101
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Wu Z, Newstead S, Biggin PC. The KDEL trafficking receptor exploits pH to tune the strength of an unusual short hydrogen bond. Sci Rep 2020; 10:16903. [PMID: 33037300 PMCID: PMC7547670 DOI: 10.1038/s41598-020-73906-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Accepted: 09/23/2020] [Indexed: 12/27/2022] Open
Abstract
The endoplasmic reticulum (ER) is the main site of protein synthesis in eukaryotic cells and requires a high concentration of luminal chaperones to function. During protein synthesis, ER luminal chaperones are swept along the secretory pathway and must be retrieved to maintain cell viability. ER protein retrieval is achieved by the KDEL receptor, which recognises a C-terminal Lys-Asp-Glu-Leu (KDEL) sequence. Recognition of ER proteins by the KDEL receptor is pH dependent, with binding occurring under acidic conditions in the Golgi and release under conditions of higher pH in the ER. Recent crystal structures of the KDEL receptor in the apo and peptide bound state suggested that peptide binding drives the formation of a short-hydrogen bond that locks the KDEL sequence in the receptor and activates the receptor for COPI binding in the cytoplasm. Using quantum mechanical calculations we demonstrate that the strength of this short hydrogen bond is reinforced following protonation of a nearby histidine, providing a conceptual link between receptor protonation and KDEL peptide binding. Protonation also controls the water networks adjacent to the peptide binding site, leading to a conformational change that ultimately allows the receptor-complex to be recognized by the COPI system.
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Affiliation(s)
- Zhiyi Wu
- Department of Biochemistry, South Parks Road, Oxford, OX1 3QU, UK
| | - Simon Newstead
- Department of Biochemistry, South Parks Road, Oxford, OX1 3QU, UK.
| | - Philip C Biggin
- Department of Biochemistry, South Parks Road, Oxford, OX1 3QU, UK.
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102
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Newstead S, Barr F. Molecular basis for KDEL-mediated retrieval of escaped ER-resident proteins - SWEET talking the COPs. J Cell Sci 2020; 133:133/19/jcs250100. [PMID: 33037041 PMCID: PMC7561476 DOI: 10.1242/jcs.250100] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Accepted: 07/30/2020] [Indexed: 12/11/2022] Open
Abstract
Protein localisation in the cell is controlled through the function of trafficking receptors, which recognise specific signal sequences and direct cargo proteins to different locations. The KDEL receptor (KDELR) was one of the first intracellular trafficking receptors identified and plays an essential role in maintaining the integrity of the early secretory pathway. The receptor recognises variants of a canonical C-terminal Lys-Asp-Glu-Leu (KDEL) signal sequence on ER-resident proteins when these escape to the Golgi, and targets these proteins to COPI- coated vesicles for retrograde transport back to the ER. The empty receptor is then recycled from the ER back to the Golgi by COPII-coated vesicles. Crystal structures of the KDELR show that it is structurally related to the PQ-loop family of transporters that are found in both pro- and eukaryotes, and shuttle sugars, amino acids and vitamins across cellular membranes. Furthermore, analogous to PQ-loop transporters, the KDELR undergoes a pH-dependent and ligand-regulated conformational cycle. Here, we propose that the striking structural similarity between the KDELR and PQ-loop transporters reveals a connection between transport and trafficking in the cell, with important implications for understanding trafficking receptor evolution and function. Summary: The structure of the KDEL receptor gives new insights into the close connection between trafficking and transport in the cell.
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Affiliation(s)
- Simon Newstead
- Department of Biochemistry, University of Oxford, South Parks Rd, Oxford OX1 3QU, UK
| | - Francis Barr
- Department of Biochemistry, University of Oxford, South Parks Rd, Oxford OX1 3QU, UK
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103
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Targeted degradation of immune checkpoint proteins: emerging strategies for cancer immunotherapy. Oncogene 2020; 39:7106-7113. [PMID: 33024277 DOI: 10.1038/s41388-020-01491-w] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2020] [Revised: 09/19/2020] [Accepted: 09/24/2020] [Indexed: 02/06/2023]
Abstract
Cancer immunotherapy using immune-checkpoint blockade has displayed promising clinical effects, but prevalent antibody-based inhibitors face multiple challenges such as low response rate, acquired resistance, and adverse effects. The intracellular expression of PD-1/PD-L1 in recycling endosomes and their active trafficking to membrane highlight the importance of depleting rather than interfering with checkpoint proteins. Preclinical investigations on the therapeutic effects of lead compounds that function by degrading immune checkpoint ligands and receptors have reported highly promising results. By harnessing the degradation capabilities of the lysosome, proteasome and autophagosomes, different small molecules and peptides potently induced degradation of checkpoint proteins and enhanced anti-tumor immunity. Both in vitro and in vivo experiments support the therapeutic efficacy of these molecules. Thus, targeted degradation through endo-lysosomal, autophagic, proteasomal, or endoplasmic reticulum-related pathways may provide promising strategies for tackling the challenges in cancer immunotherapy.
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104
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Blagotinšek Cokan K, Mavri M, Rutland CS, Glišić S, Senćanski M, Vrecl M, Kubale V. Critical Impact of Different Conserved Endoplasmic Retention Motifs and Dopamine Receptor Interacting Proteins (DRIPs) on Intracellular Localization and Trafficking of the D 2 Dopamine Receptor (D 2-R) Isoforms. Biomolecules 2020; 10:biom10101355. [PMID: 32977535 PMCID: PMC7598153 DOI: 10.3390/biom10101355] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Revised: 09/09/2020] [Accepted: 09/18/2020] [Indexed: 01/13/2023] Open
Abstract
The type 2 dopamine receptor D2 (D2-R), member of the G protein-coupled receptor (GPCR) superfamily, exists in two isoforms, short (D2S-R) and long (D2L-R). They differ by an additional 29 amino acids (AA) in the third cytoplasmic loop (ICL3) of the D2L-R. These isoforms differ in their intracellular localization and trafficking functionality, as D2L-R possesses a larger intracellular pool, mostly in the endoplasmic reticulum (ER). This review focuses on the evolutionarily conserved motifs in the ICL3 of the D2-R and proteins interacting with the ICL3 of both isoforms, specifically with the 29 AA insert. These motifs might be involved in D2-R exit from the ER and have an impact on cell-surface and intracellular localization and, therefore, also play a role in the function of dopamine receptor signaling, ligand binding and possible homo/heterodimerization. Our recent bioinformatic data on potential new interaction partners for the ICL3 of D2-Rs are also presented. Both are highly relevant, and have clinical impacts on the pathophysiology of several diseases such as Parkinson’s disease, schizophrenia, Tourette’s syndrome, Huntington’s disease, manic depression, and others, as they are connected to a variety of essential motifs and differences in communication with interaction partners.
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Affiliation(s)
- Kaja Blagotinšek Cokan
- Department of Anatomy, Histology with Embryology and Cytology, Institute of Preclinical Sciences, Veterinary Faculty, University of Ljubljana, Gerbičeva 60, 1000 Ljubljana, Slovenia; (K.B.C.); (M.M.); (M.V.)
| | - Maša Mavri
- Department of Anatomy, Histology with Embryology and Cytology, Institute of Preclinical Sciences, Veterinary Faculty, University of Ljubljana, Gerbičeva 60, 1000 Ljubljana, Slovenia; (K.B.C.); (M.M.); (M.V.)
| | - Catrin Sian Rutland
- School of Veterinary Medicine and Science, Medical Faculty, University of Nottingham, Sutton, Bonington Campus, Loughborough LE12 5RD, UK;
| | - Sanja Glišić
- Center for Multidisciplinary Research, Institute of Nuclear Sciences VINCA, University of Belgrade, Mike Petrovića Alasa 12-14, 11351 Vinča, Belgrade, Serbia; (S.G.); (M.S.)
| | - Milan Senćanski
- Center for Multidisciplinary Research, Institute of Nuclear Sciences VINCA, University of Belgrade, Mike Petrovića Alasa 12-14, 11351 Vinča, Belgrade, Serbia; (S.G.); (M.S.)
| | - Milka Vrecl
- Department of Anatomy, Histology with Embryology and Cytology, Institute of Preclinical Sciences, Veterinary Faculty, University of Ljubljana, Gerbičeva 60, 1000 Ljubljana, Slovenia; (K.B.C.); (M.M.); (M.V.)
| | - Valentina Kubale
- Department of Anatomy, Histology with Embryology and Cytology, Institute of Preclinical Sciences, Veterinary Faculty, University of Ljubljana, Gerbičeva 60, 1000 Ljubljana, Slovenia; (K.B.C.); (M.M.); (M.V.)
- Correspondence:
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105
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Freitas N, Enguehard M, Denolly S, Levy C, Neveu G, Lerolle S, Devignot S, Weber F, Bergeron E, Legros V, Cosset FL. The interplays between Crimean-Congo hemorrhagic fever virus (CCHFV) M segment-encoded accessory proteins and structural proteins promote virus assembly and infectivity. PLoS Pathog 2020; 16:e1008850. [PMID: 32956404 PMCID: PMC7529341 DOI: 10.1371/journal.ppat.1008850] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Revised: 10/01/2020] [Accepted: 08/01/2020] [Indexed: 02/07/2023] Open
Abstract
Crimean-Congo hemorrhagic fever virus (CCHFV) is a tick-borne orthonairovirus that has become a serious threat to the public health. CCHFV has a single-stranded, tripartite RNA genome composed of L, M, and S segments. Cleavage of the M polyprotein precursor generates the two envelope glycoproteins (GPs) as well as three secreted nonstructural proteins GP38 and GP85 or GP160, representing GP38 only or GP38 linked to a mucin-like protein (MLD), and a double-membrane-spanning protein called NSm. Here, we examined the relevance of each M-segment non-structural proteins in virus assembly, egress and infectivity using a well-established CCHFV virus-like-particle system (tc-VLP). Deletion of MLD protein had no impact on infectivity although it reduced by 60% incorporation of GPs into particles. Additional deletion of GP38 abolished production of infectious tc-VLPs. The loss of infectivity was associated with impaired Gc maturation and exclusion from the Golgi, showing that Gn is not sufficient to target CCHFV GPs to the site of assembly. Consistent with this, efficient complementation was achieved in cells expressing MLD-GP38 in trans with increased levels of preGc to Gc conversion, co-targeting to the Golgi, resulting in particle incorporation and restored infectivity. Contrastingly, a MLD-GP38 variant retained in the ER allowed preGc cleavage but failed to rescue miss-localization or infectivity. NSm deletion, conversely, did not affect trafficking of Gc but interfered with Gc processing, particle formation and secretion. NSm expression affected N-glycosylation of different viral proteins most likely due to increased speed of trafficking through the secretory pathway. This highlights a potential role of NSm in overcoming Golgi retention and facilitating CCHFV egress. Thus, deletions of GP38 or NSm demonstrate their important role on CCHFV particle production and infectivity. GP85 is an essential viral factor for preGc cleavage, trafficking and Gc incorporation into particles, whereas NSm protein is involved in CCHFV assembly and virion secretion. Orthonairoviruses, like the lethal Crimean-Congo hemorrhagic fever virus (CCHFV), encode secreted glycoproteins, such as GP38, in addition to virion envelope glycoproteins (Gn and Gc) that are processed by internal cleavage of the viral M segment encoded polyprotein. CCHFV MLD-GP38 proteins (GP160/GP85) also include an N-terminal domain encompassing a mucin-like protein that is released from GP38 by Furin. The protective effect of non-neutralizing monoclonal antibodies targeting GP38 against lethal CCHFV challenge previously highlighted the importance of GP38 in CCHFV replication. CCHFV also encodes a double-membrane-spanning protein (NSm) of unknown function, located between the Gn and Gc on the polyprotein. To investigate the roles of these so-called accessory proteins encoded by the CCHFV M-segment in virus formation and infectivity, we generated several M-segment deletion mutants and tested them in a CCHFV transcription-entry-competent virus-like particle (tc-VLP) system. Here, we demonstrate that GP38 is crucial for Gc biogenesis, interaction with Gn and trafficking to the Golgi, and that its deletion abrogates formation of infectious particles. We also show that NSm increases the rate of protein trafficking through the secretory pathway with altered N-glycosylation profiles that are advantageous for efficient virus release. These data advanced our understanding of GP38 and NSm roles and CCHFV-host interactions.
