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Burns GD, Hilal OE, Sun Z, Reutter KR, Preston GM, Augustine AA, Brodsky JL, Guerriero CJ. Distinct classes of misfolded proteins differentially affect the growth of yeast compromised for proteasome function. FEBS Lett 2021; 595:2383-2394. [PMID: 34358326 DOI: 10.1002/1873-3468.14172] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Revised: 07/24/2021] [Accepted: 07/29/2021] [Indexed: 11/09/2022]
Abstract
Maintenance of the proteome (proteostasis) is essential for cellular homeostasis and prevents cytotoxic stress responses that arise from protein misfolding. However, little is known about how different types of misfolded proteins impact homeostasis, especially when protein degradation pathways are compromised. We examined the effects of misfolded protein expression on yeast growth by characterizing a suite of substrates possessing the same aggregation-prone domain but engaging different quality control pathways. We discovered that treatment with a proteasome inhibitor was more toxic in yeast expressing misfolded membrane proteins, and this growth defect was mirrored in yeast lacking a proteasome-specific transcription factor, Rpn4p. These results highlight weaknesses in the proteostasis network's ability to handle the stress arising from an accumulation of misfolded membrane proteins.
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Affiliation(s)
- Grace D Burns
- Department of Biological Sciences, University of Pittsburgh, PA, USA
| | - Olivia E Hilal
- Department of Biological Sciences, University of Pittsburgh, PA, USA
| | - Zhihao Sun
- Department of Biological Sciences, University of Pittsburgh, PA, USA
| | | | - G Michael Preston
- Department of Biological Sciences, University of Pittsburgh, PA, USA
| | | | - Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh, PA, USA
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2
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DYT-TOR1A subcellular proteomics reveals selective vulnerability of the nuclear proteome to cell stress. Neurobiol Dis 2021; 158:105464. [PMID: 34358617 DOI: 10.1016/j.nbd.2021.105464] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 07/07/2021] [Accepted: 08/02/2021] [Indexed: 11/23/2022] Open
Abstract
TorsinA is a AAA+ ATPase that shuttles between the ER lumen and outer nuclear envelope in an ATP-dependent manner and is functionally implicated in nucleocytoplasmic transport. We hypothesized that the DYT-TOR1A dystonia disease-causing variant, ΔE TorsinA, may therefore disrupt the normal subcellular distribution of proteins between the nuclear and cytosolic compartments. To test this hypothesis, we performed proteomic analysis on nuclear and cytosolic subcellular fractions from DYT-TOR1A and wildtype mouse embryonic fibroblasts (MEFs). We further examined the compartmental proteomes following exposure to thapsigargin (Tg), an endoplasmic reticulum (ER) stressor, because DYT-TOR1A dystonia models have previously shown abnormalities in cellular stress responses. Across both subcellular compartments, proteomes of DYT-TOR1A cells showed basal state disruptions consistent with an activated stress response, and in response to thapsigargin, a blunted stress response. However, the DYT-TOR1A nuclear proteome under Tg cell stress showed the most pronounced and disproportionate degree of protein disruptions - 3-fold greater than all other conditions. The affected proteins extended beyond those typically associated with stress responses, including enrichments for processes critical for neuronal synaptic function. These findings highlight the advantage of subcellular proteomics to reveal events that localize to discrete subcellular compartments and refine thinking about the mechanisms and significance of cell stress in DYT-TOR1A pathogenesis.
