1
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Dao TP, Rajendran A, Galagedera SKK, Haws W, Castañeda CA. Short disordered termini and proline-rich domain are major regulators of UBQLN1/2/4 phase separation. Biophys J 2024; 123:1449-1457. [PMID: 38041404 PMCID: PMC11163289 DOI: 10.1016/j.bpj.2023.11.3401] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2023] [Revised: 11/28/2023] [Accepted: 11/29/2023] [Indexed: 12/03/2023] Open
Abstract
Highly homologous ubiquitin-binding shuttle proteins UBQLN1, UBQLN2, and UBQLN4 differ in both their specific protein quality control functions and their propensities to localize to stress-induced condensates, cellular aggregates, and aggresomes. We previously showed that UBQLN2 phase separates in vitro, and that the phase separation propensities of UBQLN2 deletion constructs correlate with their ability to form condensates in cells. Here, we demonstrated that full-length UBQLN1, UBQLN2, and UBQLN4 exhibit distinct phase behaviors in vitro. Strikingly, UBQLN4 phase separates at a much lower saturation concentration than UBQLN1. However, neither UBQLN1 nor UBQLN4 phase separates with a strong temperature dependence, unlike UBQLN2. We determined that the temperature-dependent phase behavior of UBQLN2 stems from its unique proline-rich region, which is absent in the other UBQLNs. We found that the short N-terminal disordered regions of UBQLN1, UBQLN2, and UBQLN4 inhibit UBQLN phase separation via electrostatics interactions. Charge variants of the N-terminal regions exhibit altered phase behaviors. Consistent with the sensitivity of UBQLN phase separation to the composition of the N-terminal regions, epitope tags placed on the N-termini of the UBQLNs tune phase separation. Overall, our in vitro results have important implications for studies of UBQLNs in cells, including the identification of phase separation as a potential mechanism to distinguish the cellular roles of UBQLNs and the need to apply caution when using epitope tags to prevent experimental artifacts.
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Affiliation(s)
- Thuy P Dao
- Departments of Biology and Chemistry, Syracuse University, Syracuse, New York
| | - Anitha Rajendran
- Departments of Biology and Chemistry, Syracuse University, Syracuse, New York
| | | | - William Haws
- Departments of Biology and Chemistry, Syracuse University, Syracuse, New York
| | - Carlos A Castañeda
- Departments of Biology and Chemistry, Syracuse University, Syracuse, New York; Interdisciplinary Neuroscience Program, Syracuse University, Syracuse, New York; BioInspired Institute, Syracuse University, Syracuse, New York.
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2
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Dao TP, Rajendran A, Galagedera SKK, Haws W, Castañeda CA. Short N-terminal disordered regions and the proline-rich domain are major regulators of phase transitions for full-length UBQLN1, UBQLN2 and UBQLN4. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.27.559790. [PMID: 37808720 PMCID: PMC10557701 DOI: 10.1101/2023.09.27.559790] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/10/2023]
Abstract
Highly homologous ubiquitin-binding shuttle proteins UBQLN1, UBQLN2 and UBQLN4 differ in both their specific protein quality control functions and their propensities to localize to stress-induced condensates, cellular aggregates and aggresomes. We previously showed that UBQLN2 phase separates in vitro, and that the phase separation propensities of UBQLN2 deletion constructs correlate with their ability to form condensates in cells. Here, we demonstrated that full-length UBQLN1, UBQLN2 and UBQLN4 exhibit distinct phase behaviors in vitro. Strikingly, UBQLN4 phase separates at a much lower saturation concentration than UBQLN1. However, neither UBQLN1 nor UBQLN4 phase separates with a strong temperature dependence, unlike UBQLN2. We determined that the temperature-dependent phase behavior of UBQLN2 stems from its unique proline-rich (Pxx) region, which is absent in the other UBQLNs. We found that the short N-terminal disordered regions of UBQLN1, UBQLN2 and UBQLN4 inhibit UBQLN phase separation via electrostatics interactions. Charge variants of the N-terminal regions exhibit altered phase behaviors. Consistent with the sensitivity of UBQLN phase separation to the composition of the N-terminal regions, epitope tags placed on the N-termini of the UBQLNs tune phase separation. Overall, our in vitro results have important implications for studies of UBQLNs in cells, including the identification of phase separation as a potential mechanism to distinguish the cellular roles of UBQLNs, and the need to apply caution when using epitope tags to prevent experimental artifacts.
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Affiliation(s)
- Thuy P. Dao
- Departments of Biology and Chemistry, Syracuse University, Syracuse, NY 13244, USA
| | - Anitha Rajendran
- Departments of Biology and Chemistry, Syracuse University, Syracuse, NY 13244, USA
| | | | - William Haws
- Departments of Biology and Chemistry, Syracuse University, Syracuse, NY 13244, USA
| | - Carlos A. Castañeda
- Departments of Biology and Chemistry, Syracuse University, Syracuse, NY 13244, USA
- Interdisciplinary Neuroscience Program, Syracuse University, Syracuse, NY 13244, USA
- BioInspired Institute, Syracuse University, Syracuse, NY 13244, USA
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3
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Farag M, Borcherds WM, Bremer A, Mittag T, Pappu RV. Phase separation of protein mixtures is driven by the interplay of homotypic and heterotypic interactions. Nat Commun 2023; 14:5527. [PMID: 37684240 PMCID: PMC10491635 DOI: 10.1038/s41467-023-41274-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Accepted: 08/29/2023] [Indexed: 09/10/2023] Open
Abstract
Prion-like low-complexity domains (PLCDs) are involved in the formation and regulation of distinct biomolecular condensates that form via phase separation coupled to percolation. Intracellular condensates often encompass numerous distinct proteins with PLCDs. Here, we combine simulations and experiments to study mixtures of PLCDs from two RNA-binding proteins, hnRNPA1 and FUS. Using simulations and experiments, we find that 1:1 mixtures of A1-LCD and FUS-LCD undergo phase separation more readily than either of the PLCDs on their own due to complementary electrostatic interactions. Tie line analysis reveals that stoichiometric ratios of different components and their sequence-encoded interactions contribute jointly to the driving forces for condensate formation. Simulations also show that the spatial organization of PLCDs within condensates is governed by relative strengths of homotypic versus heterotypic interactions. We uncover rules for how interaction strengths and sequence lengths modulate conformational preferences of molecules at interfaces of condensates formed by mixtures of proteins.
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Affiliation(s)
- Mina Farag
- Department of Biomedical Engineering and Center for Biomolecular Condensates, Washington University in St. Louis, St. Louis, MO, 63130, USA
| | - Wade M Borcherds
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, 38105, USA
| | - Anne Bremer
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, 38105, USA
| | - Tanja Mittag
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, 38105, USA.
| | - Rohit V Pappu
- Department of Biomedical Engineering and Center for Biomolecular Condensates, Washington University in St. Louis, St. Louis, MO, 63130, USA.
