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Tax G, Guay KP, Pantalone L, Ceci M, Soldà T, Hitchman CJ, Hill JC, Vasiljević S, Lia A, Modenutti CP, Straatman KR, Santino A, Molinari M, Zitzmann N, Hebert DN, Roversi P, Trerotola M. Rescue of secretion of rare-disease-associated misfolded mutant glycoproteins in UGGT1 knock-out mammalian cells. Traffic 2024; 25:e12927. [PMID: 38272446 PMCID: PMC10832616 DOI: 10.1111/tra.12927] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2023] [Revised: 11/02/2023] [Accepted: 12/05/2023] [Indexed: 01/27/2024]
Abstract
Endoplasmic reticulum (ER) retention of misfolded glycoproteins is mediated by the ER-localized eukaryotic glycoprotein secretion checkpoint, UDP-glucose glycoprotein glucosyl-transferase (UGGT). The enzyme recognizes a misfolded glycoprotein and flags it for ER retention by re-glucosylating one of its N-linked glycans. In the background of a congenital mutation in a secreted glycoprotein gene, UGGT-mediated ER retention can cause rare disease, even if the mutant glycoprotein retains activity ("responsive mutant"). Using confocal laser scanning microscopy, we investigated here the subcellular localization of the human Trop-2-Q118E, E227K and L186P mutants, which cause gelatinous drop-like corneal dystrophy (GDLD). Compared with the wild-type Trop-2, which is correctly localized at the plasma membrane, these Trop-2 mutants are retained in the ER. We studied fluorescent chimeras of the Trop-2 Q118E, E227K and L186P mutants in mammalian cells harboring CRISPR/Cas9-mediated inhibition of the UGGT1 and/or UGGT2 genes. The membrane localization of the Trop-2 Q118E, E227K and L186P mutants was successfully rescued in UGGT1-/- cells. UGGT1 also efficiently reglucosylated Trop-2-Q118E-EYFP in cellula. The study supports the hypothesis that UGGT1 modulation would constitute a novel therapeutic strategy for the treatment of pathological conditions associated to misfolded membrane glycoproteins (whenever the mutation impairs but does not abrogate function), and it encourages the testing of modulators of ER glycoprotein folding quality control as broad-spectrum rescue-of-secretion drugs in rare diseases caused by responsive secreted glycoprotein mutants.
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Affiliation(s)
- Gabor Tax
- Leicester Institute of Chemical and Structural Biology and Department of Molecular and Cell Biology, University of Leicester, Henry Wellcome Building, Lancaster Road, Leicester LE1 7HR, England, United Kingdom
| | - Kevin P. Guay
- Department of Biochemistry and Molecular Biology, and Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, United States
| | - Ludovica Pantalone
- Department of Medical, Oral and Biotechnological Sciences, "G. d'Annunzio" University of Chieti-Pescara, Italy; Laboratory of Cancer Pathology, Center for Advanced Studies and Technology (CAST), "G. d'Annunzio" University of Chieti-Pescara, Italy
| | - Martina Ceci
- Department of Medical, Oral and Biotechnological Sciences, "G. d'Annunzio" University of Chieti-Pescara, Italy; Laboratory of Cancer Pathology, Center for Advanced Studies and Technology (CAST), "G. d'Annunzio" University of Chieti-Pescara, Italy
| | - Tatiana Soldà
- Institute for Research in Biomedicine, Faculty of Biomedical Sciences, UniversitàdellaSvizzeraItaliana (USI), Bellinzona, Switzerland
| | - Charlie J. Hitchman
- Leicester Institute of Chemical and Structural Biology and Department of Molecular and Cell Biology, University of Leicester, Henry Wellcome Building, Lancaster Road, Leicester LE1 7HR, England, United Kingdom
| | - Johan C. Hill
- Institute of Glycobiology, Department of Biochemistry, South Parks Road, Oxford OX1 3RQ, United Kingdom
| | - Snežana Vasiljević
- Institute of Glycobiology, Department of Biochemistry, South Parks Road, Oxford OX1 3RQ, United Kingdom
| | - Andrea Lia
- Leicester Institute of Chemical and Structural Biology and Department of Molecular and Cell Biology, University of Leicester, Henry Wellcome Building, Lancaster Road, Leicester LE1 7HR, England, United Kingdom
- Institute of Sciences of Food Production, ISPA-CNR Unit of Lecce, via Monteroni, I-73100 Lecce, Italy
| | - Carlos P. Modenutti
- Departamento de QuímicaBiológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (FCEyN-UBA) e Instituto de QuímicaBiológica de la Facultad de Ciencias Exactas y Naturales (IQUIBICEN) CONICET, Pabellón 2 de Ciudad Universitaria, Ciudad de Buenos Aires C1428EHA, Argentina
| | - Kees R. Straatman
- Core Biotechnology Services, University of Leicester, University Road, Leicester LE1 7RH, England, United Kingdom
| | - Angelo Santino
- Institute of Sciences of Food Production, ISPA-CNR Unit of Lecce, via Monteroni, I-73100 Lecce, Italy
| | - Maurizio Molinari
- Institute of Glycobiology, Department of Biochemistry, South Parks Road, Oxford OX1 3RQ, United Kingdom
- School of Life Sciences, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Nicole Zitzmann
- Institute of Glycobiology, Department of Biochemistry, South Parks Road, Oxford OX1 3RQ, United Kingdom
| | - Daniel N. Hebert
- Department of Biochemistry and Molecular Biology, and Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, United States
| | - Pietro Roversi
- Leicester Institute of Chemical and Structural Biology and Department of Molecular and Cell Biology, University of Leicester, Henry Wellcome Building, Lancaster Road, Leicester LE1 7HR, England, United Kingdom
- Institute of AgriculturalBiology and Biotecnology, IBBA-CNR Unit of Milano, via Bassini 15, I-20133 Milano, Italy
| | - Marco Trerotola
- Department of Medical, Oral and Biotechnological Sciences, "G. d'Annunzio" University of Chieti-Pescara, Italy; Laboratory of Cancer Pathology, Center for Advanced Studies and Technology (CAST), "G. d'Annunzio" University of Chieti-Pescara, Italy
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Guay KP, Ibba R, Kiappes J, Vasiljević S, Bonì F, De Benedictis M, Zeni I, Le Cornu JD, Hensen M, Chandran AV, Kantsadi AL, Caputo AT, Blanco Capurro JI, Bayo Y, Hill JC, Hudson K, Lia A, Brun J, Withers SG, Martí M, Biasini E, Santino A, De Rosa M, Milani M, Modenutti CP, Hebert DN, Zitzmann N, Roversi P. A quinolin-8-ol sub-millimolar inhibitor of UGGT, the ER glycoprotein folding quality control checkpoint. iScience 2023; 26:107919. [PMID: 37822503 PMCID: PMC10562782 DOI: 10.1016/j.isci.2023.107919] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Revised: 07/05/2023] [Accepted: 09/12/2023] [Indexed: 10/13/2023] Open
Abstract
Misfolded glycoprotein recognition and endoplasmic reticulum (ER) retention are mediated by the ER glycoprotein folding quality control (ERQC) checkpoint enzyme, UDP-glucose glycoprotein glucosyltransferase (UGGT). UGGT modulation is a promising strategy for broad-spectrum antivirals, rescue-of-secretion therapy in rare disease caused by responsive mutations in glycoprotein genes, and many cancers, but to date no selective UGGT inhibitors are known. The small molecule 5-[(morpholin-4-yl)methyl]quinolin-8-ol (5M-8OH-Q) binds a CtUGGTGT24 "WY" conserved surface motif conserved across UGGTs but not present in other GT24 family glycosyltransferases. 5M-8OH-Q has a 47 μM binding affinity for CtUGGTGT24in vitro as measured by ligand-enhanced fluorescence. In cellula, 5M-8OH-Q inhibits both human UGGT isoforms at concentrations higher than 750 μM. 5M-8OH-Q binding to CtUGGTGT24 appears to be mutually exclusive to M5-9 glycan binding in an in vitro competition experiment. A medicinal program based on 5M-8OH-Q will yield the next generation of UGGT inhibitors.
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Affiliation(s)
- Kevin P. Guay
- Department of Biochemistry and Molecular Biology, and Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, MA, USA
| | - Roberta Ibba
- Oxford Glycobiology Institute, Department of Biochemistry and Kavli Institute for Nanoscience Discovery, South Parks Road, Oxford OX1 3QU, UK
- Department of Medicine, Surgery and Pharmacy, University of Sassari, Via Muroni 23A, 07100 Sassari, Italy
| | - J.L. Kiappes
- Oxford Glycobiology Institute, Department of Biochemistry and Kavli Institute for Nanoscience Discovery, South Parks Road, Oxford OX1 3QU, UK
| | - Snežana Vasiljević
- Oxford Glycobiology Institute, Department of Biochemistry and Kavli Institute for Nanoscience Discovery, South Parks Road, Oxford OX1 3QU, UK
| | - Francesco Bonì
- Institute of Biophysics, IBF-CNR Unit of Milano, via Celoria 26, 20133 Milano, Italy
| | - Maria De Benedictis
- Institute of Sciences of Food Production, C.N.R. Unit of Lecce, via Monteroni, 73100 Lecce, Italy
| | - Ilaria Zeni
- Department of Cellular, Computational and Integrative Biology, University of Trento, Povo, 38123 Trento, Italy
| | - James D. Le Cornu
- Wellcome Centre for Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, Scotland, United Kingdom
| | - Mario Hensen
- Oxford Glycobiology Institute, Department of Biochemistry and Kavli Institute for Nanoscience Discovery, South Parks Road, Oxford OX1 3QU, UK
| | - Anu V. Chandran
- Oxford Glycobiology Institute, Department of Biochemistry and Kavli Institute for Nanoscience Discovery, South Parks Road, Oxford OX1 3QU, UK
| | - Anastassia L. Kantsadi
- Oxford Glycobiology Institute, Department of Biochemistry and Kavli Institute for Nanoscience Discovery, South Parks Road, Oxford OX1 3QU, UK
| | - Alessandro T. Caputo
- Biomedical Manufacturing, Commonwealth Scientific and Industrial Research Organisation, 343 Royal Parade, Parkville, VIC 3052, Australia
| | - Juan I. Blanco Capurro
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II (CE1428EHA), Buenos Aires, Argentina
- Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales (IQUIBICEN) CONICET, Ciudad Universitaria, Pab. II (CE1428EHA), Buenos Aires, Argentina
| | - Yusupha Bayo
- Department of Biosciences, University of Milano, via Celoria 26, 20133 Milano, Italy
| | - Johan C. Hill
- Oxford Glycobiology Institute, Department of Biochemistry and Kavli Institute for Nanoscience Discovery, South Parks Road, Oxford OX1 3QU, UK
| | - Kieran Hudson
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
| | - Andrea Lia
- Oxford Glycobiology Institute, Department of Biochemistry and Kavli Institute for Nanoscience Discovery, South Parks Road, Oxford OX1 3QU, UK
- Institute of Biophysics, IBF-CNR Unit of Milano, via Celoria 26, 20133 Milano, Italy
| | - Juliane Brun
- Oxford Glycobiology Institute, Department of Biochemistry and Kavli Institute for Nanoscience Discovery, South Parks Road, Oxford OX1 3QU, UK
| | - Stephen G. Withers
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
| | - Marcelo Martí
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II (CE1428EHA), Buenos Aires, Argentina
- Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales (IQUIBICEN) CONICET, Ciudad Universitaria, Pab. II (CE1428EHA), Buenos Aires, Argentina
| | - Emiliano Biasini
- Department of Cellular, Computational and Integrative Biology, University of Trento, Povo, 38123 Trento, Italy
- Dulbecco Telethon Institute, University of Trento, Povo, 38123 Trento, Italy
| | - Angelo Santino
- Institute of Sciences of Food Production, C.N.R. Unit of Lecce, via Monteroni, 73100 Lecce, Italy
| | - Matteo De Rosa
- Institute of Biophysics, IBF-CNR Unit of Milano, via Celoria 26, 20133 Milano, Italy
| | - Mario Milani
- Institute of Biophysics, IBF-CNR Unit of Milano, via Celoria 26, 20133 Milano, Italy
| | - Carlos P. Modenutti
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II (CE1428EHA), Buenos Aires, Argentina
- Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales (IQUIBICEN) CONICET, Ciudad Universitaria, Pab. II (CE1428EHA), Buenos Aires, Argentina
| | - Daniel N. Hebert
- Department of Biochemistry and Molecular Biology, and Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, MA, USA
| | - Nicole Zitzmann
- Oxford Glycobiology Institute, Department of Biochemistry and Kavli Institute for Nanoscience Discovery, South Parks Road, Oxford OX1 3QU, UK
| | - Pietro Roversi
- Institute of Agricultural Biology and Biotechnology, IBBA-CNR Unit of Milano, via Bassini 15, 20133 Milano, Italy
- Leicester Institute of Chemical and Structural Biology and Department of Molecular and Cell Biology, University of Leicester, Henry Wellcome Building, Lancaster Road, LE1 7HR Leicester, UK
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Tax G, Guay KP, Soldà T, Hitchman CJ, Hill JC, Vasiljević S, Lia A, Modenutti CP, Straatman KR, Santino A, Molinari M, Zitzmann N, Hebert DN, Roversi P, Trerotola M. Rescue of secretion of a rare-disease associated mis-folded mutant glycoprotein in UGGT1 knock-out mammalian cells. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.30.542711. [PMID: 37398215 PMCID: PMC10312515 DOI: 10.1101/2023.05.30.542711] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2023]
Abstract
Endoplasmic reticulum (ER) retention of mis-folded glycoproteins is mediated by the ERlocalised eukaryotic glycoprotein secretion checkpoint, UDP-glucose glycoprotein glucosyl-transferase (UGGT). The enzyme recognises a mis-folded glycoprotein and flags it for ER retention by reglucosylating one of its N-linked glycans. In the background of a congenital mutation in a secreted glycoprotein gene, UGGT-mediated ER retention can cause rare disease even if the mutant glycoprotein retains activity ("responsive mutant"). Here, we investigated the subcellular localisation of the human Trop-2 Q118E variant, which causes gelatinous droplike corneal dystrophy (GDLD). Compared with the wild type Trop-2, which is correctly localised at the plasma membrane, the Trop-2-Q118E variant is found to be heavily retained in the ER. Using Trop-2-Q118E, we tested UGGT modulation as a rescue-of-secretion therapeutic strategy for congenital rare disease caused by responsive mutations in genes encoding secreted glycoproteins. We investigated secretion of a EYFP-fusion of Trop-2-Q118E by confocal laser scanning microscopy. As a limiting case of UGGT inhibition, mammalian cells harbouring CRISPR/Cas9-mediated inhibition of the UGGT1 and/or UGGT2 gene expressions were used. The membrane localisation of the Trop-2-Q118E-EYFP mutant was successfully rescued in UGGT1-/- and UGGT1/2-/- cells. UGGT1 also efficiently reglucosylated Trop-2-Q118E-EYFP in cellula. The study supports the hypothesis that UGGT1 modulation constitutes a novel therapeutic strategy for the treatment of Trop-2-Q118E associated GDLD, and it encourages the testing of modulators of ER glycoprotein folding Quality Control (ERQC) as broad-spectrum rescueof-secretion drugs in rare diseases caused by responsive secreted glycoprotein mutants.
