1
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Thalén NB, Barzadd MM, Lundqvist M, Rodhe J, Andersson M, Bidkhori G, Possner D, Su C, Nilsson J, Eisenhut P, Malm M, Karlsson A, Vestin J, Forsberg J, Nordling E, Mardinoglu A, Volk AL, Sandegren A, Rockberg J. Tuning of CHO secretional machinery improve activity of secreted therapeutic sulfatase 150-fold. Metab Eng 2024; 81:157-166. [PMID: 38081506 DOI: 10.1016/j.ymben.2023.12.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2022] [Revised: 10/12/2023] [Accepted: 12/01/2023] [Indexed: 12/18/2023]
Abstract
Rare diseases are, despite their name, collectively common and millions of people are affected daily of conditions where treatment often is unavailable. Sulfatases are a large family of activating enzymes related to several of these diseases. Heritable genetic variations in sulfatases may lead to impaired activity and a reduced macromolecular breakdown within the lysosome, with several severe and lethal conditions as a consequence. While therapeutic options are scarce, treatment for some sulfatase deficiencies by recombinant enzyme replacement are available. The recombinant production of such sulfatases suffers greatly from both low product activity and yield, further limiting accessibility for patient groups. To mitigate the low product activity, we have investigated cellular properties through computational evaluation of cultures with varying media conditions and comparison of two CHO clones with different levels of one active sulfatase variant. Transcriptome analysis identified 18 genes in secretory pathways correlating with increased sulfatase production. Experimental validation by upregulation of a set of three key genes improved the specific enzymatic activity at varying degree up to 150-fold in another sulfatase variant, broadcasting general production benefits. We also identified a correlation between product mRNA levels and sulfatase activity that generated an increase in sulfatase activity when expressed with a weaker promoter. Furthermore, we suggest that our proposed workflow for resolving bottlenecks in cellular machineries, to be useful for improvements of cell factories for other biologics as well.
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Affiliation(s)
- Niklas Berndt Thalén
- Dept. of Protein science, KTH - Royal Institute of Technology, Stockholm, SE-106 91, Sweden
| | - Mona Moradi Barzadd
- Dept. of Protein science, KTH - Royal Institute of Technology, Stockholm, SE-106 91, Sweden
| | - Magnus Lundqvist
- Dept. of Protein science, KTH - Royal Institute of Technology, Stockholm, SE-106 91, Sweden
| | | | | | - Gholamreza Bidkhori
- Science for Life Laboratory, KTH - Royal Institute of Technology, Solna, 171 65, Sweden; AIVIVO Ltd. Unit 25, Bio-innovation centre, Cambridge Science park, Cambridge, UK
| | | | - Chao Su
- SOBI AB, Tomtebodavägen 23A, Stockholm, Sweden
| | | | - Peter Eisenhut
- ACIB - Austrian Centre of Industrial Biotechnology, Krenngasse 37, 8010 Graz, Austria; BOKU - University of Natural Resources and Life Sciences, Department of Biotechnology, Vienna, 1190, Austria
| | - Magdalena Malm
- Dept. of Protein science, KTH - Royal Institute of Technology, Stockholm, SE-106 91, Sweden
| | - Alice Karlsson
- Dept. of Protein science, KTH - Royal Institute of Technology, Stockholm, SE-106 91, Sweden
| | | | | | | | - Adil Mardinoglu
- Science for Life Laboratory, KTH - Royal Institute of Technology, Solna, 171 65, Sweden
| | - Anna-Luisa Volk
- Dept. of Protein science, KTH - Royal Institute of Technology, Stockholm, SE-106 91, Sweden
| | | | - Johan Rockberg
- Dept. of Protein science, KTH - Royal Institute of Technology, Stockholm, SE-106 91, Sweden.
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2
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McKenna MJ, Shao S. The Endoplasmic Reticulum and the Fidelity of Nascent Protein Localization. Cold Spring Harb Perspect Biol 2023; 15:a041249. [PMID: 36041782 PMCID: PMC9979852 DOI: 10.1101/cshperspect.a041249] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
High-fidelity protein localization is essential to define the identities and functions of different organelles and to maintain cellular homeostasis. Accurate localization of nascent proteins requires specific protein targeting pathways as well as quality control (QC) mechanisms to remove mislocalized proteins. The endoplasmic reticulum (ER) is the first destination for approximately one-third of the eukaryotic proteome and a major site of protein biosynthesis and QC. In mammalian cells, trafficking from the ER provides nascent proteins access to the extracellular space and essentially every cellular membrane and organelle except for mitochondria and possibly peroxisomes. Here, we discuss the biosynthetic mechanisms that deliver nascent proteins to the ER and the QC mechanisms that interface with the ER to correct or degrade mislocalized proteins.
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Affiliation(s)
- Michael J McKenna
- Department of Cell Biology, Harvard Medical School, Blavatnik Institute, Boston, Massachusetts 02115, USA
| | - Sichen Shao
- Department of Cell Biology, Harvard Medical School, Blavatnik Institute, Boston, Massachusetts 02115, USA
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3
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Sec61 channel subunit Sbh1/Sec61β promotes ER translocation of proteins with suboptimal targeting sequences and is fine-tuned by phosphorylation. J Biol Chem 2023; 299:102895. [PMID: 36639027 PMCID: PMC9947333 DOI: 10.1016/j.jbc.2023.102895] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Revised: 12/07/2022] [Accepted: 12/09/2022] [Indexed: 01/12/2023] Open
Abstract
The highly conserved endoplasmic reticulum (ER) protein translocation channel contains one nonessential subunit, Sec61β/Sbh1, whose function is poorly understood so far. Its intrinsically unstructured cytosolic domain makes transient contact with ER-targeting sequences in the cytosolic channel vestibule and contains multiple phosphorylation sites suggesting a potential for regulating ER protein import. In a microscopic screen, we show that 12% of a GFP-tagged secretory protein library depends on Sbh1 for translocation into the ER. Sbh1-dependent proteins had targeting sequences with less pronounced hydrophobicity and often no charge bias or an inverse charge bias which reduces their insertion efficiency into the Sec61 channel. We determined that mutating two N-terminal, proline-flanked phosphorylation sites in the Sbh1 cytosolic domain to alanine phenocopied the temperature-sensitivity of a yeast strain lacking SBH1 and its ortholog SBH2. The phosphorylation site mutations reduced translocation into the ER of a subset of Sbh1-dependent proteins, including enzymes whose concentration in the ER lumen is critical for ER proteostasis. In addition, we found that ER import of these proteins depended on the activity of the phospho-S/T-specific proline isomerase Ess1 (PIN1 in mammals). We conclude that Sbh1 promotes ER translocation of substrates with suboptimal targeting sequences and that its activity can be regulated by a conformational change induced by N-terminal phosphorylation.
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4
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Linders PTA, Ioannidis M, ter Beest M, van den Bogaart G. Fluorescence Lifetime Imaging of pH along the Secretory Pathway. ACS Chem Biol 2022; 17:240-251. [PMID: 35000377 PMCID: PMC8787756 DOI: 10.1021/acschembio.1c00907] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
![]()
Many cellular processes
are dependent on correct pH levels, and
this is especially important for the secretory pathway. Defects in
pH homeostasis in distinct organelles cause a wide range of diseases,
including disorders of glycosylation and lysosomal storage diseases.
Ratiometric imaging of the pH-sensitive mutant of green fluorescent
protein, pHLuorin, has allowed for targeted pH measurements in various
organelles, but the required sequential image acquisition is intrinsically
slow and therefore the temporal resolution is unsuitable to follow
the rapid transit of cargo between organelles. Therefore, we applied
fluorescence lifetime imaging microscopy (FLIM) to measure intraorganellar
pH with just a single excitation wavelength. We first validated this
method by confirming the pH in multiple compartments along the secretory
pathway and compared the pH values obtained by the FLIM-based measurements
with those obtained by conventional ratiometric imaging. Then, we
analyzed the dynamic pH changes within cells treated with Bafilomycin
A1, to block the vesicular ATPase, and Brefeldin A, to block endoplasmic
reticulum (ER)–Golgi trafficking. Finally, we followed the
pH changes of newly synthesized molecules of the inflammatory cytokine
tumor necrosis factor-α while they were in transit from the
ER via the Golgi to the plasma membrane. The toolbox we present here
can be applied to measure intracellular pH with high spatial and temporal
resolution and can be used to assess organellar pH in disease models.
