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Thumbadoo KM, Dieriks BV, Murray HC, Swanson MEV, Yoo JH, Mehrabi NF, Turner C, Dragunow M, Faull RLM, Curtis MA, Siddique T, Shaw CE, Newell KL, Henden L, Williams KL, Nicholson GA, Scotter EL. Hippocampal aggregation signatures of pathogenic UBQLN2 in amyotrophic lateral sclerosis and frontotemporal dementia. Brain 2024; 147:3547-3561. [PMID: 38703371 PMCID: PMC11449146 DOI: 10.1093/brain/awae140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Revised: 03/03/2024] [Accepted: 03/07/2024] [Indexed: 05/06/2024] Open
Abstract
Pathogenic variants in the UBQLN2 gene cause X-linked dominant amyotrophic lateral sclerosis and/or frontotemporal dementia characterized by ubiquilin 2 aggregates in neurons of the motor cortex, hippocampus and spinal cord. However, ubiquilin 2 neuropathology is also seen in sporadic and familial amyotrophic lateral sclerosis and/or frontotemporal dementia cases not caused by UBQLN2 pathogenic variants, particularly C9orf72-linked cases. This makes the mechanistic role of mutant ubiquilin 2 protein and the value of ubiquilin 2 pathology for predicting genotype unclear. Here we examine a cohort of 44 genotypically diverse amyotrophic lateral sclerosis cases with or without frontotemporal dementia, including eight cases with UBQLN2 variants [resulting in p.S222G, p.P497H, p.P506S, p.T487I (two cases) and p.P497L (three cases)]. Using multiplexed (five-label) fluorescent immunohistochemistry, we mapped the co-localization of ubiquilin 2 with phosphorylated TDP-43, dipeptide repeat aggregates and p62 in the hippocampus of controls (n = 6), or amyotrophic lateral sclerosis with or without frontotemporal dementia in sporadic (n = 20), unknown familial (n = 3), SOD1-linked (n = 1), FUS-linked (n = 1), C9orf72-linked (n = 5) and UBQLN2-linked (n = 8) cases. We differentiate between (i) ubiquilin 2 aggregation together with phosphorylated TDP-43 or dipeptide repeat proteins; and (ii) ubiquilin 2 self-aggregation promoted by UBQLN2 pathogenic variants that cause amyotrophic lateral sclerosis and/or frontotemporal dementia. Overall, we describe a hippocampal protein aggregation signature that fully distinguishes mutant from wild-type ubiquilin 2 in amyotrophic lateral sclerosis with or without frontotemporal dementia, whereby mutant ubiquilin 2 is more prone than wild-type to aggregate independently of driving factors. This neuropathological signature can be used to assess the pathogenicity of UBQLN2 gene variants and to understand the mechanisms of UBQLN2-linked disease.
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Affiliation(s)
- Kyrah M Thumbadoo
- School of Biological Sciences, University of Auckland, Auckland 1010, New Zealand
- Centre for Brain Research, University of Auckland, Auckland 1010, New Zealand
| | - Birger V Dieriks
- Centre for Brain Research, University of Auckland, Auckland 1010, New Zealand
- Department of Anatomy and Medical Imaging, University of Auckland, Auckland 1010, New Zealand
| | - Helen C Murray
- Centre for Brain Research, University of Auckland, Auckland 1010, New Zealand
- Department of Anatomy and Medical Imaging, University of Auckland, Auckland 1010, New Zealand
| | - Molly E V Swanson
- School of Biological Sciences, University of Auckland, Auckland 1010, New Zealand
- Department of Anatomy and Medical Imaging, University of Auckland, Auckland 1010, New Zealand
| | - Ji Hun Yoo
- Centre for Brain Research, University of Auckland, Auckland 1010, New Zealand
- Department of Pharmacology and Clinical Pharmacology, University of Auckland, Auckland 1010, New Zealand
| | - Nasim F Mehrabi
- Centre for Brain Research, University of Auckland, Auckland 1010, New Zealand
- Department of Anatomy and Medical Imaging, University of Auckland, Auckland 1010, New Zealand
| | - Clinton Turner
- Centre for Brain Research, University of Auckland, Auckland 1010, New Zealand
- Department of Anatomy and Medical Imaging, University of Auckland, Auckland 1010, New Zealand
- Department of Anatomical Pathology, LabPlus, Auckland City Hospital, Auckland 1010, New Zealand
| | - Michael Dragunow
- Centre for Brain Research, University of Auckland, Auckland 1010, New Zealand
- Department of Pharmacology and Clinical Pharmacology, University of Auckland, Auckland 1010, New Zealand
| | - Richard L M Faull
- Centre for Brain Research, University of Auckland, Auckland 1010, New Zealand
- Department of Anatomy and Medical Imaging, University of Auckland, Auckland 1010, New Zealand
| | - Maurice A Curtis
- Centre for Brain Research, University of Auckland, Auckland 1010, New Zealand
- Department of Anatomy and Medical Imaging, University of Auckland, Auckland 1010, New Zealand
| | - Teepu Siddique
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
- Department of Cell and Developmental Biology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
- Department of Pathology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Christopher E Shaw
- Centre for Brain Research, University of Auckland, Auckland 1010, New Zealand
- UK Dementia Research Institute Centre, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London SE5 8AF, UK
| | - Kathy L Newell
- Department of Pathology and Laboratory Medicine, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Lyndal Henden
- Macquarie University Motor Neuron Disease Research Centre, Macquarie Medical School, Faculty of Medicine, Health and Human Sciences, Macquarie University, Sydney, New South Wales 2109, Australia
| | - Kelly L Williams
- Macquarie University Motor Neuron Disease Research Centre, Macquarie Medical School, Faculty of Medicine, Health and Human Sciences, Macquarie University, Sydney, New South Wales 2109, Australia
| | - Garth A Nicholson
- Macquarie University Motor Neuron Disease Research Centre, Macquarie Medical School, Faculty of Medicine, Health and Human Sciences, Macquarie University, Sydney, New South Wales 2109, Australia
- Northcott Neuroscience Laboratory, Australian and New Zealand Army Corps (ANZAC) Research Institute, Concord, New South Wales 2139, Australia
- Faculty of Medicine, University of Sydney, Sydney, New South Wales 2050, Australia
- Molecular Medicine Laboratory, Concord Repatriation General Hospital, Concord, New South Wales 2139, Australia
| | - Emma L Scotter
- School of Biological Sciences, University of Auckland, Auckland 1010, New Zealand
- Centre for Brain Research, University of Auckland, Auckland 1010, New Zealand
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2
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Adámik M, Soldánová Z, Drotárová M, Brečková K, Petr M, Helma R, Jenner LP, Vorlíčková M, Sýkorová E, Brázdová M. Human ARMC6 binds in vitro to both cancer genes and telomeric RNA, favoring G-quadruplex structure recognition. BIOCHIMICA ET BIOPHYSICA ACTA. GENE REGULATORY MECHANISMS 2024; 1867:195050. [PMID: 39029558 DOI: 10.1016/j.bbagrm.2024.195050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2024] [Revised: 06/25/2024] [Accepted: 07/13/2024] [Indexed: 07/21/2024]
Abstract
Armadillo repeat-containing proteins (ARMCs) are a large family found throughout eukaryotes, which play prominent roles in cell adhesion, signaling and cytoskeletal regulation. The ARMC6 protein is highly conserved in primates, including humans, but to date does not have a clear function beyond initial hints of a link to cancer and telomerase activity. We report here in vitro experiments showing ARMC6 binding to DNA promoter sequences from several cancer-related genes (e.g., EGFR, VEGF and c-MYC), and also to the telomeric RNA repeat (TERRA). ARMC6 binding activity appears to recognize G-quadruplex motifs, which are being increasingly implicated as structure-based protein binding sites in chromosome maintenance and repair. In vivo investigation of ARMC6 function revealed that when this protein is overexpressed in human cell lines, there is different expression of genes connected with oncogenic pathways and those implicated in downstream non-canonical telomerase pathways (e.g., VEGF, hTERT, c-MYC, ESM1, MMP3). ARMC6 is already known to interact with human shelterin protein TRF2 and telomerase. The protein binds G-quadruplex structures and does so preferentially to RNA over DNA. As such, this protein may be an example of how a non-canonical nucleic acid structural motif allows mediation between gene regulation and telomeric chromatin rearrangement pathways.
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Affiliation(s)
- Matej Adámik
- Institute of Biophysics, Academy of Sciences of the Czech Republic v.v.i., Královopolská 135, 612 00 Brno, Czech Republic
| | - Zuzana Soldánová
- Department of Molecular Pharmacy, Faculty of Pharmacy, Masaryk University, Palackého 1/3, 612 42 Brno, Czech Republic
| | - Magdaléna Drotárová
- Institute of Biophysics, Academy of Sciences of the Czech Republic v.v.i., Královopolská 135, 612 00 Brno, Czech Republic
| | - Katarína Brečková
- Department of Molecular Pharmacy, Faculty of Pharmacy, Masaryk University, Palackého 1/3, 612 42 Brno, Czech Republic
| | - Marek Petr
- Institute of Biophysics, Academy of Sciences of the Czech Republic v.v.i., Královopolská 135, 612 00 Brno, Czech Republic
| | - Robert Helma
- Institute of Biophysics, Academy of Sciences of the Czech Republic v.v.i., Královopolská 135, 612 00 Brno, Czech Republic
| | - Leon P Jenner
- Institute of Biophysics, Academy of Sciences of the Czech Republic v.v.i., Královopolská 135, 612 00 Brno, Czech Republic
| | - Michaela Vorlíčková
- Institute of Biophysics, Academy of Sciences of the Czech Republic v.v.i., Královopolská 135, 612 00 Brno, Czech Republic
| | - Eva Sýkorová
- Institute of Biophysics, Academy of Sciences of the Czech Republic v.v.i., Královopolská 135, 612 00 Brno, Czech Republic
| | - Marie Brázdová
- Institute of Biophysics, Academy of Sciences of the Czech Republic v.v.i., Královopolská 135, 612 00 Brno, Czech Republic; Department of Molecular Pharmacy, Faculty of Pharmacy, Masaryk University, Palackého 1/3, 612 42 Brno, Czech Republic.
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3
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Valentino IM, Llivicota-Guaman JG, Dao TP, Mulvey EO, Lehman AM, Galagedera SKK, Mallon EL, Castañeda CA, Kraut DA. Phase separation of polyubiquitinated proteins in UBQLN2 condensates controls substrate fate. Proc Natl Acad Sci U S A 2024; 121:e2405964121. [PMID: 39121161 PMCID: PMC11331126 DOI: 10.1073/pnas.2405964121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2024] [Accepted: 06/26/2024] [Indexed: 08/11/2024] Open
Abstract
Ubiquitination is one of the most common posttranslational modifications in eukaryotic cells. Depending on the architecture of polyubiquitin chains, substrate proteins can meet different cellular fates, but our understanding of how chain linkage controls protein fate remains limited. UBL-UBA shuttle proteins, such as UBQLN2, bind to ubiquitinated proteins and to the proteasome or other protein quality control machinery elements and play a role in substrate fate determination. Under physiological conditions, UBQLN2 forms biomolecular condensates through phase separation, a physicochemical phenomenon in which multivalent interactions drive the formation of a macromolecule-rich dense phase. Ubiquitin and polyubiquitin chains modulate UBQLN2's phase separation in a linkage-dependent manner, suggesting a possible link to substrate fate determination, but polyubiquitinated substrates have not been examined directly. Using sedimentation assays and microscopy we show that polyubiquitinated substrates induce UBQLN2 phase separation and incorporate into the resulting condensates. This substrate effect is strongest with K63-linked substrates, intermediate with mixed-linkage substrates, and weakest with K48-linked substrates. Proteasomes can be recruited to these condensates, but proteasome activity toward K63-linked and mixed linkage substrates is inhibited in condensates. Substrates are also protected from deubiquitinases by UBQLN2-induced phase separation. Our results suggest that phase separation could regulate the fate of ubiquitinated substrates in a chain-linkage-dependent manner, thus serving as an interpreter of the ubiquitin code.
