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Frachon N, Demaretz S, Seaayfan E, Chelbi L, Bakhos-Douaihy D, Laghmani K. AUP1 Regulates the Endoplasmic Reticulum-Associated Degradation and Polyubiquitination of NKCC2. Cells 2024; 13:389. [PMID: 38474353 DOI: 10.3390/cells13050389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2024] [Revised: 01/30/2024] [Accepted: 02/22/2024] [Indexed: 03/14/2024] Open
Abstract
Inactivating mutations of kidney Na-K-2Cl cotransporter NKCC2 lead to antenatal Bartter syndrome (BS) type 1, a life-threatening salt-losing tubulopathy. We previously reported that this serious inherited renal disease is linked to the endoplasmic reticulum-associated degradation (ERAD) pathway. The purpose of this work is to characterize further the ERAD machinery of NKCC2. Here, we report the identification of ancient ubiquitous protein 1 (AUP1) as a novel interactor of NKCC2 ER-resident form in renal cells. AUP1 is also an interactor of the ER lectin OS9, a key player in the ERAD of NKCC2. Similar to OS9, AUP1 co-expression decreased the amount of total NKCC2 protein by enhancing the ER retention and associated protein degradation of the cotransporter. Blocking the ERAD pathway with the proteasome inhibitor MG132 or the α-mannosidase inhibitor kifunensine fully abolished the AUP1 effect on NKCC2. Importantly, AUP1 knock-down or inhibition by overexpressing its dominant negative form strikingly decreased NKCC2 polyubiquitination and increased the protein level of the cotransporter. Interestingly, AUP1 co-expression produced a more profound impact on NKCC2 folding mutants. Moreover, AUP1 also interacted with the related kidney cotransporter NCC and downregulated its expression, strongly indicating that AUP1 is a common regulator of sodium-dependent chloride cotransporters. In conclusion, our data reveal the presence of an AUP1-mediated pathway enhancing the polyubiquitination and ERAD of NKCC2. The characterization and selective regulation of specific ERAD constituents of NKCC2 and its pathogenic mutants could open new avenues in the therapeutic strategies for type 1 BS treatment.
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Affiliation(s)
- Nadia Frachon
- Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, F-75006 Paris, France
- CNRS, ERL8228, F-75006 Paris, France
| | - Sylvie Demaretz
- Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, F-75006 Paris, France
- CNRS, ERL8228, F-75006 Paris, France
| | - Elie Seaayfan
- Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, F-75006 Paris, France
- CNRS, ERL8228, F-75006 Paris, France
| | - Lydia Chelbi
- Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, F-75006 Paris, France
- CNRS, ERL8228, F-75006 Paris, France
| | - Dalal Bakhos-Douaihy
- Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, F-75006 Paris, France
- CNRS, ERL8228, F-75006 Paris, France
| | - Kamel Laghmani
- Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, F-75006 Paris, France
- CNRS, ERL8228, F-75006 Paris, France
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2
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Bai YT, Wang X, He MJ, Xie JR, Chen XJ, Zhou G. The Potential of Lipid Droplet-associated Genes as Diagnostic and Prognostic Biomarkers in Head and Neck Squamous Cell Carcinoma. Comb Chem High Throughput Screen 2024; 27:136-147. [PMID: 36998140 DOI: 10.2174/1386207326666230328123223] [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: 11/18/2022] [Revised: 01/18/2023] [Accepted: 01/18/2023] [Indexed: 04/01/2023]
Abstract
OBJECTIVE The role of lipid droplets (LDs) and lipid droplet-associated genes (LD-AGs) remains unclear in head and neck squamous cell carcinoma (HNSCC). This study aimed to investigate LDs in HNSCC and identify LD-AGs essential for the diagnosis and prognosis of HNSCC patients. METHODS The LDs in the HNSCC and normal cell lines were stained with oil red O. Bioinformatic analysis was used to find LD-AGs in HNSCC that had diagnostic and prognostic significance. RESULTS LDs accumulation was increased in HNSCC cell lines compared with normal cell lines (P<0.05). Fifty-three differentially expressed genes, including 34 upregulated and 19 downregulated, were found in HNSCC based on the TCGA platform (P<0.05). Then, 53 genes were proved to be functionally enriched in lipid metabolism and LDs. Among them, with an AUC value > 0.7, 34 genes demonstrated a high predictive power. Six genes (AUP1, CAV1, CAV2, CAVIN1, HILPDA, and SQLE) out of 34 diagnostic genes were linked to overall survival in patients with HNSCC (P<0.05). The significant prognostic factors AUP1, CAV1, CAV2, and SQLE were further identified using the univariate and multivariate cox proportional hazard models (P<0.05). The protein expression of CAV2 and SQLE was significantly increased in the HNSCC tissue compared to normal tissues (P<0.05). Finally, the knockdown of the four LD-AGs decreased LDs accumulation, respectively. CONCLUSIONS Increased LDs accumulation was a hallmark of HNSCC, and AUP1, CAV1, CAV2, and SQLE were discovered as differentially expressed LD-AGs with diagnostic and prognostic potential in HNSCC.
