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Oliveira PVS, Dalla Torre M, Debbas V, Orsi A, Laurindo FRM, Sitia R. Transport of protein disulfide isomerase from the endoplasmic reticulum to the extracellular space without passage through the Golgi complex. J Biol Chem 2024; 300:107536. [PMID: 38971317 DOI: 10.1016/j.jbc.2024.107536] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2024] [Revised: 05/29/2024] [Accepted: 06/21/2024] [Indexed: 07/08/2024] Open
Abstract
Protein disulfide isomerase-A1 (PDIA1) is a master regulator of oxidative protein folding and proteostasis in the endoplasmic reticulum (ER). However, PDIA1 can reach the extracellular space, impacting thrombosis and other pathophysiological phenomena. Whether PDIA1 is externalized via passive release or active secretion is not known. To investigate how PDIA1 negotiates its export, we generated a tagged variant that undergoes N-glycosylation in the ER (Glyco-PDIA1). Addition of N-glycans does not alter its enzymatic functions. Upon either deletion of its KDEL ER-localization motif or silencing of KDEL receptors, Glyco-PDIA1 acquires complex glycans in the Golgi and is secreted. In control cells, however, Glyco-PDIA1 is released with endoglycosidase-H sensitive glycans, implying that it does not follow the classical ER-Golgi route nor does it encounter glycanases in the cytosol. Extracellular Glyco-PDIA1 is more abundant than actin, lactate dehydrogenase, or other proteins released by damaged or dead cells, suggesting active transport through a Golgi-independent route. The strategy we describe herein can be extended to dissect how select ER-residents reach the extracellular space.
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Affiliation(s)
- Percillia Victoria Santos Oliveira
- Division of Genetics and Cell Biology Vita-Salute San Raffaele University and IRCCS San Raffaele Scientific Institute, Milan, Italy; Laboratorio de Biologia Vascular, LIM-64 (Biologia Cardiovascular Translacional), Instituto do Coração (InCor), Hospital das Clinicas HCFMUSP, Faculdade de Medicina, Universidade de São Paulo, São Paulo, SP, Brasil
| | - Marco Dalla Torre
- Division of Genetics and Cell Biology Vita-Salute San Raffaele University and IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Victor Debbas
- Laboratorio de Biologia Vascular, LIM-64 (Biologia Cardiovascular Translacional), Instituto do Coração (InCor), Hospital das Clinicas HCFMUSP, Faculdade de Medicina, Universidade de São Paulo, São Paulo, SP, Brasil
| | - Andrea Orsi
- Division of Genetics and Cell Biology Vita-Salute San Raffaele University and IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Francisco Rafael Martins Laurindo
- Laboratorio de Biologia Vascular, LIM-64 (Biologia Cardiovascular Translacional), Instituto do Coração (InCor), Hospital das Clinicas HCFMUSP, Faculdade de Medicina, Universidade de São Paulo, São Paulo, SP, Brasil.
| | - Roberto Sitia
- Division of Genetics and Cell Biology Vita-Salute San Raffaele University and IRCCS San Raffaele Scientific Institute, Milan, Italy.
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2
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Esapa CT, McIlhinney RAJ, Waite AJ, Benson MA, Mirzayan J, Piko H, Herczegfalvi Á, Horvath R, Karcagi V, Walter MC, Lochmüller H, Rizkallah PJ, Lu QL, Blake DJ. Misfolding of fukutin-related protein (FKRP) variants in congenital and limb girdle muscular dystrophies. Front Mol Biosci 2023; 10:1279700. [PMID: 38161385 PMCID: PMC10755465 DOI: 10.3389/fmolb.2023.1279700] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Accepted: 11/16/2023] [Indexed: 01/03/2024] Open
Abstract
Fukutin-related protein (FKRP, MIM ID 606596) variants cause a range of muscular dystrophies associated with hypo-glycosylation of the matrix receptor, α-dystroglycan. These disorders are almost exclusively caused by homozygous or compound heterozygous missense variants in the FKRP gene that encodes a ribitol phosphotransferase. To understand how seemingly diverse FKRP missense mutations may contribute to disease, we examined the synthesis, intracellular dynamics, and structural consequences of a panel of missense mutations that encompass the disease spectrum. Under non-reducing electrophoresis conditions, wild type FKRP appears to be monomeric whereas disease-causing FKRP mutants migrate as high molecular weight, disulfide-bonded aggregates. These results were recapitulated using cysteine-scanning mutagenesis suggesting that abnormal disulfide bonding may perturb FKRP folding. Using fluorescence recovery after photobleaching, we found that the intracellular mobility of most FKRP mutants in ATP-depleted cells is dramatically reduced but can, in most cases, be rescued with reducing agents. Mass spectrometry showed that wild type and mutant FKRP differentially associate with several endoplasmic reticulum (ER)-resident chaperones. Finally, structural modelling revealed that disease-associated FKRP missense variants affected the local environment of the protein in small but significant ways. These data demonstrate that protein misfolding contributes to the molecular pathophysiology of FKRP-deficient muscular dystrophies and suggest that molecules that rescue this folding defect could be used to treat these disorders.
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Affiliation(s)
| | | | - Adrian J. Waite
- Centre for Neuropsychiatric Genetics and Genomics, Division of Psychological Medicine and Clinical Neurosciences, School of Medicine, Cardiff University, Cardiff, United Kingdom
| | | | - Jasmin Mirzayan
- Centre for Neuropsychiatric Genetics and Genomics, Division of Psychological Medicine and Clinical Neurosciences, School of Medicine, Cardiff University, Cardiff, United Kingdom
| | - Henriett Piko
- Department of Internal Medicine and Oncology, Semmelweis University, Budapest, Hungary
| | - Ágnes Herczegfalvi
- Semmelweis University Pediatric Center Tűzoltó Street Unit, Budapest, Hungary
| | - Rita Horvath
- Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom
| | - Veronika Karcagi
- National Institute of Environmental Health, Department of Molecular Genetics and Diagnostics, Istenhegyi Genetic Diagnostic Centre, Budapest, Hungary
| | - Maggie C. Walter
- Friedrich-Baur-Institute at the Department of Neurology, University Hospital, Munich, Germany
| | - Hanns Lochmüller
- Children’s Hospital of Eastern Ontario Research Institute, Division of Neurology, Department of Medicine, The Ottawa Hospital, and Brain and Mind Research Institute, University of Ottawa, Ottawa, ON, Canada
| | - Pierre J. Rizkallah
- Division of Infection and Immunity, School of Medicine, Cardiff University, Cardiff, United Kingdom
| | - Qi L. Lu
- McColl-Lockwood Laboratory for Muscular Dystrophy Research, Carolinas Medical Center, Charlotte, United States
| | - Derek J. Blake
- Centre for Neuropsychiatric Genetics and Genomics, Division of Psychological Medicine and Clinical Neurosciences, School of Medicine, Cardiff University, Cardiff, United Kingdom
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3
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Aschenbrenner I, Siebenmorgen T, Lopez A, Parr M, Ruckgaber P, Kerle A, Rührnößl F, Catici D, Haslbeck M, Frishman D, Sattler M, Zacharias M, Feige MJ. Assembly-dependent Structure Formation Shapes Human Interleukin-23 versus Interleukin-12 Secretion. J Mol Biol 2023; 435:168300. [PMID: 37805067 DOI: 10.1016/j.jmb.2023.168300] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Revised: 09/29/2023] [Accepted: 10/01/2023] [Indexed: 10/09/2023]
Abstract
Interleukin 12 (IL-12) family cytokines connect the innate and adaptive branches of the immune system and regulate immune responses. A unique characteristic of this family is that each member is anα:βheterodimer. For human αsubunits it has been shown that they depend on theirβsubunit for structure formation and secretion from cells. Since subunits are shared within the family and IL-12 as well as IL-23 use the same βsubunit, subunit competition may influence cytokine secretion and thus downstream immunological functions. Here, we rationally design a folding-competent human IL-23α subunit that does not depend on itsβsubunit for structure formation. This engineered variant still forms a functional heterodimeric cytokine but shows less chaperone dependency and stronger affinity in assembly with its βsubunit. It forms IL-23 more efficiently than its natural counterpart, skewing the balance of IL-12 and IL-23 towards more IL-23 formation. Together, our study shows that folding-competent human IL-12 familyαsubunits are obtainable by only few mutations and compatible with assembly and function of the cytokine. These findings might suggest that human α subunits have evolved for assembly-dependent folding to maintain and regulate correct IL-12 family member ratios in the light of subunit competition.
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Affiliation(s)
- Isabel Aschenbrenner
- Technical University of Munich, TUM School of Natural Sciences, Department of Bioscience, Center for Functional Protein Assemblies (CPA), Garching, Germany
| | - Till Siebenmorgen
- Technical University of Munich, TUM School of Natural Sciences, Department of Bioscience, Center for Functional Protein Assemblies (CPA), Garching, Germany; Helmholtz Munich, Molecular Targets & Therapeutics Center, Institute of Structural Biology, Neuherberg, Germany
| | - Abraham Lopez
- Technical University of Munich, TUM School of Natural Sciences, Department of Bioscience, Bavarian NMR Center, Garching, Germany; Helmholtz Munich, Molecular Targets & Therapeutics Center, Institute of Structural Biology, Neuherberg, Germany
| | - Marina Parr
- Technical University of Munich, TUM School of Life Sciences, Department of Bioinformatics, Freising, Germany
| | - Philipp Ruckgaber
- Technical University of Munich, TUM School of Natural Sciences, Department of Bioscience, Center for Functional Protein Assemblies (CPA), Garching, Germany
| | - Anna Kerle
- Technical University of Munich, TUM School of Natural Sciences, Department of Bioscience, Center for Functional Protein Assemblies (CPA), Garching, Germany
| | - Florian Rührnößl
- Technical University of Munich, TUM School of Natural Sciences, Department of Bioscience, Center for Functional Protein Assemblies (CPA), Garching, Germany
| | - Dragana Catici
- Technical University of Munich, TUM School of Natural Sciences, Department of Bioscience, Center for Functional Protein Assemblies (CPA), Garching, Germany
| | - Martin Haslbeck
- Technical University of Munich, TUM School of Natural Sciences, Department of Bioscience, Center for Functional Protein Assemblies (CPA), Garching, Germany
| | - Dmitrij Frishman
- Technical University of Munich, TUM School of Life Sciences, Department of Bioinformatics, Freising, Germany
| | - Michael Sattler
- Technical University of Munich, TUM School of Natural Sciences, Department of Bioscience, Bavarian NMR Center, Garching, Germany; Helmholtz Munich, Molecular Targets & Therapeutics Center, Institute of Structural Biology, Neuherberg, Germany
| | - Martin Zacharias
- Technical University of Munich, TUM School of Natural Sciences, Department of Bioscience, Center for Functional Protein Assemblies (CPA), Garching, Germany
| | - Matthias J Feige
- Technical University of Munich, TUM School of Natural Sciences, Department of Bioscience, Center for Functional Protein Assemblies (CPA), Garching, Germany.
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4
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Amagai Y, Yamada M, Kowada T, Watanabe T, Du Y, Liu R, Naramoto S, Watanabe S, Kyozuka J, Anelli T, Tempio T, Sitia R, Mizukami S, Inaba K. Zinc homeostasis governed by Golgi-resident ZnT family members regulates ERp44-mediated proteostasis at the ER-Golgi interface. Nat Commun 2023; 14:2683. [PMID: 37160917 PMCID: PMC10170084 DOI: 10.1038/s41467-023-38397-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Accepted: 05/01/2023] [Indexed: 05/11/2023] Open
Abstract
Many secretory enzymes acquire essential zinc ions (Zn2+) in the Golgi complex. ERp44, a chaperone operating in the early secretory pathway, also binds Zn2+ to regulate its client binding and release for the control of protein traffic and homeostasis. Notably, three membrane transporter complexes, ZnT4, ZnT5/ZnT6 and ZnT7, import Zn2+ into the Golgi lumen in exchange with protons. To identify their specific roles, we here perform quantitative Zn2+ imaging using super-resolution microscopy and Zn2+-probes targeted in specific Golgi subregions. Systematic ZnT-knockdowns reveal that ZnT4, ZnT5/ZnT6 and ZnT7 regulate labile Zn2+ concentration at the distal, medial, and proximal Golgi, respectively, consistent with their localization. Time-course imaging of cells undergoing synchronized secretory protein traffic and functional assays demonstrates that ZnT-mediated Zn2+ fluxes tune the localization, trafficking, and client-retrieval activity of ERp44. Altogether, this study provides deep mechanistic insights into how ZnTs control Zn2+ homeostasis and ERp44-mediated proteostasis along the early secretory pathway.