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4
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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: 0] [Impact Index Per Article: 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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5
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Pappu R, Farag M, Borcherds W, Bremer A, Mittag T. Phase Separation in Mixtures of Prion-Like Low Complexity Domains is Driven by the Interplay of Homotypic and Heterotypic Interactions. RESEARCH SQUARE 2023:rs.3.rs-2870258. [PMID: 37205474 PMCID: PMC10187436 DOI: 10.21203/rs.3.rs-2870258/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Prion-like low-complexity domains (PLCDs) are involved in the formation and regulation of distinct biomolecular condensates that form via coupled associative and segregative phase transitions. We previously deciphered how evolutionarily conserved sequence features drive phase separation of PLCDs through homotypic interactions. However, condensates typically encompass a diverse mixture of proteins with PLCDs. Here, we combine simulations and experiments to study mixtures of PLCDs from two RNA binding proteins namely, hnRNPA1 and FUS. We find that 1:1 mixtures of the A1-LCD and FUS-LCD undergo phase separation more readily than either of the PLCDs on their own. The enhanced driving forces for phase separation of mixtures of A1-LCD and FUS-LCD arise partly from complementary electrostatic interactions between the two proteins. This complex coacervation-like mechanism adds to complementary interactions among aromatic residues. Further, tie line analysis shows that stoichiometric ratios of different components and their sequence-encoded interactions jointly contribute to the driving forces for condensate formation. These results highlight how expression levels might be tuned to regulate the driving forces for condensate formation in vivo . Simulations also show that the organization of PLCDs within condensates deviates from expectations based on random mixture models. Instead, spatial organization within condensates will reflect the relative strengths of homotypic versus heterotypic interactions. We also uncover rules for how interaction strengths and sequence lengths modulate conformational preferences of molecules at interfaces of condensates formed by mixtures of proteins. Overall, our findings emphasize the network-like organization of molecules within multicomponent condensates, and the distinctive, composition-specific conformational features of condensate interfaces.
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6
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Kim SH, Nichols KD, Anderson EN, Liu Y, Ramesh N, Jia W, Kuerbis CJ, Scalf M, Smith LM, Pandey UB, Tibbetts RS. Axon guidance genes modulate neurotoxicity of ALS-associated UBQLN2. eLife 2023; 12:e84382. [PMID: 37039476 PMCID: PMC10147378 DOI: 10.7554/elife.84382] [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: 10/22/2022] [Accepted: 04/06/2023] [Indexed: 04/12/2023] Open
Abstract
Mutations in the ubiquitin (Ub) chaperone Ubiquilin 2 (UBQLN2) cause X-linked forms of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) through unknown mechanisms. Here, we show that aggregation-prone, ALS-associated mutants of UBQLN2 (UBQLN2ALS) trigger heat stress-dependent neurodegeneration in Drosophila. A genetic modifier screen implicated endolysosomal and axon guidance genes, including the netrin receptor, Unc-5, as key modulators of UBQLN2 toxicity. Reduced gene dosage of Unc-5 or its coreceptor Dcc/frazzled diminished neurodegenerative phenotypes, including motor dysfunction, neuromuscular junction defects, and shortened lifespan, in flies expressing UBQLN2ALS alleles. Induced pluripotent stem cells (iPSCs) harboring UBQLN2ALS knockin mutations exhibited lysosomal defects while inducible motor neurons (iMNs) expressing UBQLN2ALS alleles exhibited cytosolic UBQLN2 inclusions, reduced neurite complexity, and growth cone defects that were partially reversed by silencing of UNC5B and DCC. The combined findings suggest that altered growth cone dynamics are a conserved pathomechanism in UBQLN2-associated ALS/FTD.
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Affiliation(s)
- Sang Hwa Kim
- Department of Human Oncology, University of Wisconsin School of Medicine and Public HealthMadisonUnited States
| | - Kye D Nichols
- Department of Human Oncology, University of Wisconsin School of Medicine and Public HealthMadisonUnited States
| | - Eric N Anderson
- Department of Pediatrics, Children's Hospital of Pittsburgh, University of Pittsburgh Medical CenterPittsburghUnited States
| | - Yining Liu
- Department of Human Oncology, University of Wisconsin School of Medicine and Public HealthMadisonUnited States
| | - Nandini Ramesh
- Department of Pediatrics, Children's Hospital of Pittsburgh, University of Pittsburgh Medical CenterPittsburghUnited States
| | - Weiyan Jia
- Department of Human Oncology, University of Wisconsin School of Medicine and Public HealthMadisonUnited States
| | - Connor J Kuerbis
- Department of Human Oncology, University of Wisconsin School of Medicine and Public HealthMadisonUnited States
| | - Mark Scalf
- Department of Chemistry, University of Wisconsin-MadisonMadisonUnited States
| | - Lloyd M Smith
- Department of Chemistry, University of Wisconsin-MadisonMadisonUnited States
| | - Udai Bhan Pandey
- Department of Pediatrics, Children's Hospital of Pittsburgh, University of Pittsburgh Medical CenterPittsburghUnited States
| | - Randal S Tibbetts
- Department of Human Oncology, University of Wisconsin School of Medicine and Public HealthMadisonUnited States
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7
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Black HH, Hanson JL, Roberts JE, Leslie SN, Campodonico W, Ebmeier CC, Holling GA, Tay JW, Matthews AM, Ung E, Lau CI, Whiteley AM. UBQLN2 restrains the domesticated retrotransposon PEG10 to maintain neuronal health in ALS. eLife 2023; 12:e79452. [PMID: 36951542 PMCID: PMC10076021 DOI: 10.7554/elife.79452] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Accepted: 03/15/2023] [Indexed: 03/24/2023] Open
Abstract
Amyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive motor neuron dysfunction and loss. A portion of ALS cases are caused by mutation of the proteasome shuttle factor Ubiquilin 2 (UBQLN2), but the molecular pathway leading from UBQLN2 dysfunction to disease remains unclear. Here, we demonstrate that UBQLN2 regulates the domesticated gag-pol retrotransposon 'paternally expressed gene 10 (PEG10)' in human cells and tissues. In cells, the PEG10 gag-pol protein cleaves itself in a mechanism reminiscent of retrotransposon self-processing to generate a liberated 'nucleocapsid' fragment, which uniquely localizes to the nucleus and changes the expression of genes involved in axon remodeling. In spinal cord tissue from ALS patients, PEG10 gag-pol is elevated compared to healthy controls. These findings implicate the retrotransposon-like activity of PEG10 as a contributing mechanism in ALS through the regulation of gene expression, and restraint of PEG10 as a primary function of UBQLN2.
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Affiliation(s)
- Holly H Black
- Department of Biochemistry, University of Colorado BoulderBoulderUnited States
| | - Jessica L Hanson
- Institute for Behavioral Genetics, University of Colorado BoulderBoulderUnited States
| | - Julia E Roberts
- Department of Biochemistry, University of Colorado BoulderBoulderUnited States
| | - Shannon N Leslie
- Department of Biochemistry, University of Colorado BoulderBoulderUnited States
| | - Will Campodonico
- Department of Biochemistry, University of Colorado BoulderBoulderUnited States
| | | | - G Aaron Holling
- Department of Biochemistry, University of Colorado BoulderBoulderUnited States
| | - Jian Wei Tay
- Biofrontiers Institute, University of Colorado BoulderBoulderUnited States
| | - Autumn M Matthews
- Department of Biochemistry, University of Colorado BoulderBoulderUnited States
| | - Elizabeth Ung
- Department of Biochemistry, University of Colorado BoulderBoulderUnited States
| | - Cristina I Lau
- Department of Biochemistry, University of Colorado BoulderBoulderUnited States
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8
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Farag M, Borcherds WM, Bremer A, Mittag T, Pappu RV. Phase Separation in Mixtures of Prion-Like Low Complexity Domains is Driven by the Interplay of Homotypic and Heterotypic Interactions. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.15.532828. [PMID: 36993212 PMCID: PMC10055064 DOI: 10.1101/2023.03.15.532828] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Prion-like low-complexity domains (PLCDs) are involved in the formation and regulation of distinct biomolecular condensates that form via coupled associative and segregative phase transitions. We previously deciphered how evolutionarily conserved sequence features drive phase separation of PLCDs through homotypic interactions. However, condensates typically encompass a diverse mixture of proteins with PLCDs. Here, we combine simulations and experiments to study mixtures of PLCDs from two RNA binding proteins namely, hnRNPA1 and FUS. We find that 1:1 mixtures of the A1-LCD and FUS-LCD undergo phase separation more readily than either of the PLCDs on their own. The enhanced driving forces for phase separation of mixtures of A1-LCD and FUS-LCD arise partly from complementary electrostatic interactions between the two proteins. This complex coacervation-like mechanism adds to complementary interactions among aromatic residues. Further, tie line analysis shows that stoichiometric ratios of different components and their sequence-encoded interactions jointly contribute to the driving forces for condensate formation. These results highlight how expression levels might be tuned to regulate the driving forces for condensate formation in vivo . Simulations also show that the organization of PLCDs within condensates deviates from expectations based on random mixture models. Instead, spatial organization within condensates will reflect the relative strengths of homotypic versus heterotypic interactions. We also uncover rules for how interaction strengths and sequence lengths modulate conformational preferences of molecules at interfaces of condensates formed by mixtures of proteins. Overall, our findings emphasize the network-like organization of molecules within multicomponent condensates, and the distinctive, composition-specific conformational features of condensate interfaces. Significance Statement Biomolecular condensates are mixtures of different protein and nucleic acid molecules that organize biochemical reactions in cells. Much of what we know about how condensates form comes from studies of phase transitions of individual components of condensates. Here, we report results from studies of phase transitions of mixtures of archetypal protein domains that feature in distinct condensates. Our investigations, aided by a blend of computations and experiments, show that the phase transitions of mixtures are governed by a complex interplay of homotypic and heterotypic interactions. The results point to how expression levels of different protein components can be tuned in cells to modulate internal structures, compositions, and interfaces of condensates, thus affording distinct ways to control the functions of condensates.
