1
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Nguyen NH, Brodsky JL. The cellular pathways that maintain the quality control and transport of diverse potassium channels. BIOCHIMICA ET BIOPHYSICA ACTA. GENE REGULATORY MECHANISMS 2023; 1866:194908. [PMID: 36638864 PMCID: PMC9908860 DOI: 10.1016/j.bbagrm.2023.194908] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 12/20/2022] [Accepted: 01/03/2023] [Indexed: 01/12/2023]
Abstract
Potassium channels are multi-subunit transmembrane proteins that permit the selective passage of potassium and play fundamental roles in physiological processes, such as action potentials in the nervous system and organismal salt and water homeostasis, which is mediated by the kidney. Like all ion channels, newly translated potassium channels enter the endoplasmic reticulum (ER) and undergo the error-prone process of acquiring post-translational modifications, folding into their native conformations, assembling with other subunits, and trafficking through the secretory pathway to reach their final destinations, most commonly the plasma membrane. Disruptions in these processes can result in detrimental consequences, including various human diseases. Thus, multiple quality control checkpoints evolved to guide potassium channels through the secretory pathway and clear potentially toxic, aggregation-prone misfolded species. We will summarize current knowledge on the mechanisms underlying potassium channel quality control in the secretory pathway, highlight diseases associated with channel misfolding, and suggest potential therapeutic routes.
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Affiliation(s)
- Nga H Nguyen
- Department of Biological Sciences, University of Pittsburgh, A320 Langley Hall, Pittsburgh, 4249 Fifth Avenue, Pittsburgh, PA 15260, USA
| | - Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh, A320 Langley Hall, Pittsburgh, 4249 Fifth Avenue, Pittsburgh, PA 15260, USA.
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2
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Hepowit NL, Denise AS, MacGurn JA. Use of Deubiquitinase Fusion Proteins to Characterize Endocytic Trafficking in Yeast. Methods Mol Biol 2023; 2591:283-295. [PMID: 36350555 DOI: 10.1007/978-1-0716-2803-4_17] [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] [Indexed: 06/16/2023]
Abstract
Ubiquitin modification is known to regulate endocytic trafficking of many different types of cargo in eukaryotic cells, but it can be challenging to determine what role, if any, ubiquitin plays in the trafficking of a novel or uncharacterized endocytic cargo. Here, we describe a useful approach that leverages fusion to deubiquitinase (DUB) catalytic domains to explore the role ubiquitin plays in endocytic trafficking. This approach can be applied to the analysis of many different endocytic cargos in different cell types, and it can also be used to study linkage specificity in endocytic trafficking. Several different trafficking assays are described to illustrate the broad utility of this "DUB fusion" approach.
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Affiliation(s)
- Nathaniel L Hepowit
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN, USA
| | - Aeva S Denise
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN, USA
| | - Jason A MacGurn
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN, USA.
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3
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Sagarika P, Yadav K, Sahi C. Volleying plasma membrane proteins from birth to death: Role of J-domain proteins. Front Mol Biosci 2022; 9:1072242. [PMID: 36589230 PMCID: PMC9798423 DOI: 10.3389/fmolb.2022.1072242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Accepted: 12/02/2022] [Indexed: 12/23/2022] Open
Abstract
The function, stability, and turnover of plasma membrane (PM) proteins are crucial for cellular homeostasis. Compared to soluble proteins, quality control of plasma membrane proteins is extremely challenging. Failure to meet the high quality control standards is detrimental to cellular and organismal health. J-domain proteins (JDPs) are among the most diverse group of chaperones that collaborate with other chaperones and protein degradation machinery to oversee cellular protein quality control (PQC). Although fragmented, the available literature from different models, including yeast, mammals, and plants, suggests that JDPs assist PM proteins with their synthesis, folding, and trafficking to their destination as well as their degradation, either through endocytic or proteasomal degradation pathways. Moreover, some JDPs interact directly with the membrane to regulate the stability and/or functionality of proteins at the PM. The deconvoluted picture emerging is that PM proteins are relayed from one JDP to another throughout their life cycle, further underscoring the versatility of the Hsp70:JDP machinery in the cell.
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4
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Vasconcelos-Cardoso M, Batista-Almeida D, Rios-Barros LV, Castro-Gomes T, Girao H. Cellular and molecular mechanisms underlying plasma membrane functionality and integrity. J Cell Sci 2022; 135:275922. [PMID: 35801807 DOI: 10.1242/jcs.259806] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The plasma membrane not only protects the cell from the extracellular environment, acting as a selective barrier, but also regulates cellular events that originate at the cell surface, playing a key role in various biological processes that are essential for the preservation of cell homeostasis. Therefore, elucidation of the mechanisms involved in the maintenance of plasma membrane integrity and functionality is of utmost importance. Cells have developed mechanisms to ensure the quality of proteins that inhabit the cell surface, as well as strategies to cope with injuries inflicted to the plasma membrane. Defects in these mechanisms can lead to the development or onset of several diseases. Despite the importance of these processes, a comprehensive and holistic perspective of plasma membrane quality control is still lacking. To tackle this gap, in this Review, we provide a thorough overview of the mechanisms underlying the identification and targeting of membrane proteins that are to be removed from the cell surface, as well as the membrane repair mechanisms triggered in both physiological and pathological conditions. A better understanding of the mechanisms underlying protein quality control at the plasma membrane can reveal promising and unanticipated targets for the development of innovative therapeutic approaches.