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Affiliation(s)
- Yuta Amagai
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Miyagi, 980-8577, Japan
| | - Momo Yamada
- Department of Chemistry, Graduate School of Science, Tohoku University, Sendai, Miyagi, 980-8578, Japan
| | - Toshiyuki Kowada
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Miyagi, 980-8577, Japan
- Department of Chemistry, Graduate School of Science, Tohoku University, Sendai, Miyagi, 980-8578, Japan
- Department of Molecular and Chemical Life Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi, 980-8577, Japan
| | - Tomomi Watanabe
- Department of Molecular and Chemical Life Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi, 980-8577, Japan
| | - Yuyin Du
- Department of Chemistry, Faculty of Science, Tohoku University, 6-3 Aramaki-aza-Aoba, Aoba-ku, Sendai, Miyagi, 980-8578, Japan
| | - Rong Liu
- Department of Molecular and Chemical Life Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi, 980-8577, Japan
| | - Satoshi Naramoto
- Department of Ecological Developmental Adaptability Life Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi, 980-8577, Japan
- Department of Biological Sciences, Faculty of Science, Hokkaido University, Kita 10 Nishi 8, Kita-ku, Sapporo, Japan
| | - Satoshi Watanabe
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Miyagi, 980-8577, Japan
- Department of Chemistry, Graduate School of Science, Tohoku University, Sendai, Miyagi, 980-8578, Japan
- Department of Molecular and Chemical Life Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi, 980-8577, Japan
| | - Junko Kyozuka
- Department of Ecological Developmental Adaptability Life Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi, 980-8577, Japan
| | - Tiziana Anelli
- Division of Genetics and Cell Biology, Vita-Salute University, IRCCS Ospedale San Raffaele, 20132, Milan, Italy
| | - Tiziana Tempio
- Division of Genetics and Cell Biology, Vita-Salute University, IRCCS Ospedale San Raffaele, 20132, Milan, Italy
| | - Roberto Sitia
- Division of Genetics and Cell Biology, Vita-Salute University, IRCCS Ospedale San Raffaele, 20132, Milan, Italy
| | - Shin Mizukami
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Miyagi, 980-8577, Japan
- Department of Chemistry, Graduate School of Science, Tohoku University, Sendai, Miyagi, 980-8578, Japan
- Department of Molecular and Chemical Life Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi, 980-8577, Japan
- Core Research for Evolutional Science and Technology (CREST), Japan Agency for Medical Research and Development (AMED), Chiyoda, Tokyo, Japan
| | - Kenji Inaba
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Miyagi, 980-8577, Japan.
- Department of Chemistry, Graduate School of Science, Tohoku University, Sendai, Miyagi, 980-8578, Japan.
- Department of Molecular and Chemical Life Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi, 980-8577, Japan.
- Core Research for Evolutional Science and Technology (CREST), Japan Agency for Medical Research and Development (AMED), Chiyoda, Tokyo, Japan.
- Medical Institute of Bioregulation, Kyushu University, Fukuoka, 812-8582, Japan.
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5
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Vargas-Zapata V, Geiger KM, Tran D, Ma J, Mao X, Puschnik AS, Coscoy L. SARS-CoV-2 Envelope-mediated Golgi pH dysregulation interferes with ERAAP retention in cells. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2022:2022.11.29.518257. [PMID: 36482965 PMCID: PMC9727756 DOI: 10.1101/2022.11.29.518257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
Endoplasmic reticulum (ER) aminopeptidase associated with antigen processing (ERAAP) trims peptide precursors in the ER for presentation by major histocompatibility (MHC)-I molecules to surveying CD8+ T-cells. This function allows ERAAP to regulate the nature and quality of the peptide repertoire and, accordingly, the resulting immune responses. We recently showed that infection with murine cytomegalovirus leads to a dramatic loss of ERAAP levels in infected cells. In mice, this loss is associated with the activation of QFL T-cells, a subset of T-cells that monitor ERAAP integrity and eliminate cells experiencing ERAAP dysfunction. In this study, we aimed to identify host factors that regulate ERAAP expression level and determine whether these could be manipulated during viral infections. We performed a CRISPR knockout screen and identified ERp44 as a factor promoting ERAAP retention in the ER. ERp44's interaction with ERAAP is dependent on the pH gradient between the ER and Golgi. We hypothesized that viruses that disrupt the pH of the secretory pathway interfere with ERAAP retention. Here, we demonstrate that expression of the Envelope (E) protein from Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) leads to Golgi pH neutralization and consequently decrease of ERAAP intracellular levels. Furthermore, SARS-CoV-2-induced ERAAP loss correlates with its release into the extracellular environment. ERAAP's reliance on ERp44 and a functioning ER/Golgi pH gradient for proper localization and function led us to propose that ERAAP serves as a sensor of disturbances in the secretory pathway during infection and disease.
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Affiliation(s)
- Valerie Vargas-Zapata
- Division of Immunology and Molecular Medicine, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, 94720, USA
| | - Kristina M Geiger
- Division of Immunology and Molecular Medicine, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, 94720, USA
- Division of Infectious Diseases and Vaccinology, School of Public Health, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Dan Tran
- Division of Immunology and Molecular Medicine, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, 94720, USA
| | - Jessica Ma
- Division of Microbial Biology, Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Xiaowen Mao
- Division of Immunology and Molecular Medicine, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, 94720, USA
| | | | - Laurent Coscoy
- Division of Immunology and Molecular Medicine, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, 94720, USA
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6
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Ugalde JM, Aller I, Kudrjasova L, Schmidt RR, Schlößer M, Homagk M, Fuchs P, Lichtenauer S, Schwarzländer M, Müller-Schüssele SJ, Meyer AJ. Endoplasmic reticulum oxidoreductin provides resilience against reductive stress and hypoxic conditions by mediating luminal redox dynamics. THE PLANT CELL 2022; 34:4007-4027. [PMID: 35818121 PMCID: PMC9516139 DOI: 10.1093/plcell/koac202] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Accepted: 07/05/2022] [Indexed: 05/28/2023]
Abstract
Oxidative protein folding in the endoplasmic reticulum (ER) depends on the coordinated action of protein disulfide isomerases and ER oxidoreductins (EROs). Strict dependence of ERO activity on molecular oxygen as the final electron acceptor implies that oxidative protein folding and other ER processes are severely compromised under hypoxia. Here, we isolated viable Arabidopsis thaliana ero1 ero2 double mutants that are highly sensitive to reductive stress and hypoxia. To elucidate the specific redox dynamics in the ER in vivo, we expressed the glutathione redox potential (EGSH) sensor Grx1-roGFP2iL-HDEL with a midpoint potential of -240 mV in the ER of Arabidopsis plants. We found EGSH values of -241 mV in wild-type plants, which is less oxidizing than previously estimated. In the ero1 ero2 mutants, luminal EGSH was reduced further to -253 mV. Recovery to reductive ER stress induced by dithiothreitol was delayed in ero1 ero2. The characteristic signature of EGSH dynamics in the ER lumen triggered by hypoxia was affected in ero1 ero2 reflecting a disrupted balance of reductive and oxidizing inputs, including nascent polypeptides and glutathione entry. The ER redox dynamics can now be dissected in vivo, revealing a central role of EROs as major redox integrators to promote luminal redox homeostasis.
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Affiliation(s)
| | - Isabel Aller
- INRES-Chemical Signalling, University of Bonn, D-53113 Bonn, Germany
| | - Lika Kudrjasova
- INRES-Chemical Signalling, University of Bonn, D-53113 Bonn, Germany
| | - Romy R Schmidt
- Plant Biotechnology, Bielefeld University, D-33615 Bielefeld, Germany
| | - Michelle Schlößer
- INRES-Chemical Signalling, University of Bonn, D-53113 Bonn, Germany
| | - Maria Homagk
- INRES-Chemical Signalling, University of Bonn, D-53113 Bonn, Germany
| | | | - Sophie Lichtenauer
- Institute for Biology and Biotechnology of Plants, University of Münster, D-48143 Münster, Germany
| | - Markus Schwarzländer
- Institute for Biology and Biotechnology of Plants, University of Münster, D-48143 Münster, Germany
| | - Stefanie J Müller-Schüssele
- INRES-Chemical Signalling, University of Bonn, D-53113 Bonn, Germany
- Molecular Botany, Department of Biology, TU Kaiserslautern, D-67663, Kaiserslautern, Germany
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7
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Palazzo FC, Sitia R, Tempio T. Selective Secretion of KDEL-Bearing Proteins: Mechanisms and Functions. Front Cell Dev Biol 2022; 10:967875. [PMID: 35912099 PMCID: PMC9326092 DOI: 10.3389/fcell.2022.967875] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Accepted: 06/24/2022] [Indexed: 11/13/2022] Open
Abstract
In multicellular organisms, cells must continuously exchange messages with the right meaning, intensity, and duration. Most of these messages are delivered through cognate interactions between membrane and secretory proteins. Their conformational maturation is assisted by a vast array of chaperones and enzymes, ensuring the fidelity of intercellular communication. These folding assistants reside in the early secretory compartment (ESC), a functional unit that encompasses endoplasmic reticulum (ER), intermediate compartment and cis-Golgi. Most soluble ESC residents have C-terminal KDEL-like motifs that prevent their transport beyond the Golgi. However, some accumulate in the ER, while others in downstream stations, implying different recycling rates. Moreover, it is now clear that cells can actively secrete certain ESC residents but not others. This essay discusses the physiology of their differential intracellular distribution, and the mechanisms that may ensure selectivity of release.
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8
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Zhang ZY, Lv Y, Wu W, Yan C, Tang CY, Peng C, Li JT. The structural and functional divergence of a neglected three-finger toxin subfamily in lethal elapids. Cell Rep 2022; 40:111079. [PMID: 35830808 DOI: 10.1016/j.celrep.2022.111079] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2022] [Revised: 05/04/2022] [Accepted: 06/20/2022] [Indexed: 11/24/2022] Open
Abstract
Bungarus multicinctus is a widely distributed and medically important elapid snake that produces lethal neurotoxic venom. To study and enhance existing antivenom, we explore the complete repertoire of its toxin genes based on de novo chromosome-level assembly and multi-tissue transcriptome data. Comparative genomic analyses suggest that the three-finger toxin family (3FTX) may evolve through the neofunctionalization of flanking LY6E. A long-neglected 3FTX subfamily (i.e., MKA-3FTX) is also investigated. Only one MKA-3FTX gene, which evolves a different protein conformation, is under positive selection and actively transcribed in the venom gland, functioning as a major toxin effector together with MKT-3FTX subfamily homologs. Furthermore, this lethal snake may acquire self-resistance to its β-bungarotoxin via amino acid replacements on fast-evolving KCNA2. This study provides valuable resources for further evolutionary and structure-function studies of snake toxins, which are fundamental for the development of effective antivenoms and drug candidates.
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Affiliation(s)
- Zhi-Yi Zhang
- CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, Sichuan 610041, China
| | - Yunyun Lv
- CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, Sichuan 610041, China; College of Life Science, Neijiang Normal University, Neijiang, Sichuan 641100, China
| | - Wei Wu
- CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, Sichuan 610041, China; University of Chinese Academy of Sciences, Beijing 101408, China
| | - Chaochao Yan
- CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, Sichuan 610041, China
| | - Chen-Yang Tang
- CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, Sichuan 610041, China
| | - Changjun Peng
- CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, Sichuan 610041, China; University of Chinese Academy of Sciences, Beijing 101408, China
| | - Jia-Tang Li
- CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, Sichuan 610041, China; University of Chinese Academy of Sciences, Beijing 101408, China; Center for Excellence in Animal Evolution and Genetics, Chinese Academy of Sciences, Kunming, Yunnan 650223, China.
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9
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Matsuo Y. Introducing Thioredoxin-Related Transmembrane Proteins: Emerging Roles of Human TMX and Clinical Implications. Antioxid Redox Signal 2022; 36:984-1000. [PMID: 34465218 PMCID: PMC9127828 DOI: 10.1089/ars.2021.0187] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Significance: The presence of a large number of thioredoxin superfamily members suggests a complex mechanism of redox-based regulation in mammalian cells. However, whether these members are functionally redundant or play separate and distinct roles in each cellular compartment remains to be elucidated. Recent Advances: In the mammalian endoplasmic reticulum (ER), ∼20 thioredoxin-like proteins have been identified. Most ER oxidoreductases are soluble proteins located in the luminal compartment, whereas a small family of five thioredoxin-related transmembrane proteins (TMX) also reside in the ER membrane and play crucial roles with specialized functions. Critical Issues: In addition to the predicted function of ER protein quality control, several independent studies have suggested the diverse roles of TMX family proteins in the regulation of cellular processes, including calcium homeostasis, bioenergetics, and thiol-disulfide exchange in the extracellular space. Moreover, recent studies have provided evidence of their involvement in the pathogenesis of various diseases. Future Directions: Extensive research is required to unravel the physiological roles of TMX family proteins. Given that membrane-associated proteins are prime targets for drug discovery in a variety of human diseases, expanding our knowledge on the mechanistic details of TMX action on the cell membrane will provide the molecular basis for developing novel diagnostic and therapeutic approaches as a potent molecular target in a clinical setting. Antioxid. Redox Signal. 36, 984-1000.