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Affiliation(s)
- Gábor Tax
- Leicester Institute of Chemical and Structural Biology and Department of Molecular and Cell Biology, University of Leicester, Henry Wellcome Building, Lancaster Road, Leicester LE1 7HR, England, United Kingdom
| | - Kevin P. Guay
- Department of Biochemistry and Molecular Biology, and Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, United States
| | - Tatiana Soldà
- Institute for Research in Biomedicine, Faculty of Biomedical Sciences, Università della Svizzera Italiana (USI), Bellinzona, Switzerland
| | - Charlie J. Hitchman
- Leicester Institute of Chemical and Structural Biology and Department of Molecular and Cell Biology, University of Leicester, Henry Wellcome Building, Lancaster Road, Leicester LE1 7HR, England, United Kingdom
| | - Johan C. Hill
- Institute of Glycobiology, Department of Biochemistry, South Parks Road, Oxford OX1 3RQ, United Kingdom
| | - Snežana Vasiljević
- Institute of Glycobiology, Department of Biochemistry, South Parks Road, Oxford OX1 3RQ, United Kingdom
| | - Andrea Lia
- Leicester Institute of Chemical and Structural Biology and Department of Molecular and Cell Biology, University of Leicester, Henry Wellcome Building, Lancaster Road, Leicester LE1 7HR, England, United Kingdom
- Institute of Sciences of Food Production, ISPA-CNR Unit of Lecce, via Monteroni, I-73100 Lecce, Italy
| | - Carlos P. Modenutti
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (FCEyN-UBA) e Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales (IQUIBICEN) CONICET, Pabellón 2 de Ciudad Universitaria, Ciudad de Buenos Aires C1428EHA, Argentina
| | - Kees R. Straatman
- Leicester Institute of Chemical and Structural Biology and Department of Molecular and Cell Biology, University of Leicester, Henry Wellcome Building, Lancaster Road, Leicester LE1 7HR, England, United Kingdom
- Core Biotechnology Services, University of Leicester, University Road, Leicester LE1 7RH, England, United Kingdom
| | - Angelo Santino
- Institute of Sciences of Food Production, ISPA-CNR Unit of Lecce, via Monteroni, I-73100 Lecce, Italy
| | - Maurizio Molinari
- Institute of Glycobiology, Department of Biochemistry, South Parks Road, Oxford OX1 3RQ, United Kingdom
- School of Life Sciences, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Nicole Zitzmann
- Institute of Glycobiology, Department of Biochemistry, South Parks Road, Oxford OX1 3RQ, United Kingdom
| | - Daniel N. Hebert
- Department of Biochemistry and Molecular Biology, and Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, United States
| | - Pietro Roversi
- Leicester Institute of Chemical and Structural Biology and Department of Molecular and Cell Biology, University of Leicester, Henry Wellcome Building, Lancaster Road, Leicester LE1 7HR, England, United Kingdom
- Institute of Agricultural Biology and Biotecnology, IBBACNR Unit of Milano, via Bassini 15, I-20133 Milano, Italy
| | - Marco Trerotola
- Department of Medical, Oral and Biotechnological Sciences, “G. d’Annunzio” University of Chieti-Pescara, Italy; Laboratory of Cancer Pathology, Center for Advanced Studies and Technology (CAST), “G. d’Annunzio” University of Chieti-Pescara, Italy
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Deejai N, Sawasdee N, Nettuwakul C, Wanachiwanawin W, Sritippayawan S, Yenchitsomanus PT, Rungroj N. Impaired trafficking and instability of mutant kidney anion exchanger 1 proteins associated with autosomal recessive distal renal tubular acidosis. BMC Med Genomics 2022; 15:228. [PMID: 36320073 PMCID: PMC9623938 DOI: 10.1186/s12920-022-01381-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Accepted: 10/21/2022] [Indexed: 11/06/2022] Open
Abstract
Background Mutations in solute carrier family 4 member 1 (SLC4A1) encoding anion exchanger 1 (AE1) are the most common cause of autosomal recessive distal renal tubular acidosis (AR dRTA) in Southeast Asians. To explain the molecular mechanism of this disease with hematological abnormalities in an affected family, we conducted a genetic analysis of SLC4A1 and studied wild-type and mutant AE1 proteins expressed in human embryonic kidney 293T (HEK293T) cells. Methods SLC4A1 mutations in the patient and family members were analyzed by molecular genetic techniques. Protein structure modeling was initially conducted to evaluate the effects of mutations on the three-dimensional structure of the AE1 protein. The mutant kidney anion exchanger 1 (kAE1) plasmid construct was created to study protein expression, localization, and stability in HEK293T cells. Results We discovered that the patient who had AR dRTA coexisting with mild hemolytic anemia carried a novel compound heterozygous SLC4A1 mutations containing c.1199_1225del (p.Ala400_Ala408del), resulting in Southeast Asian ovalocytosis (SAO), and c.1331C > A (p.Thr444Asn). Homologous modeling and in silico mutagenesis indicated that these two mutations affected the protein structure in the transmembrane regions of kAE1. We found the wild-type and mutant kAE1 T444N to be localized at the cell surface, whereas the mutants kAE1 SAO and SAO/T444N were intracellularly retained. The half-life of the kAE1 SAO, T444N, and SAO/T444N mutants was shorter than that of the wild-type protein. Conclusion These results suggest impaired trafficking and instability of kAE1 SAO/T444N as the likely underlying molecular mechanism explaining the pathogenesis of the novel SLC4A1 compound heterozygous mutation identified in this patient. Supplementary Information The online version contains supplementary material available at 10.1186/s12920-022-01381-y.
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Affiliation(s)
- Nipaporn Deejai
- grid.10223.320000 0004 1937 0490Division of Molecular Medicine, Research Department, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
| | - Nunghathai Sawasdee
- grid.10223.320000 0004 1937 0490Division of Molecular Medicine, Research Department, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
| | - Choochai Nettuwakul
- grid.10223.320000 0004 1937 0490Division of Molecular Medicine, Research Department, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
| | - Wanchai Wanachiwanawin
- grid.10223.320000 0004 1937 0490Division of Hematology, Department of Medicine, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
| | - Suchai Sritippayawan
- grid.10223.320000 0004 1937 0490Division of Nephrology, Department of Medicine, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
| | - Pa-thai Yenchitsomanus
- grid.10223.320000 0004 1937 0490Division of Molecular Medicine, Research Department, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
| | - Nanyawan Rungroj
- grid.10223.320000 0004 1937 0490Siriraj Genomics, Office of the Dean, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
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Parray ZA, Shahid M, Islam A. Insights into Fluctuations of Structure of Proteins: Significance of Intermediary States in Regulating Biological Functions. Polymers (Basel) 2022; 14:polym14081539. [PMID: 35458289 PMCID: PMC9025146 DOI: 10.3390/polym14081539] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Revised: 03/30/2022] [Accepted: 04/05/2022] [Indexed: 02/01/2023] Open
Abstract
Proteins are indispensable to cellular communication and metabolism. The structure on which cells and tissues are developed is deciphered from proteins. To perform functions, proteins fold into a three-dimensional structural design, which is specific and fundamentally determined by their characteristic sequence of amino acids. Few of them have structural versatility, allowing them to adapt their shape to the task at hand. The intermediate states appear momentarily, while protein folds from denatured (D) ⇔ native (N), which plays significant roles in cellular functions. Prolific effort needs to be taken in characterizing these intermediate species if detected during the folding process. Protein folds into its native structure through definite pathways, which involve a limited number of transitory intermediates. Intermediates may be essential in protein folding pathways and assembly in some cases, as well as misfolding and aggregation folding pathways. These intermediate states help to understand the machinery of proper folding in proteins. In this review article, we highlight the various intermediate states observed and characterized so far under in vitro conditions. Moreover, the role and significance of intermediates in regulating the biological function of cells are discussed clearly.
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Affiliation(s)
- Zahoor Ahmad Parray
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi 110025, India;
- Department of Chemistry, Indian Institute of Technology Delhi, IIT Campus, Hauz Khas, New Delhi 110016, India
| | - Mohammad Shahid
- Department of Basic Medical Sciences, College of Medicine, Prince Sattam bin Abdulaziz University, Al Kharj 11942, Saudi Arabia;
| | - Asimul Islam
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi 110025, India;
- Correspondence: ; Tel.: +91-93-1281-2007
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Caputo AT, Ibba R, Le Cornu JD, Darlot B, Hensen M, Lipp CB, Marcianò G, Vasiljević S, Zitzmann N, Roversi P. Crystal polymorphism in fragment-based lead discovery of ligands of the catalytic domain of UGGT, the glycoprotein folding quality control checkpoint. Front Mol Biosci 2022; 9:960248. [PMID: 36589243 PMCID: PMC9794592 DOI: 10.3389/fmolb.2022.960248] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Accepted: 11/11/2022] [Indexed: 12/15/2022] Open
Abstract
None of the current data processing pipelines for X-ray crystallography fragment-based lead discovery (FBLD) consults all the information available when deciding on the lattice and symmetry (i.e., the polymorph) of each soaked crystal. Often, X-ray crystallography FBLD pipelines either choose the polymorph based on cell volume and point-group symmetry of the X-ray diffraction data or leave polymorph attribution to manual intervention on the part of the user. Thus, when the FBLD crystals belong to more than one crystal polymorph, the discovery pipeline can be plagued by space group ambiguity, especially if the polymorphs at hand are variations of the same lattice and, therefore, difficult to tell apart from their morphology and/or their apparent crystal lattices and point groups. In the course of a fragment-based lead discovery effort aimed at finding ligands of the catalytic domain of UDP-glucose glycoprotein glucosyltransferase (UGGT), we encountered a mixture of trigonal crystals and pseudotrigonal triclinic crystals-with the two lattices closely related. In order to resolve that polymorphism ambiguity, we have written and described here a series of Unix shell scripts called CoALLA (crystal polymorph and ligand likelihood-based assignment). The CoALLA scripts are written in Unix shell and use autoPROC for data processing, CCP4-Dimple/REFMAC5 and BUSTER for refinement, and RHOFIT for ligand docking. The choice of the polymorph is effected by carrying out (in each of the known polymorphs) the tasks of diffraction data indexing, integration, scaling, and structural refinement. The most likely polymorph is then chosen as the one with the best structure refinement Rfree statistic. The CoALLA scripts further implement a likelihood-based ligand assignment strategy, starting with macromolecular refinement and automated water addition, followed by removal of the water molecules that appear to be fitting ligand density, and a final round of refinement after random perturbation of the refined macromolecular model, in order to obtain unbiased difference density maps for automated ligand placement. We illustrate the use of CoALLA to discriminate between H3 and P1 crystals used for an FBLD effort to find fragments binding to the catalytic domain of Chaetomium thermophilum UGGT.
