1
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Iwasa Y, Miyata S, Tomita T, Yokota N, Miyauchi M, Mori R, Matsushita S, Suzuki R, Saeki Y, Kawahara H. TanGIBLE: A selective probe for evaluating hydrophobicity-exposed defective proteins in live cells. J Cell Biol 2025; 224:e202109010. [PMID: 39812643 PMCID: PMC11734626 DOI: 10.1083/jcb.202109010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Revised: 08/22/2024] [Accepted: 11/26/2024] [Indexed: 01/16/2025] Open
Abstract
The accumulation of defective polypeptides in cells is a major cause of various diseases. However, probing defective proteins is difficult because no currently available method can retrieve unstable defective translational products in a soluble state. To overcome this issue, there is a need for a molecular device specific to structurally defective polypeptides. In this study, we developed an artificial protein architecture comprising tandemly aligned BAG6 Domain I, a minimum substrate recognition platform responsible for protein quality control. This tandem-aligned entity shows enhanced affinity not only for model defective polypeptides but also for endogenous polyubiquitinated proteins, which are sensitive to translational inhibition. Mass-spectrometry analysis with this probe enabled the identification of endogenous defective proteins, including orphaned subunits derived from multiprotein complexes and misassembled transmembrane proteins. This probe is also useful for the real-time visualization of protein foci derived from defective polypeptides in stressed cells. Therefore, this "new molecular trap" is a versatile tool for evaluating currently "invisible" pools of defective polypeptides as tangible entities.
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Affiliation(s)
- Yasuyuki Iwasa
- Department of Biological Sciences, Laboratory of Cell Biology and Biochemistry, Tokyo Metropolitan University, Tokyo, Japan
| | - Sohtaroh Miyata
- Department of Biological Sciences, Laboratory of Cell Biology and Biochemistry, Tokyo Metropolitan University, Tokyo, Japan
| | - Takuya Tomita
- Department of Protein Metabolism, Institute of Medical Science, The University of Tokyo, Tokyo, Japan
| | - Naoto Yokota
- Department of Biological Sciences, Laboratory of Cell Biology and Biochemistry, Tokyo Metropolitan University, Tokyo, Japan
| | - Maho Miyauchi
- Department of Biological Sciences, Laboratory of Cell Biology and Biochemistry, Tokyo Metropolitan University, Tokyo, Japan
| | - Ruka Mori
- Department of Biological Sciences, Laboratory of Cell Biology and Biochemistry, Tokyo Metropolitan University, Tokyo, Japan
| | - Shin Matsushita
- Department of Biological Sciences, Laboratory of Cell Biology and Biochemistry, Tokyo Metropolitan University, Tokyo, Japan
| | - Rigel Suzuki
- Department of Biological Sciences, Laboratory of Cell Biology and Biochemistry, Tokyo Metropolitan University, Tokyo, Japan
| | - Yasushi Saeki
- Department of Protein Metabolism, Institute of Medical Science, The University of Tokyo, Tokyo, Japan
| | - Hiroyuki Kawahara
- Department of Biological Sciences, Laboratory of Cell Biology and Biochemistry, Tokyo Metropolitan University, Tokyo, Japan
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2
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Hurła M, Pikor D, Banaszek-Hurła N, Drelichowska A, Dorszewska J, Kozubski W, Kacprzak E, Paul M. Unraveling the Role of Proteinopathies in Parasitic Infections. Biomedicines 2025; 13:610. [PMID: 40149586 PMCID: PMC11940292 DOI: 10.3390/biomedicines13030610] [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: 02/03/2025] [Revised: 02/26/2025] [Accepted: 02/27/2025] [Indexed: 03/29/2025] Open
Abstract
Proteinopathies, characterized by the misfolding, aggregation, and deposition of proteins, are hallmarks of various neurodegenerative and systemic diseases. Increasingly, research has highlighted the role of protein misfolding in parasitic infections, unveiling intricate interactions between host and parasite that exacerbate disease pathology and contribute to chronic outcomes. The life cycles of parasitic protozoa, including Plasmodium, Toxoplasmosis, and Leishmania species, are complicated and involve frequent changes between host and vector environments. Their proteomes are severely stressed during these transitions, which calls for highly specialized protein quality control systems. In order to survive harsh intracellular conditions during infection, these parasites have been demonstrated to display unique adaptations in the unfolded protein response, a crucial pathway controlling endoplasmic reticulum stress. In addition to improving parasite survival, these adaptations affect host cell signaling and metabolism, which may jeopardize cellular homeostasis. By causing oxidative stress, persistent inflammation, and disturbance of cellular proteostasis, host-parasite interactions also contribute to proteinopathy. For instance, Plasmodium falciparum disrupts normal protein homeostasis and encourages the accumulation of misfolded proteins by influencing host redox systems involved in protein folding. In addition to interfering with host chaperone systems, the parasitic secretion of effector proteins exacerbates protein misfolding and aggregate formation. Autophagy, apoptosis regulation, organelle integrity, and other vital cellular processes are all disrupted by these pathological protein aggregates. Long-term misfolding and aggregation can cause irreversible tissue damage, which can worsen the clinical course of illnesses like visceral leishmaniasis, cerebral malaria, and toxoplasmosis. Treating parasite-induced proteinopathies is a potentially fruitful area of therapy. According to recent research, autophagy modulators, proteasome enhancers, and small-molecule chaperones may be repurposed to lessen these effects. Pharmacological agents that target the UPR, for example, have demonstrated the ability to decrease parasite survival while also reestablishing host protein homeostasis. Targeting the proteins secreted by parasites that disrupt host proteostasis may also offer a novel way to stop tissue damage caused by proteinopathies. In conclusion, the intersection of protein misfolding and parasitic infections represents a rapidly advancing field of research. Dissecting the molecular pathways underpinning these processes offers unprecedented opportunities for developing innovative therapies. These insights could not only transform the management of parasitic diseases but also contribute to a broader understanding of proteinopathies in infectious and non-infectious diseases alike.
