1
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Bin JM, Suminaite D, Benito-Kwiecinski SK, Kegel L, Rubio-Brotons M, Early JJ, Soong D, Livesey MR, Poole RJ, Lyons DA. Importin 13-dependent axon diameter growth regulates conduction speeds along myelinated CNS axons. Nat Commun 2024; 15:1790. [PMID: 38413580 PMCID: PMC10899189 DOI: 10.1038/s41467-024-45908-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Accepted: 02/06/2024] [Indexed: 02/29/2024] Open
Abstract
Axon diameter influences the conduction properties of myelinated axons, both directly, and indirectly through effects on myelin. However, we have limited understanding of mechanisms controlling axon diameter growth in the central nervous system, preventing systematic dissection of how manipulating diameter affects myelination and conduction along individual axons. Here we establish zebrafish to study axon diameter. We find that importin 13b is required for axon diameter growth, but does not affect cell body size or axon length. Using neuron-specific ipo13b mutants, we assess how reduced axon diameter affects myelination and conduction, and find no changes to myelin thickness, precision of action potential propagation, or ability to sustain high frequency firing. However, increases in conduction speed that occur along single myelinated axons with development are tightly linked to their growth in diameter. This suggests that axon diameter growth is a major driver of increases in conduction speeds along myelinated axons over time.
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Affiliation(s)
- Jenea M Bin
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH16 4SB, UK.
| | - Daumante Suminaite
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH16 4SB, UK
| | | | - Linde Kegel
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH16 4SB, UK
| | - Maria Rubio-Brotons
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH16 4SB, UK
| | - Jason J Early
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH16 4SB, UK
| | - Daniel Soong
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH16 4SB, UK
| | - Matthew R Livesey
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH16 4SB, UK
- Sheffield Institute for Translational Neuroscience, University of Sheffield, Sheffield, S10 2HQ, UK
- Neuroscience Institute, University of Sheffield, Sheffield, S10 2TN, UK
| | - Richard J Poole
- Department of Cell and Developmental Biology, University College London, London, WC1E 6BT, UK
| | - David A Lyons
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH16 4SB, UK.
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2
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The Nuclear Transporter Importin 13 Can Regulate Stress-Induced Cell Death through the Clusterin/KU70 Axis. Cells 2023; 12:cells12020279. [PMID: 36672214 PMCID: PMC9857240 DOI: 10.3390/cells12020279] [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: 11/11/2022] [Revised: 12/20/2022] [Accepted: 01/06/2023] [Indexed: 01/12/2023] Open
Abstract
The cellular response to environmental stresses, such as heat and oxidative stress, is dependent on extensive trafficking of stress-signalling molecules between the cytoplasm and nucleus, which potentiates stress-activated signalling pathways, eventually resulting in cell repair or death. Although Ran-dependent nucleocytoplasmic transport mediated by members of the importin (IPO) super family of nuclear transporters is believed to be responsible for nearly all macromolecular transit between nucleus and cytoplasm, it is paradoxically known to be significantly impaired under conditions of stress. Importin 13 (IPO13) is a unique bidirectional transporter that binds to and releases cargo in a Ran-dependent manner, but in some cases, cargo release from IPO13 is affected by loading of another cargo. To investigate IPO13's role in stress-activated pathways, we performed cell-based screens to identify a multitude of binding partners of IPO13 from human brain, lung, and testes. Analysis of the IPO13 interactome intriguingly indicated more than half of the candidate binding partners to be annotated for roles in stress responses; these included the pro-apoptotic protein nuclear clusterin (nCLU), as well as the nCLU-interacting DNA repair protein KU70. Here, we show, for the first time, that unlike other IPOs which are mislocalised and non-functional, IPO13 continues to translocate between the nucleus and cytoplasm under stress, retaining the capacity to import certain cargoes, such as nCLU, but not export others, such as KU70, as shown by analysis using fluorescence recovery after photobleaching. Importantly, depletion of IPO13 reduces stress-induced import of nCLU and protects against stress-induced cell death, with concomitant protection from DNA damage during stress. Overexpression/FACS experiments demonstrate that nCLU is dependent on IPO13 to trigger stress-induced cell death via apoptosis. Taken together, these results implicate IPO13 as a novel functional nuclear transporter in cellular stress, with a key role thereby in cell fate decision.