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9
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Grønbæk-Thygesen M, Kampmeyer C, Hofmann K, Hartmann-Petersen R. The moonlighting of RAD23 in DNA repair and protein degradation. BIOCHIMICA ET BIOPHYSICA ACTA. GENE REGULATORY MECHANISMS 2023; 1866:194925. [PMID: 36863450 DOI: 10.1016/j.bbagrm.2023.194925] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2022] [Revised: 02/20/2023] [Accepted: 02/23/2023] [Indexed: 03/04/2023]
Abstract
A moonlighting protein is one, which carries out multiple, often wholly unrelated, functions. The RAD23 protein is a fascinating example of this, where the same polypeptide and the embedded domains function independently in both nucleotide excision repair (NER) and protein degradation via the ubiquitin-proteasome system (UPS). Hence, through direct binding to the central NER component XPC, RAD23 stabilizes XPC and contributes to DNA damage recognition. Conversely, RAD23 also interacts directly with the 26S proteasome and ubiquitylated substrates to mediate proteasomal substrate recognition. In this function, RAD23 activates the proteolytic activity of the proteasome and engages specifically in well-characterized degradation pathways through direct interactions with E3 ubiquitin-protein ligases and other UPS components. Here, we summarize the past 40 years of research into the roles of RAD23 in NER and the UPS.
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Affiliation(s)
- Martin Grønbæk-Thygesen
- The Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Denmark.
| | - Caroline Kampmeyer
- The Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Denmark
| | - Kay Hofmann
- Institute for Genetics, University of Cologne, Germany
| | - Rasmus Hartmann-Petersen
- The Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Denmark.
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10
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Raymond-Smiedy P, Bucknor B, Yang Y, Zheng T, Castañeda CA. A Spectrophotometric Turbidity Assay to Study Liquid-Liquid Phase Separation of UBQLN2 In Vitro. Methods Mol Biol 2023; 2551:515-541. [PMID: 36310223 DOI: 10.1007/978-1-0716-2597-2_32] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Liquid-liquid phase separation (LLPS) is hypothesized to be the underlying mechanism for how membraneless organelles or biomolecular condensates form inside both prokaryotic and eukaryotic cells. Protein LLPS is a biophysical process during which proteins demix from homogeneous solution to form protein-dense droplets with liquid-like properties. Disruptions to LLPS, such as changes to material properties of condensates or physicochemical parameters for LLPS onset, are implicated in neurodegenerative diseases and cancer. Therefore, it is essential to determine the physicochemical parameters that promote protein LLPS. Here, we present our UV-Vis spectrophotometric turbidity assay to characterize the temperature and concentration dependence of LLPS for UBQLN2, a protein that undergoes LLPS via homotypic interactions in vitro and forms stress-induced condensates in cells. Mutations in UBQLN2 cause amyotrophic lateral sclerosis (ALS) and disrupt UBQLN2 LLPS. We present a detailed expression and purification protocol for a C-terminal construct of UBQLN2 and how we use microscopy to image UBQLN2 LLPS. We use our UV-Vis assay to construct temperature-concentration phase diagrams for wild-type and mutant UBQLN2 constructs to determine the effects of domain deletions and/or mutations on UBQLN2 phase separation.
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Affiliation(s)
| | - Barrington Bucknor
- Department of Biology, Syracuse University, Syracuse, NY, USA
- Department of Chemistry, Syracuse University, Syracuse, NY, USA
- Program in Neuroscience, Syracuse University, Syracuse, NY, USA
| | - Yiran Yang
- Department of Chemistry, Syracuse University, Syracuse, NY, USA
| | - Tongyin Zheng
- Department of Chemistry, Syracuse University, Syracuse, NY, USA
| | - Carlos A Castañeda
- Department of Biology, Syracuse University, Syracuse, NY, USA.
- Department of Chemistry, Syracuse University, Syracuse, NY, USA.
- Program in Neuroscience, Syracuse University, Syracuse, NY, USA.
- BioInspired Institute, Syracuse University, Syracuse, NY, USA.
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11
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Mohanty P, Kapoor U, Sundaravadivelu Devarajan D, Phan TM, Rizuan A, Mittal J. Principles Governing the Phase Separation of Multidomain Proteins. Biochemistry 2022; 61:2443-2455. [PMID: 35802394 PMCID: PMC9669140 DOI: 10.1021/acs.biochem.2c00210] [Citation(s) in RCA: 37] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
A variety of membraneless organelles, often termed "biological condensates", play an important role in the regulation of cellular processes such as gene transcription, translation, and protein quality control. On the basis of experimental and theoretical investigations, liquid-liquid phase separation (LLPS) has been proposed as a possible mechanism for the origin of biological condensates. LLPS requires multivalent macromolecules that template the formation of long-range, intermolecular interaction networks and results in the formation of condensates with defined composition and material properties. Multivalent interactions driving LLPS exhibit a wide range of modes from highly stereospecific to nonspecific and involve both folded and disordered regions. Multidomain proteins serve as suitable macromolecules for promoting phase separation and achieving disparate functions due to their potential for multivalent interactions and regulation. Here, we aim to highlight the influence of the domain architecture and interdomain interactions on the phase separation of multidomain protein condensates. First, the general principles underlying these interactions are illustrated on the basis of examples of multidomain proteins that are predominantly associated with nucleic acid binding and protein quality control and contain both folded and disordered regions. Next, the examples showcase how LLPS properties of folded and disordered regions can be leveraged to engineer multidomain constructs that form condensates with the desired assembly and functional properties. Finally, we highlight the need for improvements in coarse-grained computational models that can provide molecular-level insights into multidomain protein condensates in conjunction with experimental efforts.
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Affiliation(s)
- Priyesh Mohanty
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, TX 77843
| | - Utkarsh Kapoor
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, TX 77843
| | | | - Tien Minh Phan
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, TX 77843
| | - Azamat Rizuan
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, TX 77843
| | - Jeetain Mittal
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, TX 77843
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12
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Lin BC, Higgins NR, Phung TH, Monteiro MJ. UBQLN proteins in health and disease with a focus on UBQLN2 in ALS/FTD. FEBS J 2022; 289:6132-6153. [PMID: 34273246 PMCID: PMC8761781 DOI: 10.1111/febs.16129] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 07/08/2021] [Accepted: 07/16/2021] [Indexed: 01/12/2023]
Abstract
Ubiquilin (UBQLN) proteins are a dynamic and versatile family of proteins found in all eukaryotes that function in the regulation of proteostasis. Besides their canonical function as shuttle factors in delivering misfolded proteins to the proteasome and autophagy systems for degradation, there is emerging evidence that UBQLN proteins play broader roles in proteostasis. New information suggests the proteins function as chaperones in protein folding, protecting proteins prior to membrane insertion, and as guardians for mitochondrial protein import. In this review, we describe the evidence for these different roles, highlighting how different domains of the proteins impart these functions. We also describe how changes in the structure and phase separation properties of UBQLNs may regulate their activity and function. Finally, we discuss the pathogenic mechanisms by which mutations in UBQLN2 cause amyotrophic lateral sclerosis and frontotemporal dementia. We describe the animal model systems made for different UBQLN2 mutations and how lessons learnt from these systems provide fundamental insight into the molecular mechanisms by which UBQLN2 mutations drive disease pathogenesis through disturbances in proteostasis.
