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Bin JM, Suminaite D, Benito-Kwiecinski SK, Kegel L, Rubio-Brotons M, Early JJ, Soong D, Livesey MR, Poole RJ, Lyons DA. Importin 13-dependent axon diameter growth regulates conduction speeds along myelinated CNS axons. Nat Commun 2024; 15:1790. [PMID: 38413580 PMCID: PMC10899189 DOI: 10.1038/s41467-024-45908-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Accepted: 02/06/2024] [Indexed: 02/29/2024] Open
Abstract
Axon diameter influences the conduction properties of myelinated axons, both directly, and indirectly through effects on myelin. However, we have limited understanding of mechanisms controlling axon diameter growth in the central nervous system, preventing systematic dissection of how manipulating diameter affects myelination and conduction along individual axons. Here we establish zebrafish to study axon diameter. We find that importin 13b is required for axon diameter growth, but does not affect cell body size or axon length. Using neuron-specific ipo13b mutants, we assess how reduced axon diameter affects myelination and conduction, and find no changes to myelin thickness, precision of action potential propagation, or ability to sustain high frequency firing. However, increases in conduction speed that occur along single myelinated axons with development are tightly linked to their growth in diameter. This suggests that axon diameter growth is a major driver of increases in conduction speeds along myelinated axons over time.
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Affiliation(s)
- Jenea M Bin
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH16 4SB, UK.
| | - Daumante Suminaite
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH16 4SB, UK
| | | | - Linde Kegel
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH16 4SB, UK
| | - Maria Rubio-Brotons
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH16 4SB, UK
| | - Jason J Early
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH16 4SB, UK
| | - Daniel Soong
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH16 4SB, UK
| | - Matthew R Livesey
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH16 4SB, UK
- Sheffield Institute for Translational Neuroscience, University of Sheffield, Sheffield, S10 2HQ, UK
- Neuroscience Institute, University of Sheffield, Sheffield, S10 2TN, UK
| | - Richard J Poole
- Department of Cell and Developmental Biology, University College London, London, WC1E 6BT, UK
| | - David A Lyons
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH16 4SB, UK.
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2
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Khalil B, Linsenmeier M, Smith CL, Shorter J, Rossoll W. Nuclear-import receptors as gatekeepers of pathological phase transitions in ALS/FTD. Mol Neurodegener 2024; 19:8. [PMID: 38254150 PMCID: PMC10804745 DOI: 10.1186/s13024-023-00698-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Accepted: 12/13/2023] [Indexed: 01/24/2024] Open
Abstract
Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are fatal neurodegenerative disorders on a disease spectrum that are characterized by the cytoplasmic mislocalization and aberrant phase transitions of prion-like RNA-binding proteins (RBPs). The common accumulation of TAR DNA-binding protein-43 (TDP-43), fused in sarcoma (FUS), and other nuclear RBPs in detergent-insoluble aggregates in the cytoplasm of degenerating neurons in ALS/FTD is connected to nuclear pore dysfunction and other defects in the nucleocytoplasmic transport machinery. Recent advances suggest that beyond their canonical role in the nuclear import of protein cargoes, nuclear-import receptors (NIRs) can prevent and reverse aberrant phase transitions of TDP-43, FUS, and related prion-like RBPs and restore their nuclear localization and function. Here, we showcase the NIR family and how they recognize cargo, drive nuclear import, and chaperone prion-like RBPs linked to ALS/FTD. We also discuss the promise of enhancing NIR levels and developing potentiated NIR variants as therapeutic strategies for ALS/FTD and related neurodegenerative proteinopathies.
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Affiliation(s)
- Bilal Khalil
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, 32224, U.S.A
| | - Miriam Linsenmeier
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, U.S.A
| | - Courtney L Smith
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, 32224, U.S.A
- Mayo Clinic Graduate School of Biomedical Sciences, Neuroscience Track, Mayo Clinic, Jacksonville, FL, 32224, U.S.A
| | - James Shorter
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, U.S.A..
| | - Wilfried Rossoll
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, 32224, U.S.A..
