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Kamada Y, Ohnishi Y, Nakashima C, Fujii A, Terakawa M, Hamano I, Nakayamada U, Katoh S, Hirata N, Tateishi H, Fukuda R, Takahashi H, Lukacs GL, Okiyoneda T. HERC3 facilitates ERAD of select membrane proteins by recognizing membrane-spanning domains. J Cell Biol 2024; 223:e202308003. [PMID: 38722278 PMCID: PMC11082371 DOI: 10.1083/jcb.202308003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 02/22/2024] [Accepted: 03/18/2024] [Indexed: 05/12/2024] Open
Abstract
Aberrant proteins located in the endoplasmic reticulum (ER) undergo rapid ubiquitination by multiple ubiquitin (Ub) E3 ligases and are retrotranslocated to the cytosol as part of the ER-associated degradation (ERAD). Despite several ERAD branches involving different Ub E3 ligases, the molecular machinery responsible for these ERAD branches in mammalian cells remains not fully understood. Through a series of multiplex knockdown/knockout experiments with real-time kinetic measurements, we demonstrate that HERC3 operates independently of the ER-embedded ubiquitin ligases RNF5 and RNF185 (RNF5/185) to mediate the retrotranslocation and ERAD of misfolded CFTR. While RNF5/185 participates in the ERAD process of both misfolded ABCB1 and CFTR, HERC3 uniquely promotes CFTR ERAD. In vitro assay revealed that HERC3 directly interacts with the exposed membrane-spanning domains (MSDs) of CFTR but not with the MSDs embedded in liposomes. Therefore, HERC3 could play a role in the quality control of MSDs in the cytoplasm and might be crucial for the ERAD pathway of select membrane proteins.
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Affiliation(s)
- Yuka Kamada
- Department of Biomedical Sciences, School of Biological and Environmental Sciences, Kwansei Gakuin University, Sanda, Japan
| | - Yuko Ohnishi
- Department of Biomedical Sciences, School of Biological and Environmental Sciences, Kwansei Gakuin University, Sanda, Japan
| | - Chikako Nakashima
- Department of Biomedical Sciences, School of Biological and Environmental Sciences, Kwansei Gakuin University, Sanda, Japan
| | - Aika Fujii
- Department of Biomedical Sciences, School of Biological and Environmental Sciences, Kwansei Gakuin University, Sanda, Japan
| | - Mana Terakawa
- Department of Biomedical Sciences, School of Biological and Environmental Sciences, Kwansei Gakuin University, Sanda, Japan
| | - Ikuto Hamano
- Department of Biomedical Sciences, School of Biological and Environmental Sciences, Kwansei Gakuin University, Sanda, Japan
| | - Uta Nakayamada
- Department of Biomedical Sciences, School of Biological and Environmental Sciences, Kwansei Gakuin University, Sanda, Japan
| | - Saori Katoh
- Department of Biomedical Sciences, School of Biological and Environmental Sciences, Kwansei Gakuin University, Sanda, Japan
| | - Noriaki Hirata
- Department of Biomedical Sciences, School of Biological and Environmental Sciences, Kwansei Gakuin University, Sanda, Japan
| | - Hazuki Tateishi
- Department of Biomedical Sciences, School of Biological and Environmental Sciences, Kwansei Gakuin University, Sanda, Japan
| | - Ryosuke Fukuda
- Department of Biomedical Sciences, School of Biological and Environmental Sciences, Kwansei Gakuin University, Sanda, Japan
| | - Hirotaka Takahashi
- Division of Cell-Free Sciences, Proteo-Science Center (PROS), Ehime University, Matsuyama, Japan
| | - Gergely L. Lukacs
- Department of Physiology, McGill University, Montréal, Canada
- Department of Biochemistry, McGill University, Montréal, Canada
| | - Tsukasa Okiyoneda
- Department of Biomedical Sciences, School of Biological and Environmental Sciences, Kwansei Gakuin University, Sanda, Japan
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2
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Abdon B, Liang Y, da Luz Scheffer D, Torres M, Shrestha N, Reinert RB, Lu Y, Pederson B, Bugarin-Lapuz A, Kersten S, Qi L. Muscle-specific ER-associated degradation maintains postnatal muscle hypertrophy and systemic energy metabolism. JCI Insight 2023; 8:e170387. [PMID: 37535424 PMCID: PMC10578429 DOI: 10.1172/jci.insight.170387] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Accepted: 07/27/2023] [Indexed: 08/05/2023] Open
Abstract
The growth of skeletal muscle relies on a delicate equilibrium between protein synthesis and degradation; however, how proteostasis is managed in the endoplasmic reticulum (ER) is largely unknown. Here, we report that the SEL1L-HRD1 ER-associated degradation (ERAD) complex, the primary molecular machinery that degrades misfolded proteins in the ER, is vital to maintain postnatal muscle growth and systemic energy balance. Myocyte-specific SEL1L deletion blunts the hypertrophic phase of muscle growth, resulting in a net zero gain of muscle mass during this developmental period and a 30% reduction in overall body growth. In addition, myocyte-specific SEL1L deletion triggered a systemic reprogramming of metabolism characterized by improved glucose sensitivity, enhanced beigeing of adipocytes, and resistance to diet-induced obesity. These effects were partially mediated by the upregulation of the myokine FGF21. These findings highlight the pivotal role of SEL1L-HRD1 ERAD activity in skeletal myocytes for postnatal muscle growth, and its physiological integration in maintaining whole-body energy balance.
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Affiliation(s)
- Benedict Abdon
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Yusheng Liang
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Débora da Luz Scheffer
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA
- Department of Anatomy, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil
| | - Mauricio Torres
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Neha Shrestha
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Rachel B. Reinert
- Division of Metabolism, Endocrinology & Diabetes, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - You Lu
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Brent Pederson
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Amara Bugarin-Lapuz
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Sander Kersten
- Nutrition Metabolism and Genomics group, Wageningen University, Wageningen, Netherlands
| | - Ling Qi
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA
- Division of Metabolism, Endocrinology & Diabetes, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan, USA
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan, USA
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3
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Wang J, Han S, Ye J. Topological regulation of a transmembrane protein by luminal-to-cytosolic retrotranslocation of glycosylated sequence. Cell Rep 2023; 42:112311. [PMID: 36972171 PMCID: PMC10520219 DOI: 10.1016/j.celrep.2023.112311] [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: 10/03/2022] [Revised: 02/02/2023] [Accepted: 03/11/2023] [Indexed: 03/28/2023] Open
Abstract
Transmembrane proteins must adopt proper topology to perform their functions. We previously demonstrated that ceramide regulates TM4SF20 (transmembrane 4 L6 family 20) by altering the topology of the transmembrane protein, but the underlying mechanism remains obscure. Here we report that TM4SF20 is synthesized in the endoplasmic reticulum (ER) with a cytosolic C terminus and a luminal loop before the last transmembrane helix where N132, N148, and N163 are glycosylated. In the absence of ceramide, the sequence surrounding glycosylated N163 but not N132 is retrotranslocated from lumen to cytosol independent of ER-associated degradation. Accompanying this retrotranslocation, the C terminus of the protein is relocated from cytosol to lumen. Ceramide delays the retrotranslocation process, causing accumulation of the protein that is originally synthesized. Our findings suggest that N-linked glycans, although synthesized in the lumens, may be exposed to cytosol through retrotranslocation, a reaction that may play a crucial role in topological regulation of transmembrane proteins.
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Affiliation(s)
- Jingcheng Wang
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Sungwon Han
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Jin Ye
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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4
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Bhaduri S, Aguayo A, Ohno Y, Proietto M, Jung J, Wang I, Kandel R, Singh N, Ibrahim I, Fulzele A, Bennett EJ, Kihara A, Neal SE. An ERAD-independent role for rhomboid pseudoprotease Dfm1 in mediating sphingolipid homeostasis. EMBO J 2023; 42:e112275. [PMID: 36350249 PMCID: PMC9929635 DOI: 10.15252/embj.2022112275] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 09/20/2022] [Accepted: 10/19/2022] [Indexed: 11/11/2022] Open
Abstract
Nearly one-third of nascent proteins are initially targeted to the endoplasmic reticulum (ER), where they are correctly folded and assembled before being delivered to their final cellular destinations. To prevent the accumulation of misfolded membrane proteins, ER-associated degradation (ERAD) removes these client proteins from the ER membrane to the cytosol in a process known as retrotranslocation. Our previous work demonstrated that rhomboid pseudoprotease Dfm1 is involved in the retrotranslocation of ubiquitinated membrane integral ERAD substrates. Herein, we found that Dfm1 associates with the SPOTS complex, which is composed of serine palmitoyltransferase (SPT) enzymes and accessory components that are critical for catalyzing the first rate-limiting step of the sphingolipid biosynthesis pathway. Furthermore, Dfm1 employs an ERAD-independent role for facilitating the ER export and endosome- and Golgi-associated degradation (EGAD) of Orm2, which is a major antagonist of SPT activity. Given that the accumulation of human Orm2 homologs, ORMDLs, is associated with various pathologies, our study serves as a molecular foothold for understanding how dysregulation of sphingolipid metabolism leads to various diseases.
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Affiliation(s)
- Satarupa Bhaduri
- Department of Cell and Developmental Biology, School of Biological SciencesUniversity of California San DiegoLa JollaCAUSA
| | - Analine Aguayo
- Department of Cell and Developmental Biology, School of Biological SciencesUniversity of California San DiegoLa JollaCAUSA
| | - Yusuke Ohno
- Laboratory of Biochemistry, Faculty of Pharmaceutical SciencesHokkaido UniversitySapporoJapan
| | - Marco Proietto
- Department of Cell and Developmental Biology, School of Biological SciencesUniversity of California San DiegoLa JollaCAUSA
| | - Jasmine Jung
- Department of Cell and Developmental Biology, School of Biological SciencesUniversity of California San DiegoLa JollaCAUSA
| | - Isabel Wang
- Department of Cell and Developmental Biology, School of Biological SciencesUniversity of California San DiegoLa JollaCAUSA
| | - Rachel Kandel
- Department of Cell and Developmental Biology, School of Biological SciencesUniversity of California San DiegoLa JollaCAUSA
| | - Narinderbir Singh
- Department of Cell and Developmental Biology, School of Biological SciencesUniversity of California San DiegoLa JollaCAUSA
| | - Ikran Ibrahim
- Department of Cell and Developmental Biology, School of Biological SciencesUniversity of California San DiegoLa JollaCAUSA
| | - Amit Fulzele
- Present address:
Institute of Molecular BiologyMainzGermany
| | - Eric J Bennett
- Department of Cell and Developmental Biology, School of Biological SciencesUniversity of California San DiegoLa JollaCAUSA
| | - Akio Kihara
- Laboratory of Biochemistry, Faculty of Pharmaceutical SciencesHokkaido UniversitySapporoJapan
| | - Sonya E Neal
- Department of Cell and Developmental Biology, School of Biological SciencesUniversity of California San DiegoLa JollaCAUSA
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5
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Bhaduri S, Scott NA, Neal SE. The Role of the Rhomboid Superfamily in ER Protein Quality Control: From Mechanisms and Functions to Diseases. Cold Spring Harb Perspect Biol 2023; 15:a041248. [PMID: 35940905 PMCID: PMC9899648 DOI: 10.1101/cshperspect.a041248] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The endoplasmic reticulum (ER) is an essential organelle in eukaryotic cells and is a major site for protein folding, modification, and lipid synthesis. Perturbations within the ER, such as protein misfolding and high demand for protein folding, lead to dysregulation of the ER protein quality control network and ER stress. Recently, the rhomboid superfamily has emerged as a critical player in ER protein quality control because it has diverse cellular functions, including ER-associated degradation (ERAD), endosome Golgi-associated degradation (EGAD), and ER preemptive quality control (ERpQC). This breadth of function both illustrates the importance of the rhomboid superfamily in health and diseases and emphasizes the necessity of understanding their mechanisms of action. Because dysregulation of rhomboid proteins has been implicated in various diseases, such as neurological disorders and cancers, they represent promising potential therapeutic drug targets. This review provides a comprehensive account of the various roles of rhomboid proteins in the context of ER protein quality control and discusses their significance in health and disease.
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Affiliation(s)
- Satarupa Bhaduri
- School of Biological Sciences, the Section of Cell and Developmental Biology, University of California San Diego, La Jolla, California 92093, USA
| | - Nicola A Scott
- School of Biological Sciences, the Section of Cell and Developmental Biology, University of California San Diego, La Jolla, California 92093, USA
| | - Sonya E Neal
- School of Biological Sciences, the Section of Cell and Developmental Biology, University of California San Diego, La Jolla, California 92093, USA
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6
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The Proteostasis Network: A Global Therapeutic Target for Neuroprotection after Spinal Cord Injury. Cells 2022; 11:cells11213339. [PMID: 36359735 PMCID: PMC9658791 DOI: 10.3390/cells11213339] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Revised: 10/14/2022] [Accepted: 10/20/2022] [Indexed: 01/18/2023] Open
Abstract
Proteostasis (protein homeostasis) is critical for cellular as well as organismal survival. It is strictly regulated by multiple conserved pathways including the ubiquitin-proteasome system, autophagy, the heat shock response, the integrated stress response, and the unfolded protein response. These overlapping proteostasis maintenance modules respond to various forms of cellular stress as well as organismal injury. While proteostasis restoration and ultimately organism survival is the main evolutionary driver of such a regulation, unresolved disruption of proteostasis may engage pro-apoptotic mediators of those pathways to eliminate defective cells. In this review, we discuss proteostasis contributions to the pathogenesis of traumatic spinal cord injury (SCI). Most published reports focused on the role of proteostasis networks in acute/sub-acute tissue damage post-SCI. Those reports reveal a complex picture with cell type- and/or proteostasis mediator-specific effects on loss of neurons and/or glia that often translate into the corresponding modulation of functional recovery. Effects of proteostasis networks on such phenomena as neuro-repair, post-injury plasticity, as well as systemic manifestations of SCI including dysregulation of the immune system, metabolism or cardiovascular function are currently understudied. However, as potential interventions that target the proteostasis networks are expected to impact many cell types across multiple organ systems that are compromised after SCI, such therapies could produce beneficial effects across the wide spectrum of highly variable human SCI.
