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Chang YK, Lin YJ, Cheng CY, Tsai PC, Wang CY, Nielsen BL, Liu HJ. Nucleocytoplasmic shuttling of BEFV M protein-modulated by lamin A/C and chromosome maintenance region 1 through a transcription-, carrier- and energy-dependent pathway. Vet Microbiol 2024; 291:110026. [PMID: 38364467 DOI: 10.1016/j.vetmic.2024.110026] [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: 12/12/2023] [Revised: 01/30/2024] [Accepted: 02/07/2024] [Indexed: 02/18/2024]
Abstract
This study demonstrates for the first time that the matrix (M) protein of BEFV is a nuclear targeting protein that shuttles between the nucleus and the cytoplasm in a transcription-, carrier-, and energy-dependent manner. Experiments performed in both intact cells and digitonin-permeabilized cells revealed that M protein targets the nucleolus and requires carrier, cytosolic factors or energy input. By employing sequence and mutagenesis analyses, we have determined both nuclear localization signal (NLS) 6KKGKSK11 and nuclear export signal (NES) 98LIITSYL TI106 of M protein that are important for the nucleocytoplasmic shuttling of M protein. Furthermore, we found that both lamin A/C and chromosome maintenance region 1 (CRM-1) proteins could be coimmunoprecipitated and colocalized with the BEFV M protein. Knockdown of lamin A/C by shRNA and inhibition of CRM-1 by leptomycin B significantly reduced virus yield. Collectively, this study provides novel insights into nucleocytoplasmic shuttling of the BEFV M protein modulated by lamin A/C and CRM-1 and by a transcription- and carrier- and energy-dependent pathway.
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Affiliation(s)
- Yu-Kang Chang
- Department of Medical Research, Tungs' Taichung MetroHarbor Hospital, Taichung, Taiwan, ROC; Depertment of Post-Baccalaureate Medicine, National Chung Hsing University, Taichung, Taiwan, ROC
| | - Yi-Jyum Lin
- Institute of Molecular Biology, National Chung Hsing University, Taichung 402, Taiwan, ROC
| | - Ching-Yuan Cheng
- Institute of Molecular Biology, National Chung Hsing University, Taichung 402, Taiwan, ROC
| | - Pei-Chien Tsai
- Department of Life Sciences, National Chung Hsing University, Taichung, Taiwan, ROC
| | - Chi-Young Wang
- Department of Veterinary Medicine, National Chung Hsing University, Taichung 402, Taiwan, ROC; The iEGG and Animal Biotechnology Center, National Chung Hsing University, Taichung, Taiwan, ROC
| | - Brent L Nielsen
- Department of Microbiology and Molecular Biology, Brigham Young University, Provo, UT, USA
| | - Hung-Jen Liu
- Institute of Molecular Biology, National Chung Hsing University, Taichung 402, Taiwan, ROC; Department of Life Sciences, National Chung Hsing University, Taichung, Taiwan, ROC; The iEGG and Animal Biotechnology Center, National Chung Hsing University, Taichung, Taiwan, ROC; Ph.D Program in Translational Medicine, National Chung Hsing University, Taichung, Taiwan, ROC; Rong Hsing Research Center for Translational Medicine, National Chung Hsing, Taiwan, ROC.
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2
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Fare CM, Rhine K, Lam A, Myong S, Shorter J. A minimal construct of nuclear-import receptor Karyopherin-β2 defines the regions critical for chaperone and disaggregation activity. J Biol Chem 2023; 299:102806. [PMID: 36529289 PMCID: PMC9860449 DOI: 10.1016/j.jbc.2022.102806] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Revised: 12/02/2022] [Accepted: 12/05/2022] [Indexed: 12/23/2022] Open
Abstract
Karyopherin-β2 (Kapβ2) is a nuclear-import receptor that recognizes proline-tyrosine nuclear localization signals of diverse cytoplasmic cargo for transport to the nucleus. Kapβ2 cargo includes several disease-linked RNA-binding proteins with prion-like domains, such as FUS, TAF15, EWSR1, hnRNPA1, and hnRNPA2. These RNA-binding proteins with prion-like domains are linked via pathology and genetics to debilitating degenerative disorders, including amyotrophic lateral sclerosis, frontotemporal dementia, and multisystem proteinopathy. Remarkably, Kapβ2 prevents and reverses aberrant phase transitions of these cargoes, which is cytoprotective. However, the molecular determinants of Kapβ2 that enable these activities remain poorly understood, particularly from the standpoint of nuclear-import receptor architecture. Kapβ2 is a super-helical protein comprised of 20 HEAT repeats. Here, we design truncated variants of Kapβ2 and assess their ability to antagonize FUS aggregation and toxicity in yeast and FUS condensation at the pure protein level and in human cells. We find that HEAT repeats 8 to 20 of Kapβ2 recapitulate all salient features of Kapβ2 activity. By contrast, Kapβ2 truncations lacking even a single cargo-binding HEAT repeat display reduced activity. Thus, we define a minimal Kapβ2 construct for delivery in adeno-associated viruses as a potential therapeutic for amyotrophic lateral sclerosis/frontotemporal dementia, multisystem proteinopathy, and related disorders.
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Affiliation(s)
- Charlotte M Fare
- Department of Biochemistry and Biophysics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA; Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Kevin Rhine
- Program in Cell, Molecular, Developmental Biology, and Biophysics, Johns Hopkins University, Baltimore, Maryland, USA; Department of Biophysics, Johns Hopkins University, Baltimore, Maryland, USA
| | - Andrew Lam
- Department of Biochemistry and Biophysics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Sua Myong
- Program in Cell, Molecular, Developmental Biology, and Biophysics, Johns Hopkins University, Baltimore, Maryland, USA; Department of Biophysics, Johns Hopkins University, Baltimore, Maryland, USA
| | - James Shorter
- Department of Biochemistry and Biophysics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA; Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA.
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3
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Pörschke M, Rodríguez-González I, Parfentev I, Urlaub H, Kehlenbach RH. Transportin 1 is a major nuclear import receptor of the nitric oxide synthase interacting protein. J Biol Chem 2023; 299:102932. [PMID: 36690276 PMCID: PMC9974451 DOI: 10.1016/j.jbc.2023.102932] [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: 05/19/2022] [Revised: 01/12/2023] [Accepted: 01/14/2023] [Indexed: 01/22/2023] Open
Abstract
The nitric oxide synthase interacting protein (NOSIP), an E3-ubiquitin ligase, is involved in various processes like neuronal development, craniofacial development, granulopoiesis, mitogenic signaling, apoptosis, and cell proliferation. The best-characterized function of NOSIP is the regulation of endothelial nitric oxide synthase activity by translocating the membrane-bound enzyme to the cytoskeleton, specifically in the G2 phase of the cell cycle. For this, NOSIP itself has to be translocated from its prominent localization, the nucleus, to the cytoplasm. Nuclear import of NOSIP was suggested to be mediated by the canonical transport receptors importin α/β. Recently, we found NOSIP in a proteomic screen as a potential importin 13 cargo. Here, we describe the nuclear shuttling characteristics of NOSIP in living cells and in vitro and show that it does not interact directly with importin α. Instead, it formed stable complexes with several importins (-β, -7, -β/7, -13, and transportin 1) and was also imported into the nucleus in digitonin-permeabilized cells by these factors. In living HeLa cells, transportin 1 seems to be the major nuclear import receptor for NOSIP. A detailed analysis of the NOSIP-transportin 1 interaction revealed a high affinity and an unusual binding mode, involving the N-terminal half of transportin 1. In contrast to nuclear import, nuclear export of NOSIP seems to occur mostly by passive diffusion. Thus, our results uncover additional layers in the larger process of endothelial nitric oxide synthase regulation.
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Affiliation(s)
- Marius Pörschke
- Department of Molecular Biology, Faculty of Medicine, GZMB, Georg-August-University Göttingen, Göttingen, Germany
| | - Inés Rodríguez-González
- Department of Molecular Biology, Faculty of Medicine, GZMB, Georg-August-University Göttingen, Göttingen, Germany
| | - Iwan Parfentev
- Bioanalytical Mass Spectrometry Group, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Henning Urlaub
- Bioanalytical Mass Spectrometry Group, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany,Bioanalytics Group, Institute of Clinical Chemistry, University Medical Center Göttingen, Göttingen, Germany
| | - Ralph H. Kehlenbach
- Department of Molecular Biology, Faculty of Medicine, GZMB, Georg-August-University Göttingen, Göttingen, Germany,For correspondence: Ralph H. Kehlenbach
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4
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Khalil B, Chhangani D, Wren MC, Smith CL, Lee JH, Li X, Puttinger C, Tsai CW, Fortin G, Morderer D, Gao J, Liu F, Lim CK, Chen J, Chou CC, Croft CL, Gleixner AM, Donnelly CJ, Golde TE, Petrucelli L, Oskarsson B, Dickson DW, Zhang K, Shorter J, Yoshimura SH, Barmada SJ, Rincon-Limas DE, Rossoll W. Nuclear import receptors are recruited by FG-nucleoporins to rescue hallmarks of TDP-43 proteinopathy. Mol Neurodegener 2022; 17:80. [PMID: 36482422 PMCID: PMC9733332 DOI: 10.1186/s13024-022-00585-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Accepted: 11/23/2022] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Cytoplasmic mislocalization and aggregation of TAR DNA-binding protein-43 (TDP-43) is a hallmark of the amyotrophic lateral sclerosis and frontotemporal dementia (ALS/FTD) disease spectrum, causing both nuclear loss-of-function and cytoplasmic toxic gain-of-function phenotypes. While TDP-43 proteinopathy has been associated with defects in nucleocytoplasmic transport, this process is still poorly understood. Here we study the role of karyopherin-β1 (KPNB1) and other nuclear import receptors in regulating TDP-43 pathology. METHODS We used immunostaining, immunoprecipitation, biochemical and toxicity assays in cell lines, primary neuron and organotypic mouse brain slice cultures, to determine the impact of KPNB1 on the solubility, localization, and toxicity of pathological TDP-43 constructs. Postmortem patient brain and spinal cord tissue was stained to assess KPNB1 colocalization with TDP-43 inclusions. Turbidity assays were employed to study the dissolution and prevention of aggregation of recombinant TDP-43 fibrils in vitro. Fly models of TDP-43 proteinopathy were used to determine the effect of KPNB1 on their neurodegenerative phenotype in vivo. RESULTS We discovered that several members of the nuclear import receptor protein family can reduce the formation of pathological TDP-43 aggregates. Using KPNB1 as a model, we found that its activity depends on the prion-like C-terminal region of TDP-43, which mediates the co-aggregation with phenylalanine and glycine-rich nucleoporins (FG-Nups) such as Nup62. KPNB1 is recruited into these co-aggregates where it acts as a molecular chaperone that reverses aberrant phase transition of Nup62 and TDP-43. These findings are supported by the discovery that Nup62 and KPNB1 are also sequestered into pathological TDP-43 aggregates in ALS/FTD postmortem CNS tissue, and by the identification of the fly ortholog of KPNB1 as a strong protective modifier in Drosophila models of TDP-43 proteinopathy. Our results show that KPNB1 can rescue all hallmarks of TDP-43 pathology, by restoring its solubility and nuclear localization, and reducing neurodegeneration in cellular and animal models of ALS/FTD. CONCLUSION Our findings suggest a novel NLS-independent mechanism where, analogous to its canonical role in dissolving the diffusion barrier formed by FG-Nups in the nuclear pore, KPNB1 is recruited into TDP-43/FG-Nup co-aggregates present in TDP-43 proteinopathies and therapeutically reverses their deleterious phase transition and mislocalization, mitigating neurodegeneration.