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Affiliation(s)
- Mikołaj Hurła
- Department of Tropical and Parasitic Diseases, Central University Hospital, Przybyszewskiego 49, 61-701 Poznan, Poland
| | - Damian Pikor
- Department of Internal Medicine, University of Medical Sciences, Przybyszewskiego 49, 60-355 Poznan, Poland
| | - Natalia Banaszek-Hurła
- Laboratory of Neurobiology, Department of Neurology, Poznan University of Medical Sciences, 60-355 Poznan, Poland
| | - Alicja Drelichowska
- Student Scientific Society of Poznan, University of Medical Sciences, 60-806 Poznan, Poland
| | - Jolanta Dorszewska
- Laboratory of Neurobiology, Department of Neurology, Poznan University of Medical Sciences, 60-355 Poznan, Poland
| | - Wojciech Kozubski
- Chair and Department of Neurology, Poznan University of Medical Sciences, 60-355 Poznan, Poland
| | - Elżbieta Kacprzak
- Department of Tropical and Parasitic Diseases, Central University Hospital, Przybyszewskiego 49, 61-701 Poznan, Poland
| | - Małgorzata Paul
- Department of Internal Medicine, University of Medical Sciences, Przybyszewskiego 49, 60-355 Poznan, Poland
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3
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Zhou Y, Li T, Zhang Y, Zhang N, Guo Y, Gao X, Peng W, Shu S, Zhao C, Cui D, Sun H, Sun Y, Liu J, Tang J, Zhang R, Pu J. BAG6 inhibits influenza A virus replication by inducing viral polymerase subunit PB2 degradation and perturbing RdRp complex assembly. PLoS Pathog 2024; 20:e1012110. [PMID: 38498560 PMCID: PMC10977894 DOI: 10.1371/journal.ppat.1012110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Revised: 03/28/2024] [Accepted: 03/09/2024] [Indexed: 03/20/2024] Open
Abstract
The interaction between influenza A virus (IAV) and host proteins is an important process that greatly influences viral replication and pathogenicity. PB2 protein is a subunit of viral ribonucleoprotein (vRNP) complex playing distinct roles in viral transcription and replication. BAG6 (BCL2-associated athanogene 6) as a multifunctional host protein participates in physiological and pathological processes. Here, we identify BAG6 as a new restriction factor for IAV replication through targeting PB2. For both avian and human influenza viruses, overexpression of BAG6 reduced viral protein expression and virus titers, whereas deletion of BAG6 significantly enhanced virus replication. Moreover, BAG6-knockdown mice developed more severe clinical symptoms and higher viral loads upon IAV infection. Mechanistically, BAG6 restricted IAV transcription and replication by inhibiting the activity of viral RNA-dependent RNA polymerase (RdRp). The co-immunoprecipitation assays showed BAG6 specifically interacted with the N-terminus of PB2 and competed with PB1 for RdRp complex assembly. The ubiquitination assay indicated that BAG6 promoted PB2 ubiquitination at K189 residue and targeted PB2 for K48-linked ubiquitination degradation. The antiviral effect of BAG6 necessitated its N-terminal region containing a ubiquitin-like (UBL) domain (17-92aa) and a PB2-binding domain (124-186aa), which are synergistically responsible for viral polymerase subunit PB2 degradation and perturbing RdRp complex assembly. These findings unravel a novel antiviral mechanism via the interaction of viral PB2 and host protein BAG6 during avian or human influenza virus infection and highlight a potential application of BAG6 for antiviral drug development.
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Affiliation(s)
- Yong Zhou
- National Key Laboratory of Veterinary Public Health and Safety, College of Veterinary Medicine, China Agricultural University, Beijing, China
- Key Laboratory for Prevention and Control of Avian Influenza and Other Major Poultry Diseases, Ministry of Agriculture and Rural Affairs, College of Veterinary Medicine, China Agricultural University, Beijing, China
- Department of Preventive Veterinary, College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Tian Li
- National Key Laboratory of Veterinary Public Health and Safety, College of Veterinary Medicine, China Agricultural University, Beijing, China
- Key Laboratory for Prevention and Control of Avian Influenza and Other Major Poultry Diseases, Ministry of Agriculture and Rural Affairs, College of Veterinary Medicine, China Agricultural University, Beijing, China
- Department of Preventive Veterinary, College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Yunfan Zhang
- National Key Laboratory of Veterinary Public Health and Safety, College of Veterinary Medicine, China Agricultural University, Beijing, China
- Department of Basic Veterinary, College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Nianzhi Zhang
- National Key Laboratory of Veterinary Public Health and Safety, College of Veterinary Medicine, China Agricultural University, Beijing, China
- Department of Preventive Veterinary, College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Yuxin Guo
- National Key Laboratory of Veterinary Public Health and Safety, College of Veterinary Medicine, China Agricultural University, Beijing, China
- Key Laboratory for Prevention and Control of Avian Influenza and Other Major Poultry Diseases, Ministry of Agriculture and Rural Affairs, College of Veterinary Medicine, China Agricultural University, Beijing, China
- Department of Preventive Veterinary, College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Xiaoyi Gao
- National Key Laboratory of Veterinary Public Health and Safety, College of Veterinary Medicine, China Agricultural University, Beijing, China
- Key Laboratory for Prevention and Control of Avian Influenza and Other Major Poultry Diseases, Ministry of Agriculture and Rural Affairs, College of Veterinary Medicine, China Agricultural University, Beijing, China
- Department of Preventive Veterinary, College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Wenjing Peng
- National Key Laboratory of Veterinary Public Health and Safety, College of Veterinary Medicine, China Agricultural University, Beijing, China
- Key Laboratory for Prevention and Control of Avian Influenza and Other Major Poultry Diseases, Ministry of Agriculture and Rural Affairs, College of Veterinary Medicine, China Agricultural University, Beijing, China
- Department of Preventive Veterinary, College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Sicheng Shu
- National Key Laboratory of Veterinary Public Health and Safety, College of Veterinary Medicine, China Agricultural University, Beijing, China
- Key Laboratory for Prevention and Control of Avian Influenza and Other Major Poultry Diseases, Ministry of Agriculture and Rural Affairs, College of Veterinary Medicine, China Agricultural University, Beijing, China
- Department of Preventive Veterinary, College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Chuankuo Zhao
- National Key Laboratory of Veterinary Public Health and Safety, College of Veterinary Medicine, China Agricultural University, Beijing, China
- Key Laboratory for Prevention and Control of Avian Influenza and Other Major Poultry Diseases, Ministry of Agriculture and Rural Affairs, College of Veterinary Medicine, China Agricultural University, Beijing, China
- Department of Preventive Veterinary, College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Di Cui
- National Key Laboratory of Veterinary Public Health and Safety, College of Veterinary Medicine, China Agricultural University, Beijing, China
- Department of Basic Veterinary, College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Honglei Sun
- National Key Laboratory of Veterinary Public Health and Safety, College of Veterinary Medicine, China Agricultural University, Beijing, China
- Key Laboratory for Prevention and Control of Avian Influenza and Other Major Poultry Diseases, Ministry of Agriculture and Rural Affairs, College of Veterinary Medicine, China Agricultural University, Beijing, China
- Department of Preventive Veterinary, College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Yipeng Sun
- National Key Laboratory of Veterinary Public Health and Safety, College of Veterinary Medicine, China Agricultural University, Beijing, China
- Key Laboratory for Prevention and Control of Avian Influenza and Other Major Poultry Diseases, Ministry of Agriculture and Rural Affairs, College of Veterinary Medicine, China Agricultural University, Beijing, China
- Department of Preventive Veterinary, College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Jinhua Liu
- National Key Laboratory of Veterinary Public Health and Safety, College of Veterinary Medicine, China Agricultural University, Beijing, China
- Key Laboratory for Prevention and Control of Avian Influenza and Other Major Poultry Diseases, Ministry of Agriculture and Rural Affairs, College of Veterinary Medicine, China Agricultural University, Beijing, China
- Department of Preventive Veterinary, College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Jun Tang
- National Key Laboratory of Veterinary Public Health and Safety, College of Veterinary Medicine, China Agricultural University, Beijing, China
- Department of Basic Veterinary, College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Rui Zhang
- National Key Laboratory of Veterinary Public Health and Safety, College of Veterinary Medicine, China Agricultural University, Beijing, China
- Department of Basic Veterinary, College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Juan Pu
- National Key Laboratory of Veterinary Public Health and Safety, College of Veterinary Medicine, China Agricultural University, Beijing, China
- Key Laboratory for Prevention and Control of Avian Influenza and Other Major Poultry Diseases, Ministry of Agriculture and Rural Affairs, College of Veterinary Medicine, China Agricultural University, Beijing, China
- Department of Preventive Veterinary, College of Veterinary Medicine, China Agricultural University, Beijing, China
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4
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Hagiwara T, Minami R, Ushio C, Yokota N, Kawahara H. Proteotoxic stresses stimulate dissociation of UBL4A from the tail-anchored protein recognition complex. Biochem J 2023; 480:1583-1598. [PMID: 37747814 PMCID: PMC10586765 DOI: 10.1042/bcj20230267] [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: 07/13/2023] [Revised: 09/21/2023] [Accepted: 09/25/2023] [Indexed: 09/27/2023]
Abstract
Inclusion body formation is associated with cytotoxicity in a number of neurodegenerative diseases. However, the molecular basis of the toxicity caused by the accumulation of aggregation-prone proteins remains controversial. In this study, we found that disease-associated inclusions induced by elongated polyglutamine chains disrupt the complex formation of BAG6 with UBL4A, a mammalian homologue of yeast Get5. UBL4A also dissociated from BAG6 in response to proteotoxic stresses such as proteasomal inhibition and mitochondrial depolarization. These findings imply that the cytotoxicity of pathological protein aggregates might be attributed in part to disruption of the BAG6-UBL4A complex that is required for the biogenesis of tail-anchored proteins.