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Affiliation(s)
- Alessandro T. Caputo
- Biochemistry Department, Oxford Glycobiology Institute, University of Oxford, Oxford, United Kingdom
- Commonwealth Scientific and Industrial Research Organisation, Clayton, VIC, Australia
| | - Roberta Ibba
- Biochemistry Department, Oxford Glycobiology Institute, University of Oxford, Oxford, United Kingdom
- Department of Medicine, Surgery and Pharmacy, University of Sassari, Sassari, Italy
| | - James D. Le Cornu
- Biochemistry Department, Oxford Glycobiology Institute, University of Oxford, Oxford, United Kingdom
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Scotland, United Kingdom
| | - Benoit Darlot
- Biochemistry Department, Oxford Glycobiology Institute, University of Oxford, Oxford, United Kingdom
| | - Mario Hensen
- Biochemistry Department, Oxford Glycobiology Institute, University of Oxford, Oxford, United Kingdom
| | - Colette B. Lipp
- Biochemistry Department, Oxford Glycobiology Institute, University of Oxford, Oxford, United Kingdom
| | - Gabriele Marcianò
- Biochemistry Department, University of Oxford, Oxford, United Kingdom
| | - Snežana Vasiljević
- Biochemistry Department, Oxford Glycobiology Institute, University of Oxford, Oxford, United Kingdom
| | - Nicole Zitzmann
- Biochemistry Department, Oxford Glycobiology Institute, University of Oxford, Oxford, United Kingdom
- *Correspondence: Nicole Zitzmann, ; Pietro Roversi,
| | - Pietro Roversi
- IBBA-CNR Unit of Milano, Institute of Agricultural Biology and Biotechnology, Milano, Italy
- Department of Molecular and Cell Biology, Leicester Institute of Structural and Chemical Biology, University of Leicester, Leicester, United Kingdom
- *Correspondence: Nicole Zitzmann, ; Pietro Roversi,
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Shin J, Nile A, Oh JW. Role of adaptin protein complexes in intracellular trafficking and their impact on diseases. Bioengineered 2021; 12:8259-8278. [PMID: 34565296 PMCID: PMC8806629 DOI: 10.1080/21655979.2021.1982846] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2021] [Revised: 09/15/2021] [Accepted: 09/15/2021] [Indexed: 02/07/2023] Open
Abstract
Adaptin proteins (APs) play a crucial role in intracellular cell trafficking. The 'classical' role of APs is carried out by AP1‒3, which bind to clathrin, cargo, and accessory proteins. Accordingly, AP1-3 are crucial for both vesicle formation and sorting. All APs consist of four subunits that are indispensable for their functions. In fact, based on studies using cells, model organism knockdown/knock-out, and human variants, each subunit plays crucial roles and contributes to the specificity of each AP. These studies also revealed that the sorting and intracellular trafficking function of AP can exert varying effects on pathology by controlling features such as cell development, signal transduction related to the apoptosis and proliferation pathways in cancer cells, organelle integrity, receptor presentation, and viral infection. Although the roles and functions of AP1‒3 are relatively well studied, the functions of the less abundant and more recently identified APs, AP4 and AP5, are still to be investigated. Further studies on these APs may enable a better understanding and targeting of specific diseases.APs known or suggested locations and functions.
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Affiliation(s)
- Juhyun Shin
- Department of Stem Cell and Regenerative Biotechnology and Animal Resources Research Center, Konkuk University, Seoul, Republic of Korea
| | - Arti Nile
- Department of Stem Cell and Regenerative Biotechnology and Animal Resources Research Center, Konkuk University, Seoul, Republic of Korea
| | - Jae-Wook Oh
- Department of Stem Cell and Regenerative Biotechnology and Animal Resources Research Center, Konkuk University, Seoul, Republic of Korea
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8
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Modenutti CP, Blanco Capurro JI, Ibba R, Alonzi DS, Song MN, Vasiljević S, Kumar A, Chandran AV, Tax G, Marti L, Hill JC, Lia A, Hensen M, Waksman T, Rushton J, Rubichi S, Santino A, Martí MA, Zitzmann N, Roversi P. Clamping, bending, and twisting inter-domain motions in the misfold-recognizing portion of UDP-glucose: Glycoprotein glucosyltransferase. Structure 2021; 29:357-370.e9. [PMID: 33352114 PMCID: PMC8024514 DOI: 10.1016/j.str.2020.11.017] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Revised: 09/07/2020] [Accepted: 11/24/2020] [Indexed: 12/27/2022]
Abstract
UDP-glucose:glycoprotein glucosyltransferase (UGGT) flags misfolded glycoproteins for ER retention. We report crystal structures of full-length Chaetomium thermophilum UGGT (CtUGGT), two CtUGGT double-cysteine mutants, and its TRXL2 domain truncation (CtUGGT-ΔTRXL2). CtUGGT molecular dynamics (MD) simulations capture extended conformations and reveal clamping, bending, and twisting inter-domain movements. We name "Parodi limit" the maximum distance on the same glycoprotein between a site of misfolding and an N-linked glycan that can be reglucosylated by monomeric UGGT in vitro, in response to recognition of misfold at that site. Based on the MD simulations, we estimate the Parodi limit as around 70-80 Å. Frequency distributions of distances between glycoprotein residues and their closest N-linked glycosylation sites in glycoprotein crystal structures suggests relevance of the Parodi limit to UGGT activity in vivo. Our data support a "one-size-fits-all adjustable spanner" UGGT substrate recognition model, with an essential role for the UGGT TRXL2 domain.
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Affiliation(s)
- Carlos P Modenutti
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II (CE1428EHA), Buenos Aires, Argentina; Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales (IQUIBICEN) CONICET. Ciudad Universitaria, Pab. II (CE1428EHA), Buenos Aires, Argentina
| | - Juan I Blanco Capurro
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II (CE1428EHA), Buenos Aires, Argentina; Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales (IQUIBICEN) CONICET. Ciudad Universitaria, Pab. II (CE1428EHA), Buenos Aires, Argentina
| | - Roberta Ibba
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK; Dipartimento di Chimica e Farmacia, Università degli Studi di Sassari, Via Muroni 23A, 07100 Sassari, SS, Italy
| | - Dominic S Alonzi
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Mauro N Song
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II (CE1428EHA), Buenos Aires, Argentina; Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales (IQUIBICEN) CONICET. Ciudad Universitaria, Pab. II (CE1428EHA), Buenos Aires, Argentina
| | - Snežana Vasiljević
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Abhinav Kumar
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Anu V Chandran
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Gabor Tax
- Leicester Institute of Structural and Chemical Biology, Department of Molecular and Cell Biology, University of Leicester, Henry Wellcome Building, Lancaster Road, Leicester, LE1 7RH,, UK
| | - Lucia Marti
- Institute of Sciences of Food Production, C.N.R. Unit of Lecce, via Monteroni, 73100 Lecce, Italy
| | - Johan C Hill
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Andrea Lia
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK; Leicester Institute of Structural and Chemical Biology, Department of Molecular and Cell Biology, University of Leicester, Henry Wellcome Building, Lancaster Road, Leicester, LE1 7RH,, UK; Institute of Sciences of Food Production, C.N.R. Unit of Lecce, via Monteroni, 73100 Lecce, Italy
| | - Mario Hensen
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Thomas Waksman
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Jonathan Rushton
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Simone Rubichi
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK; Institute of Sciences of Food Production, C.N.R. Unit of Lecce, via Monteroni, 73100 Lecce, Italy
| | - Angelo Santino
- Institute of Sciences of Food Production, C.N.R. Unit of Lecce, via Monteroni, 73100 Lecce, Italy
| | - Marcelo A Martí
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II (CE1428EHA), Buenos Aires, Argentina; Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales (IQUIBICEN) CONICET. Ciudad Universitaria, Pab. II (CE1428EHA), Buenos Aires, Argentina.
| | - Nicole Zitzmann
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK.
| | - Pietro Roversi
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK; Leicester Institute of Structural and Chemical Biology, Department of Molecular and Cell Biology, University of Leicester, Henry Wellcome Building, Lancaster Road, Leicester, LE1 7RH,, UK.
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9
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EFR-Mediated Innate Immune Response in Arabidopsis thaliana is a Useful Tool for Identification of Novel ERQC Modulators. Genes (Basel) 2018; 10:genes10010015. [PMID: 30591693 PMCID: PMC6357087 DOI: 10.3390/genes10010015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Revised: 12/19/2018] [Accepted: 12/19/2018] [Indexed: 01/28/2023] Open
Abstract
Plants offer a simpler and cheaper alternative to mammalian animal models for the study of endoplasmic reticulum glycoprotein folding quality control (ERQC). In particular, the Arabidopsis thaliana (At) innate immune response to bacterial peptides provides an easy means of assaying ERQC function in vivo. A number of mutants that are useful to study ERQC in planta have been described in the literature, but only for a subset of these mutants the innate immune response to bacterial elicitors has been measured beyond monitoring plant weight and some physio-pathological parameters related to the plant immune response. In order to probe deeper into the role of ERQC in the plant immune response, we monitored expression levels of the Phosphate-induced 1 (PHI-1) and reticulin-oxidase homologue (RET-OX) genes in the At ER α-Glu II rsw3 and the At UGGT uggt1-1 mutant plants, in response to bacterial peptides elf18 and flg22. The elf18 response was impaired in the rsw3 but not completely abrogated in the uggt1-1 mutant plants, raising the possibility that the latter enzyme is partly dispensable for EF-Tu receptor (EFR) signaling. In the rsw3 mutant, seedling growth was impaired only by concomitant application of the At ER α-Glu II NB-DNJ inhibitor at concentrations above 500 nM, compatibly with residual activity in this mutant. The study highlights the need for extending plant innate immune response studies to assays sampling EFR signaling at the molecular level.
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10
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Unique Roles of β-Arrestin in GPCR Trafficking Revealed by Photoinducible Dimerizers. Sci Rep 2018; 8:677. [PMID: 29330504 PMCID: PMC5766490 DOI: 10.1038/s41598-017-19130-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Accepted: 12/21/2017] [Indexed: 12/21/2022] Open
Abstract
Intracellular trafficking of G protein-coupled receptors (GPCRs) controls their localization and degradation, which affects a cell's ability to adapt to extracellular stimuli. Although the perturbation of trafficking induces important diseases, these trafficking mechanisms are poorly understood. Herein, we demonstrate an optogenetic method using an optical dimerizer, cryptochrome (CRY) and its partner protein (CIB), to analyze the trafficking mechanisms of GPCRs and their regulatory proteins. Temporally controlling the interaction between β-arrestin and β2-adrenergic receptor (ADRB2) reveals that the duration of the β-arrestin-ADRB2 interaction determines the trafficking pathway of ADRB2. Remarkably, the phosphorylation of ADRB2 by G protein-coupled receptor kinases is unnecessary to trigger clathrin-mediated endocytosis, and β-arrestin interacting with unphosphorylated ADRB2 fails to activate mitogen-activated protein kinase (MAPK) signaling, in contrast to the ADRB2 agonist isoproterenol. Temporal control of β-arrestin-GPCR interactions will enable the investigation of the unique roles of β-arrestin and the mechanism by which it regulates β-arrestin-specific trafficking pathways of different GPCRs.