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Affiliation(s)
- Bilal Khalil
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, 32224, USA
| | - Deepak Chhangani
- Department of Neurology, McKnight Brain Institute, Norman Fixel Institute for Neurological Diseases, University of Florida, Gainesville, FL, 32610, USA
| | - Melissa C Wren
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, 32224, USA
| | - Courtney L Smith
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, 32224, USA
- Mayo Clinic Graduate School of Biomedical Sciences, Neuroscience Track, Mayo Clinic, Jacksonville, FL, USA
| | - Jannifer H Lee
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, 32224, USA
- Mayo Clinic Graduate School of Biomedical Sciences, Neuroscience Track, Mayo Clinic, Jacksonville, FL, USA
| | - Xingli Li
- Department of Neurology, University of Michigan, Ann Arbor, MI, 48109, USA
| | | | - Chih-Wei Tsai
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, 32224, USA
| | - Gael Fortin
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, 32224, USA
| | - Dmytro Morderer
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, 32224, USA
| | - Junli Gao
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, 32224, USA
| | - Feilin Liu
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, 32224, USA
| | - Chun Kim Lim
- Graduate School of Biostudies, Kyoto University, Yoshida-konoe, Sakyo-ku, Kyoto, Japan
| | - Jingjiao Chen
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, 32224, USA
- Geriatric Department, Affiliated Hospital of Qingdao University, Qingdao, Shandong, China
| | - Ching-Chieh Chou
- Department of Biology, Stanford University, Stanford, CA, 94305, USA
| | - Cara L Croft
- Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, University of Florida, Gainesville, FL, 32610, USA
- UK Dementia Research Institute at University College London, London, UK
| | - Amanda M Gleixner
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15213, USA
- LiveLikeLou Center for ALS Research, University of Pittsburgh Brain Institute, Pittsburgh, PA, 15261, USA
| | - Christopher J Donnelly
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15213, USA
- LiveLikeLou Center for ALS Research, University of Pittsburgh Brain Institute, Pittsburgh, PA, 15261, USA
| | - Todd E Golde
- Department of Neurology, McKnight Brain Institute, Norman Fixel Institute for Neurological Diseases, University of Florida, Gainesville, FL, 32610, USA
- Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, University of Florida, Gainesville, FL, 32610, USA
| | | | | | - Dennis W Dickson
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, 32224, USA
| | - Ke Zhang
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, 32224, USA
| | - James Shorter
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Shige H Yoshimura
- Graduate School of Biostudies, Kyoto University, Yoshida-konoe, Sakyo-ku, Kyoto, Japan
| | - Sami J Barmada
- Department of Neurology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Diego E Rincon-Limas
- Department of Neurology, McKnight Brain Institute, Norman Fixel Institute for Neurological Diseases, University of Florida, Gainesville, FL, 32610, USA
- Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, University of Florida, Gainesville, FL, 32610, USA
- Genetics Institute, University of Florida, Gainesville, FL, 32610, USA
| | - Wilfried Rossoll
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, 32224, USA.
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5
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Okpara MO, Hermann C, van der Watt PJ, Garnett S, Blackburn JM, Leaner VD. A mass spectrometry-based approach for the identification of Kpnβ1 binding partners in cancer cells. Sci Rep 2022; 12:20171. [PMID: 36418423 PMCID: PMC9684564 DOI: 10.1038/s41598-022-24194-6] [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: 06/03/2022] [Accepted: 11/11/2022] [Indexed: 11/25/2022] Open
Abstract
Karyopherin beta 1 (Kpnβ1) is the principal nuclear importer of cargo proteins and plays a role in many cellular processes. Its expression is upregulated in cancer and essential for cancer cell viability, thus the identification of its binding partners might help in the discovery of anti-cancer therapeutic targets and cancer biomarkers. Herein, we applied immunoprecipitation coupled to mass spectrometry (IP-MS) to identify Kpnβ1 binding partners in normal and cancer cells. IP-MS identified 100 potential Kpnβ1 binding partners in non-cancer hTERT-RPE1, 179 in HeLa cervical cancer, 147 in WHCO5 oesophageal cancer and 176 in KYSE30 oesophageal cancer cells, including expected and novel interaction partners. 38 binding proteins were identified in all cell lines, with the majority involved in RNA metabolism. 18 binding proteins were unique to the cancer cells, with many involved in protein translation. Western blot analysis validated the interaction of known and novel binding partners with Kpnβ1 and revealed enriched interactions between Kpnβ1 and select proteins in cancer cells, including proteins involved in cancer development, such as Kpnα2, Ran, CRM1, CCAR1 and FUBP1. Together, this study shows that Kpnβ1 interacts with numerous proteins, and its enhanced interaction with certain proteins in cancer cells likely contributes to the cancer state.
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Affiliation(s)
- Michael O. Okpara
- grid.7836.a0000 0004 1937 1151Division of Medical Biochemistry and Structural Biology, University of Cape Town, Cape Town, South Africa
| | - Clemens Hermann
- grid.7836.a0000 0004 1937 1151Division of Chemical and Systems Biology, Department of Integrative Biomedical Sciences, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Pauline J. van der Watt
- grid.7836.a0000 0004 1937 1151Division of Medical Biochemistry and Structural Biology, University of Cape Town, Cape Town, South Africa ,grid.7836.a0000 0004 1937 1151Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Cape Town, South Africa
| | - Shaun Garnett
- grid.7836.a0000 0004 1937 1151Division of Chemical and Systems Biology, Department of Integrative Biomedical Sciences, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Jonathan M. Blackburn
- grid.7836.a0000 0004 1937 1151Division of Chemical and Systems Biology, Department of Integrative Biomedical Sciences, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa ,grid.7836.a0000 0004 1937 1151Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Cape Town, South Africa
| | - Virna D. Leaner
- grid.7836.a0000 0004 1937 1151Division of Medical Biochemistry and Structural Biology, University of Cape Town, Cape Town, South Africa ,grid.7836.a0000 0004 1937 1151SAMRC Gynaecology Cancer Research Centre, University of Cape Town, Cape Town, South Africa
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6
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Teratake Y, Kimura Y, Ishizaka Y. Role of karyopherin nuclear transport receptors in nuclear transport by nuclear trafficking peptide. Exp Cell Res 2021; 409:112893. [PMID: 34695436 DOI: 10.1016/j.yexcr.2021.112893] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Revised: 09/17/2021] [Accepted: 10/18/2021] [Indexed: 11/15/2022]
Abstract
Nuclear trafficking peptide (NTP), a cell-penetrating peptide (CPP) composed of 10 amino acids (aa) (RIFIHFRIGC), has potent nuclear trafficking activity. Recently, we established a protein-based cell engineering system by using NTP, but it remained elusive how NTP functions as a CPP with nuclear orientation. In the present study, we identified importin subunit β1 (IMB1) and transportin 1 (TNPO1) as cellular proteins underlying the activity of NTP. These karyopherin nuclear transport receptors were identified as candidate molecules by liquid chromatography/mass spectrometry analysis, and downregulation of each protein by small interfering RNA significantly reduced NTP activity (P < 0.01). Biochemical analyses revealed that NTP bound directly to both molecules, and the forced expression of an IMB1 fragment (296-516 aa) or TNPO1 fragment (1-297 aa), which both contain binding sites to NTP, reduced nuclear NTP-green fluorescent protein (GFP) levels when it was added to cell culture medium. NTP is derived from viral protein R (Vpr) of human immunodeficiency virus-1, and Vpr enters the nucleus and exerts pleiotropic functions. Notably, Vpr bound directly to IMB1 and TNPO1, and its function was significantly impaired by the forced expression of the 296-516-aa fragment of IMB1 and 1-297-aa fragment of TNPO1. Interestingly, NTP completely blocked the physical association of Vpr with IMB1 and TNPO1. Although the nuclear localization mechanism of Vpr remains unknown, our data suggest that NTP functions as a novel nuclear localization signal of Vpr.
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Affiliation(s)
- Yoichi Teratake
- Department of Intractable Diseases, Research Institute, National Center for Global Health and Medicine, 1-21-1 Toyama, Shinjuku-ku, Tokyo, 162-8655, Japan
| | - Yayoi Kimura
- Advanced Medical Research Center, Yokohama City University, 3-9 Fukuura, Knazawa-ku, Yokohama, Kanagawa, 236-0004, Japan
| | - Yukihito Ishizaka
- Department of Intractable Diseases, Research Institute, National Center for Global Health and Medicine, 1-21-1 Toyama, Shinjuku-ku, Tokyo, 162-8655, Japan.
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7
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A Novel Mutation in Cse1l Disrupts Brain and Eye Development with Specific Effects on Pax6 Expression. J Dev Biol 2021; 9:jdb9030027. [PMID: 34287339 PMCID: PMC8293161 DOI: 10.3390/jdb9030027] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 06/21/2021] [Accepted: 07/01/2021] [Indexed: 12/23/2022] Open
Abstract
Forward genetics in the mouse continues to be a useful and unbiased approach to identifying new genes and alleles with previously unappreciated roles in mammalian development and disease. Here, we report a new mouse allele of Cse1l that was recovered from an ENU mutagenesis screen. Embryos homozygous for the anteater allele of Cse1l display a number of variable phenotypes, with craniofacial and ocular malformations being the most obvious. We provide evidence that Cse1l is the causal gene through complementation with a novel null allele of Cse1l generated by CRISPR-Cas9 editing. While the variability in the anteater phenotype was high enough to preclude a detailed molecular analysis, we demonstrate a very penetrant reduction in Pax6 levels in the developing eye along with significant ocular developmental phenotypes. The eye gene discovery tool iSyTE shows Cse1l to be significantly expressed in the lens from early eye development stages in embryos through adulthood. Cse1l has not previously been shown to be required for organogenesis as homozygosity for a null allele results in very early lethality. Future detailed studies of Cse1l function in craniofacial and neural development will be best served with a conditional allele to circumvent the variable phenotypes we report here. We suggest that human next-generation (whole genome or exome) sequencing studies yielding variants of unknown significance in CSE1L could consider these findings as part of variant analysis.