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Affiliation(s)
- Peter T. A. Linders
- Department of Tumor Immunology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Melina Ioannidis
- Department of Molecular Immunology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9747AG Groningen, Netherlands
| | - Martin ter Beest
- Department of Tumor Immunology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Geert van den Bogaart
- Department of Tumor Immunology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
- Department of Molecular Immunology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9747AG Groningen, Netherlands
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5
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Guan L, Yang Y, Liang JJ, Miao Y, Shang AY, Wang B, Wang YC, Ding M. ERGIC2 and ERGIC3 regulate the ER-to-Golgi transport of gap junction proteins in metazoans. Traffic 2022; 23:140-157. [PMID: 34994051 DOI: 10.1111/tra.12830] [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: 08/16/2021] [Revised: 12/16/2021] [Accepted: 01/04/2022] [Indexed: 11/26/2022]
Abstract
The extremely dynamic life cycle of gap junction connections requires highly efficient intracellular trafficking system especially designed for gap junction proteins, but the underlying mechanisms are largely unknown. Here, we identified that the COPII-associated proteins ERGIC2 (ER-Golgi intermediate compartment) and ERGIC3 are specifically required for the efficient intracellular transport of gap junction proteins in both C. elegans and mice. In the absence of Ergic2 or Ergic3, gap junction proteins accumulate in the ER and Golgi apparatus and the size of endogenous gap junction plaques is reduced. Knocking out the Ergic2 or Ergic3 in mice results in heart enlargement and cardiac malfunction accompanied by reduced number and size of connexin 43 (Cx43) gap junctions. Invertebrates' gap junction protein innexins share no sequence similarity with vertebrates' connexins. However, ERGIC2 and ERGIC3 could bind to gap junction proteins in both worms and mice. Characterization of the highly specialized roles of ERGIC2 and ERGIC3 in metazoans reveals how the early secretory pathway could be adapted to facilitate the efficient transport for gap junction proteins in vivo. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Liying Guan
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Yongzhi Yang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Jing Jing Liang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Yue Miao
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Ang Yang Shang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Baolei Wang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Ying Chun Wang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Mei Ding
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
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6
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Sun Z, Guerriero CJ, Brodsky JL. Substrate ubiquitination retains misfolded membrane proteins in the endoplasmic reticulum for degradation. Cell Rep 2021; 36:109717. [PMID: 34551305 PMCID: PMC8503845 DOI: 10.1016/j.celrep.2021.109717] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 06/11/2021] [Accepted: 08/25/2021] [Indexed: 11/28/2022] Open
Abstract
To maintain secretory pathway fidelity, misfolded proteins are commonly retained in the endoplasmic reticulum (ER) and selected for ER-associated degradation (ERAD). Soluble misfolded proteins use ER chaperones for retention, but the machinery that restricts aberrant membrane proteins to the ER is unclear. In fact, some misfolded membrane proteins escape the ER and traffic to the lysosome/vacuole. To this end, we describe a model substrate, SZ*, that contains an ER export signal but is also targeted for ERAD. We observe decreased ER retention when chaperone-dependent SZ* ubiquitination is compromised. In addition, appending a linear tetra-ubiquitin motif onto SZ* overrides ER export. By screening known ubiquitin-binding proteins, we then positively correlate SZ* retention with Ubx2 binding. Deletion of Ubx2 also inhibits the retention of another misfolded membrane protein. Our results indicate that polyubiquitination is sufficient to retain misfolded membrane proteins in the ER prior to ERAD. Sun et al. characterize how misfolded membrane proteins are delivered for either ERAD or post-ER degradation in the secretory pathway. By using a model substrate that can access both pathways, they show that substrate retention requires chaperone-dependent substrate ubiquitination and interaction with a conserved ER membrane protein, Ubx2.
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Affiliation(s)
- Zhihao Sun
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | | | - Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA.
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7
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Claeys L, Storoni S, Eekhoff M, Elting M, Wisse L, Pals G, Bravenboer N, Maugeri A, Micha D. Collagen transport and related pathways in Osteogenesis Imperfecta. Hum Genet 2021; 140:1121-1141. [PMID: 34169326 PMCID: PMC8263409 DOI: 10.1007/s00439-021-02302-2] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Accepted: 06/08/2021] [Indexed: 12/16/2022]
Abstract
Osteogenesis Imperfecta (OI) comprises a heterogeneous group of patients who share bone fragility and deformities as the main characteristics, albeit with different degrees of severity. Phenotypic variation also exists in other connective tissue aspects of the disease, complicating disease classification and disease course prediction. Although collagen type I defects are long established as the primary cause of the bone pathology, we are still far from comprehending the complete mechanism. In the last years, the advent of next generation sequencing has triggered the discovery of many new genetic causes for OI, helping to draw its molecular landscape. It has become clear that, in addition to collagen type I genes, OI can be caused by multiple proteins connected to different parts of collagen biosynthesis. The production of collagen entails a complex process, starting from the production of the collagen Iα1 and collagen Iα2 chains in the endoplasmic reticulum, during and after which procollagen is subjected to a plethora of posttranslational modifications by chaperones. After reaching the Golgi organelle, procollagen is destined to the extracellular matrix where it forms collagen fibrils. Recently discovered mutations in components of the retrograde transport of chaperones highlight its emerging role as critical contributor of OI development. This review offers an overview of collagen regulation in the context of recent gene discoveries, emphasizing the significance of transport disruptions in the OI mechanism. We aim to motivate exploration of skeletal fragility in OI from the perspective of these pathways to identify regulatory points which can hint to therapeutic targets.
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Affiliation(s)
- Lauria Claeys
- Department of Clinical Genetics, Amsterdam UMC, Amsterdam Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Silvia Storoni
- Department of Internal Medicine Section Endocrinology, Amsterdam UMC, Amsterdam Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Marelise Eekhoff
- Department of Internal Medicine Section Endocrinology, Amsterdam UMC, Amsterdam Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Mariet Elting
- Department of Clinical Genetics, Amsterdam UMC, Amsterdam Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Lisanne Wisse
- Department of Clinical Genetics, Amsterdam UMC, Amsterdam Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Gerard Pals
- Department of Clinical Genetics, Amsterdam UMC, Amsterdam Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Nathalie Bravenboer
- Department of Clinical Chemistry, Amsterdam /UMC, Amsterdam Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Alessandra Maugeri
- Department of Clinical Genetics, Amsterdam UMC, Amsterdam Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Dimitra Micha
- Department of Clinical Genetics, Amsterdam UMC, Amsterdam Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.
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8
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A virtuous cycle operated by ERp44 and ERGIC-53 guarantees proteostasis in the early secretory compartment. iScience 2021; 24:102244. [PMID: 33763635 PMCID: PMC7973864 DOI: 10.1016/j.isci.2021.102244] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Revised: 02/01/2021] [Accepted: 02/25/2021] [Indexed: 01/13/2023] Open
Abstract
The composition of the secretome depends on the combined action of cargo receptors that facilitate protein transport and sequential checkpoints that restrict it to native conformers. Acting after endoplasmic reticulum (ER)-resident chaperones, ERp44 retrieves its clients from downstream compartments. To guarantee efficient quality control, ERp44 should exit the ER as rapidly as its clients, or more. Here, we show that appending ERp44 to different cargo proteins increases their secretion rates. ERp44 binds the cargo receptor ER-Golgi intermediate compartment (ERGIC)-53 in the ER to negotiate preferential loading into COPII vesicles. Silencing ERGIC-53, or competing for its COPII binding with 4-phenylbutyrate, causes secretion of Prdx4, an enzyme that relies on ERp44 for intracellular localization. In more acidic, zinc-rich downstream compartments, ERGIC-53 releases its clients and ERp44, which can bind and retrieve non-native conformers via KDEL receptors. By coupling the transport of cargoes and inspector proteins, cells ensure efficiency and fidelity of secretion.