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Affiliation(s)
- Yoshiyuki Matsuo
- Department of Human Stress Response Science, Institute of Biomedical Science, Kansai Medical University, Hirakata, Osaka, Japan
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10
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Giannone C, Chelazzi MR, Orsi A, Anelli T, Nguyen T, Buchner J, Sitia R. Biogenesis of secretory immunoglobulin M requires intermediate non-native disulfide bonds and engagement of the protein disulfide isomerase ERp44. EMBO J 2022; 41:e108518. [PMID: 34957576 PMCID: PMC8804937 DOI: 10.15252/embj.2021108518] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Revised: 11/13/2021] [Accepted: 11/25/2021] [Indexed: 02/03/2023] Open
Abstract
Antibodies of the immunoglobulin M (IgM) class represent the frontline of humoral immune responses. They are secreted as planar polymers in which flanking µ2 L2 "monomeric" subunits are linked by two disulfide bonds, one formed by the penultimate cysteine (C575) in the tailpiece of secretory µ chains (µs tp) and the second by C414 in the Cµ3. The latter bond is not present in membrane IgM. Here, we show that C575 forms a non-native, intra-subunit disulfide bond as a key step in the biogenesis of secretory IgM. The abundance of this unexpected intermediate correlates with the onset and extent of polymerization. The rearrangement of the C-terminal tails into a native quaternary structure is guaranteed by the engagement of protein disulfide isomerase ERp44, which attacks the non-native C575 bonds. The resulting conformational changes promote polymerization and formation of C414 disulfide linkages. This unusual assembly pathway allows secretory polymers to form without the risk of disturbing the role of membrane IgM as part of the B cell antigen receptor.
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Affiliation(s)
- Chiara Giannone
- Division of Genetics and Cell BiologyUniversità Vita‐Salute IRCCS Ospedale San RaffaeleMilanoItaly,Vita‐Salute San Raffaele UniversityMilanItaly
| | - Maria Rita Chelazzi
- Division of Genetics and Cell BiologyUniversità Vita‐Salute IRCCS Ospedale San RaffaeleMilanoItaly,Vita‐Salute San Raffaele UniversityMilanItaly
| | - Andrea Orsi
- Division of Genetics and Cell BiologyUniversità Vita‐Salute IRCCS Ospedale San RaffaeleMilanoItaly,Vita‐Salute San Raffaele UniversityMilanItaly
| | - Tiziana Anelli
- Division of Genetics and Cell BiologyUniversità Vita‐Salute IRCCS Ospedale San RaffaeleMilanoItaly,Vita‐Salute San Raffaele UniversityMilanItaly
| | - Tuan Nguyen
- Department ChemistryTechnical University MunichGarchingGermany
| | | | - Roberto Sitia
- Division of Genetics and Cell BiologyUniversità Vita‐Salute IRCCS Ospedale San RaffaeleMilanoItaly,Vita‐Salute San Raffaele UniversityMilanItaly
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11
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Anelli T, Dalla Torre M, Borini E, Mangini E, Ulisse A, Semino C, Sitia R, Panina-Bordignon P. Profound architectural and functional readjustments of the secretory pathway in decidualization of endometrial stromal cells. Traffic 2021; 23:4-20. [PMID: 34651407 DOI: 10.1111/tra.12822] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 07/10/2021] [Accepted: 10/07/2021] [Indexed: 12/19/2022]
Abstract
Certain cell types must expand their exocytic pathway to guarantee efficiency and fidelity of protein secretion. A spectacular case is offered by decidualizing human endometrial stromal cells (EnSCs). In the midluteal phase of the menstrual cycle, progesterone stimulation induces proliferating EnSCs to differentiate into professional secretors releasing proteins essential for efficient blastocyst implantation. Here, we describe the architectural rearrangements of the secretory pathway of a human EnSC line (TERT-immortalized human endometrial stromal cells (T-HESC)). As in primary cells, decidualization entails proliferation arrest and the coordinated expansion of the entire secretory pathway without detectable activation of unfolded protein response (UPR) pathways. Decidualization proceeds also in the absence of ascorbic acid, an essential cofactor for collagen biogenesis, despite also the secretion of some proteins whose folding does not depend on vitamin C is impaired. However, even in these conditions, no overt UPR induction can be detected. Morphometric analyses reveal that the exocytic pathway does not increase relatively to the volume of the cell. Thus, differently from other cell types, abundant production is guaranteed by a coordinated increase of the cell size following arrest of proliferation.
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Affiliation(s)
- Tiziana Anelli
- Faculty of Medicine, San Raffaele Vita-Salute University, Milan, Italy.,Division of Genetics and Cell Biology, IRCCS Ospedale San Raffaele, Milan, Italy
| | - Marco Dalla Torre
- Faculty of Medicine, San Raffaele Vita-Salute University, Milan, Italy
| | - Elena Borini
- Faculty of Medicine, San Raffaele Vita-Salute University, Milan, Italy
| | - Elisabetta Mangini
- Division of Genetics and Cell Biology, IRCCS Ospedale San Raffaele, Milan, Italy
| | - Adele Ulisse
- Division of Genetics and Cell Biology, IRCCS Ospedale San Raffaele, Milan, Italy
| | - Claudia Semino
- Division of Genetics and Cell Biology, IRCCS Ospedale San Raffaele, Milan, Italy
| | - Roberto Sitia
- Faculty of Medicine, San Raffaele Vita-Salute University, Milan, Italy.,Division of Genetics and Cell Biology, IRCCS Ospedale San Raffaele, Milan, Italy
| | - Paola Panina-Bordignon
- Faculty of Medicine, San Raffaele Vita-Salute University, Milan, Italy.,Division of Neuroscience, IRCCS Ospedale San Raffaele, Milan, Italy
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12
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Bi Y, Chang Y, Liu Q, Mao Y, Zhai K, Zhou Y, Jiao R, Ji G. ERp44/CG9911 promotes fat storage in Drosophila adipocytes by regulating ER Ca 2+ homeostasis. Aging (Albany NY) 2021; 13:15013-15031. [PMID: 34031268 PMCID: PMC8221293 DOI: 10.18632/aging.203063] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Accepted: 03/27/2021] [Indexed: 12/12/2022]
Abstract
Fat storage is one of the important strategies employed in regulating energy homeostasis. Impaired lipid storage causes metabolic disorders in both mammals and Drosophila. In this study, we report CG9911, the Drosophila homolog of ERp44 (endoplasmic reticulum protein 44) plays a role in regulating adipose tissue fat storage. Using the CRISPR/Cas9 system, we generated a CG9911 mutant line deleting 5 bp of the coding sequence. The mutant flies exhibit phenotypes of lower bodyweight, fewer lipid droplets, reduced TAG level and increased expression of lipolysis related genes. The increased lipolysis phenotype is enhanced in the presence of ER stresses and suppressed by a reduction of the ER Ca2+. Moreover, loss of CG9911 per se results in a decrease of ER Ca2+ in the fat body. Together, our results reveal a novel function of CG9911 in promoting fat storage via regulating ER Ca2+ signal in Drosophila.
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Affiliation(s)
- Youkun Bi
- Key Laboratory of Interdisciplinary Research, Chinese Academy of Sciences, Beijing 100101, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yan Chang
- Key Laboratory of Interdisciplinary Research, Chinese Academy of Sciences, Beijing 100101, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Qun Liu
- Key Laboratory of Interdisciplinary Research, Chinese Academy of Sciences, Beijing 100101, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yang Mao
- Key Laboratory of Interdisciplinary Research, Chinese Academy of Sciences, Beijing 100101, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Kui Zhai
- Key Laboratory of Interdisciplinary Research, Chinese Academy of Sciences, Beijing 100101, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yuanli Zhou
- Key Laboratory of Protein and Peptide Pharmaceutical, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Renjie Jiao
- Key Laboratory of Interdisciplinary Research, Chinese Academy of Sciences, Beijing 100101, China.,Sino-French Hoffmann Institute, School of Basic Medical Science, Guangzhou Medical University, Guangzhou 510182, China
| | - Guangju Ji
- Key Laboratory of Interdisciplinary Research, Chinese Academy of Sciences, Beijing 100101, China
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13
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Hampe L, Harris PWR, Rushton B, Radjainia M, Brimble MA, Mitra AK. Engineering a stable complex of
ERp44
with a designed peptide ligand for analyzing the mode of interaction of
ERp44
with its clients. Pept Sci (Hoboken) 2021. [DOI: 10.1002/pep2.24230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Lutz Hampe
- School of Biological Sciences The University of Auckland Auckland New Zealand
| | - Paul W. R. Harris
- School of Biological Sciences The University of Auckland Auckland New Zealand
- School of Chemical Sciences The University of Auckland Auckland New Zealand
| | - Ben Rushton
- School of Biological Sciences The University of Auckland Auckland New Zealand
- Bernhard‐Nocht Institute for Tropical Medicine Bernhard‐Nocht‐Straße 74, 20359 Hamburg Germany
| | - Mazdak Radjainia
- School of Biological Sciences The University of Auckland Auckland New Zealand
- Thermo Fisher Scientific Eindhoven The Netherlands
| | - Margaret A. Brimble
- School of Biological Sciences The University of Auckland Auckland New Zealand
- School of Chemical Sciences The University of Auckland Auckland New Zealand
| | - Alok K. Mitra
- School of Biological Sciences The University of Auckland Auckland New Zealand
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14
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Abstract
Significance: Unique to the branched-chain aminotransferase (BCAT) proteins is their redox-active CXXC motif. Subjected to post-translational modification by reactive oxygen species and reactive nitrogen species, these proteins have the potential to adopt numerous cellular roles, which may be fundamental to their role in oncogenesis and neurodegenerative diseases. An understanding of the interplay of the redox regulation of BCAT with important cell signaling mechanisms will identify new targets for future therapeutics. Recent Advances: The BCAT proteins have been assigned novel thiol oxidoreductase activity that can accelerate the refolding of proteins, in particular when S-glutathionylated, supporting a chaperone role for BCAT in protein folding. Other metabolic proteins were also shown to have peroxide-mediated redox associations with BCAT, indicating that the cellular function of BCAT is more diverse. Critical Issues: While the role of branched-chain amino acid metabolism and its metabolites has dominated aspects of cancer research, less is known about the role of BCAT. The importance of the CXXC motif in regulating the BCAT activity under hypoxic conditions, a characteristic of tumors, has not been addressed. Understanding how these proteins operate under various cellular redox conditions will become important, in particular with respect to their moonlighting roles. Future Directions: Advances in the quantification of thiols, their measurement, and the manipulation of metabolons that rely on redox-based interactions should accelerate the investigation of the cellular role of moonlighting proteins such as BCAT. Given the importance of cross talk between signaling pathways, research should focus more on these "housekeeping" proteins paying attention to their wider application. Antioxid. Redox Signal. 34, 1048-1067.
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Affiliation(s)
- Myra Elizabeth Conway
- Department of Applied Science, University of the West of England, Bristol, United Kingdom
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15
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da Silva Rosa SC, Liu M, Sweeney G. Adiponectin Synthesis, Secretion and Extravasation from Circulation to Interstitial Space. Physiology (Bethesda) 2021; 36:134-149. [PMID: 33904786 PMCID: PMC8461789 DOI: 10.1152/physiol.00031.2020] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Adiponectin, an adipokine that circulates as multiple multimeric complexes at high levels in serum, has antidiabetic, anti-inflammatory, antiatherogenic, and cardioprotective properties. Understanding the mechanisms regulating adiponectin's physiological effects is likely to provide critical insight into the development of adiponectin-based therapeutics to treat various metabolic-related diseases. In this review, we summarize our current understanding on adiponectin action in its various target tissues and in cellular models. We also focus on recent advances in two particular regulatory aspects; namely, the regulation of adiponectin gene expression, multimerization, and secretion, as well as extravasation of circulating adiponectin to the interstitial space and its degradation. Finally, we discuss some potential therapeutic approaches using adiponectin as a target and the current challenges facing adiponectin-based therapeutic interventions.
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Affiliation(s)
| | - Meilian Liu
- Department of Biochemistry and Molecular Biology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico
| | - Gary Sweeney
- Department of Biology, York University, Toronto, Ontario, Canada
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16
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A virtuous cycle operated by ERp44 and ERGIC-53 guarantees proteostasis in the early secretory compartment. iScience 2021; 24:102244. [PMID: 33763635 PMCID: PMC7973864 DOI: 10.1016/j.isci.2021.102244] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Revised: 02/01/2021] [Accepted: 02/25/2021] [Indexed: 01/13/2023] Open
Abstract
The composition of the secretome depends on the combined action of cargo receptors that facilitate protein transport and sequential checkpoints that restrict it to native conformers. Acting after endoplasmic reticulum (ER)-resident chaperones, ERp44 retrieves its clients from downstream compartments. To guarantee efficient quality control, ERp44 should exit the ER as rapidly as its clients, or more. Here, we show that appending ERp44 to different cargo proteins increases their secretion rates. ERp44 binds the cargo receptor ER-Golgi intermediate compartment (ERGIC)-53 in the ER to negotiate preferential loading into COPII vesicles. Silencing ERGIC-53, or competing for its COPII binding with 4-phenylbutyrate, causes secretion of Prdx4, an enzyme that relies on ERp44 for intracellular localization. In more acidic, zinc-rich downstream compartments, ERGIC-53 releases its clients and ERp44, which can bind and retrieve non-native conformers via KDEL receptors. By coupling the transport of cargoes and inspector proteins, cells ensure efficiency and fidelity of secretion.