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8
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Palacios V, Kimble GC, Tootle TL, Buszczak M. Importin-9 regulates chromosome segregation and packaging in Drosophila germ cells. J Cell Sci 2021; 134:237786. [PMID: 33632744 DOI: 10.1242/jcs.258391] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Accepted: 02/10/2021] [Indexed: 12/29/2022] Open
Abstract
Germ cells undergo distinct nuclear processes as they differentiate into gametes. Although these events must be coordinated to ensure proper maturation, the stage-specific transport of proteins in and out of germ cell nuclei remains incompletely understood. Our efforts to genetically characterize Drosophila genes that exhibit enriched expression in germ cells led to the finding that loss of the highly conserved Importin β/karyopherin family member Importin-9 (Ipo9, herein referring to Ranbp9) results in female and male sterility. Immunofluorescence and fluorescent in situ hybridization revealed that Ipo9KO mutants display chromosome condensation and segregation defects during meiosis. In addition, Ipo9KO mutant males form abnormally structured sperm and fail to properly exchange histones for protamines. Ipo9 physically interacts with proteasome proteins, and Ipo9 mutant males exhibit disruption of the nuclear localization of several proteasome components. Thus, Ipo9 coordinates the nuclear import of functionally related factors necessary for the completion of gametogenesis. This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Victor Palacios
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Garrett C Kimble
- Department of Anatomy and Cell Biology, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA
| | - Tina L Tootle
- Department of Anatomy and Cell Biology, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA
| | - Michael Buszczak
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.,Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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9
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Lee JY, Rahman FU, Kim EK, Cho SM, Kim HR, Lee K, Lee CS, Yoon WK, Moon OS, Seo YW, Won YS, Kim HC, Kim BH, Nam KH. Importin-11 is Essential for Normal Embryonic Development in Mice. Int J Med Sci 2020; 17:815-823. [PMID: 32218703 PMCID: PMC7085267 DOI: 10.7150/ijms.40697] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Accepted: 02/18/2020] [Indexed: 11/05/2022] Open
Abstract
Importin-11 (Ipo11) is a novel member of the human importin family of transport receptors (karyopherins), which are known to mediate the nucleocytoplasmic transport of protein and RNA cargos. Despite its role in the transport of protein, we found that knockout of Ipo11 nuclear import factor affects normal embryonic development and govern embryo-lethal phenotypes in mice. In this study, we for the first time produced a mouse line containing null mutation in Ipo11 gene utilized by gene trapping. The Ipo11-/- embryos showed an embryonic lethal phenotype. The Ipo11-/- embryos showed a reduced size at embryonic day 10.5 (E10.5) when compared with Ipo11+/+ or Ipo11+/- embryos and died by E11.5. Whereas Ipo11+/- mice were healthy and fertile, and there was no detectable changes in embryonic lethality and phenotype when reviewed. In the X-gal staining with the Ipo11-/- or Ipo11+/- embryos, strong X-gal staining positivity was detected systematically in the whole mount embryos at E10.5, although almost no X-gal positivity was detected at E9.5, indicating that the embryos die soon after the process of Ipo11 expression started. These results indicate that Ipo11 is essential for the normal embryonic development in mice.
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Affiliation(s)
- Ju-Young Lee
- Laboratory Animal Resource Center, Korea Research Institute of Bioscience and Biotechnology, Yeonjudanji-ro 30, Chungbuk 28116, Korea.,Department of Public Health, College of Natural Science, Keimyung University, Daegu, 42601, Korea
| | - Faiz Ur Rahman
- Laboratory Animal Resource Center, Korea Research Institute of Bioscience and Biotechnology, Yeonjudanji-ro 30, Chungbuk 28116, Korea
| | - Eun-Kyeung Kim
- Laboratory Animal Resource Center, Korea Research Institute of Bioscience and Biotechnology, Yeonjudanji-ro 30, Chungbuk 28116, Korea
| | - Sang-Mi Cho
- Laboratory Animal Resource Center, Korea Research Institute of Bioscience and Biotechnology, Yeonjudanji-ro 30, Chungbuk 28116, Korea
| | - Hae-Rim Kim
- Laboratory Animal Resource Center, Korea Research Institute of Bioscience and Biotechnology, Yeonjudanji-ro 30, Chungbuk 28116, Korea
| | - Kihoon Lee
- Laboratory Animal Resource Center, Korea Research Institute of Bioscience and Biotechnology, Yeonjudanji-ro 30, Chungbuk 28116, Korea
| | - Chin-Soo Lee
- Laboratory Animal Resource Center, Korea Research Institute of Bioscience and Biotechnology, Yeonjudanji-ro 30, Chungbuk 28116, Korea
| | - Won-Kee Yoon
- Laboratory Animal Resource Center, Korea Research Institute of Bioscience and Biotechnology, Yeonjudanji-ro 30, Chungbuk 28116, Korea
| | - Ok-Sung Moon
- Laboratory Animal Resource Center, Korea Research Institute of Bioscience and Biotechnology, Yeonjudanji-ro 30, Chungbuk 28116, Korea
| | - Young-Won Seo
- Laboratory Animal Resource Center, Korea Research Institute of Bioscience and Biotechnology, Yeonjudanji-ro 30, Chungbuk 28116, Korea
| | - Young-Suk Won
- Laboratory Animal Resource Center, Korea Research Institute of Bioscience and Biotechnology, Yeonjudanji-ro 30, Chungbuk 28116, Korea
| | - Hyoung-Chin Kim
- Laboratory Animal Resource Center, Korea Research Institute of Bioscience and Biotechnology, Yeonjudanji-ro 30, Chungbuk 28116, Korea
| | - Bae-Hwan Kim
- Department of Public Health, College of Natural Science, Keimyung University, Daegu, 42601, Korea
| | - Ki-Hoan Nam
- Laboratory Animal Resource Center, Korea Research Institute of Bioscience and Biotechnology, Yeonjudanji-ro 30, Chungbuk 28116, Korea
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10
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Kumeta M, Konishi HA, Zhang W, Sakagami S, Yoshimura SH. Prolines in the α-helix confer the structural flexibility and functional integrity of importin-β. J Cell Sci 2018; 131:jcs.206326. [PMID: 29142102 DOI: 10.1242/jcs.206326] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Accepted: 11/06/2017] [Indexed: 01/09/2023] Open
Abstract
The karyopherin family of nuclear transport receptors is composed of a long array of amphiphilic α-helices and undergoes flexible conformational changes to pass through the hydrophobic crowding barrier of the nuclear pore. Here, we focused on the characteristic enrichment of prolines in the middle of the outer α-helices of importin-β. When these prolines were substituted with alanine, nuclear transport activity was reduced drastically in vivo and in vitro, and caused a severe defect in mitotic progression. These mutations did not alter the overall folding of the helical repeat or affect its interaction with cargo or the regulatory factor Ran. However, in vitro and in silico analyses revealed that the mutant lost structural flexibility and could not undergo rapid conformational changes when transferring from a hydrophilic to hydrophobic environment or vice versa. These findings reveal the essential roles of prolines in ensuring the structural flexibility and functional integrity of karyopherins.
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Affiliation(s)
- Masahiro Kumeta
- Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto, 606-8501, Japan
| | - Hide A Konishi
- Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto, 606-8501, Japan
| | - Wanzhen Zhang
- Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto, 606-8501, Japan
| | - Sayuri Sakagami
- Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto, 606-8501, Japan
| | - Shige H Yoshimura
- Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto, 606-8501, Japan
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11
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Onischenko E, Tang JH, Andersen KR, Knockenhauer KE, Vallotton P, Derrer CP, Kralt A, Mugler CF, Chan LY, Schwartz TU, Weis K. Natively Unfolded FG Repeats Stabilize the Structure of the Nuclear Pore Complex. Cell 2017; 171:904-917.e19. [PMID: 29033133 DOI: 10.1016/j.cell.2017.09.033] [Citation(s) in RCA: 84] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2017] [Revised: 08/25/2017] [Accepted: 09/19/2017] [Indexed: 12/30/2022]
Abstract
Nuclear pore complexes (NPCs) are ∼100 MDa transport channels assembled from multiple copies of ∼30 nucleoporins (Nups). One-third of these Nups contain phenylalanine-glycine (FG)-rich repeats, forming a diffusion barrier, which is selectively permeable for nuclear transport receptors that interact with these repeats. Here, we identify an additional function of FG repeats in the structure and biogenesis of the yeast NPC. We demonstrate that GLFG-containing FG repeats directly bind to multiple scaffold Nups in vitro and act as NPC-targeting determinants in vivo. Furthermore, we show that the GLFG repeats of Nup116 function in a redundant manner with Nup188, a nonessential scaffold Nup, to stabilize critical interactions within the NPC scaffold needed for late steps of NPC assembly. Our results reveal a previously unanticipated structural role for natively unfolded GLFG repeats as Velcro to link NPC subcomplexes and thus add a new layer of connections to current models of the NPC architecture.
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Affiliation(s)
- Evgeny Onischenko
- Department of Biology, Institute of Biochemistry, Eidgenössische Technische Hochschule Zürich, Otto-Stern-Weg 3, CH-8093 Zurich, Switzerland
| | - Jeffrey H Tang
- Department of Biology, Institute of Biochemistry, Eidgenössische Technische Hochschule Zürich, Otto-Stern-Weg 3, CH-8093 Zurich, Switzerland
| | - Kasper R Andersen
- Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Kevin E Knockenhauer
- Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Pascal Vallotton
- Department of Biology, Institute of Biochemistry, Eidgenössische Technische Hochschule Zürich, Otto-Stern-Weg 3, CH-8093 Zurich, Switzerland
| | - Carina P Derrer
- Department of Biology, Institute of Biochemistry, Eidgenössische Technische Hochschule Zürich, Otto-Stern-Weg 3, CH-8093 Zurich, Switzerland
| | - Annemarie Kralt
- Department of Biology, Institute of Biochemistry, Eidgenössische Technische Hochschule Zürich, Otto-Stern-Weg 3, CH-8093 Zurich, Switzerland
| | - Christopher F Mugler
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Leon Y Chan
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Thomas U Schwartz
- Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Karsten Weis
- Department of Biology, Institute of Biochemistry, Eidgenössische Technische Hochschule Zürich, Otto-Stern-Weg 3, CH-8093 Zurich, Switzerland.
