1
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Goncalves D, Duy DL, Peffer S, Morano KA. Cytoplasmic redox imbalance in the thioredoxin system activates Hsf1 and results in hyperaccumulation of the sequestrase Hsp42 with misfolded proteins. Mol Biol Cell 2024; 35:ar53. [PMID: 38381577 PMCID: PMC11064659 DOI: 10.1091/mbc.e23-07-0296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 02/09/2024] [Accepted: 02/16/2024] [Indexed: 02/23/2024] Open
Abstract
Cells employ multiple systems to maintain homeostasis when experiencing environmental stress. For example, the folding of nascent polypeptides is exquisitely sensitive to proteotoxic stressors including heat, pH, and oxidative stress, and is safeguarded by a network of protein chaperones that concentrate potentially toxic misfolded proteins into transient assemblies to promote folding or degradation. The redox environment itself is buffered by both cytosolic and organellar thioredoxin and glutathione pathways. How these systems are linked is poorly understood. Here, we determine that specific disruption of the cytosolic thioredoxin system resulted in constitutive activation of the heat shock response in Saccharomyces cerevisiae and accumulation of the sequestrase Hsp42 into an exaggerated and persistent juxtanuclear quality control (JUNQ) compartment. Terminally misfolded proteins also accumulated in this compartment in thioredoxin reductase (TRR1)-deficient cells, despite apparently normal formation and dissolution of transient cytoplasmic quality control (CytoQ) bodies during heat shock. Notably, cells lacking TRR1 and HSP42 exhibited severe synthetic slow growth exacerbated by oxidative stress, signifying a critical role for Hsp42 under redox-challenged conditions. Finally, we demonstrated that Hsp42 localization patterns in trr1∆ cells mimic those observed in chronically aging and glucose-starved cells, linking nutrient depletion and redox imbalance with management of misfolded proteins via a process of long-term sequestration.
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Affiliation(s)
- Davi Goncalves
- Department of Microbiology and Molecular Genetics, McGovern Medical School at UTHealth Houston, Houston, TX 77030
| | - Duong Long Duy
- Department of Microbiology and Molecular Genetics, McGovern Medical School at UTHealth Houston, Houston, TX 77030
| | - Sara Peffer
- Department of Microbiology and Molecular Genetics, McGovern Medical School at UTHealth Houston, Houston, TX 77030
- Microbiology and Infectious Disease Program, MD Anderson UTHealth Graduate School at UTHealth Houston, Houston, TX 77030
| | - Kevin A. Morano
- Department of Microbiology and Molecular Genetics, McGovern Medical School at UTHealth Houston, Houston, TX 77030
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2
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Rodriguez Tirado C, Wang C, Li X, Deng S, Gonzalez J, Johnson NA, Xu Y, Metang LA, Sundar Rajan M, Yang Y, Yin Y, Hofstad M, Raj GV, Zhang S, Lemoff A, He W, Fan J, Wang Y, Wang T, Mu P. UBE2J1 is the E2 ubiquitin-conjugating enzyme regulating androgen receptor degradation and antiandrogen resistance. Oncogene 2024; 43:265-280. [PMID: 38030789 PMCID: PMC10798893 DOI: 10.1038/s41388-023-02890-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Revised: 10/27/2023] [Accepted: 11/07/2023] [Indexed: 12/01/2023]
Abstract
Prostate cancer (PCa) is primarily driven by aberrant Androgen Receptor (AR) signaling. Although there has been substantial advancement in antiandrogen therapies, resistance to these treatments remains a significant obstacle, often marked by continuous or enhanced AR signaling in resistant tumors. While the dysregulation of the ubiquitination-based protein degradation process is instrumental in the accumulation of oncogenic proteins, including AR, the molecular mechanism of ubiquitination-driven AR degradation remains largely undefined. We identified UBE2J1 as the critical E2 ubiquitin-conjugating enzyme responsible for guiding AR ubiquitination and eventual degradation. The absence of UBE2J1, found in 5-15% of PCa patients, results in disrupted AR ubiquitination and degradation. This disruption leads to an accumulation of AR proteins, promoting resistance to antiandrogen treatments. By employing a ubiquitination-based AR degrader to adeptly restore AR ubiquitination, we reestablished AR degradation and inhibited the proliferation of antiandrogen-resistant PCa tumors. These findings underscore the fundamental role of UBE2J1 in AR degradation and illuminate an uncharted mechanism through which PCa maintains heightened AR protein levels, fostering resistance to antiandrogen therapies.