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3
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Nuclear Transporter IPO13 Is Central to Efficient Neuronal Differentiation. Cells 2022; 11:cells11121904. [PMID: 35741036 PMCID: PMC9221400 DOI: 10.3390/cells11121904] [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: 05/08/2022] [Revised: 05/28/2022] [Accepted: 06/02/2022] [Indexed: 11/16/2022] Open
Abstract
Molecular transport between the nucleus and cytoplasm of the cell is mediated by the importin superfamily of transport receptors, of which the bidirectional transporter Importin 13 (IPO13) is a unique member, with a critical role in early embryonic development through nuclear transport of key regulators, such as transcription factors Pax6, Pax3, and ARX. Here, we examined the role of IPO13 in neuronal differentiation for the first time, using a mouse embryonic stem cell (ESC) model and a monolayer-based differentiation protocol to compare IPO13−/− to wild type ESCs. Although IPO13−/− ESCs differentiated into neural progenitor cells, as indicated by the expression of dorsal forebrain progenitor markers, reduced expression of progenitor markers Pax6 and Nestin compared to IPO13−/− was evident, concomitant with reduced nuclear localisation/transcriptional function of IPO13 import cargo Pax6. Differentiation of IPO13−/− cells into neurons appeared to be strongly impaired, as evidenced by altered morphology, reduced expression of key neuronal markers, and altered response to the neurotransmitter glutamate. Our findings establish that IPO13 has a key role in ESC neuronal differentiation, in part through the nuclear transport of Pax6.
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4
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Gajewska KA, Ramialison M, Wagstaff KM, Jans DA. Transcriptomic profile dataset of embryonic stem cells (Wild-type and IPO13-Knock Out) with and without oxidative stress. Data Brief 2022; 42:108099. [PMID: 35434231 PMCID: PMC9010623 DOI: 10.1016/j.dib.2022.108099] [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: 01/11/2022] [Revised: 03/13/2022] [Accepted: 03/21/2022] [Indexed: 11/30/2022] Open
Abstract
The transcriptional response to cellular stress relies upon trafficking of regulators of transcription between the nuclear and cytoplasmic compartments, which occurs through action of members of the importin (IPO) superfamily. As a result of stresses such as oxidative or osmotic stress, one consequence is that importins become mislocalised, leading to inhibition of conventional nuclear transport. Here, we examine IPO13, which has a number of nonconventional characteristics, in the context of cell stress. We used Next Generation RNA Sequencing using the Illumina platform to compare the transcriptomes of Wild-type (WT) and IPO13-Knockout (KO) mouse embryonic stem cells in the absence and presence of oxidative stress. Differences in the mRNA expression profiles were observed between the cell lines in the absence and in the presence of stress. This data will be a key resource to enable characterization of the contribution of nuclear transporter IPO13 to cellular transcription in the absence and presence of oxidative stress, as well as more broadly, in the study of stem cell biology and effect of stress on embryonic stem cell transcription.
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Affiliation(s)
| | - Mirana Ramialison
- Australian Regenerative Medicine Institute and Systems Biology Institute, Monash University, Clayton, VIC, Australia
| | - Kylie M. Wagstaff
- Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
| | - David A. Jans
- Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
- Corresponding author.