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12
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Wälde S, Thakar K, Hutten S, Spillner C, Nath A, Rothbauer U, Wiemann S, Kehlenbach RH. The nucleoporin Nup358/RanBP2 promotes nuclear import in a cargo- and transport receptor-specific manner. Traffic 2011; 13:218-33. [PMID: 21995724 DOI: 10.1111/j.1600-0854.2011.01302.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2011] [Revised: 10/11/2011] [Accepted: 10/11/2011] [Indexed: 12/31/2022]
Abstract
In vertebrates, the nuclear pore complex (NPC), the gate for transport of macromolecules between the nucleus and the cytoplasm, consists of approximately 30 different nucleoporins (Nups). The Nup and SUMO E3-ligase Nup358/RanBP2 are the major components of the cytoplasmic filaments of the NPC. In this study, we perform a structure-function analysis of Nup358 and describe its role in nuclear import of specific proteins. In a screen for nuclear proteins that accumulate in the cytoplasm upon Nup358 depletion, we identified proteins that were able to interact with Nup358 in a receptor-independent manner. These included the importin α/β-cargo DBC-1 (deleted in breast cancer 1) and DMAP-1 (DNA methyltransferase 1 associated protein 1). Strikingly, a short N-terminal fragment of Nup358 was sufficient to promote import of DBC-1, whereas DMAP-1 required a larger portion of Nup358 for stimulated import. Neither the interaction of RanGAP with Nup358 nor its SUMO-E3 ligase activity was required for nuclear import of all tested cargos. Together, Nup358 functions as a cargo- and receptor-specific assembly platform, increasing the efficiency of nuclear import of proteins through various mechanisms.
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Affiliation(s)
- Sarah Wälde
- Department of Biochemistry I, Faculty of Medicine, Georg-August-University of Göttingen, Humboldtallee 23, 37073, Göttingen, Germany
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13
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Kahms M, Hüve J, Wesselmann R, Farr JC, Baumgärtel V, Peters R. Lighting up the nuclear pore complex. Eur J Cell Biol 2011; 90:751-8. [DOI: 10.1016/j.ejcb.2011.04.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
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14
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Abstract
Internal membrane bound structures sequester all genetic material in eukaryotic cells. The most prominent of these structures is the nucleus, which is bounded by a double membrane termed the nuclear envelope (NE). Though this NE separates the nucleoplasm and genetic material within the nucleus from the surrounding cytoplasm, it is studded throughout with portals called nuclear pore complexes (NPCs). The NPC is a highly selective, bidirectional transporter for a tremendous range of protein and ribonucleoprotein cargoes. All the while the NPC must prevent the passage of nonspecific macromolecules, yet allow the free diffusion of water, sugars, and ions. These many types of nuclear transport are regulated at multiple stages, and the NPC carries binding sites for many of the proteins that modulate and modify the cargoes as they pass across the NE. Assembly, maintenance, and repair of the NPC must somehow occur while maintaining the integrity of the NE. Finally, the NPC appears to be an anchor for localization of many nuclear processes, including gene activation and cell cycle regulation. All these requirements demonstrate the complex design of the NPC and the integral role it plays in key cellular processes.
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Affiliation(s)
- Susan R Wente
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA.
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15
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Huenniger K, Krämer A, Soom M, Chang I, Köhler M, Depping R, Kehlenbach RH, Kaether C. Notch1 signaling is mediated by importins alpha 3, 4, and 7. Cell Mol Life Sci 2010; 67:3187-96. [PMID: 20454918 PMCID: PMC3128743 DOI: 10.1007/s00018-010-0378-7] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2009] [Revised: 04/09/2010] [Accepted: 04/20/2010] [Indexed: 11/28/2022]
Abstract
The Notch signaling pathway is an important regulation system for the development and self-renewal of different tissues. A specific feature of this signaling cascade is the function of Notch as a surface receptor and regulator of gene expression. Hence, Notch activation and signal transduction requires the proteolytic release of the Notch intracellular domain (NICD), which activates the transcription of cell-specific genes after its transport into the nucleus. To date, little is known about the mechanisms that mediate NICD nuclear import. We here show that transport of NICD into the nucleus is mediated by the canonical importin alpha/beta1 pathway. GST pull-down experiments revealed that NICD binds via one of its four potential nuclear localization signals to importins alpha3, alpha4, and alpha7, but not to alpha1 and alpha5. siRNA-mediated knockdown experiments showed that importins alpha3, alpha4 (and to a lesser extent, alpha7) mediate nuclear import of NICD and thus are directly involved in Notch signaling.
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Affiliation(s)
- Kerstin Huenniger
- Leibniz Institute for Age Research, Fritz Lipmann Institute, Beutenbergstr. 11, 07745, Jena, Germany
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16
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Kaláb P, Soderholm J. The design of Förster (fluorescence) resonance energy transfer (FRET)-based molecular sensors for Ran GTPase. Methods 2010; 51:220-32. [PMID: 20096786 DOI: 10.1016/j.ymeth.2010.01.022] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2010] [Accepted: 01/19/2010] [Indexed: 01/01/2023] Open
Abstract
The application of FRET-based molecular biosensors provided confirmation of the central model of Ran GTPase function and led to important new insights into its physiological role. In many fields of cell biology, methods employing FRET are a standard approach that is becoming increasingly accessible due to advances in instrumentation and available fluorophores. However, the optimal design of a FRET sensor remains to be the cornerstone of any successful FRET application. Utilizing the recent literature on FRET applications and our studies on Ran, we outline the basic considerations involved in designing molecular FRET sensors. We point to several broadly applicable principles that were used in many different FRET sensors that can detect a wide range of molecular events. Using the FRET sensors for Ran that we created as examples, we then focus on the practical aspects of FRET assays. We describe the preparation of a bipartite FRET sensor consisting of ECFP-Ran and EYFP-importin beta and its validation as a reporter for FRET-based high throughput screening in small molecule libraries. Finally, we review the design and optimization of monomolecular FRET sensors that monitor the RanGTP-RanBP1 interaction, and of sensors detecting the RanGTP-regulated importin beta cargo release.
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Affiliation(s)
- Petr Kaláb
- National Cancer Institute, NIH, Bethesda, MD 20892-4256, USA.
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17
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Peters R. Functionalization of a nanopore: the nuclear pore complex paradigm. BIOCHIMICA ET BIOPHYSICA ACTA 2009; 1793:1533-9. [PMID: 19596381 PMCID: PMC2756448 DOI: 10.1016/j.bbamcr.2009.06.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2009] [Revised: 06/26/2009] [Accepted: 06/30/2009] [Indexed: 10/20/2022]
Abstract
Biological cells maintain a myriad of nanopores which, although relying on the same basic small-hole principle, serve a large variety of functions. Here we consider how the nuclear pore complex (NPC), a large nanopore mediating the traffic between genetic material and protein synthesizing apparatus, is functionalized to carry out a set of transport functions. A major parameter of NPC functionalization is a lining of it external and internal surfaces with so-called phenylalanine glycine (FG) proteins. FG proteins integrate a multitude of transport factor binding sites into intrinsically disordered domains. This surprising finding has given rise to a number of transport models assigning direct gating functions to FG proteins. However, recent data suggest that the properties of FG proteins cannot be properly assessed by considering only the purified, transport-factor-stripped NPC. At physiological conditions transport factors may shape FG proteins in a way allotting an essential role to surface diffusion, reconciling tight binding with efficient transport. Thus, NPC studies are revealing both general traits and novel aspects of nanopore functionalization. In addition, they inspire artificial molecule sorters for proteomic and pharmaceutical applications.
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Affiliation(s)
- Reiner Peters
- The Rockefeller University, Laboratory for mass spectrometry and gaseous ion chemistry, 1230 York Avenue, New York, NY 10065, USA.
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18
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Vázquez-Iglesias L, Lostalé-Seijo I, Martínez-Costas J, Benavente J. Avian reovirus sigmaA localizes to the nucleolus and enters the nucleus by a nonclassical energy- and carrier-independent pathway. J Virol 2009; 83:10163-75. [PMID: 19640987 PMCID: PMC2747991 DOI: 10.1128/jvi.01080-09] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2009] [Accepted: 07/16/2009] [Indexed: 12/24/2022] Open
Abstract
Avian reovirus sigmaA is a double-stranded RNA (dsRNA)-binding protein that has been shown to stabilize viral core particles and to protect the virus against the antiviral action of interferon. To continue with the characterization of this viral protein, we have investigated its intracellular distribution in avian cells. Most sigmaA accumulates into cytoplasmic viral factories of infected cells, and yet a significant fraction was detected in the nucleolus. The protein also localizes in the nucleolus of transfected cells, suggesting that nucleolar targeting is not facilitated by the viral infection or by viral factors. Assays performed in both intact cells and digitonin-permeabilized cells demonstrate that sigmaA is able to enter the nucleus via a nucleoporin-dependent nondiffusional mechanism that does not require added cytosolic factors or energy input. These results indicate that sigmaA by itself is able to penetrate into the nucleus using a process that is mechanistically different from the classical nuclear localization signal/importin pathway. On the other hand, two sigmaA arginines that are necessary for dsRNA binding are also required for nucleolar localization, suggesting that dsRNA-binding and nucleolar targeting are intimately linked properties of the viral protein.
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Affiliation(s)
- Lorena Vázquez-Iglesias
- Departamento de Bioquímica y Biología Molecular, Facultad de Farmacia, Universidad de Santiago de Compostela, Santiago de Compostela, Spain
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19
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Naim B, Zbaida D, Dagan S, Kapon R, Reich Z. Cargo surface hydrophobicity is sufficient to overcome the nuclear pore complex selectivity barrier. EMBO J 2009; 28:2697-705. [PMID: 19680225 DOI: 10.1038/emboj.2009.225] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2009] [Accepted: 06/18/2009] [Indexed: 11/09/2022] Open
Abstract
To fulfil their function, nuclear pore complexes (NPCs) must discriminate between inert proteins and nuclear transport receptors (NTRs), admitting only the latter. This specific permeation is thought to depend on interactions between hydrophobic patches on NTRs and phenylalanine-glycine (FG) or related repeats that line the NPC. Here, we tested this premise directly by conjugating different hydrophobic amino-acid analogues to the surface of an inert protein and examining its ability to cross NPCs unassisted by NTRs. Conjugation of as few as four hydrophobic moieties was sufficient to enable passage of the protein through NPCs. Transport of the modified protein proceeded with rates comparable to those measured for the innate protein when bound to an NTR and was relatively insensitive both to the nature and density of the amino acids used to confer hydrophobicity. The latter observation suggests a non-specific, small, and plant interaction network between cargo and FG repeats.