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Affiliation(s)
- Natalia Freitas
- CIRI–Centre International de Recherche en Infectiologie, Univ Lyon, Université Claude Bernard Lyon 1, Inserm, U1111, CNRS, UMR5308, ENS Lyon, 46 allée d’Italie, Lyon, France
- * E-mail: (NF); (FLC)
| | - Margot Enguehard
- CIRI–Centre International de Recherche en Infectiologie, Univ Lyon, Université Claude Bernard Lyon 1, Inserm, U1111, CNRS, UMR5308, ENS Lyon, 46 allée d’Italie, Lyon, France
| | - Solène Denolly
- CIRI–Centre International de Recherche en Infectiologie, Univ Lyon, Université Claude Bernard Lyon 1, Inserm, U1111, CNRS, UMR5308, ENS Lyon, 46 allée d’Italie, Lyon, France
| | - Camille Levy
- CIRI–Centre International de Recherche en Infectiologie, Univ Lyon, Université Claude Bernard Lyon 1, Inserm, U1111, CNRS, UMR5308, ENS Lyon, 46 allée d’Italie, Lyon, France
| | - Gregory Neveu
- CIRI–Centre International de Recherche en Infectiologie, Univ Lyon, Université Claude Bernard Lyon 1, Inserm, U1111, CNRS, UMR5308, ENS Lyon, 46 allée d’Italie, Lyon, France
| | - Solène Lerolle
- CIRI–Centre International de Recherche en Infectiologie, Univ Lyon, Université Claude Bernard Lyon 1, Inserm, U1111, CNRS, UMR5308, ENS Lyon, 46 allée d’Italie, Lyon, France
| | - Stephanie Devignot
- Institute for Virology, FB10-Veterinary Medicine, Justus-Liebig University, Gießen, Germany
| | - Friedemann Weber
- Institute for Virology, FB10-Veterinary Medicine, Justus-Liebig University, Gießen, Germany
| | - Eric Bergeron
- Viral Special Pathogens Branch, Division of High-Consequence Pathogens and Pathology, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
| | - Vincent Legros
- CIRI–Centre International de Recherche en Infectiologie, Univ Lyon, Université Claude Bernard Lyon 1, Inserm, U1111, CNRS, UMR5308, ENS Lyon, 46 allée d’Italie, Lyon, France
- Université de Lyon, VetAgro Sup, Marcy-l'Étoile, France
| | - François-Loïc Cosset
- CIRI–Centre International de Recherche en Infectiologie, Univ Lyon, Université Claude Bernard Lyon 1, Inserm, U1111, CNRS, UMR5308, ENS Lyon, 46 allée d’Italie, Lyon, France
- * E-mail: (NF); (FLC)
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106
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Brecker M, Khakhina S, Schubert TJ, Thompson Z, Rubenstein RC. The Probable, Possible, and Novel Functions of ERp29. Front Physiol 2020; 11:574339. [PMID: 33013490 PMCID: PMC7506106 DOI: 10.3389/fphys.2020.574339] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Accepted: 08/14/2020] [Indexed: 12/16/2022] Open
Abstract
The luminal endoplasmic reticulum (ER) protein of 29 kDa (ERp29) is a ubiquitously expressed cellular agent with multiple critical roles. ERp29 regulates the biosynthesis and trafficking of several transmembrane and secretory proteins, including the cystic fibrosis transmembrane conductance regulator (CFTR), the epithelial sodium channel (ENaC), thyroglobulin, connexin 43 hemichannels, and proinsulin. ERp29 is hypothesized to promote ER to cis-Golgi cargo protein transport via COP II machinery through its interactions with the KDEL receptor; this interaction may facilitate the loading of ERp29 clients into COP II vesicles. ERp29 also plays a role in ER stress (ERS) and the unfolded protein response (UPR) and is implicated in oncogenesis. Here, we review the vast array of ERp29’s clients, its role as an ER to Golgi escort protein, and further suggest ERp29 as a potential target for therapies related to diseases of protein misfolding and mistrafficking.
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Affiliation(s)
- Margaret Brecker
- Cystic Fibrosis Center, The Children’s Hospital of Philadelphia, Philadelphia, PA, United States
| | - Svetlana Khakhina
- Cystic Fibrosis Center, The Children’s Hospital of Philadelphia, Philadelphia, PA, United States
| | - Tyler J. Schubert
- Cystic Fibrosis Center, The Children’s Hospital of Philadelphia, Philadelphia, PA, United States
| | - Zachary Thompson
- Cystic Fibrosis Center, The Children’s Hospital of Philadelphia, Philadelphia, PA, United States
| | - Ronald C. Rubenstein
- Cystic Fibrosis Center, The Children’s Hospital of Philadelphia, Philadelphia, PA, United States
- Department of Pediatrics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, United States
- Division of Allergy and Pulmonary Medicine, Department of Pediatrics, Washington University in St. Louis School of Medicine, St. Louis, MO, United States
- *Correspondence: Ronald C. Rubenstein, ;
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107
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Cendrowski J, Kaczmarek M, Mazur M, Kuzmicz-Kowalska K, Jastrzebski K, Brewinska-Olchowik M, Kominek A, Piwocka K, Miaczynska M. Splicing variation of BMP2K balances abundance of COPII assemblies and autophagic degradation in erythroid cells. eLife 2020; 9:58504. [PMID: 32795391 PMCID: PMC7473771 DOI: 10.7554/elife.58504] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2020] [Accepted: 08/13/2020] [Indexed: 12/26/2022] Open
Abstract
Intracellular transport undergoes remodeling upon cell differentiation, which involves cell type-specific regulators. Bone morphogenetic protein 2-inducible kinase (BMP2K) has been potentially implicated in endocytosis and cell differentiation but its molecular functions remained unknown. We discovered that its longer (L) and shorter (S) splicing variants regulate erythroid differentiation in a manner unexplainable by their involvement in AP-2 adaptor phosphorylation and endocytosis. However, both variants interact with SEC16A and could localize to the juxtanuclear secretory compartment. Variant-specific depletion approach showed that BMP2K isoforms constitute a BMP2K-L/S regulatory system that controls the distribution of SEC16A and SEC24B as well as SEC31A abundance at COPII assemblies. Finally, we found L to promote and S to restrict autophagic degradation and erythroid differentiation. Hence, we propose that BMP2K-L and BMP2K-S differentially regulate abundance and distribution of COPII assemblies as well as autophagy, possibly thereby fine-tuning erythroid differentiation.
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Affiliation(s)
- Jaroslaw Cendrowski
- Laboratory of Cell Biology, International Institute of Molecular and Cell Biology, Warsaw, Poland
| | - Marta Kaczmarek
- Laboratory of Cell Biology, International Institute of Molecular and Cell Biology, Warsaw, Poland
| | - Michał Mazur
- Laboratory of Cell Biology, International Institute of Molecular and Cell Biology, Warsaw, Poland
| | | | - Kamil Jastrzebski
- Laboratory of Cell Biology, International Institute of Molecular and Cell Biology, Warsaw, Poland
| | | | - Agata Kominek
- Laboratory of Cytometry, Nencki Institute of Experimental Biology, Warsaw, Poland
| | - Katarzyna Piwocka
- Laboratory of Cytometry, Nencki Institute of Experimental Biology, Warsaw, Poland
| | - Marta Miaczynska
- Laboratory of Cell Biology, International Institute of Molecular and Cell Biology, Warsaw, Poland
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108
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Dimou S, Diallinas G. Life and Death of Fungal Transporters under the Challenge of Polarity. Int J Mol Sci 2020; 21:ijms21155376. [PMID: 32751072 PMCID: PMC7432044 DOI: 10.3390/ijms21155376] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Revised: 07/24/2020] [Accepted: 07/27/2020] [Indexed: 12/14/2022] Open
Abstract
Eukaryotic plasma membrane (PM) transporters face critical challenges that are not widely present in prokaryotes. The two most important issues are proper subcellular traffic and targeting to the PM, and regulated endocytosis in response to physiological, developmental, or stress signals. Sorting of transporters from their site of synthesis, the endoplasmic reticulum (ER), to the PM has been long thought, but not formally shown, to occur via the conventional Golgi-dependent vesicular secretory pathway. Endocytosis of specific eukaryotic transporters has been studied more systematically and shown to involve ubiquitination, internalization, and sorting to early endosomes, followed by turnover in the multivesicular bodies (MVB)/lysosomes/vacuole system. In specific cases, internalized transporters have been shown to recycle back to the PM. However, the mechanisms of transporter forward trafficking and turnover have been overturned recently through systematic work in the model fungus Aspergillus nidulans. In this review, we present evidence that shows that transporter traffic to the PM takes place through Golgi bypass and transporter endocytosis operates via a mechanism that is distinct from that of recycling membrane cargoes essential for fungal growth. We discuss these findings in relation to adaptation to challenges imposed by cell polarity in fungi as well as in other eukaryotes and provide a rationale of why transporters and possibly other housekeeping membrane proteins ‘avoid’ routes of polar trafficking.
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109
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Sengupta P, Lippincott-Schwartz J. Revisiting Membrane Microdomains and Phase Separation: A Viral Perspective. Viruses 2020; 12:v12070745. [PMID: 32664429 PMCID: PMC7412473 DOI: 10.3390/v12070745] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Revised: 06/29/2020] [Accepted: 07/07/2020] [Indexed: 12/11/2022] Open
Abstract
Retroviruses selectively incorporate a specific subset of host cell proteins and lipids into their outer membrane when they bud out from the host plasma membrane. This specialized viral membrane composition is critical for both viral survivability and infectivity. Here, we review recent findings from live cell imaging of single virus assembly demonstrating that proteins and lipids sort into the HIV retroviral membrane by a mechanism of lipid-based phase partitioning. The findings showed that multimerizing HIV Gag at the assembly site creates a liquid-ordered lipid phase enriched in cholesterol and sphingolipids. Proteins with affinity for this specialized lipid environment partition into it, resulting in the selective incorporation of proteins into the nascent viral membrane. Building on this and other work in the field, we propose a model describing how HIV Gag induces phase separation of the viral assembly site through a mechanism involving transbilayer coupling of lipid acyl chains and membrane curvature changes. Similar phase-partitioning pathways in response to multimerizing structural proteins likely help sort proteins into the membranes of other budding structures within cells.
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110
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Zhang J, Andersen JP, Sun H, Liu X, Sonenberg N, Nie J, Shi Y. Aster-C coordinates with COP I vesicles to regulate lysosomal trafficking and activation of mTORC1. EMBO Rep 2020; 21:e49898. [PMID: 32648345 DOI: 10.15252/embr.201949898] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Revised: 05/29/2020] [Accepted: 06/12/2020] [Indexed: 01/27/2023] Open
Abstract
Nutrient sensing by the mTOR complex 1 (mTORC1) requires its translocation to the lysosomal membrane. Upon amino acids removal, mTORC1 becomes cytosolic and inactive, yet its precise subcellular localization and the mechanism of inhibition remain elusive. Here, we identified Aster-C as a negative regulator of mTORC1 signaling. Aster-C earmarked a special rough ER subdomain where it sequestered mTOR together with the GATOR2 complex to prevent mTORC1 activation during nutrient starvation. Amino acids stimulated rapid disassociation of mTORC1 from Aster-C concurrently with assembly of COP I vesicles which escorted mTORC1 to the lysosomal membrane. Consequently, ablation of Aster-C led to spontaneous activation of mTORC1 and dissociation of TSC2 from lysosomes, whereas inhibition of COP I vesicle biogenesis or actin dynamics prevented mTORC1 activation. Together, these findings identified Aster-C as a missing link between lysosomal trafficking and mTORC1 activation by revealing an unexpected role of COP I vesicles in mTORC1 signaling.
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Affiliation(s)
- Jun Zhang
- Department of Pharmacology, Sam and Ann Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| | - John-Paul Andersen
- Department of Pharmacology, Sam and Ann Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| | - Haoran Sun
- Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing, China
| | - Xuyun Liu
- Department of Pharmacology, Sam and Ann Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| | - Nahum Sonenberg
- Department of Biochemistry, McGill University, Montreal, QC, Canada
| | - Jia Nie
- Department of Pharmacology, Sam and Ann Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| | - Yuguang Shi
- Department of Pharmacology, Sam and Ann Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA.,Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing, China
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111
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Huang S, Tang M, Jiang H, Li Y, Hu H. A COPII subunit interacting with ER-phagy receptor: a new potential avenue to maintaining neuronal homeostasis. Acta Biochim Biophys Sin (Shanghai) 2020; 52:698-700. [PMID: 32348448 DOI: 10.1093/abbs/gmaa031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2019] [Revised: 11/19/2019] [Accepted: 11/07/2019] [Indexed: 11/12/2022] Open
Affiliation(s)
- Shifang Huang
- Department of Pharmacology, Yongzhou Vocational Technical College, Yongzhou 425000, China
| | - Mingzhu Tang
- Guangzhou Regenerative Medicine and Health Guangdong Laboratory, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China
| | - Honglu Jiang
- Department of Pharmacology, Yongzhou Radio and TV University, Yongzhou 425000, China
| | - Yuting Li
- Department of Pharmacology, Yongzhou Vocational Technical College, Yongzhou 425000, China
| | - Haoliang Hu
- Department of Pharmacology, Yongzhou Vocational Technical College, Yongzhou 425000, China
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112
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Fu C, Zhan J, Huai J, Ma S, Li M, Chen G, Chen M, Cai Y, Ou C. Furin-instructed molecular self-assembly actuates endoplasmic reticulum stress-mediated apoptosis for cancer therapy. NANOSCALE 2020; 12:12126-12132. [PMID: 32484200 DOI: 10.1039/d0nr00151a] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Protein quality control and proteostasis are essential to maintain cell survival as once disordered, they will trigger endoplasmic reticulum (ER) stress and even initiate apoptosis. Severe ER stress-mediated apoptosis is the cause of neurodegenerative diseases and expected to be a new target for cancer therapy. In this study, we designed a small molecule of 1-Nap to execute furin-instructed molecular self-assembly for selectively inhibiting the growth of MDA-MB-468 cells in vitro and in vivo. According to the results of transmission electron microscopy (TEM) and HPLC tracing analysis, 1-Nap is capable of self-assembling upon furin-instructed cleavage that transforms 1-Nap nanoparticles to 1-Nap nanofibers. Fluorescence imaging and Western-blot analysis results indicate that the furin-instructed self-assembly of 1-Nap rather than its ER-targeting interaction is indispensable for the ER stress and activation of apoptosis. The furin-instructed self-assembly of 1-Nap is associated with both the ER (1-Nap's targeting location) and the trans-Golgi network (furin's location); this inspired us to reasonably believe that the blocking of ER-to-Golgi traffic in the secretory pathway by molecular self-assembly may be the intrinsic motivation for controlling cell fate. This work provides a new way for the targeted disturbance of the proteostasis of cells through molecular self-assembly for developing cancer therapeutics.