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17
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Cobb DW, Kudyba HM, Villegas A, Hoopmann MR, Baptista RP, Bruton B, Krakowiak M, Moritz RL, Muralidharan V. A redox-active crosslinker reveals an essential and inhibitable oxidative folding network in the endoplasmic reticulum of malaria parasites. PLoS Pathog 2021; 17:e1009293. [PMID: 33534803 PMCID: PMC7886143 DOI: 10.1371/journal.ppat.1009293] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 02/16/2021] [Accepted: 01/07/2021] [Indexed: 12/18/2022] Open
Abstract
Malaria remains a major global health problem, creating a constant need for research to identify druggable weaknesses in P. falciparum biology. As important components of cellular redox biology, members of the Thioredoxin (Trx) superfamily of proteins have received interest as potential drug targets in Apicomplexans. However, the function and essentiality of endoplasmic reticulum (ER)-localized Trx-domain proteins within P. falciparum has not been investigated. We generated conditional mutants of the protein PfJ2—an ER chaperone and member of the Trx superfamily—and show that it is essential for asexual parasite survival. Using a crosslinker specific for redox-active cysteines, we identified PfJ2 substrates as PfPDI8 and PfPDI11, both members of the Trx superfamily as well, which suggests a redox-regulatory role for PfJ2. Knockdown of these PDIs in PfJ2 conditional mutants show that PfPDI11 may not be essential. However, PfPDI8 is required for asexual growth and our data suggest it may work in a complex with PfJ2 and other ER chaperones. Finally, we show that the redox interactions between these Trx-domain proteins in the parasite ER and their substrates are sensitive to small molecule inhibition. Together these data build a model for how Trx-domain proteins in the P. falciparum ER work together to assist protein folding and demonstrate the suitability of ER-localized Trx-domain proteins for antimalarial drug development. One of the leading and persistent causes of childhood mortality in the world is malaria, which is caused by parasites from the genus Plasmodium. Unfortunately, the parasite has developed resistance to all available drugs, making the discovery of new drug targets and potential small molecule inhibitors of essential parasite biology a top priority. A critical pathway required for many different biological processes in the parasite is oxidative folding which requires members of the Thioredoxin (Trx) superfamily of proteins. But we know almost nothing about the function and essentiality of Trx-domain proteins that localize to the endoplasmic reticulum, the origin of the secretory pathway, within P. falciparum. Here we show that a network of Trx-domain containing proteins function together and are essential for parasite survival within human red blood cells. Further, we identify a small molecule inhibitor of the redox activities of these Trx-domain containing proteins. This study demonstrates the suitability of this pathway for future antimalarial drug development.
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Affiliation(s)
- David W. Cobb
- Department of Cellular Biology, University of Georgia, Georgia, United States of America
- Center for Tropical and Emerging Global Diseases, University of Georgia, Georgia, United States of America
| | - Heather M. Kudyba
- Department of Cellular Biology, University of Georgia, Georgia, United States of America
- Center for Tropical and Emerging Global Diseases, University of Georgia, Georgia, United States of America
| | - Alejandra Villegas
- Department of Cellular Biology, University of Georgia, Georgia, United States of America
- Center for Tropical and Emerging Global Diseases, University of Georgia, Georgia, United States of America
| | - Michael R. Hoopmann
- Institute for Systems Biology, Seattle, Washington, United States of America
| | - Rodrigo P. Baptista
- Center for Tropical and Emerging Global Diseases, University of Georgia, Georgia, United States of America
- Institute of Bioinformatics, University of Georgia, Georgia, United States of America
| | - Baylee Bruton
- Department of Cellular Biology, University of Georgia, Georgia, United States of America
| | - Michelle Krakowiak
- Department of Cellular Biology, University of Georgia, Georgia, United States of America
- Center for Tropical and Emerging Global Diseases, University of Georgia, Georgia, United States of America
| | - Robert L. Moritz
- Institute for Systems Biology, Seattle, Washington, United States of America
| | - Vasant Muralidharan
- Department of Cellular Biology, University of Georgia, Georgia, United States of America
- Center for Tropical and Emerging Global Diseases, University of Georgia, Georgia, United States of America
- * E-mail:
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18
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Samoudi M, Kuo CC, Robinson CM, Shams-Ud-Doha K, Schinn SM, Kol S, Weiss L, Petersen Bjorn S, Voldborg BG, Rosa Campos A, Lewis NE. In situ detection of protein interactions for recombinant therapeutic enzymes. Biotechnol Bioeng 2021; 118:890-904. [PMID: 33169829 PMCID: PMC7855575 DOI: 10.1002/bit.27621] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 10/20/2020] [Accepted: 10/25/2020] [Indexed: 12/13/2022]
Abstract
Despite their therapeutic potential, many protein drugs remain inaccessible to patients since they are difficult to secrete. Each recombinant protein has unique physicochemical properties and requires different machinery for proper folding, assembly, and posttranslational modifications (PTMs). Here we aimed to identify the machinery supporting recombinant protein secretion by measuring the protein-protein interaction (PPI) networks of four different recombinant proteins (SERPINA1, SERPINC1, SERPING1, and SeAP) with various PTMs and structural motifs using the proximity-dependent biotin identification (BioID) method. We identified PPIs associated with specific features of the secreted proteins using a Bayesian statistical model and found proteins involved in protein folding, disulfide bond formation, and N-glycosylation were positively correlated with the corresponding features of the four model proteins. Among others, oxidative folding enzymes showed the strongest association with disulfide bond formation, supporting their critical roles in proper folding and maintaining the ER stability. Knockdown of disulfide-isomerase PDIA4, a measured interactor with significance for SERPINC1 but not SERPINA1, led to the decreased secretion of SERPINC1, which relies on its extensive disulfide bonds, compared to SERPINA1, which has no disulfide bonds. Proximity-dependent labeling successfully identified the transient interactions supporting synthesis of secreted recombinant proteins and refined our understanding of key molecular mechanisms of the secretory pathway during recombinant protein production.
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Affiliation(s)
- Mojtaba Samoudi
- Dept of Pediatrics, University of California, San Diego
- Novo Nordisk Foundation Center for Biosustainability at UC San Diego
| | - Chih-Chung Kuo
- Novo Nordisk Foundation Center for Biosustainability at UC San Diego
- Dept of Bioengineering, University of California, San Diego
| | - Caressa M. Robinson
- Novo Nordisk Foundation Center for Biosustainability at UC San Diego
- Dept of Bioengineering, University of California, San Diego
| | | | - Song-Min Schinn
- Dept of Pediatrics, University of California, San Diego
- Novo Nordisk Foundation Center for Biosustainability at UC San Diego
| | - Stefan Kol
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark
| | - Linus Weiss
- Dept of Biochemistry, Eberhard Karls University of Tübingen, Germany
| | - Sara Petersen Bjorn
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark
| | - Bjorn G. Voldborg
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark
| | | | - Nathan E. Lewis
- Dept of Pediatrics, University of California, San Diego
- Novo Nordisk Foundation Center for Biosustainability at UC San Diego
- Dept of Bioengineering, University of California, San Diego
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19
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Tempio T, Anelli T. The pivotal role of ERp44 in patrolling protein secretion. J Cell Sci 2020; 133:133/21/jcs240366. [PMID: 33173013 DOI: 10.1242/jcs.240366] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Interactions between protein ligands and receptors are the main language of intercellular communication; hence, how cells select proteins to be secreted or presented on the plasma membrane is a central concern in cell biology. A series of checkpoints are located along the secretory pathway, which ensure the fidelity of such protein signals (quality control). Proteins that pass the checkpoints operated in the endoplasmic reticulum (ER) by the binding immunoglobulin protein (BiP; also known as HSPA5 and GRP78) and the calnexin-calreticulin systems, must still overcome additional scrutiny in the ER-Golgi intermediate compartment (ERGIC) and the Golgi. One of the main players of this process in all metazoans is the ER-resident protein 44 (ERp44); by cycling between the ER and the Golgi, ERp44 controls the localization of key enzymes designed to act in the ER but that are devoid of suitable localization motifs. ERp44 also patrols the secretion of correctly assembled disulfide-linked oligomeric proteins. Here, we discuss the mechanisms driving ERp44 substrate recognition, with important consequences on the definition of 'thiol-mediated quality control'. We also describe how pH and zinc gradients regulate the functional cycle of ERp44, coupling quality control and membrane trafficking along the early secretory compartment.
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Affiliation(s)
- Tiziana Tempio
- Division of Genetics and Cell Biology, Vita-Salute San Raffaele University, Milan 20132, Italy.,IRCCS San Raffaele Scientific Institute, Milan 20132, Italy
| | - Tiziana Anelli
- Division of Genetics and Cell Biology, Vita-Salute San Raffaele University, Milan 20132, Italy .,IRCCS San Raffaele Scientific Institute, Milan 20132, Italy
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20
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Soori M, Mohammadi Y, Goodarzi MT, Mahmoodi M. Association between breast milk adipokines with growth in breast feeding infants, a systematic review and meta-analysis. TURKISH JOURNAL OF BIOCHEMISTRY-TURK BIYOKIMYA DERGISI 2020. [DOI: 10.1515/tjb-2020-0178] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
Objectives
Breast milk adipokines are associated with growth, body mass index (BMI) and weight gain in infants. In this study, the effect of breastmilk adipokines (leptin and adiponectin) on the BMI and weight gain of breast-fed infants was evaluated using systematic review and meta-analysis.
Materials and methods
We used PRISMA checklist for carrying out this study. 752 articles were collected from the database searching and other sources from 1994 to April 2019. According to the criteria in the study, 25 articles remained for evaluation. Eight papers were related to the effect of breast milk leptin on weight gain and BMI of infants that were evaluated by meta-analyzing. The adiponectin articles were surveyed by systematic review.
Results
There was no significant publication bias in the meta-analysis study. The results of random-effect model indicated a reverse and significant correlation between breastmilk leptin with weight gain and BMI (r=−0.331). The adiponectin level in breast milk was associated with the BMI and weight gain of infants.
Conclusions
Meta-analysis indicated a significant inverse correlation between breastmilk leptin with weight gain and BMI in infants; furthermore, the systematic review study expressed significant correlation between breast milk adiponectin with growth (BMI and weight gain) in infants.
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Affiliation(s)
- Maryam Soori
- Department of Biology , Hamedan Branch, Islamic Azad University , Hamedan , Islamic Republic of Iran
| | - Younes Mohammadi
- Department of Epidemiology , Hamadan University of Medical Sciences , Hamadan , Islamic Republic of Iran
| | - Mohammad Taghi Goodarzi
- Department of Biochemistry , Shahrood Branch, Islamic Azad University , Shahrood , Islamic Republic of Iran
| | - Minoo Mahmoodi
- Department of Biology , Hamedan Branch, Islamic Azad University , Hamedan , Islamic Republic of Iran
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21
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Patel C, Saad H, Shenkman M, Lederkremer GZ. Oxidoreductases in Glycoprotein Glycosylation, Folding, and ERAD. Cells 2020; 9:cells9092138. [PMID: 32971745 PMCID: PMC7563561 DOI: 10.3390/cells9092138] [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: 08/31/2020] [Revised: 09/17/2020] [Accepted: 09/18/2020] [Indexed: 12/17/2022] Open
Abstract
N-linked glycosylation and sugar chain processing, as well as disulfide bond formation, are among the most common post-translational protein modifications taking place in the endoplasmic reticulum (ER). They are essential modifications that are required for membrane and secretory proteins to achieve their correct folding and native structure. Several oxidoreductases responsible for disulfide bond formation, isomerization, and reduction have been shown to form stable, functional complexes with enzymes and chaperones that are involved in the initial addition of an N-glycan and in folding and quality control of the glycoproteins. Some of these oxidoreductases are selenoproteins. Recent studies also implicate glycan machinery–oxidoreductase complexes in the recognition and processing of misfolded glycoproteins and their reduction and targeting to ER-associated degradation. This review focuses on the intriguing cooperation between the glycoprotein-specific cell machineries and ER oxidoreductases, and highlights open questions regarding the functions of many members of this large family.
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Affiliation(s)
- Chaitanya Patel
- The Shmunis School of Biomedicine and Cancer Research, Cell Biology Division, George Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel; (C.P.); (H.S.); (M.S.)
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv 69978, Israel
| | - Haddas Saad
- The Shmunis School of Biomedicine and Cancer Research, Cell Biology Division, George Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel; (C.P.); (H.S.); (M.S.)
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv 69978, Israel
| | - Marina Shenkman
- The Shmunis School of Biomedicine and Cancer Research, Cell Biology Division, George Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel; (C.P.); (H.S.); (M.S.)
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv 69978, Israel
| | - Gerardo Z. Lederkremer
- The Shmunis School of Biomedicine and Cancer Research, Cell Biology Division, George Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel; (C.P.); (H.S.); (M.S.)
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv 69978, Israel
- Correspondence:
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22
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Thioredoxin-Related Transmembrane Proteins: TMX1 and Little Brothers TMX2, TMX3, TMX4 and TMX5. Cells 2020; 9:cells9092000. [PMID: 32878123 PMCID: PMC7563315 DOI: 10.3390/cells9092000] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 08/21/2020] [Accepted: 08/24/2020] [Indexed: 02/06/2023] Open
Abstract
The endoplasmic reticulum (ER) is site of synthesis and maturation of membrane and secretory proteins in eukaryotic cells. The ER contains more than 20 members of the Protein Disulfide Isomerase (PDI) family. These enzymes regulate formation, isomerization and disassembly of covalent bonds between cysteine residues. As such, PDIs ensure protein folding, which is required to attain functional and transport-competent structure, and protein unfolding, which facilitates dislocation of defective gene products across the ER membrane for ER-associated degradation (ERAD). The PDI family includes over a dozen of soluble members and few membrane-bound ones. Among these latter, there are five PDIs grouped in the thioredoxin-related transmembrane (TMX) protein family. In this review, we summarize the current knowledge on TMX1, TMX2, TMX3, TMX4 and TMX5, their structural features, regulation and roles in biogenesis and control of the mammalian cell’s proteome.