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7
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Pisa R, Rapoport TA. Disulfide-crosslink analysis of the ubiquitin ligase Hrd1 complex during endoplasmic reticulum-associated protein degradation. J Biol Chem 2022; 298:102373. [PMID: 35970394 PMCID: PMC9478403 DOI: 10.1016/j.jbc.2022.102373] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Revised: 08/04/2022] [Accepted: 08/05/2022] [Indexed: 11/25/2022] Open
Abstract
Misfolded proteins in the lumen of the endoplasmic reticulum (ER) are retrotranslocated into the cytosol and degraded by the ubiquitin-proteasome system, a pathway termed luminal ER-associated protein degradation. Retrotranslocation is mediated by a conserved protein complex, consisting of the ubiquitin ligase Hrd1 and four associated proteins (Der1, Usa1, Hrd3, and Yos9). Photocrosslinking experiments provided preliminary evidence for the polypeptide path through the membrane but did not reveal specific interactions between amino acids in the substrate and Hrd1 complex. Here, we have used site-specific disulfide crosslinking to map the interactions of a glycosylated model substrate with the Hrd1 complex in live S. cerevisiae cells. Together with available electron cryo-microscopy structures, the results show that the substrate interacts on the luminal side with both a groove in Hrd3 and the lectin domain of Yos9 and inserts a loop into the membrane, with one side of the loop interacting with the lateral gate of Der1 and the other with the lateral gate of Hrd1. Our disulfide crosslinking experiments also show that two Hrd1 molecules can interact through their lateral gates and that Hrd1 autoubiquitination is required for the disassembly of these Hrd1 dimers. Taken together, these data define the path of a polypeptide through the ER membrane and suggest that autoubiquitination of inactive Hrd1 dimers is required to generate active Hrd1 monomers.
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Affiliation(s)
- Rudolf Pisa
- Howard Hughes Medical Institute and Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA
| | - Tom A Rapoport
- Howard Hughes Medical Institute and Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA.
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8
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Guo T, Weber H, Niemann MCE, Theisl L, Leonte G, Novák O, Werner T. Arabidopsis HIPP proteins regulate endoplasmic reticulum-associated degradation of CKX proteins and cytokinin responses. MOLECULAR PLANT 2021; 14:1918-1934. [PMID: 34314894 DOI: 10.1016/j.molp.2021.07.015] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Revised: 05/18/2021] [Accepted: 07/21/2021] [Indexed: 06/13/2023]
Abstract
Eukaryotic organisms are equipped with quality-control mechanisms that survey protein folding in the endoplasmic reticulum (ER) and remove non-native proteins by ER-associated degradation (ERAD). Recent research has shown that cytokinin-degrading CKX proteins are subjected to ERAD during plant development. The mechanisms of plant ERAD, including the export of substrate proteins from the ER, are not fully understood, and the molecular components involved in the ERAD of CKX are unknown. Here, we show that heavy metal-associated isoprenylated plant proteins (HIPPs) interact specifically with CKX proteins synthesized in the ER and processed by ERAD. CKX-HIPP protein complexes were detected at the ER as well as in the cytosol, suggesting that the complexes involve retrotranslocated CKX protein species. Altered CKX levels in HIPP-overexpressing and higher-order hipp mutant plants suggest that the studied HIPPs control the ERAD of CKX. Deregulation of CKX proteins caused corresponding changes in the cytokinin signaling activity and triggered typical morphological cytokinin responses. Notably, transcriptional repression of HIPP genes by cytokinin indicates a feedback regulatory mechanism of cytokinin homeostasis and signaling responses. Moreover, loss of function of HIPP genes constitutively activates the unfolded protein response and compromises the ER stress tolerance. Collectively, these results suggests that HIPPs represent novel functional components of plant ERAD.
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Affiliation(s)
- Tianqi Guo
- Institute of Biology/Applied Genetics, Dahlem Centre of Plant Sciences (DCPS), Freie Universität Berlin, Albrecht-Thaer-Weg 6, 14195 Berlin, Germany; Guangdong Provincial Key Laboratory of Conservation and Precision Utilization of Characteristic Agricultural Resources in Mountainous Areas, School of Life Science of Jiaying University, 514015 Mei Zhou, China
| | - Henriette Weber
- Institute of Biology/Applied Genetics, Dahlem Centre of Plant Sciences (DCPS), Freie Universität Berlin, Albrecht-Thaer-Weg 6, 14195 Berlin, Germany
| | - Michael C E Niemann
- Institute of Biology/Applied Genetics, Dahlem Centre of Plant Sciences (DCPS), Freie Universität Berlin, Albrecht-Thaer-Weg 6, 14195 Berlin, Germany
| | - Lisa Theisl
- Institute of Biology, University of Graz, Schubertstraße 51, 8010 Graz, Austria
| | - Georgeta Leonte
- Institute of Biology/Applied Genetics, Dahlem Centre of Plant Sciences (DCPS), Freie Universität Berlin, Albrecht-Thaer-Weg 6, 14195 Berlin, Germany
| | - Ondřej Novák
- Laboratory of Growth Regulators, Centre of the Region Haná for Biotechnological and Agricultural Research, Palacký University and Institute of Experimental Botany ASCR, 78371 Olomouc, Czech Republic
| | - Tomáš Werner
- Institute of Biology, University of Graz, Schubertstraße 51, 8010 Graz, Austria.
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9
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Oh H, Kang MK, Park SH, Kim DY, Kim SI, Oh SY, Na W, Shim JH, Lim SS, Kang YH. Asaronic acid inhibits ER stress sensors and boosts functionality of ubiquitin-proteasomal degradation in 7β-hydroxycholesterol-loaded macrophages. PHYTOMEDICINE : INTERNATIONAL JOURNAL OF PHYTOTHERAPY AND PHYTOPHARMACOLOGY 2021; 92:153763. [PMID: 34601222 DOI: 10.1016/j.phymed.2021.153763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Revised: 09/08/2021] [Accepted: 09/14/2021] [Indexed: 06/13/2023]
Abstract
BACKGROUND Misfolded proteins are formed in the endoplasmic reticulum (ER) due to diverse stimuli including oxidant production, calcium disturbance, and inflammatory factors. Accumulation of these non-native proteins in the ER evokes cellular stress involving the activation of unfolded protein response (UPR) and the execution of ER-associated degradation (ERAD). Naturally-occurring plant compounds are known to interfere with UPR due to their antioxidant and anti-inflammatory activities, leading to inhibition of ER stress. However, there are few studies dealing with the protective effects of natural compounds on the functionality of ERAD. PURPOSE The current study examined whether asaronic acid enhanced ubiquitin-proteasomal degradation in J774A.1 murine macrophages exposed to 7β-hydroxycholesterol, a risk factor for atherosclerosis. Asaronic acid (2,4,5-trimethoxybenzoic acid), identified as one of purple perilla constituents, has anti-diabetic and anti-inflammatory effects. Little is known regarding the effects of asaronic acid on the ERAD process and the ubiquitin-proteasomal degradation. METHODS AND RESULTS Murine macrophages were incubated with 28 μM 7β-hydroxycholesterol in absence and presence of 1-20 μΜ asaronic acid for up to 24 h. Nontoxic asaronic acid in macrophage diminished the activation of the ER stress sensors of ATF6, IRE1 and PERK stimulated by 7β-hydroxycholesterol. This methoxybenzoic acid down-regulated the oxysterol-induced expression of EDEM1, OS9, Sel1L-Hrd1 and p97/VCP1, all required for the recognition, recruitment and dislocation of misfolded proteins. On the other hand, asaronic acid enhanced the ubiquitin-proteasomal degradation of non-native proteins dislocated to the cytosol by 7β-hydroxycholesterol, which entailed the induction of the chaperones of Hsp70 and CHIP and the increased colocalization of ubiquitin and proteasomes. Taken together, asaronic acid attenuated the induction of the UPR-associated sensors and the dislocation-linked transmembrane components in the ER. Conversely, this compound enhanced the proteasomal degradation of dislocated non-native proteins in concert with the chaperones of Hsp70 and CHIP through ubiquitination. CONCLUSION These observations demonstrate that asaronic acid may be a potent atheroprotective agent as a natural chaperone targeting ER stress-associated macrophage injury.
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Affiliation(s)
- Hyeongjoo Oh
- Department of Food Science and Nutrition and The Korean Institute of Nutrition, Hallym University, Chuncheon, Kangwon-do 24252, Korea
| | - Min-Kyung Kang
- Department of Food Science and Nutrition and The Korean Institute of Nutrition, Hallym University, Chuncheon, Kangwon-do 24252, Korea
| | - Sin-Hye Park
- Department of Food Science and Nutrition and The Korean Institute of Nutrition, Hallym University, Chuncheon, Kangwon-do 24252, Korea
| | - Dong Yeon Kim
- Department of Food Science and Nutrition and The Korean Institute of Nutrition, Hallym University, Chuncheon, Kangwon-do 24252, Korea
| | - Soo-Il Kim
- Department of Food Science and Nutrition and The Korean Institute of Nutrition, Hallym University, Chuncheon, Kangwon-do 24252, Korea
| | - Su Yeon Oh
- Department of Food Science and Nutrition and The Korean Institute of Nutrition, Hallym University, Chuncheon, Kangwon-do 24252, Korea
| | - Woojin Na
- Department of Food Science and Nutrition and The Korean Institute of Nutrition, Hallym University, Chuncheon, Kangwon-do 24252, Korea
| | - Jae-Hoon Shim
- Department of Food Science and Nutrition and The Korean Institute of Nutrition, Hallym University, Chuncheon, Kangwon-do 24252, Korea
| | - Soon Sung Lim
- Department of Food Science and Nutrition and The Korean Institute of Nutrition, Hallym University, Chuncheon, Kangwon-do 24252, Korea
| | - Young-Hee Kang
- Department of Food Science and Nutrition and The Korean Institute of Nutrition, Hallym University, Chuncheon, Kangwon-do 24252, Korea.
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10
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Gao J, Gao A, Liu W, Chen L. Golgi stress response: A regulatory mechanism of Golgi function. Biofactors 2021; 47:964-974. [PMID: 34500494 DOI: 10.1002/biof.1780] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Accepted: 08/25/2021] [Indexed: 01/09/2023]
Abstract
The organelle of eukaryotes is a finely regulated system. Once disturbed, it activates the specific autoregulatory systems, namely, organelle autoregulation. Among which, the Golgi stress response accounts for one. When the abundance and capacity of the Golgi apparatus are insufficient compared with cellular demand, the Golgi stress response is activated to enhance the function of the Golgi apparatus. Although the molecular mechanism of the Golgi stress response has not been well characterized yet, it seems to be an important part of the mammalian stress response. In this review, we discuss the current status of research on the six pathways of the mammalian Golgi stress response (the TFE3, heat shock protein 47, CREB3, E26 transformation specific, proteoglycan, and mucin pathways), which regulate the general function of the Golgi apparatus, anti-apoptosis, pro-apoptosis, proteoglycan glycosylation, and mucin glycosylation, respectively.
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Affiliation(s)
- Jiayin Gao
- Institute of Pharmacy and Pharmacology, Learning Key Laboratory for Pharmacoproteomics, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, University of South China, Hengyang, China
| | - Anbo Gao
- Institute of Pharmacy and Pharmacology, Learning Key Laboratory for Pharmacoproteomics, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, University of South China, Hengyang, China
| | - Wei Liu
- Department of Pharmacy, The Third Xiangya Hospital, Central South University, Changsha, China
| | - Linxi Chen
- Institute of Pharmacy and Pharmacology, Learning Key Laboratory for Pharmacoproteomics, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, University of South China, Hengyang, China
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11
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Nejatfard A, Wauer N, Bhaduri S, Conn A, Gourkanti S, Singh N, Kuo T, Kandel R, Amaro RE, Neal SE. Derlin rhomboid pseudoproteases employ substrate engagement and lipid distortion to enable the retrotranslocation of ERAD membrane substrates. Cell Rep 2021; 37:109840. [PMID: 34686332 PMCID: PMC8641752 DOI: 10.1016/j.celrep.2021.109840] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Revised: 07/19/2021] [Accepted: 09/27/2021] [Indexed: 01/13/2023] Open
Abstract
Nearly one-third of proteins are initially targeted to the endoplasmic reticulum (ER) membrane, where they are correctly folded and then delivered to their final cellular destinations. To prevent the accumulation of misfolded membrane proteins, ER-associated degradation (ERAD) moves these clients from the ER membrane to the cytosol, a process known as retrotranslocation. Our recent work in Saccharomyces cerevisiae reveals a derlin rhomboid pseudoprotease, Dfm1, is involved in the retrotranslocation of ubiquitinated ERAD membrane substrates. In this study, we identify conserved residues of Dfm1 that are critical for retrotranslocation. We find several retrotranslocation-deficient Loop 1 mutants that display impaired binding to membrane substrates. Furthermore, Dfm1 possesses lipid thinning function to facilitate in the removal of ER membrane substrates, and this feature is conserved in its human homolog, Derlin-1, further implicating that derlin-mediated retrotranslocation is a well-conserved process.