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Affiliation(s)
- Maria Vasconcelos-Cardoso
- University of Coimbra, Coimbra Institute for Clinical and Biomedical Research (iCBR), Faculty of Medicine, 3000-548 Coimbra, Portugal.,University of Coimbra, Center for Innovative Biomedicine and Biotechnology (CIBB), 3000-548 Coimbra, Portugal.,Clinical Academic Centre of Coimbra (CACC), 3000-548 Coimbra, Portugal
| | - Daniela Batista-Almeida
- University of Coimbra, Coimbra Institute for Clinical and Biomedical Research (iCBR), Faculty of Medicine, 3000-548 Coimbra, Portugal.,University of Coimbra, Center for Innovative Biomedicine and Biotechnology (CIBB), 3000-548 Coimbra, Portugal.,Clinical Academic Centre of Coimbra (CACC), 3000-548 Coimbra, Portugal
| | - Laura Valeria Rios-Barros
- Department of Parasitology, Federal University of Minas Gerais, Belo Horizonte, CEP 31270-901, Brazil
| | - Thiago Castro-Gomes
- Department of Parasitology, Federal University of Minas Gerais, Belo Horizonte, CEP 31270-901, Brazil
| | - Henrique Girao
- University of Coimbra, Coimbra Institute for Clinical and Biomedical Research (iCBR), Faculty of Medicine, 3000-548 Coimbra, Portugal.,University of Coimbra, Center for Innovative Biomedicine and Biotechnology (CIBB), 3000-548 Coimbra, Portugal.,Clinical Academic Centre of Coimbra (CACC), 3000-548 Coimbra, Portugal
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5
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Onabajo OO, Wang F, Lee MH, Florez-Vargas O, Obajemu A, Tanikawa C, Vargas JM, Liao SF, Song C, Huang YH, Shen CY, Banday AR, O’Brien TR, Hu Z, Matsuda K, Prokunina-Olsson L. Intracellular Accumulation of IFN-λ4 Induces ER Stress and Results in Anti-Cirrhotic but Pro-HCV Effects. Front Immunol 2021; 12:692263. [PMID: 34497603 PMCID: PMC8419317 DOI: 10.3389/fimmu.2021.692263] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Accepted: 08/02/2021] [Indexed: 01/09/2023] Open
Abstract
IFNL3/IFNL4 polymorphisms are inversely associated with the risk of chronic hepatitis C virus (HCV) infection and cirrhosis, two major risk factors for developing hepatocellular carcinoma (HCC). To further explore these inverse associations and their molecular underpinnings, we analyzed IFNL3/IFNL4 polymorphisms represented by the IFNL4 genotype (presence of rs368234815-dG or rs12979860-T alleles) in HCV patients: 2969 from Japan and 2931 from Taiwan. IFNL4 genotype was associated with an increased risk of HCV-related HCC (OR=1.28, 95%CI=1.07-1.52, P=0.0058) in the general population of Japanese patients, but not in Taiwanese patients who achieved treatment-induced viral clearance. IFNL4 genotype was also associated with a decreased risk of cirrhosis (OR=0.66, 95%CI=0.46-0.93, P=0.018, in Taiwanese patients). We then engineered HepG2 cells to inducibly express IFN-λ4 in the presence or absence of interferon lambda receptor 1 (IFNLR1). Induction of IFN-λ4 resulted in its intracellular accumulation, mainly in lysosomes and late endosomes, and increased ER stress, leading to apoptosis and reduced proliferation. We identified the very-low-density lipoprotein receptor (VLDLR), which facilitates HCV entry into hepatocytes, as a transcript induced by IFN-λ4 but not IFN-λ3. Our results suggest that the molecular mechanisms underlying the anti-cirrhotic but pro-HCV associations observed for IFNL3/IFNL4 polymorphisms are, at least in part, contributed by intracellular accumulation of IFN-λ4 causing ER stress in hepatic cells.
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Affiliation(s)
- Olusegun O. Onabajo
- Laboratory of Translational Genomics, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD, United States
| | - Fang Wang
- Laboratory of Translational Genomics, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD, United States
| | - Mei-Hsuan Lee
- Institute of Clinical Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
| | - Oscar Florez-Vargas
- Laboratory of Translational Genomics, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD, United States
| | - Adeola Obajemu
- Laboratory of Translational Genomics, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD, United States
| | - Chizu Tanikawa
- Institute of Medical Science, The University of Tokyo, Tokyo, Japan
| | - Joselin M. Vargas
- Laboratory of Translational Genomics, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD, United States
| | - Shu-Fen Liao
- Institute of Clinical Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
- Institute of Statistical Science, Academia Sinica, Taipei, Taiwan
| | - Ci Song
- Department of Epidemiology, School of Public Health, Nanjing Medical University, Nanjing, China
| | - Yu-Han Huang
- Institute of Clinical Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
| | - Chen-Yang Shen
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - A. Rouf Banday
- Laboratory of Translational Genomics, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD, United States
| | - Thomas R. O’Brien
- Infections and Immunoepidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Rockville, MD, United States
| | - Zhibin Hu
- Department of Epidemiology, School of Public Health, Nanjing Medical University, Nanjing, China
| | - Koichi Matsuda
- Graduate School of Frontier Sciences, The University of Tokyo, Tokyo, Japan
| | - Ludmila Prokunina-Olsson
- Laboratory of Translational Genomics, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD, United States
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6
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Sardana R, Emr SD. Membrane Protein Quality Control Mechanisms in the Endo-Lysosome System. Trends Cell Biol 2021; 31:269-283. [PMID: 33414051 DOI: 10.1016/j.tcb.2020.11.011] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Revised: 11/26/2020] [Accepted: 11/30/2020] [Indexed: 01/12/2023]
Abstract
Protein quality control (PQC) machineries play a critical role in selective identification and removal of mistargeted, misfolded, and aberrant proteins. This task is extremely complicated due to the enormous diversity of the proteome. It also requires nuanced and careful differentiation between 'normal' and 'folding intermediates' from 'abnormal' and 'misfolded' protein states. Multiple genetic and proteomic approaches have started to delineate the molecular underpinnings of how these machineries recognize their target and how their activity is regulated. In this review, we summarize our understanding of the various E3 ubiquitin ligases and associated machinery that mediate PQC in the endo-lysosome system in yeast and humans, how they are regulated, and mechanisms of target selection, with the intent of guiding future research in this area.