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11
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Interdomain conformational flexibility underpins the activity of UGGT, the eukaryotic glycoprotein secretion checkpoint. Proc Natl Acad Sci U S A 2017; 114:8544-8549. [PMID: 28739903 DOI: 10.1073/pnas.1703682114] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Glycoproteins traversing the eukaryotic secretory pathway begin life in the endoplasmic reticulum (ER), where their folding is surveyed by the 170-kDa UDP-glucose:glycoprotein glucosyltransferase (UGGT). The enzyme acts as the single glycoprotein folding quality control checkpoint: it selectively reglucosylates misfolded glycoproteins, promotes their association with ER lectins and associated chaperones, and prevents premature secretion from the ER. UGGT has long resisted structural determination and sequence-based domain boundary prediction. Questions remain on how this single enzyme can flag misfolded glycoproteins of different sizes and shapes for ER retention and how it can span variable distances between the site of misfold and a glucose-accepting N-linked glycan on the same glycoprotein. Here, crystal structures of a full-length eukaryotic UGGT reveal four thioredoxin-like (TRXL) domains arranged in a long arc that terminates in two β-sandwiches tightly clasping the glucosyltransferase domain. The fold of the molecule is topologically complex, with the first β-sandwich and the fourth TRXL domain being encoded by nonconsecutive stretches of sequence. In addition to the crystal structures, a 15-Å cryo-EM reconstruction reveals interdomain flexibility of the TRXL domains. Double cysteine point mutants that engineer extra interdomain disulfide bridges rigidify the UGGT structure and exhibit impaired activity. The intrinsic flexibility of the TRXL domains of UGGT may therefore endow the enzyme with the promiscuity needed to recognize and reglucosylate its many different substrates and/or enable reglucosylation of N-linked glycans situated at variable distances from the site of misfold.
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12
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Protein traffic disorders: an effective high-throughput fluorescence microscopy pipeline for drug discovery. Sci Rep 2015; 5:9038. [PMID: 25762484 PMCID: PMC4356983 DOI: 10.1038/srep09038] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Accepted: 02/13/2015] [Indexed: 12/12/2022] Open
Abstract
Plasma membrane proteins are essential molecules in the cell which mediate interactions with the exterior milieu, thus representing key drug targets for present pharma. Not surprisingly, protein traffic disorders include a large range of diseases sharing the common mechanism of failure in the respective protein to reach the plasma membrane. However, specific therapies for these diseases are remarkably lacking. Herein, we report a robust platform for drug discovery applied to a paradigmatic genetic disorder affecting intracellular trafficking – Cystic Fibrosis. This platform includes (i) two original respiratory epithelial cellular models incorporating an inducible double-tagged traffic reporter; (ii) a plasma membrane protein traffic assay for high-throughput microscopy screening; and (iii) open-source image analysis software to quantify plasma membrane protein traffic. By allowing direct scoring of compounds rescuing the basic traffic defect, this platform enables an effective drug development pipeline, which can be promptly adapted to any traffic disorder-associated protein and leverage therapy development efforts.
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13
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Sharma A, Pohlentz G, Bobbili KB, Jeyaprakash AA, Chandran T, Mormann M, Swamy MJ, Vijayan M. The sequence and structure of snake gourd (Trichosanthes anguina) seed lectin, a three-chain nontoxic homologue of type II RIPs. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2013; 69:1493-503. [PMID: 23897472 DOI: 10.1107/s0907444913010020] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2012] [Accepted: 04/11/2013] [Indexed: 11/10/2022]
Abstract
The sequence and structure of snake gourd seed lectin (SGSL), a nontoxic homologue of type II ribosome-inactivating proteins (RIPs), have been determined by mass spectrometry and X-ray crystallography, respectively. As in type II RIPs, the molecule consists of a lectin chain made up of two β-trefoil domains. The catalytic chain, which is connected through a disulfide bridge to the lectin chain in type II RIPs, is cleaved into two in SGSL. However, the integrity of the three-dimensional structure of the catalytic component of the molecule is preserved. This is the first time that a three-chain RIP or RIP homologue has been observed. A thorough examination of the sequence and structure of the protein and of its interactions with the bound methyl-α-galactose indicate that the nontoxicity of SGSL results from a combination of changes in the catalytic and the carbohydrate-binding sites. Detailed analyses of the sequences of type II RIPs of known structure and their homologues with unknown structure provide valuable insights into the evolution of this class of proteins. They also indicate some variability in carbohydrate-binding sites, which appears to contribute to the different levels of toxicity exhibited by lectins from various sources.
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Affiliation(s)
- Alok Sharma
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560 012, Karnataka, India
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14
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Bhattacharyya S, Varadarajan R. Packing in molten globules and native states. Curr Opin Struct Biol 2012; 23:11-21. [PMID: 23270864 DOI: 10.1016/j.sbi.2012.10.010] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2012] [Accepted: 10/31/2012] [Indexed: 11/26/2022]
Abstract
Close packing of hydrophobic residues in the protein interior is an important determinant of protein stability. Cavities introduced by large to small substitutions are known to destabilize proteins. Conversely, native states of proteins and protein fragments can be stabilized by filling in existing cavities. Molten globules (MGs) were initially used to describe a state of protein which has well-defined secondary structure but little or no tertiary packing. Subsequent studies have shown that MGs do have some degree of native-like topology and specific packing. Wet molten globules (WMGs) with hydrated cores and considerably decreased packing relative to the native state have been studied extensively. Recently there has been renewed interest in identification and characterization of dry molten globules (DMGs). These are slightly expanded forms of the native state which show increased conformational flexibility, native-like main-chain hydrogen bonding and dry interiors. The generality of occurrence of DMGs during protein unfolding and the extent and nature of packing in DMGs remain to be elucidated. Packing interactions in native proteins and MGs can be probed through mutations. Next generation sequencing technologies make it possible to determine relative populations of mutants in a large pool. When this is coupled to phenotypic screens or cell-surface display, it becomes possible to rapidly examine large panels of single-site or multi-site mutants. From such studies, residue specific contributions to protein stability and function can be estimated in a highly parallelized fashion. This complements conventional biophysical methods for characterization of packing in native states and molten globules.
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15
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Cohen J, Gaw A, Barnes RI, Landschulz KT, Hobbs HH. Genetic factors that contribute to interindividual variations in plasma low density lipoprotein-cholesterol levels. CIBA FOUNDATION SYMPOSIUM 2007; 197:194-206; discussion 206-10. [PMID: 8827375 DOI: 10.1002/9780470514887.ch11] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The interplay of multiple genes and environmental factors generates interindividual variation in plasma low density lipoprotein-cholesterol (LDL-C) concentrations. As a result, it has been difficult to identify individual genes that contribute to variation in plasma LDL-C levels using classical linkage analysis. We have exploited a genetic defect in the gene encoding the LDL receptor that is associated with a dramatically elevated plasma LDL-C level to unmask an allele at another locus that lowers plasma LDL-C levels. The existence of such an allele was implied by the analysis of a human pedigree with familial hypercholesterolaemia in which a third of the familial hypercholesterolaemia heterozygotes had normal levels of LDL-C. To develop an animal model of this LDL-C lowering effect and to identify genes that modify the plasma LDL-C level, we crossed LDL receptor-deficient mice with other strains of mice.
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Affiliation(s)
- J Cohen
- Center for Human Nutrition, University of Texas, Southwestern Medical Center, Dallas 75235, USA
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16
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Rassow J, Pfanner N. Molecular chaperones and intracellular protein translocation. Rev Physiol Biochem Pharmacol 2006; 126:199-264. [PMID: 7886379 DOI: 10.1007/bfb0049777] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- J Rassow
- Biochemisches Institut, Universität Freiburg, Germany
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17
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Stojanovic M, Germain M, Nguyen M, Shore GC. BAP31 and Its Caspase Cleavage Product Regulate Cell Surface Expression of Tetraspanins and Integrin-mediated Cell Survival. J Biol Chem 2005; 280:30018-24. [PMID: 15946936 DOI: 10.1074/jbc.m501306200] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
BAP31, a resident integral protein of the endoplasmic reticulum membrane, regulates the export of other integral membrane proteins to the downstream secretory pathway. Here we show that cell surface expression of the tetraspanins CD9 and CD81 is compromised in mouse cells from which the Bap31 gene has been deleted. CD9 and CD81 facilitate the function of multiprotein complexes at the plasma membrane, including integrins. Of note, BAP31 does not appear to influence the egress of alpha5beta1 or alpha(v)beta3 integrins to the cell surface, but in Bap31-null mouse cells, these integrins are not able to maintain cellular adhesion to the extracellular matrix in the presence of reduced serum. Consequently, Bap31-null cells are sensitive to serum starvation-induced apoptosis. Reconstitution of wild-type BAP31 into these Bap31-null cells restores integrin-mediated cell attachment and cell survival after serum stress, whereas interference with the functions of CD9, alpha5beta1, or alpha(v)beta3 by antagonizing antibodies makes BAP31 cells act similar to Bap31-null cells in these respects. Finally, in human KB epithelial cells protected from apoptosis by BCL-2, the caspase-8 cleavage product, p20 BAP31, inhibits egress of tetraspanin and integrin-mediated cell attachment. Thus, p20 BAP31 can operate upstream of BCL-2 in living cells to influence cell surface properties due to its effects on protein egress from the endoplasmic reticulum.
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Affiliation(s)
- Marina Stojanovic
- Department of Biochemistry, McIntyre Medical Sciences Building, McGill University, Montreal, Quebec H3G 1Y6, Canada
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18
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Ritter C, Quirin K, Kowarik M, Helenius A. Minor folding defects trigger local modification of glycoproteins by the ER folding sensor GT. EMBO J 2005; 24:1730-8. [PMID: 15861139 PMCID: PMC1142578 DOI: 10.1038/sj.emboj.7600645] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2003] [Accepted: 03/10/2005] [Indexed: 01/16/2023] Open
Abstract
UDP-glucose:glycoprotein glucosyltransferase (GT) is a key component of the glycoprotein-specific folding and quality control system in the endoplasmic reticulum. By exclusively reglucosylating incompletely folded and assembled glycoproteins, it serves as a folding sensor that prolongs the association of newly synthesized glycoproteins with the chaperone-like lectins calnexin and calreticulin. Here, we address the mechanism by which GT recognizes and labels its substrates. Using an improved inhibitor assay based on soluble conformers of pancreatic ribonuclease in its glycosylated (RNase B) and unglycosylated (RNase A) forms, we found that the protein moiety of a misfolded conformer alone is sufficient for specific recognition by GT in vitro. To investigate the relationship between recognition and glucosylation, we tested a variety of glycosylation mutants of RNase S-Protein and an RNase mutant with a local folding defect [RNase C65S, C72S], as well as a series of loop insertion mutants. The results indicated that local folding defects in an otherwise correctly folded domain could be recognized by GT. Only glycans attached to the polypeptide within the misfolded sites were glucosylated.
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Affiliation(s)
- Christiane Ritter
- Institute of Biochemistry, Swiss Federal Institute of Technology, Zurich, Switzerland
| | - Katharina Quirin
- Institute of Biochemistry, Swiss Federal Institute of Technology, Zurich, Switzerland
| | - Michael Kowarik
- Institute of Biochemistry, Swiss Federal Institute of Technology, Zurich, Switzerland
| | - Ari Helenius
- Institute of Biochemistry, Swiss Federal Institute of Technology, Zurich, Switzerland
- Institute of Biochemistry, HPM E 6.3, ETH-Hoenggerberg, 8093 Zurich, Switzerland. Tel.: +41 1 632 6817; Fax: +41 1 632 1269; E-mail:
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19
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Komaru K, Ishida Y, Amaya Y, Goseki-Sone M, Orimo H, Oda K. Novel aggregate formation of a frame-shift mutant protein of tissue-nonspecific alkaline phosphatase is ascribed to three cysteine residues in the C-terminal extension. FEBS J 2005; 272:1704-17. [PMID: 15794757 DOI: 10.1111/j.1742-4658.2005.04597.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In the majority of hypophosphatasia patients, reductions in the serum levels of alkaline phosphatase activity are caused by various missense mutations in the tissue-nonspecific alkaline phosphatase (TNSALP) gene. A unique frame-shift mutation due to a deletion of T at cDNA number 1559 [TNSALP (1559delT)] has been reported only in Japanese patients with high allele frequency. In this study, we examined the molecular phenotype of TNSALP (1559delT) using in vitro translation/translocation system and COS-1 cells transiently expressing this mutant protein. We showed that the mutant protein not only has a larger molecular size than the wild type enzyme by approximately 12 kDa, reflecting an 80 amino acid-long extension at its C-terminus, but that it also lacks a glycosylphosphatidylinositol anchor. In support of this, alkaline phosphatase activity of the cells expressing TNSALP (1559delT) was localized at the juxtanucleus position, but not on the cell surface. However, only a limited amount of the newly synthesized protein was released into the medium and the rest was polyubiquitinated, followed by degradation in the proteasome. SDS/PAGE and analysis by sucrose-density-gradient analysis indicated that TNSALP (1559delT) forms a disulfide-bonded high-molecular-mass aggregate. Interestingly, the aggregate form of TNSALP (1559delT) exhibited a significant enzyme activity. When all three cysteines at positions of 506, 521 and 577 of TNSALP (1559delT) were replaced with serines, the aggregation disappeared and instead this modified mutant protein formed a noncovalently associated dimer, strongly indicating that these cysteine residues in the C-terminal region are solely responsible for aggregate formation by cross-linking the catalytically active dimers. Thus, complete absence of TNSALP on cell surfaces provides a plausible explanation for a severe lethal phenotype of a homozygote hypophosphatasia patient carrying TNSALP (1559delT).