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Affiliation(s)
| | - Choushi Wang
- Department of Molecular Biology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Xiaoling Li
- Department of Molecular Biology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Su Deng
- Department of Molecular Biology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Julisa Gonzalez
- Department of Molecular Biology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Nickolas A Johnson
- Department of Molecular Biology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Yaru Xu
- Department of Molecular Biology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Lauren A Metang
- Department of Molecular Biology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Medha Sundar Rajan
- Department of Molecular Biology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Yuqiu Yang
- Quantitative Biomedical Research Center, Peter O'Donnell Jr. School of Public Health, UT Southwestern Medical Center, Dallas, TX, USA
| | - Yi Yin
- Department of Urology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Mia Hofstad
- Department of Urology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Ganesh V Raj
- Department of Urology, UT Southwestern Medical Center, Dallas, TX, USA
- Harold C. Simmons Comprehensive Cancer Center, UT Southwestern Medical Center, Dallas, TX, USA
| | - Song Zhang
- Peter O'Donnell Jr. School of Public Health, UT Southwestern Medical Center, Dallas, TX, USA
| | - Andrew Lemoff
- Department of Biochemistry, UT Southwestern Medical Center, Dallas, TX, USA
| | - Wei He
- Accutar Biotechnology, Inc., Wilmington, DE, USA
| | - Jie Fan
- Accutar Biotechnology, Inc., Wilmington, DE, USA
| | - Yunguan Wang
- Division of Biomedical Informatics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
- Department of Pediatrics, University of Cincinnati, Cincinnati, OH, USA
| | - Tao Wang
- Quantitative Biomedical Research Center, Peter O'Donnell Jr. School of Public Health, UT Southwestern Medical Center, Dallas, TX, USA
- Harold C. Simmons Comprehensive Cancer Center, UT Southwestern Medical Center, Dallas, TX, USA
| | - Ping Mu
- Department of Molecular Biology, UT Southwestern Medical Center, Dallas, TX, USA.
- Harold C. Simmons Comprehensive Cancer Center, UT Southwestern Medical Center, Dallas, TX, USA.
- Hamon Center for Regenerative Science and Medicine, UT Southwestern Medical Center, Dallas, TX, USA.
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3
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Panda P, Sarohi V, Basak T, Kasturi P. Elucidation of Site-Specific Ubiquitination on Chaperones in Response to Mutant Huntingtin. Cell Mol Neurobiol 2023; 44:3. [PMID: 38102300 DOI: 10.1007/s10571-023-01446-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Accepted: 12/09/2023] [Indexed: 12/17/2023]
Abstract
Huntington's disease (HD) is one of the prominent neurodegenerative diseases, characterized by the progressive decline of neuronal function, due to the accumulation and aggregation of misfolded proteins. Pathological progression of HD is hallmarked by the aberrant aggregation of the huntingtin protein (HTT) and subsequent neurotoxicity. Molecular chaperones (heat shock proteins, HSPs) play a pivotal role in maintaining proteostasis by facilitating protein refolding, degradation, or sequestration to limit the accumulation of misfolded proteins during neurotoxicity. However, the role of post-translational modifications such as ubiquitination among HSPs during HD is less known. In this study, we aimed to elucidate HSPs ubiquitin code in the context of HD pathogenesis. In a comprehensive proteomic analysis, we identified site-specific ubiquitination events in HSPs associated with HTT in HD-affected brain regions. To assess the impact of ubiquitination on HSPs during HD, we quantified the abundance of ubiquitinated lysine sites in both the rat cortex/striatum and in the mouse primary cortical neurons. Strikingly, we observed highly tissue-specific alterations in the relative ubiquitination levels of HSPs under HD conditions, emphasizing the importance of spatial perturbed post-translational modifications (PTMs) in shaping disease pathology. These ubiquitination events, combined with other PTMs on HSPs, are likely to influence the phase transitions of HTT. In conclusion, our study uncovered differential site-specific ubiquitination of molecular chaperones and offers a comprehensive view of the intricate relationship between protein aggregation, and PTMs in the context of Huntington's disease.