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Affiliation(s)
- Richa Sardana
- Weill Institute of Cell and Molecular Biology, Cornell University, Ithaca, NY, USA; Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, USA
| | - Scott D Emr
- Weill Institute of Cell and Molecular Biology, Cornell University, Ithaca, NY, USA; Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, USA.
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7
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Affiliation(s)
- Brant M Webster
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Holly K Gildea
- Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA, USA
| | - Andrew Dillin
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA. .,Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA, USA. .,Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, CA, USA.
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8
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Braun D, Schweizer U. The Protein Translocation Defect of MCT8 L291R Is Rescued by Sodium Phenylbutyrate. Eur Thyroid J 2020; 9:269-280. [PMID: 33088796 PMCID: PMC7548921 DOI: 10.1159/000507439] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 03/24/2020] [Indexed: 11/19/2022] Open
Abstract
INTRODUCTION The monocarboxylate transporter 8 (MCT8; SLC16A2) is a specific transporter for thyroid hormones. MCT8 deficiency, formerly known as the Allan-Herndon-Dudley syndrome, is a rare genetic disease that leads to neurological impairments and muscle weakness. Current experimental treatment options rely on thyromimetic agonists that do not depend on MCT8 for cellular uptake. Another approach comes from studies with the chemical chaperone sodium phenylbutyrate (NaPB), which was able to stabilize MCT8 mutants having protein folding defects in vitro. In addition, NaPB is known as a compound that assists with plasma membrane translocation. OBJECTIVE The pathogenic MCT8L291R leads to the same severe neurological impairments found for other MCT8-deficient patients but, unexpectedly, lacks alterations in plasma 3,3',5-triiodothyronine (T3) levels. Here we tried to unravel the underlying mechanism of MCT8 deficiency and tested whether the pathogenic MCT8L291R mutant responds to NaPB treatment. Therefore, we overexpressed the mutant in Madin-Darby canine kidney cells in the human choriocarcinoma cell line JEG1 and in COS7 cells of African green monkey origin. RESULTS In our recent study we describe that the MCT8L291R mutation most likely leads to a translocation defect. The pathogenic mutant is not located at the plasma membrane, but shows overlapping expression with a marker protein of the lysosome. Mutation of the corresponding amino acid in murine Mct8 (Mct8L223R) displays a similar effect on cell surface expression and transport function as seen before for MCT8L291R. NaPB was able to correct the translocation defect of MCT8L291R/Mct8L223R and restored protein function by increasing T3 transport activity. Furthermore, we detected enhanced mRNA levels of wild-type and mutant MCT8/Mct8 after NaPB treatment. The increase in mRNA levels could be an explanation for the positive effect on protein expression and function detected for wild-type MCT8. CONCLUSION NaPB is not only suitable for the treatment of mutations leading to misfolding and protein degradation, but also for a mutant wrongly sorted inside a cell which is otherwise functional.
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Affiliation(s)
- Doreen Braun
- *Doreen Braun, Institut für Biochemie und Molekularbiologie, Medizinische Fakultät, Rheinische Friedrich-Wilhelms-Universität Bonn, Nussallee 11, DE–53115 Bonn (Germany),
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9
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Mat Nanyan NSB, Takagi H. Proline Homeostasis in Saccharomyces cerevisiae: How Does the Stress-Responsive Transcription Factor Msn2 Play a Role? Front Genet 2020; 11:438. [PMID: 32411186 PMCID: PMC7198862 DOI: 10.3389/fgene.2020.00438] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Accepted: 04/09/2020] [Indexed: 12/12/2022] Open
Abstract
Overexpression of MSN2, which is the transcription factor gene in response to stress, is well-known to increase the tolerance of the yeast Saccharomyces cerevisiae cells to a wide variety of environmental stresses. Recent studies have found that the Msn2 is a feasible potential mediator of proline homeostasis in yeast. This result is based on the finding that overexpression of the MSN2 gene exacerbates the cytotoxicity of yeast to various amino acid analogs whose uptake is increased by the active amino acid permeases localized on the plasma membrane as a result of a dysfunctional deubiquitination process. Increased understanding of the cellular responses induced by the Msn2-mediated proline incorporation will provide better comprehension of how cells respond to and counteract to different kinds of stimuli and will also contribute to the breeding of industrial yeast strains with increased productivity.