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Tanaka LY, Oliveira PVS, Laurindo FRM. Peri/Epicellular Thiol Oxidoreductases as Mediators of Extracellular Redox Signaling. Antioxid Redox Signal 2020; 33:280-307. [PMID: 31910038 DOI: 10.1089/ars.2019.8012] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Significance: Supracellular redox networks regulating cell-extracellular matrix (ECM) and organ system architecture merge with structural and functional (catalytic or allosteric) properties of disulfide bonds. This review addresses emerging evidence that exported thiol oxidoreductases (TORs), such as thioredoxin, protein disulfide isomerases (PDIs), quiescin sulfhydryl oxidases (QSOX)1, and peroxiredoxins, composing a peri/epicellular (pec)TOR pool, mediate relevant signaling. pecTOR functions depend mainly on kinetic and spatial regulation of thiol-disulfide exchange reactions governed by redox potentials, which are modulated by exported intracellular low-molecular-weight thiols, together conferring signal specificity. Recent Advances: pecTOR redox-modulates several targets including integrins, ECM proteins, surface molecules, and plasma components, although clear-cut documentation of direct effects is lacking in many cases. TOR catalytic pathways, displaying common patterns, culminate in substrate thiol reduction, oxidation, or isomerization. Peroxiredoxins act as redox/peroxide sensors, contrary to PDIs, which are likely substrate-targeted redox modulators. Emerging evidence suggests important pecTOR roles in patho(physio)logical processes, including blood coagulation, vascular remodeling, mechanosensing, endothelial function, immune responses, and inflammation. Critical Issues: Effects of pecPDIs supporting thrombosis/platelet activation have been well documented and reached the clinical arena. Roles of pecPDIA1 in vascular remodeling/mechanosensing are also emerging. Extracellular thioredoxin and pecPDIs redox-regulate immunoinflammation. Routes of TOR externalization remain elusive and appear to involve Golgi-independent routes. pecTORs are particularly accessible drug targets. Future Directions: Further understanding mechanisms of thiol redox reactions and developing assays for assessing pecTOR redox activities remain important research avenues. Also, addressing pecTORs as disease markers and achieving more efficient/specific drugs for pecTOR modulation are major perspectives for diagnostic/therapeutic improvements.
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Affiliation(s)
- Leonardo Y Tanaka
- Vascular Biology Laboratory, LIM-64 (Translational Cardiovascular Biology), Instituto do Coracao (InCor), Hospital das Clinicas HCFMUSP, Faculdade de Medicina, Universidade de Sao Paulo, Sao Paulo, Brazil
| | - Percillia V S Oliveira
- Vascular Biology Laboratory, LIM-64 (Translational Cardiovascular Biology), Instituto do Coracao (InCor), Hospital das Clinicas HCFMUSP, Faculdade de Medicina, Universidade de Sao Paulo, Sao Paulo, Brazil
| | - Francisco R M Laurindo
- Vascular Biology Laboratory, LIM-64 (Translational Cardiovascular Biology), Instituto do Coracao (InCor), Hospital das Clinicas HCFMUSP, Faculdade de Medicina, Universidade de Sao Paulo, Sao Paulo, Brazil
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Stewart AN, Little HC, Clark DJ, Zhang H, Wong GW. Protein Modifications Critical for Myonectin/Erythroferrone Secretion and Oligomer Assembly. Biochemistry 2020; 59:2684-2697. [PMID: 32602701 DOI: 10.1021/acs.biochem.0c00461] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Myonectin/erythroferrone (also known as CTRP15) is a secreted hormone with metabolic function and a role in stress erythropoiesis. Despite its importance in physiologic processes, biochemical characterization of the protein is lacking. Here, we show that multiple protein modifications are critical for myonectin secretion and multimerization. Abolishing N-linked glycosylation by tunicamycin, glucosamine supplementation, or glutamine substitutions of all four potential Asn glycosylation sites blocked myonectin secretion. Mass spectrometry confirmed that Asn-229 and Asn-281 were glycosylated, and substituting both Asn sites with Gln prevented myonectin secretion. Although Asn-319 is not identified as glycosylated, Gln substitution caused protein misfolding and retention in the endoplasmic reticulum. Of the four conserved cysteines, Cys-273 and Cys-278 were required for proper protein folding; Ala substitution of either site inhibited protein secretion. In contrast, Ala substitutions of Cys-142, Cys-194, or both markedly enhanced protein secretion, suggesting endoplasmic reticulum retention that facilitates myonectin oligomer assembly. Secreted myonectin consists of trimers, hexamers, and high-molecular weight (HMW) oligomers. The formation of higher-order structures via intermolecular disulfide bonds depended on Cys-142 and Cys-194; while the C142A mutant formed almost exclusively trimers, the C194A mutant was impaired in HMW oligomer formation. Most Pro residues within the short collagen domain of myonectin were also hydroxylated, a modification that stabilized the collagen triple helix. Inhibiting Pro hydroxylation or deleting the collagen domain markedly reduced the rate of protein secretion. Together, our results reveal key determinants that are important for myonectin folding, secretion, and multimeric assembly and provide a basis for future structure-function studies.
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Affiliation(s)
- Ashley N Stewart
- Department of Physiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, United States
| | - Hannah C Little
- Department of Physiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, United States
| | - David J Clark
- Department of Pathology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, United States
| | - Hui Zhang
- Department of Pathology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, United States
| | - G William Wong
- Department of Physiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, United States
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Pharmacological induction of selective endoplasmic reticulum retention as a strategy for cancer therapy. Nat Commun 2020; 11:1304. [PMID: 32161259 PMCID: PMC7066181 DOI: 10.1038/s41467-020-15067-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Accepted: 02/17/2020] [Indexed: 12/19/2022] Open
Abstract
The integrated stress response (ISR) converges on eIF2α phosphorylation to regulate protein synthesis. ISR is activated by several stress conditions, including endoplasmic reticulum (ER) stress, executed by protein kinase R-like endoplasmic reticulum kinase (PERK). We report that ER stress combined with ISR inhibition causes an impaired maturation of several tyrosine kinase receptors (RTKs), consistent with a partial block of their trafficking from the ER to the Golgi. Other proteins mature or are secreted normally, indicating selective retention in the ER (sERr). sERr is relieved upon protein synthesis attenuation and is accompanied by the generation of large mixed disulfide bonded complexes, including ERp44. sERr was pharmacologically recapitulated by combining the HIV-protease inhibitor nelfinavir with ISRIB, an experimental drug that inhibits ISR. Nelfinavir/ISRIB combination is highly effective to inhibit the growth of RTK-addicted cell lines and hepatocellular (HCC) cells in vitro and in vivo. Thus, pharmacological sERr can be utilized as a modality for cancer treatment. Inhibition of PERK, an endoplasmic reticulum (ER) unfolded protein response (UPR) protein, is a potential pharmacological target for cancer treatment. Here, the authors show that inhibition of PERK under ER stress affects trafficking from the ER to the surface of several key receptor tyrosine kinases, suggesting a selective ER retention.
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Soumya D, Swetha D, Momin S, Gowtham RR, Dakshinamurthy E, Bharathi T, Sai Gopal DVR. Role of Adiponectin in Cervical Cancer. Curr Drug Metab 2020; 20:1033-1038. [PMID: 31902354 DOI: 10.2174/1389200221666200103113330] [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: 10/24/2019] [Revised: 11/07/2019] [Accepted: 11/07/2019] [Indexed: 11/22/2022]
Abstract
BACKGROUND Cervical Cancer (CC) is the most common leading cancer in women globally. This is considered to be the type of cancer that is restricted to women. Any women in the reproductive age range can develop CC. However, women between the ages of 25 and 39 are at a higher risk. OBJECTIVE In comparison with developed countries, the screening and awareness of CC in developing countries are significantly low. Infection with Human papillomavirus (HPV) is the main cause of CC, especially HPV-16 and HPV-18. Other than HPV, there are other factors that can contribute to CC, such as Human simplex virus (HSV) infection and immunocompromised patients with HIV. CONCLUSION Cervical cancer can be detected by molecular techniques such as (1) PCR, (2) visual acetic acid method, (3) DNA Hybrid II test, (4) liquid-based cytology, (5) Pap-Smear techniques, and (6) colposcopy techniques. Early detection of CC is very much needed; cryotherapy or LEEP (Loop electro surgical excision procedure) can be conducted during the pre-invasive stage of CC. Some metabolic changes in the human body such as fluctuating levels of insulin and triglycerides and increased activity of adiponectin may lead to CC. These contributing factors, such as adipokines, can be used as biomarkers for CC detection.
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Affiliation(s)
| | - Dakshinamurthy Swetha
- Department of Pharmacology, Seven Hills College of Pharmacy, Tirupati, AP-517561, India
| | - Saimila Momin
- Department of Hematology and Medical Oncology, Winship Cancer Institute, Emory University, Atlanta, GA-30322, United States
| | - Racherla Rishi Gowtham
- Department of Microbiology, Sri Venkateswara Institute of Medical Sciences, Tirupati, AP-517507, India
| | | | - Talisetty Bharathi
- Department of Obstetrics and Gynaecology, Govt. Maternity Hospital, Tirupati, AP-517507, India
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Johnson BD, Geldenhuys WJ, Hazlehurst LA. The Role of ERO1α in Modulating Cancer Progression and Immune Escape. JOURNAL OF CANCER IMMUNOLOGY 2020; 2:103-115. [PMID: 33615311 PMCID: PMC7894644 DOI: 10.33696/cancerimmunol.2.023] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Endoplasmic reticulum oxidoreductin-1 alpha (ERO1α) was originally shown to be an endoplasmic reticulum (ER) resident protein undergoing oxidative cycles in concert with protein disulfide isomerase (PDI) to promote proper protein folding and to maintain homeostasis within the ER. ERO1α belongs to the flavoprotein family containing a flavin adenine dinucleotide utilized in transferring of electrons during oxidation-reduction cycles. This family is used to maintain redox potentials and protein homeostasis within the ER. ERO1α's location and function has since been shown to exist beyond the ER. Originally thought to exist solely in the ER, it has since been found to exist in the golgi apparatus, as well as in exosomes purified from patient samples. Besides aiding in protein folding of transmembrane and secretory proteins in conjunction with PDI, ERO1α is also known for formation of de novo disulfide bridges. Public databases, such as the Cancer Genome Atlas (TCGA) and The Protein Atlas, reveal ERO1α as a poor prognostic marker in multiple disease settings. Recent evidence indicates that ERO1α expression in tumor cells is a critical determinant of metastasis. However, the impact of increased ERO1α expression in tumor cells extends into the tumor microenvironment. Secretory proteins requiring ERO1α expression for proper folding have been implicated as being involved in immune escape through promotion of upregulation of programmed death ligand-1 (PD-L1) and stimulation of polymorphonuclear myeloid derived suppressor cells (PMN-MDSC's) via secretion of granulocytic colony stimulating factor (G-CSF). Hereby, ERO1α plays a pivotal role in cancer progression and potentially immune escape; making ERO1α an emerging attractive putative target for the treatment of cancer.
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Affiliation(s)
| | - Werner J. Geldenhuys
- WVU School of Pharmacy, Morgantown, WV, 25606, USA
- WVU Neuroscience Institute, Morgantown, WV, 25606, USA
| | - Lori A. Hazlehurst
- WVU Cancer Institute, Morgantown, WV 26506, USA
- WVU School of Pharmacy, Morgantown, WV, 25606, USA
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Weber B, Maier A, Buchner J. Peptides in proteins. J Pept Sci 2019; 26:e3235. [PMID: 31867828 DOI: 10.1002/psc.3235] [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: 10/25/2019] [Revised: 10/28/2019] [Accepted: 11/04/2019] [Indexed: 12/18/2022]
Abstract
During evolution C-terminal peptide extensions were added to proteins on the gene level. These convey additional functions such as interaction with partner proteins or oligomerisation. IgM antibodies and molecular chaperones are two prominent examples discussed.