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Affiliation(s)
- Anahita Nejatfard
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California San Diego, La Jolla, CA 92093, USA
| | - Nicholas Wauer
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA 92093, USA
| | - Satarupa Bhaduri
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California San Diego, La Jolla, CA 92093, USA
| | - Adam Conn
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California San Diego, La Jolla, CA 92093, USA
| | - Saroj Gourkanti
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California San Diego, La Jolla, CA 92093, USA
| | - Narinderbir Singh
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California San Diego, La Jolla, CA 92093, USA
| | - Tiffany Kuo
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California San Diego, La Jolla, CA 92093, USA
| | - Rachel Kandel
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California San Diego, La Jolla, CA 92093, USA
| | - Rommie E Amaro
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA 92093, USA
| | - Sonya E Neal
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California San Diego, La Jolla, CA 92093, USA.
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12
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van Anken E, Bakunts A, Hu CCA, Janssens S, Sitia R. Molecular Evaluation of Endoplasmic Reticulum Homeostasis Meets Humoral Immunity. Trends Cell Biol 2021; 31:529-541. [PMID: 33685797 DOI: 10.1016/j.tcb.2021.02.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Revised: 02/02/2021] [Accepted: 02/03/2021] [Indexed: 12/16/2022]
Abstract
The biosynthesis of about one third of the human proteome, including membrane receptors and secreted proteins, occurs in the endoplasmic reticulum (ER). Conditions that perturb ER homeostasis activate the unfolded protein response (UPR). An 'optimistic' UPR output aims at restoring homeostasis by reinforcement of machineries that guarantee efficiency and fidelity of protein biogenesis in the ER. Yet, once the UPR 'deems' that ER homeostatic readjustment fails, it transitions to a 'pessimistic' output, which, depending on the cell type, will result in apoptosis. In this article, we discuss emerging concepts on how the UPR 'evaluates' ER stress, how the UPR is repurposed, in particular in B cells, and how UPR-driven counter-selection of cells undergoing homeostatic failure serves organismal homeostasis and humoral immunity.
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Affiliation(s)
- Eelco van Anken
- Division of Genetics and Cell Biology, San Raffaele Scientific Institute, Milan, Italy; Vita-Salute San Raffaele University, Milan, Italy.
| | - Anush Bakunts
- Division of Genetics and Cell Biology, San Raffaele Scientific Institute, Milan, Italy
| | | | - Sophie Janssens
- Laboratory for Endoplasmic Reticulum (ER) Stress and Inflammation, VIB Center for Inflammation Research, and Department of Internal Medicine and Pediatrics, Ghent University, Ghent, Belgium
| | - Roberto Sitia
- Division of Genetics and Cell Biology, San Raffaele Scientific Institute, Milan, Italy; Vita-Salute San Raffaele University, Milan, Italy
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13
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Kang JA, Jeon YJ. How Is the Fidelity of Proteins Ensured in Terms of Both Quality and Quantity at the Endoplasmic Reticulum? Mechanistic Insights into E3 Ubiquitin Ligases. Int J Mol Sci 2021; 22:ijms22042078. [PMID: 33669844 PMCID: PMC7923238 DOI: 10.3390/ijms22042078] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 02/16/2021] [Accepted: 02/16/2021] [Indexed: 02/06/2023] Open
Abstract
The endoplasmic reticulum (ER) is an interconnected organelle that plays fundamental roles in the biosynthesis, folding, stabilization, maturation, and trafficking of secretory and transmembrane proteins. It is the largest organelle and critically modulates nearly all aspects of life. Therefore, in the endoplasmic reticulum, an enormous investment of resources, including chaperones and protein folding facilitators, is dedicated to adequate protein maturation and delivery to final destinations. Unfortunately, the folding and assembly of proteins can be quite error-prone, which leads to the generation of misfolded proteins. Notably, protein homeostasis, referred to as proteostasis, is constantly exposed to danger by flows of misfolded proteins and subsequent protein aggregates. To maintain proteostasis, the ER triages and eliminates terminally misfolded proteins by delivering substrates to the ubiquitin–proteasome system (UPS) or to the lysosome, which is termed ER-associated degradation (ERAD) or ER-phagy, respectively. ERAD not only eliminates misfolded or unassembled proteins via protein quality control but also fine-tunes correctly folded proteins via protein quantity control. Intriguingly, the diversity and distinctive nature of E3 ubiquitin ligases determine efficiency, complexity, and specificity of ubiquitination during ERAD. ER-phagy utilizes the core autophagy machinery and eliminates ERAD-resistant misfolded proteins. Here, we conceptually outline not only ubiquitination machinery but also catalytic mechanisms of E3 ubiquitin ligases. Further, we discuss the mechanistic insights into E3 ubiquitin ligases involved in the two guardian pathways in the ER, ERAD and ER-phagy. Finally, we provide the molecular mechanisms by which ERAD and ER-phagy conduct not only protein quality control but also protein quantity control to ensure proteostasis and subsequent organismal homeostasis.
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Affiliation(s)
- Ji An Kang
- Department of Biochemistry, College of Medicine, Chungnam National University, Daejeon 35015, Korea;
- Department of Medical Science, College of Medicine, Chungnam National University, Daejeon 35015, Korea
| | - Young Joo Jeon
- Department of Biochemistry, College of Medicine, Chungnam National University, Daejeon 35015, Korea;
- Department of Medical Science, College of Medicine, Chungnam National University, Daejeon 35015, Korea
- Correspondence:
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14
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Kandel RR, Neal SE. The role of rhomboid superfamily members in protein homeostasis: Mechanistic insight and physiological implications. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2020; 1867:118793. [PMID: 32645330 PMCID: PMC7434706 DOI: 10.1016/j.bbamcr.2020.118793] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Revised: 05/30/2020] [Accepted: 07/01/2020] [Indexed: 12/11/2022]
Abstract
Cells are equipped with protein quality control pathways in order to maintain a healthy proteome; a process known as protein homeostasis. Dysfunction in protein homeostasis leads to the development of many diseases that are associated with proteinopathies. Recently, the rhomboid superfamily has attracted much attention concerning their involvement in protein homeostasis. While their functional role has become much clearer in the last few years, their systemic significance in mammals remains elusive. Here we delineate the current knowledge of rhomboids in protein quality control and how these functions are integrated at the organismal level.
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Affiliation(s)
- Rachel R Kandel
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California San Diego, La Jolla, CA 92093, United States of America
| | - Sonya E Neal
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California San Diego, La Jolla, CA 92093, United States of America.
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15
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Singh A, Vashistha N, Heck J, Tang X, Wipf P, Brodsky JL, Hampton RY. Direct involvement of Hsp70 ATP hydrolysis in Ubr1-dependent quality control. Mol Biol Cell 2020; 31:2669-2686. [PMID: 32966159 PMCID: PMC7927186 DOI: 10.1091/mbc.e20-08-0541] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Chaperones can mediate both protein folding and degradation. This process is referred to as protein triage, which demands study to reveal mechanisms of quality control for both basic scientific and translational purposes. In yeast, many misfolded proteins undergo chaperone-dependent ubiquitination by the action of the E3 ligases Ubr1 and San1, allowing detailed study of protein triage. In cells, both HSP70 and HSP90 mediated substrate ubiquitination, and the canonical ATP cycle was required for HSP70’s role: we have found that ATP hydrolysis by HSP70, the nucleotide exchange activity of Sse1, and the action of J-proteins are all needed for Ubr1-mediated quality control. To discern whether chaperones were directly involved in Ubr1-mediated ubiquitination, we developed a bead-based assay with covalently immobilized but releasable misfolded protein to obviate possible chaperone effects on substrate physical state or transport. In this in vitro assay, only HSP70 was required, along with its ATPase cycle and relevant cochaperones, for Ubr1-mediated ubiquitination. The requirement for the HSP70 ATP cycle in ubiquitination suggests a possible model of triage in which efficiently folded proteins are spared, while slow-folding or nonfolding proteins are iteratively tagged with ubiquitin for subsequent degradation.
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Affiliation(s)
- Amanjot Singh
- Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92103
| | - Nidhi Vashistha
- Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92103
| | - Jarrod Heck
- Adaptive Biotechnologies Corp., Seattle, WA 98102
| | - Xin Tang
- Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92103
| | - Peter Wipf
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260
| | - Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
| | - Randolph Y Hampton
- Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92103
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16
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Niwa M. A cell cycle checkpoint for the endoplasmic reticulum. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2020; 1867:118825. [PMID: 32828757 DOI: 10.1016/j.bbamcr.2020.118825] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2020] [Revised: 08/10/2020] [Accepted: 08/12/2020] [Indexed: 02/07/2023]
Abstract
The generation of new cells is one of the most fundamental aspects of cell biology. Proper regulation of the cell cycle is critical for human health, as underscored by many diseases associated with errors in cell cycle regulation, including both cancer and hereditary diseases. A large body of work has identified regulatory mechanisms and checkpoints that ensure accurate and timely replication and segregation of chromosomal DNA. However, few studies have evaluated the extent to which similar checkpoints exist for the division of cytoplasmic components, including organelles. Such checkpoint mechanisms might be crucial for compartments that cannot be generated de novo, such as the endoplasmic reticulum (ER). In this review, we highlight recent work in the model organism Saccharomyces cerevisiae that led to the discovery of such a checkpoint that ensures that cells inherit functional ER into the daughter cell.
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Affiliation(s)
- Maho Niwa
- Division of Biological Sciences, Section of Molecular Biology, University of California San Diego, NSB#1, Rm 5328, 9500 Gilman Drive, La Jolla, CA 92093-0377, United States of America.
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17
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Neal S, Syau D, Nejatfard A, Nadeau S, Hampton RY. HRD Complex Self-Remodeling Enables a Novel Route of Membrane Protein Retrotranslocation. iScience 2020; 23:101493. [PMID: 32891886 PMCID: PMC7481253 DOI: 10.1016/j.isci.2020.101493] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Revised: 07/09/2020] [Accepted: 08/19/2020] [Indexed: 12/17/2022] Open
Abstract
ER-associated degradation (ERAD) targets misfolded ER proteins for degradation. Retrotranslocation, a key feature of ERAD, entails removal of ubiquitinated substrates into the cytosol for proteasomal destruction. Recently, it has been shown that the Hrd1 E3 ligase forms a retrotranslocation channel for luminal (ERAD-L) substrates. Conversely, our studies found that integral membrane (ERAD-M) substrates exit the ER through a distinct pathway mediated by the Dfm1 rhomboid protein. Those studies also revealed a second, Hrd1-dependent pathway of ERAD-M retrotranslocation can arise in dfm1Δ null. Here we show that, in the dfm1Δ null, the HRD complex undergoes remodeling to a form that mediates ERAD-M retrotranslocation. Specifically, Hrd1's normally present stochiometric partner Hrd3 is efficiently removed during suppressive remodeling, allowing Hrd1 to function in this novel capacity. Neither Hrd1 autoubiquitination nor its cytosolic domain is required for suppressive ERAD-M retrotranslocation. Thus, the HRD complex displays remarkable functional flexibility in response to ER stress.
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Affiliation(s)
- Sonya Neal
- Division of Biological Sciences, the Section of Cell and Developmental Biology, University of California San Diego, La Jolla, CA 92093, USA.
| | - Della Syau
- Division of Biological Sciences, the Section of Cell and Developmental Biology, University of California San Diego, La Jolla, CA 92093, USA
| | - Anahita Nejatfard
- Division of Biological Sciences, the Section of Cell and Developmental Biology, University of California San Diego, La Jolla, CA 92093, USA
| | - Samantha Nadeau
- Division of Biological Sciences, the Section of Cell and Developmental Biology, University of California San Diego, La Jolla, CA 92093, USA
| | - Randolph Y Hampton
- Division of Biological Sciences, the Section of Cell and Developmental Biology, University of California San Diego, La Jolla, CA 92093, USA
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18
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Garrison P, Bangs JD. p97 Inhibitor CB-5083 Blocks ERAD in Trypanosoma brucei. Mol Biochem Parasitol 2020; 239:111313. [PMID: 32735998 DOI: 10.1016/j.molbiopara.2020.111313] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 07/22/2020] [Accepted: 07/23/2020] [Indexed: 11/26/2022]
Abstract
Misfolded proteins trapped in the endoplasmic reticulum (ER) are specifically recognized and retrotranslocated to the cytosol by the ER-Associated Degradation (ERAD) system and delivered to the proteasome for destruction. This process was recently described in Trypanosoma brucei (T. brucei) using the misfolded epitope tagged Transferrin Receptor subunits ESAG7:Ty and HA:ESAG6 (HA:E6). Critical to this work was the proteasomal inhibitor MG132. However, MG132 has off-target inhibitory effects on lysosomal Cathepsin L that could cause misinterpretation of turnover results. Here, we evaluate an orally bioavailable p97 inhibitor, CB-5083, for use in T. brucei. p97 is a ubiquitous protein involved in many cellular events including the membrane extraction step of ERAD. CB-5083 strongly inhibits turnover of HA:E6, with comparable protein recovery to MG132 treatment. Interestingly, little deglycosylated cytoplasmic species accumulates, though it normally emerges with MG132 treatment. This suggests that CB-5083 blocks ERAD upstream of the proteasome, as expected for inhibition of the trypanosomal p97 orthologue TbVCP. Under CB-5083 treatment, HA:E6 is also strongly membrane-associated, suggesting ER localization. Finally, we provide an experimental example where CB-5083 treatment offers clarity to the off-target effects of MG132 treatment.