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Affiliation(s)
- Keiichi Komaru
- Division of Biochemistry, Niigata University Graduate School of Medical and Dental Sciences, Gakkocho-dori, Niigata, Japan
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20
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Kittanakom S, Cordat E, Akkarapatumwong V, Yenchitsomanus PT, Reithmeier RAF. Trafficking defects of a novel autosomal recessive distal renal tubular acidosis mutant (S773P) of the human kidney anion exchanger (kAE1). J Biol Chem 2004; 279:40960-71. [PMID: 15252044 DOI: 10.1074/jbc.m405356200] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Autosomal dominant and recessive distal renal tubular acidosis (dRTA) can be caused by mutations in the anion exchanger 1 (AE1 or SLC4A1) gene, which encodes the erythroid chloride/bicarbonate anion exchanger membrane glycoprotein (eAE1) and a truncated kidney isoform (kAE1). The biosynthesis and trafficking of kAE1 containing a novel recessive missense dRTA mutation (kAE1 S773P) was studied in transiently transfected HEK-293 cells, expressing the mutant alone or in combination with wild-type kAE1 or another recessive mutant, kAE1 G701D. The kAE1 S773P mutant was expressed at a three times lower level than wild-type, had a 2-fold decrease in its half-life, and was targeted for degradation by the proteasome. It could not be detected at the plasma membrane in human embryonic kidney cells and showed predominant endoplasmic reticulum immunolocalization in both human embryonic kidney and LLC-PK1 cells. The oligosaccharide on a kAE1 S773P N-glycosylation mutant (N555) was not processed to the complex form indicating impaired exit from the endoplasmic reticulum. The kAE1 S773P mutant showed decreased binding to an inhibitor affinity resin and increased sensitivity to proteases, suggesting that it was not properly folded. The other recessive dRTA mutant, kAE1 G701D, also exhibited defective trafficking to the plasma membrane. The recessive kAE1 mutants formed dimers like wild-type AE1 and could hetero-oligomerize with wild-type kAE1 or with each other. Hetero-oligomers of wild-type kAE1 with recessive kAE1 S773P or G701D, in contrast to the dominant kAE1 R589H mutant, were delivered to the plasma membrane.
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MESH Headings
- Acidosis, Renal Tubular/metabolism
- Anion Exchange Protein 1, Erythrocyte/chemistry
- Anion Exchange Protein 1, Erythrocyte/genetics
- Anions
- Biological Transport
- Biotinylation
- Blotting, Western
- Cell Line
- Cell Membrane/metabolism
- Cell Separation
- DNA, Complementary/metabolism
- Electrophoresis, Polyacrylamide Gel
- Endoplasmic Reticulum/metabolism
- Flow Cytometry
- Genes, Dominant
- Heterozygote
- Homozygote
- Humans
- Microscopy, Fluorescence
- Models, Biological
- Mutation
- Oligosaccharides/chemistry
- Plasmids/metabolism
- Polymorphism, Single-Stranded Conformational
- Precipitin Tests
- Protein Binding
- Protein Folding
- Protein Structure, Tertiary
- Time Factors
- Transfection
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Affiliation(s)
- Saranya Kittanakom
- Canadian Institutes of Health Research Group in Membrane Biology, Departments of Biochemistry and Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada
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21
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Danpure CJ. How can the products of a single gene be localized to more than one intracellular compartment? Trends Cell Biol 2004; 5:230-8. [PMID: 14732127 DOI: 10.1016/s0962-8924(00)89016-9] [Citation(s) in RCA: 124] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Protein-targeting sequences are specific for each intracellular compartment, so that most proteins are found at only one location within the eukaryotic cell. Increasingly, however, examples are being found of proteins that occur and function in more than one cellular compartment. In some cases, the multicompartmentalized isoforms are encoded by the same gene. Several mechanisms have evolved to enable such genes to encode and differentially express multiple types of topogenic information. These mechanisms include alternative forms of transcription initiation, translation initiation, splicing and post-translational modification.
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Affiliation(s)
- C J Danpure
- MRC Protein Translocation Group at the Dept of Biology, University College London, Gower Street, London, WC1E 6BT, UK
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22
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Abstract
The biosynthesis of secretory and membrane proteins in the endoplasmic reticulum (ER) yields mostly properly folded and assembled structures with full biological activity. Such fidelity is maintained by quality control (QC) mechanisms that avoid the production of nonnative structures. QC relies on chaperone systems in the ER that monitor and assist in the folding process. When folding promotion is not sufficient, proteins are retained in the ER and eventually retranslocated to the cytosol for degradation by the ubiquitin proteasome pathway. Retention of proteins that fail QC can sometimes occur beyond the ER, and degradation can take place in lysosomes. Several diseases are associated with proteins that do not pass QC, fail to be degraded efficiently, and accumulate as aggregates. In other cases, pathology arises from the downregulation of mutated but potentially functional proteins that are retained and degraded by the QC system.
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Affiliation(s)
- E Sergio Trombetta
- Department of Cell Biology, Yale University School of Medicine, PO Box 208002, New Haven, Connecticut 06520-8002, USA.
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23
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Abstract
The endoplasmic reticulum (ER) has a quality-control system for 'proof-reading' newly synthesized proteins, so that only native conformers reach their final destinations. Non-native conformers and incompletely assembled oligomers are retained, and, if misfolded persistently, they are degraded. As a large fraction of ER-synthesized proteins fail to fold and mature properly, ER quality control is important for the fidelity of cellular functions. Here, we discuss recent progress in understanding the conformation-specific sorting of proteins at the level of ER retention and export.
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Affiliation(s)
- Lars Ellgaard
- Institute of Biochemistry, Swiss Federal Institute of Technology (ETH) Zürich, Hönggerberg, CH - 8093 Zürich, Switzerland
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24
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Linke M, Herzog V, Brix K. Trafficking of lysosomal cathepsin B-green fluorescent protein to the surface of thyroid epithelial cells involves the endosomal/lysosomal compartment. J Cell Sci 2002; 115:4877-89. [PMID: 12432075 DOI: 10.1242/jcs.00184] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cathepsin B, a lysosomal cysteine proteinase, is involved in limited proteolysis of thyroglobulin with thyroxine liberation at the apical surface of thyroid epithelial cells. To analyze the trafficking of lysosomal enzymes to extracellular locations of thyroid epithelial cells, we have expressed a chimeric protein consisting of rat cathepsin B and green fluorescent protein. Heterologous expression in CHO cells validated the integrity of the structural motifs of the chimeric protein for targeting to endocytic compartments. Homologous expression, colocalization and transport experiments with rat thyroid epithelial cell lines FRT or FRTL-5 demonstrated the correct sorting of the chimeric protein into the lumen of the endoplasmic reticulum, and its subsequent transport via the Golgi apparatus and the trans-Golgi network to endosomes and lysosomes. In addition, the chimeras were secreted as active enzymes from FRTL-5 cells in a thyroid-stimulating-hormone-dependent manner. Immunoprecipitation experiments after pulse-chase radiolabeling showed that secreted chimeras lacked the propeptide of cathepsin B. Thus, the results suggest that cathepsin B is first transported to endosomes/lysosomes from where its matured form is retrieved before being secreted, supporting the view that endosome/lysosome-derived cathepsin B contributes to the potential of extracellular proteolysis in the thyroid.
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Affiliation(s)
- Martin Linke
- Institut für Zellbiologie and Bonner Forum Biomedizin, Universität Bonn, Ulrich-Haberland-Str. 61a, D-53121 Bonn, Germany
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25
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Knorre A, Wagner M, Schaefer HE, Colledge WH, Pahl HL. DeltaF508-CFTR causes constitutive NF-kappaB activation through an ER-overload response in cystic fibrosis lungs. Biol Chem 2002; 383:271-82. [PMID: 11934265 DOI: 10.1515/bc.2002.029] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The clinical course of Cystic Fibrosis is characterized by recurrent pulmonary infections which ultimately lead to death by respiratory failure. The most common CF causing mutation, deltaF508-CFTR, produces an incorrectly folded protein, which accumulates within the endoplasmic reticulum. However, the molecular mechanism by which the deltaF508-CFTR protein facilitates pulmonary infection and inflammation remains unclear. Here we show that the expression of deltaF508-CFTR causes a constitutive activation of the pro-inflammatory transcription factor NF-kappaB by eliciting an ER stress reaction, the ER-overload response. This endogenous NF-kappaB activation stimulates the transcription of pro-inflammatory cytokines thereby commencing an inflammatory cascade within the CF lung.
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Affiliation(s)
- Alexander Knorre
- Department of Experimental Anaesthesiology, University Hospital Freiburg, Germany
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26
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Abstract
The endoplasmic reticulum (ER) is a subcellular compartment specialized in folding and assembly of newly synthesized polypeptides. The polypeptides expressed in the ER include all secretory proteins produced in the cell, lumenal or membrane-bound proteins of the endocytic/vacuolar and secretory compartments and transmembrane proteins that operate at the plasma membrane. In the lumen of the ER, molecular chaperones and folding factors facilitate the maturation of newly synthesized proteins. In a process defined as ER-quality control, they also warrant that only properly structured and assembled products leave the ER and are transported to their target organelles and compartments. If proper maturation fails, the aberrant products are degraded. Quality control in the ER is essential to prevent exit of improperly regulated or not-functional products that could lead to harmful effects. The mechanisms of protein folding and quality control in the ER are far from being fully understood. They are fundamental for the life of cells and organisms, but they are also linked to important human hereditary diseases in which mutated gene products are retained in the ER and degraded (e.g., cystic fibrosis and hereditary lung emphysema).
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27
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Derer P, Derer M, Goffinet A. Axonal secretion of Reelin by Cajal-Retzius cells: evidence from comparison of normal and Reln(Orl) mutant mice. J Comp Neurol 2001; 440:136-43. [PMID: 11745613 DOI: 10.1002/cne.1375] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
A novel secretory pathway has been identified in the study of mice homozygous for the Reln(Orl) mutation, a line characterised by the defective secretion of the large extracellular matrix glycoprotein Reelin. By using both light and electron microscopy, immunohistochemical studies for Reelin in these mutants identified morphological changes in their Cajal-Retzius cells (CR cells). The CR cells of the mutant displayed the characteristic features of bipolar, tangentially elongated neurons with a dendritic proximal pole and an axonal cone at the opposite end of the soma. At either pole, cisterns of prominent rough endoplasmic reticulum (RER) were found to be rich in Reelin. However, the Reelin-positive RER cisterns of the axonal cones were hugely dilated in homozygous Reln(Orl) mice as compared with their wild type counterparts. CR cell axons displayed beads throughout their length, each contained a smooth spheroidal cistern filled with Reelin-immunoreactive fibrillar material, and were increased in number and size in Reln(Orl) mice. RER phenotype was rescued in the Reln(Alb2) mice, a mutation in which no Reelin protein is produced. We propose that the RER dilations viewed in the Reln(Orl) mutation are due to the accumulation of the defective Reelin protein, and the large axonal beads in Reln(Orl) mice reflect the accumulation of truncated Reelin as the result of defects in its secretion. These observations point to an original, hitherto unrecognised, mechanism of secretion by bulk transport in smooth cisterns from the axonal cone into the axon, followed by secretion in the cortical marginal zone from the axonal cisterns that we have named axonal reelin reservoirs.