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Affiliation(s)
| | | | - Thuy P Dao
- Department of Biology, Department of Chemistry, Bioinspired Institute, Interdisciplinary Neuroscience Program, Syracuse University, Syracuse, NY 13244
| | - Erin O Mulvey
- Department of Chemistry, Villanova University, Villanova, PA 19085
| | - Andrew M Lehman
- Department of Chemistry, Villanova University, Villanova, PA 19085
| | - Sarasi K K Galagedera
- Department of Biology, Department of Chemistry, Bioinspired Institute, Interdisciplinary Neuroscience Program, Syracuse University, Syracuse, NY 13244
| | - Erica L Mallon
- Department of Chemistry, Villanova University, Villanova, PA 19085
| | - Carlos A Castañeda
- Department of Biology, Department of Chemistry, Bioinspired Institute, Interdisciplinary Neuroscience Program, Syracuse University, Syracuse, NY 13244
| | - Daniel A Kraut
- Department of Chemistry, Villanova University, Villanova, PA 19085
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4
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Jacob SM, Lee S, Kim SH, Sharkey KA, Pfeffer G, Nguyen MD. Brain-body mechanisms contribute to sexual dimorphism in amyotrophic lateral sclerosis. Nat Rev Neurol 2024; 20:475-494. [PMID: 38965379 DOI: 10.1038/s41582-024-00991-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/07/2024] [Indexed: 07/06/2024]
Abstract
Amyotrophic lateral sclerosis (ALS) is the most common form of human motor neuron disease. It is characterized by the progressive degeneration of upper and lower motor neurons, leading to generalized motor weakness and, ultimately, respiratory paralysis and death within 3-5 years. The disease is shaped by genetics, age, sex and environmental stressors, but no cure or routine biomarkers exist for the disease. Male individuals have a higher propensity to develop ALS, and a different manifestation of the disease phenotype, than female individuals. However, the mechanisms underlying these sex differences remain a mystery. In this Review, we summarize the epidemiology of ALS, examine the sexually dimorphic presentation of the disease and highlight the genetic variants and molecular pathways that might contribute to sex differences in humans and animal models of ALS. We advance the idea that sexual dimorphism in ALS arises from the interactions between the CNS and peripheral organs, involving vascular, metabolic, endocrine, musculoskeletal and immune systems, which are strikingly different between male and female individuals. Finally, we review the response to treatments in ALS and discuss the potential to implement future personalized therapeutic strategies for the disease.
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Affiliation(s)
- Sarah M Jacob
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
- Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Sukyoung Lee
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
- Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
- Department of Cell Biology and Anatomy, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
- Department of Biochemistry and Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Seung Hyun Kim
- Department of Neurology, Hanyang University Hospital, Seoul, South Korea
| | - Keith A Sharkey
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
- Snyder Institute for Chronic Diseases, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Gerald Pfeffer
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
- Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
- Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
| | - Minh Dang Nguyen
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
- Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
- Department of Cell Biology and Anatomy, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
- Department of Biochemistry and Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
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5
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Valentino IM, Llivicota-Guaman JG, Dao TP, Mulvey EO, Lehman AM, Galagedera SKK, Mallon EL, Castañeda CA, Kraut DA. Phase separation of polyubiquitinated proteins in UBQLN2 condensates controls substrate fate. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.15.585243. [PMID: 38559018 PMCID: PMC10980000 DOI: 10.1101/2024.03.15.585243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Ubiquitination is one of the most common post-translational modifications in eukaryotic cells. Depending on the architecture of polyubiquitin chains, substrate proteins can meet different cellular fates, but our understanding of how chain linkage controls protein fate remains limited. UBL-UBA shuttle proteins, such as UBQLN2, bind to ubiquitinated proteins and to the proteasome or other protein quality control machinery elements and play a role in substrate fate determination. Under physiological conditions, UBQLN2 forms biomolecular condensates through phase separation, a physicochemical phenomenon in which multivalent interactions drive the formation of a macromolecule-rich dense phase. Ubiquitin and polyubiquitin chains modulate UBQLN2's phase separation in a linkage-dependent manner, suggesting a possible link to substrate fate determination, but polyubiquitinated substrates have not been examined directly. Using sedimentation assays and microscopy we show that polyubiquitinated substrates induce UBQLN2 phase separation and incorporate into the resulting condensates. This substrate effect is strongest with K63-linked substrates, intermediate with mixed-linkage substrates, and weakest with K48-linked substrates. Proteasomes can be recruited to these condensates, but proteasome activity towards K63-linked and mixed linkage substrates is inhibited in condensates. Substrates are also protected from deubiquitinases by UBQLN2-induced phase separation. Our results suggest that phase separation could regulate the fate of ubiquitinated substrates in a chain-linkage dependent manner, thus serving as an interpreter of the ubiquitin code.
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Affiliation(s)
| | | | - Thuy P. Dao
- Department of Biology, Department of Chemistry, Bioinspired Institute, Interdisciplinary Neuroscience Program, Syracuse University, Syracuse, NY 13244
| | - Erin O. Mulvey
- Department of Chemistry, Villanova University, Villanova, PA 19085
| | - Andrew M. Lehman
- Department of Chemistry, Villanova University, Villanova, PA 19085
| | - Sarasi K. K. Galagedera
- Department of Biology, Department of Chemistry, Bioinspired Institute, Interdisciplinary Neuroscience Program, Syracuse University, Syracuse, NY 13244
| | - Erica L. Mallon
- Department of Chemistry, Villanova University, Villanova, PA 19085
| | - Carlos A. Castañeda
- Department of Biology, Department of Chemistry, Bioinspired Institute, Interdisciplinary Neuroscience Program, Syracuse University, Syracuse, NY 13244
| | - Daniel A. Kraut
- Department of Chemistry, Villanova University, Villanova, PA 19085
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6
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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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7
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Kandel R, Jung J, Neal S. Proteotoxic stress and the ubiquitin proteasome system. Semin Cell Dev Biol 2024; 156:107-120. [PMID: 37734998 PMCID: PMC10807858 DOI: 10.1016/j.semcdb.2023.08.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Revised: 08/01/2023] [Accepted: 08/20/2023] [Indexed: 09/23/2023]
Abstract
The ubiquitin proteasome system maintains protein homeostasis by regulating the breakdown of misfolded proteins, thereby preventing misfolded protein aggregates. The efficient elimination is vital for preventing damage to the cell by misfolded proteins, known as proteotoxic stress. Proteotoxic stress can lead to the collapse of protein homeostasis and can alter the function of the ubiquitin proteasome system. Conversely, impairment of the ubiquitin proteasome system can also cause proteotoxic stress and disrupt protein homeostasis. This review examines two impacts of proteotoxic stress, 1) disruptions to ubiquitin homeostasis (ubiquitin stress) and 2) disruptions to proteasome homeostasis (proteasome stress). Here, we provide a mechanistic description of the relationship between proteotoxic stress and the ubiquitin proteasome system. This relationship is illustrated by findings from several protein misfolding diseases, mainly neurodegenerative diseases, as well as from basic biology discoveries from yeast to mammals. In addition, we explore the importance of the ubiquitin proteasome system in endoplasmic reticulum quality control, and how proteotoxic stress at this organelle is alleviated. Finally, we highlight how cells utilize the ubiquitin proteasome system to adapt to proteotoxic stress and how the ubiquitin proteasome system can be genetically and pharmacologically manipulated to maintain protein homeostasis.
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Affiliation(s)
- Rachel Kandel
- School of Biological Sciences, Department of Cell and Developmental Biology, University of California San Diego, La Jolla, CA 92093, United States
| | - Jasmine Jung
- School of Biological Sciences, Department of Cell and Developmental Biology, University of California San Diego, La Jolla, CA 92093, United States
| | - Sonya Neal
- School of Biological Sciences, Department of Cell and Developmental Biology, University of California San Diego, La Jolla, CA 92093, United States; Howard Hughes Medical Institute, Chevy Chase, MD, USA.
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8
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Safren N, Dao TP, Mohan HM, Huang C, Trotter B, Castañeda CA, Paulson H, Barmada S, Sharkey LM. Pathogenic mutations in UBQLN2 exhibit diverse aggregation propensity and neurotoxicity. Sci Rep 2024; 14:6049. [PMID: 38472280 PMCID: PMC10933299 DOI: 10.1038/s41598-024-55582-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Accepted: 02/26/2024] [Indexed: 03/14/2024] Open
Abstract
The ubiquitin-adaptor protein UBQLN2 promotes degradation of several aggregate-prone proteins implicated in neurodegenerative diseases. Missense UBQLN2 mutations also cause X-linked amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Previously we demonstrated that the liquid-like properties of UBQLN2 molecular assemblies are altered by a specific pathogenic mutation, P506T, and that the propensity of UBQLN2 to aggregate correlated with neurotoxicity. Here, we systematically assess the effects of multiple, spatially distinct ALS/FTD-linked missense mutations on UBQLN2 aggregation propensity, neurotoxicity, phase separation, and autophagic flux. In contrast to what we observed for the P506T mutation, no other tested pathogenic mutant exhibited a clear correlation between aggregation propensity and neurotoxicity. These results emphasize the unique nature of pathogenic UBQLN2 mutations and argue against a generalizable link between aggregation propensity and neurodegeneration in UBQLN2-linked ALS/FTD.
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Affiliation(s)
- 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.
| | - Thuy P Dao
- Departments of Biology and Chemistry, Syracuse University, Syracuse, NY, 13244, USA
| | - Harihar Milaganur Mohan
- Department of Neurology, University of Michigan, Ann Arbor, MI, 48109-2200, USA
- Cellular and Molecular Biology Program, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
| | - Camellia Huang
- Department of Neurology, University of Michigan, Ann Arbor, MI, 48109-2200, USA
| | - Bryce Trotter
- Department of Neurology, University of Michigan, Ann Arbor, MI, 48109-2200, USA
| | - Carlos A Castañeda
- Departments of Biology and Chemistry, Syracuse University, Syracuse, NY, 13244, USA
| | - Henry 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
| | - Sami Barmada
- 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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9
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Zheng H, Zhang H. More than a bystander: RNAs specify multifaceted behaviors of liquid-liquid phase-separated biomolecular condensates. Bioessays 2024; 46:e2300203. [PMID: 38175843 DOI: 10.1002/bies.202300203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Revised: 12/09/2023] [Accepted: 12/12/2023] [Indexed: 01/06/2024]
Abstract
Cells contain a myriad of membraneless ribonucleoprotein (RNP) condensates with distinct compositions of proteins and RNAs. RNP condensates participate in different cellular activities, including RNA storage, mRNA translation or decay, stress response, etc. RNP condensates are assembled via liquid-liquid phase separation (LLPS) driven by multivalent interactions. Transition of RNP condensates into bodies with abnormal material properties, such as solid-like amyloid structures, is associated with the pathogenesis of various diseases. In this review, we focus on how RNAs regulate multiple aspects of RNP condensates, such as dynamic assembly and/or disassembly and biophysical properties. RNA properties - including concentration, sequence, length and structure - also determine the phase behaviors of RNP condensates. RNA is also involved in specifying autophagic degradation of RNP condensates. Unraveling the role of RNA in RNPs provides novel insights into pathological accumulation of RNPs in various diseases. This new understanding can potentially be harnessed to develop therapeutic strategies.
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Affiliation(s)
- Hui Zheng
- National Laboratory of Biomacromolecules, New Cornerstone Science Laboratory, Institute of Biophysics, Chinese Academy of Sciences, Beijing, P.R. China
| | - Hong Zhang
- National Laboratory of Biomacromolecules, New Cornerstone Science Laboratory, Institute of Biophysics, Chinese Academy of Sciences, Beijing, P.R. China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, P.R. China
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10
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Wang Z, Zhang C, Fan C, Liu Y. Post-translational modifications in stress granule and their implications in neurodegenerative diseases. BIOCHIMICA ET BIOPHYSICA ACTA. GENE REGULATORY MECHANISMS 2023; 1866:194989. [PMID: 37751804 DOI: 10.1016/j.bbagrm.2023.194989] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2023] [Revised: 08/21/2023] [Accepted: 09/21/2023] [Indexed: 09/28/2023]
Abstract
Stress granules (SGs) arise as formations of mRNAs and proteins in response to translation initiation inhibition during stress. These dynamic compartments adopt a fluidic nature through liquid-liquid phase separation (LLPS), exhibiting a composition subject to constant change within cellular contexts. Research has unveiled an array of post-translational modifications (PTMs) occurring on SG proteins, intricately orchestrating SG dynamics. In the realm of neurodegenerative diseases, pathological mutant proteins congregate into insoluble aggregates alongside numerous SG proteins, manifesting resilience against disassembly. Specific PTMs conspicuously label these aggregates, designating them for subsequent degradation. The strategic manipulation of aberrant SGs via PTMs emerges as a promising avenue for therapeutic intervention. This review discerns recent strides in comprehending the impact of PTMs on LLPS behavior and the assembly/disassembly kinetics of SGs. By delving into the roles of PTMs in governing SG dynamics, we augment our cognizance of the molecular underpinnings of neurodegeneration. Furthermore, we offer invaluable insights into potential targets for therapeutic intervention in neurodegenerative afflictions, encompassing conditions like amyotrophic lateral sclerosis and frontotemporal dementia.