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Affiliation(s)
- Bracha Naim
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, Israel
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20
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Abstract
Transport through the nuclear pore complex (NPC), a keystone of the eukaryotic building plan, is known to involve a large channel and an abundance of phenylalanine-glycine (FG) protein domains serving as binding sites for soluble nuclear transport receptors and their cargo complexes. However, the conformation of the FG domains in vivo, their arrangement in relation to the transport channel and their function(s) in transport are still vividly debated. Here, we revisit a number of representative transport models-specifically Brownian affinity gating, selective phase gating, reversible FG domain collapse, and reduction of dimensionality (ROD)-in the light of new data obtained by optical single transporter recording, optical superresolution microscopy, artificial nanopores, and many other techniques. The analysis suggests that a properly adapted, simplified version of the ROD model accounts well for the available data. This has implications for nucleocytoplasmic transport in general.
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Affiliation(s)
- Reiner Peters
- Laboratory of Mass Spectrometry and Gaseous Ion Chemistry, The Rockefeller University, New York, NY 10065 , USA.
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21
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Hutten S, Wälde S, Spillner C, Hauber J, Kehlenbach RH. The nuclear pore component Nup358 promotes transportin-dependent nuclear import. J Cell Sci 2009; 122:1100-10. [PMID: 19299463 DOI: 10.1242/jcs.040154] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Nup358 (also known as RanBP2), a component of the cytoplasmic filaments of the nuclear pore complex, has been implicated in various nucleocytoplasmic transport pathways. Here, we identify Nup358 as an important factor for transportin-mediated nuclear import. Depletion of Nup358 resulted in a strong inhibition of nuclear import of the human immunodeficiency virus type 1 (HIV-1) Rev protein. HIV-1 Rev is an RNA-binding protein that is required for CRM1 (also known as exportin 1)-dependent nuclear export of unspliced or partially spliced viral RNA. We show that transportin is the major nuclear import receptor for HIV-1 Rev in HeLa cells. Overexpression of transportin strongly promoted nuclear import of HIV-1 Rev in Nup358-depleted cells, indicating that the import receptor becomes rate-limiting under these conditions. Importantly, the import rate of other transportin-dependent proteins was also significantly reduced in Nup358-depleted cells. Our data therefore suggest a general role for Nup358 in transportin-mediated nuclear import.
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Affiliation(s)
- Saskia Hutten
- Department of Biochemistry I, Faculty of Medicine, Georg-August-University of Göttingen, 37073, Göttingen, Germany
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22
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Hutten S, Flotho A, Melchior F, Kehlenbach RH. The Nup358-RanGAP complex is required for efficient importin alpha/beta-dependent nuclear import. Mol Biol Cell 2008; 19:2300-10. [PMID: 18305100 DOI: 10.1091/mbc.e07-12-1279] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
In vertebrate cells, the nucleoporin Nup358/RanBP2 is a major component of the filaments that emanate from the nuclear pore complex into the cytoplasm. Nup358 forms a complex with SUMOylated RanGAP1, the GTPase activating protein for Ran. RanGAP1 plays a pivotal role in the establishment of a RanGTP gradient across the nuclear envelope and, hence, in the majority of nucleocytoplasmic transport pathways. Here, we investigate the roles of the Nup358-RanGAP1 complex and of soluble RanGAP1 in nuclear protein transport, combining in vivo and in vitro approaches. Depletion of Nup358 by RNA interference led to a clear reduction of importin alpha/beta-dependent nuclear import of various reporter proteins. In vitro, transport could be partially restored by the addition of importin beta, RanBP1, and/or RanGAP1 to the transport reaction. In intact Nup358-depleted cells, overexpression of importin beta strongly stimulated nuclear import, demonstrating that the transport receptor is the most rate-limiting factor at reduced Nup358-concentrations. As an alternative approach, we used antibody-inhibition experiments. Antibodies against RanGAP1 inhibited the enzymatic activity of soluble and nuclear pore-associated RanGAP1, as well as nuclear import and export. Although export could be fully restored by soluble RanGAP, import was only partially rescued. Together, these data suggest a dual function of the Nup358-RanGAP1 complex as a coordinator of importin beta recycling and reformation of novel import complexes.
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Affiliation(s)
- Saskia Hutten
- Department of Biochemistry I, Faculty of Medicine, Georg-August University of Göttingen, 37073, Göttingen, Germany
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23
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Isgro TA, Schulten K. Cse1p-binding dynamics reveal a binding pattern for FG-repeat nucleoporins on transport receptors. Structure 2007; 15:977-91. [PMID: 17698002 DOI: 10.1016/j.str.2007.06.011] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2007] [Revised: 06/26/2007] [Accepted: 06/27/2007] [Indexed: 01/07/2023]
Abstract
Nuclear pore proteins with phenylalanine-glycine repeats are vital to the functional transport of molecules across the nuclear pore complex. The current study investigates the binding of these FG-nucleoporins to the Cse1p:Kap60p:RanGTP nuclear export complex. Fourteen binding spots for FG-nucleoporin peptides are revealed on the surface of Cse1p, and 5 are revealed on the Kap60p surface. Taken together, and along with binding data for two other transport receptors, the data suggest that the ability to bind FG-nucleoporins by itself is not enough to ensure viable nuclear transport. Rather, it is proposed that the density of binding spots on the transport receptor surface is key in determining transport viability. The number of binding spots on the transport receptor surface should be large enough to ensure multiple, simultaneous FG-repeat binding, and their arrangement should be close enough to ensure multiple binding from the same FG-nucleoporin.
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Affiliation(s)
- Timothy A Isgro
- Department of Physics, University of Illinois at Urbana-Champaign, Beckman Institute for Advanced Science and Technology, Urbana, IL 61801, USA
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24
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Waldmann I, Wälde S, Kehlenbach RH. Nuclear import of c-Jun is mediated by multiple transport receptors. J Biol Chem 2007; 282:27685-92. [PMID: 17652081 DOI: 10.1074/jbc.m703301200] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
c-Jun and c-Fos are major components of the transcriptional complex AP-1. Here, we investigate the nuclear import pathway(s) of the transcription factor c-Jun. c-Jun bound specifically to the nuclear import receptors importin beta, transportin, importin 5, importin 7, importin 9, and importin 13. In digitonin-permeabilized cells, importin beta, transportin, importin 7, and importin 9 promoted efficient import of c-Jun into the nucleus. Importin alpha, by contrast, inhibited nuclear import of c-Jun in vitro. A single basic region preceding the leucine zipper of c-Jun functions as a nuclear localization signal (NLS) and was required for interaction with all tested import receptors. In vivo, nuclear import of a c-Jun reporter protein lacking the leucine zipper strictly depended on this NLS. In a leucine zipper-dependent manner, c-Jun with mutations in its NLS was still imported into the nucleus in a complex with endogenous leucine zipper proteins or, for example, with cotransfected c-Fos. Together, these results explain the highly efficient nuclear import of the transcription factor c-Jun.
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Affiliation(s)
- Inga Waldmann
- Universität Göttingen, Zentrum für Biochemie und Molekulare Zellbiologie, Humboldtallee 23, 37073 Göttingen, Germany
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25
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Isgro TA, Schulten K. Association of nuclear pore FG-repeat domains to NTF2 import and export complexes. J Mol Biol 2006; 366:330-45. [PMID: 17161424 DOI: 10.1016/j.jmb.2006.11.048] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2006] [Revised: 11/08/2006] [Accepted: 11/14/2006] [Indexed: 01/12/2023]
Abstract
Transport into and out of the nucleus is regulated by the nuclear pore complex. Vital to this regulation are nuclear pore proteins with FG sequence repeats, which have been shown to be crucial for cell viability and which interact with nuclear transport receptors. Here we use molecular dynamics simulations to investigate the binding of FG-repeat peptides to the surface of NTF2, the Ran importer. The simulations, covering over 254 ns, agree with previous X-ray, mutational, NMR, and computational data in identifying four binding spots. They also serve to provide an all-atom view of binding at each spot, whereas FG-repeat binding has been only directly observed at a single spot. Furthermore, the simulations identify two novel binding spots in addition to the four others. All six binding spots broadly form a stripe across the surface of NTF2. The resulting regularity and proximity of binding spots on the surface may be necessary for identification of the transport receptor by the FG-repeats in the nuclear pore complex and for the successful transit of NTF2 through the pore.
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Affiliation(s)
- Timothy A Isgro
- Department of Physics, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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26
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Yoshimura SH, Takahashi H, Otsuka S, Takeyasu K. Development of glutathione-coupled cantilever for the single-molecule force measurement by scanning force microscopy. FEBS Lett 2006; 580:3961-5. [PMID: 16806198 DOI: 10.1016/j.febslet.2006.06.032] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2006] [Accepted: 06/12/2006] [Indexed: 11/28/2022]
Abstract
The accuracy and the fidelity of a single-molecule force measurement largely rely on how the molecule of interest is attached to the solid substrate surface (bead, cantilever, cover glass and etc.). A site-specific attachment of a protein without affecting its structure and enzymatic function has been a major concern. Here, we established a glutathione-coupled cantilever to which any glutathione S-transferase (GST)-fused proteins can be attached in a desired direction. The rupture force between glutathione and GST was approximately 100 pN on average. By using this cantilever, we succeeded in measuring the interaction force between importin alpha and importin beta.
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Affiliation(s)
- Shige H Yoshimura
- Laboratory of Plasma Membrane and Nuclear Signaling, Graduate School of Biostudies, Kyoto University, Kitashirakawa-oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan.