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MESH Headings
- Acetylcholine/metabolism
- Acetylcholinesterase/metabolism
- Animals
- Body Patterning/genetics
- Cell Adhesion Molecules, Neuronal/genetics
- Cell Adhesion Molecules, Neuronal/metabolism
- Cell Compartmentation/physiology
- Cell Differentiation/genetics
- Cell Size/genetics
- Cerebral Cortex/abnormalities
- Cerebral Cortex/metabolism
- Cerebral Cortex/ultrastructure
- Dendrites/metabolism
- Dendrites/ultrastructure
- Endoplasmic Reticulum, Rough/metabolism
- Endoplasmic Reticulum, Rough/pathology
- Endoplasmic Reticulum, Rough/ultrastructure
- Extracellular Matrix Proteins/genetics
- Extracellular Matrix Proteins/metabolism
- Fetus
- Growth Cones/metabolism
- Growth Cones/pathology
- Growth Cones/ultrastructure
- Immunohistochemistry
- Mice
- Mice, Inbred BALB C/embryology
- Mice, Inbred BALB C/metabolism
- Mice, Neurologic Mutants/abnormalities
- Mice, Neurologic Mutants/metabolism
- Microscopy, Electron
- Mutation/physiology
- Nerve Tissue Proteins
- Reelin Protein
- Serine Endopeptidases
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Affiliation(s)
- P Derer
- Laboratoire du Développement et Vieillissement du Système Nerveux (DVSN), FRE 2371 Neurobiologie des Processus Adaptatifs, CNRS et Université P. et M. Curie, Paris cedex 05, France.
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28
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Kuwahara M, Iwai K, Ooeda T, Igarashi T, Ogawa E, Katsushima Y, Shinbo I, Uchida S, Terada Y, Arthus MF, Lonergan M, Fujiwara TM, Bichet DG, Marumo F, Sasaki S. Three families with autosomal dominant nephrogenic diabetes insipidus caused by aquaporin-2 mutations in the C-terminus. Am J Hum Genet 2001; 69:738-48. [PMID: 11536078 PMCID: PMC1226060 DOI: 10.1086/323643] [Citation(s) in RCA: 118] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2001] [Accepted: 08/06/2001] [Indexed: 01/04/2023] Open
Abstract
The vasopressin-regulated water channel aquaporin-2 (AQP2) is known to tetramerize in the apical membrane of the renal tubular cells and contributes to urine concentration. We identified three novel mutations, each in a single allele of exon 4 of the AQP2 gene, in three families showing autosomal dominant nephrogenic diabetes insipidus (NDI). These mutations were found in the C-terminus of AQP2: a deletion of G at nucleotide 721 (721 delG), a deletion of 10 nucleotides starting at nucleotide 763 (763-772del), and a deletion of 7 nucleotides starting at nucleotide 812 (812-818del). The wild-type AQP2 is predicted to be a 271-amino acid protein, whereas these mutant genes are predicted to encode proteins that are 330-333 amino acids in length, because of the frameshift mutations. Interestingly, these three mutant AQP2s shared the same C-terminal tail of 61 amino acids. In Xenopus oocytes injected with mutant AQP2 cRNAs, the osmotic water permeability (Pf) was much smaller than that of oocytes with the AQP2 wild-type (14%-17%). Immunoblot analysis of the lysates of the oocytes expressing the mutant AQP2s detected a band at 34 kD, whereas the immunoblot of the plasma-membrane fractions of the oocytes and immunocytochemistry failed to show a significant surface expression, suggesting a defect in trafficking of these mutant proteins. Furthermore, coinjection of wild-type cRNAs with mutant cRNAs markedly decreased the oocyte Pf in parallel with the surface expression of the wild-type AQP2. Immunoprecipitation with antibodies against wild-type and mutant AQP2 indicated the formation of mixed oligomers composed of wild-type and mutant AQP2 monomers. Our results suggest that the trafficking of mutant AQP2 is impaired because of elongation of the C-terminal tail, and the dominant-negative effect is attributed to oligomerization of the wild-type and mutant AQP2s. Segregation of the mutations in the C-terminus of AQP2 with dominant-type NDI underlies the importance of this domain in the intracellular trafficking of AQP2.
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Affiliation(s)
- M Kuwahara
- Department of Homeostasis Medicine and Nephrology, Graduate School, Tokyo Medical and Dental University, Tokyo 113-8519, Japan.
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29
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Abstract
As a rule, only proteins that have reached a native, folded and assembled structure are transported to their target organelles and compartments within the cell. In the secretory pathway of eukaryotic cells, this type of sorting is particularly important. A variety of molecular mechanisms are involved that distinguish between folded and unfolded proteins, modulate their intracellular transport, and induce degradation if they fail to fold. This phenomenon, called quality control, occurs at several levels and involves different types of folding sensors. The quality control system provides a stringent and versatile molecular sorting system that guaranties fidelity of protein expression in the secretory pathway.
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Affiliation(s)
- A Helenius
- Swiss Federal Institute of Technology (ETH), Institute of Biochemistry, Universitätstrasse 16, CH-8092 Zurich, Switzerland.
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30
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Day JM, Murdoch AD, Hardingham TE. The folded protein modules of the C-terminal G3 domain of aggrecan can each facilitate the translocation and secretion of the extended chondroitin sulfate attachment sequence. J Biol Chem 1999; 274:38107-11. [PMID: 10608880 DOI: 10.1074/jbc.274.53.38107] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Aggrecan is a multidomain proteoglycan containing both extended and folded protein modules. The C-terminal G3 domain contains a lectin-like, complement regulatory protein-like, and two alternatively spliced epidermal growth factor-like modules. It has been proposed that the lectin module alone has a necessary role in the intracellular translocation and secretion of proteins expressed containing G3. Constructs containing human aggrecan G3 together with 1155 bases of the adjacent chondroitin sulfate attachment region (CS-2) were prepared with different combinations and deletions of the protein modules and transfected into mammalian cells of monkey or hamster origin. The results showed that the products containing only the unfolded protein sequences (CS-2 with or without the C-terminal tail sequence) were translated and accumulated intracellularly but were not secreted. In contrast the constructs containing any of the folded protein modules and the extended CS-2 region were translated and secreted from the cells. The results show that the lectin module was not unique in facilitating the intracellular translocation and secretion of the G3 domain. The conservation of G3-like domains within the aggrecan family of proteoglycans may therefore result from their participation in other extracellular functions.
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Affiliation(s)
- J M Day
- The Wellcome Trust Centre for Cell Matrix Research, School of Biological Sciences, University of Manchester, Manchester M13 9PT, United Kingdom
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31
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Abstract
A variety of quality control mechanisms operate in the endoplasmic reticulum and in downstream compartments of the secretory pathway to ensure the fidelity and regulation of protein expression during cell life and differentiation. As a rule, only proteins that pass a stringent selection process are transported to their target organelles and compartments. If proper maturation fails, the aberrant products are degraded. Quality control improves folding efficiency by retaining proteins in the special folding environment of the endoplasmic reticulum, and it prevents harmful effects that could be caused by the deployment of incompletely folded or assembled proteins.
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Affiliation(s)
- L Ellgaard
- Institute of Biochemistry, Swiss Federal Institute of Technology (ETH), Universitätstrasse 16, CH-8092 Zürich, Switzerland
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32
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Ayala I, Babià T, Baldassarre M, Pompeo A, Fabra A, Kok JW, Luini A, Buccione R, Egea G. Morphological and biochemical analysis of the secretory pathway in melanoma cells with distinct metastatic potential. FEBS Lett 1999; 451:315-20. [PMID: 10371212 DOI: 10.1016/s0014-5793(99)00620-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In this report, we have investigated whether alterations of the morphological and functional aspects of the biosecretory membrane system are associated with the metastatic potential of tumor cells. To this end, we have analyzed the morphology of the Golgi complex, the cytoskeleton organization and membrane trafficking steps of the secretory pathway in two human melanoma A375 cell line variants with low (A375-P) and high metastatic (A375-MM) potential. Immunofluorescence analysis showed that in A375-P cells, the Golgi complex showed a collapsed morphology. Conversely, in A375-MM cells, the Golgi complex presented a reticular and extended morphology. At the ultrastructural level, the Golgi complex of A375-P cells was fragmented and cisternae were swollen. When the cytoskeleton was analyzed, the microtubular network appeared normal in both cell variants, whereas actin stress fibers were largely absent in A375-P, but not in A375-MM cells. In addition, the F-actin content in A375-P cells was significantly lower than in A375-MM cells. These morphological differences in A375-P cells were accompanied by acceleration and an increase in the endoplasmic reticulum to Golgi and the trans-Golgi network to cell surface membrane transport, respectively. Our results indicate that in human A375 melanoma cells, metastatic potential correlates with a well-structured morphofunctional organization of the Golgi complex and actin cytoskeleton.
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Affiliation(s)
- I Ayala
- Dept. Biologica Cellular, Facultat de Medicina, Institut d'Investigacions Biomèdiques August Pi i Sunyer, Universität de Barcelona, Spain
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33
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Abstract
Transmissible spongiform encephalopathies form a group of fatal neurodegenerative disorders that have the unique property of being infectious, sporadic or genetic in origin. Although the nature of the responsible agent of these diseases is uncertain, it is clear that a protein called PrPSc has a central role in their pathology. PrPSc is a conformational variant of a normal protein called PrPC. Understanding the transition from PrPC to PrPSc is a major issue in the field. In this article, we will review what is known about the cell biology of PrPC, the understanding of which is crucial considering that trafficking of this molecule governs generation of PrPSc.
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34
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Aridor M, Bannykh SI, Rowe T, Balch WE. Cargo can modulate COPII vesicle formation from the endoplasmic reticulum. J Biol Chem 1999; 274:4389-99. [PMID: 9933643 DOI: 10.1074/jbc.274.7.4389] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The COPII coat complex found on endoplasmic reticulum (ER)-derived vesicles plays a critical role in cargo selection. We now address the potential role of biosynthetic cargo in modulating COPII coat assembly and vesicle budding. The ER accumulation of vesicular stomatitis glycoprotein (VSV-G), a transmembrane protein, or the soluble PiZ variant of alpha1-antitrypsin, reduced levels of general COPII vesicle formation in vivo. Consistent with this result, conditions that prevent the export of VSV-G from the ER led to a significant inhibition of general COPII vesicle budding from ER microsomes and the export of an endogenous recycling protein p58 in vitro. In contrast, synchronized export of VSV-G stimulated COPII vesicle budding both in vivo and in vitro. Under conditions where VSV-G is retained in the ER, we find that it can to be recovered in pre-budding complexes containing COPII components. These results suggest that the export of biosynthetic cargo is integrated with ER functions involved in protein folding and oligomerization. The ability of biosynthetic cargo to prevent or enhance ER export suggests that interactions of cargo with the COPII machinery contribute to the formation of vesicles budding from the ER.
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Affiliation(s)
- M Aridor
- Departments of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, California 92037, USA
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35
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Loayza D, Tam A, Schmidt WK, Michaelis S. Ste6p mutants defective in exit from the endoplasmic reticulum (ER) reveal aspects of an ER quality control pathway in Saccharomyces cerevisiae. Mol Biol Cell 1998; 9:2767-84. [PMID: 9763443 PMCID: PMC25553 DOI: 10.1091/mbc.9.10.2767] [Citation(s) in RCA: 96] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/1998] [Accepted: 07/24/1998] [Indexed: 11/11/2022] Open
Abstract
We are studying the intracellular trafficking of the multispanning membrane protein Ste6p, the a-factor transporter in Saccharomyces cerevisiae and a member of the ATP-binding cassette superfamily of proteins. In the present study, we have used Ste6p as model for studying the process of endoplasmic reticulum (ER) quality control, about which relatively little is known in yeast. We have identified three mutant forms of Ste6p that are aberrantly ER retained, as determined by immunofluorescence and subcellular fractionation. By pulse-chase metabolic labeling, we demonstrate that these mutants define two distinct classes. The single member of Class I, Ste6-166p, is highly unstable. We show that its degradation involves the ubiquitin-proteasome system, as indicated by its in vivo stabilization in certain ubiquitin-proteasome mutants or when cells are treated with the proteasome inhibitor drug MG132. The two Class II mutant proteins, Ste6-13p and Ste6-90p, are hyperstable relative to wild-type Ste6p and accumulate in the ER membrane. This represents the first report of a single protein in yeast for which distinct mutant forms can be channeled to different outcomes by the ER quality control system. We propose that these two classes of ER-retained Ste6p mutants may define distinct checkpoint steps in a linear pathway of ER quality control in yeast. In addition, a screen for high-copy suppressors of the mating defect of one of the ER-retained ste6 mutants has identified a proteasome subunit, Hrd2p/p97, previously implicated in the regulated degradation of wild-type hydroxymethylglutaryl-CoA reductase in the ER membrane.