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5
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Gajewska KA, Lescesen H, Ramialison M, Wagstaff KM, Jans DA. Nuclear transporter Importin-13 plays a key role in the oxidative stress transcriptional response. Nat Commun 2021; 12:5904. [PMID: 34625540 PMCID: PMC8501021 DOI: 10.1038/s41467-021-26125-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Accepted: 09/06/2021] [Indexed: 02/08/2023] Open
Abstract
The importin superfamily member Importin-13 is a bidirectional nuclear transporter. To delineate its functional roles, we performed transcriptomic analysis on wild-type and Importin-13-knockout mouse embryonic stem cells, revealing enrichment of differentially expressed genes involved in stress responses and apoptosis regulation. De novo promoter motif analysis on 277 Importin-13-dependent genes responsive to oxidative stress revealed an enrichment of motifs aligned to consensus sites for the transcription factors specificity protein 1, SP1, or Kruppel like factor 4, KLF4. Analysis of embryonic stem cells subjected to oxidative stress revealed that Importin-13-knockout cells were more resistant, with knockdown of SP1 or KLF4 helping protect wild-type embryonic stem cells against stress-induced death. Importin-13 was revealed to bind to SP1 and KLF4 in a cellular context, with a key role in oxidative stress-dependent nuclear export of both transcription factors. The results are integral to understanding stress biology, highlighting the importance of Importin-13 in the stress response.
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Affiliation(s)
- K. A. Gajewska
- grid.1002.30000 0004 1936 7857Biomedicine Discovery Institute, Monash University, Clayton, VIC Australia
| | - H. Lescesen
- grid.1002.30000 0004 1936 7857Biomedicine Discovery Institute, Monash University, Clayton, VIC Australia
| | - M. Ramialison
- grid.1002.30000 0004 1936 7857Australian Regenerative Medicine Institute and Systems Biology Institute, Monash University, Clayton, VIC Australia
| | - K. M. Wagstaff
- grid.1002.30000 0004 1936 7857Biomedicine Discovery Institute, Monash University, Clayton, VIC Australia
| | - D. A. Jans
- grid.1002.30000 0004 1936 7857Biomedicine Discovery Institute, Monash University, Clayton, VIC Australia
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6
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Fatima S, Wagstaff KM, Lim SM, Polo JM, Young JC, Jans DA. The nuclear transporter importin 13 is critical for cell survival during embryonic stem cell differentiation. Biochem Biophys Res Commun 2020; 534:141-148. [PMID: 33333437 DOI: 10.1016/j.bbrc.2020.11.099] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Accepted: 11/23/2020] [Indexed: 12/12/2022]
Abstract
Nuclear transporter Importin (Imp, Ipo) 13 is known to transport various mammalian cargoes into/out of the nucleus, but its role in directing cell-fate is unclear. Here we examine the role of Imp13 in the maintenance of pluripotency and differentiation of embryonic stem cells (ESCs) for the first time, using an embryonic body (EB)-based model. When induced to differentiate, Ipo13-/- ESCs displayed slow proliferation, reduced EB size, and lower expression of the proliferation marker KI67, concomitant with an increase in the number of TUNEL+ nuclei compared to wildtype ESCs. At days 5 and 10 of differentiation, Ipo13-/- EBs also showed enhanced loss of the pluripotency transcript OCT3/4, and barely detectable clusters of OCT3/4 positive cells. Day 5 Ipo13-/- EBs further exhibited reduced levels of the mesodermal markers Brachyury and Mixl1, correlating with reduced numbers of haemoglobinised cells generated. Our findings suggest that Imp13 is critical to ESC survival as well as early post-gastrulation differentiation.