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Affiliation(s)
- Yu-Ting Bai
- The State Key Laboratory Breeding Base of Basic Science of Stomatology (Hubei-MOST) and Key Laboratory of Oral Biomedicine Ministry of Education, School and Hospital of Stomatology, Wuhan University, Wuhan, Hubei Province, China
| | - Xin Wang
- The State Key Laboratory Breeding Base of Basic Science of Stomatology (Hubei-MOST) and Key Laboratory of Oral Biomedicine Ministry of Education, School and Hospital of Stomatology, Wuhan University, Wuhan, Hubei Province, China
| | - Ming-Jing He
- The State Key Laboratory Breeding Base of Basic Science of Stomatology (Hubei-MOST) and Key Laboratory of Oral Biomedicine Ministry of Education, School and Hospital of Stomatology, Wuhan University, Wuhan, Hubei Province, China
- Department of Oral Medicine, School and Hospital of Stomatology, Wuhan University, Wuhan, Hubei Province, China
| | - Ji-Rong Xie
- The State Key Laboratory Breeding Base of Basic Science of Stomatology (Hubei-MOST) and Key Laboratory of Oral Biomedicine Ministry of Education, School and Hospital of Stomatology, Wuhan University, Wuhan, Hubei Province, China
| | - Xiao-Jie Chen
- The State Key Laboratory Breeding Base of Basic Science of Stomatology (Hubei-MOST) and Key Laboratory of Oral Biomedicine Ministry of Education, School and Hospital of Stomatology, Wuhan University, Wuhan, Hubei Province, China
- Department of Oral Medicine, School and Hospital of Stomatology, Wuhan University, Wuhan, Hubei Province, China
| | - Gang Zhou
- The State Key Laboratory Breeding Base of Basic Science of Stomatology (Hubei-MOST) and Key Laboratory of Oral Biomedicine Ministry of Education, School and Hospital of Stomatology, Wuhan University, Wuhan, Hubei Province, China
- Department of Oral Medicine, School and Hospital of Stomatology, Wuhan University, Wuhan, Hubei Province, China
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3
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Yang M, Mariano J, Su R, Smith CE, Das S, Gill C, Andresson T, Loncarek J, Tsai YC, Weissman AM. SARS-CoV-2 papain-like protease plays multiple roles in regulating cellular proteins in the endoplasmic reticulum. J Biol Chem 2023; 299:105346. [PMID: 37838170 PMCID: PMC10692909 DOI: 10.1016/j.jbc.2023.105346] [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: 05/30/2023] [Revised: 10/01/2023] [Accepted: 10/03/2023] [Indexed: 10/16/2023] Open
Abstract
Nsp3s are the largest nonstructural proteins of coronaviruses. These transmembrane proteins include papain-like proteases (PLpro) that play essential roles in cleaving viral polyproteins into their mature units. The PLpro of SARS-CoV viruses also have deubiquitinating and deISGylating activities. As Nsp3 is an endoplasmic reticulum (ER)-localized protein, we asked if the deubiquitinating activity of SARS-CoV-2 PLpro affects proteins that are substrates for ER-associated degradation (ERAD). Using full-length Nsp3 as well as a truncated transmembrane form we interrogated, by coexpression, three potential ERAD substrates, all of which play roles in regulating lipid biosynthesis. Transmembrane PLpro increases the level of INSIG-1 and decreases its ubiquitination. However, different effects were seen with SREBP-1 and SREBP-2. Transmembrane PLpro cleaves SREBP-1 at three sites, including two noncanonical sites in the N-terminal half of the protein, resulting in a decrease in precursors of the active transcription factor. Conversely, cleavage of SREBP-2 occurs at a single canonical site that disrupts a C-terminal degron, resulting in increased SREBP-2 levels. When this site is mutated and the degron can no longer be interrupted, SREBP-2 is still stabilized by transmembrane PLpro, which correlates with a decrease in SREBP-2 ubiquitination. All of these observations are dependent on PLpro catalytic activity. Our findings demonstrate that, when anchored to the ER membrane, SARS-CoV-2 Nsp3 PLpro can function as a deubiquitinating enzyme to stabilize ERAD substrates. Additionally, SARS-CoV-2 Nsp3 PLpro can cleave ER-resident proteins, including at sites that could escape analyses based on the established consensus sequence.