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Affiliation(s)
- Chenxing Fu
- Department of Cardiology, Laboratory of Heart Center, Zhujiang Hospital, Sino-Japanese Cooperation Platform for Translational Research in Heart Failure, Guangdong Provincial Biomedical Engineering Technology Research Center for Cardiovascular Diseases, Guangzhou 510280, People's Republic of China.
| | - Jie Zhan
- Shunde Hospital, Southern Medical University, (the First People's Hospital of Shunde), Foshan 528300, People's Republic of China
| | - Junqi Huai
- Department of Cardiology, Laboratory of Heart Center, Zhujiang Hospital, Sino-Japanese Cooperation Platform for Translational Research in Heart Failure, Guangdong Provincial Biomedical Engineering Technology Research Center for Cardiovascular Diseases, Guangzhou 510280, People's Republic of China.
| | - Shaodan Ma
- Department of Cardiology, Laboratory of Heart Center, Zhujiang Hospital, Sino-Japanese Cooperation Platform for Translational Research in Heart Failure, Guangdong Provincial Biomedical Engineering Technology Research Center for Cardiovascular Diseases, Guangzhou 510280, People's Republic of China.
| | - Minghui Li
- Department of Cardiology, Laboratory of Heart Center, Zhujiang Hospital, Sino-Japanese Cooperation Platform for Translational Research in Heart Failure, Guangdong Provincial Biomedical Engineering Technology Research Center for Cardiovascular Diseases, Guangzhou 510280, People's Republic of China.
| | - Guoqin Chen
- Cardiology Department of Panyu Central Hospital and Cardiovascular Disease Institute of Panyu District, Guangzhou 511400, People's Republic of China
| | - Minsheng Chen
- Department of Cardiology, Laboratory of Heart Center, Zhujiang Hospital, Sino-Japanese Cooperation Platform for Translational Research in Heart Failure, Guangdong Provincial Biomedical Engineering Technology Research Center for Cardiovascular Diseases, Guangzhou 510280, People's Republic of China.
| | - Yanbin Cai
- Department of Cardiology, Laboratory of Heart Center, Zhujiang Hospital, Sino-Japanese Cooperation Platform for Translational Research in Heart Failure, Guangdong Provincial Biomedical Engineering Technology Research Center for Cardiovascular Diseases, Guangzhou 510280, People's Republic of China.
| | - Caiwen Ou
- Department of Cardiology, Laboratory of Heart Center, Zhujiang Hospital, Sino-Japanese Cooperation Platform for Translational Research in Heart Failure, Guangdong Provincial Biomedical Engineering Technology Research Center for Cardiovascular Diseases, Guangzhou 510280, People's Republic of China.
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113
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Dimou S, Martzoukou O, Dionysopoulou M, Bouris V, Amillis S, Diallinas G. Translocation of nutrient transporters to cell membrane via Golgi bypass in Aspergillus nidulans. EMBO Rep 2020; 21:e49929. [PMID: 32452614 DOI: 10.15252/embr.201949929] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Revised: 04/15/2020] [Accepted: 04/24/2020] [Indexed: 02/06/2023] Open
Abstract
Nutrient transporters, being polytopic membrane proteins, are believed, but not formally shown, to traffic from their site of synthesis, the ER, to the plasma membrane through Golgi-dependent vesicular trafficking. Here, we develop a novel genetic system to investigate the trafficking of a neosynthesized model transporter, the well-studied UapA purine transporter of Aspergillus nidulans. We show that sorting of neosynthesized UapA to the plasma membrane (PM) bypasses the Golgi and does not necessitate key Rab GTPases, AP adaptors, microtubules or endosomes. UapA PM localization is found to be dependent on functional COPII vesicles, actin polymerization, clathrin heavy chain and the PM t-SNARE SsoA. Actin polymerization proved to primarily affect COPII vesicle formation, whereas the essential role of ClaH seems indirect and less clear. We provide evidence that other evolutionary and functionally distinct transporters of A. nidulans also follow the herein identified Golgi-independent trafficking route of UapA. Importantly, our findings suggest that specific membrane cargoes drive the formation of distinct COPII subpopulations that bypass the Golgi to be sorted non-polarly to the PM, and thus serving house-keeping cell functions.
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Affiliation(s)
- Sofia Dimou
- Department of Biology, National and Kapodistrian University of Athens, Athens, Greece
| | - Olga Martzoukou
- Department of Biology, National and Kapodistrian University of Athens, Athens, Greece
| | | | - Vangelis Bouris
- Department of Biology, National and Kapodistrian University of Athens, Athens, Greece
| | - Sotiris Amillis
- Department of Biology, National and Kapodistrian University of Athens, Athens, Greece
| | - George Diallinas
- Department of Biology, National and Kapodistrian University of Athens, Athens, Greece
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114
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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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115
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Ilie A, Boucher A, Park J, Berghuis AM, McKinney RA, Orlowski J. Assorted dysfunctions of endosomal alkali cation/proton exchanger SLC9A6 variants linked to Christianson syndrome. J Biol Chem 2020; 295:7075-7095. [PMID: 32277048 PMCID: PMC7242699 DOI: 10.1074/jbc.ra120.012614] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 04/07/2020] [Indexed: 12/15/2022] Open
Abstract
Genetic screening has identified numerous variants of the endosomal solute carrier family 9 member A6 (SLC9A6)/(Na+,K+)/H+ exchanger 6 (NHE6) gene that cause Christianson syndrome, a debilitating X-linked developmental disorder associated with a range of neurological, somatic, and behavioral symptoms. Many of these variants cause complete loss of NHE6 expression, but how subtler missense substitutions or nonsense mutations that partially truncate its C-terminal cytoplasmic regulatory domain impair NHE6 activity and endosomal function are poorly understood. Here, we describe the molecular and cellular consequences of six unique mutations located in the N-terminal cytoplasmic segment (A9S), the membrane ion translocation domain (L188P and G383D), and the C-terminal regulatory domain (E547*, R568Q, and W570*) of human NHE6 that purportedly cause disease. Using a heterologous NHE6-deficient cell expression system, we show that the biochemical, catalytic, and cellular properties of the A9S and R568Q variants were largely indistinguishable from those of the WT transporter, which obscured their disease significance. By contrast, the L188P, G383D, E547*, and W570* mutants exhibited variable deficiencies in biosynthetic post-translational maturation, membrane sorting, pH homeostasis in recycling endosomes, and cargo trafficking, and they also triggered apoptosis. These findings broaden our understanding of the molecular dysfunctions of distinct NHE6 variants associated with Christianson syndrome.
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Affiliation(s)
- Alina Ilie
- Department of Physiology, McGill University, Montreal, Quebec H3G 0B1, Canada
| | - Annie Boucher
- Department of Physiology, McGill University, Montreal, Quebec H3G 0B1, Canada
| | - Jaeok Park
- Department of Biochemistry, McGill University, Montreal, Quebec H3G 0B1, Canada
| | | | - R Anne McKinney
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec H3G 0B1, Canada
| | - John Orlowski
- Department of Physiology, McGill University, Montreal, Quebec H3G 0B1, Canada
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116
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Ahmadpour D, Babazadeh R, Nystrom T. Hitchhiking on vesicles: a way to harness age-related proteopathies? FEBS J 2020; 287:5068-5079. [PMID: 32336030 DOI: 10.1111/febs.15345] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Revised: 04/06/2020] [Accepted: 04/23/2020] [Indexed: 12/27/2022]
Abstract
Central to proteopathies and leading to most age-related neurodegenerative disorders is a failure in protein quality control (PQC). To harness the toxicity of misfolded and damaged disease proteins, such proteins are either refolded, degraded by temporal PQC, or sequestered by spatial PQC into specific, organelle-associated, compartments within the cell. Here, we discuss the impact of vesicle trafficking pathways in general, and syntaxin 5 in particular, as key players in spatial PQC directing misfolded proteins to the surface of vacuole and mitochondria, which facilitates their clearance and detoxification. Since boosting vesicle trafficking genetically can positively impact on spatial PQC and make cells less sensitive to misfolded disease proteins, we speculate that regulators of such trafficking might serve as therapeutic targets for age-related neurological disorders.
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Affiliation(s)
- Doryaneh Ahmadpour
- Institute for Biomedicine, Sahlgrenska Academy, Centre for Ageing and Health-AgeCap, University of Gothenburg, Sweden.,Institute of Neuroscience and Physiology, Department of Psychiatry and Neurochemistry, Sahlgrenska Academy at the University of Gothenburg, Sweden
| | - Roja Babazadeh
- Institute for Biomedicine, Sahlgrenska Academy, Centre for Ageing and Health-AgeCap, University of Gothenburg, Sweden.,Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden
| | - Thomas Nystrom
- Institute for Biomedicine, Sahlgrenska Academy, Centre for Ageing and Health-AgeCap, University of Gothenburg, Sweden
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117
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Long M, Kranjc T, Mysior MM, Simpson JC. RNA Interference Screening Identifies Novel Roles for RhoBTB1 and RhoBTB3 in Membrane Trafficking Events in Mammalian Cells. Cells 2020; 9:cells9051089. [PMID: 32354068 PMCID: PMC7291084 DOI: 10.3390/cells9051089] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 04/22/2020] [Accepted: 04/25/2020] [Indexed: 12/19/2022] Open
Abstract
In the endomembrane system of mammalian cells, membrane traffic processes require a high degree of regulation in order to ensure their specificity. The range of molecules that participate in trafficking events is truly vast, and much attention to date has been given to the Rab family of small GTPases. However, in recent years, a role in membrane traffic for members of the Rho GTPase family, in particular Cdc42, has emerged. This prompted us to develop and apply an image-based high-content screen, initially focussing on the Golgi complex, using RNA interference to systematically perturb each of the 21 Rho family members and assess their importance to the overall organisation of this organelle. Analysis of our data revealed previously unreported roles for two atypical Rho family members, RhoBTB1 and RhoBTB3, in membrane traffic events. We find that depletion of RhoBTB3 affects the morphology of the Golgi complex and causes changes in the trafficking speeds of carriers operating at the interface of the Golgi and endoplasmic reticulum. In addition, RhoBTB3 was found to be present on these carriers. Depletion of RhoBTB1 was also found to cause a disturbance to the Golgi architecture, however, this phenotype seems to be linked to endocytosis and retrograde traffic pathways. RhoBTB1 was found to be associated with early endosomal intermediates, and changes in the levels of RhoBTB1 not only caused profound changes to the organisation and distribution of endosomes and lysosomes, but also resulted in defects in the delivery of two different classes of cargo molecules to downstream compartments. Together, our data reveal new roles for these atypical Rho family members in the endomembrane system.
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118
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Small Molecule Targets TMED9 and Promotes Lysosomal Degradation to Reverse Proteinopathy. Cell 2020; 178:521-535.e23. [PMID: 31348885 DOI: 10.1016/j.cell.2019.07.002] [Citation(s) in RCA: 102] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 04/19/2019] [Accepted: 06/28/2019] [Indexed: 02/07/2023]
Abstract
Intracellular accumulation of misfolded proteins causes toxic proteinopathies, diseases without targeted therapies. Mucin 1 kidney disease (MKD) results from a frameshift mutation in the MUC1 gene (MUC1-fs). Here, we show that MKD is a toxic proteinopathy. Intracellular MUC1-fs accumulation activated the ATF6 unfolded protein response (UPR) branch. We identified BRD4780, a small molecule that clears MUC1-fs from patient cells, from kidneys of knockin mice and from patient kidney organoids. MUC1-fs is trapped in TMED9 cargo receptor-containing vesicles of the early secretory pathway. BRD4780 binds TMED9, releases MUC1-fs, and re-routes it for lysosomal degradation, an effect phenocopied by TMED9 deletion. Our findings reveal BRD4780 as a promising lead for the treatment of MKD and other toxic proteinopathies. Generally, we elucidate a novel mechanism for the entrapment of misfolded proteins by cargo receptors and a strategy for their release and anterograde trafficking to the lysosome.