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Affiliation(s)
- Shadma Fatima
- Nuclear Signalling Lab., Department of Biochemistry & Molecular Biology, Biomedicine Discovery Institute, Monash University, Clayton, Victoria, Australia
| | - Kylie M Wagstaff
- Nuclear Signalling Lab., Department of Biochemistry & Molecular Biology, Biomedicine Discovery Institute, Monash University, Clayton, Victoria, Australia
| | - Sue Mei Lim
- Australian Regenerative Medicine Institute, Biomedicine Discovery Institute, Department of Anatomy and Developmental Biology, Monash University, Clayton, Victoria, Australia
| | - Jose M Polo
- Australian Regenerative Medicine Institute, Biomedicine Discovery Institute, Department of Anatomy and Developmental Biology, Monash University, Clayton, Victoria, Australia
| | - Julia C Young
- Department of Anatomy and Developmental Biology, Biomedicine Discovery Institute, Monash University, Clayton, Victoria, Australia
| | - David A Jans
- Nuclear Signalling Lab., Department of Biochemistry & Molecular Biology, Biomedicine Discovery Institute, Monash University, Clayton, Victoria, Australia.
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7
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Miyamoto Y, Sasaki M, Miyata H, Monobe Y, Nagai M, Otani M, Whiley PAF, Morohoshi A, Oki S, Matsuda J, Akagi KI, Adachi J, Okabe M, Ikawa M, Yoneda Y, Loveland KL, Oka M. Genetic loss of importin α4 causes abnormal sperm morphology and impacts on male fertility in mouse. FASEB J 2020; 34:16224-16242. [PMID: 33058343 DOI: 10.1096/fj.202000768rr] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Revised: 09/27/2020] [Accepted: 09/29/2020] [Indexed: 11/11/2022]
Abstract
Importin α proteins play a central role in the transport of cargo from the cytoplasm to the nucleus. In this study, we observed that male knock-out mice for importin α4, which is encoded by the Kpna4 gene (Kpna4-/- ), were subfertile and yielded smaller litter sizes than those of wild-type (WT) males. In contrast, mice lacking the closely related importin α3 (Kpna3-/- ) were fertile. In vitro fertilization and sperm motility assays demonstrated that sperm from Kpna4-/- mice had significantly reduced quality and motility. In addition, acrosome reaction was also impaired in Kpna4-/- mice. Transmission electron microscopy revealed striking defects, including abnormal head morphology and multiple axoneme structures in the flagella of Kpna4-/- mice. A five-fold increase in the frequency of abnormalities in Kpna4-/- mice compared to WT mice indicates the functional importance of importin α4 in normal sperm development. Moreover, Nesprin-2, which is a component of the linker of nucleus and cytoskeleton complex, was expressed at lower levels in sperm from Kpna4-/- mice and was localized with abnormal axonemes, suggesting incorrect formation of the nuclear membrane-cytoskeleton structure during spermiogenesis. Proteomics analysis of Kpna4-/- testis showed significantly altered expression of proteins related to sperm formation, which provided evidence that genetic loss of importin α4 perturbed chromatin status. Collectively, these findings indicate that importin α4 is critical for establishing normal sperm morphology in mice, providing new insights into male germ cell development by highlighting the requirement of importin α4 for normal fertility.
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Affiliation(s)
- Yoichi Miyamoto
- Laboratory of Nuclear Transport Dynamics, National Institutes of Biomedical Innovation, Health and Nutrition (NIBIOHN), Osaka, Japan
| | - Mitsuho Sasaki
- Laboratory of Animal Models for Human Diseases, National Institutes of Biomedical Innovation, Health and Nutrition (NIBIOHN), Osaka, Japan
| | - Haruhiko Miyata
- Research Institute for Microbial Diseases, Osaka University, Osaka, Japan
| | - Yoko Monobe
- Section of Laboratory Equipment, National Institutes of Biomedical Innovation, Health and Nutrition (NIBIOHN), Osaka, Japan
| | - Masahiro Nagai
- Department of Frontier Bioscience, Graduate School of Frontier Bioscience, Osaka University, Osaka, Japan
| | - Mayumi Otani
- Laboratory of Nuclear Transport Dynamics, National Institutes of Biomedical Innovation, Health and Nutrition (NIBIOHN), Osaka, Japan
| | - Penny A F Whiley