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Affiliation(s)
- Zhangshun Wang
- School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Chen'ang Zhang
- School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Chengyu Fan
- School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Yanfen Liu
- School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China.
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11
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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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12
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Liang P, Zhang J, Wang B. Emerging Roles of Ubiquitination in Biomolecular Condensates. Cells 2023; 12:2329. [PMID: 37759550 PMCID: PMC10527650 DOI: 10.3390/cells12182329] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2023] [Revised: 09/08/2023] [Accepted: 09/08/2023] [Indexed: 09/29/2023] Open
Abstract
Biomolecular condensates are dynamic non-membrane-bound macromolecular high-order assemblies that participate in a growing list of cellular processes, such as transcription, the cell cycle, etc. Disturbed dynamics of biomolecular condensates are associated with many diseases, including cancer and neurodegeneration. Extensive efforts have been devoted to uncovering the molecular and biochemical grammar governing the dynamics of biomolecular condensates and establishing the critical roles of protein posttranslational modifications (PTMs) in this process. Here, we summarize the regulatory roles of ubiquitination (a major form of cellular PTM) in the dynamics of biomolecular condensates. We propose that these regulatory mechanisms can be harnessed to combat many diseases.
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Affiliation(s)
- Peigang Liang
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiamen 361102, China; (P.L.); (J.Z.)
| | - Jiaqi Zhang
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiamen 361102, China; (P.L.); (J.Z.)
| | - Bo Wang
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiamen 361102, China; (P.L.); (J.Z.)
- Shenzhen Research Institute of Xiamen University, Shenzhen 518057, China
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13
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Ma Y, Farny NG. Connecting the dots: Neuronal senescence, stress granules, and neurodegeneration. Gene 2023; 871:147437. [PMID: 37084987 PMCID: PMC10205695 DOI: 10.1016/j.gene.2023.147437] [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: 02/03/2023] [Revised: 04/09/2023] [Accepted: 04/14/2023] [Indexed: 04/23/2023]
Abstract
Cellular senescence increases with aging. While senescence is associated with an exit of the cell cycle, there is ample evidence that post-mitotic cells including neurons can undergo senescence as the brain ages, and that senescence likely contributes significantly to the progression of neurodegenerative diseases (ND) such as Alzheimer's Disease (AD) and Amyotrophic Lateral Sclerosis (ALS). Stress granules (SGs) are stress-induced cytoplasmic biomolecular condensates of RNA and proteins, which have been linked to the development of AD and ALS. The SG seeding hypothesis of NDs proposes that chronic stress in aging neurons results in static SGs that progress into pathological aggregates Alterations in SG dynamics have also been linked to senescence, though studies that link SGs and senescence in the context of NDs and the aging brain have not yet been performed. In this Review, we summarize the literature on senescence, and explore the contribution of senescence to the aging brain. We describe senescence phenotypes in aging neurons and glia, and their links to neuroinflammation and the development of AD and ALS. We further examine the relationships of SGs to senescence and to ND. We propose a new hypothesis that neuronal senescence may contribute to the mechanism of SG seeding in ND by altering SG dynamics in aged cells, thereby providing additional aggregation opportunities within aged neurons.
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Affiliation(s)
- Yizhe Ma
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, MA, USA
| | - Natalie G Farny
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, MA, USA.
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14
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Li Y, Xu M, Qi Z. Deciphering molecular mechanisms of phase separation in RNA biology by single-molecule biophysical technologies. Acta Biochim Biophys Sin (Shanghai) 2023; 55:1034-1041. [PMID: 37337634 PMCID: PMC10415185 DOI: 10.3724/abbs.2023113] [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: 12/31/2022] [Accepted: 03/06/2023] [Indexed: 06/21/2023] Open
Abstract
Ribonucleic acid (RNA) biology has emerged as one of the most important areas in modern biology and biomedicine. RNA and RNA-binding proteins (RBPs) are involved in forming biomolecular condensates, which are crucial for RNA metabolism. To quantitively decipher the molecular mechanisms of RNP granules, researchers have turned to single-molecule biophysical techniques, such as single-molecule Förster resonance energy transfer (smFRET), in vivo single-molecule imaging technique with single particle tracking (SPT), DNA Curtains, optical tweezers, and atomic force microscopy (AFM). These methods are used to investigate the molecular biophysical properties within RNP granules, as well as the molecular interactions between RNA and RBPs and RBPs themselves, which are challenging to study using traditional experimental methods of the liquid-liquid phase separation (LLPS) field, such as fluorescence recovery after photobleaching (FRAP). In this work, we summarize the applications of single-molecule biophysical techniques in RNP granule studies and highlight how these methods can be used to reveal the molecular mechanisms of RNP granules.
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Affiliation(s)
- Yuchen Li
- Center for Quantitative Biology and Peking-Tsinghua Center for Life SciencesAcademy for Advanced Interdisciplinary StudiesPeking UniversityBeijing100871China
| | - Mengmeng Xu
- Tsinghua-Peking Center for Life SciencesTsinghua UniversityBeijing100084China
| | - Zhi Qi
- Center for Quantitative Biology and Peking-Tsinghua Center for Life SciencesAcademy for Advanced Interdisciplinary StudiesPeking UniversityBeijing100871China
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15
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Zheng H, Peng K, Gou X, Ju C, Zhang H. RNA recruitment switches the fate of protein condensates from autophagic degradation to accumulation. J Cell Biol 2023; 222:e202210104. [PMID: 37014300 PMCID: PMC10075224 DOI: 10.1083/jcb.202210104] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Revised: 02/07/2023] [Accepted: 03/01/2023] [Indexed: 04/05/2023] Open
Abstract
Protein condensates can evade autophagic degradation under stress or pathological conditions. However, the underlying mechanisms are unclear. Here, we demonstrate that RNAs switch the fate of condensates in Caenorhabditis elegans. PGL granules undergo autophagic degradation in embryos laid under normal conditions and accumulate in embryos laid under heat stress conditions to confer stress adaptation. In heat-stressed embryos, mRNAs and RNA control factors partition into PGL granules. Depleting proteins involved in mRNA biogenesis and stability suppresses PGL granule accumulation and triggers their autophagic degradation, while loss of activity of proteins involved in RNA turnover facilitates accumulation. RNAs facilitate LLPS of PGL granules, enhance their liquidity, and also inhibit recruitment of the gelation-promoting scaffold protein EPG-2 to PGL granules. Thus, RNAs are important for controlling the susceptibility of phase-separated protein condensates to autophagic degradation. Our work provides insights into the accumulation of ribonucleoprotein aggregates associated with the pathogenesis of various diseases.
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Affiliation(s)
- Hui Zheng
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Kangfu Peng
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Xiaomeng Gou
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Chen Ju
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Hong Zhang
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
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16
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Buel GR, Chen X, Myint W, Kayode O, Folimonova V, Cruz A, Skorupka KA, Matsuo H, Walters KJ. E6AP AZUL interaction with UBQLN1/2 in cells, condensates, and an AlphaFold-NMR integrated structure. Structure 2023; 31:395-410.e6. [PMID: 36827983 PMCID: PMC10081965 DOI: 10.1016/j.str.2023.01.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 01/13/2023] [Accepted: 01/30/2023] [Indexed: 02/25/2023]
Abstract
The E3 ligase E6AP/UBE3A has a dedicated binding site in the 26S proteasome provided by the RAZUL domain of substrate receptor hRpn10/S5a/PSMD4. Guided by RAZUL sequence similarity, we test and demonstrate here that the E6AP AZUL binds transiently to the UBA of proteasomal shuttle factor UBQLN1/2. Despite a weak binding affinity, E6AP AZUL is recruited to UBQLN2 biomolecular condensates in vitro and E6AP interacts with UBQLN1/2 in cellulo. Steady-state and transfer nuclear Overhauser effect (NOE) experiments indicate direct interaction of AZUL with UBQLN1 UBA. Intermolecular contacts identified by NOE spectroscopy (NOESY) data were combined with AlphaFold2-Multimer predictions to yield an AZUL:UBA model structure. We additionally identify an oligomerization domain directly adjacent to UBQLN1/2 UBA (UBA adjacent [UBAA]) that is α-helical and allosterically reconfigured by AZUL binding to UBA. These data lead to a model of E6AP recruitment to UBQLN1/2 by AZUL:UBA interaction and provide fundamental information on binding requirements for interactions in condensates and cells.
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Affiliation(s)
- Gwen R Buel
- Protein Processing Section, Center for Structural Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Frederick, MD 21702, USA
| | - Xiang Chen
- Protein Processing Section, Center for Structural Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Frederick, MD 21702, USA
| | - Wazo Myint
- Cancer Innovation Laboratory, Frederick National Laboratory for Cancer Research, Frederick, MD 21702, USA
| | - Olumide Kayode
- Protein Processing Section, Center for Structural Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Frederick, MD 21702, USA
| | - Varvara Folimonova
- Protein Processing Section, Center for Structural Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Frederick, MD 21702, USA
| | - Anthony Cruz
- Protein Processing Section, Center for Structural Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Frederick, MD 21702, USA
| | - Katarzyna A Skorupka
- Cancer Innovation Laboratory, Frederick National Laboratory for Cancer Research, Frederick, MD 21702, USA
| | - Hiroshi Matsuo
- Cancer Innovation Laboratory, Frederick National Laboratory for Cancer Research, Frederick, MD 21702, USA
| | - Kylie J Walters
- Protein Processing Section, Center for Structural Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Frederick, MD 21702, USA.
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17
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Ji J, Wang W, Chen C. Single-molecule techniques to visualize and to characterize liquid-liquid phase separation and phase transition. Acta Biochim Biophys Sin (Shanghai) 2023; 55:1023-1033. [PMID: 36876423 PMCID: PMC10415186 DOI: 10.3724/abbs.2023028] [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: 11/24/2022] [Accepted: 01/09/2023] [Indexed: 02/23/2023] Open
Abstract
Biomolecules forming membraneless structures via liquid-liquid phase separation (LLPS) is a common event in living cells. Some liquid-like condensates can convert into solid-like aggregations, and such a phase transition process is related to some neurodegenerative diseases. Liquid-like condensates and solid-like aggregations usually exhibit distinctive fluidity and are commonly distinguished via their morphology and dynamic properties identified through ensemble methods. Emerging single-molecule techniques are a group of highly sensitive techniques, which can offer further mechanistic insights into LLPS and phase transition at the molecular level. Here, we summarize the working principles of several commonly used single-molecule techniques and demonstrate their unique power in manipulating LLPS, examining mechanical properties at the nanoscale, and monitoring dynamic and thermodynamic properties at the molecular level. Thus, single-molecule techniques are unique tools to characterize LLPS and liquid-to-solid phase transition under close-to-physiological conditions.