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Affiliation(s)
- Paige Garrison
- Department of Microbiology and Immunology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo (SUNY), Buffalo, NY, 14203, USA
| | - James D Bangs
- Department of Microbiology and Immunology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo (SUNY), Buffalo, NY, 14203, USA.
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19
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Shrestha N, Liu T, Ji Y, Reinert RB, Torres M, Li X, Zhang M, Tang CHA, Hu CCA, Liu C, Naji A, Liu M, Lin JD, Kersten S, Arvan P, Qi L. Sel1L-Hrd1 ER-associated degradation maintains β cell identity via TGF-β signaling. J Clin Invest 2020; 130:3499-3510. [PMID: 32182217 PMCID: PMC7324191 DOI: 10.1172/jci134874] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2019] [Accepted: 03/11/2020] [Indexed: 12/21/2022] Open
Abstract
β Cell apoptosis and dedifferentiation are 2 hotly debated mechanisms underlying β cell loss in type 2 diabetes; however, the molecular drivers underlying such events remain largely unclear. Here, we performed a side-by-side comparison of mice carrying β cell-specific deletion of ER-associated degradation (ERAD) and autophagy. We reported that, while autophagy was necessary for β cell survival, the highly conserved Sel1L-Hrd1 ERAD protein complex was required for the maintenance of β cell maturation and identity. Using single-cell RNA-Seq, we demonstrated that Sel1L deficiency was not associated with β cell loss, but rather loss of β cell identity. Sel1L-Hrd1 ERAD controlled β cell identity via TGF-β signaling, in part by mediating the degradation of TGF-β receptor 1. Inhibition of TGF-β signaling in Sel1L-deficient β cells augmented the expression of β cell maturation markers and increased the total insulin content. Our data revealed distinct pathogenic effects of 2 major proteolytic pathways in β cells, providing a framework for therapies targeting distinct mechanisms of protein quality control.
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Affiliation(s)
- Neha Shrestha
- Department of Molecular and Integrative Physiology, University of Michigan Medical School
| | - Tongyu Liu
- Life Sciences Institute, University of Michigan, and
- Department of Cell and Developmental Biology and
| | - Yewei Ji
- Department of Molecular and Integrative Physiology, University of Michigan Medical School
| | - Rachel B. Reinert
- Division of Metabolism, Endocrinology and Diabetes, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Mauricio Torres
- Department of Molecular and Integrative Physiology, University of Michigan Medical School
| | - Xin Li
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
| | - Maria Zhang
- College of Literature, Science, and the Arts, University of Michigan, Ann Arbor, Michigan, USA
| | - Chih-Hang Anthony Tang
- Immunology, Microenvironment, Metastasis Program, Wistar Institute, Philadelphia, Pennsylvania, USA
| | - Chih-Chi Andrew Hu
- Immunology, Microenvironment, Metastasis Program, Wistar Institute, Philadelphia, Pennsylvania, USA
| | - Chengyang Liu
- Department of Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Ali Naji
- Department of Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Ming Liu
- Division of Metabolism, Endocrinology and Diabetes, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan, USA
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
| | - Jiandie D. Lin
- Life Sciences Institute, University of Michigan, and
- Department of Cell and Developmental Biology and
| | - Sander Kersten
- Nutrition, Metabolism and Genomics group, Wageningen University, Wageningen, Netherlands
| | - Peter Arvan
- Department of Molecular and Integrative Physiology, University of Michigan Medical School
- Division of Metabolism, Endocrinology and Diabetes, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Ling Qi
- Department of Molecular and Integrative Physiology, University of Michigan Medical School
- Division of Metabolism, Endocrinology and Diabetes, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan, USA
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20
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Schmidt CC, Vasic V, Stein A. Doa10 is a membrane protein retrotranslocase in ER-associated protein degradation. eLife 2020; 9:56945. [PMID: 32588820 PMCID: PMC7319771 DOI: 10.7554/elife.56945] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2020] [Accepted: 05/28/2020] [Indexed: 12/17/2022] Open
Abstract
In endoplasmic reticulum-associated protein degradation (ERAD), membrane proteins are ubiquitinated, extracted from the membrane, and degraded by the proteasome. The cytosolic ATPase Cdc48 drives extraction by pulling on polyubiquitinated substrates. How hydrophobic transmembrane (TM) segments are moved from the phospholipid bilayer into cytosol, often together with hydrophilic and folded ER luminal protein parts, is not known. Using a reconstituted system with purified proteins from Saccharomyces cerevisiae, we show that the ubiquitin ligase Doa10 (Teb-4/MARCH6 in animals) is a retrotranslocase that facilitates membrane protein extraction. A substrate’s TM segment interacts with the membrane-embedded domain of Doa10 and then passively moves into the aqueous phase. Luminal substrate segments cross the membrane in an unfolded state. Their unfolding occurs on the luminal side of the membrane by cytoplasmic Cdc48 action. Our results reveal how a membrane-bound retrotranslocase cooperates with the Cdc48 ATPase in membrane protein extraction. The inside of a cell contains many different compartments called organelles, which are separated by membranes. Each organelle is composed of a unique set of proteins and performs specific roles in the cell. The endoplasmic reticulum, or ER for short, is an organelle where many proteins are produced. Most of these proteins are then released from the cell or sorted to other organelles. The ER has a strict quality control system that ensures any faulty proteins are quickly marked for the cell to destroy. However, the destruction process itself does not happen in the ER, so faulty proteins first need to leave this organelle. This is achieved by a group of proteins known as endoplasmic reticulum-associated protein degradation machinery (or ERAD for short). To extract a faulty protein from the ER, proteins of the ER and outside the ER cooperate. First, an ERAD protein called Doa10 attaches a small protein tag called ubiquitin to the faulty proteins to mark them for destruction. Then, outside of the ER, a protein called Cdc48 ‘grabs’ the ubiquitin tag and pulls. But that is only part of the story. Many of the proteins made by the ER have tethers that anchor them firmly to the membrane, making them much harder to remove. To get a better idea of how the extraction works, Schmidt et al. rebuilt the ERAD machinery in a test tube. This involved purifying proteins from yeast and inserting them into artificial membranes, allowing closer study of each part of the process. This revealed that attaching ubiquitin tags to faulty proteins is only one part of Doa10's role; it also participates in the extraction itself. Part of Doa10 resides within the membrane, and this ‘membrane-spanning domain’ can interact with faulty proteins, loosening their membrane anchors. At the same time, Cdc48 pulls from the outside. This pulling force causes the faulty proteins to unfold, allowing them to pass through the membrane. Given these findings, the next step is to find out exactly how Doa10 works by looking at its three-dimensional structure. This could have implications not only for the study of ERAD, but of similar quality control processes in other organelles too. A build-up of faulty proteins can cause diseases like neurodegeneration, so understanding how cells remove faulty proteins could help future medical research.
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Affiliation(s)
- Claudia C Schmidt
- Research Group Membrane Protein Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Vedran Vasic
- Research Group Membrane Protein Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Alexander Stein
- Research Group Membrane Protein Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
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21
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Genetic Selection Based on a Ste6 *C-HA-Ura3 Substrate Identifies New Cytosolic Quality Control Alleles in Saccharomyces cerevisiae. G3-GENES GENOMES GENETICS 2020; 10:1879-1891. [PMID: 32299823 PMCID: PMC7263692 DOI: 10.1534/g3.120.401186] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Protein quality control in the cytosol (CytoQC) is an important cellular pathway consisting of a network of components which monitor the folding of cytosolic proteins and ensure the efficient removal of aberrant ones. Our understanding of CytoQC mechanisms is limited in part by the ability of current approaches to identify new genes in the pathway. In this study, we developed a CytoQC reporter substrate, Ste6*C-HA-Ura3, for a new genetic selection of spontaneous CytoQC mutations in the yeast Saccharomyces cerevisiae In addition to UBR1, which encodes for a known CytoQC E3 ligase, we identified six new CytoQC candidates. In the preliminary characterization of two mutants, we found that Doa4 is involved in the degradation of misfolded substrates while Pup2 functions in the selectivity of CytoQC and ERAD substrates. Overall, the strategy demonstrates the potential to identify novel genes and advance our understanding of CytoQC.
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22
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The degradation-promoting roles of deubiquitinases Ubp6 and Ubp3 in cytosolic and ER protein quality control. PLoS One 2020; 15:e0232755. [PMID: 32401766 PMCID: PMC7219781 DOI: 10.1371/journal.pone.0232755] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Accepted: 04/21/2020] [Indexed: 11/19/2022] Open
Abstract
The quality control of intracellular proteins is achieved by degrading misfolded proteins which cannot be refolded by molecular chaperones. In eukaryotes, such degradation is handled primarily by the ubiquitin-proteasome system. However, it remained unclear whether and how protein quality control deploys various deubiquitinases. To address this question, we screened deletions or mutation of the 20 deubiquitinase genes in Saccharomyces cerevisiae and discovered that almost half of the mutations slowed the removal of misfolded proteins whereas none of the remaining mutations accelerated this process significantly. Further characterization revealed that Ubp6 maintains the level of free ubiquitin to promote the elimination of misfolded cytosolic proteins, while Ubp3 supports the degradation of misfolded cytosolic and ER luminal proteins by different mechanisms.
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23
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Oikonomou C, Hendershot LM. Disposing of misfolded ER proteins: A troubled substrate's way out of the ER. Mol Cell Endocrinol 2020; 500:110630. [PMID: 31669350 PMCID: PMC6911830 DOI: 10.1016/j.mce.2019.110630] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Revised: 09/19/2019] [Accepted: 10/20/2019] [Indexed: 12/12/2022]
Abstract
Secreted, plasma membrane, and resident proteins of the secretory pathway are synthesized in the endoplasmic reticulum (ER) where they undergo post-translational modifications, oxidative folding, and subunit assembly in tightly monitored processes. An ER quality control (ERQC) system oversees protein maturation and ensures that only those reaching their native state will continue trafficking into the secretory pathway to reach their final destinations. Those that fail must be recognized and eliminated to maintain ER homeostasis. Two cellular mechanisms have been identified to rid the ER of terminally unfolded, misfolded, and aggregated proteins. ER-associated degradation (ERAD) was discovered nearly 30 years ago and entails the identification of improperly matured secretory pathway proteins and their retrotranslocation to the cytosol for degradation by the ubiquitin-proteasome system. ER-phagy has been more recently described and caters to larger, more complex proteins and protein aggregates that are not readily handled by ERAD. This pathway has unique upstream components and relies on the same downstream effectors of autophagy used in other cellular processes to deliver clients to lysosomes for degradation. In this review, we describe the main elements of ERQC, ERAD, and ER-phagy and focus on recent advances in these fields.
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Affiliation(s)
- Christina Oikonomou
- St. Jude Children's Research Hospital, Memphis, TN, 38104, USA; The University of Tennessee Health Science Center, Memphis, TN, USA
| | - Linda M Hendershot
- St. Jude Children's Research Hospital, Memphis, TN, 38104, USA; The University of Tennessee Health Science Center, Memphis, TN, USA.
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24
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Amaya Y, Nakai T. Localization and ER membrane insertion of parathyroid hormone-related protein analyzed without effects of reporter proteins. FEBS Lett 2019; 594:383-392. [PMID: 31471966 DOI: 10.1002/1873-3468.13592] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Revised: 08/21/2019] [Accepted: 08/22/2019] [Indexed: 11/12/2022]
Abstract
Parathyroid hormone-related protein (PTHrP) is transported to both the secretory pathway and the nucleus/nucleolus by its dual targeting signals, that is, an N-terminal signal peptide and nuclear targeting signal. Curiously, reporter proteins such as enhanced green fluorescent protein strongly affect the localization of the fusion protein. Here, we report a novel methionine tag for 35 S-labelling added to the C-terminus of its prepro-form, which has no methionine and cysteine residue other than the initiation methionine that enables analyses of the molecular mechanism of its dual localization without the effects of the reporter proteins. Mutational analyses including insertion of a glycosylation site for the tagged PTHrP revealed that the evolutionarily conserved regions in the signal peptide and the pro-region facilitate the redirection of ppPTHrP from the secretory pathway to the nuclear targeting pathway.
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Affiliation(s)
- Yoshihiro Amaya
- Division of Biochemistry, Niigata University Graduate School of Medical and Dental Sciences, Japan
| | - Toshiki Nakai
- Radioisotope Research Center, Yokohama City University School of Medicine, Japan
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25
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Pastushok L, Fu Y, Lin L, Luo Y, DeCoteau JF, Lee K, Geyer CR. A Novel Cell-Penetrating Antibody Fragment Inhibits the DNA Repair Protein RAD51. Sci Rep 2019; 9:11227. [PMID: 31375703 PMCID: PMC6677837 DOI: 10.1038/s41598-019-47600-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Accepted: 07/15/2019] [Indexed: 12/19/2022] Open
Abstract
DNA damaging chemotherapies are successful in cancer therapy, however, the damage can be reversed by DNA repair mechanisms that may be up-regulated in cancer cells. We hypothesized that inhibiting RAD51, a protein involved in homologous recombination DNA repair, would block DNA repair and restore the effectiveness of DNA damaging chemotherapy. We used phage-display to generate a novel synthetic antibody fragment that bound human RAD51 with high affinity (KD = 8.1 nM) and inhibited RAD51 ssDNA binding in vitro. As RAD51 is an intracellular target, we created a corresponding intrabody fragment that caused a strong growth inhibitory phenotype on human cells in culture. We then used a novel cell-penetrating peptide "iPTD" fusion to generate a therapeutically relevant antibody fragment that effectively entered living cells and enhanced the cell-killing effect of a DNA alkylating agent. The iPTD may be similarly useful as a cell-penetrating peptide for other antibody fragments and open the door to numerous intracellular targets previously off-limits in living cells.