- Centre for Reproductive Health, Hudson Institute of Medical Research, Clayton, VIC, Australia
| | - Akane Morohoshi
- Research Institute for Microbial Diseases, Osaka University, Osaka, Japan.,Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Shinya Oki
- Department of Drug Discovery Medicine, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Junichiro Matsuda
- Laboratory of Animal Models for Human Diseases, National Institutes of Biomedical Innovation, Health and Nutrition (NIBIOHN), Osaka, Japan
| | - Ken-Ichi Akagi
- Section of Laboratory Equipment, National Institutes of Biomedical Innovation, Health and Nutrition (NIBIOHN), Osaka, Japan
| | - Jun Adachi
- Laboratory of Proteome Research, National Institutes of Biomedical Innovation, Health and Nutrition (NIBIOHN), Osaka, Japan
| | - Masaru Okabe
- Research Institute for Microbial Diseases, Osaka University, Osaka, Japan
| | - Masahito Ikawa
- Research Institute for Microbial Diseases, Osaka University, Osaka, Japan.,Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Yoshihiro Yoneda
- National Institutes of Biomedical Innovation, Health and Nutrition (NIBIOHN), Osaka, Japan
| | - Kate L Loveland
- Centre for Reproductive Health, Hudson Institute of Medical Research, Clayton, VIC, Australia.,Department of Molecular and Translational Sciences, School of Clinical Sciences, Monash University, Clayton, VIC, Australia
| | - Masahiro Oka
- Laboratory of Nuclear Transport Dynamics, National Institutes of Biomedical Innovation, Health and Nutrition (NIBIOHN), Osaka, Japan
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8
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Zhang S, Williamson NA, Duvick L, Lee A, Orr HT, Korlin-Downs A, Yang P, Mok YF, Jans DA, Bogoyevitch MA. The ataxin-1 interactome reveals direct connection with multiple disrupted nuclear transport pathways. Nat Commun 2020; 11:3343. [PMID: 32620905 PMCID: PMC7334205 DOI: 10.1038/s41467-020-17145-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2017] [Accepted: 06/09/2020] [Indexed: 11/21/2022] Open
Abstract
The expanded polyglutamine (polyQ) tract form of ataxin-1 drives disease progression in spinocerebellar ataxia type 1 (SCA1). Although known to form distinctive intranuclear bodies, the cellular pathways and processes that polyQ-ataxin-1 influences remain poorly understood. Here we identify the direct and proximal partners constituting the interactome of ataxin-1[85Q] in Neuro-2a cells, pathways analyses indicating a significant enrichment of essential nuclear transporters, pointing to disruptions in nuclear transport processes in the presence of elevated levels of ataxin-1. Our direct assessments of nuclear transporters and their cargoes confirm these observations, revealing disrupted trafficking often with relocalisation of transporters and/or cargoes to ataxin-1[85Q] nuclear bodies. Analogous changes in importin-β1, nucleoporin 98 and nucleoporin 62 nuclear rim staining are observed in Purkinje cells of ATXN1[82Q] mice. The results highlight a disruption of multiple essential nuclear protein trafficking pathways by polyQ-ataxin-1, a key contribution to furthering understanding of pathogenic mechanisms initiated by polyQ tract proteins.
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Affiliation(s)
- Sunyuan Zhang
- Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, VIC, 3010, Australia
| | - Nicholas A Williamson
- Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, VIC, 3010, Australia
| | - Lisa Duvick
- Institute of Translational Neuroscience, and Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Alexander Lee
- Nuclear Signalling Lab., Department of Biochemistry and Molecular Biology, Monash University, Clayton, VIC, 3800, Australia
| | - Harry T Orr
- Institute of Translational Neuroscience, and Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Austin Korlin-Downs
- Institute of Translational Neuroscience, and Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Praseuth Yang
- Institute of Translational Neuroscience, and Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Yee-Foong Mok
- Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, VIC, 3010, Australia
| | - David A Jans
- Nuclear Signalling Lab., Department of Biochemistry and Molecular Biology, Monash University, Clayton, VIC, 3800, Australia.
