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Loy CA, Trader DJ. Primed for Interactions: Investigating the Primed Substrate Channel of the Proteasome for Improved Molecular Engagement. Molecules 2024; 29:3356. [PMID: 39064934 DOI: 10.3390/molecules29143356] [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: 05/30/2024] [Revised: 07/09/2024] [Accepted: 07/10/2024] [Indexed: 07/28/2024] Open
Abstract
Protein homeostasis is a tightly conserved process that is regulated through the ubiquitin proteasome system (UPS) in a ubiquitin-independent or ubiquitin-dependent manner. Over the past two decades, the proteasome has become an excellent therapeutic target through inhibition of the catalytic core particle, inhibition of subunits responsible for recognizing and binding ubiquitinated proteins, and more recently, through targeted protein degradation using proteolysis targeting chimeras (PROTACs). The majority of the developed inhibitors of the proteasome's core particle rely on gaining selectivity through binding interactions within the unprimed substrate channel. Although this has allowed for selective inhibitors and chemical probes to be generated for the different proteasome isoforms, much remains unknown about the interactions that could be harnessed within the primed substrate channel to increase potency or selectivity. Herein, we discuss small molecules that interact with the primed substrate pocket and how their differences may give rise to altered activity. Taking advantage of additional interactions with the primed substrate pocket of the proteasome could allow for the generation of improved chemical tools for perturbing or monitoring proteasome activity.
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Affiliation(s)
- Cody A Loy
- Department of Pharmaceutical Sciences, University of California, Irvine, CA 92617, USA
| | - Darci J Trader
- Department of Pharmaceutical Sciences, University of California, Irvine, CA 92617, USA
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2
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Fan Y, Liu W, Qi L, Zhao Q, Li S, Zou H, Kong C, Li Z, Ren J, Liu Z, Wang B. Correlation of disulfidptosis and periodontitis: New insights and clinical significance. Arch Oral Biol 2024; 166:106046. [PMID: 38991331 DOI: 10.1016/j.archoralbio.2024.106046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Revised: 06/24/2024] [Accepted: 06/28/2024] [Indexed: 07/13/2024]
Abstract
OBJECTIVES This study aims to investigate and predict the therapeutic agents associated with disulfidptosis in periodontitis. DESIGN The dataset GSE10334 was downloaded from the Gene Expression Omnibus (GEO) database and used to train a least absolute shrinkage and selection operator (LASSO) regression and support vector machine recursive feature elimination (SVM-RFE) algorithm to identify genes associated with disulfidptosis in periodontitis. GSE16134 validation sets, polymerase chain reaction (PCR), and gingival immunofluorescence were used to verify the results.Single-gene Gene Set Enrichment Analysis (GSEA) was performed to explore the potential mechanisms and functions of the characterized genes. Immune infiltration and correlation analyses were performed, and competing endogenous RNA (ceRNA) networks were constructed. Effective therapeutic drugs were then predicted using the DGIdb database, and molecular docking was used to validate binding affinity. RESULTS Six genes (SLC7A11, SLC3A2, RPN1, NCKAP1, LRPPRC, and NDUFS1) associated with disulfidptosis in periodontitis were obtained. Validation results from external datasets and experiments were consistent with the screening results. Single-gene GSEA analysis was mainly enriched for antigen presentation and immune-related pathways and functions.Immune infiltration and correlation analyses revealed significant regulatory relationships between these genes and plasma cells, resting dendritic cell, and activated NK cells. The ceRNA network was visualized. And ME-344, NV-128, and RILUZOLE, which have good affinity to target genes, were identified as promising agents for the treatment of periodontitis. CONCLUSIONS SLC7A11, SLC3A2, RPN1, NCKAP1, LRPPRC, and NDUFS1 are targets associated with disulfidptosis in periodontitis, and ME-344, NV-128, and RILUZOLE are promising agents for the treatment of periodontitis.
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Affiliation(s)
- Yixin Fan
- Hospital of Stomatology, Jilin University, Changchun, China.
| | - Wantong Liu
- Hospital of Stomatology, Jilin University, Changchun, China.
| | - Le Qi
- Hospital of Stomatology, Jilin University, Changchun, China.
| | - Qi Zhao
- Hospital of Stomatology, Jilin University, Changchun, China.
| | - Sining Li
- Hospital of Stomatology, Jilin University, Changchun, China.
| | - He Zou
- Hospital of Stomatology, Jilin University, Changchun, China.
| | - Chen Kong
- Hospital of Stomatology, Jilin University, Changchun, China.
| | - Zhiwei Li
- Hospital of Stomatology, Jilin University, Changchun, China.
| | - Jiwei Ren
- Hospital of Stomatology, Jilin University, Changchun, China.
| | - Zhihui Liu
- Hospital of Stomatology, Jilin University, Changchun, China.
| | - Bowei Wang
- The Second Hospital of Jilin University, Jilin University, Changchun, China.
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Wang Y, Zhang S, Zhao Z, Jin Q, Wang Z, Song Z, Liu L, Zhao Z. PSMC2 promotes glioma progression by regulating immune microenvironment and PI3K/AKT/mTOR pathway. Immunobiology 2024; 229:152802. [PMID: 38569452 DOI: 10.1016/j.imbio.2024.152802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2023] [Revised: 03/25/2024] [Accepted: 03/29/2024] [Indexed: 04/05/2024]
Abstract
BACKGROUND Glioma, the most frequent and malignant central nervous system (CNS) cancer, has a bad outcome. Proteasome 26S subunit ATPase 2 (PSMC2) is an essential part of the 26S proteasome and promotes the development of several tumors. However, the pathway and function of PSMC2 in glioma have not been unelucidated. METHODS This study analyzed PSMC2 expression in glioma tissues and its predictive significance for patients. We examined the link between PSMC2 and DNA methylation, immune cell infiltration, tumor immune cycle, immune cell homeostasis, and immune checkpoints. Subsequently, immunohistochemistry and in vitro trials were employed to validate the expression, prognostic potential, and function of PSMC2 in glioma. The mechanisms of PSMC2 in glioma were further explored. RESULTS Our study revealed that PSMC2 expression increased in glioma tissues contrasted with healthy tissues, and patients with high PSMC2 glioma exhibited poor overall survival (OS) compared to the low-PSMC2 group. Immune profile analysis revealed that PSMC2 was positively related to immunosuppressive cell infiltration and immune checkpoints and adversely related to the cancer immune cycle and immune cell homeostasis. In cell-based investigations, the inhibition of PSMC2 was found to effectively suppress the aggressiveness and proliferation of glioma cell lines while also enhancing cell cycle arrest and promoting cell death. Gene Set Enrichment Analysis (GSEA), Gene Set Variation Analysis (GSVA), and in vitro experiments showed that PSMC2 promoted glioma development through the PI3K/AKT/mTOR pathway. CONCLUSIONS PSMC2 was upregulated in glioma and promoted cancer progression by modulating the tumor immune microenvironment, cancer cell biological behavior, immune cell homeostasis, and the PI3K/AKT/mTOR pathway, providing a new option to treat glioma.
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Affiliation(s)
- Yizheng Wang
- Pain Rehabilitation, The Fourth Hospital of Hebei Medical University, Shijiazhuang 050000, China
| | - Shiyang Zhang
- Department of Neurosurgery, The Second Hospital of Hebei Medical University, Shijiazhuang 050000, China
| | - Zijun Zhao
- Spine Center, Sanbo Brain Hospital, Capital Medical University, Beijing 100000, China
| | - Qianxu Jin
- Department of Neurosurgery, The Fourth Hospital of Hebei Medical University, Shijiazhuang 050000, China
| | - Zairan Wang
- Department of Neurosurgery, Peking Union Medical College Hospital, Beijing 100000, China
| | - Zihan Song
- Department of Neurosurgery, The Second Hospital of Hebei Medical University, Shijiazhuang 050000, China
| | - Liqiang Liu
- Department of Neurosurgery, The Second Hospital of Hebei Medical University, Shijiazhuang 050000, China.
| | - Zongmao Zhao
- Department of Neurosurgery, The Fourth Hospital of Hebei Medical University, Shijiazhuang 050000, China.
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Cascio P. PA28γ, the ring that makes tumors invisible to the immune system? Biochimie 2024:S0300-9084(24)00078-6. [PMID: 38631454 DOI: 10.1016/j.biochi.2024.04.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2024] [Revised: 03/29/2024] [Accepted: 04/12/2024] [Indexed: 04/19/2024]
Abstract
PA28γ is a proteasomal interactor whose main and most known function is to stimulate the hydrolytic activity of the 20 S proteasome independently of ubiquitin and ATP. Unlike its two paralogues, PA28α and PA28β, PA28γ is largely present in the nuclear compartment and plays pivotal functions in important pathways such as cellular division, apoptosis, neoplastic transformation, chromatin structure and organization, fertility, lipid metabolism, and DNA repair mechanisms. Although it is known that a substantial fraction of PA28γ is found in the cell in a free form (i.e. not associated with 20 S), almost all of the studies so far have focused on its ability to modulate proteasomal enzymatic activities. In this respect, the ability of PA28γ to strongly stimulate degradation of proteins, especially if intrinsically disordered and therefore devoid of three-dimensional tightly folded structure, appears to be the main molecular mechanism underlying its multiple biological effects. Initial studies, conducted more than 20 years ago, came to the conclusion that among the many biological functions of PA28γ, the immunological ones were rather limited and circumscribed. In this review, we focus on recent evidence showing that PA28γ fulfills significant functions in cell-mediated acquired immunity, with a particular role in attenuating MHC class I antigen presentation, especially in relation to neoplastic transformation and autoimmune diseases.
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Affiliation(s)
- Paolo Cascio
- Department of Veterinary Sciences, University of Turin, Largo P. Braccini 2, 10095, Grugliasco, Turin, Italy.
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5
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Li H, Ji Z, Paulo JA, Gygi SP, Rapoport TA. Bidirectional substrate shuttling between the 26S proteasome and the Cdc48 ATPase promotes protein degradation. Mol Cell 2024; 84:1290-1303.e7. [PMID: 38401542 DOI: 10.1016/j.molcel.2024.01.029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 12/12/2023] [Accepted: 01/31/2024] [Indexed: 02/26/2024]
Abstract
Most eukaryotic proteins are degraded by the 26S proteasome after modification with a polyubiquitin chain. Substrates lacking unstructured segments cannot be degraded directly and require prior unfolding by the Cdc48 ATPase (p97 or VCP in mammals) in complex with its ubiquitin-binding partner Ufd1-Npl4 (UN). Here, we use purified yeast components to reconstitute Cdc48-dependent degradation of well-folded model substrates by the proteasome. We show that a minimal system consists of the 26S proteasome, the Cdc48-UN ATPase complex, the proteasome cofactor Rad23, and the Cdc48 cofactors Ubx5 and Shp1. Rad23 and Ubx5 stimulate polyubiquitin binding to the 26S proteasome and the Cdc48-UN complex, respectively, allowing these machines to compete for substrates before and after their unfolding. Shp1 stimulates protein unfolding by the Cdc48-UN complex rather than substrate recruitment. Experiments in yeast cells confirm that many proteins undergo bidirectional substrate shuttling between the 26S proteasome and Cdc48 ATPase before being degraded.