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Affiliation(s)
- Landon Pastushok
- Department of Pathology and Lab Medicine, University of Saskatchewan, Saskatoon, Canada
- Advanced Diagnostics Research Lab, Saskatchewan Cancer Agency, Saskatoon, Canada
| | - Yongpeng Fu
- Department of Pathology and Lab Medicine, University of Saskatchewan, Saskatoon, Canada
| | - Leo Lin
- iProgen Biotech Inc., Burnaby, Canada
| | - Yu Luo
- Department of Biochemistry, University of Saskatchewan, Saskatoon, Canada
| | - John F DeCoteau
- Department of Pathology and Lab Medicine, University of Saskatchewan, Saskatoon, Canada
- Advanced Diagnostics Research Lab, Saskatchewan Cancer Agency, Saskatoon, Canada
| | - Ken Lee
- iProgen Biotech Inc., Burnaby, Canada
| | - C Ronald Geyer
- Department of Pathology and Lab Medicine, University of Saskatchewan, Saskatoon, Canada.
- Advanced Diagnostics Research Lab, Saskatchewan Cancer Agency, Saskatoon, Canada.
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26
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Sasaki K, Yoshida H. Golgi stress response and organelle zones. FEBS Lett 2019; 593:2330-2340. [PMID: 31344260 DOI: 10.1002/1873-3468.13554] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Revised: 07/21/2019] [Accepted: 07/22/2019] [Indexed: 12/29/2022]
Abstract
Organelles have been studied traditionally as single units, but a novel concept is now emerging: each organelle has distinct functional zones that regulate specific functions. The Golgi apparatus seems to have various zones, including zones for: glycosylphosphatidylinositol-anchored proteins; proteoglycan, mucin and lipid glycosylation; transport of cholesterol and ceramides; protein degradation (Golgi membrane-associated degradation); and signalling for apoptosis. The capacity for these specific functions and the size of the corresponding zones appear to be tightly regulated by the Golgi stress response to accommodate cellular demands. For instance, the proteoglycan and mucin zones seem to be separately augmented during the differentiation of chondrocytes and goblet cells, respectively. The mammalian Golgi stress response consists of several response pathways. The TFE3 pathway regulates the general function of the Golgi, such as structural maintenance, N-glycosylation and vesicular transport, whereas the proteoglycan pathway increases the expression of glycosylation enzymes for proteoglycans. The CREB3 and HSP47 pathways regulate pro- and anti-apoptotic functions, respectively. These observations indicate that the Golgi is a dynamic organelle, the capacity of which is upregulated according to cellular needs.
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Affiliation(s)
- Kanae Sasaki
- Department of Molecular Biochemistry, Graduate School of Life Science, University of Hyogo, Japan
| | - Hiderou Yoshida
- Department of Molecular Biochemistry, Graduate School of Life Science, University of Hyogo, Japan
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27
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Balancing the Photoreceptor Proteome: Proteostasis Network Therapeutics for Inherited Retinal Disease. Genes (Basel) 2019; 10:genes10080557. [PMID: 31344897 PMCID: PMC6722924 DOI: 10.3390/genes10080557] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Revised: 07/09/2019] [Accepted: 07/16/2019] [Indexed: 12/17/2022] Open
Abstract
The light sensing outer segments of photoreceptors (PRs) are renewed every ten days due to their high photoactivity, especially of the cones during daytime vision. This demands a tremendous amount of energy, as well as a high turnover of their main biosynthetic compounds, membranes, and proteins. Therefore, a refined proteostasis network (PN), regulating the protein balance, is crucial for PR viability. In many inherited retinal diseases (IRDs) this balance is disrupted leading to protein accumulation in the inner segment and eventually the death of PRs. Various studies have been focusing on therapeutically targeting the different branches of the PR PN to restore the protein balance and ultimately to treat inherited blindness. This review first describes the different branches of the PN in detail. Subsequently, insights are provided on how therapeutic compounds directed against the different PN branches might slow down or even arrest the appalling, progressive blinding conditions. These insights are supported by findings of PN modulators in other research disciplines.
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28
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Guerriero CJ, Gomez YK, Daskivich GJ, Reutter KR, Augustine AA, Weiberth KF, Nakatsukasa K, Grabe M, Brodsky JL. Harmonizing Experimental Data with Modeling to Predict Membrane Protein Insertion in Yeast. Biophys J 2019; 117:668-678. [PMID: 31399214 DOI: 10.1016/j.bpj.2019.07.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 06/26/2019] [Accepted: 07/08/2019] [Indexed: 02/06/2023] Open
Abstract
Membrane proteins must adopt their proper topologies within biological membranes, but achieving the correct topology is compromised by the presence of marginally hydrophobic transmembrane helices (TMHs). In this study, we report on a new model membrane protein in yeast that harbors two TMHs fused to an unstable nucleotide-binding domain. Because the second helix (TMH2) in this reporter has an unfavorable predicted free energy of insertion, we employed established methods to generate variants that alter TMH2 insertion free energy. We first found that altering TMH2 did not significantly affect the extent of protein degradation by the cellular quality control machinery. Next, we correlated predicted insertion free energies from a knowledge-based energy scale with the measured apparent free energies of TMH2 insertion. Although the predicted and apparent insertion energies showed a similar trend, the predicted free-energy changes spanned an unanticipated narrow range. By instead using a physics-based model, we obtained a broader range of free energies that agreed considerably better with the magnitude of the experimentally derived values. Nevertheless, some variants still inserted better in yeast than predicted from energy-based scales. Therefore, molecular dynamics simulations were performed and indicated that the corresponding mutations induced conformational changes within TMH2, which altered the number of stabilizing hydrogen bonds. Together, our results offer insight into the ability of the cellular quality control machinery to recognize conformationally distinct misfolded topomers, provide a model to assess TMH insertion in vivo, and indicate that TMH insertion energy scales may be limited depending on the specific protein and the mutation present.
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Affiliation(s)
| | - Yessica K Gomez
- Cardiovascular Research Institute, Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, California
| | - Grant J Daskivich
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Karl-Richard Reutter
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Andrew A Augustine
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Kurt F Weiberth
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Kunio Nakatsukasa
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania; Division of Biological Science, Graduate School of Natural Sciences, Nagoya City University, Nagoya, Aichi, Japan
| | - Michael Grabe
- Cardiovascular Research Institute, Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, California
| | - Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania
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29
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Gupta AK, Scully ED, Palmer NA, Geib SM, Sarath G, Hein GL, Tatineni S. Wheat streak mosaic virus alters the transcriptome of its vector, wheat curl mite (Aceria tosichella Keifer), to enhance mite development and population expansion. J Gen Virol 2019; 100:889-910. [PMID: 31017568 DOI: 10.1099/jgv.0.001256] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Wheat streak mosaic virus (WSMV; genus Tritimovirus; family Potyviridae) is an economically important wheat virus that is transmitted by the wheat curl mite (WCM; Aceria tosichella Keifer) in a persistent manner. Virus-vector coevolution may potentially influence vector gene expression to prolong viral association and thus increase virus transmission efficiency and spread. To understand the transcriptomic responses of WCM to WSMV, RNA sequencing was performed to assemble and analyse transcriptomes of WSMV viruliferous and aviruliferous mites. Among 7291 de novo-assembled unigenes, 1020 were differentially expressed between viruliferous and aviruliferous WCMs using edgeR at a false discovery rate ≤0.05. Differentially expressed unigenes were enriched for 108 gene ontology terms, with the majority of the unigenes showing downregulation in viruliferous mites in comparison to only a few unigenes that were upregulated. Protein family and metabolic pathway enrichment analyses revealed that most downregulated unigenes encoded enzymes and proteins linked to stress response, immunity and development. Mechanistically, these predicted changes in mite physiology induced by viral association could be suggestive of pathways needed for promoting virus-vector interactions. Overall, our data suggest that transcriptional changes in viruliferous mites facilitate prolonged viral association and alter WCM development to expedite population expansion, both of which could enhance viral transmission.
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Affiliation(s)
- Adarsh K Gupta
- 1Department of Plant Pathology, University of Nebraska-Lincoln, Lincoln, NE 68583, USA
| | - Erin D Scully
- 2Center for Grain and Animal Health Research, Stored Product Insect and Entomology Research Unit, United States Department of Agriculture-Agricultural Research Services (USDA-ARS), Manhattan, KS 66502, USA
| | - Nathan A Palmer
- 3Wheat, Sorghum, and Forage Research Unit, USDA-ARS, Lincoln, NE 68583, USA
| | - Scott M Geib
- 4Daniel K. Inouye US Pacific Basin Agricultural Research Center, USDA-ARS, Hilo, HI 96720, USA
| | - Gautam Sarath
- 3Wheat, Sorghum, and Forage Research Unit, USDA-ARS, Lincoln, NE 68583, USA.,5Department of Agronomy and Horticulture, University of Nebraska-Lincoln, Lincoln, NE 68583, USA
| | - Gary L Hein
- 6Department of Entomology, University of Nebraska-Lincoln, Lincoln, NE 68583, USA
| | - Satyanarayana Tatineni
- 1Department of Plant Pathology, University of Nebraska-Lincoln, Lincoln, NE 68583, USA.,3Wheat, Sorghum, and Forage Research Unit, USDA-ARS, Lincoln, NE 68583, USA
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Abstract
Elimination of misfolded proteins by endoplasmic reticulum (ER)-associated protein degradation (ERAD) ensures that proteins proceeding through the secretory pathway are correctly folded and processed, which is critical to minimize ER stress. All ERAD pathways include a protein translocation process termed retrotranslocation, in which ubiquitinated misfolded substrates are extracted from the ER and degraded by the cytosolic 26S proteasome. Despite being integral to ERAD, the retrotranslocation process has been largely obscure. Recently, an explosion of discoveries has provided key mechanistic insights into this novel route of protein transport. These advances were facilitated by the development of in vitro and in vivo assays that utilize components from the yeast Saccharomyces cerevisiae. The assays permit detailed study of the distinct steps in ERAD-linked retrotranslocation, including ubiquitination of selected ERAD substrates, substrate removal from the ER, maintenance of cytosolic substrate solubility in the cytosol, and substrate degradation. Here we provide detailed protocols for these assays that pertain to work on retrotranslocation of integral membrane proteins (ERAD-M substrates), with the expectation that these approaches can be adapted for many related biochemical processes.
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Affiliation(s)
- Sonya Neal
- Division of Biological Sciences, The Section of Cell and Developmental Biology, University of California San Diego, La Jolla, CA, United States.
| | - Sascha H Duttke
- Department of Medicine, University of California San Diego, La Jolla, CA, United States
| | - Randolph Y Hampton
- Division of Biological Sciences, The Section of Cell and Developmental Biology, University of California San Diego, La Jolla, CA, United States
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31
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Benarroch R, Austin JM, Ahmed F, Isaacson RL. The roles of cytosolic quality control proteins, SGTA and the BAG6 complex, in disease. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2019; 114:265-313. [PMID: 30635083 PMCID: PMC7102839 DOI: 10.1016/bs.apcsb.2018.11.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
SGTA is a co-chaperone that, in collaboration with the complex of BAG6/UBL4A/TRC35, facilitates the biogenesis and quality control of hydrophobic proteins, protecting them from the aqueous cytosolic environment. This work includes targeting tail-anchored proteins to their resident membranes, sorting of membrane and secretory proteins that mislocalize to the cytoplasm and endoplasmic reticulum-associated degradation of misfolded proteins. Since these functions are all vital for the cell's continued proteostasis, their disruption poses a threat to the cell, with a particular risk of protein aggregation, a phenomenon that underpins many diseases. Although the specific disease implications of machinery involved in quality control of hydrophobic substrates are poorly understood, here we summarize much of the available information on this topic.
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Affiliation(s)
- Rashi Benarroch
- Department of Chemistry, King's College London, London, United Kingdom
| | - Jennifer M Austin
- Department of Chemistry, King's College London, London, United Kingdom
| | - Fahmeda Ahmed
- Department of Chemistry, King's College London, London, United Kingdom
| | - Rivka L Isaacson
- Department of Chemistry, King's College London, London, United Kingdom.