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Affiliation(s)
- Jinyao Ji
- School of Life SciencesBeijing Advanced Innovation Center for Structural BiologyBeijing Frontier Research Center of Biological StructureTsinghua UniversityBeijing100084China
| | - Wenjuan Wang
- School of Life SciencesTechnology Center for Protein SciencesTsinghua UniversityBeijing100084China
| | - Chunlai Chen
- School of Life SciencesBeijing Advanced Innovation Center for Structural BiologyBeijing Frontier Research Center of Biological StructureTsinghua UniversityBeijing100084China
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18
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Alessenko AV, Gutner UA, Shupik MA. Involvement of Lipids in the Pathogenesis of Amyotrophic Lateral Sclerosis. Life (Basel) 2023; 13:life13020510. [PMID: 36836867 PMCID: PMC9966871 DOI: 10.3390/life13020510] [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: 12/06/2022] [Revised: 01/26/2023] [Accepted: 02/10/2023] [Indexed: 02/15/2023] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by the progressive degeneration of upper and lower motor neurons. To study its underlying mechanisms, a variety of models are currently used at the cellular level and in animals with mutations in multiple ALS associated genes, including SOD1, C9ORF72, TDP-43, and FUS. Key mechanisms involved in the disease include excitotoxicity, oxidative stress, mitochondrial dysfunction, neuroinflammatory, and immune reactions. In addition, significant metabolism alterations of various lipids classes, including phospholipids, fatty acids, sphingolipids, and others have been increasingly recognized. Recently, the mechanisms of programmed cell death (apoptosis), which may be responsible for the degeneration of motor neurons observed in the disease, have been intensively studied. In this context, sphingolipids, which are the most important sources of secondary messengers transmitting signals for cell proliferation, differentiation, and apoptosis, are gaining increasing attention in the context of ALS pathogenesis given their role in the development of neuroinflammatory and immune responses. This review describes changes in lipids content and activity of enzymes involved in their metabolism in ALS, both summarizing current evidence from animal models and clinical studies and discussing the potential of new drugs among modulators of lipid metabolism enzymes.
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19
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Phung TH, Tatman M, Monteiro MJ. UBQLN2 undergoes a reversible temperature-induced conformational switch that regulates binding with HSPA1B: ALS/FTD mutations cripple the switch but do not destroy HSPA1B binding. Biochim Biophys Acta Gen Subj 2023; 1867:130284. [PMID: 36423739 PMCID: PMC9792439 DOI: 10.1016/j.bbagen.2022.130284] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Revised: 10/23/2022] [Accepted: 11/18/2022] [Indexed: 11/23/2022]
Abstract
Here we present evidence, based on alterations of its intrinsic tryptophan fluorescence, that UBQLN2 protein undergoes a conformational switch when the temperature is raised from 37 °C to 42 °C. The switch is reset on restoration of the temperature. We speculate that the switch regulates UBQLN2 function in the heat shock response because elevation of the temperature from 37 °C to 42 °C dramatically increased in vitro binding between UBQLN2 and HSPA1B. Furthermore, restoration of the temperature to 37 °C decreased HSPA1B binding. By comparison to wild type (WT) UBQLN2, we found that all five ALS/FTD mutant UBQLN2 proteins we examined had attenuated alterations in tryptophan fluorescence when shifted to 42 °C, suggesting that the conformational switch is crippled in the mutants. Paradoxically, all five mutants bound similar amounts of HSPA1B compared to WT UBQLN2 protein at 42 °C, suggesting that either the conformational switch is not instrumental for HSPA1B binding, or that, although damaged, it is still functional. Comparison of the poly-ubiquitin chain binding revealed that WT UBQLN2 binds more avidly with K63 than with K48 chains. The avidity may explain the involvement of UBQLN2 in autophagy and cell signaling. Consistent with its function in autophagy, we found UBQLN2 binds directly with LC3, the autophagosomal-specific membrane-tethered protein. Finally, we provide evidence that WT UBQLN2 can homodimerize, and heterodimerize with WT UBQLN1. We show that ALS mutant P497S-UBQLN2 protein can oligomerize with either WT UBQLN1 or 2, providing a possible mechanism for how mutant UBQLN2 proteins could bind and inactivate UBQLN proteins, causing loss of function.
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Affiliation(s)
- 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
| | - Micaela Tatman
- 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
- 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.
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20
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Millar SR, Huang JQ, Schreiber KJ, Tsai YC, Won J, Zhang J, Moses AM, Youn JY. A New Phase of Networking: The Molecular Composition and Regulatory Dynamics of Mammalian Stress Granules. Chem Rev 2023. [PMID: 36662637 PMCID: PMC10375481 DOI: 10.1021/acs.chemrev.2c00608] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Stress granules (SGs) are cytosolic biomolecular condensates that form in response to cellular stress. Weak, multivalent interactions between their protein and RNA constituents drive their rapid, dynamic assembly through phase separation coupled to percolation. Though a consensus model of SG function has yet to be determined, their perceived implication in cytoprotective processes (e.g., antiviral responses and inhibition of apoptosis) and possible role in the pathogenesis of various neurodegenerative diseases (e.g., amyotrophic lateral sclerosis and frontotemporal dementia) have drawn great interest. Consequently, new studies using numerous cell biological, genetic, and proteomic methods have been performed to unravel the mechanisms underlying SG formation, organization, and function and, with them, a more clearly defined SG proteome. Here, we provide a consensus SG proteome through literature curation and an update of the user-friendly database RNAgranuleDB to version 2.0 (http://rnagranuledb.lunenfeld.ca/). With this updated SG proteome, we use next-generation phase separation prediction tools to assess the predisposition of SG proteins for phase separation and aggregation. Next, we analyze the primary sequence features of intrinsically disordered regions (IDRs) within SG-resident proteins. Finally, we review the protein- and RNA-level determinants, including post-translational modifications (PTMs), that regulate SG composition and assembly/disassembly dynamics.
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Affiliation(s)
- Sean R Millar
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Jie Qi Huang
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Karl J Schreiber
- Program in Molecular Medicine, The Hospital for Sick Children, Toronto, Ontario M5G 0A4, Canada
| | - Yi-Cheng Tsai
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Jiyun Won
- Department of Cell & Systems Biology, University of Toronto, Toronto, Ontario M5S 3B2, Canada
| | - Jianping Zhang
- Lunenfeld-Tanenbaum Research Institute, Sinai Health System, Toronto, Ontario M5G 1X5, Canada
| | - Alan M Moses
- Department of Cell & Systems Biology, University of Toronto, Toronto, Ontario M5S 3B2, Canada.,Department of Computer Science, University of Toronto, Toronto, Ontario M5T 3A1, Canada.,The Centre for the Analysis of Genome Evolution and Function, University of Toronto, Toronto, Ontario M5S 3B2, Canada
| | - Ji-Young Youn
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario M5S 1A8, Canada.,Program in Molecular Medicine, The Hospital for Sick Children, Toronto, Ontario M5G 0A4, Canada
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21
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Silencing UBQLN2 Enhances the Radiosensitivity of Esophageal Squamous Cell Carcinoma (ESCC) via Activating p38 MAPK. JOURNAL OF ONCOLOGY 2023; 2023:2339732. [PMID: 36644234 PMCID: PMC9836790 DOI: 10.1155/2023/2339732] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/02/2022] [Revised: 12/23/2022] [Accepted: 12/26/2022] [Indexed: 01/07/2023]
Abstract
Background Ubiquilin 2 (UBQLN2) is an adaptor of ubiquitinated proteins and the proteasome. The potential role of UBQLN2 in carcinogenesis has been demonstrated. However, its role in modulating the radiosensitivity of cancer is not clear. Here, we explored the radiosensitizing effect of silencing UBQLN2 on esophageal squamous cell carcinoma (ESCC) and its mechanisms. Methods We analyzed the prognostic role of UBQLN2 in the ESCC patient cohort from the Cancer Genomic Atlas (TCGA) database and our hospital. We also conducted a series of experiments in vivo and in vitro to investigate the effect of silencing UBQLN2 on ESCC radiosensitivity and its mechanisms. Results UBQLN2 is highly expressed in ESCC tissues and positively correlated with poor overall survival (OS). The knockdown of UBQLN2 dramatically increased the radiosensitivity of ESCC cells. Mechanically, UBQLN2 suppression substantially upregulated p38 mitogen-activated protein kinases (MAPK). The p38 MAPK inhibitor SB203580 could reverse the radiation-enhancing effect induced by UBQLN2 knockdown. The direct interaction between UBQLN2 and p38 MAPK was confirmed by co-immunoprecipitation (CO-IP) assay. Furthermore, silencing UBQLN2 also inhibited the expression of phosphorylated DNA-dependent protein kinase catalytic subunit (p-DNA-PKcs) after irradiation. Finally, the xenografted tumor experiment confirmed the radiosensitizing effect of silencing UBQLN2 on ESCC in vivo. Conclusion Our results suggest that silencing UBQLN2 enhances the radiosensitivity of ESCC by activating p38 MAPK, and UBQLN2 may be a potential target to enhance the radiosensitivity of ESCC.
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22
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Alexander EJ, Wang J. An Optimized Stress Granule Detection Method: Investigation of UBQLN2 Effect on Stress Granule Formation. Methods Mol Biol 2023; 2551:543-560. [PMID: 36310224 DOI: 10.1007/978-1-0716-2597-2_33] [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] [Indexed: 06/16/2023]
Abstract
Stress granules (SGs) are cytosolic ribonucleoprotein granules that form via a liquid-liquid phase separation in response to environmental stresses such as heat, oxidative, and osmotic changes. Due to the condensation of low complexity, hydrophobic regions in core SG components in these highly dynamic granules, defects in SG maintenance and formation have been linked to toxic aggregate formation in neurodegenerative diseases such as amyotrophic lateral sclerosis and frontotemporal dementia. However, efforts to dissect mechanisms regulating SG formation and maintenance have been limited by methods of tracking protein-SG localization. Here we describe a method for detecting and quantifying recruitment of cytosolically enriched proteins to SGs by indirect immunofluorescence microscopy. Using this method, we tracked the transient recruitment of the cytosolically enriched ubiquitin-like protein, ubiquilin 2 (UBQLN2), and a number of other factors into SGs, demonstrating its utility (Alexander et al., Proc Natl Acad Sci U S A 115:E11485-E11494, 2018).
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Affiliation(s)
- Elizabeth J Alexander
- Department of Biochemistry and Molecular Biology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD, USA
- Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Jiou Wang
- Department of Biochemistry and Molecular Biology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD, USA.
- Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
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23
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Safren N, Sharkey LM, Barmada SJ. Neuronal Puncta/Aggregate Formation by WT and Mutant UBQLN2. Methods Mol Biol 2023; 2551:561-573. [PMID: 36310225 PMCID: PMC10519613 DOI: 10.1007/978-1-0716-2597-2_34] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Protein aggregates are a common feature of nearly all neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis (ALS). Here we describe a method to quickly and accurately measure protein aggregation in cells expressing a fluorescently tagged aggregation-prone protein. This unbiased method obviates the need for manual scoring and facilitates the identification of factors governing protein self-assembly and its downstream consequences for cell heath.
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Affiliation(s)
- Nathaniel Safren
- Department of Neurology, University of Michigan Health System, Ann Arbor, MI, USA
| | - Lisa M Sharkey
- Department of Neurology, University of Michigan Health System, Ann Arbor, MI, USA
| | - Sami J Barmada
- Department of Neurology, University of Michigan Health System, Ann Arbor, MI, USA.
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24
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Kumar R, Malik Z, Singh M, Rachana R, Mani S, Ponnusamy K, Haider S. Amyotrophic Lateral Sclerosis Risk Genes and Suppressor. Curr Gene Ther 2023; 23:148-162. [PMID: 36366843 DOI: 10.2174/1566523223666221108113330] [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: 04/11/2022] [Revised: 08/24/2022] [Accepted: 09/01/2022] [Indexed: 11/12/2022]
Abstract
Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that leads to death by progressive paralysis and respiratory failure within 2-4 years of onset. About 90-95% of ALS cases are sporadic (sALS), and 5-10% are inherited through family (fALS). Though the mechanisms of the disease are still poorly understood, so far, approximately 40 genes have been reported as ALS causative genes. The mutations in some crucial genes, like SOD1, C9ORF72, FUS, and TDP-43, are majorly associated with ALS, resulting in ROS-associated oxidative stress, excitotoxicity, protein aggregation, altered RNA processing, axonal and vesicular trafficking dysregulation, and mitochondrial dysfunction. Recent studies show that dysfunctional cellular pathways get restored as a result of the repair of a single pathway in ALS. In this review article, our aim is to identify putative targets for therapeutic development and the importance of a single suppressor to reduce multiple symptoms by focusing on important mutations and the phenotypic suppressors of dysfunctional cellular pathways in crucial genes as reported by other studies.