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Affiliation(s)
- Benedikt Weber
- Center for Integrated Protein Science Munich at the Department Chemie, Technische Universität München, Garching, Germany
| | - Andreas Maier
- Center for Integrated Protein Science Munich at the Department Chemie, Technische Universität München, Garching, Germany
| | - Johannes Buchner
- Center for Integrated Protein Science Munich at the Department Chemie, Technische Universität München, Garching, Germany
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Keiser KJ, Barlowe C. Molecular dissection of the Erv41-Erv46 retrograde receptor reveals a conserved cysteine-rich region in Erv46 required for retrieval activity. Mol Biol Cell 2019; 31:209-220. [PMID: 31825724 PMCID: PMC7001479 DOI: 10.1091/mbc.e19-08-0484] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The Erv41-Erv46 complex is a conserved retrograde cargo receptor that retrieves ER resident proteins from Golgi compartments in a pH-dependent manner. Here we functionally dissect the Erv46 subunit and define an approximately 60 residue cysteine-rich region that is unique to the Erv46 family of proteins. This cysteine-rich region contains two vicinal cysteine pairs in CXXC and CCXXC configurations that are each required for retrieval activity in cells. Mutation of the individual cysteine residues produced stable Erv46 proteins that were partially reduced and form mixed-disulfide species on nonreducing gels. Conserved hydrophobic amino acids within the cysteine-rich region of Erv46 were also required for retrieval function in cells. In vitro binding experiments showed that this hydrophobic patch is required for direct cargo binding. Surprisingly, the Erv46 cysteine mutants continued to bind cargo in cell-free assays and produced an increased level of Erv46-cargo complexes in cell extracts suggesting that disulfide linkages in the cysteine-rich region perform a role in releasing bound cargo. On the basis of these findings, we propose that both pH and redox environments regulate cargo binding to a hydrophobic site within the cysteine-rich region of Erv46.
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Affiliation(s)
- Kristofer J Keiser
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH 03755
| | - Charles Barlowe
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH 03755
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The molecular basis of chaperone-mediated interleukin 23 assembly control. Nat Commun 2019; 10:4121. [PMID: 31511508 PMCID: PMC6739322 DOI: 10.1038/s41467-019-12006-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Accepted: 08/14/2019] [Indexed: 01/20/2023] Open
Abstract
The functionality of most secreted proteins depends on their assembly into a defined quaternary structure. Despite this, it remains unclear how cells discriminate unassembled proteins en route to the native state from misfolded ones that need to be degraded. Here we show how chaperones can regulate and control assembly of heterodimeric proteins, using interleukin 23 (IL-23) as a model. We find that the IL-23 α-subunit remains partially unstructured until assembly with its β-subunit occurs and identify a major site of incomplete folding. Incomplete folding is recognized by different chaperones along the secretory pathway, realizing reliable assembly control by sequential checkpoints. Structural optimization of the chaperone recognition site allows it to bypass quality control checkpoints and provides a secretion-competent IL-23α subunit, which can still form functional heterodimeric IL-23. Thus, locally-restricted incomplete folding within single-domain proteins can be used to regulate and control their assembly. It is unclear how unassembled secretory pathway proteins are discriminated from misfolded ones. Here the authors combine biophysical and cellular experiments to study the folding of heterodimeric interleukin 23 and describe how ER chaperones recognize unassembled proteins and aid their assembly into protein complexes while preventing the premature degradation of unassembled units.
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Liu L, Wang W, Zhao Z, Hu C, Tao L, Zhang X. Pholidonone, an active stilbene derivative from Pholidota cantonensis, exhibits pro-apoptotic effect via induction of endoplasmic reticulum stress in human gastric cancer. Food Nutr Res 2019; 63:3553. [PMID: 31548837 PMCID: PMC6744839 DOI: 10.29219/fnr.v63.3553] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Revised: 07/10/2019] [Accepted: 07/11/2019] [Indexed: 11/29/2022] Open
Abstract
Background Gastric cancer (GC) is the second leading cause of cancer death worldwide. Current chemotherapeutic drugs exert therapeutic effects accompanied by severe side effects. Therefore, it is imperative to urgently find new drugs with low toxicity and high efficacy for the treatment of GC. Natural products as well as functional foods have always been rich sources of potential antitumor agents. Pholidota cantonensis Rolfe, a well-known functional food and a traditional Chinese medicine, has been used for a long time in China for inflammatory diseases. Previously, we have evaluated its possible antitumor potentials by screening different solvent extracts, and found that the ethyl acetate (EtOAc) extract showed potent cytotoxicity on human GC cell line AGS with an IC50 value of 33.68 ± 1.68 μg/mL. In view of the poor knowledge concerning the phytochemical and pharmacological study of P. cantonensis, it is essential to characterize the active compounds from EtOAc extract and the mechanisms of action underlying the antitumor effect of the herb. Objective This study aimed to identify the primary compounds in EtOAc extract of P. cantonensis involved in the antitumor activity of the plant by evaluating the cytotoxicity in two human GC cell lines, including AGS and BGC-823 cells. Since endoplasmic reticulum (ER) stress-induced cell apoptosis represents attractive targets for cancer therapy recently, we focused on the underlying mechanisms associated with ER stress-induced cell apoptosis and related signaling pathways. Methods Various chromatographic techniques, including silica gel, Sephadex LH-20, and octadecylsilyl silica gel (ODS) C18, were used to separate the main active compound from EtOAc extract of P. cantonensis. The cell viability of AGS and BGC-823 cells upon purified compound treatment was determined by a 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. The alteration of cell morphology was observed using an inverted microscope. Cell apoptosis was determined by fluorescein isothiocyanate (FITC)-labeled annexin-V/propidium iodide (PI) double-staining and flow cytometry analysis. Western blot analyses were performed to examine the levels of intracellular signaling molecules involved in ER stress-induced apoptosis. Results A rare stilbene derivative pholidonone was isolated and identified. The results showed that pholidonone displayed potent cytotoxicity on human GC cells. The IC50 values for 24 and 48 h in AGS cells were 26.54 ± 0.32 and 25.20 ± 3.67 μM, and the IC50 values for 24 and 48 h in BGC-823 cells were 32.41 ± 3.83 and 17.28 ± 2.30 μM, respectively. In addition, pholidonone had pro-apoptotic effect on AGS and BGC-823 cells, and it upregulated the levels of proteins involved in ER stress, including BiP, PDI, Calnexin, Ero1-Lα, IRE1α, PERK, CHOP, and cleaved-caspase-3 in AGS and BGC-823 cells. Conclusion Pholidonone can trigger ER stress-induced apoptosis through PERK and IRE1α signaling pathways. Pholidonone might be a potential naturally occurring antitumor agent.
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Affiliation(s)
- Liang Liu
- Institute of Translational Medicine, Medical College, Yangzhou University, Yangzhou, China.,The Key Laboratory of Syndrome Differentiation and Treatment of Gastric Cancer of the State Administration of Traditional Chinese Medicine, Yangzhou University, Yangzhou, China.,Jiangsu Key Laboratory of Zoonosis, Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, College of Veterinary Medicine, Yangzhou University, Yangzhou, China
| | - Wei Wang
- Institute of Translational Medicine, Medical College, Yangzhou University, Yangzhou, China.,The Key Laboratory of Syndrome Differentiation and Treatment of Gastric Cancer of the State Administration of Traditional Chinese Medicine, Yangzhou University, Yangzhou, China
| | - Zhichen Zhao
- Institute of Translational Medicine, Medical College, Yangzhou University, Yangzhou, China
| | - Chen Hu
- Institute of Translational Medicine, Medical College, Yangzhou University, Yangzhou, China
| | - Li Tao
- Institute of Translational Medicine, Medical College, Yangzhou University, Yangzhou, China.,The Key Laboratory of Syndrome Differentiation and Treatment of Gastric Cancer of the State Administration of Traditional Chinese Medicine, Yangzhou University, Yangzhou, China
| | - Xianwen Zhang
- Oncology Department, Clinical Medical College, Yangzhou University, Subei People's Hospital of Jiangsu Province, Yangzhou, China
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The role of ERp44 in glucose and lipid metabolism. Arch Biochem Biophys 2019; 671:175-184. [PMID: 31283909 DOI: 10.1016/j.abb.2019.06.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Revised: 06/25/2019] [Accepted: 06/27/2019] [Indexed: 12/21/2022]
Abstract
Endoplasmic Reticulum Protein 44 (ERp44) is a member of the PDI family, named for a molecular weight of 44 kD. White adipose tissue has metabolic and endocrine functions that are important to metabolism. The role of ERp44 in glucose and lipid metabolism is not known yet. The current study was undertaken to investigate the implication of ERp44 in glucose and lipid metabolism. In this study, we generated and characterized ERp44-/- mice. We used type 2 diabetes models and ERp44 knockout mice to show the implication of ERp44 in glucose and lipid metabolism. Knockout newborns had lower blood glucose compared to wild-type. Adult knockouts had abnormal intraperitoneal, glucose, insulin and pyruvic acid tolerance. Lipocytes were smaller and fewer in knockout mice compared to wild-type. Knockouts resisted to high-fat diet-induced obesity. ERp44 expression in white adipose tissue decreased significantly in type 2 diabetes models. Results suggest that ERp44 is closely associated with glucose and lipid metabolism.
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Abstract
The site of protein folding and maturation for the majority of proteins that are secreted, localized to the plasma membrane or targeted to endomembrane compartments is the endoplasmic reticulum (ER). It is essential that proteins targeted to the ER are properly folded in order to carry out their function, as well as maintain protein homeostasis, as accumulation of misfolded proteins could lead to the formation of cytotoxic aggregates. Because protein folding is an error-prone process, the ER contains protein quality control networks that act to optimize proper folding and trafficking of client proteins. If a protein is unable to reach its native state, it is targeted for ER retention and subsequent degradation. The protein quality control networks of the ER that oversee this evaluation or interrogation process that decides the fate of maturing nascent chains is comprised of three general types of families: the classical chaperones, the carbohydrate-dependent system, and the thiol-dependent system. The cooperative action of these families promotes protein quality control and protein homeostasis in the ER. This review will describe the families of the ER protein quality control network and discuss the functions of individual members.
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Affiliation(s)
- Benjamin M Adams
- Department of Biochemistry and Molecular Biology, University of Massachusetts, 240 Thatcher Road, Amherst, MA, 01003, USA
- Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, MA, 01003, USA
| | - Michela E Oster
- Department of Biochemistry and Molecular Biology, University of Massachusetts, 240 Thatcher Road, Amherst, MA, 01003, USA
| | - Daniel N Hebert
- Department of Biochemistry and Molecular Biology, University of Massachusetts, 240 Thatcher Road, Amherst, MA, 01003, USA.
- Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, MA, 01003, USA.
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Liyanage D, Omeka W, Lee J. Molecular characterization, host defense mechanisms, and functional analysis of ERp44 from big-belly seahorse: A novel member of the teleost thioredoxin family present in the endoplasmic reticulum. Comp Biochem Physiol B Biochem Mol Biol 2019; 232:31-41. [DOI: 10.1016/j.cbpb.2019.02.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Revised: 01/25/2019] [Accepted: 02/01/2019] [Indexed: 12/22/2022]
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Zinc regulates ERp44-dependent protein quality control in the early secretory pathway. Nat Commun 2019; 10:603. [PMID: 30723194 PMCID: PMC6363758 DOI: 10.1038/s41467-019-08429-1] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Accepted: 01/09/2019] [Indexed: 01/14/2023] Open
Abstract
Zinc ions (Zn2+) are imported into the early secretory pathway by Golgi-resident transporters, but their handling and functions are not fully understood. Here, we show that Zn2+ binds with high affinity to the pH-sensitive chaperone ERp44, modulating its localization and ability to retrieve clients like Ero1α and ERAP1 to the endoplasmic reticulum (ER). Silencing the Zn2+ transporters that uptake Zn2+ into the Golgi led to ERp44 dysfunction and increased secretion of Ero1α and ERAP1. High-resolution crystal structures of Zn2+-bound ERp44 reveal that Zn2+ binds to a conserved histidine-cluster. The consequent large displacements of the regulatory C-terminal tail expose the substrate-binding surface and RDEL motif, ensuring client capture and retrieval. ERp44 also forms Zn2+-bridged homodimers, which dissociate upon client binding. Histidine mutations in the Zn2+-binding sites compromise ERp44 activity and localization. Our findings reveal a role of Zn2+ as a key regulator of protein quality control at the ER-Golgi interface. Zinc ions (Zn2+) are imported by Golgi-resident transporters but the function of zinc in the early secretory pathway has remained unknown. Here the authors find that Zn2+ regulates protein quality control in the early secretory pathway by demonstrating that the pH-sensitive chaperone ERp44 binds Zn2+ and solving the Zn2+-bound ERp44 structure.
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Post-translational modifications of serotonin transporter. Pharmacol Res 2019; 140:7-13. [PMID: 30394319 DOI: 10.1016/j.phrs.2018.10.018] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Revised: 10/18/2018] [Accepted: 10/18/2018] [Indexed: 11/17/2022]
Abstract
The serotonin transporter (SERT) is an oligomeric glycoprotein with two sialic acid residues on each of two complex oligosaccharide molecules. Studies using in vivo and in vitro model systems demonstrated that diverse post-translational modifications, including phosphorylation, glycosylation, serotonylation, and disulfide bond formation, all favorably influences SERT conformation and allows the transporter to function most efficiently. This review discusses the post-translational modifications and their importance on the structure, maturation, and serotonin (5-HT) uptake ability of SERT. Finally, we discuss how these modifications are altered in diabetes mellitus and subsequently impairs the 5-HT uptake ability of SERT.