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3
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Honer J, Niemeyer KM, Fercher C, Diez Tissera AL, Jaberolansar N, Jafrani YMA, Zhou C, Caramelo JJ, Shewan AM, Schulz BL, Brodsky JL, Zacchi LF. TorsinA folding and N-linked glycosylation are sensitive to redox homeostasis. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2021; 1868:119073. [PMID: 34062155 PMCID: PMC8889903 DOI: 10.1016/j.bbamcr.2021.119073] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Revised: 05/18/2021] [Accepted: 05/26/2021] [Indexed: 01/03/2023]
Abstract
The Endoplasmic Reticulum (ER) is responsible for the folding and post-translational modification of secretory proteins, as well as for triaging misfolded proteins. During folding, there is a complex yet only partially understood interplay between disulfide bond formation, which is an enzyme catalyzed event in the oxidizing environment of the ER, along with other post-translational modifications (PTMs) and chaperone-supported protein folding. Here, we used the glycoprotein torsinA as a model substrate to explore the impact of ER redox homeostasis on PTMs and protein biogenesis. TorsinA is a AAA+ ATPase with unusual oligomeric properties and controversial functions. The deletion of a C-terminal glutamic acid residue (∆E) is associated with the development of Early-Onset Torsion Dystonia, a severe movement disorder. TorsinA differs from other AAA+ ATPases since it is an ER resident, and as a result of its entry into the ER torsinA contains two N-linked glycans and at least one disulfide bond. The role of these PTMs on torsinA biogenesis and function and the identity of the enzymes that catalyze them are poorly defined. Using a yeast torsinA expression system, we demonstrate that a specific protein disulfide isomerase, Pdi1, affects the folding and N-linked glycosylation of torsinA and torsinA∆E in a redox-dependent manner, suggesting that the acquisition of early torsinA folding intermediates is sensitive to perturbed interactions between Cys residues and the quality control machinery. We also highlight the role of specific Cys residues during torsinA biogenesis and demonstrate that torsinA∆E is more sensitive than torsinA when these Cys residues are mutated.
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Affiliation(s)
- Jonas Honer
- Department of Biological Sciences, A320 Langley Hall, University of Pittsburgh, Pittsburgh, PA 15260, United States of America
| | - Katie M Niemeyer
- Department of Biological Sciences, A320 Langley Hall, University of Pittsburgh, Pittsburgh, PA 15260, United States of America
| | - Christian Fercher
- Australian Research Council Training Centre for Biopharmaceutical Innovation, Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, St. Lucia, QLD 4072, Australia
| | - Ana L Diez Tissera
- Fundación Instituto Leloir and Instituto de Investigaciones Bioquímicas de Buenos Aires (IIBBA-CONICET), 1405 Buenos Aires, Argentina
| | - Noushin Jaberolansar
- Australian Research Council Training Centre for Biopharmaceutical Innovation, Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, St. Lucia, QLD 4072, Australia
| | - Yohaann M A Jafrani
- Australian Research Council Training Centre for Biopharmaceutical Innovation, Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, St. Lucia, QLD 4072, Australia
| | - Chun Zhou
- School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, Queensland, 4072, Australia
| | - Julio J Caramelo
- Fundación Instituto Leloir and Instituto de Investigaciones Bioquímicas de Buenos Aires (IIBBA-CONICET), 1405 Buenos Aires, Argentina
| | - Annette M Shewan
- School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, Queensland, 4072, Australia
| | - Benjamin L Schulz
- Australian Research Council Training Centre for Biopharmaceutical Innovation, Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, St. Lucia, QLD 4072, Australia; School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, Queensland, 4072, Australia
| | - Jeffrey L Brodsky
- Department of Biological Sciences, A320 Langley Hall, University of Pittsburgh, Pittsburgh, PA 15260, United States of America
| | - Lucía F Zacchi
- Department of Biological Sciences, A320 Langley Hall, University of Pittsburgh, Pittsburgh, PA 15260, United States of America; Australian Research Council Training Centre for Biopharmaceutical Innovation, Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, St. Lucia, QLD 4072, Australia; Fundación Instituto Leloir and Instituto de Investigaciones Bioquímicas de Buenos Aires (IIBBA-CONICET), 1405 Buenos Aires, Argentina; School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, Queensland, 4072, Australia.