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Affiliation(s)
- Hao Li
- Howard Hughes Medical Institute and Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA
| | - Zhejian Ji
- Howard Hughes Medical Institute and Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA
| | - Joao A Paulo
- Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA
| | - Steven P Gygi
- Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA
| | - Tom A Rapoport
- Howard Hughes Medical Institute and Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA.
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6
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Cao H, Zhou X, Xu B, Hu H, Guo J, Ma Y, Wang M, Li N, Jun Z. Advances in the study of protein folding and endoplasmic reticulum-associated degradation in mammal cells. J Zhejiang Univ Sci B 2024; 25:212-232. [PMID: 38453636 PMCID: PMC10918413 DOI: 10.1631/jzus.b2300403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2023] [Accepted: 08/03/2023] [Indexed: 03/09/2024]
Abstract
The endoplasmic reticulum is a key site for protein production and quality control. More than one-third of proteins are synthesized and folded into the correct three-dimensional conformation in the endoplasmic reticulum. However, during protein folding, unfolded and/or misfolded proteins are prone to occur, which may lead to endoplasmic reticulum stress. Organisms can monitor the quality of the proteins produced by endoplasmic reticulum quality control (ERQC) and endoplasmic reticulum-associated degradation (ERAD), which maintain endoplasmic reticulum protein homeostasis by degrading abnormally folded proteins. The underlying mechanisms of protein folding and ERAD in mammals have not yet been fully explored. Therefore, this paper reviews the process and function of protein folding and ERAD in mammalian cells, in order to help clinicians better understand the mechanism of ERAD and to provide a scientific reference for the treatment of diseases caused by abnormal ERAD.
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Affiliation(s)
- Hong Cao
- Department of Sport Rehabilitation, Shanghai University of Sport, Shanghai 200438, China
- National Key Laboratory of Immunity and Inflammation, Naval Medical University, Shanghai 200433, China
| | - Xuchang Zhou
- Department of Sport Rehabilitation, Shanghai University of Sport, Shanghai 200438, China
| | - Bowen Xu
- National Key Laboratory of Immunity and Inflammation, Naval Medical University, Shanghai 200433, China
| | - Han Hu
- National Key Laboratory of Immunity and Inflammation, Naval Medical University, Shanghai 200433, China
| | - Jianming Guo
- Department of Sport Rehabilitation, Shanghai University of Sport, Shanghai 200438, China
| | - Yuwei Ma
- Department of Sport Rehabilitation, Shanghai University of Sport, Shanghai 200438, China
| | - Miao Wang
- Department of Sport Rehabilitation, Shanghai University of Sport, Shanghai 200438, China
| | - Nan Li
- National Key Laboratory of Immunity and Inflammation, Naval Medical University, Shanghai 200433, China.
| | - Zou Jun
- Department of Sport Rehabilitation, Shanghai University of Sport, Shanghai 200438, China.
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Feng L, Zhang N, Luo L, Liu J, Yao Y, Gao MS, Pan J, He C. Investigation of the Proteasome 26S Subunit, ATPase Family Genes as Potential Prognostic Biomarkers and Therapeutic Targets for Hepatocellular Carcinoma. Cancer Manag Res 2024; 16:95-111. [PMID: 38370535 PMCID: PMC10874222 DOI: 10.2147/cmar.s449488] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Accepted: 02/09/2024] [Indexed: 02/20/2024] Open
Abstract
Background Several studies suggest that Proteasome 26S Subunit, ATPase (PSMC) family genes are of great importance in tumor progression and spreading, but the study for systematic evaluation of the function of PSMC genes in hepatocellular carcinoma (HCC) is currently lacking. Methods The functions of PSMC genes in HCC were analyzed using multiple online databases, including the TCGA database, GEO database, HPA database, cBioPortal database, DAVID, and KEGG pathway. Experiments were later conducted to verify PSMC expression. Results High levels of PSMC gene expression were detected in HCC tissues and PSMCs exhibited potentially powerful abilities in diagnosing HCC patients. All PSMC proteins are expressed to varying degrees in HCC tissues and high expression of the PSMC genes lead to poor prognosis in patients with HCC. Moreover, DNA methylation involves the regulation of the expression of PSMC2 and PSMC5 in HCC, and the levels of methylation of PSMC2 or PSMC5 correlate positively with patient overall survival in HCC patients. The copy number alteration and mutation of PSMC genes were observed and related to the expression of PSMCs in HCC. Functional enrichment analysis showed that many highly co-expressed genes of PSMCs had a potential role in tumor progression and metastasis, which merited further in-depth study. Functional network analysis also suggests that the primary biological function of PSMC genes is the regulation of protein homeostasis and energy metabolism in HCC. Moreover, the expression levels of PSMCs are related to immune cell infiltrates and immunomodulatory factors in HCC. Conclusion Our study indicates that PSMC genes are the potential target for precision immunotherapy and novel prognostic biomarkers for HCC.
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Affiliation(s)
- Lei Feng
- The Division of Gastroenterology and Hepatology, Suining Central Hospital, Suining City, Sichuan Province, People’s Republic of China
| | - Ning Zhang
- The Division of Gastroenterology and Hepatology, Suining Central Hospital, Suining City, Sichuan Province, People’s Republic of China
| | - Lan Luo
- The Division of Gastroenterology and Hepatology, Suining Central Hospital, Suining City, Sichuan Province, People’s Republic of China
| | - Jie Liu
- The Division of Gastroenterology and Hepatology, Suining Central Hospital, Suining City, Sichuan Province, People’s Republic of China
| | - Yong Yao
- The Division of Gastroenterology and Hepatology, Suining Central Hospital, Suining City, Sichuan Province, People’s Republic of China
| | - Ming-Sheng Gao
- The Division of Gastroenterology and Hepatology, Suining Central Hospital, Suining City, Sichuan Province, People’s Republic of China
| | - Jin Pan
- The Division of Gastroenterology and Hepatology, Suining Central Hospital, Suining City, Sichuan Province, People’s Republic of China
| | - Cai He
- The Division of Gastroenterology and Hepatology, Yibin Second People’s Hospital, Yibin City, Sichuan Province, People’s Republic of China
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8
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Li H, Ji Z, Paulo JA, Gygi SP, Rapoport TA. Bidirectional substrate shuttling between the 26S proteasome and the Cdc48 ATPase promotes protein degradation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.20.572403. [PMID: 38187576 PMCID: PMC10769200 DOI: 10.1101/2023.12.20.572403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2024]
Abstract
Most eukaryotic proteins are degraded by the 26S proteasome after modification with a polyubiquitin chain. Substrates lacking unstructured segments cannot be degraded directly and require prior unfolding by the Cdc48 ATPase (p97 or VCP in mammals) in complex with its ubiquitin-binding partner Ufd1-Npl4 (UN). Here, we use purified yeast components to reconstitute Cdc48-dependent degradation of well-folded model substrates by the proteasome. We show that a minimal system consists of the 26S proteasome, the Cdc48-UN ATPase complex, the proteasome cofactor Rad23, and the Cdc48 cofactors Ubx5 and Shp1. Rad23 and Ubx5 stimulate polyubiquitin binding to the 26S proteasome and the Cdc48-UN complex, respectively, allowing these machines to compete for substrates before and after their unfolding. Shp1 stimulates protein unfolding by the Cdc48-UN complex, rather than substrate recruitment. In vivo experiments confirm that many proteins undergo bidirectional substrate shuttling between the 26S proteasome and Cdc48 ATPase before being degraded.
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9
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Liu Q, Maqbool A, Mirkin FG, Singh Y, Stevenson CEM, Lawson DM, Kamoun S, Huang W, Hogenhout SA. Bimodular architecture of bacterial effector SAP05 that drives ubiquitin-independent targeted protein degradation. Proc Natl Acad Sci U S A 2023; 120:e2310664120. [PMID: 38039272 DOI: 10.1073/pnas.2310664120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Accepted: 10/19/2023] [Indexed: 12/03/2023] Open
Abstract
In eukaryotes, targeted protein degradation (TPD) typically depends on a series of interactions among ubiquitin ligases that transfer ubiquitin molecules to substrates leading to degradation by the 26S proteasome. We previously identified that the bacterial effector protein SAP05 mediates ubiquitin-independent TPD. SAP05 forms a ternary complex via interactions with the von Willebrand Factor Type A (vWA) domain of the proteasomal ubiquitin receptor Rpn10 and the zinc-finger (ZnF) domains of the SQUAMOSA-PROMOTER BINDING PROTEIN-LIKE (SPL) and GATA BINDING FACTOR (GATA) transcription factors (TFs). This leads to direct TPD of the TFs by the 26S proteasome. Here, we report the crystal structures of the SAP05-Rpn10vWA complex at 2.17 Å resolution and of the SAP05-SPL5ZnF complex at 2.20 Å resolution. Structural analyses revealed that SAP05 displays a remarkable bimodular architecture with two distinct nonoverlapping surfaces, a "loop surface" with three protruding loops that form electrostatic interactions with ZnF, and a "sheet surface" featuring two β-sheets, loops, and α-helices that establish polar interactions with vWA. SAP05 binding to ZnF TFs involves single amino acids responsible for multiple contacts, while SAP05 binding to vWA is more stable due to the necessity of multiple mutations to break the interaction. In addition, positioning of the SAP05 complex on the 26S proteasome points to a mechanism of protein degradation. Collectively, our findings demonstrate how a small bacterial bimodular protein can bypass the canonical ubiquitin-proteasome proteolysis pathway, enabling ubiquitin-independent TPD in eukaryotic cells. This knowledge holds significant potential for the creation of TPD technologies.
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Affiliation(s)
- Qun Liu
- Department of Crop Genetics, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom
| | - Abbas Maqbool
- Department of Biochemistry and Metabolism, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom
- The Sainsbury Laboratory, University of East Anglia, Norwich NR4 7UH, United Kingdom
| | - Federico G Mirkin
- Department of Crop Genetics, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom
| | - Yeshveer Singh
- Department of Crop Genetics, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom
| | - Clare E M Stevenson
- Department of Biochemistry and Metabolism, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom
| | - David M Lawson
- Department of Biochemistry and Metabolism, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom
| | - Sophien Kamoun
- The Sainsbury Laboratory, University of East Anglia, Norwich NR4 7UH, United Kingdom
| | - Weijie Huang
- National Key Laboratory of Plant Molecular Genetics, Shanghai Centre for Plant Stress Biology, Centre for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai 20032, China
| | - Saskia A Hogenhout
- Department of Crop Genetics, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom
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Anthony AJ, Gautam AKS, Miller LM, Ma Y, Hardwick AG, Sharma A, Ghatak S, Matouschek A, Jarrold MF, Clemmer DE. CDMS Analysis of Intact 19S, 20S, 26S, and 30S Proteasomes: Evidence for Higher-Order 20S Assemblies at a Low pH†. Anal Chem 2023; 95:12209-12215. [PMID: 37552619 PMCID: PMC10916762 DOI: 10.1021/acs.analchem.3c00472] [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] [Indexed: 08/10/2023]
Abstract
Charge detection mass spectrometry (CDMS) was examined as a means of studying proteasomes. To this end, the following masses of the 20S, 19S, 26S, and 30S proteasomes from Saccharomyces cerevisiae (budding yeast) were measured: m(20S) = 738.8 ± 2.9 kDa, m(19S) = 926.2 ± 4.8 kDa, m(26S) = 1,637.0 ± 7.6 kDa, and m(30S) = 2,534.2 ± 10.8 kDa. Under some conditions, larger (20S)x (where x = 1 to ∼13) assemblies are observed; the 19S regulatory particle also oligomerizes, but to a lesser extent, forming (19S)x complexes (where x = 1 to 4, favoring the x = 3 trimer). The (20S)x oligomers are favored in vitro, as the pH of the solution is lowered (from 7.0 to 5.4, in a 20 mM ammonium acetate solution) and may be related to in vivo proteasome storage granules that are observed under carbon starvation. From measurements of m(20S)x (x = 1 to ∼13) species, it appears that each multimer retains all 28 proteins of the 20S complex subunit. Several types of structures that might explain the formation of (20S)x assemblies are considered. We stress that each structural type [hypothetical planar, raft-like geometries (where individual proteasomes associate through side-by-side interactions); elongated, rodlike geometries (where subunits are bound end-to-end); and geometries that are roughly spherical (arising from aggregation through nonspecific subunit interactions)] is highly speculative but still interesting to consider, and a short discussion is provided. The utility of CDMS for characterizing proteasomes and related oligomers is discussed.