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A folding switch regulates interleukin 27 biogenesis and secretion of its α-subunit as a cytokine. Proc Natl Acad Sci U S A 2019; 116:1585-1590. [PMID: 30651310 DOI: 10.1073/pnas.1816698116] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
A common design principle of heteromeric signaling proteins is the use of shared subunits. This allows encoding of complex messages while maintaining evolutionary flexibility. How cells regulate and control assembly of such composite signaling proteins remains an important open question. An example of particular complexity and biological relevance is the interleukin 12 (IL-12) family. Four functionally distinct αβ heterodimers are assembled from only five subunits to regulate immune cell function and development. In addition, some subunits act as independent signaling molecules. Here we unveil key molecular mechanisms governing IL-27 biogenesis, an IL-12 family member that limits infections and autoimmunity. In mice, the IL-27α subunit is secreted as a cytokine, whereas in humans only heterodimeric IL-27 is present. Surprisingly, we find that differences in a single amino acid determine if IL-27α can be secreted autonomously, acting as a signaling molecule, or if it depends on heterodimerization for secretion. By combining computer simulations with biochemical experiments, we dissect the underlying structural determinants: a protein folding switch coupled to disulfide bond formation regulates chaperone-mediated retention versus secretion. Using these insights, we rationally change folding and assembly control for this protein. This provides the basis for a more human-like IL-27 system in mice and establishes a secretion-competent human IL-27α that signals on its own and can regulate immune cell function. Taken together, our data reveal a close link between protein folding and immunoregulation. Insights into the underlying mechanisms can be used to engineer immune modulators.
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Zhang J, Zhu Q, Wang X, Yu J, Chen X, Wang J, Wang X, Xiao J, Wang CC, Wang L. Secretory kinase Fam20C tunes endoplasmic reticulum redox state via phosphorylation of Ero1α. EMBO J 2018; 37:embj.201798699. [PMID: 29858230 DOI: 10.15252/embj.201798699] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Revised: 04/20/2018] [Accepted: 04/24/2018] [Indexed: 11/09/2022] Open
Abstract
Family with sequence similarity 20C (Fam20C), the physiological Golgi casein kinase, phosphorylates numerous secreted proteins that are involved in a wide variety of biological processes. However, the role of Fam20C in regulating proteins in the endoplasmic reticulum (ER) lumen is largely unknown. Here, we report that Fam20C interacts with various luminal proteins and that its depletion results in a more reduced ER lumen. We further show that ER oxidoreductin 1α (Ero1α), the pivotal sulfhydryl oxidase that catalyzes disulfide formation in the ER, is phosphorylated by Fam20C in the Golgi apparatus and retrograde-transported to the ER mediated by ERp44. The phosphorylation of Ser145 greatly enhances Ero1α oxidase activity and is critical for maintaining ER redox homeostasis and promoting oxidative protein folding. Notably, phosphorylation of Ero1α is induced under hypoxia, reductive stress, and secretion-demanding conditions such as mammalian lactation. Collectively, our findings open a door to uncover how oxidative protein folding is regulated by phosphorylation in the secretory pathway.
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Affiliation(s)
- Jianchao Zhang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Qinyu Zhu
- The State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing, China.,Academy for Advanced Interdisciplinary Studies, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, China
| | - Xi'e Wang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Jiaojiao Yu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Xinxin Chen
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Jifeng Wang
- Laboratory of Proteomics, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Xi Wang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Junyu Xiao
- The State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing, China.,Academy for Advanced Interdisciplinary Studies, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, China
| | - Chih-Chen Wang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Lei Wang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China .,College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
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Smirnova OA, Bartosch B, Zakirova NF, Kochetkov SN, Ivanov AV. Polyamine Metabolism and Oxidative Protein Folding in the ER as ROS-Producing Systems Neglected in Virology. Int J Mol Sci 2018; 19:ijms19041219. [PMID: 29673197 PMCID: PMC5979612 DOI: 10.3390/ijms19041219] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Revised: 04/03/2018] [Accepted: 04/11/2018] [Indexed: 12/23/2022] Open
Abstract
Reactive oxygen species (ROS) are produced in various cell compartments by an array of enzymes and processes. An excess of ROS production can be hazardous for normal cell functioning, whereas at normal levels, ROS act as vital regulators of many signal transduction pathways and transcription factors. ROS production is affected by a wide range of viruses. However, to date, the impact of viral infections has been studied only in respect to selected ROS-generating enzymes. The role of several ROS-generating and -scavenging enzymes or cellular systems in viral infections has never been addressed. In this review, we focus on the roles of biogenic polyamines and oxidative protein folding in the endoplasmic reticulum (ER) and their interplay with viruses. Polyamines act as ROS scavengers, however, their catabolism is accompanied by H2O2 production. Hydrogen peroxide is also produced during oxidative protein folding, with ER oxidoreductin 1 (Ero1) being a major source of oxidative equivalents. In addition, Ero1 controls Ca2+ efflux from the ER in response to e.g., ER stress. Here, we briefly summarize the current knowledge on the physiological roles of biogenic polyamines and the role of Ero1 at the ER, and present available data on their interplay with viral infections.
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Affiliation(s)
- Olga A Smirnova
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Vavilov str. 32, Moscow 119991, Russia.
| | - Birke Bartosch
- Cancer Research Center Lyon, INSERM U1052 and CNRS 5286, Lyon University, 69003 Lyon, France.
- DevWeCan Laboratories of Excellence Network (Labex), Lyon 69003, France.
| | - Natalia F Zakirova
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Vavilov str. 32, Moscow 119991, Russia.
| | - Sergey N Kochetkov
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Vavilov str. 32, Moscow 119991, Russia.
| | - Alexander V Ivanov
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Vavilov str. 32, Moscow 119991, Russia.
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40
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Nandi S, Ghosh S, Bhattacharyya K. Live Cell Microscopy: A Physical Chemistry Approach. J Phys Chem B 2018; 122:3023-3036. [PMID: 29389140 DOI: 10.1021/acs.jpcb.7b11689] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Probing dynamics of intracellular components using physical chemistry techniques is a remarkable bottom-up approach for understanding the structures and functions of a biological cell. In this "Feature Article", we give an overview on local polarity, solvation, viscosity, acid-base property, red-ox processes (thiol-disulfide exchange), and gene silencing at selected intracellular components inside a live cell. Significant differences have been observed between cancer cells and their noncancer counterparts. We demonstrate that thiol-disulfide exchange, calcium oscillation, and gene silencing are manifested in time dependence of fluorescence intensity. We show that fluorescent gold nanoclusters may be used in drug delivery (e.g., doxorubicin) and selective killing of cancer cells. Further, we discuss dynamics and structural changes of DNA quadruplexes and i-motifs, induced by different external conditions (e.g., pH) and additives (e.g., K+ and other target specific small molecules). We demonstrate that peptidomimetic analogues have high specificity over double-stranded DNA for binding with i-motifs and G-quadruplexes. These results may have significant biological implications.
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Affiliation(s)
- Somen Nandi
- Department of Physical Chemistry , Indian Association for the Cultivation of Science , Jadavpur, Kolkata 700 032 , India
| | - Surajit Ghosh
- Organic & Medicinal Chemistry Division , CSIR-Indian Institute of Chemical Biology , 4, Raja S. C. Mullick Road , Jadavpur, Kolkata , 700 032 West Bengal , India.,Academy of Scientific and Innovative Research (AcSIR) , CSIR-Indian Institute of Chemical Biology Campus , 4 Raja S. C. Mullick Road , Jadavpur, Kolkata 700 032 , India
| | - Kankan Bhattacharyya
- Department of Chemistry , Indian Institute of Science Education and Research Bhopal , Bhopal , 462 066 Madhya Pradesh , India
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41
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Abstract
Professional secretory cells can produce large amounts of high-quality complex molecules, including IgM antibodies. Owing to their multivalency, polymeric IgM antibodies provide an efficient first-line of defense against pathogens. To decipher the mechanisms of IgM assembly, we investigated its biosynthesis in living cells and faithfully reconstituted the underlying processes in vitro. We find that a conserved peptide extension at the C-terminal end of the IgM heavy (Ig-μ) chains, termed the tailpiece, is necessary and sufficient to establish the correct geometry. Alanine scanning revealed that hydrophobic amino acids in the first half of the tailpiece contain essential information for generating the correct topology. Assembly is triggered by the formation of a disulfide bond linking two tailpieces. This induces conformational changes in the tailpiece and the adjacent domain, which drive further polymerization. Thus, the biogenesis of large and topologically challenging IgM complexes is dictated by a local conformational switch in a peptide extension.
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Abstract
Cysteine thiols are among the most reactive functional groups in proteins, and their pairing in disulfide linkages is a common post-translational modification in proteins entering the secretory pathway. This modest amino acid alteration, the mere removal of a pair of hydrogen atoms from juxtaposed cysteine residues, contrasts with the substantial changes that characterize most other post-translational reactions. However, the wide variety of proteins that contain disulfides, the profound impact of cross-linking on the behavior of the protein polymer, the numerous and diverse players in intracellular pathways for disulfide formation, and the distinct biological settings in which disulfide bond formation can take place belie the simplicity of the process. Here we lay the groundwork for appreciating the mechanisms and consequences of disulfide bond formation in vivo by reviewing chemical principles underlying cysteine pairing and oxidation. We then show how enzymes tune redox-active cofactors and recruit oxidants to improve the specificity and efficiency of disulfide formation. Finally, we discuss disulfide bond formation in a cellular context and identify important principles that contribute to productive thiol oxidation in complex, crowded, dynamic environments.
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Affiliation(s)
- Deborah Fass
- Department of Structural Biology, Weizmann Institute of Science , Rehovot 7610001, Israel
| | - Colin Thorpe
- Department of Chemistry and Biochemistry, University of Delaware , Newark, Delaware 19716, United States
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Yuen CYL, Wang P, Kang BH, Matsumoto K, Christopher DA. A Non-Classical Member of the Protein Disulfide Isomerase Family, PDI7 of Arabidopsis thaliana, Localizes to the cis-Golgi and Endoplasmic Reticulum Membranes. PLANT & CELL PHYSIOLOGY 2017; 58:1103-1117. [PMID: 28444333 DOI: 10.1093/pcp/pcx057] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Accepted: 04/13/2017] [Indexed: 06/07/2023]
Abstract
Members of the protein disulfide isomerase (PDI)-C subfamily are chimeric proteins containing the thioredoxin (Trx) domain of PDIs, and the conserved N- and C-terminal Pfam domains of Erv41p/Erv46p-type cargo receptors. They are unique to plants and chromalveolates. The Arabidopsis genome encodes three PDI-C isoforms: PDI7, PDI12 and PDI13. Here we demonstrate that PDI7 is a 65 kDa integral membrane glycoprotein expressed throughout many Arabidopsis tissues. Using a PDI7-specific antibody, we show through immunoelectron microscopy that PDI7 localizes to the endoplasmic reticulum (ER) and Golgi membranes in wild-type root tip cells, and was also detected in vesicles. Tomographic modeling of the Golgi revealed that PDI7 was confined to the cis-Golgi, and accumulated primarily at the cis-most cisterna. Shoot apical meristem cells from transgenic plants overexpressing PDI7 exhibited a dramatic increase in anti-PDI7 labeling at the cis-Golgi. When N- or C-terminal fusions between PDI7 and the green fluorescent protein variant, GFP(S65T), were expressed in mesophyll protoplasts, the fusions co-localized with the ER marker, ER-mCherry. However, when GFP(S65T) was positioned internally within PDI7 (PDI7-GFPint), the fusion strongly co-localized with the cis-Golgi marker, mCherry-SYP31, and faintly labeled the ER. In contrast to the Golgi-resident fusion protein (Man49-mCherry), PDI7-GFPint did not redistribute to the ER after brefeldin A treatment. Protease protection experiments indicated that the Trx domain of PDI7 is located within the ER/Golgi lumen. We propose a model where PDI-C isoforms function as cargo receptors for proteins containing exposed cysteine residues, cycling them from the Golgi back to the ER.
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Affiliation(s)
- Christen Y L Yuen
- University of Hawaii, Molecular Biosciences & Bioengineering, Honolulu, HI, USA
| | - Pengfei Wang
- Chinese University of Hong Kong, Centre for Cell and Developmental Biology, State Key Laboratory of Agrobiotechnology, Shatin, Hong Kong, China
| | - Byung-Ho Kang
- Chinese University of Hong Kong, Centre for Cell and Developmental Biology, State Key Laboratory of Agrobiotechnology, Shatin, Hong Kong, China
| | - Kristie Matsumoto
- University of Hawaii, Molecular Biosciences & Bioengineering, Honolulu, HI, USA
| | - David A Christopher
- University of Hawaii, Molecular Biosciences & Bioengineering, Honolulu, HI, USA
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44
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Gutiérrez T, Simmen T. Endoplasmic reticulum chaperones tweak the mitochondrial calcium rheostat to control metabolism and cell death. Cell Calcium 2017; 70:64-75. [PMID: 28619231 DOI: 10.1016/j.ceca.2017.05.015] [Citation(s) in RCA: 73] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Revised: 05/24/2017] [Accepted: 05/24/2017] [Indexed: 12/16/2022]
Abstract
The folding of secretory proteins is a well-understood mechanism, based on decades of research on endoplasmic reticulum (ER) chaperones. These chaperones interact with newly imported polypeptides close to the ER translocon. Classic examples for these proteins include the immunoglobulin binding protein (BiP/GRP78), and the lectins calnexin and calreticulin. Although not considered chaperones per se, the ER oxidoreductases of the protein disulfide isomerase (PDI) family complete the folding job by catalyzing the formation of disulfide bonds through cysteine oxidation. Research from the past decade has demonstrated that ER chaperones are multifunctional proteins. The regulation of ER-mitochondria Ca2+ crosstalk is one of their additional functions, as shown for calnexin, BiP/GRP78 or the oxidoreductases Ero1α and TMX1. This function depends on interactions of this group of proteins with the ER Ca2+ handling machinery. This novel function makes perfect sense for two reasons: i. It allows ER chaperones to control mitochondrial apoptosis instantly without a lengthy bypass involving the upregulation of pro-apoptotic transcription factors via the unfolded protein response (UPR); and ii. It allows the ER protein folding machinery to fine-tune ATP import via controlling the speed of mitochondrial oxidative phosphorylation. Therefore, the role of ER chaperones in regulating ER-mitochondria Ca2+ flux identifies the progression of secretory protein folding as a central regulator of cell survival and death, at least in cell types that secrete large amount of proteins. In other cell types, ER protein folding might serve as a sentinel mechanism that monitors cellular well-being to control cell metabolism and apoptosis. The selenoprotein SEPN1 is a classic example for such a role. Through the control of ER-mitochondria Ca2+-flux, ER chaperones and folding assistants guide cellular apoptosis and mitochondrial metabolism.