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32
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Hochstrasser M. Preface. Methods Enzymol 2019; 619:xv-xvii. [DOI: 10.1016/s0076-6879(19)30113-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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33
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Dibdiakova K, Saksonova S, Pilchova I, Klacanova K, Tatarkova Z, Racay P. Both thapsigargin- and tunicamycin-induced endoplasmic reticulum stress increases expression of Hrd1 in IRE1-dependent fashion. Neurol Res 2018; 41:177-188. [DOI: 10.1080/01616412.2018.1547856] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Katarina Dibdiakova
- Jessenius Faculty of Medicine in Martin (JFM CU), Biomedical Center Martin JFM CU and Department of Medical Biochemistry JFM CU, Comenius University in Bratislava, Martin, Slovakia
| | - Simona Saksonova
- Jessenius Faculty of Medicine in Martin (JFM CU), Biomedical Center Martin JFM CU and Department of Medical Biochemistry JFM CU, Comenius University in Bratislava, Martin, Slovakia
| | - Ivana Pilchova
- Jessenius Faculty of Medicine in Martin (JFM CU), Biomedical Center Martin JFM CU and Department of Medical Biochemistry JFM CU, Comenius University in Bratislava, Martin, Slovakia
| | - Katarina Klacanova
- Jessenius Faculty of Medicine in Martin (JFM CU), Biomedical Center Martin JFM CU and Department of Medical Biochemistry JFM CU, Comenius University in Bratislava, Martin, Slovakia
| | - Zuzana Tatarkova
- Jessenius Faculty of Medicine in Martin (JFM CU), Biomedical Center Martin JFM CU and Department of Medical Biochemistry JFM CU, Comenius University in Bratislava, Martin, Slovakia
| | - Peter Racay
- Jessenius Faculty of Medicine in Martin (JFM CU), Biomedical Center Martin JFM CU and Department of Medical Biochemistry JFM CU, Comenius University in Bratislava, Martin, Slovakia
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34
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Depaoli MR, Hay JC, Graier WF, Malli R. The enigmatic ATP supply of the endoplasmic reticulum. Biol Rev Camb Philos Soc 2018; 94:610-628. [PMID: 30338910 PMCID: PMC6446729 DOI: 10.1111/brv.12469] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Revised: 08/20/2018] [Accepted: 08/30/2018] [Indexed: 12/11/2022]
Abstract
The endoplasmic reticulum (ER) is a functionally and morphologically complex cellular organelle largely responsible for a variety of crucial functions, including protein folding, maturation and degradation. Furthermore, the ER plays an essential role in lipid biosynthesis, dynamic Ca2+ storage, and detoxification. Malfunctions in ER‐related processes are responsible for the genesis and progression of many diseases, such as heart failure, cancer, neurodegeneration and metabolic disorders. To fulfill many of its vital functions, the ER relies on a sufficient energy supply in the form of adenosine‐5′‐triphosphate (ATP), the main cellular energy source. Despite landmark discoveries and clarification of the functional principles of ER‐resident proteins and key ER‐related processes, the mechanism underlying ER ATP transport remains somewhat enigmatic. Here we summarize ER‐related ATP‐consuming processes and outline our knowledge about the nature and function of the ER energy supply.
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Affiliation(s)
- Maria R Depaoli
- Molecular Biology and Biochemistry, Gottfried Schatz Research Center, Medical University of Graz, Neue Stiftingtalstraße 6/6, 8010 Graz, Austria
| | - Jesse C Hay
- Division of Biological Sciences and Center for Structural and Functional Neuroscience, The University of Montana, 32 Campus Drive, HS410, Missoula, MT 59812-4824, U.S.A
| | - Wolfgang F Graier
- Molecular Biology and Biochemistry, Gottfried Schatz Research Center, Medical University of Graz, Neue Stiftingtalstraße 6/6, 8010 Graz, Austria.,BioTechMed Graz, Mozartgasse 12/II, 8010 Graz, Austria
| | - Roland Malli
- Molecular Biology and Biochemistry, Gottfried Schatz Research Center, Medical University of Graz, Neue Stiftingtalstraße 6/6, 8010 Graz, Austria.,BioTechMed Graz, Mozartgasse 12/II, 8010 Graz, Austria
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35
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Moon HW, Han HG, Jeon YJ. Protein Quality Control in the Endoplasmic Reticulum and Cancer. Int J Mol Sci 2018; 19:E3020. [PMID: 30282948 PMCID: PMC6213883 DOI: 10.3390/ijms19103020] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2018] [Revised: 09/22/2018] [Accepted: 10/01/2018] [Indexed: 12/21/2022] Open
Abstract
The endoplasmic reticulum (ER) is an essential compartment of the biosynthesis, folding, assembly, and trafficking of secretory and transmembrane proteins, and consequently, eukaryotic cells possess specialized machineries to ensure that the ER enables the proteins to acquire adequate folding and maturation for maintaining protein homeostasis, a process which is termed proteostasis. However, a large variety of physiological and pathological perturbations lead to the accumulation of misfolded proteins in the ER, which is referred to as ER stress. To resolve ER stress and restore proteostasis, cells have evolutionary conserved protein quality-control machineries of the ER, consisting of the unfolded protein response (UPR) of the ER, ER-associated degradation (ERAD), and autophagy. Furthermore, protein quality-control machineries of the ER play pivotal roles in the control of differentiation, progression of cell cycle, inflammation, immunity, and aging. Therefore, severe and non-resolvable ER stress is closely associated with tumor development, aggressiveness, and response to therapies for cancer. In this review, we highlight current knowledge in the molecular understanding and physiological relevance of protein quality control of the ER and discuss new insights into how protein quality control of the ER is implicated in the pathogenesis of cancer, which could contribute to therapeutic intervention in cancer.
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Affiliation(s)
- Hye Won Moon
- Department of Biochemistry, Chungnam National University College of Medicine, Daejeon 35015, Korea.
- Department of Medical Science, Chungnam National University College of Medicine, Daejeon 35015, Korea.
| | - Hye Gyeong Han
- Department of Biochemistry, Chungnam National University College of Medicine, Daejeon 35015, Korea.
- Department of Medical Science, Chungnam National University College of Medicine, Daejeon 35015, Korea.
| | - Young Joo Jeon
- Department of Biochemistry, Chungnam National University College of Medicine, Daejeon 35015, Korea.
- Department of Medical Science, Chungnam National University College of Medicine, Daejeon 35015, Korea.
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36
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Abstract
PURPOSE A large number of studies has investigated proopiomelanocortin processing in anterior pituitary corticotropes but little is known on proopiomelanocortin/ACTH degradation within these cells. The ubiquitin-proteasome system is an intracellular protein degradation pathway which has garnered considerable interest in recent times, given its role in maintenance of protein homeostasis. Aim of the present study was to evaluate the role of the ubiquitin-proteasome system in proopiomelanocortin/ACTH turnover in pituitary corticotropes. METHODS Rat anterior pituitary primary cultures were treated with 0.01-100 nM MG132, a proteasome inhibitor, or 0.1-100 nM K48R, an inhibitor of polyubiquitylation, for 4 and 24 h and ACTH concentrations in medium and cell lysates estimated by immunometric assay. Co-immunoprecipitation for ubiquitin and ACTH was carried out to establish ubiquitin-tagged protein products. RESULTS Inhibition of proteasome-mediated degradation with MG132 lead to an increase in ACTH concentrations, both as regards secretion and cell content. Likewise, inhibition of polyubiquitylation was associated with increased ACTH secretion and cell content. Ubiquitin/ACTH co-immunoprecipitation revealed that proopiomelanocortin was a target of ubiquitylation. CONCLUSIONS We provide the first evidence that the ubiquitin-proteasome system is involved in proopiomelanocortin/ACTH degradation in corticotropes. Indeed, proopiomelanocortin is a target of ubiquitylation and modulation of ubiquitin-proteasome system affects ACTH turnover. This study shows that regulation of ACTH proteolytic degradation may represent a means to control ACTH secretion.
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Affiliation(s)
- Antonella Sesta
- Neuroendocrinology Research Laboratory, Istituto Auxologico Italiano IRCCS, Cusano Milanino (Milan), Milan, Italy
| | - Maria Francesca Cassarino
- Neuroendocrinology Research Laboratory, Istituto Auxologico Italiano IRCCS, Cusano Milanino (Milan), Milan, Italy
| | - Francesco Cavagnini
- Neuroendocrinology Research Laboratory, Istituto Auxologico Italiano IRCCS, Cusano Milanino (Milan), Milan, Italy
| | - Francesca Pecori Giraldi
- Neuroendocrinology Research Laboratory, Istituto Auxologico Italiano IRCCS, Cusano Milanino (Milan), Milan, Italy.
- Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy.
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37
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Tiengwe C, Koeller CM, Bangs JD. Endoplasmic reticulum-associated degradation and disposal of misfolded GPI-anchored proteins in Trypanosoma brucei. Mol Biol Cell 2018; 29:2397-2409. [PMID: 30091673 PMCID: PMC6233060 DOI: 10.1091/mbc.e18-06-0380] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Misfolded secretory proteins are retained by endoplasmic reticulum quality control (ERQC) and degraded in the proteasome by ER-associated degradation (ERAD). However, in yeast and mammals, misfolded glycosylphosphatidylinositol (GPI)-anchored proteins are preferentially degraded in the vacuole/lysosome. We investigate this process in the divergent eukaryotic pathogen Trypanosoma brucei using a misfolded GPI-anchored subunit (HA:E6) of the trypanosome transferrin receptor. HA:E6 is N-glycosylated and GPI-anchored and accumulates in the ER as aggregates. Treatment with MG132, a proteasome inhibitor, generates a smaller protected polypeptide (HA:E6*), consistent with turnover in the proteasome. HA:E6* partitions between membrane and cytosol fractions, and both pools are proteinase K-sensitive, indicating cytosolic disposition of membrane-associated HA:E6*. HA:E6* is de-N-glycosylated and has a full GPI-glycan structure from which dimyristoylglycerol has been removed, indicating that complete GPI removal is not a prerequisite for proteasomal degradation. However, HA:E6* is apparently not ubiquitin-modified. The trypanosome GPI anchor is a forward trafficking signal; thus the dynamic tension between ERQC and ER exit favors degradation by ERAD. These results differ markedly from the standard eukaryotic model systems and may indicate an evolutionary advantage related to pathogenesis.
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Affiliation(s)
- Calvin Tiengwe
- Department of Microbiology and Immunology, School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY 14214
| | - Carolina M Koeller
- Department of Microbiology and Immunology, School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY 14214
| | - James D Bangs
- Department of Microbiology and Immunology, School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY 14214
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38
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Yu S, Ito S, Wada I, Hosokawa N. ER-resident protein 46 (ERp46) triggers the mannose-trimming activity of ER degradation-enhancing α-mannosidase-like protein 3 (EDEM3). J Biol Chem 2018; 293:10663-10674. [PMID: 29784879 DOI: 10.1074/jbc.ra118.003129] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2018] [Revised: 05/16/2018] [Indexed: 11/06/2022] Open
Abstract
Protein folding in the cell is regulated by several quality-control mechanisms. Correct folding of glycoproteins in the endoplasmic reticulum (ER) is tightly monitored by the recognition of glycan signals by lectins in the ER-associated degradation (ERAD) pathway. In mammals, mannose trimming from N-glycans is crucial for disposal of misfolded glycoproteins. The mannosidases responsible for this process are ER mannosidase I and ER degradation-enhancing α-mannosidase-like proteins (EDEMs). However, the molecular mechanism of mannose removal by EDEMs remains unclear, partly owing to the difficulty of reconstituting mannosidase activity in vitro Here, our analysis of EDEM3-mediated mannose-trimming activity on a misfolded glycoprotein revealed that ERp46, an ER-resident oxidoreductase, associates stably with EDEM3. This interaction, which depended on the redox activity of ERp46, involved formation of a disulfide bond between the cysteine residues of the ERp46 redox-active sites and the EDEM3 α-mannosidase domain. In a defined in vitro system consisting of recombinant proteins purified from HEK293 cells, the mannose-trimming activity of EDEM3 toward the model misfolded substrate, the glycoprotein T-cell receptor α locus (TCRα), was reconstituted only when ERp46 had established a covalent interaction with EDEM3. On the basis of these findings, we propose that disposal of misfolded glycoproteins through mannose trimming is tightly connected to redox-mediated regulation in the ER.
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Affiliation(s)
- Shangyu Yu
- From the Laboratory of Molecular and Cellular Biology, Institute for Frontier Life and Medical Sciences, Kyoto University, Kyoto 606-8507
| | - Shinji Ito
- the Medical Research Support Center, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, and
| | - Ikuo Wada
- the Department of Cell Sciences, Institute of Biomedical Sciences, Fukushima Medical University School of Medicine, Fukushima 960-1295, Japan
| | - Nobuko Hosokawa
- From the Laboratory of Molecular and Cellular Biology, Institute for Frontier Life and Medical Sciences, Kyoto University, Kyoto 606-8507,
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39
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Berner N, Reutter KR, Wolf DH. Protein Quality Control of the Endoplasmic Reticulum and Ubiquitin-Proteasome-Triggered Degradation of Aberrant Proteins: Yeast Pioneers the Path. Annu Rev Biochem 2018; 87:751-782. [PMID: 29394096 DOI: 10.1146/annurev-biochem-062917-012749] [Citation(s) in RCA: 92] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Cells must constantly monitor the integrity of their macromolecular constituents. Proteins are the most versatile class of macromolecules but are sensitive to structural alterations. Misfolded or otherwise aberrant protein structures lead to dysfunction and finally aggregation. Their presence is linked to aging and a plethora of severe human diseases. Thus, misfolded proteins have to be rapidly eliminated. Secretory proteins constitute more than one-third of the eukaryotic proteome. They are imported into the endoplasmic reticulum (ER), where they are folded and modified. A highly elaborated machinery controls their folding, recognizes aberrant folding states, and retrotranslocates permanently misfolded proteins from the ER back to the cytosol. In the cytosol, they are degraded by the highly selective ubiquitin-proteasome system. This process of protein quality control followed by proteasomal elimination of the misfolded protein is termed ER-associated degradation (ERAD), and it depends on an intricate interplay between the ER and the cytosol.