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Affiliation(s)
- Adam J Anthony
- Department of Chemistry, Indiana University, Bloomington, Indiana 47401, United States
| | - Amit K S Gautam
- Department of Molecular Biosciences, University of Texas, Austin Texas 78712, United States
| | - Lohra M Miller
- Department of Chemistry, Indiana University, Bloomington, Indiana 47401, United States
| | - Yiran Ma
- Department of Chemistry, Indiana University, Bloomington, Indiana 47401, United States
| | - Anya G Hardwick
- Department of Chemistry, Indiana University, Bloomington, Indiana 47401, United States
| | - Anu Sharma
- Indiana Center for Regenerative Medicine & Engineering, Department of Surgery, Indiana University School of Medicine, Indianapolis, Indiana 46202, United States
| | - Subhadip Ghatak
- Indiana Center for Regenerative Medicine & Engineering, Department of Surgery, Indiana University School of Medicine, Indianapolis, Indiana 46202, United States
| | - Andreas Matouschek
- Department of Molecular Biosciences, University of Texas, Austin Texas 78712, United States
| | - Martin F Jarrold
- Department of Chemistry, Indiana University, Bloomington, Indiana 47401, United States
| | - David E Clemmer
- Department of Chemistry, Indiana University, Bloomington, Indiana 47401, United States
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Davis C, Spaller BL, Choi E, Kurrasch J, Chong H, Elsasser S, Finley D, Matouschek A. A strict requirement in proteasome substrates for spacing between ubiquitin tag and degradation initiation elements. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.08.552540. [PMID: 37609285 PMCID: PMC10441315 DOI: 10.1101/2023.08.08.552540] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/24/2023]
Abstract
Proteins are typically targeted to the proteasome for degradation through the attachment of ubiquitin chains and the proteasome initiates degradation at a disordered region within the target protein. Yet some proteins with ubiquitin chains and disordered regions escape degradation. Here we investigate how the position of the ubiquitin chain on the target protein relative to the disordered region modulates degradation and show that the distance between the two determines whether a protein is degraded efficiently. This distance depends on the type of the degradation tag and is likely a result of the separation on the proteasome between the receptor that binds the tag and the site that engages the disordered region.
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12
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Tychhon B, Allen JC, Gonzalez MA, Olivas IM, Solecki JP, Keivan M, Velazquez VV, McCall EB, Tapia DN, Rubio AJ, Jordan C, Elliott D, Eiring AM. The prognostic value of 19S ATPase proteasome subunits in acute myeloid leukemia and other forms of cancer. Front Med (Lausanne) 2023; 10:1209425. [PMID: 37502358 PMCID: PMC10371016 DOI: 10.3389/fmed.2023.1209425] [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: 04/21/2023] [Accepted: 06/05/2023] [Indexed: 07/29/2023] Open
Abstract
Introduction The ubiquitin-proteasome system (UPS) is an intracellular organelle responsible for targeted protein degradation, which represents a standard therapeutic target for many different human malignancies. Bortezomib, a reversible inhibitor of chymotrypsin-like proteasome activity, was first approved by the FDA in 2003 to treat multiple myeloma and is now used to treat a number of different cancers, including relapsed mantle cell lymphoma, diffuse large B-cell lymphoma, colorectal cancer, and thyroid carcinoma. Despite the success, bortezomib and other proteasome inhibitors are subject to severe side effects, and ultimately, drug resistance. We recently reported an oncogenic role for non-ATPase members of the 19S proteasome in chronic myeloid leukemia (CML), acute myeloid leukemia (AML), and several different solid tumors. In the present study, we hypothesized that ATPase members of the 19S proteasome would also serve as biomarkers and putative therapeutic targets in AML and multiple other cancers. Methods We used data from The Cancer Genome Atlas (TCGA) and the Clinical Proteomic Tumor Analysis Consortium (CPTAC) available at UALCAN and/or GEPIA2 to assess the expression and prognostic value of proteasome 26S subunit, ATPases 1-6 (PSMC1-6) of the 19S proteasome in cancer. UALCAN was also used to associate PSMC1-6 mRNA expression with distinct clinicopathological features. Finally, cBioPortal was employed to assess genomic alterations of PSMC genes across different cancer types. Results The mRNA and protein expression of PSMC1-6 of the 19S proteasome were elevated in several cancers compared with normal controls, which often correlated with worse overall survival. In contrast, AML patients demonstrated reduced expression of these proteasome subunits compared with normal mononuclear cells. However, AML patients with high expression of PSMC2-5 had worse outcomes. Discussion Altogether, our data suggest that components of the 19S proteasome could serve as prognostic biomarkers and novel therapeutic targets in AML and several other human malignancies.
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Affiliation(s)
- Boranai Tychhon
- Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center at El Paso, El Paso, TX, United States
| | - Jesse C. Allen
- Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center at El Paso, El Paso, TX, United States
| | - Mayra A. Gonzalez
- Center of Emphasis in Cancer, Department of Molecular and Translational Medicine, Texas Tech University Health Sciences Center at El Paso, El Paso, TX, United States
| | - Idaly M. Olivas
- Center of Emphasis in Cancer, Department of Molecular and Translational Medicine, Texas Tech University Health Sciences Center at El Paso, El Paso, TX, United States
| | - Jonathan P. Solecki
- L. Frederick Francis Graduate School of Biomedical Sciences, Texas Tech University Health Sciences Center at El Paso, El Paso, TX, United States
| | - Mehrshad Keivan
- L. Frederick Francis Graduate School of Biomedical Sciences, Texas Tech University Health Sciences Center at El Paso, El Paso, TX, United States
| | - Vanessa V. Velazquez
- Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center at El Paso, El Paso, TX, United States
| | - Emily B. McCall
- Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center at El Paso, El Paso, TX, United States
| | - Desiree N. Tapia
- Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center at El Paso, El Paso, TX, United States
| | - Andres J. Rubio
- Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center at El Paso, El Paso, TX, United States
| | - Connor Jordan
- L. Frederick Francis Graduate School of Biomedical Sciences, Texas Tech University Health Sciences Center at El Paso, El Paso, TX, United States
| | - David Elliott
- Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center at El Paso, El Paso, TX, United States
| | - Anna M. Eiring
- Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center at El Paso, El Paso, TX, United States
- Center of Emphasis in Cancer, Department of Molecular and Translational Medicine, Texas Tech University Health Sciences Center at El Paso, El Paso, TX, United States
- L. Frederick Francis Graduate School of Biomedical Sciences, Texas Tech University Health Sciences Center at El Paso, El Paso, TX, United States
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13
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Henderson LW, Sharon EM, Gautam AKS, Anthony AJ, Jarrold MF, Russell DH, Matouschek A, Clemmer DE. Stability of 20S Proteasome Configurations: Preopening the Axial Gate. J Phys Chem Lett 2023; 14:5014-5017. [PMID: 37224454 PMCID: PMC10916758 DOI: 10.1021/acs.jpclett.3c01040] [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] [Indexed: 05/26/2023]
Abstract
Mass spectrometry studies of the stability of the S. cerevisiae 20S proteasome from 11 to 55 °C reveal a series of related configurations and coupled transitions that appear to be associated with opening of the proteolytic core. We find no evidence for dissociation, and all transitions are reversible. A thermodynamic analysis indicates that configurations fall into three general types of structures: enthalpically stabilized, tightly closed (observed as the +54 to +58 charge states) configurations; high-entropy (+60 to +66) states that are proposed as precursors to pore opening; and larger (+70 to +79) partially and fully open pore structures. In the absence of the 19S regulatory unit, the mechanism for opening the 20S pore appears to involve a charge-priming process that loosens the closed-pore configuration. Only a small fraction (≤2%) of these 20S precursor configurations appear to open and thus expose the catalytic cavity.
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Affiliation(s)
- Lucas W Henderson
- Department of Chemistry, Indiana University, Bloomington, Indiana 47401, United States
| | - Edie M Sharon
- Department of Chemistry, Indiana University, Bloomington, Indiana 47401, United States
| | - Amit K S Gautam
- Department of Molecular Biosciences, University of Texas, Austin, Texas 78712, United States
| | - Adam J Anthony
- Department of Chemistry, Indiana University, Bloomington, Indiana 47401, United States
| | - Martin F Jarrold
- Department of Chemistry, Indiana University, Bloomington, Indiana 47401, United States
| | - David H Russell
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Andreas Matouschek
- Department of Molecular Biosciences, University of Texas, Austin, Texas 78712, United States
| | - David E Clemmer
- Department of Chemistry, Indiana University, Bloomington, Indiana 47401, United States
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14
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Abstract
Our understanding of the ubiquitin code has greatly evolved from conventional E1, E2 and E3 enzymes that modify Lys residues on specific substrates with a single type of ubiquitin chain to more complex processes that regulate and mediate ubiquitylation. In this Review, we discuss recently discovered endogenous mechanisms and unprecedented pathways by which pathogens rewrite the ubiquitin code to promote infection. These processes include unconventional ubiquitin modifications involving ester linkages with proteins, lipids and sugars, or ubiquitylation through a phosphoribosyl bridge involving Arg42 of ubiquitin. We also introduce the enzymatic pathways that write and reverse these modifications, such as the papain-like proteases of severe acute respiratory syndrome coronavirus (SARS-CoV) and SARS-CoV-2. Furthermore, structural studies have revealed that the ultimate functions of ubiquitin are mediated not simply by straightforward recognition by ubiquitin-binding domains. Instead, elaborate multivalent interactions between ubiquitylated targets or ubiquitin chains and their readers (for example, the proteasome, the MLL1 complex or DOT1L) can elicit conformational changes that regulate protein degradation or transcription. The newly discovered mechanisms provide opportunities for innovative therapeutic interventions for diseases such as cancer and infectious diseases.
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Affiliation(s)
- Ivan Dikic
- Institute of Biochemistry II, Faculty of Medicine, Goethe University, Frankfurt, Germany.