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Affiliation(s)
| | - Hiroshi Takagi
- Division of Biological Science, Graduate School of Science and Technology, Nara Institute of Science and Technology, Ikoma, Japan
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10
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Mat Nanyan NSB, Watanabe D, Sugimoto Y, Takagi H. Effect of the deubiquitination enzyme gene UBP6 on the stress-responsive transcription factor Msn2-mediated control of the amino acid permease Gnp1 in yeast. J Biosci Bioeng 2020; 129:423-427. [DOI: 10.1016/j.jbiosc.2019.10.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Revised: 09/08/2019] [Accepted: 10/01/2019] [Indexed: 11/16/2022]
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11
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Nielsen CP, MacGurn JA. Coupling Conjugation and Deconjugation Activities to Achieve Cellular Ubiquitin Dynamics. Trends Biochem Sci 2020; 45:427-439. [PMID: 32311336 DOI: 10.1016/j.tibs.2020.01.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2019] [Revised: 01/24/2020] [Accepted: 01/28/2020] [Indexed: 12/19/2022]
Abstract
In eukaryotic cells, proteome remodeling is mediated by the ubiquitin-proteasome system, which regulates protein degradation, trafficking, and signaling events in the cell. Interplay between the cellular proteome and ubiquitin is complex and dynamic and many regulatory features that support this system have only recently come into focus. An unexpected recurring feature in this system is the physical interaction between E3 ubiquitin ligases and deubiquitylases (DUBs). Recent studies have reported on the regulatory significance of DUB-E3 interactions and it is becoming clear that they play important but complicated roles in the regulation of diverse cellular processes. Here, we summarize the current understanding of interactions between ubiquitin conjugation and deconjugation machineries and we examine the regulatory logic of these enigmatic complexes.
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Affiliation(s)
- Casey P Nielsen
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN, USA
| | - Jason A MacGurn
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN, USA.
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12
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Cerri S, Blandini F. Role of Autophagy in Parkinson's Disease. Curr Med Chem 2019; 26:3702-3718. [PMID: 29484979 DOI: 10.2174/0929867325666180226094351] [Citation(s) in RCA: 74] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2017] [Revised: 01/30/2018] [Accepted: 02/13/2018] [Indexed: 12/11/2022]
Abstract
Autophagy is an essential catabolic mechanism that delivers misfolded proteins and damaged organelles to the lysosome for degradation. Autophagy pathways include macroautophagy, chaperone-mediated autophagy and microautophagy, each involving different mechanisms of substrate delivery to lysosome. Defects of these pathways and the resulting accumulation of protein aggregates represent a common pathobiological feature of neurodegenerative disorders such as Alzheimer, Parkinson and Huntington disease. This review provides an overview of the role of autophagy in Parkinson's disease (PD) by summarizing the most relevant genetic and experimental evidence showing how this process can contribute to disease pathogenesis. Given lysosomes take part in the final step of the autophagic process, the role of lysosomal defects in the impairment of autophagy and their impact on disease will also be discussed. A glance on the role of non-neuronal autophagy in the pathogenesis of PD will be included. Moreover, we will examine novel pharmacological targets and therapeutic strategies that, by boosting autophagy, may be theoretically beneficial for PD. Special attention will be focused on natural products, such as phenolic compounds, that are receiving increasing consideration due to their potential efficacy associated with low toxicity. Although many efforts have been made to elucidate autophagic process, the development of new therapeutic interventions requires a deeper understanding of the mechanisms that may lead to autophagy defects in PD and should take into account the multifactorial nature of the disease as well as the phenotypic heterogeneity of PD patients.
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Affiliation(s)
- Silvia Cerri
- Laboratory of Cellular and Molecular Neurobiology, IRCCS Mondino Foundation, Pavia, Italy
| | - Fabio Blandini
- Laboratory of Cellular and Molecular Neurobiology, IRCCS Mondino Foundation, Pavia, Italy
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13
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Sun Z, Brodsky JL. Protein quality control in the secretory pathway. J Cell Biol 2019; 218:3171-3187. [PMID: 31537714 PMCID: PMC6781448 DOI: 10.1083/jcb.201906047] [Citation(s) in RCA: 233] [Impact Index Per Article: 46.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Revised: 07/22/2019] [Accepted: 08/29/2019] [Indexed: 12/23/2022] Open
Abstract
Protein folding is inherently error prone, especially in the endoplasmic reticulum (ER). Even with an elaborate network of molecular chaperones and protein folding facilitators, misfolding can occur quite frequently. To maintain protein homeostasis, eukaryotes have evolved a series of protein quality-control checkpoints. When secretory pathway quality-control pathways fail, stress response pathways, such as the unfolded protein response (UPR), are induced. In addition, the ER, which is the initial hub of protein biogenesis in the secretory pathway, triages misfolded proteins by delivering substrates to the proteasome or to the lysosome/vacuole through ER-associated degradation (ERAD) or ER-phagy. Some misfolded proteins escape the ER and are instead selected for Golgi quality control. These substrates are targeted for degradation after retrieval to the ER or delivery to the lysosome/vacuole. Here, we discuss how these guardian pathways function, how their activities intersect upon induction of the UPR, and how decisions are made to dispose of misfolded proteins in the secretory pathway.