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Affiliation(s)
- Mei Yang
- Cancer Innovation Laboratory, Center for Cancer Research, National Institutes of Health, Frederick, Maryland, USA
| | - Jennifer Mariano
- Cancer Innovation Laboratory, Center for Cancer Research, National Institutes of Health, Frederick, Maryland, USA
| | - Rebecca Su
- Cancer Innovation Laboratory, Center for Cancer Research, National Institutes of Health, Frederick, Maryland, USA
| | - Christopher E Smith
- Cancer Innovation Laboratory, Center for Cancer Research, National Institutes of Health, Frederick, Maryland, USA
| | - Sudipto Das
- Protein Characterization Laboratory, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, Maryland, USA
| | - Catherine Gill
- Cancer Innovation Laboratory, Center for Cancer Research, National Institutes of Health, Frederick, Maryland, USA
| | - Thorkell Andresson
- Protein Characterization Laboratory, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, Maryland, USA
| | - Jadranka Loncarek
- Cancer Innovation Laboratory, Center for Cancer Research, National Institutes of Health, Frederick, Maryland, USA
| | - Yien Che Tsai
- Cancer Innovation Laboratory, Center for Cancer Research, National Institutes of Health, Frederick, Maryland, USA
| | - Allan M Weissman
- Cancer Innovation Laboratory, Center for Cancer Research, National Institutes of Health, Frederick, Maryland, USA.
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Christianson JC, Jarosch E, Sommer T. Mechanisms of substrate processing during ER-associated protein degradation. Nat Rev Mol Cell Biol 2023; 24:777-796. [PMID: 37528230 DOI: 10.1038/s41580-023-00633-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/20/2023] [Indexed: 08/03/2023]
Abstract
Maintaining proteome integrity is essential for long-term viability of all organisms and is overseen by intrinsic quality control mechanisms. The secretory pathway of eukaryotes poses a challenge for such quality assurance as proteins destined for secretion enter the endoplasmic reticulum (ER) and become spatially segregated from the cytosolic machinery responsible for disposal of aberrant (misfolded or otherwise damaged) or superfluous polypeptides. The elegant solution provided by evolution is ER-membrane-bound ubiquitylation machinery that recognizes misfolded or surplus proteins or by-products of protein biosynthesis in the ER and delivers them to 26S proteasomes for degradation. ER-associated protein degradation (ERAD) collectively describes this specialized arm of protein quality control via the ubiquitin-proteasome system. But, instead of providing a single strategy to remove defective or unwanted proteins, ERAD represents a collection of independent processes that exhibit distinct yet overlapping selectivity for a wide range of substrates. Not surprisingly, ER-membrane-embedded ubiquitin ligases (ER-E3s) act as central hubs for each of these separate ERAD disposal routes. In these processes, ER-E3s cooperate with a plethora of specialized factors, coordinating recognition, transport and ubiquitylation of undesirable secretory, membrane and cytoplasmic proteins. In this Review, we focus on substrate processing during ERAD, highlighting common threads as well as differences between the many routes via ERAD.