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Affiliation(s)
- Takumi Hagiwara
- Department of Biological Sciences, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Ryosuke Minami
- Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan
| | - Chizuru Ushio
- Department of Biological Sciences, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Naoto Yokota
- Department of Biological Sciences, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Hiroyuki Kawahara
- Department of Biological Sciences, Tokyo Metropolitan University, Tokyo 192-0397, Japan
- Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan
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5
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Takahashi T, Shirai J, Matsuda M, Nakanaga S, Matsushita S, Wakita K, Hayashishita M, Suzuki R, Noguchi A, Yokota N, Kawahara H. Protein quality control machinery supports primary ciliogenesis by eliminating GDP-bound Rab8-family GTPases. iScience 2023; 26:106652. [PMID: 37182096 PMCID: PMC10173616 DOI: 10.1016/j.isci.2023.106652] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Revised: 02/27/2023] [Accepted: 04/06/2023] [Indexed: 05/16/2023] Open
Abstract
The small GTPase Rab8 plays a vital role in the vesicular trafficking of cargo proteins from the trans-Golgi network to target membranes. Upon reaching its target destination, Rab8 is released from the vesicular membrane into the cytoplasm via guanosine triphosphate (GTP) hydrolysis. The fate of GDP-bound Rab8 released from the destination membranes, however, has not been investigated adequately. In this study, we found that GDP-bound Rab8 subfamily proteins are targeted for immediate degradation, and the pre-emptive quality control machinery is responsible for eliminating these proteins in a nucleotide-specific manner. We provide evidence that components of this quality control machinery have a critical role in vesicular trafficking events, including the formation of primary cilia, a process regulated by the Rab8 subfamily. These results suggest that the protein degradation machinery plays a critical role in the integrity of membrane trafficking by limiting the excessive accumulation of GDP-bound Rab8 subfamily proteins.
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Affiliation(s)
- Toshiki Takahashi
- Laboratory of Cell Biology and Biochemistry, Department of Biological Sciences, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Jun Shirai
- Laboratory of Cell Biology and Biochemistry, Department of Biological Sciences, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Miyo Matsuda
- Laboratory of Cell Biology and Biochemistry, Department of Biological Sciences, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Sae Nakanaga
- Laboratory of Cell Biology and Biochemistry, Department of Biological Sciences, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Shin Matsushita
- Laboratory of Cell Biology and Biochemistry, Department of Biological Sciences, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Kei Wakita
- Laboratory of Cell Biology and Biochemistry, Department of Biological Sciences, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Mizuki Hayashishita
- Laboratory of Cell Biology and Biochemistry, Department of Biological Sciences, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Rigel Suzuki
- Laboratory of Cell Biology and Biochemistry, Department of Biological Sciences, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Aya Noguchi
- Laboratory of Cell Biology and Biochemistry, Department of Biological Sciences, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Naoto Yokota
- Laboratory of Cell Biology and Biochemistry, Department of Biological Sciences, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Hiroyuki Kawahara
- Laboratory of Cell Biology and Biochemistry, Department of Biological Sciences, Tokyo Metropolitan University, Tokyo 192-0397, Japan
- Corresponding author
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6
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Miyauchi M, Matsumura R, Kawahara H. BAG6 supports stress fiber formation by preventing the ubiquitin-mediated degradation of RhoA. Mol Biol Cell 2023; 34:ar34. [PMID: 36884293 PMCID: PMC10092643 DOI: 10.1091/mbc.e22-08-0355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/09/2023] Open
Abstract
The Rho family of small GTPases is a key regulator of cytoskeletal actin polymerization. Although the ubiquitination of Rho proteins is reported to control their activity, the mechanisms by which the ubiquitination of Rho family proteins is controlled by ubiquitin ligases have yet to be elucidated. In this study, we identified BAG6 as the first factor needed to prevent the ubiquitination of RhoA, a critical Rho family protein in F-actin polymerization. We found that BAG6 is necessary for stress fiber formation by stabilizing endogenous RhoA. BAG6 deficiency enhanced the association between RhoA and Cullin-3-based ubiquitin ligases, thus promoting its polyubiquitination and subsequent degradation, leading to the abrogation of actin polymerization. In contrast, the restoration of RhoA expression through transient overexpression rescued the stress fiber formation defects induced by BAG6 depletion. BAG6 was also necessary for the appropriate assembly of focal adhesions as well as cell migration events. These findings reveal a novel role for BAG6 in maintaining the integrity of actin fiber polymerization and establish BAG6 as a RhoA-stabilizing holdase, which binds to and supports the function of RhoA.
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Affiliation(s)
- Maho Miyauchi
- Laboratory of Cell Biology and Biochemistry, Department of Biological Sciences, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Reina Matsumura
- Laboratory of Cell Biology and Biochemistry, Department of Biological Sciences, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Hiroyuki Kawahara
- Laboratory of Cell Biology and Biochemistry, Department of Biological Sciences, Tokyo Metropolitan University, Tokyo 192-0397, Japan
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7
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Tirincsi A, Sicking M, Hadzibeganovic D, Haßdenteufel S, Lang S. The Molecular Biodiversity of Protein Targeting and Protein Transport Related to the Endoplasmic Reticulum. Int J Mol Sci 2021; 23:143. [PMID: 35008565 PMCID: PMC8745461 DOI: 10.3390/ijms23010143] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Revised: 12/19/2021] [Accepted: 12/20/2021] [Indexed: 12/15/2022] Open
Abstract
Looking at the variety of the thousands of different polypeptides that have been focused on in the research on the endoplasmic reticulum from the last five decades taught us one humble lesson: no one size fits all. Cells use an impressive array of components to enable the safe transport of protein cargo from the cytosolic ribosomes to the endoplasmic reticulum. Safety during the transit is warranted by the interplay of cytosolic chaperones, membrane receptors, and protein translocases that together form functional networks and serve as protein targeting and translocation routes. While two targeting routes to the endoplasmic reticulum, SRP (signal recognition particle) and GET (guided entry of tail-anchored proteins), prefer targeting determinants at the N- and C-terminus of the cargo polypeptide, respectively, the recently discovered SND (SRP-independent) route seems to preferentially cater for cargos with non-generic targeting signals that are less hydrophobic or more distant from the termini. With an emphasis on targeting routes and protein translocases, we will discuss those functional networks that drive efficient protein topogenesis and shed light on their redundant and dynamic nature in health and disease.