- Buchmann Institute for Molecular Life Sciences, Goethe University, Frankfurt, Germany.
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15
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Grønbæk-Thygesen M, Kampmeyer C, Hofmann K, Hartmann-Petersen R. The moonlighting of RAD23 in DNA repair and protein degradation. BIOCHIMICA ET BIOPHYSICA ACTA. GENE REGULATORY MECHANISMS 2023; 1866:194925. [PMID: 36863450 DOI: 10.1016/j.bbagrm.2023.194925] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2022] [Revised: 02/20/2023] [Accepted: 02/23/2023] [Indexed: 03/04/2023]
Abstract
A moonlighting protein is one, which carries out multiple, often wholly unrelated, functions. The RAD23 protein is a fascinating example of this, where the same polypeptide and the embedded domains function independently in both nucleotide excision repair (NER) and protein degradation via the ubiquitin-proteasome system (UPS). Hence, through direct binding to the central NER component XPC, RAD23 stabilizes XPC and contributes to DNA damage recognition. Conversely, RAD23 also interacts directly with the 26S proteasome and ubiquitylated substrates to mediate proteasomal substrate recognition. In this function, RAD23 activates the proteolytic activity of the proteasome and engages specifically in well-characterized degradation pathways through direct interactions with E3 ubiquitin-protein ligases and other UPS components. Here, we summarize the past 40 years of research into the roles of RAD23 in NER and the UPS.
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Affiliation(s)
- Martin Grønbæk-Thygesen
- The Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Denmark.
| | - Caroline Kampmeyer
- The Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Denmark
| | - Kay Hofmann
- Institute for Genetics, University of Cologne, Germany
| | - Rasmus Hartmann-Petersen
- The Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Denmark.
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16
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Sun H, Yang K, Zhang X, Fu Y, Yarbro J, Wu Z, Chen PC, Chen T, Peng J. Evaluation of a Pooling Chemoproteomics Strategy with an FDA-Approved Drug Library. Biochemistry 2023; 62:624-632. [PMID: 35969671 PMCID: PMC9905291 DOI: 10.1021/acs.biochem.2c00256] [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: 02/08/2023]
Abstract
Chemoproteomics is a key platform for characterizing the mode of action for compounds, especially for targeted protein degraders such as proteolysis targeting chimeras (PROTACs) and molecular glues. With deep proteome coverage, multiplexed tandem mass tag-mass spectrometry (TMT-MS) can tackle up to 18 samples in a single experiment. Here, we present a pooling strategy for further enhancing the throughput and apply the strategy to an FDA-approved drug library (95 best-in-class compounds). The TMT-MS-based pooling strategy was evaluated in the following steps. First, we demonstrated the capability of TMT-MS by analyzing more than 15 000 unique proteins (> 12 000 gene products) in HEK293 cells treated with five PROTACs (two BRD/BET degraders and three degraders for FAK, ALK, and BTK kinases). We then introduced a rationalized pooling strategy to separate structurally similar compounds in different pools and identified the proteomic response to 14 pools from the drug library. Finally, we validated the proteomic response from one pool by reprofiling the cells via treatment with individual drugs with sufficient replicates. Interestingly, numerous proteins were found to change upon drug treatment, including AMD1, ODC1, PRKX, PRKY, EXO1, AEN, and LRRC58 with 7-hydroxystaurosporine; C6orf64, HMGCR, and RRM2 with Sorafenib; SYS1 and ALAS1 with Venetoclax; and ATF3, CLK1, and CLK4 with Palbocilib. Thus, pooling chemoproteomics screening provides an efficient method for dissecting the molecular targets of compound libraries.
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Affiliation(s)
- Huan Sun
- Departments of Structural Biology and Developmental Neurobiology, St. Jude Children’s Research Hospital, Memphis, TN 38105, USA, Equal Contribution
| | - Ka Yang
- Departments of Structural Biology and Developmental Neurobiology, St. Jude Children’s Research Hospital, Memphis, TN 38105, USA, Equal Contribution
| | - Xue Zhang
- Departments of Structural Biology and Developmental Neurobiology, St. Jude Children’s Research Hospital, Memphis, TN 38105, USA
| | - Yingxue Fu
- Departments of Structural Biology and Developmental Neurobiology, St. Jude Children’s Research Hospital, Memphis, TN 38105, USA
| | - Jay Yarbro
- Departments of Structural Biology and Developmental Neurobiology, St. Jude Children’s Research Hospital, Memphis, TN 38105, USA
| | - Zhiping Wu
- Departments of Structural Biology and Developmental Neurobiology, St. Jude Children’s Research Hospital, Memphis, TN 38105, USA
| | - Ping-Chung Chen
- Departments of Structural Biology and Developmental Neurobiology, St. Jude Children’s Research Hospital, Memphis, TN 38105, USA
| | - Taosheng Chen
- Chemical Biology & Therapeutics Department, St. Jude Children’s Research Hospital, Memphis, TN 38105, USA
| | - Junmin Peng
- Departments of Structural Biology and Developmental Neurobiology, St. Jude Children’s Research Hospital, Memphis, TN 38105, USA, Center for Proteomics and Metabolomics, St. Jude Children’s Research Hospital, Memphis, TN 38105, USA,Correspondence:
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17
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Alwahsh M, Farhat J, Talhouni S, Hamadneh L, Hergenröder R. Bortezomib advanced mechanisms of action in multiple myeloma, solid and liquid tumors along with its novel therapeutic applications. EXCLI JOURNAL 2023; 22:146-168. [PMID: 36998701 PMCID: PMC10043448 DOI: 10.17179/excli2022-5653] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Accepted: 01/12/2023] [Indexed: 04/01/2023]
Abstract
Bortezomib (BTZ) is a first-in-class reversible and selective proteasome inhibitor. It inhibits the ubiquitin proteasome pathway that leads to the degradation of many intracellular proteins. Initially, BTZ was FDA approved for the treatment of refractory or relapsed multiple myeloma (MM) in 2003. Later, its usage was approved for patients with previously untreated MM. In 2006, BTZ was approved for the treatment of relapsed or refractory Mantle Cell Lymphoma (MCL) and, in 2014, for previously untreated MCL. BTZ has been extensively studied either alone or in combination with other drugs for the treatment of different liquid tumors especially in MM. However, limited data evaluated the efficacy and safety of using BTZ in patients with solid tumors. In this review, we will discuss the advanced and novel mechanisms of action of BTZ documented in MM, solid tumors and liquid tumors. Moreover, we will shed the light on the newly discovered pharmacological effects of BTZ in other prevalent diseases.
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Affiliation(s)
- Mohammad Alwahsh
- Department of Pharmacy, Faculty of Pharmacy, Al-Zaytoonah University of Jordan, P.O. Box 130, Amman, 11733, Jordan
- Leibniz-Institut für Analytische Wissenschaften-ISAS-e.V., 44139 Dortmund, Germany
- Institute of Pathology and Medical Research Center (ZMF), University Medical Center Mannheim, Heidelberg University, 68167 Mannheim, Germany
- *To whom correspondence should be addressed: Mohammad Alwahsh, Department of Pharmacy, Faculty of Pharmacy, Al-Zaytoonah University of Jordan, P.O. Box 130, Amman, 11733, Jordan, E-mail:
| | - Joviana Farhat
- Department of Epidemiology and Population Health, College of Medicine and Health Sciences, Khalifa University, Abu Dhabi, PO Box 127788, United Arab Emirates
| | - Shahd Talhouni
- Department of Pharmacy, Faculty of Pharmacy, Al-Zaytoonah University of Jordan, P.O. Box 130, Amman, 11733, Jordan
| | - Lama Hamadneh
- Department of Pharmacy, Faculty of Pharmacy, Al-Zaytoonah University of Jordan, P.O. Box 130, Amman, 11733, Jordan
| | - Roland Hergenröder
- Leibniz-Institut für Analytische Wissenschaften-ISAS-e.V., 44139 Dortmund, Germany
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18
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Koroleva OA, Dutikova YV, Trubnikov AV, Zenov FA, Manasova EV, Shtil AA, Kurkin AV. PROTAC: targeted drug strategy. Principles and limitations. Russ Chem Bull 2022; 71:2310-2334. [PMID: 36569659 PMCID: PMC9762658 DOI: 10.1007/s11172-022-3659-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Revised: 06/08/2022] [Accepted: 06/20/2022] [Indexed: 12/23/2022]
Abstract
The PROTAC (PROteolysis TArgeting Chimera) technology is a method of targeting intracellular proteins previously considered undruggable. This technology utilizes the ubiquitin-proteasome system in cells to specifically degrade target proteins, thereby offering significant advantages over conventional small-molecule inhibitors of the enzymatic function. Preclinical and preliminary clinical trials of PROTAC-based compounds (degraders) are presented. The review considers the general principles of the design of degraders. Advances and challenges of the PROTAC technology are discussed.
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Affiliation(s)
- O. A. Koroleva
- Department of Chemistry, Lomonosov Moscow State University, Build. 3, 1 Leninskie Gory, 119991 Moscow, Russian Federation
| | - Yu. V. Dutikova
- Patent & Law Firm “A. Zalesov and Partners”, Build. 9, 2 ul. Marshala Rybalko, 123060 Moscow, Russian Federation
| | - A. V. Trubnikov
- Department of Chemistry, Lomonosov Moscow State University, Build. 3, 1 Leninskie Gory, 119991 Moscow, Russian Federation
| | - F. A. Zenov
- Department of Chemistry, Lomonosov Moscow State University, Build. 3, 1 Leninskie Gory, 119991 Moscow, Russian Federation
| | - E. V. Manasova
- Department of Chemistry, Lomonosov Moscow State University, Build. 3, 1 Leninskie Gory, 119991 Moscow, Russian Federation
| | - A. A. Shtil
- Department of Chemistry, Lomonosov Moscow State University, Build. 3, 1 Leninskie Gory, 119991 Moscow, Russian Federation
- N. N. Blokhin National Medical Research Center of Oncology, Ministry of Health of the Russian Federation, Build. 15, 24 Kashirskoe shosse, 115478 Moscow, Russian Federation
| | - A. V. Kurkin
- Department of Chemistry, Lomonosov Moscow State University, Build. 3, 1 Leninskie Gory, 119991 Moscow, Russian Federation
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19
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The deubiquitinating enzyme STAMBP is a newly discovered driver of triple-negative breast cancer progression that maintains RAI14 protein stability. Exp Mol Med 2022; 54:2047-2059. [PMID: 36434041 PMCID: PMC9723177 DOI: 10.1038/s12276-022-00890-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Revised: 09/13/2022] [Accepted: 09/19/2022] [Indexed: 11/27/2022] Open
Abstract
Triple-negative breast cancer (TNBC) is a heterogeneous malignancy in women. It is associated with poor prognosis, aggressive malignant behavior, and limited treatment options. In the ubiquitin‒proteasome system (UPS), deubiquitinases (DUBs) are potential therapeutic targets for various tumors. In this study, by performing unbiased siRNA screening, we identified STAMBP, a JAMM metalloprotease in the DUB family, as a driver of human TNBC tumor growth. Functionally, the knockdown of STAMBP inhibited the proliferation, migration, and invasion of multiple TNBC cell lines. Immunoprecipitation-mass spectrometry combined with functional and morphological analysis verified the interaction between STAMBP and the actin-binding protein RAI14. Mechanistically, STAMBP stabilized the RAI14 protein by suppressing the K48-linked ubiquitination of RAI14 and thus prevented its proteasomal degradation. Therefore, knocking down STAMBP resulted in the reduction in RAI14 protein levels and suppression of tumor growth in vitro and in vivo. Importantly, high levels of STAMBP were correlated with poor prognosis in TNBC patients. In summary, we reveal a previously unrecognized DUB pathway that promotes TNBC progression and provides a rationale for potential therapeutic interventions for the treatment of TNBC.