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Affiliation(s)
- Zhihao Sun
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA
| | - Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA
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14
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Bonsi P, Ponterio G, Vanni V, Tassone A, Sciamanna G, Migliarini S, Martella G, Meringolo M, Dehay B, Doudnikoff E, Zachariou V, Goodchild RE, Mercuri NB, D'Amelio M, Pasqualetti M, Bezard E, Pisani A. RGS9-2 rescues dopamine D2 receptor levels and signaling in DYT1 dystonia mouse models. EMBO Mol Med 2019; 11:emmm.201809283. [PMID: 30552094 PMCID: PMC6328939 DOI: 10.15252/emmm.201809283] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Dopamine D2 receptor signaling is central for striatal function and movement, while abnormal activity is associated with neurological disorders including the severe early-onset DYT1 dystonia. Nevertheless, the mechanisms that regulate D2 receptor signaling in health and disease remain poorly understood. Here, we identify a reduced D2 receptor binding, paralleled by an abrupt reduction in receptor protein level, in the striatum of juvenile Dyt1 mice. This occurs through increased lysosomal degradation, controlled by competition between β-arrestin 2 and D2 receptor binding proteins. Accordingly, we found lower levels of striatal RGS9-2 and spinophilin. Further, we show that genetic depletion of RGS9-2 mimics the D2 receptor loss of DYT1 dystonia striatum, whereas RGS9-2 overexpression rescues both receptor levels and electrophysiological responses in Dyt1 striatal neurons. This work uncovers the molecular mechanism underlying D2 receptor downregulation in Dyt1 mice and in turn explains why dopaminergic drugs lack efficacy in DYT1 patients despite significant evidence for striatal D2 receptor dysfunction. Our data also open up novel avenues for disease-modifying therapeutics to this incurable neurological disorder.
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Affiliation(s)
- Paola Bonsi
- Laboratory of Neurophysiology and Plasticity, IRCCS Fondazione Santa Lucia, Rome, Italy
| | - Giulia Ponterio
- Laboratory of Neurophysiology and Plasticity, IRCCS Fondazione Santa Lucia, Rome, Italy.,Department of Systems Medicine, University Tor Vergata, Rome, Italy
| | - Valentina Vanni
- Laboratory of Neurophysiology and Plasticity, IRCCS Fondazione Santa Lucia, Rome, Italy.,Department of Systems Medicine, University Tor Vergata, Rome, Italy
| | - Annalisa Tassone
- Laboratory of Neurophysiology and Plasticity, IRCCS Fondazione Santa Lucia, Rome, Italy.,Department of Systems Medicine, University Tor Vergata, Rome, Italy
| | - Giuseppe Sciamanna
- Laboratory of Neurophysiology and Plasticity, IRCCS Fondazione Santa Lucia, Rome, Italy.,Department of Systems Medicine, University Tor Vergata, Rome, Italy
| | - Sara Migliarini
- Unit of Cell and Developmental Biology, Department of Biology, University of Pisa, Pisa, Italy
| | - Giuseppina Martella
- Laboratory of Neurophysiology and Plasticity, IRCCS Fondazione Santa Lucia, Rome, Italy.,Department of Systems Medicine, University Tor Vergata, Rome, Italy
| | - Maria Meringolo
- Laboratory of Neurophysiology and Plasticity, IRCCS Fondazione Santa Lucia, Rome, Italy.,Department of Systems Medicine, University Tor Vergata, Rome, Italy
| | - Benjamin Dehay
- Université de Bordeaux, Institut des Maladies Neurodégénératives, UMR 5293, Bordeaux, France.,CNRS, Institut des Maladies Neurodégénératives, UMR 5293, Bordeaux, France
| | - Evelyne Doudnikoff
- Université de Bordeaux, Institut des Maladies Neurodégénératives, UMR 5293, Bordeaux, France.,CNRS, Institut des Maladies Neurodégénératives, UMR 5293, Bordeaux, France
| | - Venetia Zachariou
- Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Rose E Goodchild
- Department of Neurosciences, VIB-KU Leuven Center for Brain and Disease Research, KU Leuven, Leuven, Belgium
| | - Nicola B Mercuri
- Laboratory of Neurophysiology and Plasticity, IRCCS Fondazione Santa Lucia, Rome, Italy.,Department of Systems Medicine, University Tor Vergata, Rome, Italy
| | - Marcello D'Amelio
- Laboratory Molecular Neurosciences, IRCCS Fondazione Santa Lucia, Rome, Italy.,Unit of Molecular Neurosciences, Department of Medicine, University Campus-Biomedico, Rome, Italy
| | - Massimo Pasqualetti
- Unit of Cell and Developmental Biology, Department of Biology, University of Pisa, Pisa, Italy.,Center for Neuroscience and Cognitive Systems @UniTn, Istituto Italiano di Tecnologia, Rovereto, Italy
| | - Erwan Bezard
- Université de Bordeaux, Institut des Maladies Neurodégénératives, UMR 5293, Bordeaux, France.,CNRS, Institut des Maladies Neurodégénératives, UMR 5293, Bordeaux, France
| | - Antonio Pisani
- Laboratory of Neurophysiology and Plasticity, IRCCS Fondazione Santa Lucia, Rome, Italy .,Department of Systems Medicine, University Tor Vergata, Rome, Italy
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15
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Lee S, Ho HC, Tumolo JM, Hsu PC, MacGurn JA. Methionine triggers Ppz-mediated dephosphorylation of Art1 to promote cargo-specific endocytosis. J Cell Biol 2019; 218:977-992. [PMID: 30610170 PMCID: PMC6400557 DOI: 10.1083/jcb.201712144] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Revised: 11/11/2018] [Accepted: 12/21/2018] [Indexed: 12/15/2022] Open
Abstract
Regulation of plasma membrane (PM) protein abundance by selective endocytosis is critical for cellular adaptation to stress or changing nutrient availability. One example involves rapid endocytic turnover of Mup1, a yeast methionine transporter, in response to increased methionine availability. Here, we report that methionine triggers rapid translocation of the ubiquitin ligase adaptor Art1 to the PM and dephosphorylation of Art1 at specific threonine residues. This methionine-induced dephosphorylation of Art1 is mediated by Ppz phosphatases, and analysis of phosphomimetic and phosphorylation-defective variants of Art1 indicates that these events toggle Art1 recognition of Mup1 at the PM. Importantly, we find that Ppz phosphatases are dispensable for Art1 PM translocation, but are required for Art1 interaction with Mup1. Based on our findings, we propose that methionine influx triggers Art1 translocation to the PM, followed by Ppz-mediated dephosphorylation which promotes cargo recognition at the PM.