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Yang Y, Guo L, Chen L, Gong B, Jia D, Sun Q. Nuclear transport proteins: structure, function, and disease relevance. Signal Transduct Target Ther 2023; 8:425. [PMID: 37945593 PMCID: PMC10636164 DOI: 10.1038/s41392-023-01649-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2023] [Revised: 09/13/2023] [Accepted: 09/14/2023] [Indexed: 11/12/2023] Open
Abstract
Proper subcellular localization is crucial for the functioning of biomacromolecules, including proteins and RNAs. Nuclear transport is a fundamental cellular process that regulates the localization of many macromolecules within the nuclear or cytoplasmic compartments. In humans, approximately 60 proteins are involved in nuclear transport, including nucleoporins that form membrane-embedded nuclear pore complexes, karyopherins that transport cargoes through these complexes, and Ran system proteins that ensure directed and rapid transport. Many of these nuclear transport proteins play additional and essential roles in mitosis, biomolecular condensation, and gene transcription. Dysregulation of nuclear transport is linked to major human diseases such as cancer, neurodegenerative diseases, and viral infections. Selinexor (KPT-330), an inhibitor targeting the nuclear export factor XPO1 (also known as CRM1), was approved in 2019 to treat two types of blood cancers, and dozens of clinical trials of are ongoing. This review summarizes approximately three decades of research data in this field but focuses on the structure and function of individual nuclear transport proteins from recent studies, providing a cutting-edge and holistic view on the role of nuclear transport proteins in health and disease. In-depth knowledge of this rapidly evolving field has the potential to bring new insights into fundamental biology, pathogenic mechanisms, and therapeutic approaches.
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Affiliation(s)
- Yang Yang
- Department of Pulmonary and Critical Care Medicine, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
| | - Lu Guo
- Department of Pulmonary and Critical Care Medicine, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
| | - Lin Chen
- Department of Pulmonary and Critical Care Medicine, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
| | - Bo Gong
- The Key Laboratory for Human Disease Gene Study of Sichuan Province and Department of Laboratory Medicine, Sichuan Academy of Medical Sciences & Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, China
- Research Unit for Blindness Prevention of Chinese Academy of Medical Sciences (2019RU026), Sichuan Academy of Medical Sciences & Sichuan Provincial People's Hospital, Chengdu, China
| | - Da Jia
- Key Laboratory of Birth Defects and Related Diseases of Women and Children, Department of Pediatrics, West China Second University Hospital, State Key Laboratory of Biotherapy, Sichuan University, Chengdu, China.
| | - Qingxiang Sun
- Department of Pulmonary and Critical Care Medicine, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China.
- Department of Pathology, State Key Laboratory of Biotherapy and Cancer Centre, West China Hospital, Sichuan University, and Collaborative Innovation Centre of Biotherapy, Chengdu, China.
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4
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Steiner A, Favre S, Mack M, Hausharter A, Pillet B, Hafner J, Mitterer V, Kressler D, Pertschy B, Zierler I. Dissecting the Nuclear Import of the Ribosomal Protein Rps2 (uS5). Biomolecules 2023; 13:1127. [PMID: 37509163 PMCID: PMC10377357 DOI: 10.3390/biom13071127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 07/06/2023] [Accepted: 07/12/2023] [Indexed: 07/30/2023] Open
Abstract
The ribosome is assembled in a complex process mainly taking place in the nucleus. Consequently, newly synthesized ribosomal proteins have to travel from the cytoplasm into the nucleus, where they are incorporated into nascent ribosomal subunits. In this study, we set out to investigate the mechanism mediating nuclear import of the small subunit ribosomal protein Rps2. We demonstrate that an internal region in Rps2, ranging from amino acids 76 to 145, is sufficient to target a 3xyEGFP reporter to the nucleus. The importin-β Pse1 interacts with this Rps2 region and is involved in its import, with Rps2 residues arginine 95, arginine 97, and lysine 99 being important determinants for both Pse1 binding and nuclear localization. Moreover, our data reveal a second import mechanism involving the N-terminal region of Rps2, which depends on the presence of basic residues within amino acids 10 to 28. This Rps2 segment overlaps with the binding site of the dedicated chaperone Tsr4; however, the nuclear import of Rps2 via the internal as well as the N-terminal nuclear-targeting element does not depend on Tsr4. Taken together, our study has unveiled hitherto undescribed nuclear import signals, showcasing the versatility of the mechanisms coordinating the nuclear import of ribosomal proteins.