| | - Marie A Bogoyevitch
- Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, VIC, 3010, Australia
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9
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Jans DA, Martin AJ, Wagstaff KM. Inhibitors of nuclear transport. Curr Opin Cell Biol 2019; 58:50-60. [PMID: 30826604 DOI: 10.1016/j.ceb.2019.01.001] [Citation(s) in RCA: 92] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2018] [Revised: 12/11/2018] [Accepted: 01/02/2019] [Indexed: 12/21/2022]
Abstract
Central to eukaryotic cell function, transport into and out of the nucleus is largely mediated by members of the Importin (IMP) superfamily of transporters of α- and β-types. The first inhibitor of nuclear transport, leptomycin B (LMB), was shown to be a specific inhibitor of the IMPβ homologue Exportin 1 (EXP1) almost 20 years ago, but it has only been in the last five or so years that new inhibitors of nuclear export as well as import have been identified and characterised. Of utility in biological research, these inhibitors include those that target-specific EXPs/IMPs, with accompanying toxicity profiles, as well as agents that specifically target particular nuclear import cargoes. Both types of inhibitors have begun to be tested in preclinical/clinical studies, with particular focus on limiting various types of cancer or treating viral infection, and the most advanced agent targeting EXP1 (Selinexor) has progressed successfully through >40 clinical trials for a range of high-grade cancers and is approaching FDA approval for a number of indications. Selectively inhibiting the nucleocytoplasmic trafficking of specific proteins of interest remains a challenge, but progress in the area of the host-pathogen interface holds promise for the future.
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Affiliation(s)
- David A Jans
- Nuclear Signaling Laboratory, Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Melbourne, Australia.
| | - Alexander J Martin
- Nuclear Signaling Laboratory, Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Melbourne, Australia
| | - Kylie M Wagstaff
- Nuclear Signaling Laboratory, Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Melbourne, Australia
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10
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PKA-site phosphorylation of importin13 regulates its subcellular localization and nuclear transport function. Biochem J 2018; 475:2699-2712. [PMID: 30045875 DOI: 10.1042/bcj20180082] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Revised: 07/12/2018] [Accepted: 07/16/2018] [Indexed: 01/25/2023]
Abstract
Importin 13 (IPO13) is a key member of the importin β superfamily, which can transport cargoes both into and out of the nucleus to contribute to a variety of important cellular processes. IPO13 is known to undergo phosphorylation, but the impact of this on function has not been investigated. Here, we show for the first time that IPO13 is phosphorylated by cAMP-dependent protein kinase A specifically at serine 193. Results from fluorescence recovery after photobleaching and fluorescence loss in photobleaching approaches establish that negative charge at serine 193 through phosphorylation or point mutation both reduces IPO13 nuclear import and increases its nuclear export. Importantly, phosphorylation also appears to enhance cargo interaction on the part of IPO13, with significant impact on localization, as shown for the Pax6 homeobox-containing transcription partner. This is the first report that IPO13 can be phosphorylated at Ser193 and that this modification regulates IPO13 subcellular localization and nucleocytoplasmic transport function, with important implications for IPO13's role in development and other processes.
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11
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Baade I, Spillner C, Schmitt K, Valerius O, Kehlenbach RH. Extensive Identification and In-depth Validation of Importin 13 Cargoes. Mol Cell Proteomics 2018; 17:1337-1353. [PMID: 29666159 PMCID: PMC6030721 DOI: 10.1074/mcp.ra118.000623] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Revised: 04/09/2018] [Indexed: 11/06/2022] Open
Abstract
Importin 13 is a member of the importin β family of transport receptors. Unlike most family members, importin 13 mediates both, nuclear protein import and export. To search for novel importin 13 cargoes, we used stable isotope labeling of amino acids in cell culture (SILAC) and mass spectrometry. Using stringent criteria, we identified 255 importin 13 substrates, including the known cargoes Ubc9, Mago and eIF1A, and validate many of them as transport cargoes by extensive biochemical and cell biological characterization. Several novel cargoes can also be transported by the export receptor CRM1, demonstrating a clear redundancy in receptor choice. Using importin 13 mutants, we show that many of the novel substrates contact regions on the transport receptor that are not used by Ubc9, Mago or eIF1A. Together, this study significantly expands the repertoire of importin 13 cargoes and sets the basis for a more detailed characterization of this extremely versatile transport receptor.