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Affiliation(s)
- Sora Lee
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN
| | - Hsuan-Chung Ho
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY
| | - Jessica M Tumolo
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN
| | - Pi-Chiang Hsu
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY
| | - Jason A MacGurn
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN
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16
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FKBP8 Enhances Protein Stability of the CLC-1 Chloride Channel at the Plasma Membrane. Int J Mol Sci 2018; 19:ijms19123783. [PMID: 30487393 PMCID: PMC6320802 DOI: 10.3390/ijms19123783] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Revised: 11/18/2018] [Accepted: 11/26/2018] [Indexed: 01/23/2023] Open
Abstract
Mutations in the skeletal muscle-specific CLC-1 chloride channel are associated with the human hereditary disease myotonia congenita. The molecular pathophysiology underlying some of the disease-causing mutations can be ascribed to defective human CLC-1 protein biosynthesis. CLC-1 protein folding is assisted by several molecular chaperones and co-chaperones, including FK506-binding protein 8 (FKBP8). FKBP8 is generally considered an endoplasmic reticulum- and mitochondrion-resident membrane protein, but is not thought to contribute to protein quality control at the cell surface. Herein, we aim to test the hypothesis that FKBP8 may regulate CLC-1 protein at the plasma membrane. Surface biotinylation and subcellular fractionation analyses reveal that a portion of FKBP8 is present at the plasma membrane, and that co-expression with CLC-1 enhances surface localization of FKBP8. Immunoblotting analyses of plasma membrane proteins purified from skeletal muscle further confirm surface localization of FKBP8. Importantly, FKBP8 promotes CLC-1 protein stability at the plasma membrane. Together, our data underscore the importance of FKBP8 in the peripheral quality control of CLC-1 channel.
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17
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Mackie TD, Kim BY, Subramanya AR, Bain DJ, O'Donnell AF, Welling PA, Brodsky JL. The endosomal trafficking factors CORVET and ESCRT suppress plasma membrane residence of the renal outer medullary potassium channel (ROMK). J Biol Chem 2018; 293:3201-3217. [PMID: 29311259 PMCID: PMC5836112 DOI: 10.1074/jbc.m117.819086] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Revised: 01/02/2018] [Indexed: 11/06/2022] Open
Abstract
Protein trafficking can act as the primary regulatory mechanism for ion channels with high open probabilities, such as the renal outer medullary (ROMK) channel. ROMK, also known as Kir1.1 (KCNJ1), is the major route for potassium secretion into the pro-urine and plays an indispensable role in regulating serum potassium and urinary concentrations. However, the cellular machinery that regulates ROMK trafficking has not been fully defined. To identify regulators of the cell-surface population of ROMK, we expressed a pH-insensitive version of the channel in the budding yeast Saccharomyces cerevisiae We determined that ROMK primarily resides in the endoplasmic reticulum (ER), as it does in mammalian cells, and is subject to ER-associated degradation (ERAD). However, sufficient ROMK levels on the plasma membrane rescued growth on low-potassium medium of yeast cells lacking endogenous potassium channels. Next, we aimed to identify the biological pathways most important for ROMK regulation. Therefore, we used a synthetic genetic array to identify non-essential genes that reduce the plasma membrane pool of ROMK in potassium-sensitive yeast cells. Genes identified in this screen included several members of the endosomal complexes required for transport (ESCRT) and the class-C core vacuole/endosome tethering (CORVET) complexes. Mass spectroscopy analysis confirmed that yeast cells lacking an ESCRT component accumulate higher potassium concentrations. Moreover, silencing of ESCRT and CORVET components increased ROMK levels at the plasma membrane in HEK293 cells. Our results indicate that components of the post-endocytic pathway influence the cell-surface density of ROMK and establish that components in this pathway modulate channel activity.
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Affiliation(s)
| | - Bo-Young Kim
- the Department of Physiology, University of Maryland at Baltimore, Baltimore, Maryland 21201
| | - Arohan R Subramanya
- the Departments of Medicine and Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
- the Medicine and Research Services, Veterans Affairs Pittsburgh Healthcare System, Pittsburgh, Pennsylvania 15240, and
| | - Daniel J Bain
- Geology and Environmental Science, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
| | - Allyson F O'Donnell
- the Department of Biological Sciences, Duquesne University, Pittsburgh, Pennsylvania 15282
| | - Paul A Welling
- the Department of Physiology, University of Maryland at Baltimore, Baltimore, Maryland 21201
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18
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Kashlan OB, Kinlough CL, Myerburg MM, Shi S, Chen J, Blobner BM, Buck TM, Brodsky JL, Hughey RP, Kleyman TR. N-linked glycans are required on epithelial Na + channel subunits for maturation and surface expression. Am J Physiol Renal Physiol 2017; 314:F483-F492. [PMID: 29187368 DOI: 10.1152/ajprenal.00195.2017] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Epithelial Na+ channel (ENaC) subunits undergo N-linked glycosylation in the endoplasmic reticulum where they assemble into an αβγ complex. Six, 13, and 5 consensus sites (Asn-X-Ser/Thr) for N-glycosylation reside in the extracellular domains of the mouse α-, β-, and γ-subunits, respectively. Because the importance of ENaC N-linked glycans has not been fully addressed, we examined the effect of preventing N-glycosylation of specific subunits on channel function, expression, maturation, and folding. Heterologous expression in Xenopus oocytes or Fischer rat thyroid cells with αβγ-ENaC lacking N-linked glycans on a single subunit reduced ENaC activity as well as the inhibitory response to extracellular Na+. The lack of N-linked glycans on the β-subunit also precluded channel activation by trypsin. However, channel activation by shear stress was N-linked glycan independent, regardless of which subunit was modified. We also discovered that the lack of N-linked glycans on any one subunit reduced the total and surface levels of cognate subunits. The lack of N-linked glycans on the β-subunit had the largest effect on total levels, with the lack of N-linked glycans on the γ- and α-subunits having intermediate and modest effects, respectively. Finally, channels with wild-type β-subunits were more sensitive to limited trypsin proteolysis than channels lacking N-linked glycans on the β-subunit. Our results indicate that N-linked glycans on each subunit are required for proper folding, maturation, surface expression, and function of the channel.