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Affiliation(s)
- Andreas Steiner
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50, 8010 Graz, Austria; (A.S.); (M.M.); (V.M.)
- BioTechMed-Graz, Mozartgasse 12/II, 8010 Graz, Austria
| | - Sébastien Favre
- Unit of Biochemistry, Department of Biology, University of Fribourg, Chemin du Musée 10, 1700 Fribourg, Switzerland; (S.F.); (B.P.); (D.K.)
| | - Maximilian Mack
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50, 8010 Graz, Austria; (A.S.); (M.M.); (V.M.)
- BioTechMed-Graz, Mozartgasse 12/II, 8010 Graz, Austria
| | - Annika Hausharter
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50, 8010 Graz, Austria; (A.S.); (M.M.); (V.M.)
| | - Benjamin Pillet
- Unit of Biochemistry, Department of Biology, University of Fribourg, Chemin du Musée 10, 1700 Fribourg, Switzerland; (S.F.); (B.P.); (D.K.)
| | - Jutta Hafner
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50, 8010 Graz, Austria; (A.S.); (M.M.); (V.M.)
- BioTechMed-Graz, Mozartgasse 12/II, 8010 Graz, Austria
| | - Valentin Mitterer
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50, 8010 Graz, Austria; (A.S.); (M.M.); (V.M.)
- BioTechMed-Graz, Mozartgasse 12/II, 8010 Graz, Austria
| | - Dieter Kressler
- Unit of Biochemistry, Department of Biology, University of Fribourg, Chemin du Musée 10, 1700 Fribourg, Switzerland; (S.F.); (B.P.); (D.K.)
| | - Brigitte Pertschy
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50, 8010 Graz, Austria; (A.S.); (M.M.); (V.M.)
- BioTechMed-Graz, Mozartgasse 12/II, 8010 Graz, Austria
| | - Ingrid Zierler
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50, 8010 Graz, Austria; (A.S.); (M.M.); (V.M.)
- BioTechMed-Graz, Mozartgasse 12/II, 8010 Graz, Austria
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5
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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6
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Ye Y, Lv C, Sun J, Lin Z, Liu Y, Huang Y, Chen Y, Li H, Lian X, Jiang X, Zhang S, Wang S. XPO1-Mediated EIF1AX Cytoplasmic Relocation Promotes Tumor Migration and Invasion in Endometrial Carcinoma. Oxid Med Cell Longev 2022; 2022:1361135. [PMID: 36589683 DOI: 10.1155/2022/1361135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/31/2022] [Revised: 10/30/2022] [Accepted: 12/01/2022] [Indexed: 12/24/2022]
Abstract
Dysregulation of eukaryotic translation initiation factor 1A, X-linked (EIF1AX), has been implicated in the pathogenesis of some cancers. However, the role of EIF1AX in endometrial carcinoma (EC) remains unknown. We investigated the EIF1AX expression in EC patients and assessed its tumorigenesis-associated function and nucleocytoplasmic transport mechanism in vitro and in vivo. The results indicated that the cytoplasmic EIF1AX expression showed a gradual increase when going from endometrium normal tissue, simple endometrial hyperplasia, complex endometrial hyperplasia, and endometrial atypical hyperplasia to EC, while vice versa for the nuclear EIF1AX expression. In addition, the cytoplasmic EIF1AX expression was positively correlated with histologic type, high International Federation of Gynecology and Obstetrics (FIGO) grade, advanced FIGO stage, deeper infiltration, high Ki67 index, and shorter recurrence-free survival in EC patients. In vitro, short hairpin RNA-mediated EIF1AX depletion or SV40NLS-mediated EIF1AX import into the nucleus in multiple human EC cells potently suppressed cell migration and invasion, epithelial-mesenchymal transition, and lung metastasis. Moreover, exportin 1 induced the transport of EIF1AX from the nucleus to the cytoplasm that could be inhibited by leptomycin B treatment or the mutation in the EIF1AX location sequence. These results demonstrate that cytoplasmic EIF1AX may play a key role in the incidence and promotion of EC, and thus, targeting EIF1AX or its nucleocytoplasmic transport process may offer an effective new therapeutic approach to EC.