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Affiliation(s)
- Nicole Berner
- Institute of Biochemistry and Technical Biochemistry, University of Stuttgart, 70569 Stuttgart, Germany; , ,
| | - Karl-Richard Reutter
- Institute of Biochemistry and Technical Biochemistry, University of Stuttgart, 70569 Stuttgart, Germany; , ,
| | - Dieter H Wolf
- Institute of Biochemistry and Technical Biochemistry, University of Stuttgart, 70569 Stuttgart, Germany; , ,
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40
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Neal S, Jaeger PA, Duttke SH, Benner C, K Glass C, Ideker T, Hampton RY. The Dfm1 Derlin Is Required for ERAD Retrotranslocation of Integral Membrane Proteins. Mol Cell 2018; 69:306-320.e4. [PMID: 29351849 PMCID: PMC6049073 DOI: 10.1016/j.molcel.2017.12.012] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Revised: 10/06/2017] [Accepted: 11/15/2017] [Indexed: 12/13/2022]
Abstract
Endoplasmic reticulum (ER)-associated degradation (ERAD) removes misfolded proteins from the ER membrane and lumen by the ubiquitin-proteasome pathway. Retrotranslocation of ubiquitinated substrates to the cytosol is a universal feature of ERAD that requires the Cdc48 AAA-ATPase. Despite intense efforts, the mechanism of ER exit, particularly for integral membrane (ERAD-M) substrates, has remained unclear. Using a self-ubiquitinating substrate (SUS), which undergoes normal retrotranslocation independently of known ERAD factors, and the new SPOCK (single plate orf compendium kit) micro-library to query all yeast genes, we found the rhomboid derlin Dfm1 was required for retrotranslocation of both HRD and DOA ERAD pathway integral membrane substrates. Dfm1 recruited Cdc48 to the ER membrane with its unique SHP motifs, and it catalyzed substrate extraction through its conserved rhomboid motifs. Surprisingly, dfm1Δ can undergo rapid suppression, restoring wild-type ERAD-M. This unexpected suppression explained earlier studies ruling out Dfm1, and it revealed an ancillary ERAD-M retrotranslocation pathway requiring Hrd1.
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Affiliation(s)
- Sonya Neal
- Division of Biological Sciences, the Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Philipp A Jaeger
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA; Biocipher(X), Inc., San Diego, CA 92121, USA
| | - Sascha H Duttke
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Christopher Benner
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Christopher K Glass
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Trey Ideker
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA.
| | - Randolph Y Hampton
- Division of Biological Sciences, the Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA 92093, USA.
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41
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Shim SM, Choi HR, Sung KW, Lee YJ, Kim ST, Kim D, Mun SR, Hwang J, Cha-Molstad H, Ciechanover A, Kim BY, Kwon YT. The endoplasmic reticulum-residing chaperone BiP is short-lived and metabolized through N-terminal arginylation. Sci Signal 2018; 11:11/511/eaan0630. [PMID: 29295953 DOI: 10.1126/scisignal.aan0630] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
BiP and other endoplasmic reticulum (ER)-resident proteins are thought to be metabolically stable and to function primarily in the ER lumen. We sought to assess how the abundance of these proteins dynamically fluctuates in response to various stresses and how their subpopulations are relocated to non-ER compartments such as the cytosol. We showed that the molecular chaperone BiP (also known as GRP78) was short-lived under basal conditions and ER stress. The turnover of BiP was in part driven by its amino-terminal arginylation (Nt-arginylation) by the arginyltransferase ATE1, which generated an autophagic N-degron of the N-end rule pathway. ER stress elicited the formation of R-BiP, an effect that was increased when the proteasome was also inhibited. Nt-arginylation correlated with the cytosolic relocalization of BiP under the types of stress tested. The cytosolic relocalization of BiP did not require the functionality of the unfolded protein response or the Sec61- or Derlin1-containing translocon. A key inhibitor of the turnover and Nt-arginylation of BiP was HERP (homocysteine-responsive ER protein), a 43-kDa ER membrane-integrated protein that is an essential component of ER-associated protein degradation. Pharmacological inhibition of the ER-Golgi secretory pathway also suppressed R-BiP formation. Finally, we showed that cytosolic R-BiP induced by ER stress and proteasomal inhibition was routed to autophagic vacuoles and possibly additional metabolic fates. These results suggest that Nt-arginylation is a posttranslational modification that modulates the function, localization, and metabolic fate of ER-resident proteins.
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Affiliation(s)
- Sang Mi Shim
- Protein Metabolism Medical Research Center, College of Medicine, Seoul National University, Seoul 03080, Republic of Korea.,Department of Biomedical Sciences, College of Medicine, Seoul National University, Seoul 03080, Republic of Korea
| | - Ha Rim Choi
- Protein Metabolism Medical Research Center, College of Medicine, Seoul National University, Seoul 03080, Republic of Korea.,Department of Biomedical Sciences, College of Medicine, Seoul National University, Seoul 03080, Republic of Korea
| | - Ki Woon Sung
- Protein Metabolism Medical Research Center, College of Medicine, Seoul National University, Seoul 03080, Republic of Korea.,Department of Biomedical Sciences, College of Medicine, Seoul National University, Seoul 03080, Republic of Korea
| | - Yoon Jee Lee
- Protein Metabolism Medical Research Center, College of Medicine, Seoul National University, Seoul 03080, Republic of Korea.,Department of Biomedical Sciences, College of Medicine, Seoul National University, Seoul 03080, Republic of Korea
| | - Sung Tae Kim
- Protein Metabolism Medical Research Center, College of Medicine, Seoul National University, Seoul 03080, Republic of Korea.,Department of Biomedical Sciences, College of Medicine, Seoul National University, Seoul 03080, Republic of Korea.,Center for Pharmacogenetics and Department of Pharmaceutical Sciences, School of Pharmacy, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Daeho Kim
- Protein Metabolism Medical Research Center, College of Medicine, Seoul National University, Seoul 03080, Republic of Korea.,Department of Biophysics and Chemical Biology, College of Natural Sciences, Seoul National University, Seoul 08826, Republic of Korea
| | - Su Ran Mun
- Protein Metabolism Medical Research Center, College of Medicine, Seoul National University, Seoul 03080, Republic of Korea.,Department of Biomedical Sciences, College of Medicine, Seoul National University, Seoul 03080, Republic of Korea
| | - Joonsung Hwang
- World Class Institute, Korea Research Institute of Bioscience and Biotechnology, Ochang, Cheongwon 28116, Republic of Korea
| | - Hyunjoo Cha-Molstad
- World Class Institute, Korea Research Institute of Bioscience and Biotechnology, Ochang, Cheongwon 28116, Republic of Korea
| | - Aaron Ciechanover
- Protein Metabolism Medical Research Center, College of Medicine, Seoul National University, Seoul 03080, Republic of Korea.,Tumor and Vascular Biology Research Center, Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Haifa 31096, Israel
| | - Bo Yeon Kim
- World Class Institute, Korea Research Institute of Bioscience and Biotechnology, Ochang, Cheongwon 28116, Republic of Korea.
| | - Yong Tae Kwon
- Protein Metabolism Medical Research Center, College of Medicine, Seoul National University, Seoul 03080, Republic of Korea. .,Department of Biomedical Sciences, College of Medicine, Seoul National University, Seoul 03080, Republic of Korea.,Ischemic/Hypoxic Disease Institute, College of Medicine, Seoul National University, Seoul 03080, Republic of Korea
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42
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Yoo YS, Han HG, Jeon YJ. Unfolded Protein Response of the Endoplasmic Reticulum in Tumor Progression and Immunogenicity. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2017; 2017:2969271. [PMID: 29430279 PMCID: PMC5752989 DOI: 10.1155/2017/2969271] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Accepted: 11/29/2017] [Indexed: 12/11/2022]
Abstract
The endoplasmic reticulum (ER) is a pivotal regulator of folding, quality control, trafficking, and targeting of secreted and transmembrane proteins, and accordingly, eukaryotic cells have evolved specialized machinery to ensure that the ER enables these proteins to acquire adequate folding and maturation in the presence of intrinsic and extrinsic insults. This adaptive capacity of the ER to intrinsic and extrinsic perturbations is important for maintaining protein homeostasis, which is termed proteostasis. Failure in adaptation to these perturbations leads to accumulation of misfolded or unassembled proteins in the ER, which is termed ER stress, resulting in the activation of unfolded protein response (UPR) of the ER and the execution of ER-associated degradation (ERAD) to restore homeostasis. Furthermore, both of the two axes play key roles in the control of tumor progression, inflammation, immunity, and aging. Therefore, understanding UPR of the ER and subsequent ERAD will provide new insights into the pathogenesis of many human diseases and contribute to therapeutic intervention in these diseases.
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Affiliation(s)
- Yoon Seon Yoo
- Department of Biochemistry, Chungnam National University School of Medicine, Daejeon 35015, Republic of Korea
- Department of Medical Science, Chungnam National University School of Medicine, Daejeon 35015, Republic of Korea
| | - Hye Gyeong Han
- Department of Biochemistry, Chungnam National University School of Medicine, Daejeon 35015, Republic of Korea
- Department of Medical Science, Chungnam National University School of Medicine, Daejeon 35015, Republic of Korea
| | - Young Joo Jeon
- Department of Biochemistry, Chungnam National University School of Medicine, Daejeon 35015, Republic of Korea
- Department of Medical Science, Chungnam National University School of Medicine, Daejeon 35015, Republic of Korea
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43
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Gentil J, Hempel F, Moog D, Zauner S, Maier UG. Review: origin of complex algae by secondary endosymbiosis: a journey through time. PROTOPLASMA 2017; 254:1835-1843. [PMID: 28290059 DOI: 10.1007/s00709-017-1098-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Accepted: 03/03/2017] [Indexed: 05/19/2023]
Abstract
Secondary endosymbiosis-the merging of two eukaryotic cells into one photosynthetic cellular unit-led to the evolution of ecologically and medically very important organisms. We review the biology of these organisms, starting from the first proposal of secondary endosymbiosis up to recent phylogenetic models on the origin of secondarily evolved protists. In addition, we discuss the organelle character of the symbionts based on morphological features, gene transfers from the symbiont into the host and re-import of nucleus-encoded plastid proteins. Finally, we hypothesize that secondary endosymbiosis is more than enslaving a eukaryotic, phototrophic cell, but reflects a complex interplay between host and symbiont, leading to the inseparability of the two symbiotic partners generating a cellular entity.
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Affiliation(s)
- J Gentil
- Laboratory for Cell Biology, Philipps University Marburg, Karl-von-Frisch-Str. 8, 35032, Marburg, Germany
| | - F Hempel
- LOEWE Center for Synthetic Microbiology (Synmikro), Hans-Meerwein-Str. 6, 35032, Marburg, Germany
| | - D Moog
- Laboratory for Cell Biology, Philipps University Marburg, Karl-von-Frisch-Str. 8, 35032, Marburg, Germany
| | - S Zauner
- Laboratory for Cell Biology, Philipps University Marburg, Karl-von-Frisch-Str. 8, 35032, Marburg, Germany
| | - U G Maier
- Laboratory for Cell Biology, Philipps University Marburg, Karl-von-Frisch-Str. 8, 35032, Marburg, Germany.
- LOEWE Center for Synthetic Microbiology (Synmikro), Hans-Meerwein-Str. 6, 35032, Marburg, Germany.
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44
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Luo WW, Shu HB. Emerging roles of rhomboid-like pseudoproteases in inflammatory and innate immune responses. FEBS Lett 2017; 591:3182-3189. [PMID: 28815577 DOI: 10.1002/1873-3468.12796] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Revised: 07/28/2017] [Accepted: 08/07/2017] [Indexed: 12/31/2022]
Abstract
Rhomboid-like pseudoproteases are a conserved superfamily of proteins related to the rhomboid intramembrane serine proteases that lack key catalytic residues. iRhom2, a member of the rhomboid-like pseudoprotease superfamily, regulates the maturation and trafficking of ADAM17 and is associated with inflammatory arthritis. Recent studies demonstrate that iRhom2 is also involved in innate immunity by regulating the trafficking and stability of MITA (also called STING), which is a central adaptor in innate antiviral signalling pathways. Here, we summarize recent progress on the roles and mechanisms of iRhom2 and its homologues in innate immunity and also discuss the links between the physiological functions of iRhoms and immunological diseases.