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Affiliation(s)
- Andrea Tirincsi
- Department of Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany; (A.T.); (M.S.); (D.H.)
| | - Mark Sicking
- Department of Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany; (A.T.); (M.S.); (D.H.)
| | - Drazena Hadzibeganovic
- Department of Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany; (A.T.); (M.S.); (D.H.)
| | - Sarah Haßdenteufel
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Sven Lang
- Department of Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany; (A.T.); (M.S.); (D.H.)
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8
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Juillerat-Jeanneret L, Tafelmeyer P, Golshayan D. Regulation of Fibroblast Activation Protein-α Expression: Focus on Intracellular Protein Interactions. J Med Chem 2021; 64:14028-14045. [PMID: 34523930 DOI: 10.1021/acs.jmedchem.1c01010] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The prolyl-specific peptidase fibroblast activation protein-α (FAP-α) is expressed at very low or undetectable levels in nondiseased human tissues but is selectively induced in activated (myo)fibroblasts at sites of tissue remodeling in fibrogenic processes. In normal regenerative processes involving transient fibrosis FAP-α+(myo)fibroblasts disappear from injured tissues, replaced by cells with a normal FAP-α- phenotype. In chronic uncontrolled pathological fibrosis FAP-α+(myo)fibroblasts permanently replace normal tissues. The mechanisms of regulation and elimination of FAP-α expression in(myo)fibroblasts are unknown. According to a yeast two-hybrid screen and protein databanks search, we propose that the intracellular (co)-chaperone BAG6/BAT3 can interact with FAP-α, mediated by the BAG6/BAT3 Pro-rich domain, inducing proteosomal degradation of FAP-α protein under tissue homeostasis. In this Perspective, we discuss our findings in the context of current knowledge on the regulation of FAP-α expression and comment potential therapeutic strategies for uncontrolled fibrosis, including small molecule degraders (PROTACs)-modified FAP-α targeted inhibitors.
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Affiliation(s)
- Lucienne Juillerat-Jeanneret
- Transplantation Center and Transplantation Immunopathology Laboratory, Department of Medicine, Centre Hospitalier Universitaire Vaudois (CHUV) and University of Lausanne (UNIL), CH1011 Lausanne, Switzerland.,University Institute of Pathology, CHUV and UNIL, CH1011 Lausanne, Switzerland
| | - Petra Tafelmeyer
- Hybrigenics Services, Laboratories and Headquarters-Paris, 1 rue Pierre Fontaine, 91000 Evry, France.,Hybrigenics Corporation, Cambridge Innovation Center, 50 Milk Street, Cambridge, Massachusetts 02142, United States
| | - Dela Golshayan
- Transplantation Center and Transplantation Immunopathology Laboratory, Department of Medicine, Centre Hospitalier Universitaire Vaudois (CHUV) and University of Lausanne (UNIL), CH1011 Lausanne, Switzerland
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9
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Zhang R, Cui D, Xue T, Lang Y, Zhang Y, Li L, Sun H, Kuang Y, Li G, Tang J. HLA-B-associated transcript 3 (Bat3) stabilizes and activates p53 in a HAUSP-dependent manner. J Mol Cell Biol 2021; 12:99-112. [PMID: 31647545 PMCID: PMC7109604 DOI: 10.1093/jmcb/mjz102] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2019] [Revised: 07/12/2019] [Accepted: 08/26/2019] [Indexed: 01/06/2023] Open
Abstract
The p53 pathway is a highly complex signaling network including several key regulators. HAUSP is a critical component of the p53 pathway acting as a deubiquitinase for both p53 and its key repressor Mdm2. Here, we identified a novel HAUSP-interacting protein, HLA-B-associated transcript 3 (Bat3) and found it to be capable of inducing p53 stabilization and activation via a HAUSP-dependent mechanism, resulting in cell growth inhibition. Surprisingly, the deubiquitylating enzymatic activity of HAUSP was not required for this phenomenon. Co-immunoprecipitation showed that p53 coexisted in a complex with Bat3 and HAUSP in vivo, and HAUSP may serve as a binding mediator to enhance the interaction between p53 and Bat3. Further studies revealed that formation of this three-protein complex interfered with the binding of p53 to its proteasome receptor S5a and promoted the accumulation of p53 in nucleus. Notably, Mdm2 protein abundance is also regulated by Bat3 in the presence of HAUSP. Overexpression of Bat3 and HAUSP increases Mdm2 protein levels without influencing the p53–Mdm2 interaction and Mdm2-mediated p53 ubiquitination, indicating that Bat3–HAUSP-mediated protein stabilization is not specific to p53 and different mechanisms may be involved in Bat3-mediated regulation of p53–Mdm2 pathway. Together, our study unravels a novel mechanism by which p53 is stabilized and activated by HAUSP-mediated interaction with Bat3 and implies that Bat3 might function as a tumor suppressor through the stabilization of p53.
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Affiliation(s)
- Rui Zhang
- Department of Basic Veterinary, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China.,State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, China
| | - Di Cui
- Department of Basic Veterinary, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China.,State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, China.,Clinical Research Institute, Zhejiang Provincial People's Hospital, People's Hospital of Hangzhou Medical College, Hangzhou 310014, China
| | - Teng Xue
- Department of Basic Veterinary, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China.,State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, China
| | - Yue Lang
- Department of Basic Veterinary, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China.,State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, China
| | - Yunfan Zhang
- Department of Basic Veterinary, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China.,State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, China
| | - Lianjie Li
- Department of Basic Veterinary, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China.,State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, China
| | - Haili Sun
- Department of Basic Veterinary, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China.,State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, China
| | - Yu Kuang
- Department of Basic Veterinary, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China
| | - Gebin Li
- Department of Clinical Veterinary, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China
| | - Jun Tang
- Department of Basic Veterinary, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China.,State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, China
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10
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The Chaperone BAG6 Regulates Cellular Homeostasis between Autophagy and Apoptosis by Holding LC3B. iScience 2020; 23:101708. [PMID: 33241194 PMCID: PMC7674511 DOI: 10.1016/j.isci.2020.101708] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Revised: 07/27/2020] [Accepted: 10/16/2020] [Indexed: 12/15/2022] Open
Abstract
AMFR/gp78 and USP13 are a pair of ubiquitin ligase and deubiquitinase that ensure the accuracy of endoplasmic reticulum-associated degradation (ERAD). Depletion of USP13 leads to caspase activation and cleavage of the ERAD chaperone BAG6, which is reversed by knockdown of AMFR. However, the mechanism and physiological relevance of this regulation are still unclear. Here, by using the NEDDylator system, we screened out TXN as a substrate of AMFR and USP13 and showed its involvement in regulating CASP3 activation and BAG6 cleavage. Furthermore, we showed that the cleaved N-terminal BAG6 is located in the cytosol and interacts with both LC3B-I and unprocessed form of LC3B (Pro-LC3B) through the LIR1 motif to suppress autophagy. An NMR approach verified the direct interaction between BAG6 LIR1 and LC3B-I or Pro-LC3B. Collectively, our findings uncover a mechanism that converts BAG6 from an ERAD regulator to an autophagy tuner and apoptosis inducer during ER stress.