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7
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Damizia M, Altieri L, Lavia P. Non-transport roles of nuclear import receptors: In need of the right balance. Front Cell Dev Biol 2022; 10:1041938. [PMID: 36438555 PMCID: PMC9686011 DOI: 10.3389/fcell.2022.1041938] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2022] [Accepted: 10/21/2022] [Indexed: 11/12/2023] Open
Abstract
Nuclear import receptors ensure the recognition and transport of proteins across the nuclear envelope into the nucleus. In addition, as diverse processes as mitosis, post-translational modifications at mitotic exit, ciliogenesis, and phase separation, all share a common need for regulation by nuclear import receptors - particularly importin beta-1 and importin beta-2/transportin - independent on nuclear import. In particular, 1) nuclear import receptors regulate the mitotic spindle after nuclear envelope breakdown, 2) they shield cargoes from unscheduled ubiquitination, regulating their timely proteolysis; 3) they regulate ciliary factors, crucial to cell communications and tissue architecture during development; and 4) they prevent phase separation of toxic proteins aggregates in neurons. The balance of nuclear import receptors to cargoes is critical in all these processes, albeit in opposite directions: overexpression of import receptors, as often found in cancer, inhibits cargoes and impairs downstream processes, motivating the therapeutic design of specific inhibitors. On the contrary, elevated expression is beneficial in neuronal contexts, where nuclear import receptors are regarded as potential therapeutic tools in counteracting the formation of aggregates that may cause neurodegeneration. This paradox demonstrates the amplitude of nuclear import receptors-dependent functions in different contexts and adds complexity in considering their therapeutic implications.
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Affiliation(s)
- Michela Damizia
- Department of Cellular, Computational and Integrated Biology (CIBIO), University of Trento, Trento, Italy
| | - Ludovica Altieri
- Institute of Molecular Biology and Pathology (IBPM), CNR National Research Council of Italy, Sapienza University of Rome, Rome, Italy
- Department of Biology and Biotechnology “Charles Darwin”, Sapienza University of Rome, Rome, Italy
| | - Patrizia Lavia
- Institute of Molecular Biology and Pathology (IBPM), CNR National Research Council of Italy, Sapienza University of Rome, Rome, Italy
- Department of Biology and Biotechnology “Charles Darwin”, Sapienza University of Rome, Rome, Italy
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8
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Gajewska KA, Haynes JM, Jans DA. Nuclear Transporter IPO13 Is Central to Efficient Neuronal Differentiation. Cells 2022; 11:1904. [PMID: 35741036 DOI: 10.3390/cells11121904] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2022] [Revised: 05/28/2022] [Accepted: 06/02/2022] [Indexed: 11/16/2022] Open
Abstract
Molecular transport between the nucleus and cytoplasm of the cell is mediated by the importin superfamily of transport receptors, of which the bidirectional transporter Importin 13 (IPO13) is a unique member, with a critical role in early embryonic development through nuclear transport of key regulators, such as transcription factors Pax6, Pax3, and ARX. Here, we examined the role of IPO13 in neuronal differentiation for the first time, using a mouse embryonic stem cell (ESC) model and a monolayer-based differentiation protocol to compare IPO13−/− to wild type ESCs. Although IPO13−/− ESCs differentiated into neural progenitor cells, as indicated by the expression of dorsal forebrain progenitor markers, reduced expression of progenitor markers Pax6 and Nestin compared to IPO13−/− was evident, concomitant with reduced nuclear localisation/transcriptional function of IPO13 import cargo Pax6. Differentiation of IPO13−/− cells into neurons appeared to be strongly impaired, as evidenced by altered morphology, reduced expression of key neuronal markers, and altered response to the neurotransmitter glutamate. Our findings establish that IPO13 has a key role in ESC neuronal differentiation, in part through the nuclear transport of Pax6.