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20
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Sparks A, Kelly CJ, Saville MK. Ubiquitin receptors play redundant roles in the proteasomal degradation of the p53 repressor MDM2. FEBS Lett 2022; 596:2746-2767. [PMID: 35735670 PMCID: PMC9796813 DOI: 10.1002/1873-3468.14436] [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: 05/11/2022] [Revised: 06/01/2022] [Accepted: 06/05/2022] [Indexed: 01/07/2023]
Abstract
Much remains to be determined about the participation of ubiquitin receptors in proteasomal degradation and their potential as therapeutic targets. Suppression of the ubiquitin receptor S5A/PSMD4/hRpn10 alone stabilises p53/TP53 but not the key p53 repressor MDM2. Here, we observed S5A and the ubiquitin receptors ADRM1/PSMD16/hRpn13 and RAD23A and B functionally overlap in MDM2 degradation. We provide further evidence that degradation of only a subset of ubiquitinated proteins is sensitive to S5A knockdown because ubiquitin receptor redundancy is commonplace. p53 can be upregulated by S5A modulation while degradation of substrates with redundant receptors is maintained. Our observations and analysis of Cancer Dependency Map (DepMap) screens show S5A depletion/loss substantially reduces cancer cell line viability. This and selective S5A dependency of proteasomal substrates make S5A a target of interest for cancer therapy.
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Affiliation(s)
| | - Christopher J. Kelly
- School of MedicineUniversity of DundeeUK,Institute of Infection, Immunity and InflammationUniversity of GlasgowUK
| | - Mark K. Saville
- School of MedicineUniversity of DundeeUK,Silver River EditingDundeeUK
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21
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The RPN12a proteasome subunit is essential for the multiple hormonal homeostasis controlling the progression of leaf senescence. Commun Biol 2022; 5:1043. [PMID: 36180574 PMCID: PMC9525688 DOI: 10.1038/s42003-022-03998-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Accepted: 09/14/2022] [Indexed: 11/09/2022] Open
Abstract
The 26S proteasome is a conserved multi-subunit machinery in eukaryotes. It selectively degrades ubiquitinated proteins, which in turn provides an efficient molecular mechanism to regulate numerous cellular functions and developmental processes. Here, we studied a new loss-of-function allele of RPN12a, a plant ortholog of the yeast and human structural component of the 19S proteasome RPN12. Combining a set of biochemical and molecular approaches, we confirmed that a rpn12a knock-out had exacerbated 20S and impaired 26S activities. The altered proteasomal activity led to a pleiotropic phenotype affecting both the vegetative growth and reproductive phase of the plant, including a striking repression of leaf senescence associate cell-death. Further investigation demonstrated that RPN12a is involved in the regulation of several conjugates associated with the auxin, cytokinin, ethylene and jasmonic acid homeostasis. Such enhanced aptitude of plant cells for survival in rpn12a contrasts with reports on animals, where 26S proteasome mutants generally show an accelerated cell death phenotype.
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22
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Morehouse JP, Baker TA, Sauer RT. FtsH degrades dihydrofolate reductase by recognizing a partially folded species. Protein Sci 2022; 31:e4410. [PMID: 36630366 PMCID: PMC9601784 DOI: 10.1002/pro.4410] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Revised: 07/21/2022] [Accepted: 07/24/2022] [Indexed: 01/14/2023]
Abstract
AAA+ proteolytic machines play essential roles in maintaining and rebalancing the cellular proteome in response to stress, developmental cues, and environmental changes. Of the five AAA+ proteases in Escherichia coli, FtsH is unique in its attachment to the inner membrane and its function in degrading both membrane and cytosolic proteins. E. coli dihydrofolate reductase (DHFR) is a stable and biophysically well-characterized protein, which a previous study found resisted FtsH degradation despite the presence of an ssrA degron. By contrast, we find that FtsH degrades DHFR fused to a long peptide linker and ssrA tag. Surprisingly, we also find that FtsH degrades DHFR with shorter linkers and ssrA tag, and without any linker or tag. Thus, FtsH must be able to recognize a sequence element or elements within DHFR. We find that FtsH degradation of DHFR is noncanonical in the sense that it does not rely upon recognition of an unstructured polypeptide at or near the N-terminus or C-terminus of the substrate. Results using peptide-array experiments, mutant DHFR proteins, and fusion proteins suggest that FtsH recognizes an internal sequence in a species of DHFR that is partially unfolded. Overall, our findings provide insight into substrate recognition by FtsH and indicate that its degradation capacity is broader than previously reported.
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Affiliation(s)
- Juhee P. Morehouse
- Department of BiologyMassachusetts Institute of TechnologyCambridgeMassachusettsUSA
| | - Tania A. Baker
- Department of BiologyMassachusetts Institute of TechnologyCambridgeMassachusettsUSA
| | - Robert T. Sauer
- Department of BiologyMassachusetts Institute of TechnologyCambridgeMassachusettsUSA
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23
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Yang Y, Karthikeyan A, Yin J, Jin T, Ren R, Fang F, Cai H, Liu M, Wang D, Li K, Zhi H. The E3 Ligase GmPUB21 Negatively Regulates Drought and Salinity Stress Response in Soybean. Int J Mol Sci 2022; 23:6893. [PMID: 35805901 PMCID: PMC9266294 DOI: 10.3390/ijms23136893] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Revised: 06/17/2022] [Accepted: 06/20/2022] [Indexed: 01/27/2023] Open
Abstract
E3-ubiquitin ligases are known to confer abiotic stress responses in plants. In the present study, GmPUB21, a novel U-box E3-ubiquitin ligase-encoding gene, was isolated from soybean and functionally characterized. The expression of GmPUB21, which possesses E3-ubiquitin ligase activity, was found to be significantly up-regulated by drought, salinity, and ABA treatments. The fusion protein GmPUB21-GFP was localized in the cytoplasm, nucleus, and plasma membrane. Transgenic lines of the Nicotiana benthamiana over-expressing GmPUB21 showed more sensitive to osmotic, salinity stress and ABA in seed germination and inhibited mannitol/NaCl-mediated stomatal closure. Moreover, higher reactive oxygen species accumulation was observed in GmPUB21 overexpressing plants after drought and salinity treatment than in wild-type (WT) plants. Contrarily, silencing of GmPUB21 in soybean plants significantly enhanced the tolerance to drought and salinity stresses. Collectively, our results revealed that GmPUB21 negatively regulates the drought and salinity tolerance by increasing the stomatal density and aperture via the ABA signaling pathway. These findings improved our understanding of the role of GmPUB21 under drought and salinity stresses in soybean.
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Affiliation(s)
- Yunhua Yang
- National Center for Soybean Improvement, National Key Laboratory for Crop Genetics and Germplasm Enhancement, Key Laboratory of Biology and Genetic Improvement of Soybean—Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China; (Y.Y.); (J.Y.); (T.J.); (F.F.); (H.C.); (M.L.); (D.W.)
| | - Adhimoolam Karthikeyan
- Subtropical Horticulture Research Institute, Jeju National University, Jeju 63243, Korea;
| | - Jinlong Yin
- National Center for Soybean Improvement, National Key Laboratory for Crop Genetics and Germplasm Enhancement, Key Laboratory of Biology and Genetic Improvement of Soybean—Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China; (Y.Y.); (J.Y.); (T.J.); (F.F.); (H.C.); (M.L.); (D.W.)
| | - Tongtong Jin
- National Center for Soybean Improvement, National Key Laboratory for Crop Genetics and Germplasm Enhancement, Key Laboratory of Biology and Genetic Improvement of Soybean—Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China; (Y.Y.); (J.Y.); (T.J.); (F.F.); (H.C.); (M.L.); (D.W.)
| | - Rui Ren
- Center for Crop Genome Engineering, College of Agronomy, Henan Agricultural University, Zhengzhou 450046, China;
| | - Fei Fang
- National Center for Soybean Improvement, National Key Laboratory for Crop Genetics and Germplasm Enhancement, Key Laboratory of Biology and Genetic Improvement of Soybean—Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China; (Y.Y.); (J.Y.); (T.J.); (F.F.); (H.C.); (M.L.); (D.W.)
| | - Han Cai
- National Center for Soybean Improvement, National Key Laboratory for Crop Genetics and Germplasm Enhancement, Key Laboratory of Biology and Genetic Improvement of Soybean—Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China; (Y.Y.); (J.Y.); (T.J.); (F.F.); (H.C.); (M.L.); (D.W.)
| | - Mengzhuo Liu
- National Center for Soybean Improvement, National Key Laboratory for Crop Genetics and Germplasm Enhancement, Key Laboratory of Biology and Genetic Improvement of Soybean—Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China; (Y.Y.); (J.Y.); (T.J.); (F.F.); (H.C.); (M.L.); (D.W.)
| | - Dagang Wang
- National Center for Soybean Improvement, National Key Laboratory for Crop Genetics and Germplasm Enhancement, Key Laboratory of Biology and Genetic Improvement of Soybean—Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China; (Y.Y.); (J.Y.); (T.J.); (F.F.); (H.C.); (M.L.); (D.W.)
| | - Kai Li
- National Center for Soybean Improvement, National Key Laboratory for Crop Genetics and Germplasm Enhancement, Key Laboratory of Biology and Genetic Improvement of Soybean—Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China; (Y.Y.); (J.Y.); (T.J.); (F.F.); (H.C.); (M.L.); (D.W.)
| | - Haijian Zhi
- National Center for Soybean Improvement, National Key Laboratory for Crop Genetics and Germplasm Enhancement, Key Laboratory of Biology and Genetic Improvement of Soybean—Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China; (Y.Y.); (J.Y.); (T.J.); (F.F.); (H.C.); (M.L.); (D.W.)