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11
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Abildgaard AB, Gersing SK, Larsen-Ledet S, Nielsen SV, Stein A, Lindorff-Larsen K, Hartmann-Petersen R. Co-Chaperones in Targeting and Delivery of Misfolded Proteins to the 26S Proteasome. Biomolecules 2020; 10:E1141. [PMID: 32759676 PMCID: PMC7463752 DOI: 10.3390/biom10081141] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 07/31/2020] [Accepted: 08/02/2020] [Indexed: 12/11/2022] Open
Abstract
Protein homeostasis (proteostasis) is essential for the cell and is maintained by a highly conserved protein quality control (PQC) system, which triages newly synthesized, mislocalized and misfolded proteins. The ubiquitin-proteasome system (UPS), molecular chaperones, and co-chaperones are vital PQC elements that work together to facilitate degradation of misfolded and toxic protein species through the 26S proteasome. However, the underlying mechanisms are complex and remain partly unclear. Here, we provide an overview of the current knowledge on the co-chaperones that directly take part in targeting and delivery of PQC substrates for degradation. While J-domain proteins (JDPs) target substrates for the heat shock protein 70 (HSP70) chaperones, nucleotide-exchange factors (NEFs) deliver HSP70-bound substrates to the proteasome. So far, three NEFs have been established in proteasomal delivery: HSP110 and the ubiquitin-like (UBL) domain proteins BAG-1 and BAG-6, the latter acting as a chaperone itself and carrying its substrates directly to the proteasome. A better understanding of the individual delivery pathways will improve our ability to regulate the triage, and thus regulate the fate of aberrant proteins involved in cell stress and disease, examples of which are given throughout the review.
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Affiliation(s)
- Amanda B. Abildgaard
- Department of Biology, The Linderstrøm-Lang Centre for Protein Science, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 Copenhagen, Denmark; (A.B.A.); (S.K.G.); (S.L.-L.); (K.L.-L.)
| | - Sarah K. Gersing
- Department of Biology, The Linderstrøm-Lang Centre for Protein Science, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 Copenhagen, Denmark; (A.B.A.); (S.K.G.); (S.L.-L.); (K.L.-L.)
| | - Sven Larsen-Ledet
- Department of Biology, The Linderstrøm-Lang Centre for Protein Science, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 Copenhagen, Denmark; (A.B.A.); (S.K.G.); (S.L.-L.); (K.L.-L.)
| | - Sofie V. Nielsen
- Department of Biology, Section for Computational and RNA Biology, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 Copenhagen, Denmark; (S.V.N.); (A.S.)
| | - Amelie Stein
- Department of Biology, Section for Computational and RNA Biology, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 Copenhagen, Denmark; (S.V.N.); (A.S.)
| | - Kresten Lindorff-Larsen
- Department of Biology, The Linderstrøm-Lang Centre for Protein Science, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 Copenhagen, Denmark; (A.B.A.); (S.K.G.); (S.L.-L.); (K.L.-L.)
| | - Rasmus Hartmann-Petersen
- Department of Biology, The Linderstrøm-Lang Centre for Protein Science, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 Copenhagen, Denmark; (A.B.A.); (S.K.G.); (S.L.-L.); (K.L.-L.)
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12
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PAQR9 Modulates BAG6-mediated protein quality control of mislocalized membrane proteins. Biochem J 2020; 477:477-489. [PMID: 31904842 DOI: 10.1042/bcj20190620] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Revised: 12/24/2019] [Accepted: 01/06/2020] [Indexed: 11/17/2022]
Abstract
Protein quality control is crucial for maintaining cellular homeostasis and its dysfunction is closely linked to human diseases. The post-translational protein quality control machinery mainly composed of BCL-2-associated athanogene 6 (BAG6) is responsible for triage of mislocalized membrane proteins (MLPs). However, it is unknown how the BAG6-mediated degradation of MLPs is regulated. We report here that PAQR9, a member of the Progesterone and AdipoQ receptor (PAQR) family, is able to modulate BAG6-mediated triage of MLPs. Analysis with mass spectrometry identified that BAG6 is one of the major proteins interacting with PAQR9 and such interaction is confirmed by co-immunoprecipitation and co-localization assays. The protein degradation rate of representative MLPs is accelerated by PAQR9 knockdown. Consistently, the polyubiquitination of MLPs is enhanced by PAQR9 knockdown. PAQR9 binds to the DUF3538 domain within the proline-rich stretch of BAG6. PAQR9 reduces the binding of MLPs to BAG6 in a DUF3538 domain-dependent manner. Taken together, our results indicate that PAQR9 plays a role in the regulation of protein quality control of MLPs via affecting the interaction of BAG6 with membrane proteins.
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13
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Abstract
Due to their topology tail-anchored (TA) proteins must target to the membrane independently of the co-translational route defined by the signal sequence recognition particle (SRP), its receptor and the translocon Sec61. More than a decade of work has extensively characterized a highly conserved pathway, the yeast GET or mammalian TRC40 pathway, which is capable of countering the biogenetic challenge posed by the C-terminal TA anchor. In this review we briefly summarize current models of this targeting route and focus on emerging aspects such as the intricate interplay with the proteostatic network of cells and with other targeting pathways. Importantly, we consider the lessons provided by the in vivo analysis of the pathway in different model organisms and by the consideration of its full client spectrum in more recent studies. This analysis of the state of the field highlights directions in which the current models may be experimentally probed and conceptually extended.
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Affiliation(s)
- Nica Borgese
- Institute of Neuroscience and BIOMETRA Department, Consiglio Nazionale delle Ricerche and Università degli Studi di Milano, via Vanvitelli 32, 20129, Milan, Italy.
| | - Javier Coy-Vergara
- Department of Molecular Biology, University of Göttingen Medical Centre, Humboldtallee 23, 37073, Göttingen, Germany
| | - Sara Francesca Colombo
- Institute of Neuroscience and BIOMETRA Department, Consiglio Nazionale delle Ricerche and Università degli Studi di Milano, via Vanvitelli 32, 20129, Milan, Italy
| | - Blanche Schwappach
- Department of Molecular Biology, University of Göttingen Medical Centre, Humboldtallee 23, 37073, Göttingen, Germany.
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14
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Mariotto E, Viola G, Zanon C, Aveic S. A BAG's life: Every connection matters in cancer. Pharmacol Ther 2020; 209:107498. [PMID: 32001313 DOI: 10.1016/j.pharmthera.2020.107498] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Accepted: 01/17/2020] [Indexed: 12/30/2022]
Abstract
The members of the BCL-2 associated athanogene (BAG) family participate in the regulation of a variety of interrelated physiological processes, such as autophagy, apoptosis, and protein homeostasis. Under normal circumstances, the six BAG members described in mammals (BAG1-6) principally assist the 70 kDa heat-shock protein (HSP70) in protein folding; however, their role as oncogenes is becoming increasingly evident. Deregulation of the BAG multigene family has been associated with cell transformation, tumor recurrence, and drug resistance. In addition to BAG overexpression, BAG members are also involved in many oncogenic protein-protein interactions (PPIs). As such, either the inhibition of overloading BAGs or of specific BAG-client protein interactions could have paramount therapeutic value. In this review, we will examine the role of each BAG family member in different malignancies, focusing on their modular structure, which enables interaction with a variety of proteins to exert their pro-tumorigenic role. Lastly, critical remarks on the unmet needs for proposing effective BAG inhibitors will be pointed out.
