing to cataractogenesis. Importantly, there is a dynamic interaction between the Nrf2 antioxidant system and the ERS/UPR mechanism in the lens. This interplay, where ERS/UPR can modulate Nrf2 expression and vice versa, holds potential therapeutic implications for cataract prevention and treatment. This review explores the intricate crosstalk between these systems, aiming to illuminate strategies for future advancements in cataract prevention and intervention. The Nrf2-dependent antioxidant system communicates and cross-talks with the ERS/UPR pathway. Both mechanisms are proposed to play pivotal roles in the onset of cataract formation.
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Affiliation(s)
- Xi Zhang
- College of Traditional Chinese Medicine, Beijing University of Chinese Medicine, Beijing, China
| | - Bingqing Liu
- College of Traditional Chinese Medicine, Beijing University of Chinese Medicine, Beijing, China
| | - Kevin Lal
- Pharmaceutical Sciences, College of Pharmacy, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Haihua Liu
- Peking University First Hospital, Beijing, China
| | - Myhoa Tran
- Pharmaceutical Sciences, College of Pharmacy, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Manyu Zhou
- College of Traditional Chinese Medicine, Beijing University of Chinese Medicine, Beijing, China
| | - Chimdindu Ezugwu
- Pharmaceutical Sciences, College of Pharmacy, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Xin Gao
- College of Traditional Chinese Medicine, Beijing University of Chinese Medicine, Beijing, China
| | - Terry Dang
- Pharmaceutical Sciences, College of Pharmacy, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - My-Lien Au
- Pharmaceutical Sciences, College of Pharmacy, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Erica Brown
- School of Medicine, Texas Christian University and University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Hongli Wu
- Pharmaceutical Sciences, College of Pharmacy, University of North Texas Health Science Center, Fort Worth, TX, USA.
- North Texas Eye Research Institute, University of North Texas Health Science Center, Fort Worth, TX, USA.
| | - Yan Liao
- College of Traditional Chinese Medicine, Beijing University of Chinese Medicine, Beijing, China.
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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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Cavalié A, Zimmermann R. Editorial: The evolving picture of Ca 2+ leak from endoplasmic reticulum in health and diseases. Front Physiol 2023; 14:1182455. [PMID: 37051023 PMCID: PMC10083479 DOI: 10.3389/fphys.2023.1182455] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Accepted: 03/20/2023] [Indexed: 03/29/2023] Open
Affiliation(s)
- Adolfo Cavalié
- Experimental and Clinical Pharmacology and Toxicology, Pre-clinical Center for Molecular Signalling (PZMS), Saarland University, Homburg, Germany
| | - Richard Zimmermann
- Competence Center for Molecular Medicine, Saarland University, Homburg, Germany
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4
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Melnyk A, Lang S, Sicking M, Zimmermann R, Jung M. Co-chaperones of the Human Endoplasmic Reticulum: An Update. Subcell Biochem 2023; 101:247-291. [PMID: 36520310 DOI: 10.1007/978-3-031-14740-1_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
In mammalian cells, the rough endoplasmic reticulum (ER) plays central roles in the biogenesis of extracellular plus organellar proteins and in various signal transduction pathways. For these reasons, the ER comprises molecular chaperones, which are involved in import, folding, assembly, export, plus degradation of polypeptides, and signal transduction components, such as calcium channels, calcium pumps, and UPR transducers plus adenine nucleotide carriers/exchangers in the ER membrane. The calcium- and ATP-dependent ER lumenal Hsp70, termed immunoglobulin heavy-chain-binding protein or BiP, is the central player in all these activities and involves up to nine different Hsp40-type co-chaperones, i.e., ER membrane integrated as well as ER lumenal J-domain proteins, termed ERj or ERdj proteins, two nucleotide exchange factors or NEFs (Grp170 and Sil1), and NEF-antagonists, such as MANF. Here we summarize the current knowledge on the ER-resident BiP/ERj chaperone network and focus on the interaction of BiP with the polypeptide-conducting and calcium-permeable Sec61 channel of the ER membrane as an example for BiP action and how its functional cycle is linked to ER protein import and various calcium-dependent signal transduction pathways.
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Affiliation(s)
- Armin Melnyk
- Medical Biochemistry & Molecular Biology, Saarland University, Homburg, Germany
| | - Sven Lang
- Medical Biochemistry & Molecular Biology, Saarland University, Homburg, Germany
| | - Mark Sicking
- Medical Biochemistry & Molecular Biology, Saarland University, Homburg, Germany
| | - Richard Zimmermann
- Medical Biochemistry & Molecular Biology, Saarland University, Homburg, Germany.
| | - Martin Jung
- Medical Biochemistry & Molecular Biology, Saarland University, Homburg, Germany
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5
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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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6
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Feliziani C, Fernandez M, Quasollo G, Holstein D, Bairo SM, Paton JC, Paton AW, de Batista J, Lechleiter JD, Bollo M. Ca 2+ signalling system initiated by endoplasmic reticulum stress stimulates PERK activation. Cell Calcium 2022; 106:102622. [PMID: 35908318 PMCID: PMC9982837 DOI: 10.1016/j.ceca.2022.102622] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Revised: 06/11/2022] [Accepted: 07/05/2022] [Indexed: 01/25/2023]
Abstract
The accumulation of unfolded proteins within the Endoplasmic Reticulum (ER) activates a signal transduction pathway termed the unfolded protein response (UPR), which attempts to restore ER homoeostasis. If this cannot be done, UPR signalling ultimately induces apoptosis. Ca2+ depletion in the ER is a potent inducer of ER stress. Despite the ubiquity of Ca2+ as an intracellular messenger, the precise mechanism(s) by which Ca2+ release affects the UPR remains unknown. Tethering a genetically encoded Ca2+ indicator (GCamP6) to the ER membrane revealed novel Ca2+ signalling events initiated by Ca2+ microdomains in human astrocytes under ER stress, induced by tunicamycin (Tm), an N-glycosylation inhibitor, as well as in a cell model deficient in all three inositol triphosphate receptor isoforms. Pharmacological and molecular studies indicate that these local events are mediated by translocons and that the Ca2+ microdomains impact (PKR)-like-ER kinase (PERK), an UPR sensor, activation. These findings reveal the existence of a Ca2+ signal mechanism by which stressor-mediated Ca2+ release regulates ER stress.
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Affiliation(s)
- Constanza Feliziani
- Instituto de Investigación Médica M y M
Ferreyra, INIMEC-CONICET, Universidad Nacional de Córdoba, 2434 Friuli,
Córdoba 5016, Argentina
| | - Macarena Fernandez
- Instituto de Investigación Médica M y M
Ferreyra, INIMEC-CONICET, Universidad Nacional de Córdoba, 2434 Friuli,
Córdoba 5016, Argentina
| | - Gonzalo Quasollo
- Instituto de Investigación Médica M y M
Ferreyra, INIMEC-CONICET, Universidad Nacional de Córdoba, 2434 Friuli,
Córdoba 5016, Argentina
| | - Deborah Holstein
- Department of Cell Systems and Anatomy, UT Health San
Antonio, 8403 Floyd Curl Dr., San Antonio, TX 78229-3904, USA
| | - Sebastián M Bairo
- Instituto de Investigación Médica M y M
Ferreyra, INIMEC-CONICET, Universidad Nacional de Córdoba, 2434 Friuli,
Córdoba 5016, Argentina
| | - James C Paton
- Research Centre for Infectious Diseases, School of
Molecular and Biomedical Science, University of Adelaide, South Australia 5005,
Australia
| | - Adrienne W Paton
- Research Centre for Infectious Diseases, School of
Molecular and Biomedical Science, University of Adelaide, South Australia 5005,
Australia
| | - Juan de Batista
- Instituto Universitario de Ciencias Biomédicas de
Córdoba (IUCBC), Hospital Privado Universitario de Córdoba, 420
Naciones Unidas, Córdoba 5016, Argentina
| | - James D Lechleiter
- Department of Cell Systems and Anatomy, UT Health San
Antonio, 8403 Floyd Curl Dr., San Antonio, TX 78229-3904, USA
| | - Mariana Bollo
- Instituto de Investigación Médica M y M Ferreyra, INIMEC-CONICET, Universidad Nacional de Córdoba, 2434 Friuli, Córdoba 5016, Argentina.
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7
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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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8
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Regulation of calcium homeostasis and flux between the endoplasmic reticulum and the cytosol. J Biol Chem 2022; 298:102061. [PMID: 35609712 PMCID: PMC9218512 DOI: 10.1016/j.jbc.2022.102061] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Revised: 05/17/2022] [Accepted: 05/18/2022] [Indexed: 12/20/2022] Open
Abstract
The concentration of Ca2+ in the endoplasmic reticulum (ER) is critically important for maintaining its oxidizing environment as well as for maintaining luminal ATP levels required for chaperone activity. Therefore, local luminal Ca2+ concentrations and the dynamic Ca2+ flux between the different subcellular compartments are tightly controlled. Influx of Ca2+ into the ER is enabled by a reductive shift, which opens the sarcoendoplasmic reticulum calcium transport ATPase pump, building the Ca2+ gradient across the ER membrane required for ATP import. Meanwhile, Ca2+ leakage from the ER has been reported to occur via the Sec61 translocon following protein translocation. In this review, we provide an overview of the complex regulation of Ca2+ homeostasis, Ca2+ flux between subcellular compartments, and the cellular stress response (the unfolded protein response) induced upon dysregulated luminal Ca2+ metabolism. We also provide insight into the structure and gating mechanism at the Sec61 translocon and examine the role of ER-resident cochaperones in assisting the central ER-resident chaperone BiP in the control of luminal Ca2+ concentrations.