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4
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Cao X, An J, Cao Y, Lv J, Wang J, Ding Y, Lin X, Zhou X. EMC3 Is Essential for Retinal Organization and Neurogenesis During Mouse Retinal Development. Invest Ophthalmol Vis Sci 2021; 62:31. [PMID: 33605987 PMCID: PMC7900856 DOI: 10.1167/iovs.62.2.31] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Accepted: 01/18/2021] [Indexed: 12/15/2022] Open
Abstract
Purpose We used a mouse model to explore the role of the endoplasmic reticulum membrane protein complex subunit 3 (EMC3) in mammalian retinal development. Methods The transcription pattern of Emc3 in C57BL/6 mice was analyzed by in situ hybridization. To explore the effects of EMC3 absence on retinal development, the Cre-loxP system was used to generate retina-specific Emc3 in knockout mice (Emc3flox/flox, Six3-cre+; CKO). Morphological changes in the retina of E13.5, E17.5, P0.5, and P7 mice were observed via hematoxylin and eosin staining. Immunofluorescence staining was used to assess protein distribution and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining to assess apoptosis changes. Proteins were identified and quantified by Western blotting and proteomic analysis. Electroretinogram (ERG), fundus color photography, and optical coherence tomography were performed on 5-week-old mice to evaluate retinal function and structure. Results The Emc3 mRNA was widely distributed in the whole retina during development. Loss of retinal EMC3 led to retinal rosette degeneration with mislocalization of cell junction molecules (β-catenin, N-cadherin, and zonula occludens-1) and polarity molecules (Par3 and PKCζ). Endoplasmic reticulum stress and TUNEL apoptosis signals were present in retinal rosette-forming cells. Although the absence of EMC3 promoted the production of photoreceptor cells, 5-week-old mice lost all visual function and had severe retinal morphological degeneration. Conclusions EMC3 regulates retinal structure by maintaining the polarity of retinal progenitor cells and regulating retinal cell apoptosis.
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Affiliation(s)
- Xiaowen Cao
- School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
- State Key Laboratory of Optometry, Ophthalmology and Vision Science, Wenzhou, Zhejiang, China
| | - Jianhong An
- School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
- State Key Laboratory of Optometry, Ophthalmology and Vision Science, Wenzhou, Zhejiang, China
| | - Yuqing Cao
- School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
- State Key Laboratory of Optometry, Ophthalmology and Vision Science, Wenzhou, Zhejiang, China
| | - Juan Lv
- School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
- State Key Laboratory of Optometry, Ophthalmology and Vision Science, Wenzhou, Zhejiang, China
| | - Jiawei Wang
- School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
- State Key Laboratory of Optometry, Ophthalmology and Vision Science, Wenzhou, Zhejiang, China
| | - Yang Ding
- School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
- State Key Laboratory of Optometry, Ophthalmology and Vision Science, Wenzhou, Zhejiang, China
| | - Xinhua Lin
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Xiangtian Zhou
- School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
- State Key Laboratory of Optometry, Ophthalmology and Vision Science, Wenzhou, Zhejiang, China
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5
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Fercher C, Zacchi LF. Resolving the TorsinA Oligomerization Conundrum: The Glycan Hypothesis. Front Mol Biosci 2020; 7:585643. [PMID: 33134321 PMCID: PMC7567157 DOI: 10.3389/fmolb.2020.585643] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Accepted: 09/14/2020] [Indexed: 11/13/2022] Open
Abstract
TorsinA is a AAA+ ATPase involved in the severe neurological disease Early Onset Torsion Dystonia. Despite the impressive progress in the field in the recent years, the structural organization and function of this intriguing molecule is still not clear. One outstanding difference between torsinA and other AAA+ ATPases is that torsinA is a glycoprotein. TorsinA N-linked glycans impact torsinA biogenesis and subcellular localization. Here, we propose that torsinA glycans also modulate torsinA oligomerization properties. We used structural modeling to test this idea, and show that N-linked glycans appear to restrict torsinA's ability to form closed homohexameric ring assemblies, and instead promote an open hexameric conformation that allows torsinA interaction with key cofactors required for ATP hydrolysis. This mechanism would make torsinA a prime example of Nature's sophisticated molecular glycoengineering.
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Affiliation(s)
- Christian Fercher
- Australian Research Council (ARC), Training Centre for Biopharmaceutical Innovation, The University of Queensland, St Lucia, QLD, Australia
| | - Lucía F Zacchi
- Australian Research Council (ARC), Training Centre for Biopharmaceutical Innovation, The University of Queensland, St Lucia, QLD, Australia
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6
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Phung TK, Zacchi LF, Schulz BL. DIALib: an automated ion library generator for data independent acquisition mass spectrometry analysis of peptides and glycopeptides. Mol Omics 2020; 16:100-112. [DOI: 10.1039/c9mo00125e] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Data Independent Acquisition (DIA) Mass Spectrometry (MS) workflows allow unbiased measurement of all detectable peptides from complex proteomes, but require ion libraries for interrogation of peptides of interest.