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Affiliation(s)
- Elena Mariotto
- Department of Woman's and Child's Health, University of Padova, Via Giustiniani 2, 35127 Padova, Italy; Fondazione Istituto di Ricerca Pediatrica Città della Speranza, Corso Stati Uniti 4, 35128 Padova, Italy.
| | - Giampietro Viola
- Department of Woman's and Child's Health, University of Padova, Via Giustiniani 2, 35127 Padova, Italy; Fondazione Istituto di Ricerca Pediatrica Città della Speranza, Corso Stati Uniti 4, 35128 Padova, Italy
| | - Carlo Zanon
- Fondazione Istituto di Ricerca Pediatrica Città della Speranza, Corso Stati Uniti 4, 35128 Padova, Italy
| | - Sanja Aveic
- Neuroblastoma Laboratory, Fondazione Istituto di Ricerca Pediatrica Città della Speranza, Corso Stati Uniti 4, 35128 Padova, Italy
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15
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Minami S, Yokota N, Kawahara H. BAG6 contributes to glucose uptake by supporting the cell surface translocation of the glucose transporter GLUT4. Biol Open 2020; 9:bio.047324. [PMID: 31911483 PMCID: PMC6994957 DOI: 10.1242/bio.047324] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Defective translocation of glucose transporter 4 (GLUT4) to the cell surface is a key feature of insulin resistance in type 2 diabetes. Therefore, elucidating the mechanism of GLUT4 translocation is of primary importance. The mammalian Bag6/Bat3 gene has been suggested to be linked with potential obesity- and diabetes-associated loci, while its function in the control of glucose incorporation into the cytoplasm has not been investigated. In this study, we established a series of cell lines that stably expressed GLUT4 with three tandem repeats of the antigenic peptide inserted into its 1st extracellular loop. With these cell lines, we found that the depletion of endogenous BAG6 downregulated the cell surface expression of GLUT4, concomitant with the reduced incorporation of a glucose analog into the cells. Defective intracellular translocation of GLUT4 in BAG6-depleted cells is similar to the case observed for the depletion of Rab8a, an essential regulator of insulin-stimulated GLUT4 translocation. In addition, we observed that the assembly of syntaxin 6 into the endoplasmic reticulum membrane was slightly disturbed under BAG6 depletion. Given that Rab8a and syntaxin 6 are critical for GLUT4 translocation, we suggest that BAG6 may play multiple roles in the trafficking of glucose transporters to the cell surface. This article has an associated First Person interview with the first author of the paper. Summary: BAG6 is critical for the insulin-stimulated translocation of GLUT4 from its peri-nuclear storage compartments to the cell surface.
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Affiliation(s)
- Setsuya Minami
- Laboratory of Cell Biology and Biochemistry, Department of Biological Sciences, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Naoto Yokota
- Laboratory of Cell Biology and Biochemistry, Department of Biological Sciences, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Hiroyuki Kawahara
- Laboratory of Cell Biology and Biochemistry, Department of Biological Sciences, Tokyo Metropolitan University, Tokyo 192-0397, Japan
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16
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Abstract
One-fourth of eukaryotic genes code for integral membrane proteins, nearly all of which are inserted and assembled at the endoplasmic reticulum (ER). The defining feature of membrane proteins is one or more transmembrane domains (TMDs). During membrane protein biogenesis, TMDs are selectively recognized, shielded, and chaperoned into the lipid bilayer, where they often assemble with other TMDs. If maturation fails, exposed TMDs serve as a cue for engagement of degradation pathways. Thus, TMD-recognition factors in the cytosol and ER are essential for membrane protein biogenesis and quality control. Here, we discuss the growing assortment of cytosolic and membrane-embedded TMD-recognition factors, the pathways within which they operate, and mechanistic principles of recognition.
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17
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Hayashishita M, Kawahara H, Yokota N. BAG6 deficiency induces mis-distribution of mitochondrial clusters under depolarization. FEBS Open Bio 2019; 9:1281-1291. [PMID: 31125507 PMCID: PMC6609563 DOI: 10.1002/2211-5463.12677] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Revised: 04/16/2019] [Accepted: 05/22/2019] [Indexed: 01/09/2023] Open
Abstract
Accumulation of damaged mitochondria is implicated in a number of neurodegenerative disorders, including Parkinson's disease. Therefore, the machinery for mitochondrial quality control is important for the prevention of such diseases. It has been reported that Parkin‐ and p62/sequestosome 1 (SQSTM1)‐mediated clustering and subsequent elimination of damaged mitochondria (termed mitophagy) are critical for maintaining the quality of mitochondria under stress induced by uncoupling agents such as carbonyl cyanide m‐chlorophenyl hydrazone. However, the molecular mechanisms underlying mitochondrial translocation to the perinuclear region during mitophagy have not been adequately addressed to date. In this study, we found that BCL2‐associated athanogene 6 (BAG6; also known as BAT3 or Scythe) is required for this process. Indeed, RNA interference‐mediated depletion of endogenous BAG6 prevented Parkin‐dependent relocalization of mitochondrial clusters to the perinuclear cytoplasmic region, whereas BAG6 knockdown did not affect the translocation of Parkin and p62/SQSTM1 to the depolarized mitochondria and subsequent aggregation. These results suggest that BAG6 is essential for cytoplasmic redistribution, but not for clustering, of damaged mitochondria.
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Affiliation(s)
- Mizuki Hayashishita
- Laboratory of Cell Biology and Biochemistry, Department of Biological Sciences, Tokyo Metropolitan University, Japan
| | - Hiroyuki Kawahara
- Laboratory of Cell Biology and Biochemistry, Department of Biological Sciences, Tokyo Metropolitan University, Japan
| | - Naoto Yokota
- Laboratory of Cell Biology and Biochemistry, Department of Biological Sciences, Tokyo Metropolitan University, Japan
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18
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Takahashi T, Minami S, Tsuchiya Y, Tajima K, Sakai N, Suga K, Hisanaga SI, Ohbayashi N, Fukuda M, Kawahara H. Cytoplasmic control of Rab family small GTPases through BAG6. EMBO Rep 2019; 20:embr.201846794. [PMID: 30804014 PMCID: PMC6446207 DOI: 10.15252/embr.201846794] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2018] [Revised: 01/25/2019] [Accepted: 01/29/2019] [Indexed: 11/18/2022] Open
Abstract
Rab family small GTPases are master regulators of distinct steps of intracellular vesicle trafficking in eukaryotic cells. GDP‐bound cytoplasmic forms of Rab proteins are prone to aggregation due to the exposure of hydrophobic groups but the machinery that determines the fate of Rab species in the cytosol has not been elucidated in detail. In this study, we find that BAG6 (BAT3/Scythe) predominantly recognizes a cryptic portion of GDP‐associated Rab8a, while its major GTP‐bound active form is not recognized. The hydrophobic residues of the Switch I region of Rab8a are essential for its interaction with BAG6 and the degradation of GDP‐Rab8a via the ubiquitin‐proteasome system. BAG6 prevents the excess accumulation of inactive Rab8a, whose accumulation impairs intracellular membrane trafficking. BAG6 binds not only Rab8a but also a functionally distinct set of Rab family proteins, and is also required for the correct distribution of Golgi and endosomal markers. From these observations, we suggest that Rab proteins represent a novel set of substrates for BAG6, and the BAG6‐mediated pathway is associated with the regulation of membrane vesicle trafficking events in mammalian cells.