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Affiliation(s)
- Rupesh Kumar
- Department of Biotechnology, Jaypee Institute of Information Technology, Sec-62, Noida, Uttar Pradesh, India
| | - Zubbair Malik
- School of Computational and Integrative Science, Jawaharlal Nehru University, New Delhi-110067, India
| | - Manisha Singh
- Department of Biotechnology, Jaypee Institute of Information Technology, Sec-62, Noida, Uttar Pradesh, India
| | - R Rachana
- Department of Biotechnology, Jaypee Institute of Information Technology, Sec-62, Noida, Uttar Pradesh, India
| | - Shalini Mani
- Department of Biotechnology, Jaypee Institute of Information Technology, Sec-62, Noida, Uttar Pradesh, India
| | | | - Shazia Haider
- Department of Biotechnology, Jaypee Institute of Information Technology, Sec-62, Noida, Uttar Pradesh, India
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25
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Assoni AF, Foijer F, Zatz M. Amyotrophic Lateral Sclerosis, FUS and Protein Synthesis Defects. Stem Cell Rev Rep 2022; 19:625-638. [PMID: 36515764 DOI: 10.1007/s12015-022-10489-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Revised: 12/06/2022] [Accepted: 12/06/2022] [Indexed: 12/15/2022]
Abstract
Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease that mainly affects the motor system. It is a very heterogeneous disorder, so far more than 40 genes have been described as responsible for ALS. The cause of motor neuron degeneration is not yet fully understood, but there is consensus in the literature that it is the result of a complex interplay of several pathogenic processes, which include alterations in nucleocytoplasmic transport, defects in transcription and splicing, altered formation and/or disassembly of stress granules and impaired proteostasis. These defects result in protein aggregation, impaired DNA repair, mitochondrial dysfunction and oxidative stress, neuroinflammation, impaired axonal transport, impaired vesicular transport, excitotoxicity, as well as impaired calcium influx. We argue here that all the above functions ultimately lead to defects in protein synthesis. Fused in Sarcoma (FUS) is one of the genes associated with ALS. It causes ALS type 6 when mutated and is found mislocalized to the cytoplasm in the motor neurons of sporadic ALS patients (without FUS mutations). In addition, FUS plays a role in all cellular functions that are impaired in degenerating motor neurons. Moreover, ALS patients with FUS mutations present the first symptoms significantly earlier than in other forms of the disease. Therefore, the aim of this review is to further discuss ALS6, detail the cellular functions of FUS, and suggest that the localization of FUS, as well as protein synthesis rates, could be hallmarks of the ALS phenotype and thus good therapeutic targets.
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Affiliation(s)
- Amanda Faria Assoni
- Human Genome and Stem Cell Research Center, Institute of Biosciences, University of São Paulo, 055080-090, CidadeUniversitária, São Paulo, Brazil.,European Research Institute for the Biology of Ageing, University of Groningen, 9713 AV, Groningen, The Netherlands
| | - Floris Foijer
- European Research Institute for the Biology of Ageing, University of Groningen, 9713 AV, Groningen, The Netherlands
| | - Mayana Zatz
- Human Genome and Stem Cell Research Center, Institute of Biosciences, University of São Paulo, 055080-090, CidadeUniversitária, São Paulo, Brazil.
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26
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Hu HY, Liu YJ. Sequestration of cellular native factors by biomolecular assemblies: Physiological or pathological? BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2022; 1869:119360. [PMID: 36087810 DOI: 10.1016/j.bbamcr.2022.119360] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Revised: 09/01/2022] [Accepted: 09/02/2022] [Indexed: 06/15/2023]
Abstract
In addition to native-state structures, biomolecules often form condensed supramolecular assemblies or cellular membraneless organelles that are critical for cell life. These biomolecular assemblies, generally including liquid-like droplets (condensates) and amyloid-like aggregates, can sequester or recruit their interacting partners, so as to either modulate various cellular behaviors or even cause disorders. This review article summarizes recent advances in the sequestration of native factors by biomolecular assemblies and discusses their potential consequences on cellular function, homeostasis, and disease pathology.
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Affiliation(s)
- Hong-Yu Hu
- State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai 200031, PR China.
| | - Ya-Jun Liu
- State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai 200031, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China
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27
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Espinoza MF, Nguyen KK, Sycks MM, Lyu Z, Quanrud GM, Montoya MR, Genereux JC. Heat shock protein Hspa13 regulates endoplasmic reticulum and cytosolic proteostasis through modulation of protein translocation. J Biol Chem 2022; 298:102597. [PMID: 36244454 PMCID: PMC9691929 DOI: 10.1016/j.jbc.2022.102597] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Revised: 09/29/2022] [Accepted: 10/03/2022] [Indexed: 11/06/2022] Open
Abstract
Most eukaryotic secretory proteins are cotranslationally translocated through Sec61 into the endoplasmic reticulum (ER). Because these proteins have evolved to fold in the ER, their mistargeting is associated with toxicity. Genetic experiments have implicated the ER heat shock protein 70 (Hsp70) Hspa13/STCH as involved in processing of nascent secretory proteins. Herein, we evaluate the role of Hspa13 in protein import and the maintenance of cellular proteostasis in human cells, primarily using the human embryonic kidney 293T cell line. We find that Hspa13 interacts primarily with the Sec61 translocon and its associated factors. Hspa13 overexpression inhibits translocation of the secreted protein transthyretin, leading to accumulation and aggregation of immature transthyretin in the cytosol. ATPase-inactive mutants of Hspa13 further inhibit translocation and maturation of secretory proteins. While Hspa13 overexpression inhibits cell growth and ER quality control, we demonstrate that HSPA13 knockout destabilizes proteostasis and increases sensitivity to ER disruption. Thus, we propose that Hspa13 regulates import through the translocon to maintain both ER and cytosolic protein homeostasis. The raw mass spectrometry data associated with this article have been deposited in the PRIDE archive and can be accessed at PXD033498.
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Affiliation(s)
- Mateo F Espinoza
- Graduate Program in Microbiology, University of California, Riverside, California, USA
| | - Khanh K Nguyen
- Department of Chemistry, University of California, Riverside, California, USA
| | - Melody M Sycks
- Department of Chemistry, University of California, Riverside, California, USA
| | - Ziqi Lyu
- Department of Chemistry, University of California, Riverside, California, USA
| | - Guy M Quanrud
- Department of Chemistry, University of California, Riverside, California, USA
| | - Maureen R Montoya
- Department of Chemistry, University of California, Riverside, California, USA
| | - Joseph C Genereux
- Graduate Program in Microbiology, University of California, Riverside, California, USA; Department of Chemistry, University of California, Riverside, California, USA.
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28
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Strohm L, Hu Z, Suk Y, Rühmkorf A, Sternburg E, Gattringer V, Riemenschneider H, Berutti R, Graf E, Weishaupt JH, Brill MS, Harbauer AB, Dormann D, Dengjel J, Edbauer D, Behrends C. Multi-omics profiling identifies a deregulated FUS-MAP1B axis in ALS/FTD-associated UBQLN2 mutants. Life Sci Alliance 2022; 5:5/11/e202101327. [PMID: 35777956 PMCID: PMC9258132 DOI: 10.26508/lsa.202101327] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 06/10/2022] [Accepted: 06/14/2022] [Indexed: 11/24/2022] Open
Abstract
Analysis of ALS patient-derived and engineered cells revealed that mutant UBQLN2 increases mRNA and protein of MAP1B which is mediated by dephosphorylation of FUS within its RNA-binding domain. Ubiquilin-2 (UBQLN2) is a ubiquitin-binding protein that shuttles ubiquitinated proteins to proteasomal and autophagic degradation. UBQLN2 mutations are genetically linked to the neurodegenerative disorders amyotrophic lateral sclerosis and frontotemporal dementia (ALS/FTD). However, it remains elusive how UBQLN2 mutations cause ALS/FTD. Here, we systematically examined proteomic and transcriptomic changes in patient-derived lymphoblasts and CRISPR/Cas9–engineered HeLa cells carrying ALS/FTD UBQLN2 mutations. This analysis revealed a strong up-regulation of the microtubule-associated protein 1B (MAP1B) which was also observed in UBQLN2 knockout cells and primary rodent neurons depleted of UBQLN2, suggesting that a UBQLN2 loss-of-function mechanism is responsible for the elevated MAP1B levels. Consistent with MAP1B’s role in microtubule binding, we detected an increase in total and acetylated tubulin. Furthermore, we uncovered that UBQLN2 mutations result in decreased phosphorylation of MAP1B and of the ALS/FTD–linked fused in sarcoma (FUS) protein at S439 which is critical for regulating FUS-RNA binding and MAP1B protein abundance. Together, our findings point to a deregulated UBQLN2-FUS-MAP1B axis that may link protein homeostasis, RNA metabolism, and cytoskeleton dynamics, three molecular pathomechanisms of ALS/FTD.
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Affiliation(s)
- Laura Strohm
- Munich Cluster for Systems Neurology, Medical Faculty, Ludwig-Maximilians-University München, Munich, Germany
| | - Zehan Hu
- Department of Biology, University of Fribourg, Fribourg, Switzerland
| | - Yongwon Suk
- Institute for Molecular Physiology, Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Alina Rühmkorf
- Max Planck Institute of Neurobiology, Martinsried, Germany
| | - Erin Sternburg
- Institute for Molecular Physiology, Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Vanessa Gattringer
- Munich Cluster for Systems Neurology, Medical Faculty, Ludwig-Maximilians-University München, Munich, Germany
| | - Henrick Riemenschneider
- Munich Cluster for Systems Neurology, Medical Faculty, Ludwig-Maximilians-University München, Munich, Germany.,German Center for Neurodegenerative Diseases Munich, Munich, Germany
| | - Riccardo Berutti
- Institute of Human Genetics, Helmholtz Zentrum München, Neuherberg, Germany
| | - Elisabeth Graf
- Institut für Humangenetik, Klinikum Rechts der Isar der Technischen Universität München, Munich, Germany
| | - Jochen H Weishaupt
- Division of Neurodegenerative Disorders, Department of Neurology, Medical Faculty Mannheim, Mannheim Center for Translational Neurosciences, Heidelberg University, Mannheim, Germany
| | | | - Angelika B Harbauer
- Institute of Neuronal Cell Biology, Technical University of Munich, Munich, Germany.,Max Planck Institute of Neurobiology, Martinsried, Germany.,Munich Cluster for Systems Neurology, Munich, Germany
| | - Dorothee Dormann
- Institute for Molecular Physiology, Johannes Gutenberg-University Mainz, Mainz, Germany.,Institute of Molecule Biology, Mainz, Germany
| | - Jörn Dengjel
- Department of Biology, University of Fribourg, Fribourg, Switzerland
| | - Dieter Edbauer
- Munich Cluster for Systems Neurology, Medical Faculty, Ludwig-Maximilians-University München, Munich, Germany.,German Center for Neurodegenerative Diseases Munich, Munich, Germany
| | - Christian Behrends
- Munich Cluster for Systems Neurology, Medical Faculty, Ludwig-Maximilians-University München, Munich, Germany
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29
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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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30
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Li Z, Liu X, Liu M. Stress Granule Homeostasis, Aberrant Phase Transition, and Amyotrophic Lateral Sclerosis. ACS Chem Neurosci 2022; 13:2356-2370. [PMID: 35905138 DOI: 10.1021/acschemneuro.2c00262] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease. In recent years, a large number of ALS-related mutations have been discovered to have a strong link to stress granules (SGs). SGs are cytoplasmic ribonucleoprotein condensates mediated by liquid-liquid phase separation (LLPS) of biomacromolecules. They help cells cope with stress. The normal physiological functions of SGs are dependent on three key aspects of SG "homeostasis": SG assembly, disassembly, and SG components. Any of these three aspects can be disrupted, resulting in abnormalities in the cellular stress response and leading to cytotoxicity. Several ALS-related pathogenic mutants have abnormal LLPS abilities that disrupt SG homeostasis, and some of them can even cause aberrant phase transitions. As a result, ALS-related mutants may disrupt various aspects of SG homeostasis by directly disturbing the intermolecular interactions or affecting core SG components, thus disrupting the phase equilibrium of the cytoplasm during stress. Considering that the importance of the "global view" of SG homeostasis in ALS pathogenesis has not received enough attention, we first systematically summarize the physiological regulatory mechanism of SG homeostasis based on LLPS and then examine ALS pathogenesis from the perspective of disrupted SG homeostasis and aberrant phase transition of biomacromolecules.