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119
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Baron DM, Matheny T, Lin YC, Leszyk JD, Kenna K, Gall KV, Santos DP, Tischbein M, Funes S, Hayward LJ, Kiskinis E, Landers JE, Parker R, Shaffer SA, Bosco DA. Quantitative proteomics identifies proteins that resist translational repression and become dysregulated in ALS-FUS. Hum Mol Genet 2020; 28:2143-2160. [PMID: 30806671 DOI: 10.1093/hmg/ddz048] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Revised: 02/01/2019] [Accepted: 02/07/2019] [Indexed: 12/13/2022] Open
Abstract
Aberrant translational repression is a feature of multiple neurodegenerative diseases. The association between disease-linked proteins and stress granules further implicates impaired stress responses in neurodegeneration. However, our knowledge of the proteins that evade translational repression is incomplete. It is also unclear whether disease-linked proteins influence the proteome under conditions of translational repression. To address these questions, a quantitative proteomics approach was used to identify proteins that evade stress-induced translational repression in arsenite-treated cells expressing either wild-type or amyotrophic lateral sclerosis (ALS)-linked mutant FUS. This study revealed hundreds of proteins that are actively synthesized during stress-induced translational repression, irrespective of FUS genotype. In addition to proteins involved in RNA- and protein-processing, proteins associated with neurodegenerative diseases such as ALS were also actively synthesized during stress. Protein synthesis under stress was largely unperturbed by mutant FUS, although several proteins were found to be differentially expressed between mutant and control cells. One protein in particular, COPBI, was downregulated in mutant FUS-expressing cells under stress. COPBI is the beta subunit of the coat protein I (COPI), which is involved in Golgi to endoplasmic reticulum (ER) retrograde transport. Further investigation revealed reduced levels of other COPI subunit proteins and defects in COPBI-relatedprocesses in cells expressing mutant FUS. Even in the absence of stress, COPBI localization was altered in primary and human stem cell-derived neurons expressing ALS-linked FUS variants. Our results suggest that Golgi to ER retrograde transport may be important under conditions of stress and is perturbed upon the expression of disease-linked proteins such as FUS.
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Affiliation(s)
- Desiree M Baron
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Tyler Matheny
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO, USA
| | - Yen-Chen Lin
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, USA
| | - John D Leszyk
- Department of Biochemistry and Molecular Pharmacology, Worcester, MA, USA.,Mass Spectrometry Facility, University of Massachusetts Medical School, Shrewsbury, MA, USA
| | - Kevin Kenna
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, USA.,Department of Neurology, Brain Center Rudolf Magnus, University Medical Center Utrecht, University of Utrecht, Utrecht, The Netherlands
| | - Katherine V Gall
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, USA
| | - David P Santos
- The Ken & Ruth Davee Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.,Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Maeve Tischbein
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Salome Funes
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Lawrence J Hayward
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Evangelos Kiskinis
- The Ken & Ruth Davee Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.,Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - John E Landers
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Roy Parker
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO, USA.,Howard Hughes Medical Institute, Chevy Chase, MD, USA
| | - Scott A Shaffer
- Department of Biochemistry and Molecular Pharmacology, Worcester, MA, USA.,Mass Spectrometry Facility, University of Massachusetts Medical School, Shrewsbury, MA, USA
| | - Daryl A Bosco
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, USA.,Department of Biochemistry and Molecular Pharmacology, Worcester, MA, USA
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120
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EhRab21 associates with the Golgi apparatus in Entamoeba histolytica. Parasitol Res 2020; 119:1629-1640. [PMID: 32219551 DOI: 10.1007/s00436-020-06667-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Accepted: 03/15/2020] [Indexed: 01/12/2023]
Abstract
Rab proteins constitute the largest group of small GTPases and act as molecular switches in a wide variety of cellular processes, including proliferation, cytoskeleton assembly, and membrane trafficking in all eukaryotic cells. Rab21 has been reported in several eukaryotic cells, and our results suggest that in Entamoeba histolytica, Rab21 is involved in the vesicular traffic associated with the Golgi apparatus, where its function appears to be important to maintain the structure of this organelle. In addition, proteins such as Rab1A and Sec24, identified in this work associated with EhRab21, participate in the traffic of COPII vesicles from the endoplasmic reticulum to the Golgi apparatus and are necessary to maintain the latter's structure in human cells. In addition, EhRab21 probably affects the lysosome biogenesis, as indicated by an increase in the number of lysosomes as a result of the increase in EhRab21 activity. The participation of EhRab21 in the pathogenesis of amebiasis was verified on the amoebic liver abscess formation model using hamsters (Mesocricetus auratus), in which the overexpression of EhRab21Q64L (positive dominant mutant protein) decreased the number of liver abscesses formed.
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121
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Cui Y, Parashar S, Zahoor M, Needham PG, Mari M, Zhu M, Chen S, Ho HC, Reggiori F, Farhan H, Brodsky JL, Ferro-Novick S. A COPII subunit acts with an autophagy receptor to target endoplasmic reticulum for degradation. Science 2020; 365:53-60. [PMID: 31273116 DOI: 10.1126/science.aau9263] [Citation(s) in RCA: 107] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Revised: 04/13/2019] [Accepted: 06/12/2019] [Indexed: 12/21/2022]
Abstract
The COPII-cargo adaptor complex Lst1-Sec23 selectively sorts proteins into vesicles that bud from the endoplasmic reticulum (ER) and traffic to the Golgi. Improperly folded proteins are prevented from exiting the ER and are degraded. ER-phagy is an autophagic degradation pathway that uses ER-resident receptors. Working in yeast, we found an unexpected role for Lst1-Sec23 in ER-phagy that was independent from its function in secretion. Up-regulation of the stress-inducible ER-phagy receptor Atg40 induced the association of Lst1-Sec23 with Atg40 at distinct ER domains to package ER into autophagosomes. Lst1-mediated ER-phagy played a vital role in maintaining cellular homeostasis by preventing the accumulation of an aggregation-prone protein in the ER. Lst1 function appears to be conserved because its mammalian homolog, SEC24C, was also required for ER-phagy.
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Affiliation(s)
- Yixian Cui
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, CA 92093, USA
| | - Smriti Parashar
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, CA 92093, USA
| | - Muhammad Zahoor
- Institute of Basic Medical Sciences, Department of Molecular Medicine, University of Oslo, Sognsvannsveien 9, 0372 Oslo, Norway
| | - Patrick G Needham
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Muriel Mari
- Department of Biomedical Sciences of Cells and Systems, University of Groningen Medical Center, Groningen, Netherlands
| | - Ming Zhu
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, CA 92093, USA
| | - Shuliang Chen
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, CA 92093, USA
| | - Hsuan-Chung Ho
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, CA 92093, USA
| | - Fulvio Reggiori
- Department of Biomedical Sciences of Cells and Systems, University of Groningen Medical Center, Groningen, Netherlands
| | - Hesso Farhan
- Institute of Basic Medical Sciences, Department of Molecular Medicine, University of Oslo, Sognsvannsveien 9, 0372 Oslo, Norway
| | - Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Susan Ferro-Novick
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, CA 92093, USA.
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122
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Jeng CJ, Fu SJ, You CY, Peng YJ, Hsiao CT, Chen TY, Tang CY. Defective Gating and Proteostasis of Human ClC-1 Chloride Channel: Molecular Pathophysiology of Myotonia Congenita. Front Neurol 2020; 11:76. [PMID: 32117034 PMCID: PMC7026490 DOI: 10.3389/fneur.2020.00076] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Accepted: 01/22/2020] [Indexed: 01/17/2023] Open
Abstract
The voltage-dependent ClC-1 chloride channel, whose open probability increases with membrane potential depolarization, belongs to the superfamily of CLC channels/transporters. ClC-1 is almost exclusively expressed in skeletal muscles and is essential for stabilizing the excitability of muscle membranes. Elucidation of the molecular structures of human ClC-1 and several CLC homologs provides important insight to the gating and ion permeation mechanisms of this chloride channel. Mutations in the human CLCN1 gene, which encodes the ClC-1 channel, are associated with a hereditary skeletal muscle disease, myotonia congenita. Most disease-causing CLCN1 mutations lead to loss-of-function phenotypes in the ClC-1 channel and thus increase membrane excitability in skeletal muscles, consequently manifesting as delayed relaxations following voluntary muscle contractions in myotonic subjects. The inheritance pattern of myotonia congenita can be autosomal dominant (Thomsen type) or recessive (Becker type). To date over 200 myotonia-associated ClC-1 mutations have been identified, which are scattered throughout the entire protein sequence. The dominant inheritance pattern of some myotonia mutations may be explained by a dominant-negative effect on ClC-1 channel gating. For many other myotonia mutations, however, no clear relationship can be established between the inheritance pattern and the location of the mutation in the ClC-1 protein. Emerging evidence indicates that the effects of some mutations may entail impaired ClC-1 protein homeostasis (proteostasis). Proteostasis of membrane proteins comprises of biogenesis at the endoplasmic reticulum (ER), trafficking to the surface membrane, and protein turn-over at the plasma membrane. Maintenance of proteostasis requires the coordination of a wide variety of different molecular chaperones and protein quality control factors. A number of regulatory molecules have recently been shown to contribute to post-translational modifications of ClC-1 and play critical roles in the ER quality control, membrane trafficking, and peripheral quality control of this chloride channel. Further illumination of the mechanisms of ClC-1 proteostasis network will enhance our understanding of the molecular pathophysiology of myotonia congenita, and may also bring to light novel therapeutic targets for skeletal muscle dysfunction caused by myotonia and other pathological conditions.
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Affiliation(s)
- Chung-Jiuan Jeng
- Institute of Anatomy and Cell Biology, School of Medicine, National Yang-Ming University, Taipei, Taiwan.,Brain Research Center, National Yang-Ming University, Taipei, Taiwan
| | - Ssu-Ju Fu
- Institute of Anatomy and Cell Biology, School of Medicine, National Yang-Ming University, Taipei, Taiwan.,Department of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Chia-Ying You
- Department of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Yi-Jheng Peng
- Department of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Cheng-Tsung Hsiao
- Department of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan.,Department of Neurology, Taipei Veterans General Hospital, Taipei, Taiwan
| | - Tsung-Yu Chen
- Center for Neuroscience, University of California, Davis, Davis, CA, United States
| | - Chih-Yung Tang
- Department of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan.,College of Medicine, Graduate Institute of Brain and Mind Sciences, National Taiwan University, Taipei, Taiwan
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123
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Trowitzsch S, Tampé R. Multifunctional Chaperone and Quality Control Complexes in Adaptive Immunity. Annu Rev Biophys 2020; 49:135-161. [PMID: 32004089 DOI: 10.1146/annurev-biophys-121219-081643] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The fundamental process of adaptive immunity relies on the differentiation of self from nonself. Nucleated cells are continuously monitored by effector cells of the immune system, which police the peptide status presented via cell surface molecules. Recent integrative structural approaches have provided insights toward our understanding of how sophisticated cellular machineries shape such hierarchical immune surveillance. Biophysical and structural achievements were invaluable for defining the interconnection of many key factors during antigen processing and presentation, and helped to solve several conundrums that persisted for many years. In this review, we illuminate the numerous quality control machineries involved in different steps during the maturation of major histocompatibility complex class I (MHC I) proteins, from their synthesis in the endoplasmic reticulum to folding and trafficking via the secretory pathway, optimization of antigenic cargo, final release to the cell surface, and engagement with their cognate receptors on cytotoxic T lymphocytes.
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Affiliation(s)
- Simon Trowitzsch
- Institute of Biochemistry, Biocenter, Goethe University Frankfurt, 60438 Frankfurt am Main, Germany; ,
| | - Robert Tampé
- Institute of Biochemistry, Biocenter, Goethe University Frankfurt, 60438 Frankfurt am Main, Germany; ,
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124
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Beese CJ, Brynjólfsdóttir SH, Frankel LB. Selective Autophagy of the Protein Homeostasis Machinery: Ribophagy, Proteaphagy and ER-Phagy. Front Cell Dev Biol 2020; 7:373. [PMID: 32039200 PMCID: PMC6985035 DOI: 10.3389/fcell.2019.00373] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Accepted: 12/16/2019] [Indexed: 01/06/2023] Open
Abstract
The eukaryotic cell has developed intricate machineries that monitor and maintain proteome homeostasis in order to ensure cellular functionality. This involves the carefully coordinated balance between protein synthesis and degradation pathways, which are dynamically regulated in order to meet the constantly changing demands of the cell. Ribosomes, together with the endoplasmic reticulum (ER), are the key drivers of protein synthesis, folding, maturation and sorting, while the proteasome plays a pivotal role in terminating the existence of thousands of proteins that are misfolded, damaged or otherwise obsolete. The synthesis, structure and function of these dedicated machines has been studied for decades, however, much less is understood about the mechanisms that control and execute their own turnover. Autophagy, an evolutionarily conserved catabolic pathway, mediates degradation of a large variety of cytosolic substrates, ranging from single proteins to entire organelles or multi-subunit macromolecular complexes. In this review, we focus on selective autophagy of three key components of the protein homeostasis machinery: ribosomes, ER and proteasomes, through the selective autophagy pathways of ribophagy, ER-phagy, and proteaphagy. We discuss newly discovered mechanisms for the selective clearance of these substrates, which are often stress-dependent and involve specialized signals for cargo recognition by a growing number of receptors. We further discuss the interplay between these pathways and their biological impact on key aspects of proteome homeostasis and cellular function in health and disease.