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Affiliation(s)
- Toan K. Phung
- School of Chemistry and Molecular Biosciences
- The University of Queensland
- St Lucia
- Australia
| | - Lucia F. Zacchi
- ARC Training Centre for Biopharmaceutical Innovation
- The University of Queensland
- St. Lucia
- Australia
| | - Benjamin L. Schulz
- School of Chemistry and Molecular Biosciences
- The University of Queensland
- St Lucia
- Australia
- ARC Training Centre for Biopharmaceutical Innovation
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Needham PG, Guerriero CJ, Brodsky JL. Chaperoning Endoplasmic Reticulum-Associated Degradation (ERAD) and Protein Conformational Diseases. Cold Spring Harb Perspect Biol 2019; 11:cshperspect.a033928. [PMID: 30670468 DOI: 10.1101/cshperspect.a033928] [Citation(s) in RCA: 84] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Misfolded proteins compromise cellular homeostasis. This is especially problematic in the endoplasmic reticulum (ER), which is a high-capacity protein-folding compartment and whose function requires stringent protein quality-control systems. Multiprotein complexes in the ER are able to identify, remove, ubiquitinate, and deliver misfolded proteins to the 26S proteasome for degradation in the cytosol, and these events are collectively termed ER-associated degradation, or ERAD. Several steps in the ERAD pathway are facilitated by molecular chaperone networks, and the importance of ERAD is highlighted by the fact that this pathway is linked to numerous protein conformational diseases. In this review, we discuss the factors that constitute the ERAD machinery and detail how each step in the pathway occurs. We then highlight the underlying pathophysiology of protein conformational diseases associated with ERAD.
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Affiliation(s)
- Patrick G Needham
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
| | | | - Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
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8
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Gonzalez-Alegre P. Advances in molecular and cell biology of dystonia: Focus on torsinA. Neurobiol Dis 2019; 127:233-241. [DOI: 10.1016/j.nbd.2019.03.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Revised: 02/20/2019] [Accepted: 03/09/2019] [Indexed: 12/15/2022] Open
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9
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Chalfant M, Barber KW, Borah S, Thaller D, Lusk CP. Expression of TorsinA in a heterologous yeast system reveals interactions with lumenal domains of LINC and nuclear pore complex components. Mol Biol Cell 2019; 30:530-541. [PMID: 30625036 PMCID: PMC6589686 DOI: 10.1091/mbc.e18-09-0585] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
DYT1 dystonia is caused by an in-frame deletion of a glutamic acid codon in the gene encoding the AAA+ ATPase TorsinA (TorA). TorA localizes within the lumen of the nuclear envelope/endoplasmic reticulum and binds to a membrane-spanning cofactor, lamina associated polypeptide 1 (LAP1) or lumenal domain like LAP1 (LULL1), to form an ATPase; the substrate(s) of TorA remains ill-defined. Here we use budding yeast, which lack Torsins, to interrogate TorA function. We show that TorA accumulates at nuclear envelope-embedded spindle pole bodies (SPBs) in a way that requires its oligomerization and the SUN (Sad1 and UNc-84)-domain protein, Mps3. We further show that TorA physically interacts with human SUN1/2 within this system, supporting the physiological relevance of these interactions. Consistent with the idea that TorA acts on a SPB substrate, its binding to SPBs is modulated by the ATPase-stimulating activity of LAP1. TorA and TorA-ΔE reduce the fitness of cells expressing mps3 alleles, whereas TorA alone inhibits growth of cells lacking Pom152, a component of the nuclear pore complex. This genetic specificity is mirrored biochemically as TorA, but not TorA-ΔE, binds Pom152. Thus, TorA–nucleoporin interactions might be abrogated by TorA-ΔE, suggesting new experimental avenues to interrogate the molecular basis behind nuclear envelope herniations seen in mammalian cells lacking TorA function.