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Affiliation(s)
- Prajnadipta Panda
- School of Biosciences and Bioengineering, Indian Institute of Technology Mandi, Kamand, Himachal Pradesh, 175005, India
| | - Vivek Sarohi
- School of Biosciences and Bioengineering, Indian Institute of Technology Mandi, Kamand, Himachal Pradesh, 175005, India
| | - Trayambak Basak
- School of Biosciences and Bioengineering, Indian Institute of Technology Mandi, Kamand, Himachal Pradesh, 175005, India.
| | - Prasad Kasturi
- School of Biosciences and Bioengineering, Indian Institute of Technology Mandi, Kamand, Himachal Pradesh, 175005, India.
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4
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Gonçalves D, Peffer S, Morano KA. Cytoplasmic redox imbalance in the thioredoxin system activates Hsf1 and results in hyperaccumulation of the sequestrase Hsp42 with misfolded proteins. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.26.546610. [PMID: 37425817 PMCID: PMC10327208 DOI: 10.1101/2023.06.26.546610] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/11/2023]
Abstract
Cells employ multiple systems to maintain homeostasis when experiencing environmental stress. For example, the folding of nascent polypeptides is exquisitely sensitive to proteotoxic stressors including heat, pH and oxidative stress, and is safeguarded by a network of protein chaperones that concentrate potentially toxic misfolded proteins into transient assemblies to promote folding or degradation. The redox environment itself is buffered by both cytosolic and organellar thioredoxin and glutathione pathways. How these systems are linked is poorly understood. Here, we determine that specific disruption of the cytosolic thioredoxin system resulted in constitutive activation of the heat shock response in Saccharomyces cerevisiae and accumulation of the sequestrase Hsp42 into an exaggerated and persistent juxtanuclear quality control (JUNQ) compartment. Terminally misfolded proteins also accumulated in this compartment in thioredoxin reductase (TRR1)-deficient cells, despite apparently normal formation and dissolution of transient cytoplasmic quality control (CytoQ) bodies during heat shock. Notably, cells lacking TRR1 and HSP42 exhibited severe synthetic slow growth exacerbated by oxidative stress, signifying a critical role for Hsp42 under redox-challenged conditions. Finally, we demonstrated that Hsp42 localization patterns in trr1∆ cells mimic those observed in chronically aging and glucose-starved cells, linking nutrient depletion and redox imbalance with management of misfolded proteins via a mechanism of long-term sequestration.
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Affiliation(s)
- Davi Gonçalves
- Department of Microbiology and Molecular Genetics, McGovern Medical School at UTHealth Houston, Houston, TX USA
- Current address: Cemvita Factory, Houston, TX USA
| | - Sara Peffer
- Department of Microbiology and Molecular Genetics, McGovern Medical School at UTHealth Houston, Houston, TX USA
- MD Anderson UTHealth Graduate School at UTHealth Houston, Houston, TX USA
- Current address: Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, TX USA
| | - Kevin A. Morano
- Department of Microbiology and Molecular Genetics, McGovern Medical School at UTHealth Houston, Houston, TX USA
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5
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An L, Gao H, Zhong Y, Liu Y, Cao Y, Yi J, Huang X, Wen C, Tong R, Pan Z, Yan X, Liu M, Wang S, Bai X, Wu H, Hu T. Molecular chaperones HSP40, HSP70, STIP1, and HSP90 are involved in stabilization of Cx43. Cytotechnology 2023; 75:207-217. [PMID: 37187948 PMCID: PMC10167082 DOI: 10.1007/s10616-023-00570-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Accepted: 01/10/2023] [Indexed: 02/05/2023] Open
Abstract
To investigate the involvement of stress induced phosphoprotein 1 (STIP1), heat shock protein (HSP) 70, and HSP90 in ubiquitination of connexin 43 (Cx43) in rat H9c2 cardiomyocytes. Co-immunoprecipitation was used to detect protein-protein interactions and Cx43 ubiquitination. Immunofluorescence was used for protein co-localization. The protein binding, Cx43 protein expression, and Cx43 ubiquitination were reanalyzed in H9c2 cells with modified STIP1 and/or HSP90 expression. STIP1 bound to HSP70 and HSP90, and Cx43 bound to HSP40, HSP70, and HSP90 in normal H9c2 cardiomyocytes. Overexpression of STIP1 promoted the transition of Cx43-HSP70 to Cx43-HSP90 and inhibited Cx43 ubiquitination; knockdown of STIP1 resulted in the opposite effects. Inhibition of HSP90 counteracted the inhibitory effect of STIP1 overexpression on Cx43 ubiquitination. STIP1 suppresses Cx43 ubiquitination in H9c2 cardiomyocytes by promoting the transition of Cx43-HSP70 to Cx43-HSP90.