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9
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Tempio T, Anelli T. The pivotal role of ERp44 in patrolling protein secretion. J Cell Sci 2020; 133:133/21/jcs240366. [PMID: 33173013 DOI: 10.1242/jcs.240366] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Interactions between protein ligands and receptors are the main language of intercellular communication; hence, how cells select proteins to be secreted or presented on the plasma membrane is a central concern in cell biology. A series of checkpoints are located along the secretory pathway, which ensure the fidelity of such protein signals (quality control). Proteins that pass the checkpoints operated in the endoplasmic reticulum (ER) by the binding immunoglobulin protein (BiP; also known as HSPA5 and GRP78) and the calnexin-calreticulin systems, must still overcome additional scrutiny in the ER-Golgi intermediate compartment (ERGIC) and the Golgi. One of the main players of this process in all metazoans is the ER-resident protein 44 (ERp44); by cycling between the ER and the Golgi, ERp44 controls the localization of key enzymes designed to act in the ER but that are devoid of suitable localization motifs. ERp44 also patrols the secretion of correctly assembled disulfide-linked oligomeric proteins. Here, we discuss the mechanisms driving ERp44 substrate recognition, with important consequences on the definition of 'thiol-mediated quality control'. We also describe how pH and zinc gradients regulate the functional cycle of ERp44, coupling quality control and membrane trafficking along the early secretory compartment.
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Affiliation(s)
- Tiziana Tempio
- Division of Genetics and Cell Biology, Vita-Salute San Raffaele University, Milan 20132, Italy.,IRCCS San Raffaele Scientific Institute, Milan 20132, Italy
| | - Tiziana Anelli
- Division of Genetics and Cell Biology, Vita-Salute San Raffaele University, Milan 20132, Italy .,IRCCS San Raffaele Scientific Institute, Milan 20132, Italy
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10
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Scarpin MR, Leiboff S, Brunkard JO. Parallel global profiling of plant TOR dynamics reveals a conserved role for LARP1 in translation. eLife 2020; 9:e58795. [PMID: 33054972 PMCID: PMC7584452 DOI: 10.7554/elife.58795] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Accepted: 10/14/2020] [Indexed: 12/15/2022] Open
Abstract
Target of rapamycin (TOR) is a protein kinase that coordinates eukaryotic metabolism. In mammals, TOR specifically promotes translation of ribosomal protein (RP) mRNAs when amino acids are available to support protein synthesis. The mechanisms controlling translation downstream from TOR remain contested, however, and are largely unexplored in plants. To define these mechanisms in plants, we globally profiled the plant TOR-regulated transcriptome, translatome, proteome, and phosphoproteome. We found that TOR regulates ribosome biogenesis in plants at multiple levels, but through mechanisms that do not directly depend on 5' oligopyrimidine tract motifs (5'TOPs) found in mammalian RP mRNAs. We then show that the TOR-LARP1-5'TOP signaling axis is conserved in plants and regulates expression of a core set of eukaryotic 5'TOP mRNAs, as well as new, plant-specific 5'TOP mRNAs. Our study illuminates ancestral roles of the TOR-LARP1-5'TOP metabolic regulatory network and provides evolutionary context for ongoing debates about the molecular function of LARP1.
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Affiliation(s)
- M Regina Scarpin
- Department of Plant and Microbial Biology, University of California at BerkeleyBerkeleyUnited States
- Plant Gene Expression Center, U.S. Department of Agriculture Agricultural Research ServiceAlbanyUnited States
| | - Samuel Leiboff
- Department of Plant and Microbial Biology, University of California at BerkeleyBerkeleyUnited States
- Plant Gene Expression Center, U.S. Department of Agriculture Agricultural Research ServiceAlbanyUnited States
- Department of Botany and Plant Pathology, Oregon State UniversityCorvallisUnited States
| | - Jacob O Brunkard
- Department of Plant and Microbial Biology, University of California at BerkeleyBerkeleyUnited States
- Plant Gene Expression Center, U.S. Department of Agriculture Agricultural Research ServiceAlbanyUnited States
- Laboratory of Genetics, University of Wisconsin—MadisonMadisonUnited States
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11
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Lopez S, Perez-Linero AM, Manzano-Lopez J, Sabido-Bozo S, Cortes-Gomez A, Rodriguez-Gallardo S, Aguilera-Romero A, Goder V, Muñiz M. Dual Independent Roles of the p24 Complex in Selectivity of Secretory Cargo Export from the Endoplasmic Reticulum. Cells 2020; 9:cells9051295. [PMID: 32456004 PMCID: PMC7291304 DOI: 10.3390/cells9051295] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 05/18/2020] [Accepted: 05/20/2020] [Indexed: 11/22/2022] Open
Abstract
The cellular mechanisms that ensure the selectivity and fidelity of secretory cargo protein transport from the endoplasmic reticulum (ER) to the Golgi are still not well understood. The p24 protein complex acts as a specific cargo receptor for GPI-anchored proteins by facilitating their ER exit through a specialized export pathway in yeast. In parallel, the p24 complex can also exit the ER using the general pathway that exports the rest of secretory proteins with their respective cargo receptors. Here, we show biochemically that the p24 complex associates at the ER with other cargo receptors in a COPII-dependent manner, forming high-molecular weight multireceptor complexes. Furthermore, live cell imaging analysis reveals that the p24 complex is required to retain in the ER secretory cargos when their specific receptors are absent. This requirement does not involve neither the unfolded protein response nor the retrograde transport from the Golgi. Our results suggest that, in addition to its role as a cargo receptor in the specialized GPI-anchored protein pathway, the p24 complex also plays an independent role in secretory cargo selectivity during its exit through the general ER export pathway, preventing the non-selective bulk flow of native secretory cargos. This mechanism would ensure receptor-regulated cargo transport, providing an additional layer of regulation of secretory cargo selectivity during ER export.
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Affiliation(s)
- Sergio Lopez
- Department of Cell Biology, University of Seville, 41012 Seville, Spain; (S.L.); (A.M.P.-L.); (J.M.-L.); (S.S.-B.); (A.C.-G.); (S.R.-G.); (A.A.-R.)
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, 41012 Seville, Spain
| | - Ana Maria Perez-Linero
- Department of Cell Biology, University of Seville, 41012 Seville, Spain; (S.L.); (A.M.P.-L.); (J.M.-L.); (S.S.-B.); (A.C.-G.); (S.R.-G.); (A.A.-R.)
| | - Javier Manzano-Lopez
- Department of Cell Biology, University of Seville, 41012 Seville, Spain; (S.L.); (A.M.P.-L.); (J.M.-L.); (S.S.-B.); (A.C.-G.); (S.R.-G.); (A.A.-R.)
| | - Susana Sabido-Bozo
- Department of Cell Biology, University of Seville, 41012 Seville, Spain; (S.L.); (A.M.P.-L.); (J.M.-L.); (S.S.-B.); (A.C.-G.); (S.R.-G.); (A.A.-R.)
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, 41012 Seville, Spain
| | - Alejandro Cortes-Gomez
- Department of Cell Biology, University of Seville, 41012 Seville, Spain; (S.L.); (A.M.P.-L.); (J.M.-L.); (S.S.-B.); (A.C.-G.); (S.R.-G.); (A.A.-R.)