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Affiliation(s)
- Brian C. Lin
- Program in Neuroscience, University of Maryland School of Medicine, Baltimore, MD, USA,Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD, USA,Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Nicole R. Higgins
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD, USA,Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD, USA,Program in Molecular Medicine, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Trong H. Phung
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD, USA,Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Mervyn J. Monteiro
- Program in Neuroscience, University of Maryland School of Medicine, Baltimore, MD, USA,Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD, USA,Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD, USA,Program in Molecular Medicine, University of Maryland School of Medicine, Baltimore, MD, USA
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13
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Tirincsi A, O’Keefe S, Nguyen D, Sicking M, Dudek J, Förster F, Jung M, Hadzibeganovic D, Helms V, High S, Zimmermann R, Lang S. Proteomics Identifies Substrates and a Novel Component in hSnd2-Dependent ER Protein Targeting. Cells 2022; 11:cells11182925. [PMID: 36139500 PMCID: PMC9496750 DOI: 10.3390/cells11182925] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Revised: 09/07/2022] [Accepted: 09/13/2022] [Indexed: 11/16/2022] Open
Abstract
Importing proteins into the endoplasmic reticulum (ER) is essential for about 30% of the human proteome. It involves the targeting of precursor proteins to the ER and their insertion into or translocation across the ER membrane. Furthermore, it relies on signals in the precursor polypeptides and components, which read the signals and facilitate their targeting to a protein-conducting channel in the ER membrane, the Sec61 complex. Compared to the SRP- and TRC-dependent pathways, little is known about the SRP-independent/SND pathway. Our aim was to identify additional components and characterize the client spectrum of the human SND pathway. The established strategy of combining the depletion of the central hSnd2 component from HeLa cells with proteomic and differential protein abundance analysis was used. The SRP and TRC targeting pathways were analyzed in comparison. TMEM109 was characterized as hSnd3. Unlike SRP but similar to TRC, the SND clients are predominantly membrane proteins with N-terminal, central, or C-terminal targeting signals.
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Affiliation(s)
- Andrea Tirincsi
- Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany
| | - Sarah O’Keefe
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PT, UK
| | - Duy Nguyen
- Center for Bioinformatics, Saarland University, 66041 Saarbrücken, Germany
| | - Mark Sicking
- Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany
| | - Johanna Dudek
- Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany
| | - Friedrich Förster
- Bijvoet Center for Biomolecular Research, Utrecht University, 3584 CH Utrecht, The Netherlands
| | - Martin Jung
- Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany
| | | | - Volkhard Helms
- Center for Bioinformatics, Saarland University, 66041 Saarbrücken, Germany
| | - Stephen High
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PT, UK
| | - Richard Zimmermann
- Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany
- Correspondence: (R.Z.); (S.L.)
| | - Sven Lang
- Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany
- Correspondence: (R.Z.); (S.L.)
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14
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Kaur S, Saldana AC, Elkahloun AG, Petersen JD, Arakelyan A, Singh SP, Jenkins LM, Kuo B, Reginauld B, Jordan DG, Tran AD, Wu W, Zimmerberg J, Margolis L, Roberts DD. CD47 interactions with exportin-1 limit the targeting of m 7G-modified RNAs to extracellular vesicles. J Cell Commun Signal 2022; 16:397-419. [PMID: 34841476 PMCID: PMC9411329 DOI: 10.1007/s12079-021-00646-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Accepted: 09/09/2021] [Indexed: 12/14/2022] Open
Abstract
CD47 is a marker of self and a signaling receptor for thrombospondin-1 that is also a component of extracellular vesicles (EVs) released by various cell types. Previous studies identified CD47-dependent functional effects of T cell EVs on target cells, mediated by delivery of their RNA contents, and enrichment of specific subsets of coding and noncoding RNAs in CD47+ EVs. Mass spectrometry was employed here to identify potential mechanisms by which CD47 regulates the trafficking of specific RNAs to EVs. Specific interactions of CD47 and its cytoplasmic adapter ubiquilin-1 with components of the exportin-1/Ran nuclear export complex were identified and confirmed by coimmunoprecipitation. Exportin-1 is known to regulate nuclear to cytoplasmic trafficking of 5'-7-methylguanosine (m7G)-modified microRNAs and mRNAs that interact with its cargo protein EIF4E. Interaction with CD47 was inhibited following alkylation of exportin-1 at Cys528 by its covalent inhibitor leptomycin B. Leptomycin B increased levels of m7G-modified RNAs, and their association with exportin-1 in EVs released from wild type but not CD47-deficient cells. In addition to perturbing nuclear to cytoplasmic transport, transcriptomic analyses of EVs released by wild type and CD47-deficient Jurkat T cells revealed a global CD47-dependent enrichment of m7G-modified microRNAs and mRNAs in EVs released by CD47-deficient cells. Correspondingly, decreasing CD47 expression in wild type cells or treatment with thrombospondin-1 enhanced levels of specific m7G-modified RNAs released in EVs, and re-expressing CD47 in CD47-deficient T cells decreased their levels. Therefore, CD47 signaling limits the trafficking of m7G-modified RNAs to EVs through physical interactions with the exportin-1/Ran transport complex.
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Affiliation(s)
- Sukhbir Kaur
- Laboratory of Pathology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Building 10 Room 2S235, 10 Center Dr, Bethesda, MD, 20892-1500, USA
| | - Alejandra Cavazos Saldana
- Laboratory of Pathology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Building 10 Room 2S235, 10 Center Dr, Bethesda, MD, 20892-1500, USA
| | - Abdel G Elkahloun
- Cancer Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, USA
| | - Jennifer D Petersen
- Section On Integrative Biophysics, Division of Basic and Translational Biophysics, Eunice Kennedy-Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, USA
| | - Anush Arakelyan
- Section On Intercellular Interactions, Division of Basic and Translational Biophysics, Eunice Kennedy-Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, USA
| | - Satya P Singh
- Inflammation Biology Section, Laboratory of Molecular Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, USA
| | - Lisa M Jenkins
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, USA
| | - Bethany Kuo
- Laboratory of Pathology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Building 10 Room 2S235, 10 Center Dr, Bethesda, MD, 20892-1500, USA
| | - Bianca Reginauld
- Laboratory of Pathology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Building 10 Room 2S235, 10 Center Dr, Bethesda, MD, 20892-1500, USA
| | - David G Jordan
- Laboratory of Pathology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Building 10 Room 2S235, 10 Center Dr, Bethesda, MD, 20892-1500, USA
| | - Andy D Tran
- Confocal Microscopy Core Facility, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, USA
| | - Weiwei Wu
- Cancer Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, USA
| | - Joshua Zimmerberg
- Section On Integrative Biophysics, Division of Basic and Translational Biophysics, Eunice Kennedy-Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, USA
| | - Leonid Margolis
- Section On Intercellular Interactions, Division of Basic and Translational Biophysics, Eunice Kennedy-Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, USA
| | - David D Roberts
- Laboratory of Pathology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Building 10 Room 2S235, 10 Center Dr, Bethesda, MD, 20892-1500, USA.