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Affiliation(s)
- Tomas Gutiérrez
- Faculty of Medicine and Dentistry, Department of Cell Biology, University of Alberta, Edmonton, T6G2H7, Canada
| | - Thomas Simmen
- Faculty of Medicine and Dentistry, Department of Cell Biology, University of Alberta, Edmonton, T6G2H7, Canada,.
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45
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Structural basis of pH-dependent client binding by ERp44, a key regulator of protein secretion at the ER-Golgi interface. Proc Natl Acad Sci U S A 2017; 114:E3224-E3232. [PMID: 28373561 DOI: 10.1073/pnas.1621426114] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
ERp44 retrieves some endoplasmic reticulum (ER)-resident enzymes and immature oligomers of secretory proteins from the Golgi. Association of ERp44 with its clients is regulated by pH-dependent mechanisms, but the molecular details are not fully understood. Here we report high-resolution crystal structures of human ERp44 at neutral and weakly acidic pH. These structures reveal key regions in the C-terminal tail (C tail) missing in the original crystal structure, including a regulatory histidine-rich region and a subsequent extended loop. The former region forms a short α-helix (α16), generating a histidine-clustered site (His cluster). At low pH, the three Trx-like domains of ERp44 ("a," "b," and "b'") undergo significant rearrangements, likely induced by protonation of His157 located at the interface between the a and b domains. The α16-helix is partially unwound and the extended loop is disordered in weakly acidic conditions, probably due to electrostatic repulsion between the protonated histidines in the His cluster. Molecular dynamics simulations indicated that helix unwinding enhances the flexibility of the C tail, disrupting its normal hydrogen-bonding pattern. The observed pH-dependent conformational changes significantly enlarge the positively charged regions around the client-binding site of ERp44 at low pH. Mutational analyses showed that ERp44 forms mixed disulfides with specific cysteines residing on negatively charged loop regions of Ero1α. We propose that the protonation states of the essential histidines regulate the ERp44-client interaction by altering the C-tail dynamics and surface electrostatic potential of ERp44.
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46
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Molecular Determinants of the Regulation of Development and Metabolism by Neuronal eIF2α Phosphorylation in Caenorhabditis elegans. Genetics 2017; 206:251-263. [PMID: 28292919 DOI: 10.1534/genetics.117.200568] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Accepted: 03/09/2017] [Indexed: 11/18/2022] Open
Abstract
Cell-nonautonomous effects of signaling in the nervous system of animals can influence diverse aspects of organismal physiology. We previously showed that phosphorylation of Ser49 of the α-subunit of eukaryotic translation initiation factor 2 (eIF2α) in two chemosensory neurons by PEK-1/PERK promotes entry of Caenorhabditis elegans into dauer diapause. Here, we identified and characterized the molecular determinants that confer sensitivity to effects of neuronal eIF2α phosphorylation on development and physiology of C. elegans Isolation and characterization of mutations in eif-2Ba encoding the α-subunit of eIF2B support a conserved role, previously established by studies in yeast, for eIF2Bα in providing a binding site for phosphorylated eIF2α to inhibit the exchange factor eIF2B catalytic activity that is required for translation initiation. We also identified a mutation in eif-2c, encoding the γ-subunit of eIF2, which confers insensitivity to the effects of phosphorylated eIF2α while also altering the requirement for eIF2Bγ. In addition, we show that constitutive expression of eIF2α carrying a phosphomimetic S49D mutation in the ASI pair of sensory neurons confers dramatic effects on growth, metabolism, and reproduction in adult transgenic animals, phenocopying systemic responses to starvation. Furthermore, we show that constitutive expression of eIF2α carrying a phosphomimetic S49D mutation in the ASI neurons enhances dauer entry through bypassing the requirement for nutritionally deficient conditions. Our data suggest that the state of eIF2α phosphorylation in the ASI sensory neuron pair may modulate internal nutrient sensing and signaling pathways, with corresponding organismal effects on development and metabolism.
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Marchi S, Bittremieux M, Missiroli S, Morganti C, Patergnani S, Sbano L, Rimessi A, Kerkhofs M, Parys JB, Bultynck G, Giorgi C, Pinton P. Endoplasmic Reticulum-Mitochondria Communication Through Ca 2+ Signaling: The Importance of Mitochondria-Associated Membranes (MAMs). ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 997:49-67. [PMID: 28815521 DOI: 10.1007/978-981-10-4567-7_4] [Citation(s) in RCA: 93] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The execution of proper Ca2+ signaling requires close apposition between the endoplasmic reticulum (ER) and mitochondria. Hence, Ca2+ released from the ER is "quasi-synaptically" transferred to mitochondrial matrix, where Ca2+ stimulates mitochondrial ATP synthesis by activating the tricarboxylic acid (TCA) cycle. However, when the Ca2+ transfer is excessive and sustained, mitochondrial Ca2+ overload induces apoptosis by opening the mitochondrial permeability transition pore. A large number of regulatory proteins reside at mitochondria-associated ER membranes (MAMs) to maintain the optimal distance between the organelles and to coordinate the functionality of both ER and mitochondrial Ca2+ transporters or channels. In this chapter, we discuss the different pathways involved in the regulation of ER-mitochondria Ca2+ flux and describe the activities of the various Ca2+ players based on their primary intra-organelle localization.
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Affiliation(s)
- Saverio Marchi
- Department of Morphology, Surgery and Experimental Medicine, Section of Pathology, Oncology and Experimental Biology, Laboratory for Technologies of Advanced Therapies (LTTA), University of Ferrara, Ferrara, Italy
| | - Mart Bittremieux
- Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine and Leuven Kanker Instituut, KU Leuven, Campus Gasthuisberg O&N-I box 802, Herestraat 49, B-3000, Leuven, Belgium
| | - Sonia Missiroli
- Department of Morphology, Surgery and Experimental Medicine, Section of Pathology, Oncology and Experimental Biology, Laboratory for Technologies of Advanced Therapies (LTTA), University of Ferrara, Ferrara, Italy
| | - Claudia Morganti
- Department of Morphology, Surgery and Experimental Medicine, Section of Pathology, Oncology and Experimental Biology, Laboratory for Technologies of Advanced Therapies (LTTA), University of Ferrara, Ferrara, Italy
| | - Simone Patergnani
- Department of Morphology, Surgery and Experimental Medicine, Section of Pathology, Oncology and Experimental Biology, Laboratory for Technologies of Advanced Therapies (LTTA), University of Ferrara, Ferrara, Italy
| | - Luigi Sbano
- Department of Morphology, Surgery and Experimental Medicine, Section of Pathology, Oncology and Experimental Biology, Laboratory for Technologies of Advanced Therapies (LTTA), University of Ferrara, Ferrara, Italy
| | - Alessandro Rimessi
- Department of Morphology, Surgery and Experimental Medicine, Section of Pathology, Oncology and Experimental Biology, Laboratory for Technologies of Advanced Therapies (LTTA), University of Ferrara, Ferrara, Italy
| | - Martijn Kerkhofs
- Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine and Leuven Kanker Instituut, KU Leuven, Campus Gasthuisberg O&N-I box 802, Herestraat 49, B-3000, Leuven, Belgium
| | - Jan B Parys
- Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine and Leuven Kanker Instituut, KU Leuven, Campus Gasthuisberg O&N-I box 802, Herestraat 49, B-3000, Leuven, Belgium
| | - Geert Bultynck
- Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine and Leuven Kanker Instituut, KU Leuven, Campus Gasthuisberg O&N-I box 802, Herestraat 49, B-3000, Leuven, Belgium
| | - Carlotta Giorgi
- Department of Morphology, Surgery and Experimental Medicine, Section of Pathology, Oncology and Experimental Biology, Laboratory for Technologies of Advanced Therapies (LTTA), University of Ferrara, Ferrara, Italy.
| | - Paolo Pinton
- Department of Morphology, Surgery and Experimental Medicine, Section of Pathology, Oncology and Experimental Biology, Laboratory for Technologies of Advanced Therapies (LTTA), University of Ferrara, Ferrara, Italy.
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48
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ER-luminal thiol/selenol-mediated regulation of Ca2+ signalling. Biochem Soc Trans 2016; 44:452-9. [PMID: 27068954 DOI: 10.1042/bst20150233] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Indexed: 01/05/2023]
Abstract
The endoplasmic reticulum (ER) is the main cellular Ca(2+)storage unit. Among other signalling outputs, the ER can release Ca(2+)ions, which can, for instance, communicate the status of ER protein folding to the cytosol and to other organelles, in particular the mitochondria. As a consequence, ER Ca(2+)flux can alter the apposition of the ER with mitochondria, influence mitochondrial ATP production or trigger apoptosis. All aspects of ER Ca(2+)flux have emerged as processes that are intimately controlled by intracellular redox conditions. In this review, we focus on ER-luminal redox-driven regulation of Ca(2+)flux. This involves the direct reduction of disulfides within ER Ca(2+)handling proteins themselves, but also the regulated interaction of ER chaperones and oxidoreductases such as calnexin or ERp57 with them. Well-characterized examples are the activating interactions of Ero1α with inositol 1,4,5-trisphosphate receptors (IP3Rs) or of selenoprotein N (SEPN1) with sarco/endoplasmic reticulum Ca(2+)transport ATPase 2 (SERCA2). The future discovery of novel ER-luminal modulators of Ca(2+)handling proteins is likely. Based on the currently available information, we describe how the variable ER redox conditions govern Ca(2+)flux from the ER.
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49
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Gomez-Navarro N, Miller E. Protein sorting at the ER-Golgi interface. J Cell Biol 2016; 215:769-778. [PMID: 27903609 PMCID: PMC5166505 DOI: 10.1083/jcb.201610031] [Citation(s) in RCA: 184] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Revised: 11/02/2016] [Accepted: 11/17/2016] [Indexed: 01/01/2023] Open
Abstract
In this review, Gomez-Navarro and Miller summarize the principles of cargo sorting by the vesicle traffic machinery and consider the diverse mechanisms by which cargo proteins are selected and captured into different transport vesicles. Protein traffic is of critical importance for normal cellular physiology. In eukaryotes, spherical transport vesicles move proteins and lipids from one internal membrane-bound compartment to another within the secretory pathway. The process of directing each individual protein to a specific destination (known as protein sorting) is a crucial event that is intrinsically linked to vesicle biogenesis. In this review, we summarize the principles of cargo sorting by the vesicle traffic machinery and consider the diverse mechanisms by which cargo proteins are selected and captured into different transport vesicles. We focus on the first two compartments of the secretory pathway: the endoplasmic reticulum and Golgi. We provide an overview of the complexity and diversity of cargo adaptor function and regulation, focusing on recent mechanistic discoveries that have revealed insight into protein sorting in cells.
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Affiliation(s)
- Natalia Gomez-Navarro
- Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, England, UK
| | - Elizabeth Miller
- Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, England, UK
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50
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Crystal Structure of the ERp44-Peroxiredoxin 4 Complex Reveals the Molecular Mechanisms of Thiol-Mediated Protein Retention. Structure 2016; 24:1755-1765. [PMID: 27642162 DOI: 10.1016/j.str.2016.08.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Revised: 07/22/2016] [Accepted: 08/05/2016] [Indexed: 12/23/2022]
Abstract
ERp44 controls the localization and transport of diverse proteins in the early secretory pathway. The mechanisms that allow client recognition and the source of the oxidative power for forming intermolecular disulfides are as yet unknown. Here we present the structure of ERp44 bound to a client, peroxiredoxin 4. Our data reveal that ERp44 binds the oxidized form of peroxiredoxin 4 via thiol-disulfide interchange reactions. The structure explains the redox-dependent recognition and characterizes the essential non-covalent interactions at the interface. The ERp44-Prx4 covalent complexes can be reduced by glutathione and protein disulfide isomerase family members in the ER, allowing the two components to recycle. This work provides insights into the mechanisms of thiol-mediated protein retention and indicates the key roles of ERp44 in this biochemical cycle to optimize oxidative folding and redox homeostasis.
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