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Affiliation(s)
- John C Christianson
- Botnar Research Centre, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, UK.
| | - Ernst Jarosch
- Max-Delbrück-Centrer for Molecular Medicine in Helmholtz Association, Berlin-Buch, Germany
| | - Thomas Sommer
- Max-Delbrück-Centrer for Molecular Medicine in Helmholtz Association, Berlin-Buch, Germany.
- Institute for Biology, Humboldt Universität zu Berlin, Berlin, Germany.
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5
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Aguilan JT, Pedrosa E, Dolstra H, Baykara RN, Barnes J, Zhang J, Sidoli S, Lachman HM. Proteomics and phosphoproteomics profiling in glutamatergic neurons and microglia in an iPSC model of Jansen de Vries Syndrome. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.08.548192. [PMID: 37461463 PMCID: PMC10350077 DOI: 10.1101/2023.07.08.548192] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 07/25/2023]
Abstract
Background Jansen de Vries Syndrome (JdVS) is a rare neurodevelopmental disorder (NDD) caused by gain-of-function (GOF) truncating mutations in PPM1D exons 5 or 6. PPM1D is a serine/threonine phosphatase that plays an important role in the DNA damage response (DDR) by negatively regulating TP53 (P53). JdVS-associated mutations lead to the formation of a truncated PPM1D protein that retains catalytic activity and has a GOF effect because of reduced degradation. Somatic PPM1D exons 5 and 6 truncating mutations are well-established factors in a number of cancers, due to excessive dephosphorylation and reduced function of P53 and other substrates involved in DDR. Children with JdVS have a variety of neurodevelopmental, psychiatric, and physical problems. In addition, a small fraction has acute neuropsychiatric decompensation apparently triggered by infection or severe non-infectious environmental stress factors. Methods To understand the molecular basis of JdVS, we developed an induced pluripotent stem cell (iPSC) model system. iPSCs heterozygous for the truncating variant (PPM1D+/tr), were made from a patient, and control lines engineered using CRISPR-Cas9 gene editing. Proteomics and phosphoprotemics analyses were carried out on iPSC-derived glutamatergic neurons and microglia from three control and three PPM1D+/tr iPSC lines. We also analyzed the effect of the TLR4 agonist, lipopolysaccharide, to understand how activation of the innate immune system in microglia could account for acute behavioral decompensation. Results One of the major findings was the downregulation of POGZ in unstimulated microglia. Since loss-of-function variants in the POGZ gene are well-known causes of autism spectrum disorder, the decrease in PPM1D+/tr microglia suggests this plays a role in the neurodevelopmental aspects of JdVS. In addition, neurons, baseline, and LPS-stimulated microglia show marked alterations in the expression of several E3 ubiquitin ligases, most notably UBR4, and regulators of innate immunity, chromatin structure, ErbB signaling, and splicing. In addition, pathway analysis points to overlap with neurodegenerative disorders. Limitations Owing to the cost and labor-intensive nature of iPSC research, the sample size was small. Conclusions Our findings provide insight into the molecular basis of JdVS and can be extrapolated to understand neuropsychiatric decompensation that occurs in subgroups of patients with ASD and other NDDs.