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, 41012 Seville, Spain
| | - Sofia Rodriguez-Gallardo
- Department of Cell Biology, University of Seville, 41012 Seville, Spain; (S.L.); (A.M.P.-L.); (J.M.-L.); (S.S.-B.); (A.C.-G.); (S.R.-G.); (A.A.-R.)
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, 41012 Seville, Spain
| | - Auxiliadora Aguilera-Romero
- Department of Cell Biology, University of Seville, 41012 Seville, Spain; (S.L.); (A.M.P.-L.); (J.M.-L.); (S.S.-B.); (A.C.-G.); (S.R.-G.); (A.A.-R.)
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, 41012 Seville, Spain
| | - Veit Goder
- Department of Genetics, University of Seville, 41012 Seville, Spain;
| | - Manuel Muñiz
- Department of Cell Biology, University of Seville, 41012 Seville, Spain; (S.L.); (A.M.P.-L.); (J.M.-L.); (S.S.-B.); (A.C.-G.); (S.R.-G.); (A.A.-R.)
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, 41012 Seville, Spain
- Correspondence: ; Tel.: +34-954556529
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12
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Keiser KJ, Barlowe C. Molecular dissection of the Erv41-Erv46 retrograde receptor reveals a conserved cysteine-rich region in Erv46 required for retrieval activity. Mol Biol Cell 2019; 31:209-220. [PMID: 31825724 PMCID: PMC7001479 DOI: 10.1091/mbc.e19-08-0484] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The Erv41-Erv46 complex is a conserved retrograde cargo receptor that retrieves ER resident proteins from Golgi compartments in a pH-dependent manner. Here we functionally dissect the Erv46 subunit and define an approximately 60 residue cysteine-rich region that is unique to the Erv46 family of proteins. This cysteine-rich region contains two vicinal cysteine pairs in CXXC and CCXXC configurations that are each required for retrieval activity in cells. Mutation of the individual cysteine residues produced stable Erv46 proteins that were partially reduced and form mixed-disulfide species on nonreducing gels. Conserved hydrophobic amino acids within the cysteine-rich region of Erv46 were also required for retrieval function in cells. In vitro binding experiments showed that this hydrophobic patch is required for direct cargo binding. Surprisingly, the Erv46 cysteine mutants continued to bind cargo in cell-free assays and produced an increased level of Erv46-cargo complexes in cell extracts suggesting that disulfide linkages in the cysteine-rich region perform a role in releasing bound cargo. On the basis of these findings, we propose that both pH and redox environments regulate cargo binding to a hydrophobic site within the cysteine-rich region of Erv46.
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Affiliation(s)
- Kristofer J Keiser
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH 03755
| | - Charles Barlowe
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH 03755
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13
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Arakel EC, Huranova M, Estrada AF, Rau EM, Spang A, Schwappach B. Dissection of GTPase-activating proteins reveals functional asymmetry in the COPI coat of budding yeast. J Cell Sci 2019; 132:jcs.232124. [PMID: 31331965 PMCID: PMC6737914 DOI: 10.1242/jcs.232124] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Accepted: 07/12/2019] [Indexed: 12/11/2022] Open
Abstract
The Arf GTPase controls formation of the COPI vesicle coat. Recent structural models of COPI revealed the positioning of two Arf1 molecules in contrasting molecular environments. Each of these pockets for Arf1 is expected to also accommodate an Arf GTPase-activating protein (ArfGAP). Structural evidence and protein interactions observed between isolated domains indirectly suggest that each niche preferentially recruits one of the two ArfGAPs known to affect COPI, i.e. Gcs1/ArfGAP1 and Glo3/ArfGAP2/3, although only partial structures are available. The functional role of the unique non-catalytic domain of either ArfGAP has not been integrated into the current COPI structural model. Here, we delineate key differences in the consequences of triggering GTP hydrolysis through the activity of one versus the other ArfGAP. We demonstrate that Glo3/ArfGAP2/3 specifically triggers Arf1 GTP hydrolysis impinging on the stability of the COPI coat. We show that the Snf1 kinase complex, the yeast homologue of AMP-activated protein kinase (AMPK), phosphorylates the region of Glo3 that is crucial for this effect and, thereby, regulates its function in the COPI-vesicle cycle. Our results revise the model of ArfGAP function in the molecular context of COPI. This article has an associated First Person interview with the first author of the paper. Highlighted Article: The regulatory domain of the COPI-associated ArfGAP Glo3 can stabilize the COPI coat. GTP hydrolysis is necessary to resolve the stabilised state. This mechanism is regulated by phosphorylation.
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Affiliation(s)
- Eric C Arakel
- Department of Molecular Biology, Universitätsmedizin Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
| | - Martina Huranova
- Growth and Development, Biozentrum, University of Basel, Klingelbergstrasse 50/70, 4056 Basel, Switzerland.,Laboratory of Adaptive Immunity, Institute of Molecular Genetics of the Czech Academy of Sciences, Videnska 1083, 142 20 Prague 4, Czech Republic
| | - Alejandro F Estrada
- Growth and Development, Biozentrum, University of Basel, Klingelbergstrasse 50/70, 4056 Basel, Switzerland
| | - E-Ming Rau
- Growth and Development, Biozentrum, University of Basel, Klingelbergstrasse 50/70, 4056 Basel, Switzerland
| | - Anne Spang
- Growth and Development, Biozentrum, University of Basel, Klingelbergstrasse 50/70, 4056 Basel, Switzerland
| | - Blanche Schwappach
- Department of Molecular Biology, Universitätsmedizin Göttingen, Humboldtallee 23, 37073 Göttingen, Germany .,Max-Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
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14
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Yoo W, Cho EB, Kim S, Yoon JB. The E3 ubiquitin ligase MARCH2 regulates ERGIC3-dependent trafficking of secretory proteins. J Biol Chem 2019; 294:10900-10912. [PMID: 31142615 DOI: 10.1074/jbc.ra119.007435] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2019] [Revised: 05/17/2019] [Indexed: 11/06/2022] Open
Abstract
The E3 ubiquitin ligase membrane-associated ring-CH-type finger 2 (MARCH2) is known to be involved in intracellular vesicular trafficking, but its role in the early secretory pathway between the endoplasmic reticulum (ER) and Golgi compartments is largely unknown. Human ER-Golgi intermediate compartment protein 2 (ERGIC2) and ERGIC3 are orthologs of Erv41 and Erv46 in yeast, proteins that form a heteromeric complex, cycle between the ER and Golgi, and function as cargo receptors in both anterograde and retrograde protein trafficking. Here, we report that MARCH2 directs ubiquitination and subsequent degradation of ERGIC3 and that MARCH2 depletion increases endogenous ERGIC3 levels. We provide evidence that the lysine residues at positions 6 and 8 of ERGIC3 are the major sites of MARCH2-mediated ubiquitination. Of note, MARCH2 did not significantly decrease the levels of an ERGIC3 variant with lysine-to-arginine substitutions at residues 6 and 8. We also show that ERGIC3 binds to itself or to ERGIC2, whereas ERGIC2 is unable to interact with itself. Our results indicate that α1-antitrypsin and haptoglobin are likely to be cargo proteins of ERGIC3. We further observed that α1-antitrypsin and haptoglobin specifically bind to ERGIC3 and that ERGIC3 depletion decreases their secretion. Moreover, MARCH2 reduced secretion of α1-antitrypsin and haptoglobin, and coexpression of the ubiquitination-resistant ERGIC3 variant largely restored their secretion, suggesting that MARCH2-mediated ERGIC3 ubiquitination is the major cause of the decrease in trafficking of ERGIC3-binding secretory proteins. Our findings provide detailed insights into the regulation of the early secretory pathway by MARCH2 and into ERGIC3 function.
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Affiliation(s)
- Wonjin Yoo
- Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul 03722, Korea and
| | - Eun-Bee Cho
- Department of Medical Lifesciences, Catholic University of Korea, Seoul 06591, Korea
| | - Sungjoo Kim
- Department of Medical Lifesciences, Catholic University of Korea, Seoul 06591, Korea
| | - Jong-Bok Yoon
- Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul 03722, Korea and.