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15
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Substrate spectrum of PPM1D in the cellular response to DNA double-strand breaks. iScience 2022; 25:104892. [PMID: 36060052 PMCID: PMC9436757 DOI: 10.1016/j.isci.2022.104892] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 07/03/2022] [Accepted: 08/02/2022] [Indexed: 12/03/2022] Open
Abstract
PPM1D is a p53-regulated protein phosphatase that modulates the DNA damage response (DDR) and is frequently altered in cancer. Here, we employed chemical inhibition of PPM1D and quantitative mass spectrometry-based phosphoproteomics to identify the substrates of PPM1D upon induction of DNA double-strand breaks (DSBs) by etoposide. We identified 73 putative PPM1D substrates that are involved in DNA repair, regulation of transcription, and RNA processing. One-third of DSB-induced S/TQ phosphorylation sites are dephosphorylated by PPM1D, demonstrating that PPM1D only partially counteracts ATM/ATR/DNA-PK signaling. PPM1D-targeted phosphorylation sites are found in a specific amino acid sequence motif that is characterized by glutamic acid residues, high intrinsic disorder, and poor evolutionary conservation. We identified a functionally uncharacterized protein Kanadaptin as ATM and PPM1D substrate upon DSB induction. We propose that PPM1D plays a role during the response to DSBs by regulating the phosphorylation of DNA- and RNA-binding proteins in intrinsically disordered regions. MS-based phosphoproteomic profiling of PPM1D substrates in U2OS and HCT116 cells PPM1D counteracts ATM in the cellular response to DNA double-strand breaks PPM1D target sites localize to glutamic acid-rich regions with high intrinsic disorder Kanadaptin is a putative DNA damage response factor regulated by ATM and PPM1D
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16
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Dao TP, Yang Y, Presti MF, Cosgrove MS, Hopkins JB, Ma W, Loh SN, Castañeda CA. Mechanistic insights into enhancement or inhibition of phase separation by different polyubiquitin chains. EMBO Rep 2022; 23:e55056. [PMID: 35762418 PMCID: PMC9346500 DOI: 10.15252/embr.202255056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Revised: 06/06/2022] [Accepted: 06/08/2022] [Indexed: 12/03/2022] Open
Abstract
Ubiquitin‐binding shuttle UBQLN2 mediates crosstalk between proteasomal degradation and autophagy, likely via interactions with K48‐ and K63‐linked polyubiquitin chains, respectively. UBQLN2 comprises self‐associating regions that drive its homotypic liquid–liquid phase separation (LLPS). Specific interactions between one of these regions and ubiquitin inhibit UBQLN2 LLPS. Here, we show that, unlike ubiquitin, the effects of multivalent polyubiquitin chains on UBQLN2 LLPS are highly dependent on chain types. Specifically, K11‐Ub4 and K48‐Ub4 chains generally inhibit UBQLN2 LLPS, whereas K63‐Ub4, M1‐Ub4 chains, and a designed tetrameric ubiquitin construct significantly enhance LLPS. We demonstrate that these opposing effects stem from differences in chain conformations but not in affinities between chains and UBQLN2. Chains with extended conformations and increased accessibility to the ubiquitin‐binding surface promote UBQLN2 LLPS by enabling a switch between homotypic to partially heterotypic LLPS that is driven by both UBQLN2 self‐interactions and interactions between multiple UBQLN2 units with each polyubiquitin chain. Our study provides mechanistic insights into how the structural and conformational properties of polyubiquitin chains contribute to heterotypic LLPS with ubiquitin‐binding shuttles and adaptors.
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Affiliation(s)
- Thuy P Dao
- Departments of Biology and Chemistry Syracuse University Syracuse NY USA
| | - Yiran Yang
- Department of Chemistry Syracuse University Syracuse NY USA
| | - Maria F Presti
- Department of Biochemistry and Molecular Biology SUNY Upstate Medical University Syracuse NY USA
| | - Michael S Cosgrove
- Department of Biochemistry and Molecular Biology SUNY Upstate Medical University Syracuse NY USA
| | - Jesse B Hopkins
- The Biophysics Collaborative Access Team (BioCAT), Department of Biological Sciences Illinois Institute of Technology Chicago IL USA
| | - Weikang Ma
- The Biophysics Collaborative Access Team (BioCAT), Department of Biological Sciences Illinois Institute of Technology Chicago IL USA
| | - Stewart N Loh
- Department of Biochemistry and Molecular Biology SUNY Upstate Medical University Syracuse NY USA
| | - Carlos A Castañeda
- Departments of Biology and Chemistry Syracuse University Syracuse NY USA
- Interdisciplinary Neuroscience Program Syracuse University Syracuse NY USA
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17
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Mohan HM, Trzeciakiewicz H, Pithadia A, Crowley EV, Pacitto R, Safren N, Trotter B, Zhang C, Zhou X, Zhang Y, Basrur V, Paulson HL, Sharkey LM. RTL8 promotes nuclear localization of UBQLN2 to subnuclear compartments associated with protein quality control. Cell Mol Life Sci 2022; 79:176. [PMID: 35247097 PMCID: PMC9376861 DOI: 10.1007/s00018-022-04170-z] [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: 04/19/2021] [Revised: 01/17/2022] [Accepted: 01/25/2022] [Indexed: 11/24/2022]
Abstract
The brain-expressed ubiquilins (UBQLNs) 1, 2 and 4 are a family of ubiquitin adaptor proteins that participate broadly in protein quality control (PQC) pathways, including the ubiquitin proteasome system (UPS). One family member, UBQLN2, has been implicated in numerous neurodegenerative diseases including ALS/FTD. UBQLN2 typically resides in the cytoplasm but in disease can translocate to the nucleus, as in Huntington's disease where it promotes the clearance of mutant Huntingtin. How UBQLN2 translocates to the nucleus and clears aberrant nuclear proteins, however, is not well understood. In a mass spectrometry screen to discover UBQLN2 interactors, we identified a family of small (13 kDa), highly homologous uncharacterized proteins, RTL8, and confirmed the interaction between UBQLN2 and RTL8 both in vitro using recombinant proteins and in vivo using mouse brain tissue. Under endogenous and overexpressed conditions, RTL8 localizes to nucleoli. When co-expressed with UBQLN2, RTL8 promotes nuclear translocation of UBQLN2. RTL8 also facilitates UBQLN2's nuclear translocation during heat shock. UBQLN2 and RTL8 colocalize within ubiquitin-enriched subnuclear structures containing PQC components. The robust effect of RTL8 on the nuclear translocation and subnuclear localization of UBQLN2 does not extend to the other brain-expressed ubiquilins, UBQLN1 and UBQLN4. Moreover, compared to UBQLN1 and UBQLN4, UBQLN2 preferentially stabilizes RTL8 levels in human cell lines and in mouse brain, supporting functional heterogeneity among UBQLNs. As a novel UBQLN2 interactor that recruits UBQLN2 to specific nuclear compartments, RTL8 may regulate UBQLN2 function in nuclear protein quality control.