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Affiliation(s)
- Jennifer T. Aguilan
- Department of Pathology, Albert Einstein College of Medicine, 1300 Morris Park Ave. Bronx, NY, 10461
| | - Erika Pedrosa
- Department of Psychiatry and Behavioral Sciences, Albert Einstein College of Medicine, 1300 Morris Park Ave. Bronx, NY, 10461
| | - Hedwig Dolstra
- Department of Psychiatry and Behavioral Sciences, Albert Einstein College of Medicine, 1300 Morris Park Ave. Bronx, NY, 10461
| | - Refia Nur Baykara
- Department of Psychiatry and Behavioral Sciences, Albert Einstein College of Medicine, 1300 Morris Park Ave. Bronx, NY, 10461
| | - Jesse Barnes
- Department of Psychiatry and Behavioral Sciences, Albert Einstein College of Medicine, 1300 Morris Park Ave. Bronx, NY, 10461
| | - Jinghang Zhang
- Department of Microbiology & Immunology, Albert Einstein College of Medicine, 1300 Morris Park Ave. Bronx, NY, 10461
| | - Simone Sidoli
- Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Ave. Bronx, NY, 10461
| | - Herbert M. Lachman
- Department of Psychiatry and Behavioral Sciences, Albert Einstein College of Medicine, 1300 Morris Park Ave. Bronx, NY, 10461
- Department of Medicine, Albert Einstein College of Medicine, 1300 Morris Park Ave. Bronx, NY, 10461
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, 1300 Morris Park Ave. Bronx, NY, 10461
- Department of Genetics, Albert Einstein College of Medicine, 1300 Morris Park Ave. Bronx, NY, 10461
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6
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Badawi S, Mohamed FE, Varghese DS, Ali BR. Genetic disruption of mammalian endoplasmic reticulum-associated protein degradation: Human phenotypes and animal and cellular disease models. Traffic 2023. [PMID: 37188482 DOI: 10.1111/tra.12902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Revised: 04/28/2023] [Accepted: 05/02/2023] [Indexed: 05/17/2023]
Abstract
Endoplasmic reticulum-associated protein degradation (ERAD) is a stringent quality control mechanism through which misfolded, unassembled and some native proteins are targeted for degradation to maintain appropriate cellular and organelle homeostasis. Several in vitro and in vivo ERAD-related studies have provided mechanistic insights into ERAD pathway activation and its consequent events; however, a majority of these have investigated the effect of ERAD substrates and their consequent diseases affecting the degradation process. In this review, we present all reported human single-gene disorders caused by genetic variation in genes that encode ERAD components rather than their substrates. Additionally, after extensive literature survey, we present various genetically manipulated higher cellular and mammalian animal models that lack specific components involved in various stages of the ERAD pathway.
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Affiliation(s)
- Sally Badawi
- Department of Genetics and Genomics, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Feda E Mohamed
- Department of Genetics and Genomics, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Divya Saro Varghese
- Department of Genetics and Genomics, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Bassam R Ali
- Department of Genetics and Genomics, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
- ASPIRE Precision Medicine Research Institute Abu Dhabi, United Arab Emirates University, Al Ain, United Arab Emirates
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7
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Lan Y, van Leur SW, Fernando JA, Wong HH, Kampmann M, Siu L, Zhang J, Li M, Nicholls JM, Sanyal S. Viral subversion of selective autophagy is critical for biogenesis of virus replication organelles. Nat Commun 2023; 14:2698. [PMID: 37164963 PMCID: PMC10171163 DOI: 10.1038/s41467-023-38377-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 04/25/2023] [Indexed: 05/12/2023] Open
Abstract
Infection by many (+)RNA viruses is accompanied by ER-expansion and membrane remodelling to form viral replication organelles, followed by assembly and secretion of viral progenies. We previously identified that virus-triggered lipophagy was critical for flaviviral assembly, and is driven by the lipid droplet associated protein Ancient ubiquitin protein 1 (Aup1). A ubiquitin conjugating protein Ube2g2 that functions as a co-factor for Aup1 was identified as a host dependency factor in our study. Here we characterized its function: Ube2g2-deficient cells displayed a dramatic reduction in virus production, which could be rescued by reconstituting the wild-type but not the catalytically deficient (C89K) mutant of Ube2g2, suggesting that its enzymatic activity is necessary. Ube2g2 deficiency did not affect entry of virus particles but resulted in a profound loss in formation of replication organelles, and production of infectious progenies. This phenomenon resulted from its dual activity in (i) triggering lipophagy in conjunction with Aup1, and (ii) degradation of ER chaperones such as Herpud1, SEL1L, Hrd1, along with Sec62 to restrict ER-phagy upon Xbp1-IRE1 triggered ER expansion. Our results therefore underscore an exquisite fine-tuning of selective autophagy by flaviviruses that drive host membrane reorganization during infection to enable biogenesis of viral replication organelles.