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Affiliation(s)
- Li An
- Guizhou Medical University, Guiyang, 550004 Guizhou People’s Republic of China
- Department of Anesthesiology, The Affiliated Hospital of Guizhou Medical University, No. 28 Guiyi St, Yunyan District, Guiyang, 550004 Guizhou People’s Republic of China
- Translational Medicine Research Center of Guizhou Medical University, Guiyang, 550004 Guizhou People’s Republic of China
| | - Hong Gao
- Department of Anesthesiology, The Affiliated Hospital of Guizhou Medical University, No. 28 Guiyi St, Yunyan District, Guiyang, 550004 Guizhou People’s Republic of China
| | - Yi Zhong
- Department of Anesthesiology, The Affiliated Hospital of Guizhou Medical University, No. 28 Guiyi St, Yunyan District, Guiyang, 550004 Guizhou People’s Republic of China
| | - Yanqiu Liu
- Department of Anesthesiology, Guiyang Fourth People’s Hospital, Guiyang, 550002 Guizhou People’s Republic of China
| | - Ying Cao
- School of Anesthesiology, Guizhou Medical University, Guiyang, 550004 Guizhou People’s Republic of China
- Guiyang Second People’s Hospital, Guiyang, 550001 Guizhou People’s Republic of China
| | - Jing Yi
- Department of Anesthesiology, The Affiliated Hospital of Guizhou Medical University, No. 28 Guiyi St, Yunyan District, Guiyang, 550004 Guizhou People’s Republic of China
| | - Xiang Huang
- School of Anesthesiology, Guizhou Medical University, Guiyang, 550004 Guizhou People’s Republic of China
| | - Chunlei Wen
- Children’s Hospital of Guiyang Maternal and Child Health Hospital, Guiyang, 550001 Guizhou People’s Republic of China
| | - Rui Tong
- School of Anesthesiology, Guizhou Medical University, Guiyang, 550004 Guizhou People’s Republic of China
| | - Zhijun Pan
- School of Anesthesiology, Guizhou Medical University, Guiyang, 550004 Guizhou People’s Republic of China
| | - Xu Yan
- School of Anesthesiology, Guizhou Medical University, Guiyang, 550004 Guizhou People’s Republic of China
| | - Meiyan Liu
- School of Anesthesiology, Guizhou Medical University, Guiyang, 550004 Guizhou People’s Republic of China
| | - Shengzhao Wang
- School of Anesthesiology, Guizhou Medical University, Guiyang, 550004 Guizhou People’s Republic of China
| | - Xue Bai
- School of Anesthesiology, Guizhou Medical University, Guiyang, 550004 Guizhou People’s Republic of China
| | - Hao Wu
- School of Anesthesiology, Guizhou Medical University, Guiyang, 550004 Guizhou People’s Republic of China
| | - Tingju Hu
- School of Anesthesiology, Guizhou Medical University, Guiyang, 550004 Guizhou People’s Republic of China
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6
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Goel S, Oliva R, Jeganathan S, Bader V, Krause LJ, Kriegler S, Stender ID, Christine CW, Nakamura K, Hoffmann JE, Winter R, Tatzelt J, Winklhofer KF. Linear ubiquitination induces NEMO phase separation to activate NF-κB signaling. Life Sci Alliance 2023; 6:e202201607. [PMID: 36720498 PMCID: PMC9889916 DOI: 10.26508/lsa.202201607] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Revised: 01/09/2023] [Accepted: 01/09/2023] [Indexed: 02/02/2023] Open
Abstract
The NF-κB essential modulator NEMO is the core regulatory component of the inhibitor of κB kinase complex, which is a critical checkpoint in canonical NF-κB signaling downstream of innate and adaptive immune receptors. In response to various stimuli, such as TNF or IL-1β, NEMO binds to linear or M1-linked ubiquitin chains generated by LUBAC, promoting its oligomerization and subsequent activation of the associated kinases. Here we show that M1-ubiquitin chains induce phase separation of NEMO and the formation of NEMO assemblies in cells after exposure to IL-1β. Phase separation is promoted by both binding of NEMO to linear ubiquitin chains and covalent linkage of M1-ubiquitin to NEMO and is essential but not sufficient for its phase separation. Supporting the functional relevance of NEMO phase separation in signaling, a pathogenic NEMO mutant, which is impaired in both binding and linkage to linear ubiquitin chains, does not undergo phase separation and is defective in mediating IL-1β-induced NF-κB activation.