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Affiliation(s)
- Wei-Wei Luo
- Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Hong-Bing Shu
- Medical Research Institute, School of Medicine, Wuhan University, China
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45
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Guerriero CJ, Reutter KR, Augustine AA, Preston GM, Weiberth KF, Mackie TD, Cleveland-Rubeor HC, Bethel NP, Callenberg KM, Nakatsukasa K, Grabe M, Brodsky JL. Transmembrane helix hydrophobicity is an energetic barrier during the retrotranslocation of integral membrane ERAD substrates. Mol Biol Cell 2017; 28:2076-2090. [PMID: 28539401 PMCID: PMC5509421 DOI: 10.1091/mbc.e17-03-0184] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Revised: 05/12/2017] [Accepted: 05/16/2017] [Indexed: 12/25/2022] Open
Abstract
Integral membrane proteins fold inefficiently and are susceptible to turnover via the endoplasmic reticulum-associated degradation (ERAD) pathway. During ERAD, misfolded proteins are recognized by molecular chaperones, polyubiquitinated, and retrotranslocated to the cytoplasm for proteasomal degradation. Although many aspects of this pathway are defined, how transmembrane helices (TMHs) are removed from the membrane and into the cytoplasm before degradation is poorly understood. In this study, we asked whether the hydrophobic character of a TMH acts as an energetic barrier to retrotranslocation. To this end, we designed a dual-pass model ERAD substrate, Chimera A*, which contains the cytoplasmic misfolded domain from a characterized ERAD substrate, Sterile 6* (Ste6p*). We found that the degradation requirements for Chimera A* and Ste6p* are similar, but Chimera A* was retrotranslocated more efficiently than Ste6p* in an in vitro assay in which retrotranslocation can be quantified. We then constructed a series of Chimera A* variants containing synthetic TMHs with a range of ΔG values for membrane insertion. TMH hydrophobicity correlated inversely with retrotranslocation efficiency, and in all cases, retrotranslocation remained Cdc48p dependent. These findings provide insight into the energetic restrictions on the retrotranslocation reaction, as well as a new computational approach to predict retrotranslocation efficiency.
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Affiliation(s)
| | - Karl-Richard Reutter
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
| | - Andrew A Augustine
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
| | - G Michael Preston
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
| | - Kurt F Weiberth
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
| | - Timothy D Mackie
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
| | | | - Neville P Bethel
- Cardiovascular Research Institute, Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA 94158
| | - Keith M Callenberg
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
| | - Kunio Nakatsukasa
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260.,Division of Biological Science, Graduate School of Natural Sciences, Nagoya City University, Nagoya, Aichi 467-8501, Japan
| | - Michael Grabe
- Cardiovascular Research Institute, Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA 94158
| | - Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
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46
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Mouse Mammary Tumor Virus Signal Peptide Uses a Novel p97-Dependent and Derlin-Independent Retrotranslocation Mechanism To Escape Proteasomal Degradation. mBio 2017; 8:mBio.00328-17. [PMID: 28351922 PMCID: PMC5371415 DOI: 10.1128/mbio.00328-17] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Multiple pathogens, including viruses and bacteria, manipulate endoplasmic reticulum-associated degradation (ERAD) to avoid the host immune response and promote their replication. The betaretrovirus mouse mammary tumor virus (MMTV) encodes Rem, which is a precursor protein that is cleaved into a 98-amino-acid signal peptide (SP) and a C-terminal protein (Rem-CT). SP uses retrotranslocation for ER membrane extraction and yet avoids ERAD by an unknown mechanism to enter the nucleus and function as a Rev-like protein. To determine how SP escapes ERAD, we used a ubiquitin-activated interaction trap (UBAIT) screen to trap and identify transient protein interactions with SP, including the ERAD-associated p97 ATPase, but not E3 ligases or Derlin proteins linked to retrotranslocation, polyubiquitylation, and proteasomal degradation of extracted proteins. A dominant negative p97 ATPase inhibited both Rem and SP function. Immunoprecipitation experiments indicated that Rem, but not SP, is polyubiquitylated. Using both yeast and mammalian expression systems, linkage of a ubiquitin-like domain (UbL) to SP or Rem induced degradation by the proteasome, whereas SP was stable in the absence of the UbL. ERAD-associated Derlin proteins were not required for SP activity. Together, these results suggested that Rem uses a novel p97-dependent, Derlin-independent retrotranslocation mechanism distinct from other pathogens to avoid SP ubiquitylation and proteasomal degradation. Bacterial and viral infections produce pathogen-specific proteins that interfere with host functions, including the immune response. Mouse mammary tumor virus (MMTV) is a model system for studies of human complex retroviruses, such as HIV-1, as well as cancer induction. We have shown that MMTV encodes a regulatory protein, Rem, which is cleaved into an N-terminal signal peptide (SP) and a C-terminal protein (Rem-CT) within the endoplasmic reticulum (ER) membrane. SP function requires ER membrane extraction by retrotranslocation, which is part of a protein quality control system known as ER-associated degradation (ERAD) that is essential to cellular health. Through poorly understood mechanisms, certain pathogen-derived proteins are retrotranslocated but not degraded. We demonstrate here that MMTV SP retrotranslocation from the ER membrane avoids degradation through a unique process involving interaction with cellular p97 ATPase and failure to acquire cellular proteasome-targeting sequences.
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47
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Neal S, Mak R, Bennett EJ, Hampton R. A Cdc48 "Retrochaperone" Function Is Required for the Solubility of Retrotranslocated, Integral Membrane Endoplasmic Reticulum-associated Degradation (ERAD-M) Substrates. J Biol Chem 2017; 292:3112-3128. [PMID: 28077573 DOI: 10.1074/jbc.m116.770610] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Revised: 01/10/2017] [Indexed: 12/22/2022] Open
Abstract
A surprising feature of endoplasmic reticulum (ER)-associated degradation (ERAD) is the movement, or retrotranslocation, of ubiquitinated substrates from the ER lumen or membrane to the cytosol where they are degraded by the 26S proteasome. Multispanning ER membrane proteins, called ERAD-M substrates, are retrotranslocated to the cytosol as full-length intermediates during ERAD, and we have investigated how they maintain substrate solubility. Using an in vivo assay, we show that retrotranslocated ERAD-M substrates are moved to the cytoplasm as part of the normal ERAD pathway, where they are part of a solely proteinaceous complex. Using proteomics and direct biochemical confirmation, we found that Cdc48 serves as a critical "retrochaperone" for these ERAD-M substrates. Cdc48 binding to retrotranslocated, ubiquitinated ERAD-M substrates is required for their solubility; removal of the polyubiquitin chains or competition for binding by addition of free polyubiquitin liberated Cdc48 from retrotranslocated proteins and rendered them insoluble. All components of the canonical Cdc48 complex Cdc48-Npl4-Ufd1 were present in solubilized ERAD-M substrates. This function of the complex was observed for both HRD and DOA pathway substrates. Thus, in addition to the long known ATP-dependent extraction of ERAD substrates during retrotranslocation, the Cdc48 complex is generally and critically needed for the solubility of retrotranslocated ERAD-M intermediates.
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Affiliation(s)
- Sonya Neal
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, California 92093
| | - Raymond Mak
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, California 92093
| | - Eric J Bennett
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, California 92093
| | - Randolph Hampton
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, California 92093.
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48
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Hantouche C, Williamson B, Valinsky WC, Solomon J, Shrier A, Young JC. Bag1 Co-chaperone Promotes TRC8 E3 Ligase-dependent Degradation of Misfolded Human Ether a Go-Go-related Gene (hERG) Potassium Channels. J Biol Chem 2016; 292:2287-2300. [PMID: 27998983 DOI: 10.1074/jbc.m116.752618] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Revised: 12/02/2016] [Indexed: 11/06/2022] Open
Abstract
Cardiac long QT syndrome type 2 is caused by mutations in the human ether a go-go-related gene (hERG) potassium channel, many of which cause misfolding and degradation at the endoplasmic reticulum instead of normal trafficking to the cell surface. The Hsc70/Hsp70 chaperones assist the folding of the hERG cytosolic domains. Here, we demonstrate that the Hsp70 nucleotide exchange factor Bag1 promotes hERG degradation by the ubiquitin-proteasome system at the endoplasmic reticulum to regulate hERG levels and channel activity. Dissociation of hERG complexes containing Hsp70 and the E3 ubiquitin ligase CHIP requires the interaction of Bag1 with Hsp70, but this does not involve the Bag1 ubiquitin-like domain. The interaction with Bag1 then shifts hERG degradation to the membrane-anchored E3 ligase TRC8 and its E2-conjugating enzyme Ube2g2, as determined by siRNA screening. TRC8 interacts through the transmembrane region with hERG and decreases hERG functional expression. TRC8 also mediates degradation of the misfolded hERG-G601S disease mutant, but pharmacological stabilization of the mutant structure prevents degradation. Our results identify TRC8 as a previously unknown Hsp70-independent quality control E3 ligase for hERG.
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Affiliation(s)
- Christine Hantouche
- From the Departments of Physiology and.,Groupe de Recherche Axé sur la Structure des Protéines, McGill University, Montreal, Quebec H3G 0B1, Canada
| | - Brittany Williamson
- Biochemistry and.,Groupe de Recherche Axé sur la Structure des Protéines, McGill University, Montreal, Quebec H3G 0B1, Canada
| | - William C Valinsky
- From the Departments of Physiology and.,Groupe de Recherche Axé sur la Structure des Protéines, McGill University, Montreal, Quebec H3G 0B1, Canada
| | - Joshua Solomon
- From the Departments of Physiology and.,Groupe de Recherche Axé sur la Structure des Protéines, McGill University, Montreal, Quebec H3G 0B1, Canada
| | - Alvin Shrier
- From the Departments of Physiology and .,Groupe de Recherche Axé sur la Structure des Protéines, McGill University, Montreal, Quebec H3G 0B1, Canada
| | - Jason C Young
- Biochemistry and .,Groupe de Recherche Axé sur la Structure des Protéines, McGill University, Montreal, Quebec H3G 0B1, Canada
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49
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Nilse L, Avci D, Heisterkamp P, Serang O, Lemberg MK, Schilling O. Yeast membrane proteomics using leucine metabolic labelling: Bioinformatic data processing and exemplary application to the ER-intramembrane protease Ypf1. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2016; 1864:1363-71. [PMID: 27426920 DOI: 10.1016/j.bbapap.2016.07.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Revised: 06/27/2016] [Accepted: 07/12/2016] [Indexed: 10/21/2022]
Abstract
We describe in detail the usage of leucine metabolic labelling in yeast in order to monitor quantitative proteome alterations, e.g. upon removal of a protease. Since laboratory yeast strains are typically leucine auxotroph, metabolic labelling with trideuterated leucine (d3-leucine) is a straightforward, cost-effective, and ubiquitously applicable strategy for quantitative proteomic studies, similar to the widely used arginine/lysine metabolic labelling method for mammalian cells. We showcase the usage of advanced peptide quantification using the FeatureFinderMultiplex algorithm (part of the OpenMS software package) for robust and reliable quantification. Furthermore, we present an OpenMS bioinformatics data analysis workflow that combines accurate quantification with high proteome coverage. In order to enable visualization, peptide-mapping, and sharing of quantitative proteomic data, especially for membrane-spanning and cell-surface proteins, we further developed the web-application Proteator (http://proteator.appspot.com). Due to its simplicity and robustness, we expect metabolic leucine labelling in yeast to be of great interest to the research community. As an exemplary application, we show the identification of the copper transporter Ctr1 as a putative substrate of the ER-intramembrane protease Ypf1 by yeast membrane proteomics using d3-leucine isotopic labelling.
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Affiliation(s)
- Lars Nilse
- Institute of Molecular Medicine and Cell Research, University of Freiburg, D-79104 Freiburg, Germany
| | - Dönem Avci
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), DKFZ-ZMBH Allianz, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany
| | - Patrick Heisterkamp
- Institute of Molecular Medicine and Cell Research, University of Freiburg, D-79104 Freiburg, Germany
| | - Oliver Serang
- Freie Universität Berlin, Department of Informatik, Takustr. 9, 14195 Berlin, Germany; Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Müggelsee 310, 12587 Berlin, Germany
| | - Marius K Lemberg
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), DKFZ-ZMBH Allianz, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany.
| | - Oliver Schilling
- Institute of Molecular Medicine and Cell Research, University of Freiburg, D-79104 Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, University of Freiburg, D-79104 Freiburg, Germany.
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50
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Tiengwe C, Muratore KA, Bangs JD. Surface proteins, ERAD and antigenic variation in Trypanosoma brucei. Cell Microbiol 2016; 18:1673-1688. [PMID: 27110662 DOI: 10.1111/cmi.12605] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Revised: 03/20/2016] [Accepted: 04/12/2016] [Indexed: 12/11/2022]
Abstract
Variant surface glycoprotein (VSG) is central to antigenic variation in African trypanosomes. Although much prior work documents that VSG is efficiently synthesized and exported to the cell surface, it was recently claimed that 2-3 fold more is synthesized than required, the excess being eliminated by ER-Associated Degradation (ERAD) (Field et al., ). We now reinvestigate VSG turnover and find no evidence for rapid degradation, consistent with a model whereby VSG synthesis is precisely regulated to match requirements for a functional surface coat on each daughter cell. However, using a mutated version of the ESAG7 subunit of the transferrin receptor (E7:Ty) we confirm functional ERAD in trypanosomes. E7:Ty fails to assemble into transferrin receptors and accumulates in the ER, consistent with retention of misfolded protein, and its turnover is selectively rescued by the proteasomal inhibitor MG132. We also show that ER accumulation of E7:Ty does not induce an unfolded protein response. These data, along with the presence of ERAD orthologues in the Trypanosoma brucei genome, confirm ERAD in trypanosomes. We discuss scenarios in which ERAD could be critical to bloodstream parasites, and how these may have contributed to the evolution of antigenic variation in trypanosomes.
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Affiliation(s)
- Calvin Tiengwe
- Department of Microbiology and Immunology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo (SUNY), Buffalo, NY, 14214, USA
| | - Katherine A Muratore
- Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis-St. Paul, MN, 55455, USA
| | - James D Bangs
- Department of Microbiology and Immunology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo (SUNY), Buffalo, NY, 14214, USA.
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