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24
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Enenkel C, Kang RW, Wilfling F, Ernst OP. Intracellular localization of the proteasome in response to stress conditions. J Biol Chem 2022; 298:102083. [PMID: 35636514 PMCID: PMC9218506 DOI: 10.1016/j.jbc.2022.102083] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Revised: 05/13/2022] [Accepted: 05/16/2022] [Indexed: 12/15/2022] Open
Abstract
The ubiquitin–proteasome system fulfills an essential role in regulating protein homeostasis by spatially and temporally controlling proteolysis in an ATP- and ubiquitin-dependent manner. However, the localization of proteasomes is highly variable under diverse cellular conditions. In yeast, newly synthesized proteasomes are primarily localized to the nucleus during cell proliferation. Yeast proteasomes are transported into the nucleus through the nuclear pore either as immature subcomplexes or as mature enzymes via adapter proteins Sts1 and Blm10, while in mammalian cells, postmitotic uptake of proteasomes into the nucleus is mediated by AKIRIN2, an adapter protein essentially required for nuclear protein degradation. Stressful growth conditions and the reversible halt of proliferation, that is quiescence, are associated with a decline in ATP and the reorganization of proteasome localization. Cellular stress leads to proteasome accumulation in membraneless granules either in the nucleus or in the cytoplasm. In quiescence, yeast proteasomes are sequestered in an ubiquitin-dependent manner into motile and reversible proteasome storage granules in the cytoplasm. In cancer cells, upon amino acid deprivation, heat shock, osmotic stress, oxidative stress, or the inhibition of either proteasome activity or nuclear export, reversible proteasome foci containing polyubiquitinated substrates are formed by liquid–liquid phase separation in the nucleus. In this review, we summarize recent literature revealing new links between nuclear transport, ubiquitin signaling, and the intracellular organization of proteasomes during cellular stress conditions.
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Affiliation(s)
- Cordula Enenkel
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada.
| | - Ryu Won Kang
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Florian Wilfling
- Mechanisms of Cellular Quality Control, Max-Planck-Institute of Biophysics, Frankfurt, Germany
| | - Oliver P Ernst
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada; Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
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25
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Behl T, Kumar S, Althafar ZM, Sehgal A, Singh S, Sharma N, Badavath VN, Yadav S, Bhatia S, Al-Harrasi A, Almoshari Y, Almikhlafi MA, Bungau S. Exploring the Role of Ubiquitin-Proteasome System in Parkinson's Disease. Mol Neurobiol 2022; 59:4257-4273. [PMID: 35505049 DOI: 10.1007/s12035-022-02851-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Accepted: 04/25/2022] [Indexed: 02/06/2023]
Abstract
Over the last decade, researchers have discovered that a group of apparently unrelated neurodegenerative disorders, such as Parkinson's disease, have remarkable cellular and molecular biology similarities. Protein misfolding and aggregation are involved in all of the neurodegenerative conditions; as a result, inclusion bodies aggregation starts in the cells. Chaperone proteins and ubiquitin (26S proteasome's proteolysis signal), which aid in refolding misfolded proteins, are frequently found in these aggregates. The discovery of disease-causing gene alterations that code for multiple ubiquitin-proteasome pathway proteins in Parkinson's disease has strengthened the relationship between the ubiquitin-proteasome system and neurodegeneration. The specific molecular linkages between these systems and pathogenesis, on the other hand, are unknown and controversial. We outline the current level of knowledge in this article, focusing on important unanswered problems.
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Affiliation(s)
- Tapan Behl
- Chitkara College of Pharmacy, Chitkara University, Punjab, India.
| | - Sachin Kumar
- Chitkara College of Pharmacy, Chitkara University, Punjab, India
| | - Ziyad M Althafar
- Department of Medical Laboratories Sciences, College of Applied Medical Sciences in Alquwayiyah, Shaqra University, Riyadh, Saudi Arabia
| | - Aayush Sehgal
- Chitkara College of Pharmacy, Chitkara University, Punjab, India
| | - Sukhbir Singh
- Chitkara College of Pharmacy, Chitkara University, Punjab, India
| | - Neelam Sharma
- Chitkara College of Pharmacy, Chitkara University, Punjab, India
| | | | - Shivam Yadav
- Yashraj Institute of Pharmacy, Uttar Pradesh, India
| | - Saurabh Bhatia
- Natural & Medical Sciences Research Center, University of Nizwa, Nizwa, Oman.,School of Health Science, University of Petroleum and Energy Studies, Dehradun, Uttarakhand, India
| | - Ahmed Al-Harrasi
- Natural & Medical Sciences Research Center, University of Nizwa, Nizwa, Oman
| | - Yosif Almoshari
- Department of Pharmaceutics, College of Pharmacy, Jazan University, Jazan, Saudi Arabia
| | - Mohannad A Almikhlafi
- Department of Pharmacology and Toxicology, College of Pharmacy, Taibha University, Madinah, Saudi Arabia
| | - Simona Bungau
- Department of Pharmacy, Faculty of Medicine and Pharmacy, University of Oradea, Oradea, Romania
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26
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Abstract
Targeted protein degradation (TPD) is an emerging therapeutic modality with the potential to tackle disease-causing proteins that have historically been highly challenging to target with conventional small molecules. In the 20 years since the concept of a proteolysis-targeting chimera (PROTAC) molecule harnessing the ubiquitin-proteasome system to degrade a target protein was reported, TPD has moved from academia to industry, where numerous companies have disclosed programmes in preclinical and early clinical development. With clinical proof-of-concept for PROTAC molecules against two well-established cancer targets provided in 2020, the field is poised to pursue targets that were previously considered 'undruggable'. In this Review, we summarize the first two decades of PROTAC discovery and assess the current landscape, with a focus on industry activity. We then discuss key areas for the future of TPD, including establishing the target classes for which TPD is most suitable, expanding the use of ubiquitin ligases to enable precision medicine and extending the modality beyond oncology.
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Affiliation(s)
| | | | - Craig M Crews
- Department of Molecular, Cellular & Developmental Biology, Yale University, New Haven, CT, USA.
- Department of Pharmacology, Yale University, New Haven, CT, USA.
- Department of Chemistry, Yale University, New Haven, CT, USA.
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27
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Hung KYS, Klumpe S, Eisele MR, Elsasser S, Tian G, Sun S, Moroco JA, Cheng TC, Joshi T, Seibel T, Van Dalen D, Feng XH, Lu Y, Ovaa H, Engen JR, Lee BH, Rudack T, Sakata E, Finley D. Allosteric control of Ubp6 and the proteasome via a bidirectional switch. Nat Commun 2022; 13:838. [PMID: 35149681 PMCID: PMC8837689 DOI: 10.1038/s41467-022-28186-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2021] [Accepted: 01/10/2022] [Indexed: 11/09/2022] Open
Abstract
The proteasome recognizes ubiquitinated proteins and can also edit ubiquitin marks, allowing substrates to be rejected based on ubiquitin chain topology. In yeast, editing is mediated by deubiquitinating enzyme Ubp6. The proteasome activates Ubp6, whereas Ubp6 inhibits the proteasome through deubiquitination and a noncatalytic effect. Here, we report cryo-EM structures of the proteasome bound to Ubp6, based on which we identify mutants in Ubp6 and proteasome subunit Rpt1 that abrogate Ubp6 activation. The Ubp6 mutations define a conserved region that we term the ILR element. The ILR is found within the BL1 loop, which obstructs the catalytic groove in free Ubp6. Rpt1-ILR interaction opens the groove by rearranging not only BL1 but also a previously undescribed network of three interconnected active-site-blocking loops. Ubp6 activation and noncatalytic proteasome inhibition are linked in that they are eliminated by the same mutations. Ubp6 and ubiquitin together drive proteasomes into a unique conformation associated with proteasome inhibition. Thus, a multicomponent allosteric switch exerts simultaneous control over both Ubp6 and the proteasome.
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Affiliation(s)
| | - Sven Klumpe
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, 82152, Martinsried, Germany
| | - Markus R Eisele
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, 82152, Martinsried, Germany
| | - Suzanne Elsasser
- Department of Cell Biology, Harvard Medical School, Boston, MA, 02115, USA
| | - Geng Tian
- Department of Cell Biology, Harvard Medical School, Boston, MA, 02115, USA
| | - Shuangwu Sun
- Department of Cell Biology, Harvard Medical School, Boston, MA, 02115, USA.,Life Sciences Institute (LSI), Zhejiang University, Hangzhou, 310058, China
| | - Jamie A Moroco
- Department of Chemistry and Chemical Biology, Northeastern University, Boston, MA, 02115, USA
| | - Tat Cheung Cheng
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, 82152, Martinsried, Germany.,Institute for Auditory Neuroscience, University Medical Center Göttingen, 37077, Göttingen, Germany
| | - Tapan Joshi
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, 82152, Martinsried, Germany
| | - Timo Seibel
- Department of Cell Biology, Harvard Medical School, Boston, MA, 02115, USA
| | - Duco Van Dalen
- Leiden University Medical Center, Einthovenweg 20, 2333, Leiden, ZC, the Netherlands
| | - Xin-Hua Feng
- Life Sciences Institute (LSI), Zhejiang University, Hangzhou, 310058, China
| | - Ying Lu
- Department of Systems Biology, Harvard Medical School, Boston, MA, 02115, USA
| | - Huib Ovaa
- Leiden University Medical Center, Einthovenweg 20, 2333, Leiden, ZC, the Netherlands
| | - John R Engen
- Department of Chemistry and Chemical Biology, Northeastern University, Boston, MA, 02115, USA
| | - Byung-Hoon Lee
- Department of New Biology, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, 42988, Korea.
| | - Till Rudack
- Biospectroscopy, Center for Protein Diagnostics (PRODI), Ruhr University Bochum, 44801, Bochum, Germany. .,Department of Biophysics, Ruhr University Bochum, 44801, Bochum, Germany.
| | - Eri Sakata
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, 82152, Martinsried, Germany. .,Institute for Auditory Neuroscience, University Medical Center Göttingen, 37077, Göttingen, Germany. .,Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells (MBExC), University of Goettingen, 37073, Göttingen, Germany.
| | - Daniel Finley
- Department of Cell Biology, Harvard Medical School, Boston, MA, 02115, USA.
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28
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Kavalchuk M, Jomaa A, Müller AU, Weber-Ban E. Structural basis of prokaryotic ubiquitin-like protein engagement and translocation by the mycobacterial Mpa-proteasome complex. Nat Commun 2022; 13:276. [PMID: 35022401 PMCID: PMC8755798 DOI: 10.1038/s41467-021-27787-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Accepted: 12/13/2021] [Indexed: 12/19/2022] Open
Abstract
Proteasomes are present in eukaryotes, archaea and Actinobacteria, including the human pathogen Mycobacterium tuberculosis, where proteasomal degradation supports persistence inside the host. In mycobacteria and other members of Actinobacteria, prokaryotic ubiquitin-like protein (Pup) serves as a degradation tag post-translationally conjugated to target proteins for their recruitment to the mycobacterial proteasome ATPase (Mpa). Here, we use single-particle cryo-electron microscopy to determine the structure of Mpa in complex with the 20S core particle at an early stage of pupylated substrate recruitment, shedding light on the mechanism of substrate translocation. Two conformational states of Mpa show how substrate is translocated stepwise towards the degradation chamber of the proteasome core particle. We also demonstrate, in vitro and in vivo, the importance of a structural feature in Mpa that allows formation of alternating charge-complementary interactions with the proteasome resulting in radial, rail-guided movements during the ATPase conformational cycle. Pup is the bacterial analog of ubiquitin for targeting proteins to the proteasome. Here, the authors use cryoEM to visualize structures of the Mycobacterium tuberculosis proteasome translocating a Pup-tagged substrate.
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Affiliation(s)
- Mikhail Kavalchuk
- ETH Zurich, Institute of Molecular Biology & Biophysics, CH-8093, Zurich, Switzerland
| | - Ahmad Jomaa
- ETH Zurich, Institute of Molecular Biology & Biophysics, CH-8093, Zurich, Switzerland.
| | - Andreas U Müller
- ETH Zurich, Institute of Molecular Biology & Biophysics, CH-8093, Zurich, Switzerland
| | - Eilika Weber-Ban
- ETH Zurich, Institute of Molecular Biology & Biophysics, CH-8093, Zurich, Switzerland.