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Affiliation(s)
- Simran Goel
- Department Molecular Cell Biology, Institute of Biochemistry and Pathobiochemistry, Ruhr University Bochum, Bochum, Germany
| | - Rosario Oliva
- Physical Chemistry I-Biophysical Chemistry, Department of Chemistry and Chemical Biology, TU Dortmund University, Dortmund, Germany
- Department of Chemical Sciences, University of Naples Federico II, Naples, Italy
| | - Sadasivam Jeganathan
- Department Molecular Cell Biology, Institute of Biochemistry and Pathobiochemistry, Ruhr University Bochum, Bochum, Germany
| | - Verian Bader
- Department Molecular Cell Biology, Institute of Biochemistry and Pathobiochemistry, Ruhr University Bochum, Bochum, Germany
- Department Biochemistry of Neurodegenerative Diseases, Institute of Biochemistry and Pathobiochemistry, Ruhr University Bochum, Bochum, Germany
| | - Laura J Krause
- Department Molecular Cell Biology, Institute of Biochemistry and Pathobiochemistry, Ruhr University Bochum, Bochum, Germany
- RESOLV Cluster of Excellence, Ruhr University Bochum, Bochum, Germany
| | - Simon Kriegler
- Physical Chemistry I-Biophysical Chemistry, Department of Chemistry and Chemical Biology, TU Dortmund University, Dortmund, Germany
| | - Isabelle D Stender
- Protein Chemistry Facility, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | | | - Ken Nakamura
- Department of Neurology, UCSF, San Francisco, CA, USA
- Gladstone Institute of Neurological Disease, Gladstone Institutes, San Francisco, CA, USA
| | - Jan-Erik Hoffmann
- Protein Chemistry Facility, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Roland Winter
- Physical Chemistry I-Biophysical Chemistry, Department of Chemistry and Chemical Biology, TU Dortmund University, Dortmund, Germany
- RESOLV Cluster of Excellence, Ruhr University Bochum, Bochum, Germany
| | - Jörg Tatzelt
- RESOLV Cluster of Excellence, Ruhr University Bochum, Bochum, Germany
- Department Biochemistry of Neurodegenerative Diseases, Institute of Biochemistry and Pathobiochemistry, Ruhr University Bochum, Bochum, Germany
| | - Konstanze F Winklhofer
- Department Molecular Cell Biology, Institute of Biochemistry and Pathobiochemistry, Ruhr University Bochum, Bochum, Germany
- RESOLV Cluster of Excellence, Ruhr University Bochum, Bochum, Germany
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7
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Gao Y, Zhu Y, Sun Q, Chen D. Argonaute-dependent ribosome-associated protein quality control. Trends Cell Biol 2023; 33:260-272. [PMID: 35981909 DOI: 10.1016/j.tcb.2022.07.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Revised: 07/19/2022] [Accepted: 07/25/2022] [Indexed: 11/17/2022]
Abstract
Ribosome-associated protein quality control (RQC) is a protein surveillance mechanism that eliminates defective nascent polypeptides. The E3 ubiquitin ligase, Ltn1, is a key regulator of RQC that targets substrates for ubiquitination. Argonaute proteins (AGOs) are central players in miRNA-mediated gene silencing and have recently been shown to also regulate RQC by facilitating Ltn1. Therefore, AGOs directly coordinate post-transcriptional gene silencing and RQC, ensuring efficient gene silencing. We summarize the principles of RQC and the functions of AGOs in miRNA-mediated gene silencing, and discuss how AGOs associate with the endoplasmic reticulum (ER) to assist Ltn1 in controlling RQC. We highlight that RQC not only eliminates defective nascent polypeptides but also removes unwanted protein products when AGOs participate.