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Affiliation(s)
| | - Karl W. Barber
- Department of Cellular and Molecular Physiology, Yale School of Medicine, Yale University, New Haven, CT 06520
- Systems Biology Institute, Yale University, West Haven, CT 06477
| | - Sapan Borah
- Department of Cell Biology, Yale University, New Haven, CT 06520
| | - David Thaller
- Department of Cell Biology, Yale University, New Haven, CT 06520
| | - C. Patrick Lusk
- Department of Cell Biology, Yale University, New Haven, CT 06520
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10
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Beauvais G, Rodriguez-Losada N, Ying L, Zakirova Z, Watson JL, Readhead B, Gadue P, French DL, Ehrlich ME, Gonzalez-Alegre P. Exploring the Interaction Between eIF2α Dysregulation, Acute Endoplasmic Reticulum Stress and DYT1 Dystonia in the Mammalian Brain. Neuroscience 2018; 371:455-468. [DOI: 10.1016/j.neuroscience.2017.12.033] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Revised: 12/19/2017] [Accepted: 12/20/2017] [Indexed: 12/15/2022]
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11
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Human TorsinA can function in the yeast cytosol as a molecular chaperone. Biochem J 2017; 474:3439-3454. [PMID: 28871039 PMCID: PMC5628414 DOI: 10.1042/bcj20170395] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Revised: 08/25/2017] [Accepted: 09/01/2017] [Indexed: 11/17/2022]
Abstract
TorsinA (TorA) is an AAA+ (ATPases associated with diverse cellular activities) ATPase linked to dystonia type 1 (DYT1), a neurological disorder that leads to uncontrollable muscular movements. Although DYT1 is linked to a 3 bp deletion in the C-terminus of TorA, the biological function of TorA remains to be established. Here, we use the yeast Saccharomyces cerevisiae as a tractable in vivo model to explore TorA function. We demonstrate that TorA can protect yeast cells against different forms of environmental stress and show that in the absence of the molecular disaggregase Hsp104, TorA can refold heat-denatured luciferase in vivo in an ATP-dependent manner. However, this activity requires TorA to be translocated to the cytoplasm from the endoplasmic reticulum in order to access and process cytoplasmic protein aggregates. Furthermore, mutational or chemical inactivation of the ATPase activity of TorA blocks this activity. We also find that TorA can inhibit the propagation of certain conformational variants of [PSI+], the aggregated prion form of the endogenous Sup35 protein. Finally, we show that while cellular localisation remains unchanged in the dystonia-linked TorA mutant ΔE302-303, the ability of this mutant form of TorA to protect against cellular stress and to facilitate protein refolding is impaired, consistent with it being a loss-of-function mutation.
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12
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Zacchi LF, Dittmar JC, Mihalevic MJ, Shewan AM, Schulz BL, Brodsky JL, Bernstein KA. Early-onset torsion dystonia: a novel high-throughput yeast genetic screen for factors modifying protein levels of torsinAΔE. Dis Model Mech 2017; 10:1129-1140. [PMID: 28768697 PMCID: PMC5611967 DOI: 10.1242/dmm.029926] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Accepted: 07/18/2017] [Indexed: 12/12/2022] Open
Abstract
Dystonia is the third most common movement disorder, but its diagnosis and treatment remain challenging. One of the most severe types of dystonia is early-onset torsion dystonia (EOTD). The best studied and validated EOTD-associated mutation, torsinAΔE, is a deletion of a C-terminal glutamate residue in the AAA+ ATPase torsinA. TorsinA appears to be an endoplasmic reticulum (ER)/nuclear envelope chaperone with multiple roles in the secretory pathway and in determining subcellular architecture. Many functions are disabled in the torsinAΔE variant, and torsinAΔE is also less stable than wild-type torsinA and is a substrate for ER-associated degradation. Nevertheless, the molecular factors involved in the biogenesis and degradation of torsinA and torsinAΔE have not been fully explored. To identify conserved cellular factors that can alter torsinAΔE protein levels, we designed a new high-throughput, automated, genome-wide screen utilizing our validated Saccharomyces cerevisiae torsinA expression system. By analyzing the yeast non-essential gene deletion collection, we identified 365 deletion strains with altered torsinAΔE steady-state levels. One notable hit was EUG1, which encodes a member of the protein disulfide isomerase family (PDIs). PDIs reside in the ER and catalyze the formation of disulfide bonds, mediate protein quality control and aid in nascent protein folding. We validated the role of select human PDIs in torsinA biogenesis in mammalian cells and found that overexpression of PDIs reduced the levels of torsinA and torsinAΔE. Together, our data report the first genome-wide screen to identify cellular factors that alter expression levels of the EOTD-associated protein torsinAΔE. More generally, the identified hits help in dissecting the cellular machinery involved in folding and degrading a torsinA variant, and constitute potential therapeutic factors for EOTD. This screen can also be readily adapted to identify factors impacting the levels of any protein of interest, considerably expanding the applicability of yeast in both basic and applied research.