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29
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Fungal Secondary Metabolites as Inhibitors of the Ubiquitin-Proteasome System. Int J Mol Sci 2021; 22:ijms222413309. [PMID: 34948102 PMCID: PMC8707610 DOI: 10.3390/ijms222413309] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Revised: 12/04/2021] [Accepted: 12/07/2021] [Indexed: 12/19/2022] Open
Abstract
The ubiquitin–proteasome system (UPS) is the major non-lysosomal pathway responsible for regulated degradation of intracellular proteins in eukaryotes. As the principal proteolytic pathway in the cytosol and the nucleus, the UPS serves two main functions: the quality control function (i.e., removal of damaged, misfolded, and functionally incompetent proteins) and a major regulatory function (i.e., targeted degradation of a variety of short-lived regulatory proteins involved in cell cycle control, signal transduction cascades, and regulation of gene expression and metabolic pathways). Aberrations in the UPS are implicated in numerous human pathologies such as cancer, neurodegenerative disorders, autoimmunity, inflammation, or infectious diseases. Therefore, the UPS has become an attractive target for drug discovery and development. For the past two decades, much research has been focused on identifying and developing compounds that target specific components of the UPS. Considerable effort has been devoted to the development of both second-generation proteasome inhibitors and inhibitors of ubiquitinating/deubiquitinating enzymes. With the feature of unique structure and bioactivity, secondary metabolites (natural products) serve as the lead compounds in the development of new therapeutic drugs. This review, for the first time, summarizes fungal secondary metabolites found to act as inhibitors of the UPS components.
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30
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Armstrong LA, Lange SM, Dee Cesare V, Matthews SP, Nirujogi RS, Cole I, Hope A, Cunningham F, Toth R, Mukherjee R, Bojkova D, Gruber F, Gray D, Wyatt PG, Cinatl J, Dikic I, Davies P, Kulathu Y. Biochemical characterization of protease activity of Nsp3 from SARS-CoV-2 and its inhibition by nanobodies. PLoS One 2021; 16:e0253364. [PMID: 34270554 PMCID: PMC8284666 DOI: 10.1371/journal.pone.0253364] [Citation(s) in RCA: 51] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Accepted: 06/04/2021] [Indexed: 12/12/2022] Open
Abstract
Of the 16 non-structural proteins (Nsps) encoded by SARS CoV-2, Nsp3 is the largest and plays important roles in the viral life cycle. Being a large, multidomain, transmembrane protein, Nsp3 has been the most challenging Nsp to characterize. Encoded within Nsp3 is the papain-like protease domain (PLpro) that cleaves not only the viral polypeptide but also K48-linked polyubiquitin and the ubiquitin-like modifier, ISG15, from host cell proteins. We here compare the interactors of PLpro and Nsp3 and find a largely overlapping interactome. Intriguingly, we find that near full length Nsp3 is a more active protease compared to the minimal catalytic domain of PLpro. Using a MALDI-TOF based assay, we screen 1971 approved clinical compounds and identify five compounds that inhibit PLpro with IC50s in the low micromolar range but showed cross reactivity with other human deubiquitinases and had no significant antiviral activity in cellular SARS-CoV-2 infection assays. We therefore looked for alternative methods to block PLpro activity and engineered competitive nanobodies that bind to PLpro at the substrate binding site with nanomolar affinity thus inhibiting the enzyme. Our work highlights the importance of studying Nsp3 and provides tools and valuable insights to investigate Nsp3 biology during the viral infection cycle.
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Affiliation(s)
- Lee A. Armstrong
- MRC Protein Phosphorylation and Ubiquitylation Unit, Sir James Black Centre, School of Life Sciences, University of Dundee, Dundee, Scotland, United Kingdom
| | - Sven M. Lange
- MRC Protein Phosphorylation and Ubiquitylation Unit, Sir James Black Centre, School of Life Sciences, University of Dundee, Dundee, Scotland, United Kingdom
| | - Virginia Dee Cesare
- MRC Protein Phosphorylation and Ubiquitylation Unit, Sir James Black Centre, School of Life Sciences, University of Dundee, Dundee, Scotland, United Kingdom
| | - Stephen P. Matthews
- MRC Protein Phosphorylation and Ubiquitylation Unit, Sir James Black Centre, School of Life Sciences, University of Dundee, Dundee, Scotland, United Kingdom
| | - Raja Sekhar Nirujogi
- MRC Protein Phosphorylation and Ubiquitylation Unit, Sir James Black Centre, School of Life Sciences, University of Dundee, Dundee, Scotland, United Kingdom
| | - Isobel Cole
- MRC Protein Phosphorylation and Ubiquitylation Unit, Sir James Black Centre, School of Life Sciences, University of Dundee, Dundee, Scotland, United Kingdom
| | - Anthony Hope
- Drug Discovery Unit, School of Life Sciences, University of Dundee, Dundee, Scotland, United Kingdom
| | - Fraser Cunningham
- Drug Discovery Unit, School of Life Sciences, University of Dundee, Dundee, Scotland, United Kingdom
| | - Rachel Toth
- MRC Reagents and Services, University of Dundee, Dundee, Scotland, United Kingdom
| | - Rukmini Mukherjee
- Institute of Biochemistry II, Goethe University Frankfurt Medical Faculty, University Hospital, Frankfurt am Main, Germany
- Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Denisa Bojkova
- Institute of Medical Virology, University Hospital Frankfurt, Frankfurt am Main, Germany
| | - Franz Gruber
- National Phenotypic Screening Centre, University of Dundee, Dundee, Scotland, United Kingdom
| | - David Gray
- Drug Discovery Unit, School of Life Sciences, University of Dundee, Dundee, Scotland, United Kingdom
| | - Paul G. Wyatt
- Drug Discovery Unit, School of Life Sciences, University of Dundee, Dundee, Scotland, United Kingdom
| | - Jindrich Cinatl
- Institute of Medical Virology, University Hospital Frankfurt, Frankfurt am Main, Germany
| | - Ivan Dikic
- Institute of Biochemistry II, Goethe University Frankfurt Medical Faculty, University Hospital, Frankfurt am Main, Germany
- Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, Frankfurt am Main, Germany
- Max Planck Institute of Biophysics, Frankfurt am Main, Germany
| | - Paul Davies
- MRC Protein Phosphorylation and Ubiquitylation Unit, Sir James Black Centre, School of Life Sciences, University of Dundee, Dundee, Scotland, United Kingdom
| | - Yogesh Kulathu
- MRC Protein Phosphorylation and Ubiquitylation Unit, Sir James Black Centre, School of Life Sciences, University of Dundee, Dundee, Scotland, United Kingdom
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31
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Small-Molecule Inhibitors Targeting Proteasome-Associated Deubiquitinases. Int J Mol Sci 2021; 22:ijms22126213. [PMID: 34207520 PMCID: PMC8226605 DOI: 10.3390/ijms22126213] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Revised: 06/02/2021] [Accepted: 06/05/2021] [Indexed: 02/06/2023] Open
Abstract
The 26S proteasome is the principal protease for regulated intracellular proteolysis. This multi-subunit complex is also pivotal for clearance of harmful proteins that are produced throughout the lifetime of eukaryotes. Recent structural and kinetic studies have revealed a multitude of conformational states of the proteasome in substrate-free and substrate-engaged forms. These conformational transitions demonstrate that proteasome is a highly dynamic machinery during substrate processing that can be also controlled by a number of proteasome-associated factors. Essentially, three distinct family of deubiquitinases–USP14, RPN11, and UCH37–are associated with the 19S regulatory particle of human proteasome. USP14 and UCH37 are capable of editing ubiquitin conjugates during the process of their dynamic engagement into the proteasome prior to the catalytic commitment. In contrast, RPN11-mediated deubiquitination is directly coupled to substrate degradation by sensing the proteasome’s conformational switch into the commitment steps. Therefore, proteasome-bound deubiquitinases are likely to tailor the degradation events in accordance with substrate processing steps and for dynamic proteolysis outcomes. Recent chemical screening efforts have yielded highly selective small-molecule inhibitors for targeting proteasomal deubiquitinases, such as USP14 and RPN11. USP14 inhibitors, IU1 and its progeny, were found to promote the degradation of a subset of substrates probably by overriding USP14-imposed checkpoint on the proteasome. On the other hand, capzimin, a RPN11 inhibitor, stabilized the proteasome substrates and showed the anti-proliferative effects on cancer cells. It is highly conceivable that these specific inhibitors will aid to dissect the role of each deubiquitinase on the proteasome. Moreover, customized targeting of proteasome-associated deubiquitinases may also provide versatile therapeutic strategies for induced or repressed protein degradation depending on proteolytic demand and cellular context.
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32
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Kyca T, Pavlíková L, Boháčová V, Mišák A, Poturnayová A, Breier A, Sulová Z, Šereš M. Insight into Bortezomib Focusing on Its Efficacy against P-gp-Positive MDR Leukemia Cells. Int J Mol Sci 2021; 22:ijms22115504. [PMID: 34071136 PMCID: PMC8197160 DOI: 10.3390/ijms22115504] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Revised: 05/12/2021] [Accepted: 05/21/2021] [Indexed: 02/06/2023] Open
Abstract
In this paper, we compared the effects of bortezomib on L1210 (S) cells with its effects on P-glycoprotein (P-gp)-positive variant S cells, which expressed P-gp either after selection with vincristine (R cells) or after transfection with a human gene encoding P-gp (T cells). Bortezomib induced the death-related effects in the S, R, and T cells at concentrations not exceeding 10 nM. Bortezomib-induced cell cycle arrest in the G2/M phase was more pronounced in the S cells than in the R or T cells and was related to the expression levels of cyclins, cyclin-dependent kinases, and their inhibitors. We also observed an increase in the level of polyubiquitinated proteins (via K48-linkage) and a decrease in the gene expression of some deubiquitinases after treatment with bortezomib. Resistant cells expressed higher levels of genes encoding 26S proteasome components and the chaperone HSP90, which is involved in 26S proteasome assembly. After 4 h of preincubation, bortezomib induced a more pronounced depression of proteasome activity in S cells than in R or T cells. However, none of these changes alone or in combination sufficiently suppressed the sensitivity of R or T cells to bortezomib, which remained at a level similar to that of S cells.