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9
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Cancer associated mutations in Sec61γ alter the permeability of the ER translocase. PLoS Genet 2021; 17:e1009780. [PMID: 34460824 PMCID: PMC8439465 DOI: 10.1371/journal.pgen.1009780] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2020] [Revised: 09/14/2021] [Accepted: 08/16/2021] [Indexed: 11/19/2022] Open
Abstract
Translocation of secretory and integral membrane proteins across or into the ER membrane occurs via the Sec61 complex, a heterotrimeric protein complex possessing two essential sub-units, Sec61p/Sec61α and Sss1p/Sec61γ and the non-essential Sbh1p/Sec61β subunit. In addition to forming a protein conducting channel, the Sec61 complex maintains the ER permeability barrier, preventing flow of molecules and ions. Loss of Sec61 integrity is detrimental and implicated in the progression of disease. The Sss1p/Sec61γ C-terminus is juxtaposed to the key gating module of Sec61p/Sec61α and is important for gating the translocon. Inspection of the cancer genome database identifies six mutations in highly conserved amino acids of Sec61γ/Sss1p. We identify that five out of the six mutations identified affect gating of the ER translocon, albeit with varying strength. Together, we find that mutations in Sec61γ that arise in malignant cells result in altered translocon gating dynamics, this offers the potential for the translocon to represent a target in co-therapy for cancer treatment.
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10
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Dhandapani P, Dondapati SK, Zemella A, Bräuer D, Wüstenhagen DA, Mergler S, Kubick S. Targeted esterase-induced dye (TED) loading supports direct calcium imaging in eukaryotic cell-free systems. RSC Adv 2021; 11:16285-16296. [PMID: 35479141 PMCID: PMC9030739 DOI: 10.1039/d0ra08397f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Accepted: 03/25/2021] [Indexed: 11/21/2022] Open
Abstract
Calcium imaging is an important functional tool for analysing ion channels, transporters and pumps for drug screening in living cells. Depicted eukaryotic cell-free systems utilize microsomes, derived from the endoplasmic reticulum to incorporate the synthesized membrane proteins-like ion channels. Carboxylesterase is required to cleave the acetoxymethyl ester moiety of the chemical calcium indicators in order to ensure its immobility across the endoplasmic reticulum membrane. Absence or an inadequate amount of carboxylesterase in the endoplasmic reticulum of different eukaryotic cells poses a hindrance to perform calcium imaging in microsomes. In this work, we try to overcome this drawback and adapt the cell-based calcium imaging principle to a cell-free protein synthesis platform. Carboxylesterase synthesized in a Spodoptera frugiperda Sf21 lysate translation system is established as a viable calcium imaging tool in microsomes. Cell-free synthesized carboxylesterase inside microsomes is validated with esterase and dye loading assays. Native proteins from the endoplasmic reticulum, such as ryanodine channels and calcium ATPase, are analysed. Cell-free synthesized transient receptor potential channels are used as model proteins to demonstrate the realization of this concept. Carboxylesterase, the key enzyme to handle ester-based dyes, is synthesized in microsomes using eukaryotic cell-free protein synthesis platform and established as a viable calcium imaging tool to analyze native and cell-free synthesized ion channels.![]()
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Affiliation(s)
- Priyavathi Dhandapani
- Fraunhofer Institute of Cell Therapy and Immunology, Branch of Bioanalytics and Bioprocesses (IZI-BB) Am Muehlenberg 13 Potsdam-Golm Germany
| | - Srujan Kumar Dondapati
- Fraunhofer Institute of Cell Therapy and Immunology, Branch of Bioanalytics and Bioprocesses (IZI-BB) Am Muehlenberg 13 Potsdam-Golm Germany
| | - Anne Zemella
- Fraunhofer Institute of Cell Therapy and Immunology, Branch of Bioanalytics and Bioprocesses (IZI-BB) Am Muehlenberg 13 Potsdam-Golm Germany
| | - Dennis Bräuer
- Fraunhofer Institute of Cell Therapy and Immunology, Branch of Bioanalytics and Bioprocesses (IZI-BB) Am Muehlenberg 13 Potsdam-Golm Germany
| | - Doreen Anja Wüstenhagen
- Fraunhofer Institute of Cell Therapy and Immunology, Branch of Bioanalytics and Bioprocesses (IZI-BB) Am Muehlenberg 13 Potsdam-Golm Germany
| | - Stefan Mergler
- Department of Ophthalmology, Charité - Universitätsmedizin Berlin Campus Virchow-Hospital Berlin Germany
| | - Stefan Kubick
- Fraunhofer Institute of Cell Therapy and Immunology, Branch of Bioanalytics and Bioprocesses (IZI-BB) Am Muehlenberg 13 Potsdam-Golm Germany .,Faculty of Health Sciences, Joint Faculty of Brandenburg University of Technology, Cottbus - Senftenberg, Theodor Fontane Medical School of Brandenburg, University of Potsdam Germany
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11
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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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12
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Lemos FO, Bultynck G, Parys JB. A comprehensive overview of the complex world of the endo- and sarcoplasmic reticulum Ca 2+-leak channels. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2021; 1868:119020. [PMID: 33798602 DOI: 10.1016/j.bbamcr.2021.119020] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 01/23/2021] [Revised: 03/09/2021] [Accepted: 03/13/2021] [Indexed: 12/11/2022]
Abstract
Inside cells, the endoplasmic reticulum (ER) forms the largest Ca2+ store. Ca2+ is actively pumped by the SERCA pumps in the ER, where intraluminal Ca2+-binding proteins enable the accumulation of large amount of Ca2+. IP3 receptors and the ryanodine receptors mediate the release of Ca2+ in a controlled way, thereby evoking complex spatio-temporal signals in the cell. The steady state Ca2+ concentration in the ER of about 500 μM results from the balance between SERCA-mediated Ca2+ uptake and the passive leakage of Ca2+. The passive Ca2+ leak from the ER is often ignored, but can play an important physiological role, depending on the cellular context. Moreover, excessive Ca2+ leakage significantly lowers the amount of Ca2+ stored in the ER compared to normal conditions, thereby limiting the possibility to evoke Ca2+ signals and/or causing ER stress, leading to pathological consequences. The so-called Ca2+-leak channels responsible for Ca2+ leakage from the ER are however still not well understood, despite over 20 different proteins have been proposed to contribute to it. This review has the aim to critically evaluate the available evidence about the various channels potentially involved and to draw conclusions about their relative importance.
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Affiliation(s)
- Fernanda O Lemos
- KU Leuven, Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine and Leuven Kanker Instituut, Campus Gasthuisberg O/N-1 B-802, Herestraat 49, B-3000 Leuven, Belgium
| | - Geert Bultynck
- KU Leuven, Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine and Leuven Kanker Instituut, Campus Gasthuisberg O/N-1 B-802, Herestraat 49, B-3000 Leuven, Belgium
| | - Jan B Parys
- KU Leuven, Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine and Leuven Kanker Instituut, Campus Gasthuisberg O/N-1 B-802, Herestraat 49, B-3000 Leuven, Belgium.
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13
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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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14
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Wang X, Mick G, McCormick K. Pyridine nucleotide regulation of hepatic endoplasmic reticulum calcium uptake. Physiol Rep 2020; 7:e14151. [PMID: 31222964 PMCID: PMC6586769 DOI: 10.14814/phy2.14151] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Accepted: 05/31/2019] [Indexed: 01/03/2023] Open
Abstract
Pyridine nucleotides serve an array of intracellular metabolic functions such as, to name a few, shuttling electrons in enzymatic reactions, safeguarding the redox state against reactive oxygen species, cytochrome P450 (CYP) enzyme detoxification pathways and, relevant to this study, the regulation of ion fluxes. In particular, the maintenance of a steep calcium gradient between the cytosol and endoplasmic reticulum (ER), without which apoptosis ensues, is achieved by an elaborate combination of energy–requiring ER membrane pumps and efflux channels. In liver microsomes, net calcium uptake was inhibited by physiological concentrations of NADP. In the presence of 1 mmol/L NADP, calcium uptake was attenuated by nearly 80%, additionally, this inhibitory effect was blunted by concomitant addition of NADPH. No other nicotinamide containing compounds ‐save a slight inhibition by NAADP‐hindered calcium uptake; thus, only oxidized pyridine nucleotides, or related compounds with a phosphate moiety, had an imposing effect. Moreover, the NADP inhibition was evident even after selectively blocking ER calcium efflux channels. Given the fundamental role of endoplasmic calcium homeostasis, it is plausible that changes in cytosolic NADP concentration, for example, during anabolic processes, could regulate net ER calcium uptake.