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Affiliation(s)
- D Loayza
- Department of Cell Biology and Anatomy, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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36
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Galan JM, Cantegrit B, Garnier C, Namy O, Haguenauer-Tsapis R. 'ER degradation' of a mutant yeast plasma membrane protein by the ubiquitin-proteasome pathway. FASEB J 1998; 12:315-23. [PMID: 9506475 DOI: 10.1096/fasebj.12.3.315] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The yeast plasma membrane, uracil permease, undergoes ubiquitin-dependent endocytosis and subsequent degradation in the vacuole via a process that does not involve the proteasome. Cell-surface ubiquitination of this protein is mediated by the ubiquitin-protein ligase Npi1p/Rsp5p and involves Lys63-linked ubiquitin chains. This report describes the intracellular fate of a mutant form of uracil permease carrying a three amino acid insertion in a cytoplasmic loop. Most of this protein is not deployed beyond the ER, and is degraded by the 26S proteasome. Mutant permease degradation is almost unaffected in cells with impaired Npi1p/Rsp5p, but is dependent on the Ubc6p and Ubc7p ubiquitin-conjugating enzymes, suggesting that proteolysis of the protein requires its prior ubiquitination. Overproduction of a derivative of ubiquitin with a modified Lys48 strongly impairs mutant permease degradation. This suggests that, like other proteasome substrates, mutant permease might be polyubiquitinated with Lys48-linked ubiquitin chains. These findings provide an example of a yeast plasma membrane protein that is routed to the 'ER degradation' pathway, and highlight the versatility of the ubiquitin system.
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Affiliation(s)
- J M Galan
- Institut J. Monod, Université Paris VII-CNRS, France
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37
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Loayza D, Michaelis S. Role for the ubiquitin-proteasome system in the vacuolar degradation of Ste6p, the a-factor transporter in Saccharomyces cerevisiae. Mol Cell Biol 1998; 18:779-89. [PMID: 9447974 PMCID: PMC108789 DOI: 10.1128/mcb.18.2.779] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/1997] [Accepted: 10/29/1997] [Indexed: 02/05/2023] Open
Abstract
Ste6p, the a-factor transporter in Saccharomyces cerevisiae, is a multispanning membrane protein with 12 transmembrane spans and two cytosolic ATP binding domains. Ste6p belongs to the ATP binding cassette (ABC) superfamily and provides an excellent model for examining the intracellular trafficking of a complex polytopic membrane protein in yeast. Previous studies have shown that Ste6p undergoes constitutive endocytosis from the plasma membrane, followed by delivery to the vacuole, where it is degraded in a Pep4p-dependent manner, even though only a small portion of Ste6p is exposed to the vacuolar lumen where the Pep4p-dependent proteases reside. Ste6p is known to be ubiquitinated, a modification that may facilitate its endocytosis. In the present study, we further investigated the intracellular trafficking of Ste6p, focusing on the role of the ubiquitin-proteasome machinery in the metabolic degradation of Ste6p. We demonstrate by pulse-chase analysis that the degradation of Ste6p is impaired in mutants that exhibit defects in the activity of the proteasome (doa4 and pre1,2). Likewise, by immunofluorescence, we observe that Ste6p accumulates in the vacuole in the doa4 mutant, as it does in the vacuolar protease-deficient pep4 mutant. One model consistent with our results is that the degradation of Ste6p, the bulk of which is exposed to the cytosol, requires the activity of both the cytosolic proteasomal degradative machinery and the vacuolar lumenal proteases, acting in a synergistic fashion. Alternatively, we discuss a second model whereby the ubiquitin-proteasome system may indirectly influence the Pep4p-dependent vacuolar degradation of Ste6p. This study establishes that Ste6p is distinctive in that two independent degradative systems (the vacuolar Pep4p-dependent proteases and the cytosolic proteasome) are both involved, either directly or indirectly, in the metabolic degradation of a single substrate.
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Affiliation(s)
- D Loayza
- Department of Cell Biology and Anatomy, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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38
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Bonifacino JS, Weissman AM. Ubiquitin and the control of protein fate in the secretory and endocytic pathways. Annu Rev Cell Dev Biol 1998; 14:19-57. [PMID: 9891777 PMCID: PMC4781171 DOI: 10.1146/annurev.cellbio.14.1.19] [Citation(s) in RCA: 485] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The modification of proteins by chains of ubiquitin has long been known to mediate targeting of cytosolic and nuclear proteins for degradation by proteasomes. In this article, we discuss recent developments that reveal the involvement of ubiquitin in the degradation of proteins retained within the endoplasmic reticulum (ER) and in the internalization of plasma membrane proteins. Both luminal and transmembrane proteins retained in the ER are now known to be retrotranslocated into the cytosol in a process that involves ER chaperones and components of the protein import machinery. Once exposed to the cytosolic milieu, retro-translocated proteins are degraded by the proteasome, in most cases following polyubiquitination. There is growing evidence that both the ubiquitin-conjugating machinery and proteasomes may be associated with the cytosolic face of the ER membrane and that they could be functionally coupled to the process of retrotranslocation. The ubiquitination of plasma membrane proteins, on the other hand, mediates internalization of the proteins, which in most cases is followed by lysosomal/vacuolar degradation. There is, however, a well-documented case of a plasma membrane protein (the c-Met receptor) for which ubiquitination results in proteasomal degradation. These recent findings imply that ubiquitin plays more diverse roles in the regulation of the fate of cellular proteins than originally anticipated.
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Affiliation(s)
- J S Bonifacino
- Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-5430, USA.
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39
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Hauri H, Schweizer A. The
ER
–Golgi Membrane System: Compartmental Organization and Protein Traffic. Compr Physiol 1997. [DOI: 10.1002/cphy.cp140115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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40
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Fujiki Y. Molecular defects in genetic diseases of peroxisomes. BIOCHIMICA ET BIOPHYSICA ACTA 1997; 1361:235-50. [PMID: 9375798 DOI: 10.1016/s0925-4439(97)00051-3] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- Y Fujiki
- Department of Biology, Faculty of Science, Kyushu University, Fukuoka, Japan.
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41
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de Bergeyck V, Nakajima K, Lambert de Rouvroit C, Naerhuyzen B, Goffinet AM, Miyata T, Ogawa M, Mikoshiba K. A truncated Reelin protein is produced but not secreted in the 'Orleans' reeler mutation (Reln[rl-Orl]). BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 1997; 50:85-90. [PMID: 9406921 DOI: 10.1016/s0169-328x(97)00166-6] [Citation(s) in RCA: 106] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Reelin is the protein defective in reeler mutant mice [I. Bar, C. Lambert de Rouvroit, I. Royaux, D.B. Krizman, C. Dernoncourt, D. Ruelle, M.C. Beckers, A.M. Goffinet, A YAC contig containing the reeler locus with preliminary characterization of candidate gene fragments, Genomics 26 (1995) 543-549; G. D'Arcangelo, G.G. Miao, S.C. Chen, H.D. Soares, J.I. Morgan, T. Curran, A protein related to extracellular matrix proteins deleted in the mouse mutant reeler, Nature 374 (1995) 719-723; S. Hirotsune, T. Takahara, N. Sasaki, K. Hirose, A. Yoshiki, T. Ohashi, M. Kusakabe, Y. Murakami, M. Muramatsu, S. Watanabe, K. Nakao, M. Katsuki, Y. Hayashizaki, The reeler gene encodes a protein with an EGF-like motif expressed by pioneer neurons, Nature Genet. 10 (1995) 77-83]. In the Orleans allele of reeler (symbol: Reln[rl-Orl]), a 220 nucleotide deletion is present in the 3' region of the Reelin message, resulting in a frame shift with production of a predicted protein amputated from its C-terminal amino acids. In this study, we first show that the predicted truncated protein indeed exists in Orleans reeler mice, using several anti-Reelin antibodies. Three antibodies are directed against epitopes located in the N-terminal region of the protein, namely: monoclonal antibody CR-50 [M. Ogawa, T. Miyata, K. Nakajima, K. Yagyu, M. Seike, K. Ikenaka, H. Yamamoto, K. Mikoshiba, The reeler gene-associated antigen on Cajal-Retzius neurons is a crucial molecule for laminar organization of cortical neurons, Neuron 14 (1995) 899-912] (epitope region between Reelin residues 251-407), monoclonal antibody G10 (epitope located between amino acids 199 and 244) and the polyclonal antipeptide rp4 (positions 381-399). A fourth antibody, antipeptide rp5, reacts with the C-terminal (3443-3461) Reelin sequence. In normal embryos, all four antibodies stained cells in the marginal zone with features of Cajal-Retzius cells. While N-terminal specific antibodies detected Reelin immunoreactivity in mouse embryos homozygous for the reeler-Orleans mutation, no staining was obtained with the rp5 antibody, showing the presence of a truncated protein. Moreover, although Reelin could be detected at the surface of living Cajal-Retzius cells of normal mice, it was not revealed after vital staining of embryonic cortex from Orleans reeler mice. These results indicate that the C-terminal region of Reelin is essential for its secretion and suggest that the Orleans reeler phenotype is due to defective Reelin secretion rather than to secretion of an inactive protein.
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Affiliation(s)
- V de Bergeyck
- Department of Physiology, FUNDP Medical School, Namur, Belgium.
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42
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Brown CR, Hong-Brown LQ, Welch WJ. Strategies for correcting the delta F508 CFTR protein-folding defect. J Bioenerg Biomembr 1997; 29:491-502. [PMID: 9511934 DOI: 10.1023/a:1022491124939] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Many human diseases arise as a result of mutations within genes encoding essential proteins. In many cases, the mutations are not so severe as to render the protein biologically inactive. Rather, the mutations oftentimes result in only subtle protein-folding abnormalities. In the case of the CFTR protein, a mutation leading to the loss of a single amino acid is responsible for the diseased state in the majority of individuals with cystic fibrosis. Here the newly synthesized mutant CFTR protein, missing a phenylalanine residue at position 508 (delta F508 CFTR), is unable to transit from the endoplasmic reticulum to the plasma membrane, where it functions as a regulator of chloride transport. All of the available evidence indicate that the newly synthesized delta F508 CFTR protein adopts a slightly altered conformation and therefore is retained at the level of the endoplasmic reticulum, ostensibly by the actions of the cellular quality control system. Because the mutant protein is capable of functioning as a chloride channel, developing ways to elicit its release out of the ER and to the plasma membrane has important clinical implications. Herein, we discuss our recent studies showing that the protein-folding defect associated with the delta F508 CFTR mutation, as well as a number of other temperature-sensitive mutations, can be overcome by strategies designed to influence protein folding inside the cell. Specifically we show that a number of low-molecular-weight compounds, all of which are known to stabilize proteins in their native conformation, are effective in rescuing the folding and/or processing defects associated with different mutations that oftentimes lead to human disease.
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Affiliation(s)
- C R Brown
- Department of Medicine, The University of California, San Francisco 94143, USA
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43
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Halaban R, Cheng E, Zhang Y, Moellmann G, Hanlon D, Michalak M, Setaluri V, Hebert DN. Aberrant retention of tyrosinase in the endoplasmic reticulum mediates accelerated degradation of the enzyme and contributes to the dedifferentiated phenotype of amelanotic melanoma cells. Proc Natl Acad Sci U S A 1997; 94:6210-5. [PMID: 9177196 PMCID: PMC21028 DOI: 10.1073/pnas.94.12.6210] [Citation(s) in RCA: 197] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The loss of tyrosinase, the key enzyme in melanin synthesis, has been implicated in the dedifferentiation of malignant melanocytes. The presence of tyrosinase transcripts and antigenic peptides in melanoma tumors prompted us to investigate whether the basis for the loss of the enzyme was proteolytic degradation. Toward this aim, we followed the kinetics of synthesis, degradation, processing, chaperone binding, inhibitor sensitivity, and subcellular localization of tyrosinase in normal and malignant melanocytes. We found that, in amelanotic melanoma cell lines, tyrosinase failed to reach the melanosome, the organelle for melanin synthesis, because it was retained in the endoplasmic reticulum (ER) and then degraded. Tyrosinase appeared mostly as a 70-kDa core-glycosylated, endoglycosidase H-sensitive, immature form bound to the ER chaperone calnexin and had a life-span of only 25% of normal. Maturation and transit from the ER to the Golgi compartment was facilitated by lowering the temperature of incubation to 31 degrees C. Several proteasome inhibitors caused the accumulation of an approximately 60-kDa tyrosinase doublet that was more prominent in malignant than in normal melanocytes and promoted, to various degrees, the maturation of tyrosinase in melanoma cells and the translocation of the enzyme to melanosomes. The appearance of ubiquitinated tyrosinase after treatment of normal melanocytes with N-acetyl-L-leucinyl-L-leucinal-L-norleucinal reinforced our notion that some tyrosinase is normally degraded by proteasomes. Proteolysis of tyrosinase by proteasomes is consistent with the production of antigenic tyrosinase peptides that are presented to the immune system by major histocompatibility complex class I molecules.