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Abstract
Efficient and regulated nucleocytoplasmic trafficking of macromolecules to the correct subcellular compartment is critical for proper functions of the eukaryotic cell. The majority of the macromolecular traffic across the nuclear pores is mediated by the Karyopherin-β (or Kap) family of nuclear transport receptors. Work over more than two decades has shed considerable light on how the different Kap family members bring their respective cargoes into the nucleus or the cytoplasm in efficient and highly regulated manners. In this Review, we overview the main features and established functions of Kap family members, describe how Kaps recognize their cargoes and discuss the different ways in which these Kap-cargo interactions can be regulated, highlighting new findings and open questions. We also describe current knowledge of the import and export of the components of three large gene expression machines - the core replisome, RNA polymerase II and the ribosome - pointing out the questions that persist about how such large macromolecular complexes are trafficked to serve their function in a designated subcellular location.
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10
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Gajewska KA, Lescesen H, Ramialison M, Wagstaff KM, Jans DA. Nuclear transporter Importin-13 plays a key role in the oxidative stress transcriptional response. Nat Commun 2021; 12:5904. [PMID: 34625540 PMCID: PMC8501021 DOI: 10.1038/s41467-021-26125-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Accepted: 09/06/2021] [Indexed: 02/08/2023] Open
Abstract
The importin superfamily member Importin-13 is a bidirectional nuclear transporter. To delineate its functional roles, we performed transcriptomic analysis on wild-type and Importin-13-knockout mouse embryonic stem cells, revealing enrichment of differentially expressed genes involved in stress responses and apoptosis regulation. De novo promoter motif analysis on 277 Importin-13-dependent genes responsive to oxidative stress revealed an enrichment of motifs aligned to consensus sites for the transcription factors specificity protein 1, SP1, or Kruppel like factor 4, KLF4. Analysis of embryonic stem cells subjected to oxidative stress revealed that Importin-13-knockout cells were more resistant, with knockdown of SP1 or KLF4 helping protect wild-type embryonic stem cells against stress-induced death. Importin-13 was revealed to bind to SP1 and KLF4 in a cellular context, with a key role in oxidative stress-dependent nuclear export of both transcription factors. The results are integral to understanding stress biology, highlighting the importance of Importin-13 in the stress response.
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Affiliation(s)
- K. A. Gajewska
- grid.1002.30000 0004 1936 7857Biomedicine Discovery Institute, Monash University, Clayton, VIC Australia
| | - H. Lescesen
- grid.1002.30000 0004 1936 7857Biomedicine Discovery Institute, Monash University, Clayton, VIC Australia
| | - M. Ramialison
- grid.1002.30000 0004 1936 7857Australian Regenerative Medicine Institute and Systems Biology Institute, Monash University, Clayton, VIC Australia
| | - K. M. Wagstaff
- grid.1002.30000 0004 1936 7857Biomedicine Discovery Institute, Monash University, Clayton, VIC Australia
| | - D. A. Jans
- grid.1002.30000 0004 1936 7857Biomedicine Discovery Institute, Monash University, Clayton, VIC Australia
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11
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Harrison AR, David CT, Rawlinson SM, Moseley GW. The Ebola Virus Interferon Antagonist VP24 Undergoes Active Nucleocytoplasmic Trafficking. Viruses 2021; 13:v13081650. [PMID: 34452514 PMCID: PMC8402725 DOI: 10.3390/v13081650] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 08/13/2021] [Accepted: 08/17/2021] [Indexed: 12/25/2022] Open
Abstract
Viral interferon (IFN) antagonist proteins mediate evasion of IFN-mediated innate immunity and are often multifunctional, with distinct roles in viral replication. The Ebola virus IFN antagonist VP24 mediates nucleocapsid assembly, and inhibits IFN-activated signaling by preventing nuclear import of STAT1 via competitive binding to nuclear import receptors (karyopherins). Proteins of many viruses, including viruses with cytoplasmic replication cycles, interact with nuclear trafficking machinery to undergo nucleocytoplasmic transport, with key roles in pathogenesis; however, despite established karyopherin interaction, potential nuclear trafficking of VP24 has not been investigated. We find that inhibition of nuclear export pathways or overexpression of VP24-binding karyopherin results in nuclear localization of VP24. Molecular mapping indicates that cytoplasmic localization of VP24 depends on a CRM1-dependent nuclear export sequence at the VP24 C-terminus. Nuclear export is not required for STAT1 antagonism, consistent with competitive karyopherin binding being the principal antagonistic mechanism, while export mediates return of nuclear VP24 to the cytoplasm where replication/nucleocapsid assembly occurs.