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Affiliation(s)
- Xudong Wang
- Department of Pediatrics, University of Alabama at Birmingham, Birmingham, Alabama
| | - Gail Mick
- Department of Pediatrics, University of Alabama at Birmingham, Birmingham, Alabama
| | - Kenneth McCormick
- Department of Pediatrics, University of Alabama at Birmingham, Birmingham, Alabama
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15
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Gordaliza-Alaguero I, Cantó C, Zorzano A. Metabolic implications of organelle-mitochondria communication. EMBO Rep 2019; 20:e47928. [PMID: 31418169 DOI: 10.15252/embr.201947928] [Citation(s) in RCA: 87] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Revised: 05/10/2019] [Accepted: 05/28/2019] [Indexed: 12/31/2022] Open
Abstract
Cellular organelles are not static but show dynamism-a property that is likely relevant for their function. In addition, they interact with other organelles in a highly dynamic manner. In this review, we analyze the proteins involved in the interaction between mitochondria and other cellular organelles, especially the endoplasmic reticulum, lipid droplets, and lysosomes. Recent results indicate that, on one hand, metabolic alterations perturb the interaction between mitochondria and other organelles, and, on the other hand, that deficiency in proteins involved in the tethering between mitochondria and the ER or in specific functions of the interaction leads to metabolic alterations in a variety of tissues. The interaction between organelles is an emerging field that will permit to identify key proteins, to delineate novel modulation pathways, and to elucidate their implications in human disease.
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Affiliation(s)
- Isabel Gordaliza-Alaguero
- Institute for Research in Biomedicine (IRB Barcelona), Barcelona Institute of Science and Technology (BIST), Barcelona, Spain.,CIBER de Diabetes y Enfermedades Metabolicas Asociadas, Barcelona, Spain.,Departamento de Bioquimica i Biomedicina Molecular, Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain
| | - Carlos Cantó
- Nestle Institute of Health Sciences (NIHS), Lausanne, Switzerland.,School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Antonio Zorzano
- Institute for Research in Biomedicine (IRB Barcelona), Barcelona Institute of Science and Technology (BIST), Barcelona, Spain.,CIBER de Diabetes y Enfermedades Metabolicas Asociadas, Barcelona, Spain.,Departamento de Bioquimica i Biomedicina Molecular, Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain
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16
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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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17
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Liu H, Kurtoglu M, León-Annicchiarico CL, Munoz-Pinedo C, Barredo J, Leclerc G, Merchan J, Liu X, Lampidis TJ. Combining 2-deoxy-D-glucose with fenofibrate leads to tumor cell death mediated by simultaneous induction of energy and ER stress. Oncotarget 2017; 7:36461-36473. [PMID: 27183907 PMCID: PMC5095013 DOI: 10.18632/oncotarget.9263] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Accepted: 04/16/2016] [Indexed: 11/25/2022] Open
Abstract
Unregulated growth and replication as well as an abnormal microenvironment, leads to elevated levels of stress which is a common trait of cancer. By inducing both energy and endoplasmic reticulum (ER) stress, 2-Deoxy-glucose (2-DG) is particularly well-suited to take advantage of the therapeutic window that heightened stress in tumors provides. Under hypoxia, blocking glycolysis with 2-DG leads to significant lowering of ATP resulting in energy stress and cell death in numerous carcinoma cell types. In contrast, under normoxia, 2-DG at a low-concentration is not toxic in most carcinomas tested, but induces growth inhibition, which is primarily due to ER stress. Here we find a synergistic toxic effect in several tumor cell lines in vitro combining 2-DG with fenofibrate (FF), a drug that has been safely used for over 40 years to lower cholesterol in patients. This combination induces much greater energy stress than either agent alone, as measured by ATP reduction, increased p-AMPK and downregulation of mTOR. Inhibition of mTOR results in blockage of GRP78 a critical component of the unfolded protein response which we speculate leads to greater ER stress as observed by increased p-eIF2α. Moreover, to avoid an insulin response and adsorption by the liver, 2-DG is delivered by slow-release pump yielding significant anti-tumor control when combined with FF. Our results provide promise for developing this combination clinically and others that combine 2-DG with agents that act synergistically to selectively increase energy and ER stress to a level that is toxic to numerous tumor cell types.
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Affiliation(s)
- Huaping Liu
- Department of Cell Biology, University of Miami, Miller School of Medicine and Sylvester Comprehensive Cancer Center, Miami, FL, USA
| | | | - Clara Lucia León-Annicchiarico
- Cell Death Regulation Group, Bellvitage Biomedical Research Institute (IDIBELL), L'Hospitalet de Llobregat, Barcelona, Spain
| | - Cristina Munoz-Pinedo
- Cell Death Regulation Group, Bellvitage Biomedical Research Institute (IDIBELL), L'Hospitalet de Llobregat, Barcelona, Spain
| | - Julio Barredo
- Department of Pediatrics, University of Miami, Miller School of Medicine and Sylvester Comprehensive Cancer Center, Miami, FL, USA
| | - Guy Leclerc
- Department of Pediatrics, University of Miami, Miller School of Medicine and Sylvester Comprehensive Cancer Center, Miami, FL, USA
| | - Jaime Merchan
- Department of Medicine, University of Miami, Miller School of Medicine and Sylvester Comprehensive Cancer Center, Miami, FL, USA
| | - Xiongfei Liu
- Department of Cell Biology, University of Miami, Miller School of Medicine and Sylvester Comprehensive Cancer Center, Miami, FL, USA
| | - Theodore J Lampidis
- Department of Cell Biology, University of Miami, Miller School of Medicine and Sylvester Comprehensive Cancer Center, Miami, FL, USA
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18
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Periyasamy P, Shinohara T. Age-related cataracts: Role of unfolded protein response, Ca 2+ mobilization, epigenetic DNA modifications, and loss of Nrf2/Keap1 dependent cytoprotection. Prog Retin Eye Res 2017; 60:1-19. [PMID: 28864287 PMCID: PMC5600869 DOI: 10.1016/j.preteyeres.2017.08.003] [Citation(s) in RCA: 87] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Revised: 08/26/2017] [Accepted: 08/28/2017] [Indexed: 12/11/2022]
Abstract
Age-related cataracts are closely associated with lens chronological aging, oxidation, calcium imbalance, hydration and crystallin modifications. Accumulating evidence indicates that misfolded proteins are generated in the endoplasmic reticulum (ER) by most cataractogenic stresses. To eliminate misfolded proteins from cells before they can induce senescence, the cells activate a clean-up machinery called the ER stress/unfolded protein response (UPR). The UPR also activates the nuclear factor-erythroid-2-related factor 2 (Nrf2), a central transcriptional factor for cytoprotection against stress. Nrf2 activates nearly 600 cytoprotective target genes. However, if ER stress reaches critically high levels, the UPR activates destructive outputs to trigger programmed cell death. The UPR activates mobilization of ER-Ca2+ to the cytoplasm and results in activation of Ca2+-dependent proteases to cleave various enzymes and proteins which cause the loss of normal lens function. The UPR also enhances the overproduction of reactive oxygen species (ROS), which damage lens constituents and induce failure of the Nrf2 dependent cytoprotection. Kelch-like ECH-associated protein 1 (Keap1) is an oxygen sensor protein and regulates the levels of Nrf2 by the proteasomal degradation. A significant loss of DNA methylation in diabetic cataracts was found in the Keap1 promoter, which overexpresses the Keap1 protein. Overexpressed Keap1 significantly decreases the levels of Nrf2. Lower levels of Nrf2 induces loss of the redox balance toward to oxidative stress thereby leading to failure of lens cytoprotection. Here, this review summarizes the overall view of ER stress, increases in Ca2+ levels, protein cleavage, and loss of the well-established stress protection in somatic lens cells.