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Affiliation(s)
- Carsten J Beese
- Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark.,Danish Cancer Society Research Center, Copenhagen, Denmark
| | | | - Lisa B Frankel
- Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark.,Danish Cancer Society Research Center, Copenhagen, Denmark
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125
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Cavalli G, Cenci S. Autophagy and Protein Secretion. J Mol Biol 2020; 432:2525-2545. [PMID: 31972172 DOI: 10.1016/j.jmb.2020.01.015] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 01/08/2020] [Accepted: 01/12/2020] [Indexed: 12/13/2022]
Abstract
Autophagy - conventional for macroautophagy - is a major recycling strategy that ensures cellular homeostasis through the selective engulfment of cytoplasmic supramolecular cargos in double membrane vesicles and their rapid dispatch to the lysosome for digestion. As autophagy operates in the cytoplasm, its interference with secretory proteins, that is, proteins destined to the plasma membrane or the extracellular space, generally synthesized and routed within the endoplasmic reticulum (ER), has been relatively overlooked in the past. However, mounting evidence reveals that autophagy in fact heavily regulates protein secretion through diverse mechanisms. First, autophagy is closely involved in the unconventional secretion of leaderless proteins, a pool of proteins destined extracellularly, but lacking an ER-targeted leader sequence, and thus manufactured in the cytosol. Autophagy-related (ATG) genes now appear instrumental to the underlying pathways, hence the recently coined concept of secretory autophagy, or better ATG gene-dependent secretion. Indeed, ATG genes regulate unconventional protein secretion at multiple levels, ranging from intracellular inflammatory signaling, for example, through the control of mitochondrial health and inflammasome activity, to trafficking of leaderless proteins. Moreover, perhaps less expectedly, autophagy also participates in the control of conventional secretion, intersecting the secretory apparatus at multiple points, though with surprising differences among professional secretory cell types that disclose remarkable and unpredicted specificity. This review synopsizes the multiple mechanisms whereby autophagy interfaces with conventional and unconventional protein secretory pathways and discusses the relative teleology. Altogether, the diverse controls exerted on protein secretion broaden and deepen the homeostatic significance of autophagy within the cell.
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Affiliation(s)
- Giulio Cavalli
- Unit of Immunology, Rheumatology, Allergy and Rare Diseases, Ospedale San Raffaele, Milano, Italy; Vita-Salute San Raffaele University, Milano, Italy
| | - Simone Cenci
- Vita-Salute San Raffaele University, Milano, Italy; Unit of Age Related Diseases, Division of Genetics and Cell Biology, Ospedale San Raffaele, Milano, Italy.
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126
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Abstract
Defects in membrane trafficking are hallmarks of neurodegeneration. Rab GTPases are key regulators of membrane trafficking. Alterations of Rab GTPases, or the membrane compartments they regulate, are associated with virtually all neuronal activities in health and disease. The observation that many Rab GTPases are associated with neurodegeneration has proven a challenge in the quest for cause and effect. Neurodegeneration can be a direct consequence of a defect in membrane trafficking. Alternatively, changes in membrane trafficking may be secondary consequences or cellular responses. The secondary consequences and cellular responses, in turn, may protect, represent inconsequential correlates or function as drivers of pathology. Here, we attempt to disentangle the different roles of membrane trafficking in neurodegeneration by focusing on selected associations with Alzheimer’s disease, Parkinson’s disease, Huntington’s disease and selected neuropathies. We provide an overview of current knowledge on Rab GTPase functions in neurons and review the associations of Rab GTPases with neurodegeneration with respect to the following classifications: primary cause, secondary cause driving pathology or secondary correlate. This analysis is devised to aid the interpretation of frequently observed membrane trafficking defects in neurodegeneration and facilitate the identification of true causes of pathology.
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127
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Affiliation(s)
- James E. Rothman
- Department of Cell Biology Yale University School of Medicine New Haven CT USA
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128
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Ran pathway-independent regulation of mitotic Golgi disassembly by Importin-α. Nat Commun 2019; 10:4307. [PMID: 31541088 PMCID: PMC6754406 DOI: 10.1038/s41467-019-12207-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Accepted: 08/22/2019] [Indexed: 01/24/2023] Open
Abstract
To facilitate proper mitotic cell partitioning, the Golgi disassembles by suppressing vesicle fusion. However, the underlying mechanism has not been characterized previously. Here, we report a Ran pathway-independent attenuation mechanism that allows Importin-α (a nuclear transport factor) to suppress the vesicle fusion mediated by p115 (a vesicular tethering factor) and is required for mitotic Golgi disassembly. We demonstrate that Importin-α directly competes with p115 for interaction with the Golgi protein GM130. This interaction, promoted by a phosphate moiety on GM130, is independent of Importin-β and Ran. A GM130 K34A mutant, in which the Importin-α-GM130 interaction is specifically disrupted, exhibited abundant Golgi puncta during metaphase. Importantly, a mutant showing enhanced p115-GM130 interaction presented proliferative defects and G2/M arrest, demonstrating that Importin-α-GM130 binding modulates the Golgi disassembly that governs mitotic progression. Our findings illuminate that the Ran and kinase-phosphatase pathways regulate multiple aspects of mitosis coordinated by Importin-α (e.g. spindle assembly, Golgi disassembly). Golgi disassembly is required for mitosis and occurs by vesicle fusion suppression, although the mechanism is unclear. Here, Chang et al. show, with quantitative analyses and crystallography, that Importin-α regulates this process by blocking GM130-p115 interactions in a Ran pathway-independent way.
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129
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Bräuer P, Parker JL, Gerondopoulos A, Zimmermann I, Seeger MA, Barr FA, Newstead S. Structural basis for pH-dependent retrieval of ER proteins from the Golgi by the KDEL receptor. Science 2019; 363:1103-1107. [PMID: 30846601 DOI: 10.1126/science.aaw2859] [Citation(s) in RCA: 85] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Accepted: 02/13/2019] [Indexed: 11/02/2022]
Abstract
Selective export and retrieval of proteins between the endoplasmic reticulum (ER) and Golgi apparatus is indispensable for eukaryotic cell function. An essential step in the retrieval of ER luminal proteins from the Golgi is the pH-dependent recognition of a carboxyl-terminal Lys-Asp-Glu-Leu (KDEL) signal by the KDEL receptor. Here, we present crystal structures of the chicken KDEL receptor in the apo ER state, KDEL-bound Golgi state, and in complex with an antagonistic synthetic nanobody (sybody). These structures show a transporter-like architecture that undergoes conformational changes upon KDEL binding and reveal a pH-dependent interaction network crucial for recognition of the carboxyl terminus of the KDEL signal. Complementary in vitro binding and in vivo cell localization data explain how these features create a pH-dependent retrieval system in the secretory pathway.
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Affiliation(s)
- Philipp Bräuer
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Joanne L Parker
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Andreas Gerondopoulos
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Iwan Zimmermann
- Institute of Medical Microbiology, University of Zurich, 8006 Zurich, Switzerland
| | - Markus A Seeger
- Institute of Medical Microbiology, University of Zurich, 8006 Zurich, Switzerland
| | - Francis A Barr
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
| | - Simon Newstead
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
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130
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Affiliation(s)
- J Paul Luzio
- Cambridge Institute for Medical Research and Department of Clinical Biochemistry, University of Cambridge School of Clinical Medicine, Cambridge, UK.
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131
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Anelli T, Panina-Bordignon P. How to Avoid a No-Deal ER Exit. Cells 2019; 8:cells8091051. [PMID: 31500301 PMCID: PMC6769657 DOI: 10.3390/cells8091051] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2019] [Revised: 08/28/2019] [Accepted: 09/06/2019] [Indexed: 01/01/2023] Open
Abstract
Efficiency and fidelity of protein secretion are achieved thanks to the presence of different steps, located sequentially in time and space along the secretory compartment, controlling protein folding and maturation. After entering into the endoplasmic reticulum (ER), secretory proteins attain their native structure thanks to specific chaperones and enzymes. Only correctly folded molecules are allowed by quality control (QC) mechanisms to leave the ER and proceed to downstream compartments. Proteins that cannot fold properly are instead retained in the ER to be finally destined to proteasomal degradation. Exiting from the ER requires, in most cases, the use of coated vesicles, departing at the ER exit sites, which will fuse with the Golgi compartment, thus releasing their cargoes. Protein accumulation in the ER can be caused by a too stringent QC or by ineffective transport: these situations could be deleterious for the organism, due to the loss of the secreted protein, and to the cell itself, because of abnormal increase of protein concentration in the ER. In both cases, diseases can arise. In this review, we will describe the pathophysiology of protein folding and transport between the ER and the Golgi compartment.
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Affiliation(s)
- Tiziana Anelli
- Vita-Salute San Raffaele University, 20132 Milan, Italy.
- Division of Genetics and Cell Biology, IRCCS Ospedale San Raffaele, 20132 Milan, Italy.
| | - Paola Panina-Bordignon
- Vita-Salute San Raffaele University, 20132 Milan, Italy.
- Division of Neuroscience, IRCCS Ospedale San Raffaele, 20132 Milan, Italy.
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132
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Moshal KS, Roder K, Kabakov AY, Werdich AA, Yi-Eng Chiang D, Turan NN, Xie A, Kim TY, Cooper LL, Lu Y, Zhong M, Li W, Terentyev D, Choi BR, Karma A, MacRae CA, Koren G. LITAF (Lipopolysaccharide-Induced Tumor Necrosis Factor) Regulates Cardiac L-Type Calcium Channels by Modulating NEDD (Neural Precursor Cell Expressed Developmentally Downregulated Protein) 4-1 Ubiquitin Ligase. CIRCULATION. GENOMIC AND PRECISION MEDICINE 2019; 12:407-420. [PMID: 31462068 PMCID: PMC6750970 DOI: 10.1161/circgen.119.002641] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
BACKGROUND The turnover of cardiac ion channels underlying action potential duration is regulated by ubiquitination. Genome-wide association studies of QT interval identified several single-nucleotide polymorphisms located in or near genes involved in protein ubiquitination. A genetic variant upstream of LITAF (lipopolysaccharide-induced tumor necrosis factor) gene prompted us to determine its role in modulating cardiac excitation. METHODS Optical mapping was performed in zebrafish hearts to determine Ca2+ transients. Live-cell confocal calcium imaging was performed on adult rabbit cardiomyocytes to determine intracellular Ca2+handling. L-type calcium channel (LTCC) current (ICa,L) was measured using whole-cell recording. To study the effect of LITAF on Cav1.2 (L-type voltage-gated calcium channel 1.2) channel expression, surface biotinylation, and Westerns were performed. LITAF interactions were studied using coimmunoprecipitation and in situ proximity ligation assay. RESULTS LITAF knockdown in zebrafish resulted in a robust increase in calcium transients. Overexpressed LITAF in 3-week-old rabbit cardiomyocytes resulted in a decrease in ICa,L and Cavα1c abundance, whereas LITAF knockdown increased ICa,L and Cavα1c protein. LITAF-overexpressing decreases calcium transients in adult rabbit cardiomyocytes, which was associated with lower Cavα1c levels. In tsA201 cells, overexpressed LITAF downregulated total and surface pools of Cavα1c via increased Cavα1c ubiquitination and its subsequent lysosomal degradation. We observed colocalization between LITAF and LTCC in tsA201 and cardiomyocytes. In tsA201, NEDD (neural precursor cell expressed developmentally downregulated protein) 4-1, but not its catalytically inactive form NEDD4-1-C867A, increased Cavα1c ubiquitination. Cavα1c ubiquitination was further increased by coexpressed LITAF and NEDD4-1 but not NEDD4-1-C867A. NEDD4-1 knockdown abolished the negative effect of LITAF on ICa,L and Cavα1c levels in 3-week-old rabbit cardiomyocytes. Computer simulations demonstrated that a decrease of ICa,L current associated with LITAF overexpression simultaneously shortened action potential duration and decreased calcium transients in rabbit cardiomyocytes. CONCLUSIONS LITAF acts as an adaptor protein promoting NEDD4-1-mediated ubiquitination and subsequent degradation of LTCC, thereby controlling LTCC membrane levels and function and thus cardiac excitation.