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Affiliation(s)
- Zhanxu Li
- Xiangya School of Medicine, Central South University, Changsha 410078, Hunan, China
| | - Xionghao Liu
- Center for Medical Genetics & Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha 410008, Hunan, China
| | - Mujun Liu
- Department of Cell Biology, School of Life Sciences, Central South University, Changsha 410078, Hunan, China
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31
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Crosstalk between Biomolecular Condensates and Proteostasis. Cells 2022; 11:cells11152415. [PMID: 35954258 PMCID: PMC9368065 DOI: 10.3390/cells11152415] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Revised: 07/19/2022] [Accepted: 07/21/2022] [Indexed: 12/23/2022] Open
Abstract
Proper homeostasis of the proteome, referred to as proteostasis, is maintained by chaperone-dependent refolding of misfolded proteins and by protein degradation via the ubiquitin-proteasome system and the autophagic machinery. This review will discuss a crosstalk between biomolecular condensates and proteostasis, whereby the crowding of proteostasis factors into macromolecular assemblies is often established by phase separation of membraneless biomolecular condensates. Specifically, ubiquitin and other posttranslational modifications come into play as agents of phase separation, essential for the formation of condensates and for ubiquitin-proteasome system activity. Furthermore, an intriguing connection associates malfunction of the same pathways to the accumulation of misfolded and ubiquitinated proteins in aberrant condensates, the formation of protein aggregates, and finally, to the pathogenesis of neurodegenerative diseases. The crosstalk between biomolecular condensates and proteostasis is an emerging theme in cellular and disease biology and further studies will focus on delineating specific molecular pathways involved in the pathogenesis of amyotrophic lateral sclerosis (ALS) and other neurodegenerative diseases.
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32
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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: 22] [Impact Index Per Article: 11.0] [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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33
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Houghton OH, Mizielinska S, Gomez-Suaga P. The Interplay Between Autophagy and RNA Homeostasis: Implications for Amyotrophic Lateral Sclerosis and Frontotemporal Dementia. Front Cell Dev Biol 2022; 10:838402. [PMID: 35573690 PMCID: PMC9096704 DOI: 10.3389/fcell.2022.838402] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 04/14/2022] [Indexed: 01/18/2023] Open
Abstract
Amyotrophic lateral sclerosis and frontotemporal dementia are neurodegenerative disorders that lie on a disease spectrum, sharing genetic causes and pathology, and both without effective therapeutics. Two pathways that have been shown to play major roles in disease pathogenesis are autophagy and RNA homeostasis. Intriguingly, there is an increasing body of evidence suggesting a critical interplay between these pathways. Autophagy is a multi-stage process for bulk and selective clearance of malfunctional cellular components, with many layers of regulation. Although the majority of autophagy research focuses on protein degradation, it can also mediate RNA catabolism. ALS/FTD-associated proteins are involved in many stages of autophagy and autophagy-mediated RNA degradation, particularly converging on the clearance of persistent pathological stress granules. In this review, we will summarise the progress in understanding the autophagy-RNA homeostasis interplay and how that knowledge contributes to our understanding of the pathobiology of ALS/FTD.
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Affiliation(s)
- O H Houghton
- Department of Basic and Clinical Neuroscience, Institute of Psychiatry, Psychology and Neuroscience, King's College London, Maurice Wohl Clinical Neuroscience Institute, London, United Kingdom.,UK Dementia Research Institute at King's College London, London, United Kingdom
| | - S Mizielinska
- Department of Basic and Clinical Neuroscience, Institute of Psychiatry, Psychology and Neuroscience, King's College London, Maurice Wohl Clinical Neuroscience Institute, London, United Kingdom.,UK Dementia Research Institute at King's College London, London, United Kingdom
| | - P Gomez-Suaga
- Department of Basic and Clinical Neuroscience, Institute of Psychiatry, Psychology and Neuroscience, King's College London, Maurice Wohl Clinical Neuroscience Institute, London, United Kingdom.,Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Enfermería y Terapia Ocupacional, Universidad de Extremadura, Cáceres, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain.,Instituto Universitario de Investigación Biosanitaria de Extremadura (INUBE), Cáceres, Spain
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34
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Kuechler ER, Jacobson M, Mayor T, Gsponer J. GraPES: The Granule Protein Enrichment Server for prediction of biological condensate constituents. Nucleic Acids Res 2022; 50:W384-W391. [PMID: 35474477 PMCID: PMC9252806 DOI: 10.1093/nar/gkac279] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2022] [Revised: 03/27/2022] [Accepted: 04/09/2022] [Indexed: 01/30/2023] Open
Abstract
Phase separation-based condensate formation is a novel working paradigm in biology, helping to rationalize many important cellular phenomena including the assembly of membraneless organelles. Uncovering the functional impact of cellular condensates requires a better knowledge of these condensates’ constituents. Herein, we introduce the webserver GraPES (Granule Protein Enrichment Server), a user-friendly online interface containing the MaGS and MaGSeq predictors, which provide propensity scores for proteins’ localization into cellular condensates. Our webpage contains models trained on human (Homo sapiens) and yeast (Saccharomyces cerevisiae) stress granule proteins. MaGS utilizes experimentally-based protein features for prediction, whereas MaGSeq is an entirely protein sequence-based implementation. GraPES is implemented in HTML/CSS and Javascript and is freely available for public use at https://grapes.msl.ubc.ca/. Documentation for using the provided webtools, descriptions of their methodology, and implementation notes can be found on the webpage.
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Affiliation(s)
- Erich R Kuechler
- Department of Biochemistry and Molecular Biology, Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada
| | - Matthew Jacobson
- Department of Biochemistry and Molecular Biology, Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada
| | - Thibault Mayor
- Department of Biochemistry and Molecular Biology, Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada
| | - Jörg Gsponer
- Department of Biochemistry and Molecular Biology, Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada
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35
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Role of the Ubiquitin System in Stress Granule Metabolism. Int J Mol Sci 2022; 23:ijms23073624. [PMID: 35408984 PMCID: PMC8999021 DOI: 10.3390/ijms23073624] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Revised: 03/24/2022] [Accepted: 03/25/2022] [Indexed: 02/01/2023] Open
Abstract
Eukaryotic cells react to various stress conditions with the rapid formation of membrane-less organelles called stress granules (SGs). SGs form by multivalent interactions between RNAs and RNA-binding proteins and are believed to protect stalled translation initiation complexes from stress-induced degradation. SGs contain hundreds of different mRNAs and proteins, and their assembly and disassembly are tightly controlled by post-translational modifications. The ubiquitin system, which mediates the covalent modification of target proteins with the small protein ubiquitin (‘ubiquitylation’), has been implicated in different aspects of SG metabolism, but specific functions in SG turnover have only recently emerged. Here, we summarize the evidence for the presence of ubiquitylated proteins at SGs, review the functions of different components of the ubiquitin system in SG formation and clearance, and discuss the link between perturbed SG clearance and the pathogenesis of neurodegenerative disorders. We conclude that the ubiquitin system plays an important, medically relevant role in SG biology.
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36
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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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Davidson JM, Chung RS, Lee A. The converging roles of sequestosome-1/p62 in the molecular pathways of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Neurobiol Dis 2022; 166:105653. [PMID: 35143965 DOI: 10.1016/j.nbd.2022.105653] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Revised: 01/18/2022] [Accepted: 02/03/2022] [Indexed: 01/03/2023] Open
Abstract
Investigations into the pathogenetic mechanisms underlying amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) have provided significant insight into the disease. At the cellular level, ALS and FTD are classified as proteinopathies, which is motor neuron degeneration and death characterized by pathological protein aggregates or dysregulated proteostasis. At both the clinical and molecular level there are common signaling pathways dysregulated across the ALS and FTD spectrum (ALS/FTD). Sequestosome-1/p62 is a multifunctional scaffold protein with roles in several signaling pathways including proteostasis, protein degradation via the ubiquitin proteasome system and autophagy, the antioxidant response, inflammatory response, and apoptosis. Notably these pathways are dysregulated in ALS and FTD. Mutations in the functional domains of p62 provide links to the pathogenetic mechanisms of p62 and dyshomeostasis of p62 levels is noted in several types of ALS and FTD. We present here that the dysregulated ALS and FTD signaling pathways are linked, with p62 converging the molecular mechanisms. This review summarizes the current literature on the complex role of p62 in the pathogenesis across the ALS/FTD spectrum. The focus is on the underlying convergent molecular mechanisms of ALS and FTD-associated proteins and pathways that dysregulate p62 levels or are dysregulated by p62, with emphasis on how p62 is implicated across the ALS/FTD spectrum.
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Affiliation(s)
- Jennilee M Davidson
- Centre for Motor Neuron Disease Research, Macquarie Medical School, Faculty of Medicine, Health and Human Sciences, Macquarie University, 2 Technology Place, NSW 2109, Australia..
| | - Roger S Chung
- Centre for Motor Neuron Disease Research, Macquarie Medical School, Faculty of Medicine, Health and Human Sciences, Macquarie University, 2 Technology Place, NSW 2109, Australia..
| | - Albert Lee
- Centre for Motor Neuron Disease Research, Macquarie Medical School, Faculty of Medicine, Health and Human Sciences, Macquarie University, 2 Technology Place, NSW 2109, Australia..
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38
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Carey JL, Guo L. Liquid-Liquid Phase Separation of TDP-43 and FUS in Physiology and Pathology of Neurodegenerative Diseases. Front Mol Biosci 2022; 9:826719. [PMID: 35187086 PMCID: PMC8847598 DOI: 10.3389/fmolb.2022.826719] [Citation(s) in RCA: 62] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 01/11/2022] [Indexed: 12/12/2022] Open
Abstract
Liquid-liquid phase separation of RNA-binding proteins mediates the formation of numerous membraneless organelles with essential cellular function. However, aberrant phase transition of these proteins leads to the formation of insoluble protein aggregates, which are pathological hallmarks of neurodegenerative diseases including ALS and FTD. TDP-43 and FUS are two such RNA-binding proteins that mislocalize and aggregate in patients of ALS and FTD. They have similar domain structures that provide multivalent interactions driving their phase separation in vitro and in the cellular environment. In this article, we review the factors that mediate and regulate phase separation of TDP-43 and FUS. We also review evidences that connect the phase separation property of TDP-43 and FUS to their functional roles in cells. Aberrant phase transition of TDP-43 and FUS leads to protein aggregation and disrupts their regular cell function. Therefore, restoration of functional protein phase of TDP-43 and FUS could be beneficial for neuronal cells. We discuss possible mechanisms for TDP-43 and FUS aberrant phase transition and aggregation while reviewing the methods that are currently being explored as potential therapeutic strategies to mitigate aberrant phase transition and aggregation of TDP-43 and FUS.
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Nedelsky NB, Taylor JP. Pathological phase transitions in ALS-FTD impair dynamic RNA-protein granules. RNA (NEW YORK, N.Y.) 2022; 28:97-113. [PMID: 34706979 PMCID: PMC8675280 DOI: 10.1261/rna.079001.121] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
The genetics of human disease serves as a robust and unbiased source of insight into human biology, both revealing fundamental cellular processes and exposing the vulnerabilities associated with their dysfunction. Over the last decade, the genetics of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) have epitomized this concept, as studies of ALS-FTD-causing mutations have yielded fundamental discoveries regarding the role of biomolecular condensation in organizing cellular contents while implicating disturbances in condensate dynamics as central drivers of neurodegeneration. Here we review this genetic evidence, highlight its intersection with patient pathology, and discuss how studies in model systems have revealed a role for aberrant condensation in neuronal dysfunction and death. We detail how multiple, distinct types of disease-causing mutations promote pathological phase transitions that disturb the dynamics and function of ribonucleoprotein (RNP) granules. Dysfunction of RNP granules causes pleiotropic defects in RNA metabolism and can drive the evolution of these structures to end-stage pathological inclusions characteristic of ALS-FTD. We propose that aberrant phase transitions of these complex condensates in cells provide a parsimonious explanation for the widespread cellular abnormalities observed in ALS as well as certain histopathological features that characterize late-stage disease.