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Affiliation(s)
- Palsamy Periyasamy
- Department of Ophthalmology and Visual Sciences, University of Nebraska Medical Center, Omaha, NE 68198, USA; Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198, USA.
| | - Toshimichi Shinohara
- Department of Ophthalmology and Visual Sciences, University of Nebraska Medical Center, Omaha, NE 68198, USA
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19
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Leon-Aparicio D, Chavez-Reyes J, Guerrero-Hernandez A. Activation of endoplasmic reticulum calcium leak by 2-APB depends on the luminal calcium concentration. Cell Calcium 2017; 65:80-90. [DOI: 10.1016/j.ceca.2017.01.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2016] [Revised: 01/20/2017] [Accepted: 01/20/2017] [Indexed: 10/20/2022]
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20
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Gutiérrez T, Simmen T. Endoplasmic reticulum chaperones tweak the mitochondrial calcium rheostat to control metabolism and cell death. Cell Calcium 2017; 70:64-75. [PMID: 28619231 DOI: 10.1016/j.ceca.2017.05.015] [Citation(s) in RCA: 73] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Revised: 05/24/2017] [Accepted: 05/24/2017] [Indexed: 12/16/2022]
Abstract
The folding of secretory proteins is a well-understood mechanism, based on decades of research on endoplasmic reticulum (ER) chaperones. These chaperones interact with newly imported polypeptides close to the ER translocon. Classic examples for these proteins include the immunoglobulin binding protein (BiP/GRP78), and the lectins calnexin and calreticulin. Although not considered chaperones per se, the ER oxidoreductases of the protein disulfide isomerase (PDI) family complete the folding job by catalyzing the formation of disulfide bonds through cysteine oxidation. Research from the past decade has demonstrated that ER chaperones are multifunctional proteins. The regulation of ER-mitochondria Ca2+ crosstalk is one of their additional functions, as shown for calnexin, BiP/GRP78 or the oxidoreductases Ero1α and TMX1. This function depends on interactions of this group of proteins with the ER Ca2+ handling machinery. This novel function makes perfect sense for two reasons: i. It allows ER chaperones to control mitochondrial apoptosis instantly without a lengthy bypass involving the upregulation of pro-apoptotic transcription factors via the unfolded protein response (UPR); and ii. It allows the ER protein folding machinery to fine-tune ATP import via controlling the speed of mitochondrial oxidative phosphorylation. Therefore, the role of ER chaperones in regulating ER-mitochondria Ca2+ flux identifies the progression of secretory protein folding as a central regulator of cell survival and death, at least in cell types that secrete large amount of proteins. In other cell types, ER protein folding might serve as a sentinel mechanism that monitors cellular well-being to control cell metabolism and apoptosis. The selenoprotein SEPN1 is a classic example for such a role. Through the control of ER-mitochondria Ca2+-flux, ER chaperones and folding assistants guide cellular apoptosis and mitochondrial metabolism.
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Affiliation(s)
- Tomas Gutiérrez
- Faculty of Medicine and Dentistry, Department of Cell Biology, University of Alberta, Edmonton, T6G2H7, Canada
| | - Thomas Simmen
- Faculty of Medicine and Dentistry, Department of Cell Biology, University of Alberta, Edmonton, T6G2H7, Canada,.
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21
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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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22
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Cassel R, Ducreux S, Alam MR, Dingreville F, Berlé C, Burda-Jacob K, Chauvin MA, Chikh K, Païta L, Al-Mawla R, Crola Da Silva C, Rieusset J, Thivolet C, Van Coppenolle F, Madec AM. Protection of Human Pancreatic Islets from Lipotoxicity by Modulation of the Translocon. PLoS One 2016; 11:e0148686. [PMID: 26862742 PMCID: PMC4749224 DOI: 10.1371/journal.pone.0148686] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2015] [Accepted: 01/20/2016] [Indexed: 12/04/2022] Open
Abstract
Type 2 diabetes is characterized by peripheral insulin resistance and pancreatic beta cell dysfunction. Elevated free fatty acids (FFAs) may impair beta cell function and mass (lipotoxicity). Altered calcium homeostasis may be involved in defective insulin release. The endoplasmic reticulum (ER) is the major intracellular calcium store. Lipotoxicity induces ER stress and in parallel an ER calcium depletion through unknown ER calcium leak channels. The main purposes of this study is first to identify one of these channels and secondly, to check the opportunity to restore beta cells function (i.e., insulin secretion) after pharmacological inhibition of ER calcium store depletion. We investigated the functionality of translocon, an ER calcium leak channel and its involvement on FFAs-induced alterations in MIN6B1 cells and in human pancreatic islets. We evidenced that translocon acts as a functional ER calcium leak channel in human beta cells using anisomycin and puromycin (antibiotics), respectively blocker and opener of this channel. Puromycin induced a significant ER calcium release, inhibited by anisomycin pretreatment. Palmitate treatment was used as FFA model to induce a mild lipotoxic effect: ER calcium content was reduced, ER stress but not apoptosis were induced and glucose induced insulin secretion was decreased in our beta cells. Interestingly, translocon inhibition by chronic anisomycin treatment prevented dysfunctions induced by palmitate, avoiding reticular calcium depletion, ER stress and restoring insulin secretion. Our results provide for the first time compelling evidence that translocon actively participates to the palmitate-induced ER calcium leak and insulin secretion decrease in beta cells. Its inhibition reduces these lipotoxic effects. Taken together, our data indicate that TLC may be a new potential target for the treatment of type 2 diabetes.
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Affiliation(s)
- R. Cassel
- Inserm UMR-U1060 CarMeN Laboratory, University Lyon 1, INRA U1235, INSA-Lyon, Facultés de médecine Charles Mérieux Lyon-Sud, F-69003 Lyon, France
| | - S. Ducreux
- Inserm UMR-U1060 CarMeN Laboratory, University Lyon 1, INRA U1235, INSA-Lyon, Facultés de médecine Rockefeller, F-69003 Lyon, France
| | - M. R. Alam
- Inserm UMR-U1060 CarMeN Laboratory, University Lyon 1, INRA U1235, INSA-Lyon, Facultés de médecine Rockefeller, F-69003 Lyon, France
| | - F. Dingreville
- Inserm UMR-U1060 CarMeN Laboratory, University Lyon 1, INRA U1235, INSA-Lyon, Facultés de médecine Charles Mérieux Lyon-Sud, F-69003 Lyon, France
| | - C. Berlé
- Inserm UMR-U1060 CarMeN Laboratory, University Lyon 1, INRA U1235, INSA-Lyon, Facultés de médecine Charles Mérieux Lyon-Sud, F-69003 Lyon, France
| | - K. Burda-Jacob
- Inserm UMR-U1060 CarMeN Laboratory, University Lyon 1, INRA U1235, INSA-Lyon, Facultés de médecine Charles Mérieux Lyon-Sud, F-69003 Lyon, France
| | - M. A. Chauvin
- Inserm UMR-U1060 CarMeN Laboratory, University Lyon 1, INRA U1235, INSA-Lyon, Facultés de médecine Charles Mérieux Lyon-Sud, F-69003 Lyon, France
| | - K. Chikh
- Inserm UMR-U1060 CarMeN Laboratory, University Lyon 1, INRA U1235, INSA-Lyon, Facultés de médecine Charles Mérieux Lyon-Sud, F-69003 Lyon, France
| | - L. Païta
- Inserm UMR-U1060 CarMeN Laboratory, University Lyon 1, INRA U1235, INSA-Lyon, Facultés de médecine Rockefeller, F-69003 Lyon, France
| | - R. Al-Mawla
- Inserm UMR-U1060 CarMeN Laboratory, University Lyon 1, INRA U1235, INSA-Lyon, Facultés de médecine Rockefeller, F-69003 Lyon, France
| | - C. Crola Da Silva
- Inserm UMR-U1060 CarMeN Laboratory, University Lyon 1, INRA U1235, INSA-Lyon, Facultés de médecine Rockefeller, F-69003 Lyon, France
| | - J. Rieusset
- Inserm UMR-U1060 CarMeN Laboratory, University Lyon 1, INRA U1235, INSA-Lyon, Facultés de médecine Charles Mérieux Lyon-Sud, F-69003 Lyon, France
| | - C. Thivolet
- Inserm UMR-U1060 CarMeN Laboratory, University Lyon 1, INRA U1235, INSA-Lyon, Facultés de médecine Charles Mérieux Lyon-Sud, F-69003 Lyon, France
- Hospices Civils de Lyon, Hôpital Lyon-Sud, Service d’Endocrinologie, Diabétologie et Nutrition, F-69310 Pierre Bénite, France
| | - F. Van Coppenolle
- Inserm UMR-U1060 CarMeN Laboratory, University Lyon 1, INRA U1235, INSA-Lyon, Facultés de médecine Rockefeller, F-69003 Lyon, France
| | - A. M. Madec
- Inserm UMR-U1060 CarMeN Laboratory, University Lyon 1, INRA U1235, INSA-Lyon, Facultés de médecine Charles Mérieux Lyon-Sud, F-69003 Lyon, France
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Schorr S, Klein MC, Gamayun I, Melnyk A, Jung M, Schäuble N, Wang Q, Hemmis B, Bochen F, Greiner M, Lampel P, Urban SK, Hassdenteufel S, Dudek J, Chen XZ, Wagner R, Cavalié A, Zimmermann R. Co-chaperone Specificity in Gating of the Polypeptide Conducting Channel in the Membrane of the Human Endoplasmic Reticulum. J Biol Chem 2015; 290:18621-35. [PMID: 26085089 DOI: 10.1074/jbc.m115.636639] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Indexed: 11/06/2022] Open
Abstract
In mammalian cells, signal peptide-dependent protein transport into the endoplasmic reticulum (ER) is mediated by a dynamic polypeptide-conducting channel, the heterotrimeric Sec61 complex. Previous work has characterized the Sec61 complex as a potential ER Ca(2+) leak channel in HeLa cells and identified ER lumenal molecular chaperone immunoglobulin heavy-chain-binding protein (BiP) as limiting Ca(2+) leakage via the open Sec61 channel by facilitating channel closing. This BiP activity involves binding of BiP to the ER lumenal loop 7 of Sec61α in the vicinity of tyrosine 344. Of note, the Y344H mutation destroys the BiP binding site and causes pancreatic β-cell apoptosis and diabetes in mice. Here, we systematically depleted HeLa cells of the BiP co-chaperones by siRNA-mediated gene silencing and used live cell Ca(2+) imaging to monitor the effects on ER Ca(2+) leakage. Depletion of either one of the ER lumenal BiP co-chaperones, ERj3 and ERj6, but not the ER membrane-resident co-chaperones (such as Sec63 protein, which assists BiP in Sec61 channel opening) led to increased Ca(2+) leakage via Sec6 complex, thereby phenocopying the effect of BiP depletion. Thus, BiP facilitates Sec61 channel closure (i.e. limits ER Ca(2+) leakage) via the Sec61 channel with the help of ERj3 and ERj6. Interestingly, deletion of ERj6 causes pancreatic β-cell failure and diabetes in mice and humans. We suggest that co-chaperone-controlled gating of the Sec61 channel by BiP is particularly important for cells, which are highly active in protein secretion, and that breakdown of this regulatory mechanism can cause apoptosis and disease.