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Affiliation(s)
- Karni S. Moshal
- Cardiovascular Research Center, Division of Cardiology, Dept of Medicine, Rhode Island Hospital, The Warren Alpert Medical School, Brown Univ, Providence, RI
| | - Karim Roder
- Cardiovascular Research Center, Division of Cardiology, Dept of Medicine, Rhode Island Hospital, The Warren Alpert Medical School, Brown Univ, Providence, RI
| | - Anatoli Y. Kabakov
- Cardiovascular Research Center, Division of Cardiology, Dept of Medicine, Rhode Island Hospital, The Warren Alpert Medical School, Brown Univ, Providence, RI
| | - Andreas A. Werdich
- Cardiovascular Division, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA
| | - David Yi-Eng Chiang
- Cardiovascular Division, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA
| | - Nilüfer N. Turan
- Cardiovascular Research Center, Division of Cardiology, Dept of Medicine, Rhode Island Hospital, The Warren Alpert Medical School, Brown Univ, Providence, RI
| | - An Xie
- Cardiovascular Research Center, Division of Cardiology, Dept of Medicine, Rhode Island Hospital, The Warren Alpert Medical School, Brown Univ, Providence, RI
| | - Tae Yun Kim
- Cardiovascular Research Center, Division of Cardiology, Dept of Medicine, Rhode Island Hospital, The Warren Alpert Medical School, Brown Univ, Providence, RI
| | | | - Yichun Lu
- Cardiovascular Research Center, Division of Cardiology, Dept of Medicine, Rhode Island Hospital, The Warren Alpert Medical School, Brown Univ, Providence, RI
| | - Mingwang Zhong
- Physics Dept & Center for Interdisciplinary Research in Complex Systems, Northeastern Univ, Boston, MA
| | - Weiyan Li
- Cardiovascular Research Center, Division of Cardiology, Dept of Medicine, Rhode Island Hospital, The Warren Alpert Medical School, Brown Univ, Providence, RI
| | - Dmitry Terentyev
- Cardiovascular Research Center, Division of Cardiology, Dept of Medicine, Rhode Island Hospital, The Warren Alpert Medical School, Brown Univ, Providence, RI
| | - Bum-Rak Choi
- Cardiovascular Research Center, Division of Cardiology, Dept of Medicine, Rhode Island Hospital, The Warren Alpert Medical School, Brown Univ, Providence, RI
| | - Alain Karma
- Physics Dept & Center for Interdisciplinary Research in Complex Systems, Northeastern Univ, Boston, MA
| | - Calum A. MacRae
- Cardiovascular Division, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA
| | - Gideon Koren
- Cardiovascular Research Center, Division of Cardiology, Dept of Medicine, Rhode Island Hospital, The Warren Alpert Medical School, Brown Univ, Providence, RI
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Erv14 cargo receptor participates in regulation of plasma-membrane potential, intracellular pH and potassium homeostasis via its interaction with K+-specific transporters Trk1 and Tok1. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2019; 1866:1376-1388. [DOI: 10.1016/j.bbamcr.2019.05.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 05/21/2019] [Accepted: 05/23/2019] [Indexed: 12/31/2022]
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134
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van Leeuwen W, Rabouille C. Cellular stress leads to the formation of membraneless stress assemblies in eukaryotic cells. Traffic 2019; 20:623-638. [PMID: 31152627 PMCID: PMC6771618 DOI: 10.1111/tra.12669] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 05/10/2019] [Accepted: 05/30/2019] [Indexed: 12/28/2022]
Abstract
In cells at steady state, two forms of cell compartmentalization coexist: membrane-bound organelles and phase-separated membraneless organelles that are present in both the nucleus and the cytoplasm. Strikingly, cellular stress is a strong inducer of the reversible membraneless compartments referred to as stress assemblies. Stress assemblies play key roles in survival during cell stress and in thriving of cells upon stress relief. The two best studied stress assemblies are the RNA-based processing-bodies (P-bodies) and stress granules that form in response to oxidative, endoplasmic reticulum (ER), osmotic and nutrient stress as well as many others. Interestingly, P-bodies and stress granules are heterogeneous with respect to both the pathways that lead to their formation and their protein and RNA content. Furthermore, in yeast and Drosophila, nutrient stress also leads to the formation of many other types of prosurvival cytoplasmic stress assemblies, such as metabolic enzymes foci, proteasome storage granules, EIF2B bodies, U-bodies and Sec bodies, some of which are not RNA-based. Nutrient stress leads to a drop in cytoplasmic pH, which combined with posttranslational modifications of granule contents, induces phase separation.
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Affiliation(s)
- Wessel van Leeuwen
- Hubrecht Institute of the Royal Netherlands Academy of Arts and Sciencesand University Medical Center UtrechtUtrechtthe Netherlands
| | - Catherine Rabouille
- Hubrecht Institute of the Royal Netherlands Academy of Arts and Sciencesand University Medical Center UtrechtUtrechtthe Netherlands
- Department of Biomedical Science of Cells and SystemsUniversity Medical Center GroningenGroningenthe Netherlands
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135
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Zhang C, Rabouille C. Membrane-Bound Meet Membraneless in Health and Disease. Cells 2019; 8:cells8091000. [PMID: 31470564 PMCID: PMC6770257 DOI: 10.3390/cells8091000] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 08/26/2019] [Accepted: 08/27/2019] [Indexed: 12/12/2022] Open
Abstract
Membraneless organelles (MLOs) are defined as cellular structures that are not sealed by a lipidic membrane and are shown to form by phase separation. They exist in both the nucleus and the cytoplasm that is also heavily populated by numerous membrane-bound organelles. Even though the name membraneless suggests that MLOs are free of membrane, both membrane and factors regulating membrane trafficking steps are emerging as important components of MLO formation and function. As a result, we name them biocondensates. In this review, we examine the relationships between biocondensates and membrane. First, inhibition of membrane trafficking in the early secretory pathway leads to the formation of biocondensates (P-bodies and Sec bodies). In the same vein, stress granules have a complex relationship with the cyto-nuclear transport machinery. Second, membrane contributes to the regulated formation of phase separation in the cells and we will present examples including clustering at the plasma membrane and at the synapse. Finally, the whole cell appears to transit from an interphase phase-separated state to a mitotic diffuse state in a DYRK3 dependent manner. This firmly establishes a crosstalk between the two types of cell organization that will need to be further explored.
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Affiliation(s)
- Chujun Zhang
- Hubrecht Institute of the Royal Netherlands Academy of Arts and Sciences, and University Medical Center Utrecht, 3584 CT Utrecht, The Netherlands
| | - Catherine Rabouille
- Hubrecht Institute of the Royal Netherlands Academy of Arts and Sciences, and University Medical Center Utrecht, 3584 CT Utrecht, The Netherlands.
- Department of Biomedical Science of Cells and Systems, University Medical Center Groningen, 9713 AV Groningen, The Netherlands.
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136
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De Leonibus C, Cinque L, Settembre C. Emerging lysosomal pathways for quality control at the endoplasmic reticulum. FEBS Lett 2019; 593:2319-2329. [PMID: 31388984 DOI: 10.1002/1873-3468.13571] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Revised: 07/30/2019] [Accepted: 08/02/2019] [Indexed: 01/01/2023]
Abstract
Protein misfolding occurring in the endoplasmic reticulum (ER) might eventually lead to aggregation and cellular distress, and is a primary pathogenic mechanism in multiple human disorders. Mammals have developed evolutionary-conserved quality control mechanisms at the level of the ER. The best characterized is the ER-associated degradation (ERAD) pathway, through which misfolded proteins translocate from the ER to the cytosol and are subsequently proteasomally degraded. However, increasing evidence indicates that additional quality control mechanisms apply for misfolded ER clients that are not eligible for ERAD. This review focuses on the alternative, ERAD-independent, mechanisms of clearance of misfolded polypeptides from the ER. These processes, collectively referred to as ER-to-lysosome-associated degradation, involve ER-phagy, microautophagy or vesicular transport. The identification of the underlying molecular mechanisms is particularly important for developing new therapeutic approaches for human diseases associated with protein aggregate formation.
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Affiliation(s)
| | - Laura Cinque
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, Italy
| | - Carmine Settembre
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, Italy.,Department of Medical and Translational Science, University of Naples "Federico II", Italy
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137
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Endoplasmic Reticulum Export of GPI-Anchored Proteins. Int J Mol Sci 2019; 20:ijms20143506. [PMID: 31319476 PMCID: PMC6678536 DOI: 10.3390/ijms20143506] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Revised: 07/07/2019] [Accepted: 07/15/2019] [Indexed: 12/12/2022] Open
Abstract
Protein export from the endoplasmic reticulum (ER) is an essential process in all eukaryotes driven by the cytosolic coat complex COPII, which forms vesicles at ER exit sites for transport of correctly assembled secretory cargo to the Golgi apparatus. The COPII machinery must adapt to the existing wide variety of different types of cargo proteins and to different cellular needs for cargo secretion. The study of the ER export of glycosylphosphatidylinositol (GPI)-anchored proteins (GPI-APs), a special glycolipid-linked class of cell surface proteins, is contributing to address these key issues. Due to their special biophysical properties, GPI-APs use a specialized COPII machinery to be exported from the ER and their processing and maturation has been recently shown to actively regulate COPII function. In this review, we discuss the regulatory mechanisms by which GPI-APs are assembled and selectively exported from the ER.
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138
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Baïsse B, Spertini C, Galisson F, Smirnova T, Spertini O. The function of P-selectin glycoprotein ligand-1 is conserved from ancestral fishes to mammals. J Leukoc Biol 2019; 106:1271-1283. [PMID: 31302947 DOI: 10.1002/jlb.2a0818-327rr] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Revised: 07/03/2019] [Accepted: 07/05/2019] [Indexed: 02/07/2023] Open
Abstract
PSGL-1 is a mucin-like glycoprotein that supports, in mammals, leukocyte rolling on selectins. However, we have limited knowledge whether its function is conserved in non-mammals and how its structure adapted during evolution. To identify conserved amino acid sequences required for selectin binding, we performed multiple alignments of PSGL-1 sequences from 18 mammals, 4 birds, 3 reptiles, 1 amphibian, and 15 fishes. The amino-terminal T[D/E]PP[D/E] motif, which identifies in mammals a core-2 O-glycosylated threonine required for selectin-binding, is partially conserved in some fishes (e.g., T. rubripes) and birds (e.g., G. gallus), however, most non-mammals do not display it. The sulfated tyrosine residues of human PSGL-1, which bind L- and P-selectin, are not observed in non-mammals, suggesting that they are dispensable for selectin-binding or that other amino acids play their role. A mucin-like domain is present in all species. Interestingly, the alignment of cytoplasmic sequences of non-mammals reveals the conservation of ezrin/radixin/moesin binding site and two new motifs (M1 and M2). To examine the conservation of PSGL-1 function, we cloned PSGL-1 cDNA sequences of zebrafish and fugu, and established their cross-reactivity with human selectins under flow conditions. Importantly, deleting the well-conserved M1 motif strongly decreased PSGL-1 expression at leukocyte surface and induced retention of the precursor molecule in the endoplasmic reticulum, indicating that M1 motif provides a signal required to export PSGL-1 precursors to the Golgi complex. These data show for the first time the conservation of PSGL-1 function from fishes to mammals and reveal the function of a new motif.
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Affiliation(s)
- Bénédicte Baïsse
- Service and Central Laboratory of Hematology, Centre Hospitalier Universitaire Vaudois and University of Lausanne, Lausanne, Switzerland
| | - Caroline Spertini
- Service and Central Laboratory of Hematology, Centre Hospitalier Universitaire Vaudois and University of Lausanne, Lausanne, Switzerland
| | - Frédérique Galisson
- Service and Central Laboratory of Hematology, Centre Hospitalier Universitaire Vaudois and University of Lausanne, Lausanne, Switzerland
| | - Tatiana Smirnova
- Service and Central Laboratory of Hematology, Centre Hospitalier Universitaire Vaudois and University of Lausanne, Lausanne, Switzerland
| | - Olivier Spertini
- Service and Central Laboratory of Hematology, Centre Hospitalier Universitaire Vaudois and University of Lausanne, Lausanne, Switzerland
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Henriques SF, Gicquel E, Marsolier J, Richard I. Functional and cellular localization diversity associated with Fukutin-related protein patient genetic variants. Hum Mutat 2019; 40:1874-1885. [PMID: 31268217 DOI: 10.1002/humu.23827] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2018] [Revised: 05/14/2019] [Accepted: 05/29/2019] [Indexed: 11/05/2022]
Abstract
Genetic variants in Fukutin-related protein (FKRP), an essential enzyme of the glycosylation pathway of α-dystroglycan, can lead to pathologies with different severities affecting the eye, brain, and muscle tissues. Here, we generate an in vitro cellular system to characterize the cellular localization as well as the functional potential of the most common FKRP patient missense mutations. We observe a differential retention in the endoplasmic reticulum (ER), the indication of misfolded proteins. We find data supporting that mutant protein able to overcome this ER-retention through overexpression present functional levels comparable to the wild-type. We also identify a specific region in FKRP protein localized between residues 300 and 321 in which genetic variants found in patients lead to correctly localized proteins but which are nevertheless functionally impaired or catalytically dead in our model, indicating that this particular region might be important for the enzymatic activity of FKRP within the Golgi. Our system thus allows the functional testing of patient-specific mutant proteins and the identification of candidate mutants to be further explored with the aim of finding pharmacological treatments targeting the protein quality control system.