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Affiliation(s)
- Yajie Gao
- Institute of Biomedical Research, Yunnan University, Kunming 650500, China
| | - Yuanxiang Zhu
- Institute of Biomedical Research, Yunnan University, Kunming 650500, China
| | - Qinmiao Sun
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; Institute of Stem Cells and Regeneration, Chinese Academy of Sciences, Beijing 100101, China.
| | - Dahua Chen
- Institute of Biomedical Research, Yunnan University, Kunming 650500, China.
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8
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Abstract
The combination of large-scale protein separation techniques, sophisticated mass spectrometry, and systems bioinformatics has led to the establishment of proteomics as a distinct discipline within the wider field of protein biochemistry. Both discovery proteomics and targeted proteomics are widely used in biological and biomedical research, whereby the analytical approaches can be broadly divided into proteoform-centric top-down proteomics versus peptide-centric bottom-up proteomics. This chapter outlines the scientific value of top-down proteomics and describes how fluorescence two-dimensional difference gel electrophoresis can be combined with the systematic analysis of crucial post-translational modifications. The concept of on-membrane digestion following the electrophoretic transfer of proteins and the usefulness of comparative two-dimensional immunoblotting are discussed.
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Affiliation(s)
- Kay Ohlendieck
- Department of Biology, Maynooth University, National University of Ireland, Maynooth, Co. Kildare, Ireland.
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9
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Modulating the Ubiquitin–Proteasome System: A Therapeutic Strategy for Autoimmune Diseases. Cells 2022; 11:cells11071093. [PMID: 35406655 PMCID: PMC8997991 DOI: 10.3390/cells11071093] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Revised: 03/20/2022] [Accepted: 03/22/2022] [Indexed: 12/12/2022] Open
Abstract
Multiple sclerosis (MS) is an autoimmune, neurodegenerative disease associated with the central nervous system (CNS). Autoimmunity is caused by an abnormal immune response to self-antigens, which results in chronic inflammation and tissue death. Ubiquitination is a post-translational modification in which ubiquitin molecules are attached to proteins by ubiquitinating enzymes, and then the modified proteins are degraded by the proteasome system. In addition to regulating proteasomal degradation of proteins, ubiquitination also regulates other cellular functions that are independent of proteasomal degradation. It plays a vital role in intracellular protein turnover and immune signaling and responses. The ubiquitin–proteasome system (UPS) is primarily responsible for the nonlysosomal proteolysis of intracellular proteins. The 26S proteasome is a multicatalytic adenosine-triphosphate-dependent protease that recognizes ubiquitin covalently attached to particular proteins and targets them for degradation. Damaged, oxidized, or misfolded proteins, as well as regulatory proteins that govern many essential cellular functions, are removed by this degradation pathway. When this system is affected, cellular homeostasis is altered, resulting in the induction of a range of diseases. This review discusses the biochemistry and molecular biology of the UPS, including its role in the development of MS and proteinopathies. Potential therapies and targets involving the UPS are also addressed.
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10
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The San1 Ubiquitin Ligase Avidly Recognizes Misfolded Proteins through Multiple Substrate Binding Sites. Biomolecules 2021; 11:biom11111619. [PMID: 34827617 PMCID: PMC8615460 DOI: 10.3390/biom11111619] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Revised: 10/28/2021] [Accepted: 10/29/2021] [Indexed: 02/06/2023] Open
Abstract
Cellular homeostasis depends on robust protein quality control (PQC) pathways that discern misfolded proteins from functional ones in the cell. One major branch of PQC involves the controlled degradation of misfolded proteins by the ubiquitin-proteasome system. Here ubiquitin ligases must recognize and bind to misfolded proteins with sufficient energy to form a complex and with an adequate half-life to achieve poly-ubiquitin chain formation, the signal for protein degradation, prior to its dissociation from the ligase. It is not well understood how PQC ubiquitin ligases accomplish these tasks. Employing a fully reconstituted enzyme and substrate system to perform quantitative biochemical experiments, we demonstrate that the yeast PQC ubiquitin ligase San1 contains multiple substrate binding sites along its polypeptide chain that appear to display specificity for unique misfolded proteins. The results are consistent with a model where these substrate binding sites enable San1 to bind to misfolded substrates avidly, resulting in high affinity ubiquitin ligase-substrate complexes.
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