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Affiliation(s)
- Stefan Schorr
- From the Departments of Medical Biochemistry and Molecular Biology and
| | | | - Igor Gamayun
- Experimental and Clinical Pharmacology and Toxicology, Saarland University, 66421 Homburg, Germany
| | - Armin Melnyk
- From the Departments of Medical Biochemistry and Molecular Biology and
| | - Martin Jung
- From the Departments of Medical Biochemistry and Molecular Biology and
| | - Nico Schäuble
- From the Departments of Medical Biochemistry and Molecular Biology and
| | - Qian Wang
- the Department of Physiology, University of Alberta, Edmonton T6G 2H7, Canada, and
| | - Birgit Hemmis
- the Division of Biophysics, Universität Osnabrück, FB Biologie/Chemie, 49076 Osnabrück, Germany
| | - Florian Bochen
- From the Departments of Medical Biochemistry and Molecular Biology and
| | - Markus Greiner
- From the Departments of Medical Biochemistry and Molecular Biology and
| | - Pavel Lampel
- From the Departments of Medical Biochemistry and Molecular Biology and
| | | | | | - Johanna Dudek
- From the Departments of Medical Biochemistry and Molecular Biology and
| | - Xing-Zhen Chen
- the Department of Physiology, University of Alberta, Edmonton T6G 2H7, Canada, and
| | - Richard Wagner
- the Division of Biophysics, Universität Osnabrück, FB Biologie/Chemie, 49076 Osnabrück, Germany
| | - Adolfo Cavalié
- Experimental and Clinical Pharmacology and Toxicology, Saarland University, 66421 Homburg, Germany
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Abstract
In mammalian cells, the rough endoplasmic reticulum or ER plays a central role in the biogenesis of most extracellular plus many organellar proteins and in cellular calcium homeostasis. Therefore, this organelle comprises molecular chaperones that are involved in import, folding/assembly, export, and degradation of polypeptides in millimolar concentrations. In addition, there are calcium channels/pumps and signal transduction components present in the ER membrane that affect and are affected by these processes. The ER lumenal Hsp70, termed immunoglobulin-heavy chain binding protein or BiP, is the central player in all these activities and involves up to seven different co-chaperones, i.e. ER-membrane integrated as well as ER-lumenal Hsp40s, which are termed ERj or ERdj, and two nucleotide exchange factors.
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25
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Takeshima H, Venturi E, Sitsapesan R. New and notable ion-channels in the sarcoplasmic/endoplasmic reticulum: do they support the process of intracellular Ca²⁺ release? J Physiol 2014; 593:3241-51. [PMID: 26228553 DOI: 10.1113/jphysiol.2014.281881] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Accepted: 10/10/2014] [Indexed: 12/11/2022] Open
Abstract
Intracellular Ca(2+) release through ryanodine receptor (RyR) and inositol trisphosphate receptor (IP3 R) channels is supported by a complex network of additional proteins that are located in or near the Ca(2+) release sites. In this review, we focus, not on RyR/IP3 R, but on other ion-channels that are known to be present in the sarcoplasmic/endoplasmic reticulum (ER/SR) membranes. We review their putative physiological roles and the evidence suggesting that they may support the process of intracellular Ca(2+) release, either indirectly by manipulating ionic fluxes across the ER/SR membrane or by directly interacting with a Ca(2+) -release channel. These channels rarely receive scientific attention because of the general lack of information regarding their biochemical and/or electrophysiological characteristics makes it difficult to predict their physiological roles and their impact on SR Ca(2+) fluxes. We discuss the possible role of SR K(+) channels and, in parallel, detail the known biochemical and biophysical properties of the trimeric intracellular cation (TRIC) proteins and their possible biological and pathophysiological roles in ER/SR Ca(2+) release. We summarise what is known regarding Cl(-) channels in the ER/SR and the non-selective cation channels or putative 'Ca(2+) leak channels', including mitsugumin23 (MG23), pannexins, presenilins and the transient receptor potential (TRP) channels that are distributed across ER/SR membranes but which have not yet been fully characterised functionally.
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Affiliation(s)
- Hiroshi Takeshima
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, 606-8501, Japan
| | - Elisa Venturi
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK
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26
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Endoplasmic reticulum stress in insulin resistance and diabetes. Cell Calcium 2014; 56:311-22. [PMID: 25239386 DOI: 10.1016/j.ceca.2014.08.006] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Accepted: 08/07/2014] [Indexed: 02/07/2023]
Abstract
The endoplasmic reticulum is the main intracellular Ca(2+) store for Ca(2+) release during cell signaling. There are different strategies to avoid ER Ca(2+) depletion. Release channels utilize first Ca(2+)-bound to proteins and this minimizes the reduction of the free luminal [Ca(2+)]. However, if release channels stay open after exhaustion of Ca(2+)-bound to proteins, then the reduction of the free luminal ER [Ca(2+)] (via STIM proteins) activates Ca(2+) entry at the plasma membrane to restore the ER Ca(2+) load, which will work provided that SERCA pump is active. Nevertheless, there are several noxious conditions that result in decreased activity of the SERCA pump such as oxidative stress, inflammatory cytokines, and saturated fatty acids, among others. These conditions result in a deficient restoration of the ER [Ca(2+)] and lead to the ER stress response that should facilitate recovery of the ER. However, if the stressful condition persists then ER stress ends up triggering cell death and the ensuing degenerative process leads to diverse pathologies; particularly insulin resistance, diabetes and several of the complications associated with diabetes. This scenario suggests that limiting ER stress should decrease the incidence of diabetes and the mobility and mortality associated with this illness.
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Haßdenteufel S, Klein MC, Melnyk A, Zimmermann R. Protein transport into the human ER and related diseases, Sec61-channelopathies. Biochem Cell Biol 2014; 92:499-509. [PMID: 24934166 DOI: 10.1139/bcb-2014-0043] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Protein transport into the human endoplasmic reticulum (ER) is relevant to the biogenesis of most soluble and membrane proteins of organelles, which are involved in endo- or exo-cytsosis. It involves amino-terminal signal peptides in the precursor polypeptides and various transport components in the cytosol plus the ER, and can occur co- or post-translationally. The two mechanisms merge at the level of the ER membrane, specifically at the level of the heterotrimeric Sec61 complex, which forms a dynamic polypeptide-conducting channel in the ER membrane. Since the mammalian ER is also the main intracellular calcium storage organelle, and the Sec61 complex is calcium permeable, the Sec61 complex is tightly regulated in its equilibrium between the closed and open conformations, or "gated", by ligands, such as signal peptides of the transport substrates and the ER lumenal Hsp70-type molecular chaperone BiP. Furthermore, BiP binding to the incoming polypeptide contributes to the efficiency and unidirectionality of transport. Recent insights into the structure and dynamic equilibrium of the Sec61 complex have various mechanistic as well as medical implications.
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Affiliation(s)
- Sarah Haßdenteufel
- Medical Biochemistry & Molecular Biology, Saarland University, Building 44, Kirrbergerstr, D-66421 Homburg, Germany
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28
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Johnson GG, White MC, Wu JH, Vallejo M, Grimaldi M. The deadly connection between endoplasmic reticulum, Ca2+, protein synthesis, and the endoplasmic reticulum stress response in malignant glioma cells. Neuro Oncol 2014; 16:1086-99. [PMID: 24569545 DOI: 10.1093/neuonc/nou012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND The endoplasmic reticulum (ER) is involved in Ca(2+) signaling and protein processing. Accumulation of unfolded proteins following ER Ca(2+) depletion triggers the ER stress response (ERSR), which facilitates protein folding and removal of damaged proteins and can induce cell death. Unfolded proteins bind to chaperones, such as the glucose-regulated protein (GRP)78 and cause the release of GRP78-repressed proteins executing ERSR. METHODS Several glioma cell lines and primary astrocytes were used to analyze ERSR using standard western blots, reverse transcription-PCR, viability assays, and single cell Ca(2+) imaging. RESULTS ERSR induction with thapsigargin results in a more intense ERSR associated with a larger loss of ER Ca(2+), activation of ER-associated caspases (4/12) and caspase 3, and a higher rate of malignant glioma cell death than in normal glial cells. Malignant glioma cells have higher levels of protein synthesis and expression of the translocon (a component of the ribosomal complex, guiding protein entry in the ER), the activity of which is associated with the loss of ER Ca(2+). Our experiments confirm increased expression of the translocon in malignant glioma cells. In addition, blockade of the ribosome-translocon complex with agents differently affecting translocon Ca(2+) permeability causes opposite effects on ERSR deployment and death of malignant glioma cells. CONCLUSIONS Excessive ER Ca(2+) loss due to translocon activity appears to be responsible for the enhancement of ERSR, leading to the death of glioma cells. The results reveal a characteristic of malignant glioma cells that could be exploited to develop new therapeutic strategies to treat incurable glial malignancies.