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Affiliation(s)
- Lucía F Zacchi
- School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, QLD 4072, Australia
| | - John C Dittmar
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - Michael J Mihalevic
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, 5117 Centre Avenue, UPCI Research Pavilion, 2.42e, Pittsburgh, PA 15213, USA
| | - Annette M Shewan
- School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, QLD 4072, Australia
| | - Benjamin L Schulz
- School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, QLD 4072, Australia
| | - Jeffrey L Brodsky
- Department of Biological Sciences, A320 Langley Hall, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Kara A Bernstein
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, 5117 Centre Avenue, UPCI Research Pavilion, 2.42e, Pittsburgh, PA 15213, USA
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N-glycosylation Triggers a Dual Selection Pressure in Eukaryotic Secretory Proteins. Sci Rep 2017; 7:8788. [PMID: 28821844 PMCID: PMC5562741 DOI: 10.1038/s41598-017-09173-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Accepted: 07/07/2017] [Indexed: 01/08/2023] Open
Abstract
Nearly one third of the eukaryotic proteome traverses the secretory pathway and most of these proteins are N-glycosylated in the lumen of the endoplasmic reticulum. N-glycans fulfill multiple structural and biological functions, and are crucial for productive folding of many glycoproteins. N-glycosylation involves the attachment of an oligosaccharide to selected asparagine residues in the sequence N-X-S/T (X ≠ P), a motif known as an N-glycosylation’sequon’. Mutations that create novel sequons can cause disease due to the destabilizing effect of a bulky N-glycan. Thus, an analogous process must have occurred during evolution, whenever ancestrally cytosolic proteins were recruited to the secretory pathway. Here, we show that during evolution N-glycosylation triggered a dual selection pressure on secretory pathway proteins: while sequons were positively selected in solvent exposed regions, they were almost completely eliminated from buried sites. This process is one of the sharpest evolutionary signatures of secretory pathway proteins, and was therefore critical for the evolution of an efficient secretory pathway.
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14
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Zhao C, Brown RSH, Tang CHA, Hu CCA, Schlieker C. Site-specific Proteolysis Mobilizes TorsinA from the Membrane of the Endoplasmic Reticulum (ER) in Response to ER Stress and B Cell Stimulation. J Biol Chem 2016; 291:9469-81. [PMID: 26953341 DOI: 10.1074/jbc.m115.709337] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Indexed: 01/01/2023] Open
Abstract
Torsin ATPases are the only representatives of the AAA+ ATPase family that reside in the lumen of the endoplasmic reticulum (ER) and nuclear envelope. Two of these, TorsinA and TorsinB, are anchored to the ER membrane by virtue of an N-terminal hydrophobic domain. Here we demonstrate that the imposition of ER stress leads to a proteolytic cleavage event that selectively removes the hydrophobic domain from the AAA+ domain of TorsinA, which retains catalytic activity. Both the pharmacological inhibition profile and the identified cleavage site between two juxtaposed cysteine residues are distinct from those of presently known proteases, suggesting that a hitherto uncharacterized, membrane-associated protease accounts for TorsinA processing. This processing occurs not only in stress-exposed cell lines but also in primary cells from distinct organisms including stimulated B cells, indicating that Torsin conversion in response to physiologically relevant stimuli is an evolutionarily conserved process. By establishing 5-nitroisatin as a cell-permeable inhibitor for Torsin processing, we provide the methodological framework for interfering with Torsin processing in a wide range of primary cells without the need for genetic manipulation.