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Affiliation(s)
- Sara F Henriques
- INTEGRARE Research Unit, UMR951, Genethon, INSERM, Univ. Paris-Saclay, Evry, F-91002, France
| | - Evelyne Gicquel
- INTEGRARE Research Unit, UMR951, Genethon, INSERM, Univ. Paris-Saclay, Evry, F-91002, France
| | - Justine Marsolier
- INTEGRARE Research Unit, UMR951, Genethon, INSERM, Univ. Paris-Saclay, Evry, F-91002, France
| | - Isabelle Richard
- INTEGRARE Research Unit, UMR951, Genethon, INSERM, Univ. Paris-Saclay, Evry, F-91002, France
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140
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Atlastin-mediated membrane tethering is critical for cargo mobility and exit from the endoplasmic reticulum. Proc Natl Acad Sci U S A 2019; 116:14029-14038. [PMID: 31239341 PMCID: PMC6628656 DOI: 10.1073/pnas.1908409116] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
In the early secretory pathway, newly synthesized proteins undergo folding and modifications and then leave the ER through COPII-coated vesicles. How these processes are coordinated and maintained are important but mostly unclear. We show here that ATL, a GTPase that connects ER tubules, controls ER protein mobility and regulates cargo packaging and coat assembly of COPII vesicles. The tethering and fusion activity by ATL likely maintains tension and other necessary parameters for COPII formation in ER membranes. These findings reveal a role of ER shaping in the early secretory pathway and provide insight into behaviors of ER exportation. Endoplasmic reticulum (ER) membrane junctions are formed by the dynamin-like GTPase atlastin (ATL). Deletion of ATL results in long unbranched ER tubules in cells, and mutation of human ATL1 is linked to hereditary spastic paraplegia. Here, we demonstrate that COPII formation is drastically decreased in the periphery of ATL-deleted cells. ER export of cargo proteins becomes defective; ER exit site initiation is not affected, but many of the sites fail to recruit COPII subunits. The efficiency of cargo packaging into COPII vesicles is significantly reduced in cells lacking ATLs, or when the ER is transiently fragmented. Cargo is less mobile in the ER in the absence of ATL, but the cargo mobility and COPII formation can be restored by ATL R77A, which is capable of tethering, but not fusing, ER tubules. These findings suggest that the generation of ER junctions by ATL plays a critical role in maintaining the necessary mobility of ER contents to allow efficient packaging of cargo proteins into COPII vesicles.
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141
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Ernst AM, Toomre D, Bogan JS. Acylation - A New Means to Control Traffic Through the Golgi. Front Cell Dev Biol 2019; 7:109. [PMID: 31245373 PMCID: PMC6582194 DOI: 10.3389/fcell.2019.00109] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Accepted: 05/29/2019] [Indexed: 12/22/2022] Open
Abstract
The Golgi is well known to act as center for modification and sorting of proteins for secretion and delivery to other organelles. A key sorting step occurs at the trans-Golgi network and is mediated by protein adapters. However, recent data indicate that sorting also occurs much earlier, at the cis-Golgi, and uses lipid acylation as a novel means to regulate anterograde flux. Here, we examine an emerging role of S-palmitoylation/acylation as a mechanism to regulate anterograde routing. We discuss the critical Golgi-localized DHHC S-palmitoyltransferase enzymes that orchestrate this lipid modification, as well as their diverse protein clients (e.g., MAP6, SNAP25, CSP, LAT, β-adrenergic receptors, GABA receptors, and GLUT4 glucose transporters). Critically, for integral membrane proteins, S-acylation can act as new a “self-sorting” signal to concentrate these cargoes in rims of Golgi cisternae, and to promote their rapid traffic through the Golgi or, potentially, to bypass the Golgi. We discuss this mechanism and examine its potential relevance to human physiology and disease, including diabetes and neurodegenerative diseases.
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Affiliation(s)
- Andreas M Ernst
- Department of Cell Biology, Yale School of Medicine, Yale University, New Haven, CT, United States
| | - Derek Toomre
- Department of Cell Biology, Yale School of Medicine, Yale University, New Haven, CT, United States
| | - Jonathan S Bogan
- Department of Cell Biology, Yale School of Medicine, Yale University, New Haven, CT, United States.,Section of Endocrinology and Metabolism, Department of Internal Medicine, Yale School of Medicine, Yale University, New Haven, CT, United States
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142
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Schoberer J, Liebminger E, Vavra U, Veit C, Grünwald-Gruber C, Altmann F, Botchway SW, Strasser R. The Golgi Localization of GnTI Requires a Polar Amino Acid Residue within Its Transmembrane Domain. PLANT PHYSIOLOGY 2019; 180:859-873. [PMID: 30971450 PMCID: PMC6548254 DOI: 10.1104/pp.19.00310] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Accepted: 04/03/2019] [Indexed: 05/12/2023]
Abstract
The Golgi apparatus consists of stacked cisternae filled with enzymes that facilitate the sequential and highly controlled modification of glycans from proteins that transit through the organelle. Although the glycan processing pathways have been extensively studied, the underlying mechanisms that concentrate Golgi-resident glycosyltransferases and glycosidases in distinct Golgi compartments are poorly understood. The single-pass transmembrane domain (TMD) of n-acetylglucosaminyltransferaseI (GnTI) accounts for its steady-state distribution in the cis/medial-Golgi. Here, we investigated the contribution of individual amino acid residues within the TMD of Arabidopsis (Arabidopsis thaliana) and Nicotiana tabacum GnTI toward Golgi localization and n-glycan processing. Conserved sequence motifs within the TMD were replaced with those from the established trans-Golgi enzyme α2,6-sialyltransferase and site-directed mutagenesis was used to exchange individual amino acid residues. Subsequent subcellular localization of fluorescent fusion proteins and n-glycan profiling revealed that a conserved Gln residue in the GnTI TMD is essential for its cis/medial-Golgi localization. Substitution of the crucial Gln residue with other amino acids resulted in mislocalization to the vacuole and impaired n-glycan processing in vivo. Our results suggest that sequence-specific features of the GnTI TMD are required for its interaction with a Golgi-resident adaptor protein or a specific lipid environment that likely promotes coat protein complexI-mediated retrograde transport, thus maintaining the steady-state distribution of GnTI in the cis/medial-Golgi of plants.
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Affiliation(s)
- Jennifer Schoberer
- Department of Applied Genetics and Cell Biology, University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
| | - Eva Liebminger
- Department of Applied Genetics and Cell Biology, University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
| | - Ulrike Vavra
- Department of Applied Genetics and Cell Biology, University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
| | - Christiane Veit
- Department of Applied Genetics and Cell Biology, University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
| | - Clemens Grünwald-Gruber
- Department of Chemistry, University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
| | - Friedrich Altmann
- Department of Chemistry, University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
| | - Stanley W Botchway
- Research Complex at Harwell, Central Laser Facility, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell-Oxford, Didcot OX11 0QX, United Kingdom
| | - Richard Strasser
- Department of Applied Genetics and Cell Biology, University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
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143
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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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144
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Porcine Epidemic Diarrhea Virus (PEDV) ORF3 Interactome Reveals Inhibition of Virus Replication by Cellular VPS36 Protein. Viruses 2019; 11:v11040382. [PMID: 31022991 PMCID: PMC6521123 DOI: 10.3390/v11040382] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 04/19/2019] [Accepted: 04/23/2019] [Indexed: 12/21/2022] Open
Abstract
The accessory protein ORF3 of porcine epidemic diarrhea virus (PEDV) has been proposed to play a key role in virus replication. However, our understanding of its function regarding virus and host interaction is still limited. In this study, we employed immunoprecipitation and mass spectrometry to screen for cellular interacting partners of ORF3. Gene ontology analysis of the host interactome highlighted the involvement of ORF3 in endosomal and immune signaling pathways. Among the identified ORF3-interacting proteins, the vacuolar protein-sorting-associated protein 36 (VPS36) was assessed for its role in PEDV replication. VPS36 was found to interact with ORF3 regardless of its GLUE domain. As a result of VPS36-ORF3 interaction, PEDV replication was substantially suppressed in cells overexpressing VPS36. Interestingly, the ORF3 protein expression was diminished in VPS36-overexpressing cells, an effect that could not be restored by treatment of lysosomal inhibitors. In addition, disruption of endogenously-expressed VPS36 by siRNA could partially augment PEDV replication. Taken together, our study provides mechanistic insights into the contribution of ORF3 in PEDV replication.
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145
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Miyauchi Y, Kimura S, Kimura A, Kurohara K, Hirota Y, Fujimoto K, Mackenzie PI, Tanaka Y, Ishii Y. Investigation of the Endoplasmic Reticulum Localization of UDP-Glucuronosyltransferase 2B7 with Systematic Deletion Mutants. Mol Pharmacol 2019; 95:551-562. [PMID: 30944207 DOI: 10.1124/mol.118.113902] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Accepted: 03/05/2019] [Indexed: 11/22/2022] Open
Abstract
UDP-Glucuronosyltransferase (UGT) plays an important role in the metabolism of endogenous and exogenous compounds. UGT is a type I membrane protein, and has a dilysine motif (KKXX/KXKXX) in its C-terminal cytoplasmic domain. Although a dilysine motif is defined as an endoplasmic reticulum (ER) retrieval signal, it remains a matter of debate whether this motif functions in the ER localization of UGT. To address this issue, we generated systematic deletion mutants of UGT2B7, a major human isoform, and compared their subcellular localizations with that of an ER marker protein calnexin (CNX), using subcellular fractionation and immunofluorescent microscopy. We found that although the dilysine motif functioned as the ER retention signal in a chimera that replaced the cytoplasmic domain of CD4 with that of UGT2B7, UGT2B7 truncated mutants lacking this motif extensively colocalized with CNX, indicating dilysine motif-independent ER retention of UGT2B7. Moreover, deletion of the C-terminal transmembrane and cytoplasmic domains did not affect ER localization of UGT2B7, suggesting that the signal necessary for ER retention of UGT2B7 is present in its luminal domain. Serial deletions of the luminal domain, however, did not affect the ER retention of the mutants. Further, a cytoplasmic and transmembrane domain-deleted mutant of UGT2B7 was localized to the ER without being secreted. These results suggest that UGT2B7 could localize to the ER without any retention signal, and lead to the conclusion that the static localization of UGT results from lack of a signal for export from the ER.
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Affiliation(s)
- Yuu Miyauchi
- Division of Pharmaceutical Cell Biology, Graduate School of Pharmaceutical Sciences (Y.M., A.K., K.K., Y.H., K.F., Y.T.) and Laboratory of Molecular Life Sciences, Graduate School of Pharmaceutical Sciences (Y.M., S.K., Y.I.), Kyushu University, Fukuoka, Japan; and Department of Clinical Pharmacology, Flinders Medical Centre and Flinders University, Adelaide, South Australia, Australia (P.I.M.)
| | - Sora Kimura
- Division of Pharmaceutical Cell Biology, Graduate School of Pharmaceutical Sciences (Y.M., A.K., K.K., Y.H., K.F., Y.T.) and Laboratory of Molecular Life Sciences, Graduate School of Pharmaceutical Sciences (Y.M., S.K., Y.I.), Kyushu University, Fukuoka, Japan; and Department of Clinical Pharmacology, Flinders Medical Centre and Flinders University, Adelaide, South Australia, Australia (P.I.M.)
| | - Akane Kimura
- Division of Pharmaceutical Cell Biology, Graduate School of Pharmaceutical Sciences (Y.M., A.K., K.K., Y.H., K.F., Y.T.) and Laboratory of Molecular Life Sciences, Graduate School of Pharmaceutical Sciences (Y.M., S.K., Y.I.), Kyushu University, Fukuoka, Japan; and Department of Clinical Pharmacology, Flinders Medical Centre and Flinders University, Adelaide, South Australia, Australia (P.I.M.)
| | - Ken Kurohara
- Division of Pharmaceutical Cell Biology, Graduate School of Pharmaceutical Sciences (Y.M., A.K., K.K., Y.H., K.F., Y.T.) and Laboratory of Molecular Life Sciences, Graduate School of Pharmaceutical Sciences (Y.M., S.K., Y.I.), Kyushu University, Fukuoka, Japan; and Department of Clinical Pharmacology, Flinders Medical Centre and Flinders University, Adelaide, South Australia, Australia (P.I.M.)
| | - Yuko Hirota
- Division of Pharmaceutical Cell Biology, Graduate School of Pharmaceutical Sciences (Y.M., A.K., K.K., Y.H., K.F., Y.T.) and Laboratory of Molecular Life Sciences, Graduate School of Pharmaceutical Sciences (Y.M., S.K., Y.I.), Kyushu University, Fukuoka, Japan; and Department of Clinical Pharmacology, Flinders Medical Centre and Flinders University, Adelaide, South Australia, Australia (P.I.M.)
| | - Keiko Fujimoto
- Division of Pharmaceutical Cell Biology, Graduate School of Pharmaceutical Sciences (Y.M., A.K., K.K., Y.H., K.F., Y.T.) and Laboratory of Molecular Life Sciences, Graduate School of Pharmaceutical Sciences (Y.M., S.K., Y.I.), Kyushu University, Fukuoka, Japan; and Department of Clinical Pharmacology, Flinders Medical Centre and Flinders University, Adelaide, South Australia, Australia (P.I.M.)
| | - Peter I Mackenzie
- Division of Pharmaceutical Cell Biology, Graduate School of Pharmaceutical Sciences (Y.M., A.K., K.K., Y.H., K.F., Y.T.) and Laboratory of Molecular Life Sciences, Graduate School of Pharmaceutical Sciences (Y.M., S.K., Y.I.), Kyushu University, Fukuoka, Japan; and Department of Clinical Pharmacology, Flinders Medical Centre and Flinders University, Adelaide, South Australia, Australia (P.I.M.)
| | - Yoshitaka Tanaka
- Division of Pharmaceutical Cell Biology, Graduate School of Pharmaceutical Sciences (Y.M., A.K., K.K., Y.H., K.F., Y.T.) and Laboratory of Molecular Life Sciences, Graduate School of Pharmaceutical Sciences (Y.M., S.K., Y.I.), Kyushu University, Fukuoka, Japan; and Department of Clinical Pharmacology, Flinders Medical Centre and Flinders University, Adelaide, South Australia, Australia (P.I.M.)
| | - Yuji Ishii
- Division of Pharmaceutical Cell Biology, Graduate School of Pharmaceutical Sciences (Y.M., A.K., K.K., Y.H., K.F., Y.T.) and Laboratory of Molecular Life Sciences, Graduate School of Pharmaceutical Sciences (Y.M., S.K., Y.I.), Kyushu University, Fukuoka, Japan; and Department of Clinical Pharmacology, Flinders Medical Centre and Flinders University, Adelaide, South Australia, Australia (P.I.M.)