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27
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Arnold M, Nath A, Wohlwend D, Kehlenbach RH. Transportin is a major nuclear import receptor for c-Fos: a novel mode of cargo interaction. J Biol Chem 2006; 281:5492-9. [PMID: 16407315 DOI: 10.1074/jbc.m513281200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
c-Fos, a component of the transcription factor AP-1, is rapidly imported into the nucleus after translation. We established an in vitro system using digitonin-permeabilized cells to analyze nuclear import of c-Fos in detail. Two import receptors of the importin beta superfamily, importin beta itself and transportin, promote import of c-Fos in vitro. Under conditions where importin beta-dependent transport was blocked, c-Fos still accumulated in the nucleus in the presence of cytosol. Inhibition of the transportin-dependent pathway, in contrast, abolished import of c-Fos. Furthermore, c-Fos mutants that interact with transportin but not with importin beta were efficiently imported in the presence of cytosol. Hence, transportin appears to be the predominant import receptor for c-Fos. A detailed biochemical characterization revealed that the interaction of transportin with c-Fos is distinct from the interaction with its established import cargoes, the M9 sequence of heterogeneous nuclear ribonucleoprotein A1 or the nuclear localization sequence of some basic proteins. Likewise, the binding sites on importin beta for its classic import cargo and for c-Fos can be separated. In summary, c-Fos employs a novel mode of receptor-cargo interaction. Hence, transportin may be as versatile as importin beta in recognizing different nuclear import cargoes.
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Affiliation(s)
- Marc Arnold
- Zentrum für Biochemie und Molekulare Zellbiologie, Universität Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
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28
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Isgro TA, Schulten K. Binding Dynamics of Isolated Nucleoporin Repeat Regions to Importin-β. Structure 2005; 13:1869-79. [PMID: 16338415 DOI: 10.1016/j.str.2005.09.007] [Citation(s) in RCA: 135] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2005] [Revised: 08/31/2005] [Accepted: 09/01/2005] [Indexed: 11/24/2022]
Abstract
The nuclear pore complex, through the interaction of its proteins with transport receptors, controls the transport of large molecules into and out of the cell's nucleus. There is ample evidence for proteins with FG sequence repeats playing an essential role in this control. Previous studies have elucidated binding spots for FG sequence repeats on the surface of the transport receptor importin-beta by X-ray crystallography and mutational studies. Molecular dynamics simulations have been performed to characterize the interaction of FG sequence repeats with the transport receptor. Observed binding spots have been verified and novel sites discovered, suggesting that importin-beta features many more binding spots than suspected so far. The observed binding spots are in accord with several models of nucleocytoplasmic transport, and the large number of binding spots on importin-beta may be necessary for the pore complex to distinguish between importin-beta and inert proteins, and to allow for its passage through the pore.
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Affiliation(s)
- Timothy A Isgro
- Department of Physics, University of Illinois at Urbana-Champaign, Beckman Institute for Advanced Science and Technology, Urbana, Illinois 61801, USA
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29
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Abstract
Importin beta, once thought to be exclusively a nuclear transport receptor, is emerging as a global regulator of diverse cellular functions. Importin beta acts positively in multiple interphase roles: in nuclear import, as a chaperone for highly charged nuclear proteins, and as a potential motor adaptor for movement along microtubules. In contrast, importin beta plays a negative regulatory role in mitotic spindle assembly, centrosome dynamics, nuclear membrane formation, and nuclear pore assembly. In most of these, importin beta is counteracted by its regulator, Ran-GTP. In light of this, the recent discovery of Ran's involvement in spindle checkpoint control suggested a potential new arena for importin beta action, although it is also possible that one of importin beta's relatives, the karyopherin family of proteins, manages this checkpoint. Lastly, importin beta plays a role in transducing damage signals from the axons of injured neurons back to the cell body.
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Affiliation(s)
- Amnon Harel
- Section of Cell and Developmental Biology, Division of Biological Sciences 0347, University of California, San Diego, 9500 Gilman Drive, Room 2124A, Pacific Hall, La Jolla, CA 92093, USA
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30
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Marg A, Shan Y, Meyer T, Meissner T, Brandenburg M, Vinkemeier U. Nucleocytoplasmic shuttling by nucleoporins Nup153 and Nup214 and CRM1-dependent nuclear export control the subcellular distribution of latent Stat1. J Cell Biol 2004; 165:823-33. [PMID: 15210729 PMCID: PMC2172394 DOI: 10.1083/jcb.200403057] [Citation(s) in RCA: 127] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2004] [Accepted: 05/07/2004] [Indexed: 01/02/2023] Open
Abstract
Interferon stimulation of cells leads to the tyrosine phosphorylation of latent Stat1 and subsequent transient accumulation in the nucleus that requires canonical transport factors. However, the mechanisms that control the predominantly cytoplasmic localization in unstimulated cells have not been resolved. We uncovered that constitutive energy- and transport factor-independent nucleocytoplasmic shuttling is a property of unphosphorylated Stat1, Stat3, and Stat5. The NH(2)- and COOH-terminal Stat domains are generally dispensable, whereas alkylation of a single cysteine residue blocked cytokine-independent nuclear translocation and thus implicated the linker domain into the cycling of Stat1. It is revealed that constitutive nucleocytoplasmic shuttling of Stat1 is mediated by direct interactions with the FG repeat regions of nucleoporin 153 and nucleoporin 214 of the nuclear pore. Concurrent active nuclear export by CRM1 created a nucleocytoplasmic Stat1 concentration gradient that is significantly reduced by the blocking of energy-requiring translocation mechanisms or the specific inactivation of CRM1. Thus, we propose that two independent translocation pathways cooperate to determine the steady-state distribution of Stat1.
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Affiliation(s)
- Andreas Marg
- Abteilung Zellulare Signalverarbeitung, Leibniz-Forschungsinstitut fur Molekulare Pharmakologie, Robert-Rossle-Str. 10, 13125 Berlin, Germany
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31
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Suh EK, Gumbiner BM. Translocation of β-catenin into the nucleus independent of interactions with FG-rich nucleoporins. Exp Cell Res 2003; 290:447-56. [PMID: 14568002 DOI: 10.1016/s0014-4827(03)00370-7] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
beta-Catenin nuclear import has been found to be independent of classical nuclear localization signal (NLS) nuclear import factors. Here, we test the hypothesis that beta-catenin interacts directly with nuclear pore proteins to mediate its own transport. We show that beta-catenin, unlike importin-beta, does not interact detectably with Phe/Gly(FG)-repeat-rich nuclear pore proteins or nucleoporins (Nups). Moreover, unlike NLS-containing proteins, beta-catenin nuclear import is not inhibited by wheat germ agglutinin (WGA) or excess importin-beta. These results suggest beta-catenin nuclear translocation does not involve direct interactions with FG-Nups. However, beta-catenin has two regions that can target it to the nucleus, and its import is cold sensitive, indicating that beta-catenin nuclear import is still an active process. Transport is blocked by a soluble form of the C-cadherin cytoplasmic domain, suggesting that masking of the nuclear targeting signal may be a mechanism of regulating beta-catenin subcellular localization.
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Affiliation(s)
- Eun-Kyung Suh
- Neuroscience Program, Weill Graduate School of Medical Sciences of Cornell University, New York, NY 10021, USA
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32
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33
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Bednenko J, Cingolani G, Gerace L. Importin beta contains a COOH-terminal nucleoporin binding region important for nuclear transport. J Cell Biol 2003; 162:391-401. [PMID: 12885761 PMCID: PMC2172684 DOI: 10.1083/jcb.200303085] [Citation(s) in RCA: 118] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Proteins containing a classical NLS are transported into the nucleus by the import receptor importin beta, which binds to cargoes via the adaptor importin alpha. The import complex is translocated through the nuclear pore complex by interactions of importin beta with a series of nucleoporins. Previous studies have defined a nucleoporin binding region in the NH2-terminal half of importin beta. Here we report the identification of a second nucleoporin binding region in its COOH-terminal half. Although the affinity of the COOH-terminal region for nucleoporins is dramatically weaker than that of the NH2-terminal region, sets of mutations that perturb the nucleoporin binding of either region reduce the nuclear import activity of importin beta to a similar extent ( approximately 50%). An importin beta mutant with a combination of mutations in the NH2- and COOH-terminal regions is completely inactive for nuclear import. Thus, importin beta possesses two nucleoporin binding sites, both of which are important for its nuclear import function.
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Affiliation(s)
- Janna Bednenko
- Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
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34
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Bayliss R, Littlewood T, Strawn LA, Wente SR, Stewart M. GLFG and FxFG nucleoporins bind to overlapping sites on importin-beta. J Biol Chem 2002; 277:50597-606. [PMID: 12372823 DOI: 10.1074/jbc.m209037200] [Citation(s) in RCA: 179] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The interaction between nuclear pore proteins (nucleoporins) and transport factors is crucial for the translocation of macromolecules through nuclear pores. Many nucleoporins contain FG sequence repeats, and previous studies have demonstrated interactions between repeats containing FxFG or GLFG cores and transport factors. The crystal structure of residues 1-442 of importin-beta bound to a GLFG peptide indicates that this repeat core binds to the same primary site as FxFG cores. Importin-beta-I178D shows reduced binding to both FxFG and GLFG repeats, consistent with both binding to an overlapping site in the hydrophobic groove between the A-helices of HEAT repeats 5 and 6. Moreover, FxFG repeats can displace importin-beta or its S. cerevisiae homologue, Kap95, bound to GLFG repeats. Addition of soluble GLFG repeats decreases the rate of nuclear protein import in digitonin-permeabilized HeLa cells, indicating that this interaction has a role in the translocation of carrier-cargo complexes through nuclear pores. The binding of GLFG and FxFG repeats to overlapping sites on importin-beta indicates that functional differences between different repeats probably arise from differences in their spatial organization.
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Affiliation(s)
- Richard Bayliss
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, United Kingdom
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35
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Cingolani G, Bednenko J, Gillespie MT, Gerace L. Molecular basis for the recognition of a nonclassical nuclear localization signal by importin beta. Mol Cell 2002; 10:1345-53. [PMID: 12504010 DOI: 10.1016/s1097-2765(02)00727-x] [Citation(s) in RCA: 161] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Nuclear import of proteins containing a classical nuclear localization signal (NLS) involves NLS recognition by importin alpha, which associates with importin beta via the IBB domain. Other proteins, including parathyroid hormone-related protein (PTHrP), are imported into the nucleus by direct interaction with importin beta. We solved the crystal structure of a fragment of importin beta-1 (1-485) bound to the nonclassical NLS of PTHrP. The structure reveals a second extended cargo binding site on importin beta distinct from the IBB domain binding site. Using a permeabilized cell import assay we demonstrate that importin beta (1-485) can import PTHrP-coupled cargo in a Ran-dependent manner. We propose that this region contains a prototypical nuclear import receptor domain, which could have evolved into the modern importin beta superfamily.