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MESH Headings
- ATP Binding Cassette Transporter, Subfamily B, Member 1/genetics
- ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism
- Animals
- Antineoplastic Agents/pharmacology
- Bortezomib/pharmacology
- Cell Cycle/drug effects
- Cell Division
- Cell Line, Tumor
- Deubiquitinating Enzymes
- Drug Resistance, Multiple/drug effects
- Drug Resistance, Neoplasm/drug effects
- Fluoresceins/metabolism
- Gene Expression Regulation, Neoplastic/drug effects
- Genes, cdc/drug effects
- Humans
- Inhibitory Concentration 50
- Leukemia, Lymphoid/genetics
- Leukemia, Lymphoid/metabolism
- Leukemia, Lymphoid/pathology
- Mice
- Neoplasm Proteins/genetics
- Neoplasm Proteins/metabolism
- Protease Inhibitors/pharmacology
- Proteasome Endopeptidase Complex/drug effects
- Proteasome Endopeptidase Complex/metabolism
- RNA, Messenger/biosynthesis
- RNA, Neoplasm/biosynthesis
- Recombinant Proteins/metabolism
- Transcription, Genetic/drug effects
- Ubiquitinated Proteins/metabolism
- Vincristine/pharmacology
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Affiliation(s)
- Tomáš Kyca
- Institute of Molecular Physiology and Genetics, Centre of Biosciences, Slovak Academy of Sciences, Dúbravská cesta 9, 84505 Bratislava, Slovakia; (T.K.); (L.P.); (V.B.); (A.P.)
| | - Lucia Pavlíková
- Institute of Molecular Physiology and Genetics, Centre of Biosciences, Slovak Academy of Sciences, Dúbravská cesta 9, 84505 Bratislava, Slovakia; (T.K.); (L.P.); (V.B.); (A.P.)
- Institute of Zoology, Slovak Academy of Sciences, Dúbravská cesta 9, 84506 Bratislava, Slovakia
| | - Viera Boháčová
- Institute of Molecular Physiology and Genetics, Centre of Biosciences, Slovak Academy of Sciences, Dúbravská cesta 9, 84505 Bratislava, Slovakia; (T.K.); (L.P.); (V.B.); (A.P.)
| | - Anton Mišák
- Institute for Clinical and Translational Research, Biomedical Research Center, Slovak Academy of Sciences, Dúbravská cesta 9, 84505 Bratislava, Slovakia;
| | - Alexandra Poturnayová
- Institute of Molecular Physiology and Genetics, Centre of Biosciences, Slovak Academy of Sciences, Dúbravská cesta 9, 84505 Bratislava, Slovakia; (T.K.); (L.P.); (V.B.); (A.P.)
| | - Albert Breier
- Institute of Molecular Physiology and Genetics, Centre of Biosciences, Slovak Academy of Sciences, Dúbravská cesta 9, 84505 Bratislava, Slovakia; (T.K.); (L.P.); (V.B.); (A.P.)
- Institute of Biochemistry and Microbiology, Faculty of Chemical and Food Technology, Slovak University of Technology in Bratislava, Radlinského 9, 81237 Bratislava 1, Slovakia
- Correspondence: (A.B.); (Z.S.); (M.Š.); Tel.: +421-2-593-25-514 or +421-918-674-514 (A.B.); +421-2-3229-5510 (Z.S.)
| | - Zdena Sulová
- Institute of Molecular Physiology and Genetics, Centre of Biosciences, Slovak Academy of Sciences, Dúbravská cesta 9, 84505 Bratislava, Slovakia; (T.K.); (L.P.); (V.B.); (A.P.)
- Correspondence: (A.B.); (Z.S.); (M.Š.); Tel.: +421-2-593-25-514 or +421-918-674-514 (A.B.); +421-2-3229-5510 (Z.S.)
| | - Mário Šereš
- Institute of Molecular Physiology and Genetics, Centre of Biosciences, Slovak Academy of Sciences, Dúbravská cesta 9, 84505 Bratislava, Slovakia; (T.K.); (L.P.); (V.B.); (A.P.)
- Institute of Zoology, Slovak Academy of Sciences, Dúbravská cesta 9, 84506 Bratislava, Slovakia
- Correspondence: (A.B.); (Z.S.); (M.Š.); Tel.: +421-2-593-25-514 or +421-918-674-514 (A.B.); +421-2-3229-5510 (Z.S.)
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Proteasome in action: substrate degradation by the 26S proteasome. Biochem Soc Trans 2021; 49:629-644. [PMID: 33729481 PMCID: PMC8106498 DOI: 10.1042/bst20200382] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Revised: 02/22/2021] [Accepted: 02/25/2021] [Indexed: 12/16/2022]
Abstract
Ubiquitination is the major criteria for the recognition of a substrate-protein by the 26S proteasome. Additionally, a disordered segment on the substrate — either intrinsic or induced — is critical for proteasome engagement. The proteasome is geared to interact with both of these substrate features and prepare it for degradation. To facilitate substrate accessibility, resting proteasomes are characterised by a peripheral distribution of ubiquitin receptors on the 19S regulatory particle (RP) and a wide-open lateral surface on the ATPase ring. In this substrate accepting state, the internal channel through the ATPase ring is discontinuous, thereby obstructing translocation of potential substrates. The binding of the conjugated ubiquitin to the ubiquitin receptors leads to contraction of the 19S RP. Next, the ATPases engage the substrate at a disordered segment, energetically unravel the polypeptide and translocate it towards the 20S catalytic core (CP). In this substrate engaged state, Rpn11 is repositioned at the pore of the ATPase channel to remove remaining ubiquitin modifications and accelerate translocation. C-termini of five of the six ATPases insert into corresponding lysine-pockets on the 20S α-ring to complete 20S CP gate opening. In the resulting substrate processing state, the ATPase channel is fully contiguous with the translocation channel into the 20S CP, where the substrate is proteolyzed. Complete degradation of a typical ubiquitin-conjugate takes place over a few tens of seconds while hydrolysing tens of ATP molecules in the process (50 kDa/∼50 s/∼80ATP). This article reviews recent insight into biochemical and structural features that underlie substrate recognition and processing by the 26S proteasome.
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Zhu W, Li J, Zhang Y, Zhu Z, Liu H, Lin Y, Hu A, Zhou J, Ren H, Shi X. Inhibition of HMGB1 Suppresses Hepatocellular Carcinoma Progression via HIPK2-Mediated Autophagic Degradation of ZEB1. Front Oncol 2021; 11:599124. [PMID: 33747917 PMCID: PMC7969871 DOI: 10.3389/fonc.2021.599124] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Accepted: 01/11/2021] [Indexed: 12/29/2022] Open
Abstract
Autophagy is a conserved catabolic process maintaining cellular homeostasis and reportedly plays a critical role in tumor progression. Accumulating data show that autophagic activity is inhibited in hepatocellular carcinoma. However, the underlying molecular basis of impaired autophagy in HCC remains unclear. In this study, we revealed that autophagic activity was suppressed by HMGB1 in a HIPK2-dependent way. Targeting HMGB1 could inhibit the degradation of HIPK2, as a result of which, autophagic degradation of ZEB1 was enhanced by reprogramming glucose metabolism/AMPK/mTOR axis. Moreover, we demonstrated that selectively degradation of ZEB1 was responsible for HCC growth inhibition in HMGB1 deficient cells. Lastly, we found the combination therapy of HMGB1 inhibitor and rapamycin achieved a better anti-HCC effect. These results demonstrate that impaired autophagy is controlled by HMGB1 and targeting HMGB1 could suppress HCC progression via HIPK2-mediated autophagic degradation of ZEB1.
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Affiliation(s)
- Wei Zhu
- Department of Anesthesiology, Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing, China
| | - Jun Li
- Department of General Surgery, The First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Yuheng Zhang
- Department of Hepatobiliary Surgery, Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing, China
| | - Zhengyi Zhu
- Department of Hepatobiliary Surgery, Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing, China
| | - Hanyi Liu
- Department of Hepatobiliary Surgery, Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing, China
| | - Yunzhen Lin
- Department of Hepatobiliary Surgery, Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing, China
| | - Anyin Hu
- Department of Hepatobiliary Surgery, Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing, China
| | - Jingchao Zhou
- Department of Hepatobiliary Surgery, Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing, China
| | - Haozhen Ren
- Department of Hepatobiliary Surgery, Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing, China
| | - Xiaolei Shi
- Department of Hepatobiliary Surgery, Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing, China
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Cascio P. PA28γ: New Insights on an Ancient Proteasome Activator. Biomolecules 2021; 11:228. [PMID: 33562807 PMCID: PMC7915322 DOI: 10.3390/biom11020228] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2021] [Revised: 02/02/2021] [Accepted: 02/03/2021] [Indexed: 02/06/2023] Open
Abstract
PA28 (also known as 11S, REG or PSME) is a family of proteasome regulators whose members are widely present in many of the eukaryotic supergroups. In jawed vertebrates they are represented by three paralogs, PA28α, PA28β, and PA28γ, which assemble as heptameric hetero (PA28αβ) or homo (PA28γ) rings on one or both extremities of the 20S proteasome cylindrical structure. While they share high sequence and structural similarities, the three isoforms significantly differ in terms of their biochemical and biological properties. In fact, PA28α and PA28β seem to have appeared more recently and to have evolved very rapidly to perform new functions that are specifically aimed at optimizing the process of MHC class I antigen presentation. In line with this, PA28αβ favors release of peptide products by proteasomes and is particularly suited to support adaptive immune responses without, however, affecting hydrolysis rates of protein substrates. On the contrary, PA28γ seems to be a slow-evolving gene that is most similar to the common ancestor of the PA28 activators family, and very likely retains its original functions. Notably, PA28γ has a prevalent nuclear localization and is involved in the regulation of several essential cellular processes including cell growth and proliferation, apoptosis, chromatin structure and organization, and response to DNA damage. In striking contrast with the activity of PA28αβ, most of these diverse biological functions of PA28γ seem to depend on its ability to markedly enhance degradation rates of regulatory protein by 20S proteasome. The present review will focus on the molecular mechanisms and biochemical properties of PA28γ, which are likely to account for its various and complex biological functions and highlight the common features with the PA28αβ paralog.
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Affiliation(s)
- Paolo Cascio
- Department of Veterinary Sciences, University of Turin, Largo P. Braccini 2, 10095 Grugliasco, Italy
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Structural Insights into Substrate Recognition and Processing by the 20S Proteasome. Biomolecules 2021; 11:biom11020148. [PMID: 33498876 PMCID: PMC7910952 DOI: 10.3390/biom11020148] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2021] [Revised: 01/18/2021] [Accepted: 01/21/2021] [Indexed: 12/12/2022] Open
Abstract
Four decades of proteasome research have yielded extensive information on ubiquitin-dependent proteolysis. The archetype of proteasomes is a 20S barrel-shaped complex that does not rely on ubiquitin as a degradation signal but can degrade substrates with a considerable unstructured stretch. Since roughly half of all proteasomes in most eukaryotic cells are free 20S complexes, ubiquitin-independent protein degradation may coexist with ubiquitin-dependent degradation by the highly regulated 26S proteasome. This article reviews recent advances in our understanding of the biochemical and structural features that underlie the proteolytic mechanism of 20S proteasomes. The two outer α-rings of 20S proteasomes provide a number of potential docking sites for loosely folded polypeptides. The binding of a substrate can induce asymmetric conformational changes, trigger gate opening, and initiate its own degradation through a protease-driven translocation mechanism. Consequently, the substrate translocates through two additional narrow apertures augmented by the β-catalytic active sites. The overall pulling force through the two annuli results in a protease-like unfolding of the substrate and subsequent proteolysis in the catalytic chamber. Although both proteasomes contain identical β-catalytic active sites, the differential translocation mechanisms yield distinct peptide products. Nonoverlapping substrate repertoires and product outcomes rationalize cohabitation of both proteasome complexes in cells.
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