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Affiliation(s)
- Toshiki Takahashi
- Laboratory of Cell Biology and Biochemistry, Department of Biological Sciences, Tokyo Metropolitan University, Tokyo, Japan
| | - Setsuya Minami
- Laboratory of Cell Biology and Biochemistry, Department of Biological Sciences, Tokyo Metropolitan University, Tokyo, Japan
| | - Yugo Tsuchiya
- Laboratory of Cell Biology and Biochemistry, Department of Biological Sciences, Tokyo Metropolitan University, Tokyo, Japan
| | - Kazu Tajima
- Laboratory of Cell Biology and Biochemistry, Department of Biological Sciences, Tokyo Metropolitan University, Tokyo, Japan
| | - Natsumi Sakai
- Laboratory of Cell Biology and Biochemistry, Department of Biological Sciences, Tokyo Metropolitan University, Tokyo, Japan
| | - Kei Suga
- Department of Cell Physiology, Kyorin University School of Medicine, Mitaka, Japan.,Department of Chemistry, Kyorin University School of Medicine, Mitaka, Japan
| | - Shin-Ichi Hisanaga
- Laboratory of Molecular Neuroscience, Department of Biological Sciences, Tokyo Metropolitan University, Tokyo, Japan
| | - Norihiko Ohbayashi
- Department of Physiological Chemistry, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Mitsunori Fukuda
- Department of Integrative Life Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
| | - Hiroyuki Kawahara
- Laboratory of Cell Biology and Biochemistry, Department of Biological Sciences, Tokyo Metropolitan University, Tokyo, Japan
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19
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Benarroch R, Austin JM, Ahmed F, Isaacson RL. The roles of cytosolic quality control proteins, SGTA and the BAG6 complex, in disease. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2019; 114:265-313. [PMID: 30635083 PMCID: PMC7102839 DOI: 10.1016/bs.apcsb.2018.11.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
SGTA is a co-chaperone that, in collaboration with the complex of BAG6/UBL4A/TRC35, facilitates the biogenesis and quality control of hydrophobic proteins, protecting them from the aqueous cytosolic environment. This work includes targeting tail-anchored proteins to their resident membranes, sorting of membrane and secretory proteins that mislocalize to the cytoplasm and endoplasmic reticulum-associated degradation of misfolded proteins. Since these functions are all vital for the cell's continued proteostasis, their disruption poses a threat to the cell, with a particular risk of protein aggregation, a phenomenon that underpins many diseases. Although the specific disease implications of machinery involved in quality control of hydrophobic substrates are poorly understood, here we summarize much of the available information on this topic.
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Affiliation(s)
- Rashi Benarroch
- Department of Chemistry, King's College London, London, United Kingdom
| | - Jennifer M Austin
- Department of Chemistry, King's College London, London, United Kingdom
| | - Fahmeda Ahmed
- Department of Chemistry, King's College London, London, United Kingdom
| | - Rivka L Isaacson
- Department of Chemistry, King's College London, London, United Kingdom.
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20
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Elimination of a signal sequence-uncleaved form of defective HLA protein through BAG6. Sci Rep 2017; 7:14545. [PMID: 29109525 PMCID: PMC5674028 DOI: 10.1038/s41598-017-14975-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Accepted: 10/16/2017] [Indexed: 12/15/2022] Open
Abstract
A portion of newly synthesized transmembrane domain proteins tend to fail to assemble correctly in the lumen of the endoplasmic reticulum, thus resulting in the production of a signal sequence-uncleaved form of the defective species. Although the efficient degradation of these mistargeted polypeptides is crucial, the molecular mechanism of their elimination pathway has not been adequately characterized. In this study, we focused on one such cryptic portion of a defective transmembrane domain protein, HLA-A, and show that a part of HLA-A is produced as a signal sequence-uncleaved labile species that is immediately targeted to the degradation pathway. We found that both BAG6 and proteasomes are indispensable for elimination of mislocalized HLA-A species. Furthermore, defective HLA-A is subjected to BAG6-dependent solubilization in the cytoplasm. These observations suggest that BAG6 acts as a critical factor for proteasome-mediated degradation of mislocalized HLA-A with a non-cleaved signal sequence at its N-terminus.
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21
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Chua NK, Howe V, Jatana N, Thukral L, Brown AJ. A conserved degron containing an amphipathic helix regulates the cholesterol-mediated turnover of human squalene monooxygenase, a rate-limiting enzyme in cholesterol synthesis. J Biol Chem 2017; 292:19959-19973. [PMID: 28972164 DOI: 10.1074/jbc.m117.794230] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2017] [Revised: 09/13/2017] [Indexed: 12/22/2022] Open
Abstract
Cholesterol biosynthesis in the endoplasmic reticulum (ER) is tightly controlled by multiple mechanisms to regulate cellular cholesterol levels. Squalene monooxygenase (SM) is the second rate-limiting enzyme in cholesterol biosynthesis and is regulated both transcriptionally and post-translationally. SM undergoes cholesterol-dependent proteasomal degradation when cholesterol is in excess. The first 100 amino acids of SM (designated SM N100) are necessary for this degradative process and represent the shortest cholesterol-regulated degron identified to date. However, the fundamental intrinsic characteristics of this degron remain unknown. In this study, we performed a series of deletions, point mutations, and domain swaps to identify a 12-residue region (residues Gln-62-Leu-73), required for SM cholesterol-mediated turnover. Molecular dynamics and circular dichroism revealed an amphipathic helix within this 12-residue region. Moreover, 70% of the variation in cholesterol regulation was dependent on the hydrophobicity of this region. Of note, the earliest known Doa10 yeast degron, Deg1, also contains an amphipathic helix and exhibits 42% amino acid similarity with SM N100. Mutating SM residues Phe-35/Ser-37/Leu-65/Ile-69 into alanine, based on the key residues in Deg1, blunted SM cholesterol-mediated turnover. Taken together, our results support a model whereby the amphipathic helix in SM N100 attaches reversibly to the ER membrane depending on cholesterol levels; with excess, the helix is ejected and unravels, exposing a hydrophobic patch, which then serves as a degradation signal. Our findings shed new light on the regulation of a key cholesterol synthesis enzyme, highlighting the conservation of critical degron features from yeast to humans.
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Affiliation(s)
- Ngee Kiat Chua
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Vicky Howe
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Nidhi Jatana
- Council of Scientific and Industrial Research-Institute of Genomics and Integrative Biology, Mathura Road, Sukhdev Vihar, New Delhi 110 020, India
| | - Lipi Thukral
- Council of Scientific and Industrial Research-Institute of Genomics and Integrative Biology, Mathura Road, Sukhdev Vihar, New Delhi 110 020, India
| | - Andrew J Brown
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia.