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Affiliation(s)
- Gino Cingolani
- Departments of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
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36
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Plafker K, Macara IG. Fluorescence resonance energy transfer biosensors that detect Ran conformational changes and a Ran x GDP-importin-beta -RanBP1 complex in vitro and in intact cells. J Biol Chem 2002; 277:30121-7. [PMID: 12034733 DOI: 10.1074/jbc.m203006200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Ran GTPase plays a central role in nucleocytoplasmic transport. Association of Ran x GTP with transport carriers (karyopherins) triggers the loading/unloading of export or import cargo, respectively. The C-terminal tail of Ran x GTP is deployed in an extended conformation when associated with a Ran binding domain or importins. To monitor tail orientation, a Ran-GFP fusion was labeled with the fluorophore Alexa546. Fluorescence resonance energy transfer (FRET) occurs efficiently between the green fluorescent protein (GFP) and Alexa546 for Ran x GDP and Ran x GTP, suggesting that the tail is tethered in both states. However, Ran x GTP complexes with importin-beta, RanBP1, and Crm1 all show reduced FRET consistent with tail extension. Displacement of the C-terminal tail of Ran by karyopherins may be a general mechanism to facilitate RanBP1 binding. A Ran x GDP-RanBP1-importin-beta complex also displayed a low FRET signal. To detect this complex in vivo, a bipartite biosensor consisting of Ran-Alexa546 plus GST-GFP-RanBP1, was co-injected into the cytoplasm of cells. The Ran redistributed predominantly to the nucleus, and RanBP1 remained cytoplasmic. Nonetheless, a robust cytoplasmic FRET signal was detectable, which suggests that a significant fraction of cytoplasmic Ran.GDP may exist in a ternary complex with RanBP1 and importins.
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Affiliation(s)
- Kendra Plafker
- Center for Cell Signaling and the Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, Virginia 22908-0577, USA
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37
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Kuersten S, Arts GJ, Walther TC, Englmeier L, Mattaj IW. Steady-state nuclear localization of exportin-t involves RanGTP binding and two distinct nuclear pore complex interaction domains. Mol Cell Biol 2002; 22:5708-20. [PMID: 12138183 PMCID: PMC133969 DOI: 10.1128/mcb.22.16.5708-5720.2002] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Vertebrate tRNA export receptor exportin-t (Xpo-t) binds to RanGTP and mature tRNAs cooperatively to form a nuclear export complex. Xpo-t shuttles bidirectionally through nuclear pore complexes (NPCs) but is mainly nuclear at steady state. The steady-state distribution of Xpo-t is shown to depend on its interaction with RanGTP. Two distinct Xpo-t NPC interaction domains that bind differentially to peripherally localized nucleoporins in vitro are identified. The N terminus binds to both Nup153 and RanBP2/Nup358 in a RanGTP-dependent manner, while the C terminus binds to CAN/Nup214 independently of Ran. We propose that these interactions increase the concentration of tRNA export complexes and of empty Xpo-t in the vicinity of NPCs and thus increase the efficiency of the Xpo-t transport cycle.
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Affiliation(s)
- Scott Kuersten
- Gene Expression Programme, European Molecular Biology Laboratory, D-69117 Heidelberg, Germany
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38
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Zhang C, Hutchins JRA, Mühlhäusser P, Kutay U, Clarke PR. Role of importin-beta in the control of nuclear envelope assembly by Ran. Curr Biol 2002; 12:498-502. [PMID: 11909537 DOI: 10.1016/s0960-9822(02)00714-5] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Compartmentalization of the genetic material into a nucleus bounded by a nuclear envelope (NE) is the hallmark of a eukaryotic cell. The control of NE assembly is poorly understood, but in a cell-free system made from Xenopus eggs, NE assembly involves the small GTPase Ran. In this system, Sepharose beads coated with Ran induce the formation of functional NEs in the absence of chromatin. Here, we show that importin-beta, an effector of Ran involved in nucleocytoplasmic transport and mitotic spindle assembly, is required for NE assembly induced by Ran. Concentration of importin-beta on beads is sufficient to induce NE assembly in Xenopus egg extracts. The function of importin-beta in NE assembly is disrupted by a mutation that decreases affinity for nucleoporins containing FxFG repeats. By contrast, a truncated protein that cannot interact with importin-alpha is functional. Thus, importin-beta functions in NE assembly by recruiting FxFG nucleoporins rather than by interaction through importin-alpha with karyophilic proteins carrying classical nuclear localization signals. Importin-beta links NE assembly, mitotic spindle assembly, and nucleocytoplasmic transport to regulation by Ran and may coordinate these processes during cell division.
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Affiliation(s)
- Chuanmao Zhang
- Biomedical Research Centre, Level 5, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, Scotland, United Kingdom
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39
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Abstract
A defining characteristic of eukaryotic cells is the possession of a nuclear envelope. Transport of macromolecules between the nuclear and cytoplasmic compartments occurs through nuclear pore complexes that span the double membrane of this envelope. The molecular basis for transport has been revealed only within the last few years. The transport mechanism lacks motors and pumps and instead operates by a process of facilitated diffusion of soluble carrier proteins, in which vectoriality is provided by compartment-specific assembly and disassembly of cargo-carrier complexes. The carriers recognize localization signals on the cargo and can bind to pore proteins. They also bind a small GTPase, Ran, whose GTP-bound form is predominantly nuclear. Ran-GTP dissociates import carriers from their cargo and promotes the assembly of export carriers with cargo. The ongoing discovery of numerous carriers, Ran-independent transport mechanisms, and cofactors highlights the complexity of the nuclear transport process. Multiple regulatory mechanisms are also being identified that control cargo-carrier interactions. Circadian rhythms, cell cycle, transcription, RNA processing, and signal transduction are all regulated at the level of nucleocytoplasmic transport. This review focuses on recent discoveries in the field, with an emphasis on the carriers and cofactors involved in transport and on possible mechanisms for movement through the nuclear pores.
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Affiliation(s)
- I G Macara
- Center for Cell Signaling, University of Virginia, Charlottesville, Virginia 22908-0577, USA.
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40
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Bera TK, Bera J, Brinkmann U, Tessarollo L, Pastan I. Cse1l is essential for early embryonic growth and development. Mol Cell Biol 2001; 21:7020-4. [PMID: 11564884 PMCID: PMC99877 DOI: 10.1128/mcb.21.20.7020-7024.2001] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The CSE1L gene, the human homologue of the yeast chromosome segregation gene CSE1, is a nuclear transport factor that plays a role in proliferation as well as in apoptosis. CSE1 and CSE1L are essential genes in Saccharomyces cerevisiae and mammalian cells, as shown by conditional yeast mutants and mammalian cell culture experiments with antisense-mediated depletion of CSE1L. To analyze whether CSE1L is also essential in vivo and whether its absence can be compensated for by other genes or mechanisms, we have cloned the murine CSE1L gene (Cse1l) and analyzed its tissue- and development-specific expression: Cse1l was detected at embryonic day 7.0 (E7.0), E11.0, E15.0, and E17.0, and in adults, high expression was observed in proliferating tissues. Subsequently, we inactivated the Cse1l gene in embryonic stem cells to generate heterozygous and homozygous knockout mice. Mice heterozygous for Cse1l appear normal and are fertile. However, no homozygous pups were born after interbreeding of heterozygous mice. In 30 heterozygote interbreeding experiments, 50 Cse1l wild-type mice and 100 heterozygotes were born but no animal with both Cse1l alleles deleted was born. Embryo analyses showed that homozygous mutant embryos were already disorganized and degenerated by E5.5. This implicates with high significance (P < 0.0001, Pearson chi-square test) an embryonically lethal phenotype of homozygous murine CSE1 deficiency and suggests that Cse1l plays a critical role in early embryonic development.
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Affiliation(s)
- T K Bera
- Laboratory of Molecular Biology, Clinical Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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41
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Geles KG, Adam SA. Germline and developmental roles of the nuclear transport factor importin (α)3 in C. elegans. Development 2001; 128:1817-30. [PMID: 11311162 DOI: 10.1242/dev.128.10.1817] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The importin (α) family of transport factors mediates the nuclear import of classical nuclear localization signal-containing proteins. In order to understand how multiple importin (α) proteins are regulated both in individual cells and in a whole organism, the three importin (α) (ima) genes of Caenorhabditis elegans have been identified and studied. All three IMAs are expressed in the germline; however, only IMA-3 is expressed in the soma. RNA interference (RNAi) experiments demonstrate that IMA-3 is required for the progression of meiotic prophase I during oocyte development. Loss of IMA-3 expression leads also to a disruption of the nuclear pore complex accompanied by the mis-localization of P granules. A range of defects occurring in ima-3(RNAi) F(1) progeny further supports a role for IMA-3 during embryonic and larval development. The functional association of IMA-3 with distinct cellular events, its expression pattern and intracellular localization indicate that regulation of the nuclear transport machinery is involved in the control of developmental pathways.
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Affiliation(s)
- K G Geles
- Department of Cell and Molecular Biology and the Robert H. Lurie Comprehensive Cancer Center, Northwestern University Medical School, Chicago, IL 60611, USA.
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42
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Ferrando-May E, Cordes V, Biller-Ckovric I, Mirkovic J, Görlich D, Nicotera P. Caspases mediate nucleoporin cleavage, but not early redistribution of nuclear transport factors and modulation of nuclear permeability in apoptosis. Cell Death Differ 2001; 8:495-505. [PMID: 11423910 DOI: 10.1038/sj.cdd.4400837] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2000] [Revised: 12/22/2000] [Accepted: 12/29/2000] [Indexed: 11/08/2022] Open
Abstract
In eukaryotic cells, both soluble transport factors and components of the nuclear pore complex mediate protein and RNA trafficking between the nucleus and the cytoplasm. Here, we investigated whether caspases, the major execution system in apoptosis, target the nuclear pore or components of the nuclear transport machinery. Four nucleoporins, Nup153, RanBP2, Nup214 and Tpr are cleaved by caspases during apoptosis. In contrast, the nuclear transport factors, Ran, importin alpha and importin beta are not proteolytically processed, but redistribute across the nuclear envelope independently and prior to caspase activation. Also, mRNA accumulates into the nucleus before caspases become active. Microinjection experiments further revealed that early in apoptosis, the nucleus becomes permeable to dextran molecules of 70 kD molecular weight. Redistribution of import factors and mRNA, as well as nuclear permeabilisation, occur prior to caspase-mediated nucleoporin cleavage. Our findings suggest that the apoptotic programme includes modifications in the machinery responsible for nucleocytoplasmic transport, which are independent from caspase-mediated degradation of nuclear proteins.