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Affiliation(s)
- Guyla G Johnson
- Laboratory of Neuropharmacology, Department of Biochemistry and Molecular Biology, Southern Research Institute, Birmingham, Alabama (G.G.J., M.C.W., J-H.W., M.G.); Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama (M.V.)
| | - Misti C White
- Laboratory of Neuropharmacology, Department of Biochemistry and Molecular Biology, Southern Research Institute, Birmingham, Alabama (G.G.J., M.C.W., J-H.W., M.G.); Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama (M.V.)
| | - Jian-He Wu
- Laboratory of Neuropharmacology, Department of Biochemistry and Molecular Biology, Southern Research Institute, Birmingham, Alabama (G.G.J., M.C.W., J-H.W., M.G.); Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama (M.V.)
| | - Matthew Vallejo
- Laboratory of Neuropharmacology, Department of Biochemistry and Molecular Biology, Southern Research Institute, Birmingham, Alabama (G.G.J., M.C.W., J-H.W., M.G.); Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama (M.V.)
| | - Maurizio Grimaldi
- Laboratory of Neuropharmacology, Department of Biochemistry and Molecular Biology, Southern Research Institute, Birmingham, Alabama (G.G.J., M.C.W., J-H.W., M.G.); Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama (M.V.)
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29
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Paredes RM, Bollo M, Holstein D, Lechleiter JD. Luminal Ca2+ depletion during the unfolded protein response in Xenopus oocytes: cause and consequence. Cell Calcium 2013; 53:286-96. [PMID: 23415071 DOI: 10.1016/j.ceca.2013.01.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Revised: 01/15/2013] [Accepted: 01/18/2013] [Indexed: 01/22/2023]
Abstract
The endoplasmic reticulum (ER) is a Ca(2+) storing organelle that plays a critical role in the synthesis, folding and post-translational modifications of many proteins. The ER enters into a condition of stress when the load of newly synthesized proteins exceeds its folding and processing capacity. This activates a signal transduction pathway called the unfolded protein response (UPR) that attempts to restore homeostasis. The precise role of ER Ca(2+) in the initiation of the UPR has not been defined. Specifically, it has not been established whether ER Ca(2+) dysregulation is a cause or consequence of ER stress. Here, we report that partial depletion of ER Ca(2+) stores induces a significant induction of the UPR, and leads to the retention of a normally secreted protein Carboxypeptidase Y. Moreover, inhibition of protein glycosylation by tunicamycin rapidly induced an ER Ca(2+) leak into the cytosol. However, blockade of the translocon with emetine inhibited the tunicamycin-induced Ca(2+) release. Furthermore, emetine treatment blocked elF2α phosphorylation and reduced expression of the chaperone BiP. These findings suggest that Ca(2+) may be both a cause and a consequence of ER protein misfolding. Thus, it appears that ER Ca(2+) leak is a significant co-factor for the initiation of the UPR.
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Affiliation(s)
- R Madelaine Paredes
- Department of Cellular and Structural Biology, University of Texas Health Science Center at San Antonio (UTHSCSA), San Antonio, TX 78229-3900, USA
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30
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Transport and distribution of 45Ca2+ in the perfused rat liver and the influence of adjuvant-induced arthritis. Biochim Biophys Acta Mol Basis Dis 2013; 1832:249-62. [DOI: 10.1016/j.bbadis.2012.10.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2012] [Revised: 09/30/2012] [Accepted: 10/06/2012] [Indexed: 12/22/2022]
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Jacobs-Harper A, Crumbly A, Romani A. Acute effect of ethanol on hepatic reticular G6Pase and Ca2+ pool. Alcohol Clin Exp Res 2013; 37 Suppl 1:E40-51. [PMID: 22958133 PMCID: PMC3519974 DOI: 10.1111/j.1530-0277.2012.01933.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2011] [Accepted: 06/21/2012] [Indexed: 11/25/2022]
Abstract
BACKGROUND Hydrolysis of glucose 6-phosphate (G6P) via glucose 6-phosphatase (G6Pase) enlarges the reticular Ca(2+) pool of the hepatocyte. Exposure of liver cells to ethanol (EtOH) impairs reticular Ca(2+) homeostasis. The present study investigated the effect of acute EtOH administration on G6P-supported Ca(2+) accumulation in liver cells. METHODS Total microsomes were isolated from rat livers acutely perfused with varying doses of EtOH (0.01, 0.1, or 1% v/v) for 8 minutes. Calcium uptake was assessed by (45) Ca redistribution. Inorganic phosphate (Pi) formation was measured as an indicator of G6Pase hydrolytic activity. RESULTS G6P-supported Ca(2+) uptake decreased in a manner directly proportional to the dose of EtOH infused in the liver, whereas Ca(2+) uptake via SERCA pumps was decreased by ~25% only at the highest dose of alcohol administered. The reduced accumulation of Ca(2+) within the microsomes resulted in a smaller inositol 1,4,5-trisphosphate (IP(3))-induced Ca(2+) release. Kinetic assessment of IP(3) and passive Ca(2+) release indicated a faster mobilization in microsomes from EtOH-treated livers, suggesting alcohol-induced alteration of Ca(2+) releasing mechanisms. Pretreatment of livers with chloromethiazole (CMZ) or dithiothreitol (DTT), but not 4-methyl-pyrazole prevented the inhibitory effect of EtOH on G6Pase activity and Ca(2+) homeostasis. CONCLUSIONS Liver G6Pase activity and IP(3) -mediated Ca(2+) release are rapidly inhibited following acute (8 minutes) exposure to EtOH, thus compromising the ability of the endoplasmic reticulum to dynamically modulate Ca(2+) homeostasis in the hepatocyte. The protective effect of CMZ and DTT suggests that the inhibitory effect of EtOH is mediated through its metabolism via reticular cyP4502E1 and consequent free radicals formation.
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Affiliation(s)
- Amy Jacobs-Harper
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, US
| | - Ashlee Crumbly
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, US
| | - Andrea Romani
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, US
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Schäuble N, Lang S, Jung M, Cappel S, Schorr S, Ulucan Ö, Linxweiler J, Dudek J, Blum R, Helms V, Paton AW, Paton JC, Cavalié A, Zimmermann R. BiP-mediated closing of the Sec61 channel limits Ca2+ leakage from the ER. EMBO J 2012; 31:3282-96. [PMID: 22796945 PMCID: PMC3411083 DOI: 10.1038/emboj.2012.189] [Citation(s) in RCA: 126] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Accepted: 06/20/2012] [Indexed: 01/08/2023] Open
Abstract
In mammalian cells, signal peptide-dependent protein transport into the endoplasmic reticulum (ER) is mediated by a dynamic protein-conducting channel, the Sec61 complex. Previous work has characterized the Sec61 channel as a potential ER Ca(2+) leak channel and identified calmodulin as limiting Ca(2+) leakage in a Ca(2+)-dependent manner by binding to an IQ motif in the cytosolic aminoterminus of Sec61α. Here, we manipulated the concentration of the ER lumenal chaperone BiP in cells in different ways and used live cell Ca(2+) imaging to monitor the effects of reduced levels of BiP on ER Ca(2+) leakage. Regardless of how the BiP concentration was lowered, the absence of available BiP led to increased Ca(2+) leakage via the Sec61 complex. When we replaced wild-type Sec61α with mutant Sec61αY344H in the same model cell, however, Ca(2+) leakage from the ER increased and was no longer affected by manipulation of the BiP concentration. Thus, BiP limits ER Ca(2+) leakage through the Sec61 complex by binding to the ER lumenal loop 7 of Sec61α in the vicinity of tyrosine 344.