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Kimura M, Imai K, Morinaka Y, Hosono-Sakuma Y, Horton P, Imamoto N. Distinct mutations in importin-β family nucleocytoplasmic transport receptors transportin-SR and importin-13 affect specific cargo binding. Sci Rep 2021; 11:15649. [PMID: 34341383 DOI: 10.1038/s41598-021-94948-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Accepted: 07/20/2021] [Indexed: 01/25/2023] Open
Abstract
Importin-(Imp)β family nucleocytoplasmic transport receptors (NTRs) are supposed to bind to their cargoes through interaction between a confined interface on an NTR and a nuclear localization or export signal (NLS/NES) on a cargo. Although consensus NLS/NES sequence motifs have been defined for cargoes of some NTRs, many experimentally identified cargoes of those NTRs lack those motifs, and consensus NLSs/NESs have been reported for only a few NTRs. Crystal structures of NTR–cargo complexes have exemplified 3D structure-dependent binding of cargoes lacking a consensus NLS/NES to different sites on an NTR. Since only a limited number of NTR–cargo interactions have been studied, whether most cargoes lacking a consensus NLS/NES bind to the same confined interface or to various sites on an NTR is still unclear. Addressing this issue, we generated four mutants of transportin-(Trn)SR, of which many cargoes lack a consensus NLS, and eight mutants of Imp13, where no consensus NLS has been defined, and we analyzed their binding to as many as 40 cargo candidates that we previously identified by a nuclear import reaction-based method. The cargoes bind differently to the NTR mutants, suggesting that positions on an NTR contribute differently to the binding of respective cargoes.
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13
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Baade I, Hutten S, Sternburg EL, Pörschke M, Hofweber M, Dormann D, Kehlenbach RH. The RNA-binding protein FUS is chaperoned and imported into the nucleus by a network of import receptors. J Biol Chem 2021; 296:100659. [PMID: 33857479 PMCID: PMC8131929 DOI: 10.1016/j.jbc.2021.100659] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Revised: 03/31/2021] [Accepted: 04/09/2021] [Indexed: 12/11/2022] Open
Abstract
Fused in sarcoma (FUS) is a predominantly nuclear RNA-binding protein with key functions in RNA processing and DNA damage repair. Defects in nuclear import of FUS have been linked to severe neurodegenerative diseases; hence, it is of great interest to understand this process and how it is dysregulated in disease. Transportin-1 (TNPO1) and the closely related transportin-2 have been identified as major nuclear import receptors of FUS. They bind to the C-terminal nuclear localization signal of FUS and mediate the protein's nuclear import and at the same time also suppress aberrant phase transitions of FUS in the cytoplasm. Whether FUS can utilize other nuclear transport receptors for the purpose of import and chaperoning has not been examined so far. Here, we show that FUS directly binds to different import receptors in vitro. FUS formed stable complexes not only with TNPO1 but also with transportin-3, importin β, importin 7, or the importin β/7 heterodimer. Binding of these alternative import receptors required arginine residues within FUS-RG/RGG motifs and was weakened by arginine methylation. Interaction with these importins suppressed FUS phase separation and reduced its sequestration into stress granules. In a permeabilized cell system, we further showed that transportin-3 had the capacity to import FUS into the nucleus, albeit with lower efficiency than TNPO1. Our data suggest that aggregation-prone RNA-binding proteins such as FUS may utilize a network of importins for chaperoning and import, similar to histones and ribosomal proteins.
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Affiliation(s)
- Imke Baade
- Department of Molecular Biology, Faculty of Medicine, GZMB, Georg-August-University Göttingen, Göttingen, Germany
| | - Saskia Hutten
- BioMedical Center (BMC), Cell Biology, Ludwig-Maximilians-University Munich, Planegg-Martinsried, Germany
| | - Erin L Sternburg
- BioMedical Center (BMC), Cell Biology, Ludwig-Maximilians-University Munich, Planegg-Martinsried, Germany
| | - Marius Pörschke
- Department of Molecular Biology, Faculty of Medicine, GZMB, Georg-August-University Göttingen, Göttingen, Germany
| | - Mario Hofweber
- BioMedical Center (BMC), Cell Biology, Ludwig-Maximilians-University Munich, Planegg-Martinsried, Germany
| | - Dorothee Dormann
- BioMedical Center (BMC), Cell Biology, Ludwig-Maximilians-University Munich, Planegg-Martinsried, Germany; Munich Cluster for Systems Neurology (SyNergy), Munich, Germany.
| | - Ralph H Kehlenbach
- Department of Molecular Biology, Faculty of Medicine, GZMB, Georg-August-University Göttingen, Göttingen, Germany.