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22
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On the road to nowhere: cross-talk between post-translational protein targeting and cytosolic quality control. Biochem Soc Trans 2016; 44:796-801. [DOI: 10.1042/bst20160045] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Indexed: 02/06/2023]
Abstract
A well-defined co-translational pathway couples the synthesis and translocation of nascent polypeptides into and across the membrane of the endoplasmic reticulum (ER), thereby minimizing the possibility of the hydrophobic signals and transmembrane domains that such proteins contain from being exposed to the cytosol. Nevertheless, a proportion of these co-translational substrates may fail to reach the ER, and therefore mislocalize to the cytosol where their intrinsic hydrophobicity makes them aggregation-prone. A range of hydrophobic precursor proteins that employ alternative, post-translational, routes for ER translocation also contribute to the cytosolic pool of mislocalized proteins (MLPs). In this review, we detail how mammalian cells can efficiently deal with these MLPs by selectively targeting them for proteasomal degradation. Strikingly, this pathway for MLP degradation is regulated by cytosolic components that also facilitate the TRC40-dependent, post-translational, delivery of tail-anchored membrane proteins (TA proteins) to the ER. Among these components are small glutamine-rich tetratricopeptide repeat-containing protein α (SGTA) and Bcl-2-associated athanogene 6 (BAG6), which appear to play a decisive role in enforcing quality control over hydrophobic precursor proteins that have mislocalized to the cytosol, directing them to either productive membrane insertion or selective ubiquitination and proteasomal degradation.
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23
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Krysztofinska EM, Martínez-Lumbreras S, Thapaliya A, Evans NJ, High S, Isaacson RL. Structural and functional insights into the E3 ligase, RNF126. Sci Rep 2016; 6:26433. [PMID: 27193484 PMCID: PMC4872217 DOI: 10.1038/srep26433] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Accepted: 05/03/2016] [Indexed: 12/14/2022] Open
Abstract
RNF126 is an E3 ubiquitin ligase that collaborates with the BAG6 sortase complex to ubiquitinate hydrophobic substrates in the cytoplasm that are destined for proteasomal recycling. Composed of a trimeric complex of BAG6, TRC35 and UBL4A the BAG6 sortase is also associated with SGTA, a co-chaperone from which it can obtain hydrophobic substrates. Here we solve the solution structure of the RNF126 zinc finger domain in complex with the BAG6 UBL domain. We also characterise an interaction between RNF126 and UBL4A and analyse the competition between SGTA and RNF126 for the N-terminal BAG6 binding site. This work sheds light on the sorting mechanism of the BAG6 complex and its accessory proteins which, together, decide the fate of stray hydrophobic proteins in the aqueous cytoplasm.
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Affiliation(s)
- Ewelina M. Krysztofinska
- Department of Chemistry, King’s College London, Britannia House, Trinity Street, London, SE1 1DB, UK
| | | | - Arjun Thapaliya
- Department of Chemistry, King’s College London, Britannia House, Trinity Street, London, SE1 1DB, UK
| | - Nicola J. Evans
- Department of Chemistry, King’s College London, Britannia House, Trinity Street, London, SE1 1DB, UK
| | - Stephen High
- Faculty of Life Sciences, University of Manchester, The Michael Smith Building, Oxford Road, Manchester, M13 9PT, UK
| | - Rivka L. Isaacson
- Department of Chemistry, King’s College London, Britannia House, Trinity Street, London, SE1 1DB, UK
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24
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Behl C. Breaking BAG: The Co-Chaperone BAG3 in Health and Disease. Trends Pharmacol Sci 2016; 37:672-688. [PMID: 27162137 DOI: 10.1016/j.tips.2016.04.007] [Citation(s) in RCA: 183] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Revised: 04/11/2016] [Accepted: 04/12/2016] [Indexed: 01/01/2023]
Abstract
Human BAG (Bcl-2-associated athanogene) proteins form a family of antiapoptotic proteins that currently consists of six members (BAG1-6) all sharing the BAG protein domain from which the name arises. Via this domain, BAG proteins bind to the heat shock protein 70 (Hsp70), thereby acting as a co-chaperone regulating the activity of Hsp70. In addition to their antiapoptotic activity, all human BAG proteins have distinct functions in health and disease, and BAG3 in particular is the focus of many investigations. BAG3 has a modular protein domain composition offering the possibility for manifold interactions with other proteins. Various BAG3 functions are implicated in disorders including cancer, myopathies, and neurodegeneration. The discovery of its role in selective autophagy and the description of BAG3-mediated selective macroautophagy as an adaptive mechanism to maintain cellular homeostasis, under stress as well as during aging, make BAG3 a highly interesting target for future pharmacological interventions.
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Affiliation(s)
- Christian Behl
- Institute of Pathobiochemistry, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany.
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Boomsma W, Nielsen SV, Lindorff-Larsen K, Hartmann-Petersen R, Ellgaard L. Bioinformatics analysis identifies several intrinsically disordered human E3 ubiquitin-protein ligases. PeerJ 2016; 4:e1725. [PMID: 26966660 PMCID: PMC4782732 DOI: 10.7717/peerj.1725] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Accepted: 02/02/2016] [Indexed: 12/28/2022] Open
Abstract
The ubiquitin-proteasome system targets misfolded proteins for degradation. Since the accumulation of such proteins is potentially harmful for the cell, their prompt removal is important. E3 ubiquitin-protein ligases mediate substrate ubiquitination by bringing together the substrate with an E2 ubiquitin-conjugating enzyme, which transfers ubiquitin to the substrate. For misfolded proteins, substrate recognition is generally delegated to molecular chaperones that subsequently interact with specific E3 ligases. An important exception is San1, a yeast E3 ligase. San1 harbors extensive regions of intrinsic disorder, which provide both conformational flexibility and sites for direct recognition of misfolded targets of vastly different conformations. So far, no mammalian ortholog of San1 is known, nor is it clear whether other E3 ligases utilize disordered regions for substrate recognition. Here, we conduct a bioinformatics analysis to examine >600 human and S. cerevisiae E3 ligases to identify enzymes that are similar to San1 in terms of function and/or mechanism of substrate recognition. An initial sequence-based database search was found to detect candidates primarily based on the homology of their ordered regions, and did not capture the unique disorder patterns that encode the functional mechanism of San1. However, by searching specifically for key features of the San1 sequence, such as long regions of intrinsic disorder embedded with short stretches predicted to be suitable for substrate interaction, we identified several E3 ligases with these characteristics. Our initial analysis revealed that another remarkable trait of San1 is shared with several candidate E3 ligases: long stretches of complete lysine suppression, which in San1 limits auto-ubiquitination. We encode these characteristic features into a San1 similarity-score, and present a set of proteins that are plausible candidates as San1 counterparts in humans. In conclusion, our work indicates that San1 is not a unique case, and that several other yeast and human E3 ligases have sequence properties that may allow them to recognize substrates by a similar mechanism as San1.
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Affiliation(s)
- Wouter Boomsma
- Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen , Copenhagen , Denmark
| | - Sofie V Nielsen
- Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen , Copenhagen , Denmark
| | - Kresten Lindorff-Larsen
- Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen , Copenhagen , Denmark
| | - Rasmus Hartmann-Petersen
- Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen , Copenhagen , Denmark
| | - Lars Ellgaard
- Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen , Copenhagen , Denmark
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