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Affiliation(s)
- Nico Schäuble
- Department of Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
| | - Sven Lang
- Department of Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
| | - Martin Jung
- Department of Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
| | - Sabine Cappel
- Department of Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
| | - Stefan Schorr
- Department of Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
| | - Özlem Ulucan
- Department of Computational Biology, Saarland University, Saarbrücken, Germany
| | - Johannes Linxweiler
- Department of Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
| | - Johanna Dudek
- Department of Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
| | - Robert Blum
- Department of Clinical Neurobiology, Würzburg University, Würzburg, Germany
| | - Volkhard Helms
- Department of Computational Biology, Saarland University, Saarbrücken, Germany
| | - Adrienne W Paton
- Research Centre for Infectious Disease, School of Molecular and Biomedical Science, University of Adelaide, South Australia, Australia
| | - James C Paton
- Research Centre for Infectious Disease, School of Molecular and Biomedical Science, University of Adelaide, South Australia, Australia
| | - Adolfo Cavalié
- Department of Experimental and Clinical Pharmacology and Toxicology, Saarland University, Homburg, Germany
| | - Richard Zimmermann
- Department of Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
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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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Bogeski I, Kappl R, Kummerow C, Gulaboski R, Hoth M, Niemeyer BA. Redox regulation of calcium ion channels: Chemical and physiological aspects. Cell Calcium 2011; 50:407-23. [DOI: 10.1016/j.ceca.2011.07.006] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2011] [Accepted: 07/26/2011] [Indexed: 02/07/2023]
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Lang S, Schäuble N, Cavalié A, Zimmermann R. Live cell calcium imaging combined with siRNA mediated gene silencing identifies Ca²⁺ leak channels in the ER membrane and their regulatory mechanisms. J Vis Exp 2011:e2730. [PMID: 21775954 PMCID: PMC3196168 DOI: 10.3791/2730] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
In mammalian cells, the endoplasmic reticulum (ER) plays a key role in protein biogenesis as well as in calcium signalling1. The heterotrimeric Sec61 complex in the ER membrane provides an aqueous path for newly-synthesized polypeptides into the lumen of the ER. Recent work from various laboratories suggested that this heterotrimeric complex may also form transient Ca2+ leak channels2-8. The key observation for this notion was that release of nascent polypeptides from the ribosome and Sec61 complex by puromycin leads to transient release of Ca2+ from the ER. Furthermore, it had been observed in vitro that the ER luminal protein BiP is involved in preventing ion permeability at the level of the Sec61 complex9,10. We have established an experimental system that allows us to directly address the role of the Sec61 complex as potential Ca2+ leak channel and to characterize its putative regulatory mechanisms11-13. This system combines siRNA mediated gene silencing and live cell Ca2+ imaging13. Cells are treated with siRNAs that are directed against the coding and untranslated region (UTR), respectively, of the SEC61A1 gene or a negative control siRNA. In complementation analysis, the cells are co-transfected with an IRES-GFP vector that allows the siRNA-resistant expression of the wildtype SEC61A1 gene. Then the cells are loaded with the ratiometric Ca2+-indicator FURA-2 to monitor simultaneously changes in the cytosolic Ca2+ concentration in a number of cells via a fluorescence microscope. The continuous measurement of cytosolic Ca2+ also allows the evaluation of the impact of various agents, such as puromycin, small molecule inhibitors, and thapsigargin on Ca2+ leakage. This experimental system gives us the unique opportunities to i) evaluate the contribution of different ER membrane proteins to passive Ca2+ efflux from the ER in various cell types, ii) characterize the proteins and mechanisms that limit this passive Ca2+ efflux, and iii) study the effects of disease linked mutations in the relevant components.
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Affiliation(s)
- Sven Lang
- Medical Biochemistry and Molecular Biology, Saarland University
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Greiner M, Kreutzer B, Lang S, Jung V, Cavalié A, Unteregger G, Zimmermann R, Wullich B. Sec62 protein level is crucial for the ER stress tolerance of prostate cancer. Prostate 2011; 71:1074-83. [PMID: 21557272 DOI: 10.1002/pros.21324] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2010] [Accepted: 11/22/2010] [Indexed: 11/10/2022]
Abstract
BACKGROUND We previously reported that over-expression of the SEC62 gene is a widespread phenomenon in prostate cancer. Since the use of endoplasmic reticulum (ER) stress-inducing substances such as thapsigargin in prostate cancer therapy is widely discussed in the literature, we investigated the influence of Sec62 protein content on the cellular response to these drugs. METHODS Growth effects were analyzed by real-time cell analysis and viability tests in DU145-cells representing an increased SEC62 expression or PC3- and LNCaP-cells representing a similar SEC62 expression compared to non-tumor cells. Ca(2+) -imaging in an established HeLa-system with fluorescent dye was used to study molecular effects of Sec62 depletion. RESULTS We found a lower propensity toward apoptotic cell death after thapsigargin treatment for DU145 cells compared to PC3 or LNCaP and siRNA-mediated silencing of SEC62 resulted in a reduced viability of thapsigargin-treated PC3 cells, indicating that Sec62 functions in cellular stress response. Measurement of cytosolic [Ca(2+) ] demonstrated the influence of Sec62 on the cellular response to thapsigargin on a molecular level. Using real-time cell analysis, we observed the loss of androgen stimulation of LNCaP cells in the presence of thapsigargin, and an additional negative effect on cell growth of Sec62 depletion. Also, for PC3- and DU145-cells Sec62 depletion inhibited growth after thapsigargin treatment. CONCLUSIONS Our data indicate a crucial function of Sec62 in the response to thapsigargin-induced ER stress. This will be of great significance on the background of elevated Sec62 protein levels in prostate cancer cells when treatment with thapsigargin analogs is considered.
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Affiliation(s)
- Markus Greiner
- Department of Medical Biochemistry and Molecular Biology, Saarland University, Homburg/Saar, Germany.
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37
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Barfell A, Crumbly A, Romani A. Enhanced glucose 6-phosphatase activity in liver of rats exposed to Mg(2+)-deficient diet. Arch Biochem Biophys 2011; 509:157-63. [PMID: 21402051 DOI: 10.1016/j.abb.2011.03.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2011] [Revised: 03/03/2011] [Accepted: 03/04/2011] [Indexed: 11/18/2022]
Abstract
Total hepatic Mg(2+) content decreases by >25% in animals maintained for 2 weeks on Mg(2+) deficient diet, and results in a >25% increase in glucose 6-phosphatase (G6Pase) activity in isolated liver microsomes in the absence of significant changed in enzyme expression. Incubation of Mg(2+)-deficient microsomes in the presence of 1mM external Mg(2+) returned G6Pase activity to levels measured in microsomes from animals on normal Mg(2+) diet. EDTA addition dynamically reversed the Mg(2+) effect. The effect of Mg(2+) or EDTA persisted in taurocholic acid permeabilized microsomes. An increase in G6Pase activity was also observed in liver microsomes from rats starved overnight, which presented a ~15% decrease in hepatic Mg(2+) content. In this model, G6Pase activity increased to a lesser extent than in Mg(2+)-deficient microsomes, but it could still be dynamically modulated by addition of Mg(2+) or EDTA. Our results indicate that (1) hepatic Mg(2+) content rapidly decreases following starvation or exposure to deficient diet, and (2) the loss of Mg(2+) stimulates G6P transport and hydrolysis as a possible compensatory mechanism to enhance intrahepatic glucose availability. The Mg(2+) effect appears to take place at the level of the substrate binding site of the G6Pase enzymatic complex or the surrounding phospholipid environment.
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Affiliation(s)
- Andrew Barfell
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH 44106-4970, USA
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38
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Venturi E, Mio K, Nishi M, Ogura T, Moriya T, Pitt SJ, Okuda K, Kakizawa S, Sitsapesan R, Sato C, Takeshima H. Mitsugumin 23 forms a massive bowl-shaped assembly and cation-conducting channel. Biochemistry 2011; 50:2623-32. [PMID: 21381722 PMCID: PMC3065873 DOI: 10.1021/bi1019447] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Mitsugumin 23 (MG23) is a 23 kDa transmembrane protein localized to the sarcoplasmic/endoplasmic reticulum and nuclear membranes in a wide variety of cells. Although the characteristics imply the participation in a fundamental function in intracellular membrane systems, the physiological role of MG23 is unknown. Here we report the biochemical and biophysical characterization of MG23. Hydropathicity profile and limited proteolytic analysis proposed three transmembrane segments in the MG23 primary structure. Chemical cross-linking analysis suggested a homo-oligomeric assembly of MG23. Ultrastructural observations detected a large symmetrical particle as the predominant component and a small asymmetric assembly as the second major component in highly purified MG23 preparations. Single-particle three-dimensional reconstruction revealed that MG23 forms a large bowl-shaped complex equipped with a putative central pore, which is considered an assembly of the small asymmetric subunit. After reconstitution into planar phospholipid bilayers, purified MG23 behaved as a voltage-dependent, cation-conducting channel, permeable to both K(+) and Ca(2+). A feature of MG23 gating was that multiple channels always appeared to be gating together in the bilayer. Our observations suggest that the bowl-shaped MG23 can transiently assemble and disassemble. These building transitions may underlie the unusual channel gating behavior of MG23 and allow rapid cationic flux across intracellular membrane systems.