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15
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Reifenrath M, Boles E. A superfolder variant of pH-sensitive pHluorin for in vivo pH measurements in the endoplasmic reticulum. Sci Rep 2018; 8:11985. [PMID: 30097598 PMCID: PMC6086885 DOI: 10.1038/s41598-018-30367-z] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Accepted: 07/27/2018] [Indexed: 11/09/2022] Open
Abstract
Many cellular processes are regulated via pH, and maintaining the pH of different organelles is crucial for cell survival. A pH-sensitive GFP variant, the so-called pHluorin, has proven to be a valuable tool to study the pH of the cytosol, mitochondria and other organelles in vivo. We found that the fluorescence intensity of Endoplasmic Reticulum (ER)-targeted pHluorin in the yeast Saccharomyces cerevisiae was very low and barely showed pH sensitivity, probably due to misfolding in the oxidative environment of the ER. We therefore developed a superfolder variant of pHluorin which enabled us to monitor pH changes in the ER and the cytosol of S. cerevisiae in vivo. The superfolder pHluorin variant is likely to be functional in cells of different organisms as well as in additional compartments that originate from the secretory pathway like the Golgi apparatus and pre-vacuolar compartments, and therefore has a broad range of possible future applications.
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Affiliation(s)
- Mara Reifenrath
- Institute of Molecular Biosciences, Faculty of Biological Sciences, Goethe University Frankfurt, Max-von-Laue Straße 9, 60438, Frankfurt am Main, Germany
| | - Eckhard Boles
- Institute of Molecular Biosciences, Faculty of Biological Sciences, Goethe University Frankfurt, Max-von-Laue Straße 9, 60438, Frankfurt am Main, Germany.
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16
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Sun Z, Brodsky JL. The degradation pathway of a model misfolded protein is determined by aggregation propensity. Mol Biol Cell 2018; 29:1422-1434. [PMID: 29688814 PMCID: PMC6014095 DOI: 10.1091/mbc.e18-02-0117] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Protein homeostasis in the secretory pathway is maintained by a hierarchy of quality control checkpoints, including endoplasmic reticulum–associated degradation (ERAD), which leads to the destruction of misfolded proteins in the ER, as well as post-ER proteolysis. Although most aberrant proteins are degraded by ERAD, some misfolded proteins escape the ER and are degraded instead by lysosomal/vacuolar proteases. To date, it remains unclear how misfolded membrane proteins are selected for these different fates. Here we designed a novel model substrate, SZ*, to investigate how substrate selection is mediated in yeast. We discovered that SZ* is degraded by both the proteasome and vacuolar proteases, the latter of which occurs after ER exit and requires the multivesicular body pathway. By interrogating how various conditions affect the fate of SZ*, we also discovered that heat-shock and substrate overexpression increase ERAD targeting. These conditions also increase substrate aggregation. We next found that aggregation of the membrane-free misfolded domain in SZ* is concentration dependent, and fusion of this misfolded domain to a post-ER quality control substrate instead targets the substrate for ERAD. Our data indicate that a misfolded membrane protein with a higher aggregation propensity is preferentially retained in the ER and targeted for ERAD.
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Affiliation(s)
- Zhihao Sun
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
| | - Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
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17
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Abstract
The coat protein complex I (COPI) allows the precise sorting of lipids and proteins between Golgi cisternae and retrieval from the Golgi to the ER. This essential role maintains the identity of the early secretory pathway and impinges on key cellular processes, such as protein quality control. In this Cell Science at a Glance and accompanying poster, we illustrate the different stages of COPI-coated vesicle formation and revisit decades of research in the context of recent advances in the elucidation of COPI coat structure. By calling attention to an array of questions that have remained unresolved, this review attempts to refocus the perspectives of the field.
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Affiliation(s)
- Eric C Arakel
- Department of Molecular Biology, Universitätsmedizin Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
| | - Blanche Schwappach
- Department of Molecular Biology, Universitätsmedizin Göttingen, Humboldtallee 23, 37073 Göttingen, Germany .,Max-Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
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18
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Starr TL, Gonçalves AP, Meshgin N, Glass NL. The major cellulases CBH-1 and CBH-2 of Neurospora crassa rely on distinct ER cargo adaptors for efficient ER-exit. Mol Microbiol 2017; 107:229-248. [PMID: 29131484 DOI: 10.1111/mmi.13879] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/10/2017] [Indexed: 12/17/2022]
Abstract
Filamentous fungi are native secretors of lignocellulolytic enzymes and are used as protein-producing factories in the industrial biotechnology sector. Despite the importance of these organisms in industry, relatively little is known about the filamentous fungal secretory pathway or how it might be manipulated for improved protein production. Here, we use Neurospora crassa as a model filamentous fungus to interrogate the requirements for trafficking of cellulase enzymes from the endoplasmic reticulum to the Golgi. We characterized the localization and interaction properties of the p24 and ERV-29 cargo adaptors, as well as their role in cellulase enzyme trafficking. We find that the two most abundantly secreted cellulases, CBH-1 and CBH-2, depend on distinct ER cargo adaptors for efficient exit from the ER. CBH-1 depends on the p24 proteins, whereas CBH-2 depends on the N. crassa homolog of yeast Erv29p. This study provides a first step in characterizing distinct trafficking pathways of lignocellulolytic enzymes in filamentous fungi.
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Affiliation(s)
- Trevor L Starr
- The Energy Biosciences Institute, The University of California, Berkeley, CA 94720, USA
| | - A Pedro Gonçalves
- The Energy Biosciences Institute, The University of California, Berkeley, CA 94720, USA.,Plant and Microbial Biology Department, The University of California, Berkeley, CA 94720, USA
| | - Neeka Meshgin
- The Energy Biosciences Institute, The University of California, Berkeley, CA 94720, USA
| | - N Louise Glass
- The Energy Biosciences Institute, The University of California, Berkeley, CA 94720, USA.,Plant and Microbial Biology Department, The University of California, Berkeley, CA 94720, USA.,Environmental Genomics and Systems Biology Division, The Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA
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19
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Geva Y, Crissman J, Arakel EC, Gómez-Navarro N, Chuartzman SG, Stahmer KR, Schwappach B, Miller EA, Schuldiner M. Two novel effectors of trafficking and maturation of the yeast plasma membrane H + -ATPase. Traffic 2017; 18:672-682. [PMID: 28727280 PMCID: PMC5607100 DOI: 10.1111/tra.12503] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Revised: 07/17/2017] [Accepted: 07/17/2017] [Indexed: 11/28/2022]
Abstract
The endoplasmic reticulum (ER) is the entry site of proteins into the endomembrane system. Proteins exit the ER via coat protein II (COPII) vesicles in a selective manner, mediated either by direct interaction with the COPII coat or aided by cargo receptors. Despite the fundamental role of such receptors in protein sorting, only a few have been identified. To further define the machinery that packages secretory cargo and targets proteins from the ER to Golgi membranes, we used multiple systematic approaches, which revealed 2 uncharacterized proteins that mediate the trafficking and maturation of Pma1, the essential yeast plasma membrane proton ATPase. Ydl121c (Exp1) is an ER protein that binds Pma1, is packaged into COPII vesicles, and whose deletion causes ER retention of Pma1. Ykl077w (Psg1) physically interacts with Exp1 and can be found in the Golgi and coat protein I (COPI) vesicles but does not directly bind Pma1. Loss of Psg1 causes enhanced degradation of Pma1 in the vacuole. Our findings suggest that Exp1 is a Pma1 cargo receptor and that Psg1 aids Pma1 maturation in the Golgi or affects its retrieval. More generally our work shows the utility of high content screens in the identification of novel trafficking components.