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Affiliation(s)
- Harihar Milaganur Mohan
- Department of Neurology, University of Michigan, Ann Arbor, MI, 48109-2200, USA.,Graduate Program in Cellular and Molecular Biology, University of Michigan, Ann Arbor, MI, 48109-2200, USA
| | | | - Amit Pithadia
- Department of Neurology, University of Michigan, Ann Arbor, MI, 48109-2200, USA
| | - Emily V Crowley
- Department of Neurology, University of Michigan, Ann Arbor, MI, 48109-2200, USA
| | - Regina Pacitto
- Department of Neurology, University of Michigan, Ann Arbor, MI, 48109-2200, USA
| | - Nathaniel Safren
- Department of Neurology, University of Michigan, Ann Arbor, MI, 48109-2200, USA.,Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL, 60611, USA
| | - Bryce Trotter
- Department of Neurology, University of Michigan, Ann Arbor, MI, 48109-2200, USA
| | - Chengxin Zhang
- Department of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, MI, 48109-2200, USA
| | - Xiaogen Zhou
- Department of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, MI, 48109-2200, USA
| | - Yang Zhang
- Department of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, MI, 48109-2200, USA
| | - Venkatesha Basrur
- Department of Pathology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
| | - Henry L Paulson
- Department of Neurology, University of Michigan, Ann Arbor, MI, 48109-2200, USA. .,Michigan Neuroscience Institute, University of Michigan, Ann Arbor, MI, 48109-2200, USA.
| | - Lisa M Sharkey
- Department of Neurology, University of Michigan, Ann Arbor, MI, 48109-2200, USA. .,Michigan Neuroscience Institute, University of Michigan, Ann Arbor, MI, 48109-2200, USA.
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18
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Tzou FY, Wen JK, Yeh JY, Huang SY, Chen GC, Chan CC. Drosophila as a model to study autophagy in neurodegenerative diseases and digestive tract. IUBMB Life 2021; 74:339-360. [PMID: 34874101 DOI: 10.1002/iub.2583] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2021] [Revised: 11/08/2021] [Accepted: 11/15/2021] [Indexed: 12/20/2022]
Abstract
Autophagy regulates cellular homeostasis by degrading and recycling cytosolic components and damaged organelles. Disruption of autophagic flux has been shown to induce or facilitate neurodegeneration and accumulation of autophagic vesicles is overt in neurodegenerative diseases. The fruit fly Drosophila has been used as a model system to identify new factors that regulate physiology and disease. Here we provide a historical perspective of how the fly models have offered mechanistic evidence to understand the role of autophagy in neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, Charcot-Marie-Tooth neuropathy, and polyglutamine disorders. Autophagy also plays a pivotal role in maintaining tissue homeostasis and protecting organism health. The gastrointestinal tract regulates organism health by modulating food intake, energy balance, and immunity. Growing evidence is strengthening the link between autophagy and digestive tract health in recent years. Here, we also discuss how the fly models have advanced the understanding of digestive physiology regulated by autophagy.
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Affiliation(s)
- Fei-Yang Tzou
- Graduate Institute of Physiology, National Taiwan University, Taipei, Taiwan
| | - Jung-Kun Wen
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Jui-Yu Yeh
- Graduate Institute of Physiology, National Taiwan University, Taipei, Taiwan
| | - Shu-Yi Huang
- Department of Medical Research, National Taiwan University Hospital, Taipei, Taiwan
| | - Guang-Chao Chen
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Chih-Chiang Chan
- Graduate Institute of Physiology, National Taiwan University, Taipei, Taiwan
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19
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Bonifacino T, Zerbo RA, Balbi M, Torazza C, Frumento G, Fedele E, Bonanno G, Milanese M. Nearly 30 Years of Animal Models to Study Amyotrophic Lateral Sclerosis: A Historical Overview and Future Perspectives. Int J Mol Sci 2021; 22:ijms222212236. [PMID: 34830115 PMCID: PMC8619465 DOI: 10.3390/ijms222212236] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 11/08/2021] [Accepted: 11/09/2021] [Indexed: 12/20/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a fatal, multigenic, multifactorial, and non-cell autonomous neurodegenerative disease characterized by upper and lower motor neuron loss. Several genetic mutations lead to ALS development and many emerging gene mutations have been discovered in recent years. Over the decades since 1990, several animal models have been generated to study ALS pathology including both vertebrates and invertebrates such as yeast, worms, flies, zebrafish, mice, rats, guinea pigs, dogs, and non-human primates. Although these models show different peculiarities, they are all useful and complementary to dissect the pathological mechanisms at the basis of motor neuron degeneration and ALS progression, thus contributing to the development of new promising therapeutics. In this review, we describe the up to date and available ALS genetic animal models, classified by the different genetic mutations and divided per species, pointing out their features in modeling, the onset and progression of the pathology, as well as their specific pathological hallmarks. Moreover, we highlight similarities, differences, advantages, and limitations, aimed at helping the researcher to select the most appropriate experimental animal model, when designing a preclinical ALS study.
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Affiliation(s)
- Tiziana Bonifacino
- Pharmacology and Toxicology Unit, Department of Pharmacy, University of Genoa, 16148 Genoa, Italy; (T.B.); (R.A.Z.); (M.B.); (C.T.); (G.F.); (G.B.); (M.M.)
- Inter-University Center for the Promotion of the 3Rs Principles in Teaching & Research (Centro 3R), 56122 Genoa, Italy
| | - Roberta Arianna Zerbo
- Pharmacology and Toxicology Unit, Department of Pharmacy, University of Genoa, 16148 Genoa, Italy; (T.B.); (R.A.Z.); (M.B.); (C.T.); (G.F.); (G.B.); (M.M.)
| | - Matilde Balbi
- Pharmacology and Toxicology Unit, Department of Pharmacy, University of Genoa, 16148 Genoa, Italy; (T.B.); (R.A.Z.); (M.B.); (C.T.); (G.F.); (G.B.); (M.M.)
| | - Carola Torazza
- Pharmacology and Toxicology Unit, Department of Pharmacy, University of Genoa, 16148 Genoa, Italy; (T.B.); (R.A.Z.); (M.B.); (C.T.); (G.F.); (G.B.); (M.M.)
| | - Giulia Frumento
- Pharmacology and Toxicology Unit, Department of Pharmacy, University of Genoa, 16148 Genoa, Italy; (T.B.); (R.A.Z.); (M.B.); (C.T.); (G.F.); (G.B.); (M.M.)
| | - Ernesto Fedele
- Pharmacology and Toxicology Unit, Department of Pharmacy, University of Genoa, 16148 Genoa, Italy; (T.B.); (R.A.Z.); (M.B.); (C.T.); (G.F.); (G.B.); (M.M.)
- IRCCS Ospedale Policlinico San Martino, 16132 Genoa, Italy
- Correspondence:
| | - Giambattista Bonanno
- Pharmacology and Toxicology Unit, Department of Pharmacy, University of Genoa, 16148 Genoa, Italy; (T.B.); (R.A.Z.); (M.B.); (C.T.); (G.F.); (G.B.); (M.M.)
- IRCCS Ospedale Policlinico San Martino, 16132 Genoa, Italy
| | - Marco Milanese
- Pharmacology and Toxicology Unit, Department of Pharmacy, University of Genoa, 16148 Genoa, Italy; (T.B.); (R.A.Z.); (M.B.); (C.T.); (G.F.); (G.B.); (M.M.)
- Inter-University Center for the Promotion of the 3Rs Principles in Teaching & Research (Centro 3R), 56122 Genoa, Italy
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20
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A Comprehensive Multiomics Analysis Identified Ubiquilin 4 as a Promising Prognostic Biomarker of Immune-Related Therapy in Pan-Cancer. JOURNAL OF ONCOLOGY 2021; 2021:7404927. [PMID: 34539785 PMCID: PMC8443395 DOI: 10.1155/2021/7404927] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Accepted: 08/28/2021] [Indexed: 01/02/2023]
Abstract
Recently, it was reported that ubiquilin 4 (UBQLN4) alteration was associated with genomic instability in some cancers. However, whether UBQLN4 is a valuable biomarker for the prognosis of immunotherapy in pan-cancer was not identified. We evaluated the biologic and oncologic significance of UBQLN4 in pan-cancer at multiomics level, such as expression, mutation, copy number variation (CNV), methylation, and N6-methyladenosine (m6A) methylation. These omics data were obtained from several public databases, including Oncomine, The Cancer Genome Atlas (TCGA), Gene Expression Omnibus (GEO), the Genotype-Tissue Expression (GTEx), the Human Protein Atlas (HPA), Gene Set Cancer Analysis (GSCA), m6A-Atlas, CancerSEA, and RNAactDrug. We found that UBQLN4 mRNA and protein were overexpressed in most cancer types, and the expression, mutation, CNV, and methylation of UBQLN4 were associated with the prognosis of some cancers. Mechanistically, UBQLN4 was involved in angiogenesis, DNA damage, apoptosis, and the pathway of PI3K/AKT and TSC/mTOR. Moreover, UBQLN4 mRNA was significantly correlated with immune checkpoints, tumor mutational burden (TMB), microsatellite instability (MSI), and mismatch repair (MMR). And, the correlation among UBQLN4 mRNA, CNV, and methylation and immune microenvironment was also identified. Furthermore, UBQLN4 was associated with the sensitivity of chemotherapy and targeted drugs at multiomics level. In conclusion, UBQLN4 was a promising prognostic biomarker of immune-related therapy in pan-cancer.