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Affiliation(s)
- E Ferrando-May
- Chair of Molecular Toxicology, Department of Biology, University of Konstanz, 78457 Konstanz, Germany
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43
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Ben-Efraim I, Gerace L. Gradient of increasing affinity of importin beta for nucleoporins along the pathway of nuclear import. J Cell Biol 2001; 152:411-7. [PMID: 11266456 PMCID: PMC2199621 DOI: 10.1083/jcb.152.2.411] [Citation(s) in RCA: 230] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Nuclear import and export signals on macromolecules mediate directional, receptor-driven transport through the nuclear pore complex (NPC) by a process that is suggested to involve the sequential binding of transport complexes to different nucleoporins. The directionality of transport appears to be partly determined by the nucleocytoplasmic compartmentalization of components of the Ran GTPase system. We have analyzed whether the asymmetric localization of discrete nucleoporins can also contribute to transport directionality. To this end, we have used quantitative solid phase binding analysis to determine the affinity of an importin beta cargo complex for Nup358, the Nup62 complex, and Nup153, which are in the cytoplasmic, central, and nucleoplasmic regions of the NPC, respectively. These nucleoporins are proposed to provide progressively more distal binding sites for importin beta during import. Our results indicate that the importin beta transport complex binds to nucleoporins with progressively increasing affinity as the complex moves from Nup358 to the Nup62 complex and to Nup153. Antibody inhibition studies support the possibility that importin beta moves from Nup358 to Nup153 via the Nup62 complex during import. These results indicate that nucleoporins themselves, as well as the nucleocytoplasmic compartmentalization of the Ran system, are likely to play an important role in conferring directionality to nuclear protein import.
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Affiliation(s)
- Iris Ben-Efraim
- Department of Cell Biology and Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037
| | - Larry Gerace
- Department of Cell Biology and Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037
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44
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Abstract
SUMMARY In recent years, our understanding of macromolecular transport processes across the nuclear envelope has grown dramatically, and a large number of soluble transport receptors mediating either nuclear import or nuclear export have been identified. Most of these receptors belong to one large family of proteins, all of which share homology with the protein import receptor importin beta (also named karyopherin beta). Members of this family have been classified as importins or exportins on the basis of the direction they carry their cargo. To date, the family includes 14 members in the yeast Saccharomyces cerevisiae and at least 22 members in humans. Importins and exportins are regulated by the small GTPase Ran, which is thought to be highly enriched in the nucleus in its GTP-bound form. Importins recognize their substrates in the cytoplasm and transport them through nuclear pores into the nucleus. In the nucleoplasm, RanGTP binds to importins, inducing the release of import cargoes. In contrast, exportins interact with their substrates only in the nucleus in the presence of RanGTP and release them after GTP hydrolysis in the cytoplasm, causing disassembly of the export complex. Thus, common features of all importin-beta-like transport factors are their ability to shuttle between the nucleus and the cytoplasm, their interaction with RanGTP as well as their ability to recognize specific transport substrates.
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Affiliation(s)
- Anne-Christine Ström
- Department of Molecular and Cellular Biology, University of California, Berkeley, CA 94720-3200, USA
| | - Karsten Weis
- Department of Molecular and Cellular Biology, University of California, Berkeley, CA 94720-3200, USA
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45
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Abstract
Importins are members of a family of transport receptors (karyopherins) that mediate the nucleocytoplasmic transport of protein and RNA cargoes. We identified importin-11 as a potential new human member of this family, on the basis of limited similarity to the Saccharomyces cerevisiae protein, Lph2p, and cloned the complete open reading frame. Importin-11 interacts with the Ran GTPase, and constitutively shuttles between the nuclear and cytoplasmic compartments. A yeast dihybrid screen identified UbcM2, an E2-type ubiquitin-conjugating enzyme, as a binding partner and potential transport cargo for importin-11. Importin-11 and UbcM2 interact directly, and the complex is disassembled by Ran:GTP but not by Ran:GDP. UbcM2 is constitutively nuclear and shuttles between the nuclear and cytoplasmic compartments. Nuclear import of UbcM2 requires Ran and importin-11, and is inhibited by wheatgerm agglutinin, energy depletion or dominant interfering mutants of Ran and importin-beta. These data establish importin-11 as a new member of the karyopherin family of transport receptors, and identify UbcM2 as a nuclear member of the E2 ubiquitin-conjugating enzyme family.
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Affiliation(s)
- S M Plafker
- Center for Cell Signaling, Box 800577, HSC and Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA.
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46
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Bayliss R, Kent HM, Corbett AH, Stewart M. Crystallization and initial X-ray diffraction characterization of complexes of FxFG nucleoporin repeats with nuclear transport factors. J Struct Biol 2000; 131:240-7. [PMID: 11052897 DOI: 10.1006/jsbi.2000.4297] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
NTF2 and importin-beta are transport factors that mediate nuclear protein import and which interact with nuclear pore proteins (nucleoporins) during translocation from the cytoplasm to the nucleus through nuclear pore complexes. We employed a native gel electrophoresis method to assess the interaction of nucleoporin constructs that contain FxFG sequence repeats with NTF2 and truncation mutants of importin-beta to determine suitable fragments for crystallization. Based on these data, we obtained crystals of complexes between yeast NTF2 and a construct containing five FxFG nucleoporin repeats from the yeast nucleoporin Nsp1p and between a construct containing residues 1-442 of human importin-beta and the same nucleoporin construct. The yeast NTF2-nucleoporin crystals have trigonal symmetry and diffract past 2.8 A resolution using synchrotron radiation, whereas the importin-beta-nucleoporin complex crystals have P2(1)2(1)2 orthorhombic symmetry and diffract past 3.2 A resolution.
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Affiliation(s)
- R Bayliss
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, England
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Hood JK, Silver PA. Diverse nuclear transport pathways regulate cell proliferation and oncogenesis. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1471:M31-41. [PMID: 10967423 DOI: 10.1016/s0304-419x(00)00018-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- J K Hood
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School and the Dana-Farber Cancer Institute, 44 Binney Street, 02115, Boston, MA, USA
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Bayliss R, Littlewood T, Stewart M. Structural basis for the interaction between FxFG nucleoporin repeats and importin-beta in nuclear trafficking. Cell 2000; 102:99-108. [PMID: 10929717 DOI: 10.1016/s0092-8674(00)00014-3] [Citation(s) in RCA: 367] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
We describe the crystal structure of a complex between importin-beta residues 1-442 (Ib442) and five FxFG nucleoporin repeats from Nsp1p. Nucleoporin FxFG cores bind on the convex face of Ib442 to a primary site between the A helices of HEAT repeats 5 and 6, and to a secondary site between HEAT repeats 6 and 7. Mutations at importin-beta Ile178 in the primary FxFG binding site reduce both binding and nuclear protein import, providing direct evidence for the functional significance of the importin-beta-FxFG interaction. The FxFG binding sites on importin-beta do not overlap with the RanGTP binding site. Instead, RanGTP may release importin-beta from FxFG nucleoporins by generating a conformational change that alters the structure of the FxFG binding site.
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Affiliation(s)
- R Bayliss
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
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Bayliss R, Corbett AH, Stewart M. The molecular mechanism of transport of macromolecules through nuclear pore complexes. Traffic 2000; 1:448-56. [PMID: 11208130 DOI: 10.1034/j.1600-0854.2000.010602.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Trafficking of macromolecules between nuclear and cytoplasmic compartments takes place through the nuclear pore complexes (NPCs) of the nuclear envelope. Nuclear trafficking involves a complex series of interactions between cargo, soluble transport factors (carriers) and nuclear pore proteins (nucleoporins) that are orchestrated by the Ras-family GTPase Ran. The primary role of Ran is probably to establish directionality and to sort molecules to be transported by controlling the interaction between carriers and cargoes, so that they bind in one compartment but dissociate in the other. Translocation of carriers and cargo-carrier complexes through NPCs requires interactions between the carriers and nucleoporins that contain distinctive tandem sequence repeats based on cores rich in glycine and phenylalanine residues that are separated by hydrophilic linkers. Much recent work has focused on these interactions and, in particular, their specificity, regulation and function. Evidence is accumulating that carriers move through the NPC by distinct but overlapping routes using specific subsets of nucleoporins.
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Affiliation(s)
- R Bayliss
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK
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Petersen C, Orem N, Trueheart J, Thorner JW, Macara IG. Random mutagenesis and functional analysis of the Ran-binding protein, RanBP1. J Biol Chem 2000; 275:4081-91. [PMID: 10660567 DOI: 10.1074/jbc.275.6.4081] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ran GTPase is required for nucleocytoplasmic transport of many types of cargo. Several proteins that recognize Ran in its GTP-bound state (Ran x GTP) possess a conserved Ran-binding domain (RanBD). Ran-binding protein-1 (RanBP1) has a single RanBD and is required for RanGAP-mediated GTP hydrolysis and release of Ran from nuclear transport receptors (karyopherins). In budding yeast (Saccharomyces cerevisiae), RanBP1 is encoded by the essential YRB1 gene; expression of mouse RanBP1 cDNA rescues the lethality of Yrb1-deficient cells. We generated libraries of mouse RanBP1 mutants and examined 11 mutants in vitro and for their ability to complement a temperature-sensitive yrb1 mutant (yrb1-51(ts)) in vivo. In 9 of the mutants, the alteration was a change in a residue (or 2 residues) that is conserved in all known RanBDs. However, 4 of these 9 mutants displayed biochemical properties indistinguishable from that of wild-type RanBP1. These mutants bound to Ran x GTP, stimulated RanGAP, inhibited the exchange activity of RCC1, and rescued growth of the yrb1-51(ts) yeast cells. Two of the 9 mutants altered in residues thought to be essential for interaction with Ran were unable to rescue growth of the yrb1(ts) mutant and did not bind detectably to Ran in vitro. However, one of these 2 mutants (and 2 others that were crippled in other RanBP1 functions) retained some ability to co-activate RanGAP. A truncated form of RanBP1 (lacking its nuclear export signal) was able to complement the yrb1(ts) mutation. When driven from the YRB1 promoter, 4 of the 5 mutants most impaired for Ran binding were unable to rescue growth of the yrb1(ts) cells; remarkably, these mutants could nevertheless form ternary complexes with importin-5 or importin-beta and Ran-GTP. The same mutants stimulated only inefficiently RanGAP-mediated GTP hydrolysis of the Ran x GTP x importin-5 complex. Thus, the essential biological activity of RanBP1 in budding yeast correlates not with Ran x GTP binding per se or with the ability to form ternary complexes with karyopherins, but with the capacity to potentiate RanGAP activity toward GTP-bound Ran in these complexes.
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Affiliation(s)
- C Petersen
- Center for Cell Signaling, University of Virginia, Charlottesville, Virginia 22908, USA
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