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Affiliation(s)
- Yosef Geva
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
| | - Jonathan Crissman
- Department of Biological Sciences, Columbia University, New York, NY
| | - Eric C Arakel
- Department of Molecular Biology, Universitätsmedizin Göttingen, Göttingen, Germany
| | | | - Silvia G Chuartzman
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
| | - Kyle R Stahmer
- Department of Biological Sciences, Columbia University, New York, NY
| | - Blanche Schwappach
- Department of Molecular Biology, Universitätsmedizin Göttingen, Göttingen, Germany
| | - Elizabeth A Miller
- Department of Biological Sciences, Columbia University, New York, NY.,MRC Laboratory of Molecular Biology, Cell Biology Division, Cambridge, UK
| | - Maya Schuldiner
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
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20
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Anderson NS, Mukherjee I, Bentivoglio CM, Barlowe C. The Golgin protein Coy1 functions in intra-Golgi retrograde transport and interacts with the COG complex and Golgi SNAREs. Mol Biol Cell 2017; 28:mbc.E17-03-0137. [PMID: 28794270 PMCID: PMC5620376 DOI: 10.1091/mbc.e17-03-0137] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Revised: 07/12/2017] [Accepted: 07/31/2017] [Indexed: 01/09/2023] Open
Abstract
Extended coiled-coil proteins of the Golgin family play prominent roles in maintaining the structure and function of the Golgi complex. Here we further investigate the Golgin protein Coy1 and document its function in retrograde transport between early Golgi compartments. Cells that lack Coy1 displayed a reduced half-life of the Och1 mannosyltransferase, an established cargo of intra-Golgi retrograde transport. Combining the coy1Δ mutation with deletions in other putative retrograde Golgins (sgm1Δ and rud3Δ) caused strong glycosylation and growth defects and reduced membrane association of the Conserved Oligomeric Golgi complex. In contrast, overexpression of COY1 inhibited the growth of mutant strains deficient in fusion activity at the Golgi (sed5-1 and sly1-ts). To map Coy1 protein interactions, co-immunoprecipitation experiments revealed an association with the Conserved Oliogmeric Golgi (COG) complex and with intra-Golgi SNARE proteins. These physical interactions are direct, as Coy1 was efficiently captured in vitro by Lobe A of the COG complex and the purified SNARE proteins Gos1, Sed5 and Sft1. Thus, our genetic, in vivo, and biochemical data indicate a role for Coy1 in regulating COG complex-dependent fusion of retrograde-directed COPI vesicles.
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Affiliation(s)
- Nadine S Anderson
- Department of Biochemistry & Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH 03755
| | - Indrani Mukherjee
- Department of Biochemistry & Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH 03755
| | - Christine M Bentivoglio
- Department of Biochemistry & Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH 03755
| | - Charles Barlowe
- Department of Biochemistry & Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH 03755
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21
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Ma W, Goldberg E, Goldberg J. ER retention is imposed by COPII protein sorting and attenuated by 4-phenylbutyrate. eLife 2017; 6. [PMID: 28594326 PMCID: PMC5464768 DOI: 10.7554/elife.26624] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Accepted: 04/18/2017] [Indexed: 01/07/2023] Open
Abstract
Native cargo proteins exit the endoplasmic reticulum (ER) in COPII-coated vesicles, whereas resident and misfolded proteins are substantially excluded from vesicles by a retention mechanism that remains unresolved. We probed the ER retention process using the proteostasis regulator 4-phenylbutyrate (4-PBA), which we show targets COPII protein to reduce the stringency of retention. 4-PBA competes with p24 proteins to bind COPII. When p24 protein uptake is blocked, COPII vesicles package resident proteins and an ER-trapped mutant LDL receptor. We further show that 4-PBA triggers the secretion of a KDEL-tagged luminal resident, implying that a compromised retention mechanism causes saturation of the KDEL retrieval system. The results indicate that stringent ER retention requires the COPII coat machinery to actively sort biosynthetic cargo from diffusible misfolded and resident ER proteins. DOI:http://dx.doi.org/10.7554/eLife.26624.001
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Affiliation(s)
- Wenfu Ma
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, United States
| | - Elena Goldberg
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, United States
| | - Jonathan Goldberg
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, United States.,Howard Hughes Medical Institute, New York, United States
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22
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Yuen CYL, Wang P, Kang BH, Matsumoto K, Christopher DA. A Non-Classical Member of the Protein Disulfide Isomerase Family, PDI7 of Arabidopsis thaliana, Localizes to the cis-Golgi and Endoplasmic Reticulum Membranes. PLANT & CELL PHYSIOLOGY 2017; 58:1103-1117. [PMID: 28444333 DOI: 10.1093/pcp/pcx057] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Accepted: 04/13/2017] [Indexed: 06/07/2023]
Abstract
Members of the protein disulfide isomerase (PDI)-C subfamily are chimeric proteins containing the thioredoxin (Trx) domain of PDIs, and the conserved N- and C-terminal Pfam domains of Erv41p/Erv46p-type cargo receptors. They are unique to plants and chromalveolates. The Arabidopsis genome encodes three PDI-C isoforms: PDI7, PDI12 and PDI13. Here we demonstrate that PDI7 is a 65 kDa integral membrane glycoprotein expressed throughout many Arabidopsis tissues. Using a PDI7-specific antibody, we show through immunoelectron microscopy that PDI7 localizes to the endoplasmic reticulum (ER) and Golgi membranes in wild-type root tip cells, and was also detected in vesicles. Tomographic modeling of the Golgi revealed that PDI7 was confined to the cis-Golgi, and accumulated primarily at the cis-most cisterna. Shoot apical meristem cells from transgenic plants overexpressing PDI7 exhibited a dramatic increase in anti-PDI7 labeling at the cis-Golgi. When N- or C-terminal fusions between PDI7 and the green fluorescent protein variant, GFP(S65T), were expressed in mesophyll protoplasts, the fusions co-localized with the ER marker, ER-mCherry. However, when GFP(S65T) was positioned internally within PDI7 (PDI7-GFPint), the fusion strongly co-localized with the cis-Golgi marker, mCherry-SYP31, and faintly labeled the ER. In contrast to the Golgi-resident fusion protein (Man49-mCherry), PDI7-GFPint did not redistribute to the ER after brefeldin A treatment. Protease protection experiments indicated that the Trx domain of PDI7 is located within the ER/Golgi lumen. We propose a model where PDI-C isoforms function as cargo receptors for proteins containing exposed cysteine residues, cycling them from the Golgi back to the ER.
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Affiliation(s)
- Christen Y L Yuen
- University of Hawaii, Molecular Biosciences & Bioengineering, Honolulu, HI, USA
| | - Pengfei Wang
- Chinese University of Hong Kong, Centre for Cell and Developmental Biology, State Key Laboratory of Agrobiotechnology, Shatin, Hong Kong, China
| | - Byung-Ho Kang
- Chinese University of Hong Kong, Centre for Cell and Developmental Biology, State Key Laboratory of Agrobiotechnology, Shatin, Hong Kong, China
| | - Kristie Matsumoto
- University of Hawaii, Molecular Biosciences & Bioengineering, Honolulu, HI, USA
| | - David A Christopher
- University of Hawaii, Molecular Biosciences & Bioengineering, Honolulu, HI, USA
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23
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Klink VP, Sharma K, Pant SR, McNeece B, Niraula P, Lawrence GW. Components of the SNARE-containing regulon are co-regulated in root cells undergoing defense. PLANT SIGNALING & BEHAVIOR 2017; 12:e1274481. [PMID: 28010187 PMCID: PMC5351740 DOI: 10.1080/15592324.2016.1274481] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Revised: 12/14/2016] [Accepted: 12/15/2016] [Indexed: 05/23/2023]
Abstract
The term regulon has been coined in the genetic model plant Arabidopsis thaliana, denoting a structural and physiological defense apparatus defined genetically through the identification of the penetration (pen) mutants. The regulon is composed partially by the soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptor (SNARE) syntaxin PEN1. PEN1 has homology to a Saccharomyces cerevisae gene that regulates a Secretion (Sec) protein, Suppressor of Sec 1 (Sso1p). The regulon is also composed of the β-glucosidase (PEN2) and an ATP binding cassette (ABC) transporter (PEN3). While important in inhibiting pathogen infection, limited observations have been made regarding the transcriptional regulation of regulon genes until now. Experiments made using the model agricultural Glycine max (soybean) have identified co-regulated gene expression of regulon components. The results explain the observation of hundreds of genes expressed specifically in the root cells undergoing the natural process of defense. Data regarding additional G. max genes functioning within the context of the regulon are presented here, including Sec 14, Sec 4 and Sec 23. Other examined G. max homologs of membrane fusion genes include an endosomal bromo domain-containing protein1 (Bro1), syntaxin6 (SYP6), SYP131, SYP71, SYP8, Bet1, coatomer epsilon (ϵ-COP), a coatomer zeta (ζ-COP) paralog and an ER to Golgi component (ERGIC) protein. Furthermore, the effectiveness of biochemical pathways that would function within the context of the regulon ave been examined, including xyloglucan xylosyltransferase (XXT), reticuline oxidase (RO) and galactinol synthase (GS). The experiments have unveiled the importance of the regulon during defense in the root and show how the deposition of callose relates to the process.