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21
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Park JS, Ma H, Roh YS. Ubiquitin pathways regulate the pathogenesis of chronic liver disease. Biochem Pharmacol 2021; 193:114764. [PMID: 34529948 DOI: 10.1016/j.bcp.2021.114764] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Revised: 09/05/2021] [Accepted: 09/08/2021] [Indexed: 02/07/2023]
Abstract
Chronic liver disease (CLD) is considered the leading cause of global mortality. In westernized countries, increased consumption of alcohol and overeating foods with high fat/ high glucose promote progression of CLD such as alcoholic liver disease (ALD) and non-alcoholic liver disease (NAFLD). Accumulating evidence and research suggest that ubiquitin, a 75 amino acid protein, plays crucial role in the pathogenesis of CLD through dynamic post-translational modifications (PTMs) exerting diverse cellular outcomes such as protein degradation through ubiquitin-proteasome system (UPS) and autophagy, and regulation of signal transduction. In this review, we present the function of ubiquitination and latest findings on diverse mechanism of PTMs, UPS and autophagy which significantly contribute to the pathogenesis of alcoholic liver disease (ALD), non-alcoholic fatty liver disease (NAFLD), cirrhosis, and HCC. Despite its high prevalence, morbidity, and mortality, there are only few FDA approved drugs that could be administered to CLD patients. The goal of this review is to present a variety of pathways and therapeutic targets involving ubiquitination in the pathogenesis of CLD. Further, this review summarizes collective views of pharmaceutical inhibition or activation of recent drugs targeting UPS and autophagy system to highlight potential targets and new approaches to treat CLD.
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Affiliation(s)
- Jeong-Su Park
- College of Pharmacy and Medical Research Center, Chungbuk National University, Cheongju 28160, South Korea
| | - Hwan Ma
- College of Pharmacy and Medical Research Center, Chungbuk National University, Cheongju 28160, South Korea
| | - Yoon-Seok Roh
- College of Pharmacy and Medical Research Center, Chungbuk National University, Cheongju 28160, South Korea.
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22
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Higgins NR, Greenslade JE, Wu JJ, Miranda E, Galliciotti G, Monteiro MJ. Serpin neuropathology in the P497S UBQLN2 mouse model of ALS/FTD. Brain Pathol 2021; 31:e12948. [PMID: 33780087 PMCID: PMC8387369 DOI: 10.1111/bpa.12948] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Revised: 02/17/2021] [Accepted: 03/08/2021] [Indexed: 01/12/2023] Open
Abstract
Accumulating evidence suggests X-linked dominant mutations in UBQLN2 cause amyotrophic lateral sclerosis (ALS) with frontotemporal dementia (FTD) through both loss- and gain-of-function mechanisms. However, the mechanisms by which the mutations cause disease are still unclear. The goal of the study was to uncover the possible pathomechanism(s) by which UBQLN2 mutations cause ALS/FTD. An analysis of proteomic changes in neuronal tissue was used to identify proteins with altered accumulation in the P497S UBQLN2 transgenic mouse model of ALS/FTD. We then used immunocytochemistry and biochemical techniques to confirm protein changes in the mutant P497S mice. Additionally, we used cell lines inactivated of UBQLN2 expression to determine whether its loss underlies the alteration in the proteins seen in P497S mice. The proteome screen identified a dramatic alteration of serine protease inhibitor (serpin) proteins in the mutant P497S animals. Double immunofluorescent staining of brain and spinal cord tissues of the mutant and control mice revealed an age-dependent change in accumulation of Serpin A1, C1, and I1 in puncta whose staining colocalized with UBQLN2 puncta in the mutant P497S mice. Serpin A1 aggregation in P497S animals was confirmed by biochemical extraction and filter retardation assays. A similar phenomenon of serpin protein aggregation was found in HeLa and NSC34 motor neuron cells with inactivated UBQLN2 expression. We found aberrant aggregation of serpin proteins, particularly Serpin A1, in the brain and spinal cord of the P497S UBQLN2 mouse model of ALS/FTD. Similar aggregation of serpin proteins was found in UBQLN2 knockout cells suggesting that serpin aggregation in the mutant P497S animals may stem from loss of UBQLN2 function. Because serpin aggregation is known to cause disease through both loss- and gain-of-function mechanisms, we speculate that their accumulation in the P497S mouse model of ALS/FTD may contribute to disease pathogenesis through similar mechanism(s).
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Affiliation(s)
- Nicole R. Higgins
- Program in Molecular MedicineUniversity of Maryland School of MedicineBaltimoreMDUSA
- Center for Biomedical Engineering and TechnologyDepartment of Anatomy and NeurobiologyUniversity of Maryland School of MedicineBaltimoreMDUSA
| | - Jessie E. Greenslade
- Center for Biomedical Engineering and TechnologyDepartment of Anatomy and NeurobiologyUniversity of Maryland School of MedicineBaltimoreMDUSA
| | - Josephine J. Wu
- Center for Biomedical Engineering and TechnologyDepartment of Anatomy and NeurobiologyUniversity of Maryland School of MedicineBaltimoreMDUSA
| | - Elena Miranda
- Department of Biology and Biotechnologies ‘Charles Darwin’Pasteur Institute – Cenci Bolognetti FoundationSapienza University of RomeRomeItaly
| | - Giovanna Galliciotti
- Institute of NeuropathologyUniversity Medical Center Hamburg‐EppendorfHamburgGermany
| | - Mervyn J. Monteiro
- Program in Molecular MedicineUniversity of Maryland School of MedicineBaltimoreMDUSA
- Center for Biomedical Engineering and TechnologyDepartment of Anatomy and NeurobiologyUniversity of Maryland School of MedicineBaltimoreMDUSA
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23
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Riley JF, Fioramonti PJ, Rusnock AK, Hehnly H, Castañeda CA. ALS-linked mutations impair UBQLN2 stress-induced biomolecular condensate assembly in cells. J Neurochem 2021; 159:145-155. [PMID: 34129687 DOI: 10.1111/jnc.15453] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 05/30/2021] [Accepted: 06/13/2021] [Indexed: 11/28/2022]
Abstract
Mutations in Ubiquilin-2 (UBQLN2), a ubiquitin-binding shuttle protein involved in several protein quality control processes, can lead to amyotrophic lateral sclerosis (ALS). We previously found that wild-type UBQLN2 forms dynamic, membraneless biomolecular condensates upon cellular stress, and undergoes liquid-liquid phase separation in vitro. However, the impact of ALS-linked mutations on UBQLN2 condensate formation in cells is unknown. Here, we employ live-cell imaging and photokinetic analysis to investigate how five patient-derived ALS-linked mutations in UBQLN2 impact stress-induced UBQLN2 condensate assembly and condensate material properties. Both wild-type and mutant UBQLN2 condensates are generally cytoplasmic and liquid-like. However, cells transfected with mutant UBQLN2 contain fewer stress-induced UBQLN2 condensates than those with wild-type UBQLN2. Most strikingly, exogenously expressed P506T UBQLN2 forms the lowest number of stress-induced condensates of all UBQLN2 mutants, and these condensates are significantly smaller than those of wild-type UBQLN2. Fluorescence recovery after photobleaching (FRAP) analysis of UBQLN2 condensates revealed higher immobile fractions for UBQLN2 mutants, especially P506T. P497S and P497H mutations differentially impact condensate properties, demonstrating that the effects of ALS-linked mutations are both position- and amino acid-dependent. Collectively, our data show that disease mutations hinder assembly and alter viscoelastic properties of stress-induced UBQLN2 condensates, potentially leading to aggregates commonly observed in ALS.