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Affiliation(s)
- Yun Lan
- HKU-Pasteur Research Pole, School of Public Health, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong SAR, China
| | | | - Julia Ayano Fernando
- HKU-Pasteur Research Pole, School of Public Health, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong SAR, China
| | - Ho Him Wong
- HKU-Pasteur Research Pole, School of Public Health, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong SAR, China
| | - Martin Kampmann
- HKU-Pasteur Research Pole, School of Public Health, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong SAR, China
| | - Lewis Siu
- HKU-Pasteur Research Pole, School of Public Health, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong SAR, China
| | - Jingshu Zhang
- HKU-Pasteur Research Pole, School of Public Health, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong SAR, China
| | - Mingyuan Li
- HKU-Pasteur Research Pole, School of Public Health, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong SAR, China
| | - John M Nicholls
- Department of Pathology, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong SAR, China
| | - Sumana Sanyal
- HKU-Pasteur Research Pole, School of Public Health, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong SAR, China.
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford, OX1 3RE, UK.
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8
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Mehrtash AB, Hochstrasser M. Elements of the ERAD ubiquitin ligase Doa10 regulating sequential poly-ubiquitylation of its targets. iScience 2022; 25:105351. [PMID: 36325070 PMCID: PMC9619350 DOI: 10.1016/j.isci.2022.105351] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Revised: 08/16/2022] [Accepted: 10/11/2022] [Indexed: 11/29/2022] Open
Abstract
In ER-associated degradation (ERAD), misfolded ER proteins are degraded by the proteasome after undergoing ubiquitylation. Yeast Doa10 (human MARCHF6/TEB4) is a membrane-embedded E3 ubiquitin ligase that functions with E2s Ubc6 and Ubc7. Ubc6 attaches a single ubiquitin to substrates, which is extended by Ubc7 to form a polyubiquitin chain. We show the conserved C-terminal element (CTE) of Doa10 promotes E3-mediated Ubc6 activity. Doa10 substrates undergoing an alternative ubiquitylation mechanism are still degraded in CTE-mutant cells. Structure prediction by AlphaFold2 suggests the CTE binds near the catalytic RING-CH domain, implying a direct role in substrate ubiquitylation, and we confirm this interaction using intragenic suppression. Truncation analysis defines a minimal E2-binding region of Doa10; structural predictions suggest that Doa10 forms a retrotranslocation channel and that E2s bind within the cofactor-binding region defined here. These results provide mechanistic insight into how Doa10, and potentially other ligases, interact with their cofactors and mediate ERAD. The conserved Doa10 C-terminus promotes E3-mediated activity of Ubc6 The minimal E2-binding region of Doa10 includes TMs 1–9 The N- and C-terminus of Doa10 interact, likely forming an ERAD protein channel
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Affiliation(s)
- Adrian B. Mehrtash
- Department of Molecular, Cellular, & Developmental Biology, Yale University, New Haven, 06520 CT, USA
| | - Mark Hochstrasser
- Department of Molecular, Cellular, & Developmental Biology, Yale University, New Haven, 06520 CT, USA
- Department of Molecular Biophysics & Biochemistry, Yale University, New Haven, CT 06520, USA
- Corresponding author
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