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Affiliation(s)
- Chenguang Zhao
- From the Departments of Molecular Biophysics and Biochemistry and
| | | | - Chih-Hang Anthony Tang
- the Department of Translational Tumor Immunology, The Wistar Institute, Philadelphia, Pennsylvania 19104
| | - Chih-Chi Andrew Hu
- the Department of Translational Tumor Immunology, The Wistar Institute, Philadelphia, Pennsylvania 19104
| | - Christian Schlieker
- From the Departments of Molecular Biophysics and Biochemistry and Cell Biology, Yale University, New Haven, Connecticut 06520 and
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Zacchi LF, Schulz BL. N-glycoprotein macroheterogeneity: biological implications and proteomic characterization. Glycoconj J 2015; 33:359-76. [DOI: 10.1007/s10719-015-9641-3] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Revised: 11/04/2015] [Accepted: 11/20/2015] [Indexed: 10/22/2022]
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Abstract
Torsin ATPases (Torsins) belong to the widespread AAA+ (ATPases associated with a variety of cellular activities) family of ATPases, which share structural similarity but have diverse cellular functions. Torsins are outliers in this family because they lack many characteristics of typical AAA+ proteins, and they are the only members of the AAA+ family located in the endoplasmic reticulum and contiguous perinuclear space. While it is clear that Torsins have essential roles in many, if not all metazoans, their precise cellular functions remain elusive. Studying Torsins has significant medical relevance since mutations in Torsins or Torsin-associated proteins result in a variety of congenital human disorders, the most frequent of which is early-onset torsion (DYT1) dystonia, a severe movement disorder. A better understanding of the Torsin system is needed to define the molecular etiology of these diseases, potentially enabling corrective therapy. Here, we provide a comprehensive overview of the Torsin system in metazoans, discuss functional clues obtained from various model systems and organisms and provide a phylogenetic and structural analysis of Torsins and their regulatory cofactors in relation to disease-causative mutations. Moreover, we review recent data that have led to a dramatically improved understanding of these machines at a molecular level, providing a foundation for investigating the molecular defects underlying the associated movement disorders. Lastly, we discuss our ideas on how recent progress may be utilized to inform future studies aimed at determining the cellular role(s) of these atypical molecular machines and their implications for dystonia treatment options.
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Affiliation(s)
- April E Rose
- a Department of Molecular Biophysics and Biochemistry , Yale University , New Haven , CT , USA and
| | - Rebecca S H Brown
- a Department of Molecular Biophysics and Biochemistry , Yale University , New Haven , CT , USA and
| | - Christian Schlieker
- a Department of Molecular Biophysics and Biochemistry , Yale University , New Haven , CT , USA and.,b Department of Cell Biology , Yale School of Medicine , New Haven , CT , USA
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Li H, Wu HC, Liu Z, Zacchi LF, Brodsky JL, Zolkiewski M. Intracellular complexes of the early-onset torsion dystonia-associated AAA+ ATPase TorsinA. SPRINGERPLUS 2014; 3:743. [PMID: 25674472 PMCID: PMC4320221 DOI: 10.1186/2193-1801-3-743] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Accepted: 12/09/2014] [Indexed: 01/25/2023]
Abstract
A single GAG codon deletion in the gene encoding torsinA is linked to most cases of early-onset torsion dystonia. TorsinA is an ER-localized membrane-associated ATPase from the AAA+ superfamily with an unknown biological function. We investigated the formation of oligomeric complexes of torsinA in cultured mammalian cells and found that wild type torsinA associates into a complex with a molecular weight consistent with that of a homohexamer. Interestingly, the dystonia-linked variant torsinAΔE displayed a reduced propensity to form the oligomers compared to the wild type protein. We also discovered that the deletion of the N-terminal membrane-associating region of torsinA abolished oligomer formation. Our results demonstrate that the dystonia-linked mutation in the torsinA gene produces a protein variant that is deficient in maintaining its oligomeric state and suggest that ER membrane association is required to stabilize the torsinA complex.
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Affiliation(s)
- Hui Li
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS 66506 USA
| | - Hui-Chuan Wu
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS 66506 USA
| | - Zhonghua Liu
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS 66506 USA ; Department of Embryology, Carnegie Institution, Baltimore, MD 21218 USA
| | - Lucia F Zacchi
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260 USA
| | - Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260 USA
| | - Michal Zolkiewski
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS 66506 USA
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