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Affiliation(s)
- Julia F Riley
- Department of Biology, Syracuse University, Syracuse, NY, 13244, USA.,Department of Chemistry, Syracuse University, Syracuse, NY, 13244, USA.,Interdisciplinary Neuroscience Program, Syracuse University, Syracuse, NY, 13244, USA
| | | | - Amber K Rusnock
- Department of Biology, Syracuse University, Syracuse, NY, 13244, USA
| | - Heidi Hehnly
- Department of Biology, Syracuse University, Syracuse, NY, 13244, USA
| | - Carlos A Castañeda
- Department of Biology, Syracuse University, Syracuse, NY, 13244, USA.,Department of Chemistry, Syracuse University, Syracuse, NY, 13244, USA.,Interdisciplinary Neuroscience Program, Syracuse University, Syracuse, NY, 13244, USA
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24
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Zheng T, Galagedera SKK, Castañeda CA. Previously uncharacterized interactions between the folded and intrinsically disordered domains impart asymmetric effects on UBQLN2 phase separation. Protein Sci 2021; 30:1467-1481. [PMID: 34029402 DOI: 10.1002/pro.4128] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Revised: 05/20/2021] [Accepted: 05/21/2021] [Indexed: 02/06/2023]
Abstract
Shuttle protein UBQLN2 functions in protein quality control (PQC) by binding to proteasomal receptors and ubiquitinated substrates via its N-terminal ubiquitin-like (UBL) and C-terminal ubiquitin-associated (UBA) domains, respectively. Between these two folded domains are low-complexity STI1-I and STI1-II regions, connected by disordered linkers. The STI1 regions bind other components, such as HSP70, that are important to the PQC functions of UBQLN2. We recently determined that the STI1-II region enables UBQLN2 to undergo liquid-liquid phase separation (LLPS) to form liquid droplets in vitro and biomolecular condensates in cells. However, how the interplay between the folded (UBL/UBA) domains and the intrinsically disordered regions mediates phase separation is largely unknown. Using engineered domain deletion constructs, we found that removing the UBA domain inhibits UBQLN2 LLPS while removing the UBL domain enhances LLPS, suggesting that UBA and UBL domains contribute asymmetrically in modulating UBQLN2 LLPS. To explain these differential effects, we interrogated the interactions that involve the UBA and UBL domains across the entire UBQLN2 molecule using nuclear magnetic resonance spectroscopy. To our surprise, aside from well-studied canonical UBL:UBA interactions, there also exist moderate interactions between the UBL and several disordered regions, including STI1-I and residues 555-570, the latter of which is a known contributor to UBQLN2 LLPS. Our findings are essential for the understanding of both the molecular driving forces of UBQLN2 LLPS and the effects of ligand binding to UBL, UBA, or disordered regions on the phase behavior and physiological functions of UBQLN2.
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Affiliation(s)
- Tongyin Zheng
- Department of Chemistry, Syracuse University, Syracuse, New York, USA
| | | | - Carlos A Castañeda
- Departments of Biology and Chemistry, Syracuse University, Syracuse, New York, USA.,Interdisciplinary Neuroscience Program, Syracuse University, Syracuse, New York, USA.,BioInspired Institute, Syracuse University, Syracuse, New York, USA
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25
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Muley C, Kotschi S, Bartelt A. Role of Ubiquilins for Brown Adipocyte Proteostasis and Thermogenesis. Front Endocrinol (Lausanne) 2021; 12:739021. [PMID: 34650520 PMCID: PMC8505974 DOI: 10.3389/fendo.2021.739021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Accepted: 09/14/2021] [Indexed: 11/13/2022] Open
Abstract
The acclimatization of brown adipose tissue (BAT) to sustained cold exposure requires an adaptive increase in proteasomal protein quality control. Ubiquilins represent a recently identified family of shuttle proteins with versatile functions in protein degradation, such as facilitating substrate targeting and proteasomal degradation. However, whether ubiquilins participate in brown adipocyte function has not been investigated so far. Here, we determine the role of ubiquilins for proteostasis and non-shivering thermogenesis in brown adipocytes. We found that Ubqln1, 2 and 4 are highly expressed in BAT and their expression was induced by cold and proteasomal inhibition. Surprisingly, silencing of ubiquilin gene expression (one or multiple in combinations) did not lead to aggravated ER stress or inflammation. Moreover, ubiquitin level and proteasomal activity under basal conditions were not impacted by loss of ubiquilins. Also, non-shivering thermogenesis measured by norepinephrine-induced respiration remained intact after loss of ubiquilins. In conclusion, ubiquilin proteins are highly abundant in BAT and regulated by cold, but they are dispensable for brown adipocyte proteostasis and thermogenesis.
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Affiliation(s)
- Carolin Muley
- Institute for Cardiovascular Prevention (IPEK), Ludwig-Maximilians-University, Munich, Germany
| | - Stefan Kotschi
- Institute for Cardiovascular Prevention (IPEK), Ludwig-Maximilians-University, Munich, Germany
| | - Alexander Bartelt
- Institute for Cardiovascular Prevention (IPEK), Ludwig-Maximilians-University, Munich, Germany
- German Center for Cardiovascular Research, Partner Site Munich Heart Alliance, Technische Universität München, Munich, Germany
- Institute for Diabetes and Cancer (IDC), Helmholtz Center Munich, German Research Center for Environmental Health, Neuherberg, Germany
- Department of Molecular Metabolism & Sabri Ülker Center, Harvard T.H. Chan School of Public Health, Boston, MA, United States
- *Correspondence: Alexander Bartelt,
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26
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Johnston HE, Samant RS. Alternative systems for misfolded protein clearance: life beyond the proteasome. FEBS J 2020; 288:4464-4487. [PMID: 33135311 DOI: 10.1111/febs.15617] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Revised: 10/15/2020] [Accepted: 10/30/2020] [Indexed: 12/18/2022]
Abstract
Protein misfolding is a major driver of ageing-associated frailty and disease pathology. Although all cells possess multiple, well-characterised protein quality control systems to mitigate the toxicity of misfolded proteins, how they are integrated to maintain protein homeostasis ('proteostasis') in health-and how their disintegration contributes to disease-is still an exciting and fast-paced area of research. Under physiological conditions, the predominant route for misfolded protein clearance involves ubiquitylation and proteasome-mediated degradation. When the capacity of this route is overwhelmed-as happens during conditions of acute environmental stress, or chronic ageing-related decline-alternative routes for protein quality control are activated. In this review, we summarise our current understanding of how proteasome-targeted misfolded proteins are retrafficked to alternative protein quality control routes such as juxta-nuclear sequestration and selective autophagy when the ubiquitin-proteasome system is compromised. We also discuss the molecular determinants of these alternative protein quality control systems, attempt to clarify distinctions between various cytoplasmic spatial quality control inclusion bodies (e.g., Q-bodies, p62 bodies, JUNQ, aggresomes, and aggresome-like induced structures 'ALIS'), and speculate on emerging concepts in the field that we hope will spur future research-with the potential to benefit the rational development of healthy ageing strategies.
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Affiliation(s)
| | - Rahul S Samant
- Signalling Programme, The Babraham Institute, Cambridge, UK
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