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Affiliation(s)
- Elisa Venturi
- School of Physiology and Pharmacology, Bristol Heart Institute and Centre for Nanoscience and Quantum Information, University of Bristol, Bristol, United Kingdom
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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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Pannexin channels in ATP release and beyond: an unexpected rendezvous at the endoplasmic reticulum. Cell Signal 2010; 23:305-16. [PMID: 20688156 DOI: 10.1016/j.cellsig.2010.07.018] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2010] [Accepted: 07/22/2010] [Indexed: 01/13/2023]
Abstract
The pannexin (Panx) family of proteins, which is co-expressed with connexins (Cxs) in vertebrates, was found to be a new GJ-forming protein family related to invertebrate innexins. During the past ten years, different studies showed that Panxs mainly form hemichannels in the plasma membrane and mediate paracrine signalling by providing a flux pathway for ions such as Ca²(+), for ATP and perhaps for other compounds, in response to physiological and pathological stimuli. Although the physiological role of Panxs as a hemichannel was questioned, there is increasing evidence that Panx play a role in vasodilatation, initiation of inflammatory responses, ischemic death of neurons, epilepsy and in tumor suppression. Moreover, it is intriguing that Panxs may also function at the endoplasmic reticulum (ER) as intracellular Ca²(+)-leak channel and may be involved in ER-related functions. Although the physiological significance and meaning of such Panx-regulated intracellular Ca²(+) leak requires further exploration, this functional property places Panx at the centre of many physiological and pathophysiological processes, given the fundamental role of intracellular Ca²(+) homeostasis and dynamics in a plethora of physiological processes. In this review, we therefore want to focus on Panx as channels at the plasma membrane and at the ER membranes with a particular emphasis on the potential implications of the latter in intracellular Ca²(+) signalling.
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Simmen T, Lynes EM, Gesson K, Thomas G. Oxidative protein folding in the endoplasmic reticulum: tight links to the mitochondria-associated membrane (MAM). BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:1465-73. [PMID: 20430008 DOI: 10.1016/j.bbamem.2010.04.009] [Citation(s) in RCA: 142] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2010] [Revised: 04/15/2010] [Accepted: 04/16/2010] [Indexed: 12/18/2022]
Abstract
The production of secretory proteins at the ER (endoplasmic reticulum) depends on a ready supply of energy and metabolites as well as the close monitoring of the chemical conditions that favor oxidative protein folding. ER oxidoreductases and chaperones fold nascent proteins into their export-competent three-dimensional structure. Interference with these protein folding enzymes leads to the accumulation of unfolded proteins within the ER lumen, causing an acute organellar stress that triggers the UPR (unfolded protein response). The UPR increases the transcription of ER chaperones commensurate with the load of newly synthesized proteins and can protect the cell from ER stress. Persistant stress, however, can force the UPR to commit cells to undergo apoptotic cell death, which requires the emptying of ER calcium stores. Conversely, a continuous ebb and flow of calcium occurs between the ER and mitochondria during resting conditions on a domain of the ER that forms close contacts with mitochondria, the MAM (mitochondria-associated membrane). On the MAM, ER folding chaperones such as calnexin and calreticulin and oxidoreductases such as ERp44, ERp57 and Ero1alpha regulate calcium flux from the ER through reversible, calcium and redox-dependent interactions with IP3Rs (inositol 1,4,5-trisphophate receptors) and with SERCAs (sarcoplasmic/endoplasmic reticulum calcium ATPases). During apoptosis progression and depending on the identity of the ER chaperone and oxidoreductase, these interactions increase or decrease, suggesting that the extent of MAM targeting of ER chaperones and oxidoreductases could shift the readout of ER-mitochondria calcium exchange from housekeeping to apoptotic. However, little is known about the cytosolic factors that mediate the on/off interactions between ER chaperones and oxidoreductases with ER calcium channels and pumps. One candidate regulator is the multi-functional molecule PACS-2 (phosphofurin acidic cluster sorting protein-2). Recent studies suggest that PACS-2 mediates localization of a mobile pool of calnexin to the MAM in addition to regulating homeostatic ER calcium signaling as well as MAM integrity. Together, these findings suggest that cytosolic, membrane and lumenal proteins combine to form a two-way switch that determines the rate of protein secretion by providing ions and metabolites and that appears to participate in the pro-apoptotic ER-mitochondria calcium transfer.
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Affiliation(s)
- Thomas Simmen
- Faculty of Medicine and Dentistry, School of Molecular and Systems Medicine, Department of Cell Biology, University of Alberta, Edmonton, Alberta, Canada.
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42
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Intracellular Ca2+ storage in health and disease: a dynamic equilibrium. Cell Calcium 2010; 47:297-314. [PMID: 20189643 DOI: 10.1016/j.ceca.2010.02.001] [Citation(s) in RCA: 147] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2009] [Revised: 01/31/2010] [Accepted: 02/01/2010] [Indexed: 12/17/2022]
Abstract
Homeostatic control of the endoplasmic reticulum (ER) both as the site for protein handling (synthesis, folding, trafficking, disaggregation and degradation) and as a Ca2+ store is of crucial importance for correct functioning of the cell. Disturbance of the homeostatic control mechanisms leads to a vast array of severe pathologies. The Ca2+ content of the ER is a dynamic equilibrium between active uptake via Ca2+ pumps and Ca2+ release by a number of highly regulated Ca2+-release channels. Regulation of the Ca2+-release channels is very complex and several mechanisms are still poorly understood or controversial. There is increasing evidence that a number of unrelated proteins, either by themselves or in association with other Ca2+ channels, can provide additional Ca2+-leak pathways. The ER is a dynamic organelle and changes in its size and components have been described, either as a result of (de)differentiation processes affecting the secretory capacity of cells, or as a result of adaptation mechanisms to diverse stress conditions such as the unfolded protein response and autophagy. In this review we want to give an overview of the current knowledge of the (short-term) regulatory mechanisms that affect Ca2+-release and Ca2+-leak pathways and of the (long-term) adaptations in ER size and capacity. Understanding of the consequences of these mechanisms for cellular Ca2+ signaling could provide a huge therapeutic potential.
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Huang CJ, Gurlo T, Haataja L, Costes S, Daval M, Ryazantsev S, Wu X, Butler AE, Butler PC. Calcium-activated calpain-2 is a mediator of beta cell dysfunction and apoptosis in type 2 diabetes. J Biol Chem 2009; 285:339-48. [PMID: 19861418 DOI: 10.1074/jbc.m109.024190] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The islet in type 2 diabetes (T2DM) and the brain in neurodegenerative diseases share progressive cell dysfunction, increased apoptosis, and accumulation of locally expressed amyloidogenic proteins (islet amyloid polypeptide (IAPP) in T2DM). Excessive activation of the Ca(2+)-sensitive protease calpain-2 has been implicated as a mediator of oligomer-induced cell death and dysfunction in neurodegenerative diseases. To establish if human IAPP toxicity is mediated by a comparable mechanism, we overexpressed human IAPP in rat insulinoma cells and freshly isolated human islets. Pancreas was also obtained at autopsy from humans with T2DM and nondiabetic controls. We report that overexpression of human IAPP leads to the formation of toxic oligomers and increases beta cell apoptosis mediated by increased cytosolic Ca(2+) and hyperactivation of calpain-2. Cleavage of alpha-spectrin, a marker of calpain hyperactivation, is increased in beta cells in T2DM. We conclude that overactivation of Ca(2+)-calpain pathways contributes to beta cell dysfunction and apoptosis in T2DM.
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Affiliation(s)
- Chang-jiang Huang
- Larry Hillblom Islet Research Center, David Geffen School of Medicine, California Nano Systems Institute, UCLA, Los Angeles, California 90024-2852, USA
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44
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High endoplasmic reticulum activity renders multiple myeloma cells hypersensitive to mitochondrial inhibitors. Cancer Chemother Pharmacol 2009; 66:129-40. [PMID: 19779717 DOI: 10.1007/s00280-009-1143-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2009] [Accepted: 09/12/2009] [Indexed: 10/20/2022]
Abstract
Multiple myeloma (MM) cells continuously secrete large amounts of immunoglobulins that are folded in the endoplasmic reticulum (ER) whose function depend on the Ca(2+) concentration inside its lumen. Recently, it was shown that the ER membrane leaks Ca(2+) that is captured and delivered back by mitochondria in order to prevent its loss. Thus, we hypothesized that the highly active and abundant ER in MM cells results in greater Ca(2+)-regulation by mitochondria which would render them sensitive to mitochondrial inhibitors. Here, we indeed find that Ca(2+) leak is greater in 3 MM, when compared to 2 B-cell leukemia cell lines. Moreover, this greater leak in MM cells is associated with hypersensitivity to various mitochondrial inhibitors, including CCCP. Consistent with our hypothesis, CCCP is more potent in inducing the unfolded protein response marker, CHOP/GADD153 in MM versus B-cell leukemia lines. Additionally, MM cells are found to be significantly more sensitive to clinically used fenofibrate and troglitazone, both of which were recently shown to have inhibitory effects on mitochondrial function. Overall, our results demonstrate that the unusually high ER activity in MM cells may be exploited for therapeutic benefit through the use of mitochondrial inhibitors including troglitazone and fenofibrate.
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45
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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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46
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Savineau JP. Is the translocon a crucial player of the calcium homeostasis in vascular smooth muscle cell? Am J Physiol Heart Circ Physiol 2009; 296:H906-7. [DOI: 10.1152/ajpheart.00177.2009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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47
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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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48
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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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