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Affiliation(s)
- Imke Baade
- From the ‡Department of Molecular Biology, Faculty of Medicine, Göttingen Center of Biosciences (GZMB), Georg-August-University Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
| | - Christiane Spillner
- From the ‡Department of Molecular Biology, Faculty of Medicine, Göttingen Center of Biosciences (GZMB), Georg-August-University Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
| | - Kerstin Schmitt
- §Department of Molecular Microbiology and Genetics, Institute of Microbiology and Genetics, GZMB, Georg-August-University Göttingen, Grisebachstr 8, 37077 Göttingen, Germany
| | - Oliver Valerius
- §Department of Molecular Microbiology and Genetics, Institute of Microbiology and Genetics, GZMB, Georg-August-University Göttingen, Grisebachstr 8, 37077 Göttingen, Germany
| | - Ralph H Kehlenbach
- From the ‡Department of Molecular Biology, Faculty of Medicine, Göttingen Center of Biosciences (GZMB), Georg-August-University Göttingen, Humboldtallee 23, 37073 Göttingen, Germany;
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12
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Brandi V, Di Lella V, Marino M, Ascenzi P, Polticelli F. A comprehensive in silico analysis of huntingtin and its interactome. J Biomol Struct Dyn 2017; 36:3155-3171. [PMID: 28920551 DOI: 10.1080/07391102.2017.1381646] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
A polyglutamine expansion of the N-terminal region of huntingtin (Htt) causes Huntington's disease, a severe neurodegenerative disorder. Htt huge multidomain structure, the presence of disordered regions, and the lack of sequence homologs of known structure, so far prevented structural studies of Htt, making the study of its structure-function relationships very difficult. In this work, the presence and location of five Htt ordered domains (named from Hunt1 to Hunt5) has been detected and the structure of these domains has been predicted for the first time using a combined threading/ab initio modeling approach. This work has led to the identification of a previously undetected HEAT repeats region in the Hunt3 domain. Furthermore, a putative function has been assigned to four out of the five domains. Hunt1 and Hunt5, displaying structural similarity with the regulatory subunit A of protein phosphatase 2A, are predicted to play a role in regulating the phosphorylation status of cellular proteins. Hunt2 and Hunt3 are predicted to be homologs of two yeast importins and to mediate vescicles transport and protein trafficking. Finally, a comprehensive analysis of the Htt interactome has been carried out and is discussed to provide a global picture of the Htt's structure-function relationships.
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Affiliation(s)
- Valentina Brandi
- a Department of Sciences , Roma Tre University, Viale Guglielmo Marconi 446 , Roma I-00146 , Italy
| | - Valentina Di Lella
- a Department of Sciences , Roma Tre University, Viale Guglielmo Marconi 446 , Roma I-00146 , Italy
| | - Maria Marino
- a Department of Sciences , Roma Tre University, Viale Guglielmo Marconi 446 , Roma I-00146 , Italy
| | - Paolo Ascenzi
- a Department of Sciences , Roma Tre University, Viale Guglielmo Marconi 446 , Roma I-00146 , Italy.,b Interdepartmental Laboratory for Electron Microscopy , Roma Tre University , Roma I-00146 , Italy
| | - Fabio Polticelli
- a Department of Sciences , Roma Tre University, Viale Guglielmo Marconi 446 , Roma I-00146 , Italy.,c National Institute of Nuclear Physics , Roma Tre University, Roma Tre Section , Roma I-00146 , Italy
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