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Affiliation(s)
- Natalia B Nedelsky
- Department of Cell and Molecular Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
| | - J Paul Taylor
- Department of Cell and Molecular Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
- Howard Hughes Medical Institute, Chevy Chase, Maryland 20815, USA
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40
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Rhine K, Skanchy S, Myong S. Single-molecule and ensemble methods to probe RNP nucleation and condensate properties. Methods 2022; 197:74-81. [PMID: 33610691 PMCID: PMC8374000 DOI: 10.1016/j.ymeth.2021.02.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Revised: 02/02/2021] [Accepted: 02/13/2021] [Indexed: 01/03/2023] Open
Abstract
Biomolecular condensates often consist of intrinsically disordered protein and RNA molecules, which together promote the formation of membraneless organelles in cells. The nucleation, condensation, and maturation of condensates is a critical yet poorly understood process. Here, we present single-molecule and accompanying ensemble methods to quantify these processes more comprehensively. In particular, we focus on how to properly design and execute a single-molecule nucleation assay, in which we detect signals arising from individual units of fluorescently labeled RNA-binding proteins associating with an RNA substrate. The analysis of this data allows one to determine the kinetics involved with each step of nucleation. Complemented with meso-scale techniques that measure the biophysical properties of ribonucleoprotein condensates, the methods described herein are powerful tools that can be adopted for studying any protein-RNA interactions that promote phase separation.
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Affiliation(s)
- Kevin Rhine
- Program in Cell, Molecular, Developmental Biology, and Biophysics, Johns Hopkins University, 3400 N Charles St, Baltimore, MD 21218,Department of Biology, Johns Hopkins University, 3400 N Charles St, Baltimore, MD 21218
| | - Sophie Skanchy
- Department of Biophysics, Johns Hopkins University, 3400 N Charles St, Baltimore, MD 21218
| | - Sua Myong
- Program in Cell, Molecular, Developmental Biology, and Biophysics, Johns Hopkins University, 3400 N Charles St, Baltimore, MD 21218,Department of Biophysics, Johns Hopkins University, 3400 N Charles St, Baltimore, MD 21218,Department of Physics, Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, 506 S Wright St, Urbana, IL 61801,Corresponding Author;
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41
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Samanta N, Ribeiro SS, Becker M, Laborie E, Pollak R, Timr S, Sterpone F, Ebbinghaus S. Sequestration of Proteins in Stress Granules Relies on the In-Cell but Not the In Vitro Folding Stability. J Am Chem Soc 2021; 143:19909-19918. [PMID: 34788540 DOI: 10.1021/jacs.1c09589] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Stress granules (SGs) are among the most studied membraneless organelles that form upon heat stress (HS) to sequester unfolded, misfolded, or aggregated protein, supporting protein quality control (PQC) clearance. The folding states that are primarily associated with SGs, as well as the function of the phase separated environment in adjusting the energy landscapes, remain unknown. Here, we investigate the association of superoxide dismutase 1 (SOD1) proteins with different folding stabilities and aggregation propensities with condensates in cells, in vitro and by simulation. We find that irrespective of aggregation the folding stability determines the association of SOD1 with SGs in cells. In vitro and in silico experiments however suggest that the increased flexibility of the unfolded state constitutes only a minor driving force to associate with the dynamic biomolecular network of the condensate. Specific protein-protein interactions in the cytoplasm in comparison to SGs determine the partitioning of folding states between the respective phases during HS.
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Affiliation(s)
- Nirnay Samanta
- Institute of Physical and Theoretical Chemistry, TU Braunschweig, Rebenring 56, D-38106 Braunschweig, Germany
| | - Sara S Ribeiro
- Institute of Physical and Theoretical Chemistry, TU Braunschweig, Rebenring 56, D-38106 Braunschweig, Germany
| | - Mailin Becker
- Institute of Physical and Theoretical Chemistry, TU Braunschweig, Rebenring 56, D-38106 Braunschweig, Germany
| | - Emeline Laborie
- CNRS Laboratoire de Biochimie Théorique, Institut de Biologie Physico-Chimique, Université Paris Denis Diderot, Sorbonne Paris Cité, PSL Research University, 13 rue Pierre et Marie Curie, Paris 75005, France
| | - Roland Pollak
- Institute of Physical and Theoretical Chemistry, TU Braunschweig, Rebenring 56, D-38106 Braunschweig, Germany
| | - Stepan Timr
- CNRS Laboratoire de Biochimie Théorique, Institut de Biologie Physico-Chimique, Université Paris Denis Diderot, Sorbonne Paris Cité, PSL Research University, 13 rue Pierre et Marie Curie, Paris 75005, France.,J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, Dolejskova 2155/3, Prague 8 182 23, Czech Republic
| | - Fabio Sterpone
- CNRS Laboratoire de Biochimie Théorique, Institut de Biologie Physico-Chimique, Université Paris Denis Diderot, Sorbonne Paris Cité, PSL Research University, 13 rue Pierre et Marie Curie, Paris 75005, France
| | - Simon Ebbinghaus
- Institute of Physical and Theoretical Chemistry, TU Braunschweig, Rebenring 56, D-38106 Braunschweig, Germany
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Peng G, Gu A, Niu H, Chen L, Chen Y, Zhou M, Zhang Y, Liu J, Cai L, Liang D, Liu X, Liu M. Amyotrophic lateral sclerosis (ALS) linked mutation in Ubiquilin 2 affects stress granule assembly via TIA-1. CNS Neurosci Ther 2021; 28:105-115. [PMID: 34750982 PMCID: PMC8673703 DOI: 10.1111/cns.13757] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Revised: 09/28/2021] [Accepted: 10/15/2021] [Indexed: 12/17/2022] Open
Abstract
Aims The ubiquilin‐like protein ubiquilin 2 (UBQLN2) is associated with amyotrophic lateral sclerosis and frontotemporal degeneration (ALS/FTD). The biological function of UBQLN2 has previously been shown to be related to stress granules (SGs). In this study, we aimed to clarify the regulatory relationship between UBQLN2 and SGs. Methods In this study, we transfected UBQLN2‐WT or UBQLN2‐P497H plasmids into cell lines (HEK293T, HeLa), and observed the process of SG dynamics by immunofluorescence. Meanwhile, immunoblot analyses the protein changes of stress granules related components. Results We observed that ubiquilin 2 colocalizes with the SG component proteins G3BP1, TIA‐1, ATXN2, and PABPC1. In cells expressing WT UBQLN2 or P497H mutants, in the early stages of SG formation under oxidative stress, the percentage of cells with SGs and the number of SGs per cell decreased to varying degrees. Between WT and mutant, there was no significant difference in eIF2α activity after stress treatment. Interestingly, the UBQLN2 P497H mutant downregulates the level of TIA‐1. In addition, the overexpression of the UBQLN2 P497H mutant inhibited the phosphorylation of 4E‐BP1 and affected the nucleoplasmic distribution of TDP‐43. Conclusions Ubiquilin 2 colocalizes with the SG component proteins G3BP1, TIA‐1, ATXN2, and PABPC1. It participates in regulating SG dynamics. And UBQLN2 mutation affects the assembly of stress granules by regulating TIA‐1. In addition, the overexpression of the UBQLN2 P497H mutant inhibited the phosphorylation of 4E‐BP1 and affected the nuclear and cytoplasmic distribution of TDP‐43. These provide new insights into the role of UBQLN2 in oxidative stress and the pathogenesis of ALS.
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Affiliation(s)
- Guangnan Peng
- Center for Medical Genetics & Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Hunan, China
| | - Ao Gu
- Center for Medical Genetics & Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Hunan, China
| | - Hongyan Niu
- Center for Medical Genetics & Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Hunan, China
| | - Linlin Chen
- Center for Medical Genetics & Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Hunan, China
| | - Yan Chen
- Center for Medical Genetics & Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Hunan, China
| | - Miaojin Zhou
- Center for Medical Genetics & Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Hunan, China
| | - Yiti Zhang
- Center for Medical Genetics & Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Hunan, China
| | - Jie Liu
- Center for Regenerative Medicine, The First People's Hospital of Yunnan Province, Kunming, China
| | - Licong Cai
- School of Life Sciences, Central South University, Hunan, China
| | - Desheng Liang
- Center for Medical Genetics & Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Hunan, China.,Hunan Key Laboratory of Basic and Applied Hematology, Central South University, Hunan, China
| | - Xionghao Liu
- Center for Medical Genetics & Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Hunan, China.,Hunan Key Laboratory of Basic and Applied Hematology, Central South University, Hunan, China.,Hunan Key Laboratory of Animal Models for Human Diseases, Central South University, Hunan, China
| | - Mujun Liu
- Hunan Key Laboratory of Basic and Applied Hematology, Central South University, Hunan, China.,Hunan Key Laboratory of Animal Models for Human Diseases, Central South University, Hunan, China.,Department of Cell Biology, School of Life Sciences, Central South University, Hunan, China
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43
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Zhu H, Fu H, Cui T, Ning L, Shao H, Guo Y, Ke Y, Zheng J, Lin H, Wu X, Liu G, He J, Han X, Li W, Zhao X, Lu H, Wang D, Hu K, Shen X. RNAPhaSep: a resource of RNAs undergoing phase separation. Nucleic Acids Res 2021; 50:D340-D346. [PMID: 34718740 PMCID: PMC8728120 DOI: 10.1093/nar/gkab985] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 10/04/2021] [Accepted: 10/08/2021] [Indexed: 02/04/2023] Open
Abstract
Liquid-liquid phase separation (LLPS) partitions cellular contents, underlies the formation of membraneless organelles and plays essential biological roles. To date, most of the research on LLPS has focused on proteins, especially RNA-binding proteins. However, accumulating evidence has demonstrated that RNAs can also function as ‘scaffolds’ and play essential roles in seeding or nucleating the formation of granules. To better utilize the knowledge dispersed in published literature, we here introduce RNAPhaSep (http://www.rnaphasep.cn), a manually curated database of RNAs undergoing LLPS. It contains 1113 entries with experimentally validated RNA self-assembly or RNA and protein co-involved phase separation events. RNAPhaSep contains various types of information, including RNA information, protein information, phase separation experiment information and integrated annotation from multiple databases. RNAPhaSep provides a valuable resource for exploring the relationship between RNA properties and phase behaviour, and may further enhance our comprehensive understanding of LLPS in cellular functions and human diseases.