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Affiliation(s)
- R Halaban
- Department of Dermatology, Yale University School of Medicine, New Haven, CT 06520, USA.
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44
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Abstract
A nonconservative leucine to proline mutation in peripheral myelin protein 22 (PMP22) causes the Trembler-J (TrJ) neuropathy in mice and humans. The expression levels and localization of the PMP22 protein in the TrJ mouse have not been previously determined. The aim of our studies was to reevaluate the extent of myelin deficit in genotyped heterozygous and homozygous animals and to examine how the TrJ mutation alters the normal in vivo post-translational processing of PMP22. Morphological studies show evidence for primary dysmyelination and myelin instability in affected animals. As expected, Western blot analysis indicates that in adult heterozygous TrJ animals, the level of PMP22 is markedly decreased, similar to myelin basic protein and protein zero, whereas myelin-associated glycoprotein is largely unaffected. The decrease in myelin protein expression is associated with an increase in lysosomal biogenesis, suggestive of augmented endocytosis or autophagy. Double-immunolabeling experiments show the accumulation of PMP22 in endosomal/lysosomal structures of TrJ Schwann cells, and chloroquine treatment of nerve segments indicates that the degradation of protein zero, PMP22, and myelin basic protein is augmented in TrJ nerves. These studies suggest that the TrJ mutation alters myelin stability and that the mutant protein is likely degraded via the lysosomal pathway.
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45
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Choudhury P, Liu Y, Bick RJ, Sifers RN. Intracellular association between UDP-glucose:glycoprotein glucosyltransferase and an incompletely folded variant of alpha1-antitrypsin. J Biol Chem 1997; 272:13446-51. [PMID: 9148970 DOI: 10.1074/jbc.272.20.13446] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Genetic variants of human alpha1-antitrypsin unable to fold into the native structural conformation are poorly secreted from hepatocytes. The molecular chaperone calnexin coimmunoprecipitates with secretion-incompetent variant null(Hong Kong) retained in stably transfected mouse hepatoma cells (Le, A., Steiner, J. L., Ferrell, G. A., Shaker, J. F., and Sifers, R. N. (1994) J. Biol. Chem. 269, 7514-7519). Mobilization of intracellular Ca2+ stores with metabolic poisons diminished interaction with calnexin and coincided with coimmuoprecipitation of a 150-kDa protein (p150). Mobilization of endoplasmic reticulum lumenal Ca2+ with thapsigargin, an inhibitor of the microsomal Ca2+ATPase, gave a similar result. Coimmunoprecipitation of p150 was specifically disrupted in response to incubation of the cell lysate with exogenous CaCl2. Finally, in ECL Western blotting, p150 was recognized by polyclonal antiserum against UDP-glucose:glycoprotein glucosyltransferase that likely functions in glycoprotein folding and quality control (Sousa, M. C., Ferrero-Garcia, M. A., and Parodi, A. J. (1992) Biochemistry 31, 97-105). The data are consistent with a model in which perturbation of endoplasmic reticulum Ca2+ results in a stable physical association between unfolded human alpha1-antitrypsin and UDP-glucose:glycoprotein glucosyltransferase.
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Affiliation(s)
- P Choudhury
- Departments of Pathology and Cell Biology, Baylor College of Medicine, University of Texas, Houston, Texas 77030, USA
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46
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Daude N, Lehmann S, Harris DA. Identification of intermediate steps in the conversion of a mutant prion protein to a scrapie-like form in cultured cells. J Biol Chem 1997; 272:11604-12. [PMID: 9111077 DOI: 10.1074/jbc.272.17.11604] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The central causative event in infectious, familial, and sporadic forms of prion disease is thought to be a conformational change that converts the cellular isoform of the prion protein (PrPC) into the scrapie isoform (PrPSc) that is the primary constituent of infectious prion particles. To provide a model system for analyzing the mechanistic details of this critical transformation, we have previously prepared cultured Chinese hamster ovary cells that stably express mouse PrP molecules carrying mutations homologous to those seen in familial prion diseases of humans. In the present work, we have analyzed the kinetics with which a PrP molecule containing an insertional mutation associated with Creutzfeldt-Jakob disease acquires several biochemical properties characteristic of PrPSc. Within 10 min of pulse labeling, the mutant protein undergoes a molecular alteration that is detectable by a change in Triton X-114 phase partitioning and phenyl-Sepharose binding. After 30 min of labeling, a detergent-insoluble and protease-sensitive form of the protein appears. After a chase period of several hours, the protein becomes protease-resistant. Incubation of cells at 18 degrees C or treatment with brefeldin A inhibits acquisition of detergent insolubility and protease resistance but does not affect Triton X-114 partitioning and phenyl-Sepharose binding. Our results support a model in which conversion of mutant PrPs to a PrPSc-like state proceeds in a stepwise fashion via a series of identifiable biochemical intermediates, with the earliest step occurring during or very soon after synthesis of the polypeptide in the endoplasmic reticulum.
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Affiliation(s)
- N Daude
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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47
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Motley AM, Hettema EH, Hogenhout EM, Brites P, ten Asbroek AL, Wijburg FA, Baas F, Heijmans HS, Tabak HF, Wanders RJ, Distel B. Rhizomelic chondrodysplasia punctata is a peroxisomal protein targeting disease caused by a non-functional PTS2 receptor. Nat Genet 1997; 15:377-80. [PMID: 9090382 DOI: 10.1038/ng0497-377] [Citation(s) in RCA: 215] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Rhizomelic chondrodysplasia punctata (RCDP) is an autosomal recessive disease characterized clinically by a disproportionately short stature primarily affecting the proximal parts of the extremities, typical dysmorphic facial appearance, congenital contractures and severe growth and mental retardation. Although some patients have single enzyme deficiencies, the majority of RCDP patients (86%) belong to a single complementation group (CG11, also known as complementation group I, Amsterdam nomenclature). Cells from CG11 show a tetrad of biochemical abnormalities: a deficiency of i) dihydroxyacetonephosphate acyltransferase, ii) alkyldihydroxyacetonephosphate synthase, iii) phytanic acid alpha-oxidation and iv) inability to import peroxisomal thiolase. These deficiencies indicate involvement of a component required for correct targeting of these peroxisomal proteins. Deficiencies in peroxisomal targeting are also found in Saccharomyces cerevisiae pex5 and pex7 mutants, which show differential protein import deficiencies corresponding to two peroxisomal targeting sequences (PTS1 and PTS2). These mutants lack their PTS1 and PTS2 receptors, respectively. Like S. cerevisiae pex cells, RCDP cells from CG11 cannot import a PTS2 reporter protein. Here we report the cloning of PEX7 encoding the human PTS2 receptor, based on its similarity to two yeast orthologues. All RCDP patients from CG11 with detectable PEX7 mRNA were found to contain mutations in PEX7. A mutation resulting in C-terminal truncation of PEX7 cosegregates with the disease and expression of PEX7 in RCDP fibroblasts from CG11 rescues the PTS2 protein import deficiency. These findings prove that mutations in PEX7 cause RCDP, CG11.
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Affiliation(s)
- A M Motley
- Department of Biochemistry, University of Amsterdam, The Netherlands
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48
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Arvan P, Kim PS, Kuliawat R, Prabakaran D, Muresan Z, Yoo SE, Abu Hossain S. Intracellular protein transport to the thyrocyte plasma membrane: potential implications for thyroid physiology. Thyroid 1997; 7:89-105. [PMID: 9086577 DOI: 10.1089/thy.1997.7.89] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
We present a snapshot of developments in epithelial biology that may prove helpful in understanding cellular aspects of the machinery designed for the synthesis of thyroid hormones on the thyroglobulin precursor. The functional unit of the thyroid gland is the follicle, delimited by a monolayer of thyrocytes. Like the cells of most simple epithelia, thyrocytes exhibit specialization of the cell surface that confronts two different extracellular environments-apical and basolateral, which are separated by tight junctions. Specifically, the basolateral domain faces the interstitium/bloodstream, while the apical domain is in contact with the lumen that is the primary target for newly synthesized thyroglobulin secretion and also serves as a storage depot for previously secreted protein. Thyrocytes use their polarity in several important ways, such as for maintaining basolaterally located iodide uptake and T4 deiodination, as well apically located iodide efflux and iodination machinery. The mechanisms by which this organization is established, fall in large part under the more general cell biological problem of intracellular sorting and trafficking of different proteins en route to the cell surface. Nearly all exportable proteins begin their biological life after synthesis in an intracellular compartment known as the endoplasmic reticulum (ER), upon which different degrees of difficulty may be encountered during nascent polypeptide folding and initial export to the Golgi complex. In these initial stages, ER molecular chaperones can assist in monitoring protein folding and export while themselves remaining as resident proteins of the thyroid ER. After export from the ER, most subsequent sorting for protein delivery to apical or basolateral surfaces of thyrocytes occurs within another specialized intracellular compartment known as the trans-Golgi network. Targeting information encoded in secretory proteins and plasma membrane proteins can be exposed or buried at different stages along the export pathway, which is likely to account for sorting and specific delivery of different newly-synthesized proteins. Defects in either burying or exposing these structural signals, and consequent abnormalities in protein transport, may contribute to different thyroid pathologies.
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Affiliation(s)
- P Arvan
- Division of Endocrinology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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49
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Abstract
Our level of understanding of peroxisome biogenesis in comparison with other cellular organelles is rudimentary, yet the fragments of information available indicate that the targeting and import of peroxisomal proteins occur by fundamentally different mechanisms. Genetic studies have identified a number of genes required for peroxisome assembly, but in most cases the functions of the gene products remain unknown. In vitro protein translocation systems have played a prominent role in unravelling the biochemistry of protein translocation into other organelles. This review considers some of the requirements for establishing a bona fide peroxisomal import assay and discusses the findings which have emerged as a result of using such experimental systems.
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Affiliation(s)
- A Baker
- Centre for Plant Biochemistry and Biotechnology, University of Leeds, United Kingdom.
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50
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Olias G, Richter D, Schmale H. Heterologous expression of human vasopressin-neurophysin precursors in a pituitary cell line: defective transport of a mutant protein from patients with familial diabetes insipidus. DNA Cell Biol 1996; 15:929-35. [PMID: 8945633 DOI: 10.1089/dna.1996.15.929] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Familial hypothalamic diabetes insipidus is an autosomal dominant disorder characterized by deficient vasopressin synthesis. Different point mutations in the vasopressin-neurophysin (VP-NP) precursor gene have been found in affected families. In a Dutch kindred, a single G to T transversion in the NP-encoding exon B of one allele converts the highly conserved glycine 17 to a valine residue. In order to examine whether this point mutation affects the processing and transport of the VP-NP precursor, the normal (HV2) and mutant (MT6) vasopressin cDNAs were stably expressed in the mouse pituitary cell line AtT20. The normal precursor was correctly glycosylated and processed, and NP was detected in the culture medium. Secretion of NP was stimulated by 8-bromo-cAMP, indicating that the normal precursor was targeted to the regulated secretory pathway. In contrast, the mutant precursor was synthesized, but processing and secretion were dramatically reduced. The mutant precursor was core-glycosylated but remained endoglycosidase H-sensitive, suggesting that the protein did not reach the trans-Golgi network. These results were supported by immunocytochemical studies. In HV2 cells, NP derived from the precursor was concentrated in the tips of the cell processes where secretory granules accumulate. In MT6 cells, NP staining was restricted to the endoplasmic reticulum (ER) as determined by colocalization with an ER-resident protein, BiP. These results suggest that the mutation within the conserved part of NP alters the conformation of the precursor and thus triggers its retention in the ER.
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Affiliation(s)
- G Olias
- Institut für Zellbiochemie und klinische Neurobiologie, Universitätskrankenhaus Eppendorf, Hamburg, Germany
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