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Affiliation(s)
- Ossama B Kashlan
- Renal Electrolyte Division, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania.,Department of Computational and Systems Biology, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Carol L Kinlough
- Renal Electrolyte Division, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Michael M Myerburg
- Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Shujie Shi
- Renal Electrolyte Division, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Jingxin Chen
- Renal Electrolyte Division, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Brandon M Blobner
- Renal Electrolyte Division, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Teresa M Buck
- Department of Biological Sciences, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Rebecca P Hughey
- Renal Electrolyte Division, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania.,Department of Cell Biology, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Thomas R Kleyman
- Renal Electrolyte Division, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania.,Department of Cell Biology, University of Pittsburgh , Pittsburgh, Pennsylvania.,Department of Pharmacology and Chemical Biology, University of Pittsburgh , Pittsburgh, Pennsylvania
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19
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Abstract
A healthy proteome is essential for cell survival. Protein misfolding is linked to a rapidly expanding list of human diseases, ranging from neurodegenerative diseases to aging and cancer. Many of these diseases are characterized by the accumulation of misfolded proteins in intra- and extracellular inclusions, such as amyloid plaques. The clear link between protein misfolding and disease highlights the need to better understand the elaborate machinery that manages proteome homeostasis, or proteostasis, in the cell. Proteostasis depends on a network of molecular chaperones and clearance pathways involved in the recognition, refolding, and/or clearance of aberrant proteins. Recent studies reveal that an integral part of the cellular management of misfolded proteins is their spatial sequestration into several defined compartments. Here, we review the properties, function, and formation of these compartments. Spatial sequestration plays a central role in protein quality control and cellular fitness and represents a critical link to the pathogenesis of protein aggregation-linked diseases.
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Affiliation(s)
| | - Rahul S Samant
- Department of Biology, Stanford University, Stanford, California 94305; , ,
| | - Judith Frydman
- Department of Biology, Stanford University, Stanford, California 94305; , ,
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20
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Cellular proteostasis: degradation of misfolded proteins by lysosomes. Essays Biochem 2017; 60:173-180. [PMID: 27744333 PMCID: PMC5065703 DOI: 10.1042/ebc20160005] [Citation(s) in RCA: 95] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Accepted: 04/29/2016] [Indexed: 12/16/2022]
Abstract
Proteostasis refers to the regulation of the cellular concentration, folding, interactions and localization of each of the proteins that comprise the proteome. One essential element of proteostasis is the disposal of misfolded proteins by the cellular pathways of protein degradation. Lysosomes are an important site for the degradation of misfolded proteins, which are trafficked to this organelle by the pathways of macroautophagy, chaperone-mediated autophagy and endocytosis. Conversely, amyloid diseases represent a failure in proteostasis, in which proteins misfold, forming amyloid deposits that are not degraded effectively by cells. Amyloid may then exacerbate this failure by disrupting autophagy and lysosomal proteolysis. However, targeting the pathways that regulate autophagy and the biogenesis of lysosomes may present approaches that can rescue cells from the deleterious effects of amyloidogenic proteins.
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21
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Desdín-Micó G, Mittelbrunn M. Role of exosomes in the protection of cellular homeostasis. Cell Adh Migr 2017; 11:127-134. [PMID: 27875097 PMCID: PMC5351736 DOI: 10.1080/19336918.2016.1251000] [Citation(s) in RCA: 125] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Revised: 10/13/2016] [Accepted: 10/17/2016] [Indexed: 12/20/2022] Open
Abstract
Due to their ability to shuttle proteins, lipids and genetic material between distant cells, exosomes promote extensive phenotypic changes in recipient cells, modulating immune responses, cellular migration, cancer metastasis or the spreading of neurotoxic protein aggregates in neurodegenerative diseases. Besides intercellular communication, exosome biogenesis and secretion permit the rapid release of a selective repertoire of compounds, conferring cells with an additional mechanism to fight alterations in protein, lipid or RNA homeostasis during stress or pathological conditions. Here, we review the dual role of the different quality control mechanisms arising from the endolysosomal system and the diverse situations that control the decision between degradation or secretion. The crosstalk between exosome secretion and the different cellular degradation mechanisms confers an additional layer of protection to maintain cellular integrity and homeostasis in a number of physiological and pathological conditions.