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146
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Solarewicz J, Manly A, Kokoszka S, Sleiman N, Leff T, Cala S. Adiponectin secretion from cardiomyocytes produces canonical multimers and partial co-localization with calsequestrin in junctional SR. Mol Cell Biochem 2019; 457:201-214. [PMID: 30919218 DOI: 10.1007/s11010-019-03524-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Accepted: 03/15/2019] [Indexed: 01/21/2023]
Abstract
Adiponectin (ADN) is an abundant protein in serum, secreted by adipocytes, that acts as a signal for fat metabolism. It is marked by a complex molecular structure that results from processes within the secretory pathway, producing a canonical set of multimers. ADN may also be secreted from cardiomyocytes, where a unique sarcomeric endoplasmic/sarcoplasmic reticulum (ER/SR) substructure has been characterized primarily for its Ca handling. We expressed ADN in cultured primary adult cardiomyocytes and nonmuscle (COS) cells. After 48 h of ADN expression by adenovirus treatment, roughly half of synthesized ADN was secreted from cardiomyocytes, and half was still in-transit within inner membrane compartments, similar to COS cells. Cardiomyocytes and COS cells both produced ADN in the three canonical forms: trimers, hexamers, and 18-mers. Higher rates of secretion occurred for higher-molecular weight multimers, especially 18-mers. The highest levels of ADN protein, whether in transit or secreted, were present as trimers and hexamers. In nonmuscle cell lines, ADN trafficked through ER and Golgi compartments as expected. In contrast, ADN in primary adult cardiomyocytes populated ER/SR tubules along the edges of sarcomeres that emanated from nuclear surfaces. Prominent co-localization of ADN occurred with calsequestrin, a marker of junctional SR, the Ca2+-release compartment of the cell. The early steps in ADN trafficking re-trace those recently described for newly made junctional SR proteins, involving a nuclear envelope (NE) translocation into SR tubules that are oriented along sarcolemmal transverse (T)-tubules (NEST pathway).
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Affiliation(s)
- Joanna Solarewicz
- Department of Physiology, Wayne State University, Detroit, MI, 48201, USA
| | - Amanda Manly
- Department of Physiology, Wayne State University, Detroit, MI, 48201, USA
| | - Stephanie Kokoszka
- Department of Physiology, Wayne State University, Detroit, MI, 48201, USA
| | - Naama Sleiman
- Department of Physiology, Wayne State University, Detroit, MI, 48201, USA
| | - Todd Leff
- Department of Pathology, Wayne State University, Detroit, MI, 48201, USA
| | - Steven Cala
- Department of Physiology, Wayne State University, Detroit, MI, 48201, USA.
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147
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Papadopoulou AA, Müller SA, Mentrup T, Shmueli MD, Niemeyer J, Haug-Kröper M, von Blume J, Mayerhofer A, Feederle R, Schröder B, Lichtenthaler SF, Fluhrer R. Signal peptide peptidase-like 2c impairs vesicular transport and cleaves SNARE proteins. EMBO Rep 2019; 20:e46451. [PMID: 30733281 PMCID: PMC6399617 DOI: 10.15252/embr.201846451] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2018] [Revised: 12/07/2018] [Accepted: 12/21/2018] [Indexed: 12/25/2022] Open
Abstract
Members of the GxGD-type intramembrane aspartyl proteases have emerged as key players not only in fundamental cellular processes such as B-cell development or protein glycosylation, but also in development of pathologies, such as Alzheimer's disease or hepatitis virus infections. However, one member of this protease family, signal peptide peptidase-like 2c (SPPL2c), remains orphan and its capability of proteolysis as well as its physiological function is still enigmatic. Here, we demonstrate that SPPL2c is catalytically active and identify a variety of SPPL2c candidate substrates using proteomics. The majority of the SPPL2c candidate substrates cluster to the biological process of vesicular trafficking. Analysis of selected SNARE proteins reveals proteolytic processing by SPPL2c that impairs vesicular transport and causes retention of cargo proteins in the endoplasmic reticulum. As a consequence, the integrity of subcellular compartments, in particular the Golgi, is disturbed. Together with a strikingly high physiological SPPL2c expression in testis, our data suggest involvement of SPPL2c in acrosome formation during spermatogenesis.
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Affiliation(s)
- Alkmini A Papadopoulou
- Institute for Metabolic Biochemistry, Biomedical Center (BMC), Ludwig-Maximilians University Munich, Munich, Germany
| | - Stephan A Müller
- DZNE - German Center for Neurodegenerative Diseases, Munich, Germany
| | - Torben Mentrup
- Biochemical Institute, Christian Albrechts University of Kiel, Kiel, Germany
| | - Merav D Shmueli
- DZNE - German Center for Neurodegenerative Diseases, Munich, Germany
- Department of Immunology, The Weizmann Institute of Science, Rehovot, Israel
- Neuroproteomics, School of Medicine, Klinikum Rechts der Isar, and Institute for Advanced Study, Technical University Munich, Munich, Germany
| | - Johannes Niemeyer
- Biochemical Institute, Christian Albrechts University of Kiel, Kiel, Germany
| | - Martina Haug-Kröper
- Institute for Metabolic Biochemistry, Biomedical Center (BMC), Ludwig-Maximilians University Munich, Munich, Germany
| | | | - Artur Mayerhofer
- Cell Biology, Anatomy III, Biomedical Center (BMC), Ludwig-Maximilians University Munich, Munich, Germany
| | - Regina Feederle
- DZNE - German Center for Neurodegenerative Diseases, Munich, Germany
- Institute for Diabetes and Obesity, Monoclonal Antibody Core Facility, Helmholtz Center Munich, German Research Center for Environmental Health, Neuherberg, Germany
- Munich Center for Systems Neurology (SyNergy), Munich, Germany
| | - Bernd Schröder
- Biochemical Institute, Christian Albrechts University of Kiel, Kiel, Germany
- Institute for Physiological Chemistry, Technische Universität Dresden, Dresden, Germany
| | - Stefan F Lichtenthaler
- DZNE - German Center for Neurodegenerative Diseases, Munich, Germany
- Neuroproteomics, School of Medicine, Klinikum Rechts der Isar, and Institute for Advanced Study, Technical University Munich, Munich, Germany
- Munich Center for Systems Neurology (SyNergy), Munich, Germany
| | - Regina Fluhrer
- Institute for Metabolic Biochemistry, Biomedical Center (BMC), Ludwig-Maximilians University Munich, Munich, Germany
- DZNE - German Center for Neurodegenerative Diseases, Munich, Germany
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148
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Khan F, Suguna K. Crystal structure of the legume lectin-like domain of an ERGIC-53-like protein from Entamoeba histolytica. Acta Crystallogr F Struct Biol Commun 2019; 75:197-204. [PMID: 30839295 PMCID: PMC6404861 DOI: 10.1107/s2053230x19000499] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2018] [Accepted: 01/09/2019] [Indexed: 01/09/2023] Open
Abstract
ERGIC-53-like proteins are type I membrane proteins that belong to the class of intracellular cargo receptors and are known to be indispensable for the intracellular transport of glycoproteins. They are implicated in transporting glycoproteins between the endoplasmic reticulum and the Golgi body. The crystal structure of the legume lectin-like domain of an ERGIC-53-like protein from Entamoeba histolytica has been determined at 2.4 Å resolution. Although the overall structure of the domain resembles those of its mammalian and yeast orthologs (ERGIC-53 and Emp46, respectively), there are significant changes in the carbohydrate-binding site. A sequence-based search revealed the presence of several homologs of ERGIC-53 in different species of Entamoeba. This is the first report of the structural characterization of a member of this class of proteins from a protozoan and serves to further knowledge and understanding regarding the species-specific differences.
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Affiliation(s)
- Farha Khan
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, Karnataka 560 012, India
| | - Kaza Suguna
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, Karnataka 560 012, India
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149
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Fu YL, Zhang B, Mu TW. LMAN1 (ERGIC-53) promotes trafficking of neuroreceptors. Biochem Biophys Res Commun 2019; 511:356-362. [PMID: 30791981 DOI: 10.1016/j.bbrc.2019.02.053] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Accepted: 02/10/2019] [Indexed: 12/15/2022]
Abstract
The endoplasmic reticulum-Golgi intermediate compartment protein-53 (ERGIC-53, aka LMAN1), which cycles between the endoplasmic reticulum (ER) and Golgi, is a known cargo receptor for a number of soluble proteins. However, whether LMAN1 plays a role as a trafficking factor in the central nervous system is largely unknown. Here, we determined the role of LMAN1 on endogenous protein levels of the Cys-loop superfamily of neuroreceptors, including gamma-aminobutyric acid type A receptors (GABAARs), 5-hydroxytryptamine (serotonin) type 3 (5-HT3) receptors, and nicotinic acetylcholine receptors (nAChRs). Knockdown of LMAN1 reduces the surface trafficking of endogenous β3 subunits of GABAARs in mouse hypothalamic GT1-7 neurons. Furthermore, Western blot analysis of brain homogenates from LMAN1 knockout mice demonstrated that loss of LMAN1 decreases the total protein levels of 5HT3A receptors and γ2 subunits of GABAARs. LMAN1 knockout regulates the ER proteostasis network by upregulating ERP44 without changing calnexin levels. Interestingly, despite the critical role of the glycan-binding function of LMAN1 in its other known cargo clients, LMAN1 interacts with GABAARs in a glycan-independent manner. In summary, LMAN1 is a trafficking factor for certain neuroreceptors in the central nervous system. This is the first report of LMAN1 function in membrane protein trafficking.
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Affiliation(s)
- Yan-Lin Fu
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Bin Zhang
- Genomic Medicine Institute, Lerner Research Institute of Cleveland Clinic, Cleveland, OH, USA
| | - Ting-Wei Mu
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH, USA.
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Naturally Occurring Hepatitis B Virus Mutations Leading to Endoplasmic Reticulum Stress and Their Contribution to the Progression of Hepatocellular Carcinoma. Int J Mol Sci 2019; 20:ijms20030597. [PMID: 30704071 PMCID: PMC6387469 DOI: 10.3390/ijms20030597] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2018] [Revised: 01/23/2019] [Accepted: 01/24/2019] [Indexed: 02/07/2023] Open
Abstract
Hepatitis B virus (HBV) infection is a global health problem that causes a wide range of pathological outcomes, including cirrhosis and hepatocellular carcinoma (HCC). Endoplasmic reticulum (ER) stress induction by HBV infection has been implicated in liver carcinogenesis and disease progression with chronic inflammation via enhanced inflammation, oxidative stress-mediated DNA damage, and hepatocyte proliferation. In the natural course of HBV infection, the accumulation of naturally occurring mutations in the HBV genome can generate several mutant types of HBV-encoded proteins, including three different proteins in the S ORF (SHBs, MHBs, and LHBs) and HBcAg in the C ORF, which could contribute to enhanced ER stress in infected hepatocytes mainly via increased ER accumulation of mutant proteins. However, it seems that there may be distinct capacity and pathway in ER stress-induction and distinct resulting clinical outcomes between HBV variants. In addition, the role of HBxAg mutations in ER stress remains unknown. However, it has been reported that HBxAg itself could exert ER stress in infected cells, resulting in HCC generation in chronic HBV patients. To date, review papers regarding ER stress-mediated HBV mutation have been limited into a specific mutation type: preS2 deletion. So, in this review, we will discuss details about various mutation types in all four regions of the HBV genome (preS1, preS2, S, and C) related to ER stress and their distinct ER stress mechanisms and clinical outcomes in terms of mutation types.
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