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Affiliation(s)
- Vincent P. Klink
- Department of Biological Sciences, Mississippi State University, Mississippi State, MS, USA
| | - Keshav Sharma
- Department of Biological Sciences, Mississippi State University, Mississippi State, MS, USA
| | - Shankar R. Pant
- Department of Biological Sciences, Mississippi State University, Mississippi State, MS, USA
| | - Brant McNeece
- Department of Biological Sciences, Mississippi State University, Mississippi State, MS, USA
| | - Prakash Niraula
- Department of Biological Sciences, Mississippi State University, Mississippi State, MS, USA
| | - Gary W. Lawrence
- Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Mississippi State University, Mississippi State, MS, USA
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24
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Becker B, Schnöder T, Schmitt MJ. Yeast Reporter Assay to Identify Cellular Components of Ricin Toxin A Chain Trafficking. Toxins (Basel) 2016; 8:toxins8120366. [PMID: 27929418 PMCID: PMC5198560 DOI: 10.3390/toxins8120366] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Revised: 11/22/2016] [Accepted: 11/30/2016] [Indexed: 01/08/2023] Open
Abstract
RTA, the catalytic A-subunit of the ribosome inactivating A/B toxin ricin, inhibits eukaryotic protein biosynthesis by depurination of 28S rRNA. Although cell surface binding of ricin holotoxin is mainly mediated through its B-subunit (RTB), sole application of RTA is also toxic, albeit to a significantly lower extent, suggesting alternative pathways for toxin uptake and transport. Since ricin toxin trafficking in mammalian cells is still not fully understood, we developed a GFP-based reporter assay in yeast that allows rapid identification of cellular components required for RTA uptake and subsequent transport through a target cell. We hereby show that Ypt6p, Sft2p and GARP-complex components play an important role in RTA transport, while neither the retromer complex nor COPIB vesicles are part of the transport machinery. Analyses of yeast knock-out mutants with chromosomal deletion in genes whose products regulate ADP-ribosylation factor GTPases (Arf-GTPases) and/or retrograde Golgi-to-ER (endoplasmic reticulum) transport identified Sso1p, Snc1p, Rer1p, Sec22p, Erv46p, Gea1p and Glo3p as novel components in RTA transport, suggesting the developed reporter assay as a powerful tool to dissect the multistep processes of host cell intoxication in yeast.
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Affiliation(s)
- Björn Becker
- Molecular and Cell Biology, Department of Biosciences and Center of Human and Molecular Biology (ZHMB), Saarland University, Saarbrücken D-66123, Germany.
| | - Tina Schnöder
- Molecular and Cell Biology, Department of Biosciences and Center of Human and Molecular Biology (ZHMB), Saarland University, Saarbrücken D-66123, Germany.
| | - Manfred J Schmitt
- Molecular and Cell Biology, Department of Biosciences and Center of Human and Molecular Biology (ZHMB), Saarland University, Saarbrücken D-66123, Germany.
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Gomez-Navarro N, Miller E. Protein sorting at the ER-Golgi interface. J Cell Biol 2016; 215:769-778. [PMID: 27903609 PMCID: PMC5166505 DOI: 10.1083/jcb.201610031] [Citation(s) in RCA: 166] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Revised: 11/02/2016] [Accepted: 11/17/2016] [Indexed: 01/01/2023] Open
Abstract
In this review, Gomez-Navarro and Miller summarize the principles of cargo sorting by the vesicle traffic machinery and consider the diverse mechanisms by which cargo proteins are selected and captured into different transport vesicles. Protein traffic is of critical importance for normal cellular physiology. In eukaryotes, spherical transport vesicles move proteins and lipids from one internal membrane-bound compartment to another within the secretory pathway. The process of directing each individual protein to a specific destination (known as protein sorting) is a crucial event that is intrinsically linked to vesicle biogenesis. In this review, we summarize the principles of cargo sorting by the vesicle traffic machinery and consider the diverse mechanisms by which cargo proteins are selected and captured into different transport vesicles. We focus on the first two compartments of the secretory pathway: the endoplasmic reticulum and Golgi. We provide an overview of the complexity and diversity of cargo adaptor function and regulation, focusing on recent mechanistic discoveries that have revealed insight into protein sorting in cells.
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Affiliation(s)
- Natalia Gomez-Navarro
- Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, England, UK
| | - Elizabeth Miller
- Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, England, UK
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Yuen CYL, Shek R, Kang BH, Matsumoto K, Cho EJ, Christopher DA. Arabidopsis protein disulfide isomerase-8 is a type I endoplasmic reticulum transmembrane protein with thiol-disulfide oxidase activity. BMC PLANT BIOLOGY 2016; 16:181. [PMID: 27549196 PMCID: PMC4994283 DOI: 10.1186/s12870-016-0869-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Accepted: 08/08/2016] [Indexed: 05/26/2023]
Abstract
BACKGROUND In eukaryotes, classical protein disulfide isomerases (PDIs) facilitate the oxidative folding of nascent secretory proteins in the endoplasmic reticulum by catalyzing the formation, breakage, and rearrangement of disulfide bonds. Terrestrial plants encode six structurally distinct subfamilies of PDIs. The novel PDI-B subfamily is unique to terrestrial plants, and in Arabidopsis is represented by a single member, PDI8. Unlike classical PDIs, which lack transmembrane domains (TMDs), PDI8 is unique in that it has a C-terminal TMD and a single N-terminal thioredoxin domain (instead of two). No PDI8 isoforms have been experimentally characterized to date. Here we describe the characterization of the membrane orientation, expression, sub-cellular localization, and biochemical function of this novel member of the PDI family. RESULTS Histochemical staining of plants harboring a PDI8 promoter:β-glucuronidase (GUS) fusion revealed that the PDI8 promoter is highly active in young, expanding leaves, the guard cells of cotyledons, and in the vasculature of several organs, including roots, leaves, cotyledons, and flowers. Immunoelectron microscopy studies using a PDI8-specific antibody on root and shoot apical cells revealed that PDI8 localizes to the endoplasmic reticulum (ER). Transient expression of two PDI8 fusions to green fluorescent protein (spGFP-PDI8 and PDI8-GFP-KKED) in leaf mesophyll protoplasts also resulted in labeling of the ER. Protease-protection immunoblot analysis indicated that PDI8 is a type I membrane protein, with its catalytic domain facing the ER lumen. The lumenal portion of PDI8 was able to functionally complement the loss of the prokaryotic protein foldase, disulfide oxidase (DsbA), as demonstrated by the reconstitution of periplasmic alkaline phosphatase in Escherichia coli. CONCLUSION The results indicate that PDI8 is a type I transmembrane protein with its catalytic domain facing the lumen of the ER and functions in the oxidation of cysteines to produce disulfide bonds. It likely plays a role in folding newly-synthesized secretory proteins as they translocate across the ER membrane into the lumen. These foundational results open the door to identifying the substrates of PDI8 to enable a more thorough understanding of its function in plants.