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Affiliation(s)
- Haibo Zhu
- Department of Intelligent Medical Engineering, School of Medical Technology and Engineering, Fujian Medical University, Fuzhou 350122, China.,School of Artificial Intelligence and Information Technology, Nanjing University of Chinese Medicine, Nanjing Jiangsu 210023, China
| | - Hao Fu
- Department of Intelligent Medical Engineering, School of Medical Technology and Engineering, Fujian Medical University, Fuzhou 350122, China.,School of Artificial Intelligence and Information Technology, Nanjing University of Chinese Medicine, Nanjing Jiangsu 210023, China
| | - Tianyu Cui
- Department of Bioinformatics, School of Basic Medical Sciences, Southern Medical University, Guangzhou 510515, China
| | - Lin Ning
- Department of Bioinformatics, School of Basic Medical Sciences, Southern Medical University, Guangzhou 510515, China
| | - Huaguo Shao
- Department of Intelligent Medical Engineering, School of Medical Technology and Engineering, Fujian Medical University, Fuzhou 350122, China.,Department of Biochemistry and Molecular Biology, School of Medicine & Holistic Integrative Medicine, Jiangsu Collaborative Innovation Center of Chinese Medicinal Resources Industrialization, Nanjing University of Chinese Medicine, Nanjing 210023, China
| | - Yehan Guo
- Department of Bioinformatics, Fujian Key Laboratory of Medical Bioinformatics, School of Medical Technology and Engineering, Fujian Medical University, Fuzhou 350122, China
| | - Yanting Ke
- Department of Bioinformatics, Fujian Key Laboratory of Medical Bioinformatics, School of Medical Technology and Engineering, Fujian Medical University, Fuzhou 350122, China
| | - Jiayi Zheng
- Department of Bioinformatics, Fujian Key Laboratory of Medical Bioinformatics, School of Medical Technology and Engineering, Fujian Medical University, Fuzhou 350122, China
| | - Hongyan Lin
- Department of Bioinformatics, Fujian Key Laboratory of Medical Bioinformatics, School of Medical Technology and Engineering, Fujian Medical University, Fuzhou 350122, China
| | - Xin Wu
- Department of Bioinformatics, Fujian Key Laboratory of Medical Bioinformatics, School of Medical Technology and Engineering, Fujian Medical University, Fuzhou 350122, China.,Key Laboratory of Ministry of Education for Gastrointestinal Cancer, School of Basic Medical Sciences, Fujian Medical University, Fuzhou 350122, China
| | - Guanghao Liu
- Department of Bioinformatics, Fujian Key Laboratory of Medical Bioinformatics, School of Medical Technology and Engineering, Fujian Medical University, Fuzhou 350122, China.,Key Laboratory of Ministry of Education for Gastrointestinal Cancer, School of Basic Medical Sciences, Fujian Medical University, Fuzhou 350122, China
| | - Jun He
- Department of Bioinformatics, Fujian Key Laboratory of Medical Bioinformatics, School of Medical Technology and Engineering, Fujian Medical University, Fuzhou 350122, China.,Key Laboratory of Ministry of Education for Gastrointestinal Cancer, School of Basic Medical Sciences, Fujian Medical University, Fuzhou 350122, China
| | - Xin Han
- Department of Biochemistry and Molecular Biology, School of Medicine & Holistic Integrative Medicine, Jiangsu Collaborative Innovation Center of Chinese Medicinal Resources Industrialization, Nanjing University of Chinese Medicine, Nanjing 210023, China
| | - Wenlin Li
- School of Artificial Intelligence and Information Technology, Nanjing University of Chinese Medicine, Nanjing Jiangsu 210023, China.,Jingwen Library, Nanjing University of Chinese Medicine, Nanjing 210023, China
| | - Xiaoyang Zhao
- State Key Laboratory of Organ Failure Research, Department of Developmental Biology, School of Basic Medical Sciences, Southern Medical University, Guangzhou 510515, China
| | - Huasong Lu
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Dong Wang
- Department of Bioinformatics, School of Basic Medical Sciences, Southern Medical University, Guangzhou 510515, China
| | - Kongfa Hu
- School of Artificial Intelligence and Information Technology, Nanjing University of Chinese Medicine, Nanjing Jiangsu 210023, China
| | - Xiaopei Shen
- Department of Intelligent Medical Engineering, School of Medical Technology and Engineering, Fujian Medical University, Fuzhou 350122, China.,Department of Bioinformatics, Fujian Key Laboratory of Medical Bioinformatics, School of Medical Technology and Engineering, Fujian Medical University, Fuzhou 350122, China.,Key Laboratory of Ministry of Education for Gastrointestinal Cancer, School of Basic Medical Sciences, Fujian Medical University, Fuzhou 350122, China
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Sternburg EL, Gruijs da Silva LA, Dormann D. Post-translational modifications on RNA-binding proteins: accelerators, brakes, or passengers in neurodegeneration? Trends Biochem Sci 2021; 47:6-22. [PMID: 34366183 DOI: 10.1016/j.tibs.2021.07.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Revised: 07/09/2021] [Accepted: 07/19/2021] [Indexed: 02/07/2023]
Abstract
RNA-binding proteins (RBPs) are critical players in RNA expression and metabolism, thus, the proper regulation of this class of proteins is critical for cellular health. Regulation of RBPs often occurs through post-translational modifications (PTMs), which allow the cell to quickly and efficiently respond to cellular and environmental stimuli. PTMs have recently emerged as important regulators of RBPs implicated in neurodegenerative disorders, in particular amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Here, we summarize how disease-associated PTMs influence the biophysical properties, molecular interactions, subcellular localization, and function of ALS/FTD-linked RBPs, such as FUS and TDP-43. We will discuss how PTMs are believed to play pathological, protective, or ambiguous roles in these neurodegenerative disorders.
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Affiliation(s)
- Erin L Sternburg
- Johannes Gutenberg-Universität (JGU) Mainz, Faculty of Biology, Mainz, Germany
| | - Lara A Gruijs da Silva
- Johannes Gutenberg-Universität (JGU) Mainz, Faculty of Biology, Mainz, Germany; Graduate School of Systemic Neurosciences (GSN), Munich, Germany
| | - Dorothee Dormann
- Johannes Gutenberg-Universität (JGU) Mainz, Faculty of Biology, Mainz, Germany; Institute of Molecular Biology (IMB), Mainz, Germany.
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45
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Zaepfel BL, Rothstein JD. RNA Is a Double-Edged Sword in ALS Pathogenesis. Front Cell Neurosci 2021; 15:708181. [PMID: 34349625 PMCID: PMC8326408 DOI: 10.3389/fncel.2021.708181] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Accepted: 06/22/2021] [Indexed: 11/13/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a progressive and fatal neurodegenerative disease that affects upper and lower motor neurons. Familial ALS accounts for a small subset of cases (<10-15%) and is caused by dominant mutations in one of more than 10 known genes. Multiple genes have been causally or pathologically linked to both ALS and frontotemporal dementia (FTD). Many of these genes encode RNA-binding proteins, so the role of dysregulated RNA metabolism in neurodegeneration is being actively investigated. In addition to defects in RNA metabolism, recent studies provide emerging evidence into how RNA itself can contribute to the degeneration of both motor and cortical neurons. In this review, we discuss the roles of altered RNA metabolism and RNA-mediated toxicity in the context of TARDBP, FUS, and C9ORF72 mutations. Specifically, we focus on recent studies that describe toxic RNA as the potential initiator of disease, disease-associated defects in specific RNA metabolism pathways, as well as how RNA-based approaches can be used as potential therapies. Altogether, we highlight the importance of RNA-based investigations into the molecular progression of ALS, as well as the need for RNA-dependent structural studies of disease-linked RNA-binding proteins to identify clear therapeutic targets.
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Affiliation(s)
- Benjamin L Zaepfel
- Biochemistry, Cellular and Molecular Biology Program, Johns Hopkins University School of Medicine, Baltimore, MD, United States.,Molecular Biology and Genetics Department, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Jeffrey D Rothstein
- Brain Science Institute, Johns Hopkins University School of Medicine, Baltimore, MD, United States.,Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, United States
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Lin BC, Phung TH, Higgins NR, Greenslade JE, Prado MA, Finley D, Karbowski M, Polster BM, Monteiro MJ. ALS/FTD mutations in UBQLN2 are linked to mitochondrial dysfunction through loss-of-function in mitochondrial protein import. Hum Mol Genet 2021; 30:1230-1246. [PMID: 33891006 PMCID: PMC8212775 DOI: 10.1093/hmg/ddab116] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Revised: 04/13/2021] [Accepted: 04/16/2021] [Indexed: 01/12/2023] Open
Abstract
UBQLN2 mutations cause amyotrophic lateral sclerosis (ALS) with frontotemporal dementia (FTD), but the pathogenic mechanisms by which they cause disease remain unclear. Proteomic profiling identified 'mitochondrial proteins' as comprising the largest category of protein changes in the spinal cord (SC) of the P497S UBQLN2 mouse model of ALS/FTD. Immunoblots confirmed P497S animals have global changes in proteins predictive of a severe decline in mitochondrial health, including oxidative phosphorylation (OXPHOS), mitochondrial protein import and network dynamics. Functional studies confirmed mitochondria purified from the SC of P497S animals have age-dependent decline in nearly all steps of OXPHOS. Mitochondria cristae deformities were evident in spinal motor neurons of aged P497S animals. Knockout (KO) of UBQLN2 in HeLa cells resulted in changes in mitochondrial proteins and OXPHOS activity similar to those seen in the SC. KO of UBQLN2 also compromised targeting and processing of the mitochondrial import factor, TIMM44, resulting in accumulation in abnormal foci. The functional OXPHOS deficits and TIMM44-targeting defects were rescued by reexpression of WT UBQLN2 but not by ALS/FTD mutant UBQLN2 proteins. In vitro binding assays revealed ALS/FTD mutant UBQLN2 proteins bind weaker with TIMM44 than WT UBQLN2 protein, suggesting that the loss of UBQLN2 binding may underlie the import and/or delivery defect of TIMM44 to mitochondria. Our studies indicate a potential key pathogenic disturbance in mitochondrial health caused by UBQLN2 mutations.
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Affiliation(s)
- Brian C Lin
- Program in Neuroscience, University of Maryland School of Medicine, Baltimore, MD 21201, USA
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Trong H Phung
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Nicole R Higgins
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
- Program in Molecular Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Jessie E Greenslade
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Miguel A Prado
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Daniel Finley
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Mariusz Karbowski
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
- Program in Molecular Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Brian M Polster
- Program in Neuroscience, University of Maryland School of Medicine, Baltimore, MD 21201, USA
- Program in Molecular Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA
- Department of Anesthesiology, Center for Shock, Trauma and Anesthesiology Research, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Mervyn J Monteiro
- Program in Neuroscience, University of Maryland School of Medicine, Baltimore, MD 21201, USA
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
- Program in Molecular Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA
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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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48
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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: 22] [Impact Index Per Article: 7.3] [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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49
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Ruff KM, Dar F, Pappu RV. Polyphasic linkage and the impact of ligand binding on the regulation of biomolecular condensates. BIOPHYSICS REVIEWS 2021; 2:021302. [PMID: 34179888 PMCID: PMC8211317 DOI: 10.1063/5.0050059] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Accepted: 05/11/2021] [Indexed: 12/30/2022]
Abstract
Cellular matter can be spatially and temporally organized into membraneless biomolecular condensates. The current thinking is that these condensates form and dissolve via phase transitions driven by one or more condensate-specific multivalent macromolecules known as scaffolds. Cells likely regulate condensate formation and dissolution by exerting control over the concentrations of regulatory molecules, which we refer to as ligands. Wyman and Gill introduced the framework of polyphasic linkage to explain how ligands can exert thermodynamic control over phase transitions. This review focuses on describing the concepts of polyphasic linkage and the relevance of such a mechanism for controlling condensate formation and dissolution. We describe how ligand-mediated control over scaffold phase behavior can be quantified experimentally. Further, we build on recent studies to highlight features of ligands that make them suppressors vs drivers of phase separation. Finally, we highlight areas where advances are needed to further understand ligand-mediated control of condensates in complex cellular environments. These advances include understanding the effects of networks of ligands on condensate behavior and how ligands modulate phase transitions controlled by different combinations of homotypic and heterotypic interactions among scaffold macromolecules. Insights gained from the application of polyphasic linkage concepts should be useful for designing novel pharmaceutical ligands to regulate condensates.
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Affiliation(s)
- Kiersten M. Ruff
- Department of Biomedical Engineering and Center for Science and Engineering of Living Systems (CSELS), Washington University in St. Louis, St. Louis, Missouri 63130, USA
| | - Furqan Dar
- Department of Physics, Washington University in St. Louis, St. Louis, Missouri 63130, USA
| | - Rohit V. Pappu
- Department of Biomedical Engineering and Center for Science and Engineering of Living Systems (CSELS), Washington University in St. Louis, St. Louis, Missouri 63130, USA
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50
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Hou YJ, Zheng X, Zhong HM, Chen F, Yan GY, Cai KC. Structural dynamics of amyloid β peptide binding to acetylcholine receptor and virtual screening for effective inhibitors. CHINESE J CHEM PHYS 2021. [DOI: 10.1063/1674-0068/cjcp2008150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Affiliation(s)
- Yan-jun Hou
- College of Chemistry and Materials Science, Fujian Provincial Key Laboratory of Advanced Materials Oriented Chemical Engineering, Fujian Normal University, Fuzhou 350007, China
- Fujian Provincial Key Laboratory of Featured Biochemical and Chemical Materials, Ningde Normal University, Ningde 352100, China
- Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, Xiamen 361005, China
| | - Xuan Zheng
- Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Hong-mei Zhong
- College of Chemistry and Materials Science, Fujian Provincial Key Laboratory of Advanced Materials Oriented Chemical Engineering, Fujian Normal University, Fuzhou 350007, China
- Fujian Provincial Key Laboratory of Featured Biochemical and Chemical Materials, Ningde Normal University, Ningde 352100, China
- Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, Xiamen 361005, China
| | - Feng Chen
- Fujian Provincial Key Laboratory of Featured Biochemical and Chemical Materials, Ningde Normal University, Ningde 352100, China
| | - Gui-yang Yan
- Fujian Provincial Key Laboratory of Featured Biochemical and Chemical Materials, Ningde Normal University, Ningde 352100, China
| | - Kai-cong Cai
- College of Chemistry and Materials Science, Fujian Provincial Key Laboratory of Advanced Materials Oriented Chemical Engineering, Fujian Normal University, Fuzhou 350007, China
- Fujian Provincial Key Laboratory of Featured Biochemical and Chemical Materials, Ningde Normal University, Ningde 352100, China
- Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, Xiamen 361005, China
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