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Affiliation(s)
| | - María Mittelbrunn
- Instituto de Investigación del Hospital 12 de Octubre, Madrid, Spain
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22
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Kock C, Arlt H, Ungermann C, Heinisch JJ. Yeast cell wall integrity sensors form specific plasma membrane microdomains important for signalling. Cell Microbiol 2016; 18:1251-67. [DOI: 10.1111/cmi.12635] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2016] [Revised: 06/14/2016] [Accepted: 06/17/2016] [Indexed: 02/06/2023]
Affiliation(s)
- Christian Kock
- Universität Osnabrück; Fachbereich Biologie/Chemie, AG Genetik; 49076 Osnabrück Germany
| | - Henning Arlt
- Universität Osnabrück; Fachbereich Biologie/Chemie, AG Biochemie; 49076 Osnabrück Germany
| | - Christian Ungermann
- Universität Osnabrück; Fachbereich Biologie/Chemie, AG Biochemie; 49076 Osnabrück Germany
| | - Jürgen J. Heinisch
- Universität Osnabrück; Fachbereich Biologie/Chemie, AG Genetik; 49076 Osnabrück Germany
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23
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Fang F, Zhao Q, Sui Z, Liang Y, Jiang H, Yang K, Liang Z, Zhang L, Zhang Y. Glycan Moieties as Bait to Fish Plasma Membrane Proteins. Anal Chem 2016; 88:5065-71. [DOI: 10.1021/acs.analchem.6b01082] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Fei Fang
- National Chromatographic R. & A. Center, Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Science, Dalian, Liaoning 116023, China
- University of Chinese Academy of Sciences, Beijing 100039, China
| | - Qun Zhao
- National Chromatographic R. & A. Center, Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Science, Dalian, Liaoning 116023, China
| | - Zhigang Sui
- National Chromatographic R. & A. Center, Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Science, Dalian, Liaoning 116023, China
| | - Yu Liang
- National Chromatographic R. & A. Center, Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Science, Dalian, Liaoning 116023, China
| | - Hao Jiang
- National Chromatographic R. & A. Center, Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Science, Dalian, Liaoning 116023, China
- University of Chinese Academy of Sciences, Beijing 100039, China
| | - Kaiguang Yang
- National Chromatographic R. & A. Center, Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Science, Dalian, Liaoning 116023, China
| | - Zhen Liang
- National Chromatographic R. & A. Center, Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Science, Dalian, Liaoning 116023, China
| | - Lihua Zhang
- National Chromatographic R. & A. Center, Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Science, Dalian, Liaoning 116023, China
| | - Yukui Zhang
- National Chromatographic R. & A. Center, Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Science, Dalian, Liaoning 116023, China
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24
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Nickerson DP, Merz AJ. LUCID: A Quantitative Assay of ESCRT-Mediated Cargo Sorting into Multivesicular Bodies. Traffic 2015; 16:1318-29. [PMID: 26424513 DOI: 10.1111/tra.12331] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Revised: 09/09/2015] [Accepted: 09/09/2015] [Indexed: 11/30/2022]
Abstract
Endosomes are transportation nodes, mediating selective transport of soluble and transmembrane cargos to and from the Golgi apparatus, plasma membrane and lysosomes. As endosomes mature to become multivesicular bodies (MVBs), Endosomal Sorting Complexes Required for Transport (ESCRTs) selectively incorporate transmembrane cargos into vesicles that bud into the endosome lumen. Luminal vesicles and their cargoes are targeted for destruction when MVBs fuse with lysosomes. Common assays of endosomal luminal targeting, including fluorescence microscopy and monitoring of proteolytic cargo maturation, possess significant limitations. We present a quantitative assay system called LUCID (LUCiferase reporter of Intraluminal Deposition) that monitors exposure of chimeric luciferase-cargo reporters to cytosol. Luciferase-chimera signal increases when sorting to the endosome lumen is disrupted, and silencing of signal from the chimera depends upon luminal delivery of the reporter rather than proteolytic degradation. The system presents several advantages, including rapidity, microscale operation and a high degree of reproducibility that enables detection of subtle phenotypic differences. Luciferase reporters provide linear signal over an extremely broad dynamic range, allowing analysis of reporter traffic even at anemic levels of expression. Furthermore, LUCID reports transport kinetics when applied to inducible trafficking reporters.
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Affiliation(s)
- Daniel P Nickerson
- Department of Biochemistry, University of Washington, Seattle, WA, 98195-7350, USA
| | - Alexey J Merz
- Department of Biochemistry, University of Washington, Seattle, WA, 98195-7350, USA.,Department of Physiology and Biophysics, University of Washington, Seattle, WA, 98195-7350, USA
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25
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Webster BM, Lusk CP. Border Safety: Quality Control at the Nuclear Envelope. Trends Cell Biol 2015; 26:29-39. [PMID: 26437591 DOI: 10.1016/j.tcb.2015.08.002] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Revised: 07/27/2015] [Accepted: 08/07/2015] [Indexed: 10/23/2022]
Abstract
The unique biochemical identity of the nuclear envelope confers its capacity to establish a barrier that protects the nuclear compartment and directly contributes to nuclear function. Recent work uncovered quality control mechanisms employing the endosomal sorting complexes required for transport (ESCRT) machinery and a new arm of endoplasmic reticulum-associated protein degradation (ERAD) to counteract the unfolding, damage, or misassembly of nuclear envelope proteins and ensure the integrity of the nuclear envelope membranes. Moreover, cells have the capacity to recognize and triage defective nuclear pore complexes to prevent their inheritance and preserve the longevity of progeny. These mechanisms serve to highlight the diverse strategies used by cells to maintain nuclear compartmentalization; we suggest they mitigate the progression and severity of diseases associated with nuclear envelope malfunction such as the laminopathies.
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