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Affiliation(s)
- Christen Y. L. Yuen
- Department of Molecular Biosciences and Bioengineering, University of Hawaii, 1955 East-West Rd., Ag. Science Rm 218, Honolulu, HI 96822 USA
| | - Roger Shek
- Department of Molecular Biosciences and Bioengineering, University of Hawaii, 1955 East-West Rd., Ag. Science Rm 218, Honolulu, HI 96822 USA
| | - Byung-Ho Kang
- The Chinese University of Hong Kong, School of Life Sciences, Shatin, Hong Kong, SAR China
| | - Kristie Matsumoto
- Department of Molecular Biosciences and Bioengineering, University of Hawaii, 1955 East-West Rd., Ag. Science Rm 218, Honolulu, HI 96822 USA
| | - Eun Ju Cho
- Department of Molecular Biosciences and Bioengineering, University of Hawaii, 1955 East-West Rd., Ag. Science Rm 218, Honolulu, HI 96822 USA
| | - David A. Christopher
- Department of Molecular Biosciences and Bioengineering, University of Hawaii, 1955 East-West Rd., Ag. Science Rm 218, Honolulu, HI 96822 USA
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Abstract
Transport of newly synthesized proteins from the endoplasmic reticulum (ER) to the Golgi complex is highly selective. As a general rule, such transport is limited to soluble and membrane-associated secretory proteins that have reached properly folded and assembled conformations. To secure the efficiency, fidelity, and control of this crucial transport step, cells use a combination of mechanisms. The mechanisms are based on selective retention of proteins in the ER to prevent uptake into transport vesicles, on selective capture of proteins in COPII carrier vesicles, on inclusion of proteins in these vesicles by default as part of fluid and membrane bulk flow, and on selective retrieval of proteins from post-ER compartments by retrograde vesicle transport.
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Affiliation(s)
- Charles Barlowe
- Biochemistry Department, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755;
| | - Ari Helenius
- Institute of Biochemistry, ETH Zurich, Zurich CH-8093, Switzerland
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28
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Yuen CYL, Wong K, Christopher DA. Phylogenetic characterization and promoter expression analysis of a novel hybrid protein disulfide isomerase/cargo receptor subfamily unique to plants and chromalveolates. Mol Genet Genomics 2016; 291:455-69. [PMID: 26300531 PMCID: PMC4729789 DOI: 10.1007/s00438-015-1106-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Accepted: 08/13/2015] [Indexed: 11/26/2022]
Abstract
Protein disulfide isomerases (PDIs) play critical roles in protein folding by catalyzing the formation and rearrangement of disulfide bonds in nascent secretory proteins. There are six distinct PDI subfamilies in terrestrial plants. A unique feature of PDI-C subfamily members is their homology to the yeast retrograde (Golgi-to-endoplasmic reticulum) cargo receptor proteins, Erv41p and Erv46p. Here, we demonstrate that plant Erv41p/Erv46p-like proteins are divided into three subfamilies: ERV-A, ERV-B and PDI-C, which all possess the N-proximal and C-proximal conserved domains of yeast Erv41p and Erv46p. However, in PDI-C isoforms, these domains are separated by a thioredoxin domain. The distribution of PDI-C isoforms among eukaryotes indicates that the PDI-C subfamily likely arose through an ancient exon-shuffling event that occurred before the divergence of plants from stramenopiles and rhizarians. Arabidopsis has three PDI-C genes: PDI7, PDI12, and PDI13. PDI12- and PDI13-promoter: β-glucuronidase (GUS) gene fusions are co-expressed in pollen and stipules, while PDI7 is distinctly expressed in the style, hydathodes, and leaf vasculature. The PDI-C thioredoxin domain active site motif CxxS is evolutionarily conserved among land plants. Whereas PDI12 and PDI13 retain the CxxS motif, PDI7 has a CxxC motif similar to classical PDIs. We hypothesize that PDI12 and PDI13 maintain the ancestral roles of PDI-C in Arabidopsis, while PDI7 has undergone neofunctionalization. The unusual PDI/cargo receptor hybrid arrangement in PDI-C isoforms has no counterpart in animals or yeast, and predicts the need for pairing redox functions with cargo receptor processes during protein trafficking in plants and other PDI-C containing organisms.
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Affiliation(s)
- Christen Y L Yuen
- Department of Molecular Biosciences and Bioengineering, University of Hawaii, 1955 East-West Rd., Ag. Science Rm 218, Honolulu, HI, 96822, USA
| | - Katharine Wong
- Department of Molecular Biosciences and Bioengineering, University of Hawaii, 1955 East-West Rd., Ag. Science Rm 218, Honolulu, HI, 96822, USA
| | - David A Christopher
- Department of Molecular Biosciences and Bioengineering, University of Hawaii, 1955 East-West Rd., Ag. Science Rm 218, Honolulu, HI, 96822, USA.
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Anelli T, Sannino S, Sitia R. Proteostasis and "redoxtasis" in the secretory pathway: Tales of tails from ERp44 and immunoglobulins. Free Radic Biol Med 2015; 83:323-30. [PMID: 25744412 DOI: 10.1016/j.freeradbiomed.2015.02.020] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 02/20/2015] [Accepted: 02/22/2015] [Indexed: 01/09/2023]
Abstract
In multicellular organisms, some cells are given the task of secreting huge quantities of proteins. To comply with their duty, they generally equip themselves with a highly developed endoplasmic reticulum (ER) and downstream organelles in the secretory pathway. These professional secretors face paramount proteostatic challenges in that they need to couple efficiency and fidelity in their secretory processes. On one hand, stringent quality control (QC) mechanisms operate from the ER onward to check the integrity of the secretome. On the other, the pressure to secrete can be overwhelming, as for instance on antibody-producing cells during infection. Maintaining homeostasis is particularly hard when the products to be released contain disulfide bonds, because oxidative folding entails production of reactive oxygen species. How are redox homeostasis ("redoxtasis") and proteostasis maintained despite the massive fluxes of cargo proteins traversing the pathway? Here we describe recent findings on how ERp44, a multifunctional chaperone of the secretory pathway, can modulate these processes integrating protein QC, redoxtasis, and calcium signaling.
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Affiliation(s)
- Tiziana Anelli
- Divisions of Genetics and Cell Biology, IRCCS Ospedale San Raffaele and Università Vita-Salute San Raffaele, 20132 Milan, Italy
| | - Sara Sannino
- Divisions of Genetics and Cell Biology, IRCCS Ospedale San Raffaele and Università Vita-Salute San Raffaele, 20132 Milan, Italy
| | - Roberto Sitia
- Divisions of Genetics and Cell Biology, IRCCS Ospedale San Raffaele and Università Vita-Salute San Raffaele, 20132 Milan, Italy.
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30
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Abstract
Retrieval mechanisms are essential to dynamically maintain the composition and functional homeostasis of secretory organelles. A recent study has identified a novel class of cargo receptor that retrieves a specific subset of escaped ER folding machinery from the Golgi.
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Affiliation(s)
- Ana M Perez-Linero
- Departamento de Biología Celular, Facultad de Biología, Universidad de Sevilla, 41012 Sevilla, Spain; Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, 41013 Sevilla, Spain
| | - Manuel Muñiz
- Departamento de Biología Celular, Facultad de Biología, Universidad de Sevilla, 41012 Sevilla, Spain; Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, 41013 Sevilla, Spain.
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Leslie M. Erv41–Erv46 complex recaptures wayward ER proteins. J Biophys Biochem Cytol 2015. [PMCID: PMC4298683 DOI: 10.1083/jcb.2082iti3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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