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14
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Abstract
Bidirectional transport of macromolecules across the nuclear envelope is a hallmark of eukaryotic cells, in which the genetic material is compartmentalized inside the nucleus. The nuclear pore complex (NPC) is the major gateway to the nucleus and it regulates nucleocytoplasmic transport, which is key to processes including transcriptional regulation and cell cycle control. Accordingly, components of the nuclear transport machinery are often found to be dysregulated or hijacked in diseases. In this Cell Science at a Glance article and accompanying poster, we provide an overview of our current understanding of cargo transport through the NPC, from the basic transport signals and machinery to more emerging aspects, all from a 'cargo perspective'. Among these, we discuss the transport of large cargoes (>15 nm), as well as the roles of different cargo properties to nuclear transport, from size and number of bound nuclear transport receptors (NTRs), to surface and mechanical properties.
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Affiliation(s)
- Giulia Paci
- Biocentre, Johannes Gutenberg-University Mainz, Hans-Dieter-Hüsch-Weg 15, 555128 Mainz, Germany.,Institute of Molecular Biology, Ackermannweg 4, 55128 Mainz, Germany.,European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Joana Caria
- Biocentre, Johannes Gutenberg-University Mainz, Hans-Dieter-Hüsch-Weg 15, 555128 Mainz, Germany.,Institute of Molecular Biology, Ackermannweg 4, 55128 Mainz, Germany.,European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Edward A Lemke
- Biocentre, Johannes Gutenberg-University Mainz, Hans-Dieter-Hüsch-Weg 15, 555128 Mainz, Germany .,Institute of Molecular Biology, Ackermannweg 4, 55128 Mainz, Germany.,European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany
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15
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Zohud BA, Guo P, Zohud BA, Li F, Hao JJ, Shan X, Yu W, Guo W, Qin Y, Cai X. Importin 13 promotes NSCLC progression by mediating RFPL3 nuclear translocation and hTERT expression upregulation. Cell Death Dis 2020; 11:879. [PMID: 33082305 PMCID: PMC7575581 DOI: 10.1038/s41419-020-03101-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 09/23/2020] [Accepted: 09/25/2020] [Indexed: 12/13/2022]
Abstract
Our previous studies have reported that RFPL3 protein exerts its unique function as a transcriptional factor of hTERT promoter after being transported into the lung cancer cell nucleus. However, the detailed mechanism by which RFPL3 undergoes nuclear transport has not been reported yet. Here, we identified RFPL3 as a potential import cargo for IPO13, which was found to be overexpressed in NSCLC cells and tissues. IPO13 interacted with RFPL3 in lung cancer cells, and the knockdown of IPO13 led to the cytoplasmic accumulation of RFPL3, the decreased anchoring of RFPL3 at hTERT promoter, and the downregulation of hTERT expression. Moreover, IPO13 silencing suppressed tumor growth in vitro and in vivo. IHC analysis confirmed the positive correlation between the expression levels of IPO13 and hTERT in the tumor tissues from patients with lung cancer. Furthermore, the mechanistic study revealed that IPO13 recognized RFPL3 via a functional nuclear localization signal (NLS), which is located in the B30.2 domain at the C-terminal region of RFPL3. Of note, the presence of EGFR mutations was significantly related to the increased IPO13 expression. The EGFR-TKI Osimertinib downregulated IPO13 expression level in NSCLC cell lines with EGFR mutations, but not in EGFR wild-type ones. In summary, our data suggest that inhibition of IPO13 transport activity itself might be an alternative and potential therapeutic strategy for NSCLC.
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Affiliation(s)
| | - Ping Guo
- Institute of Cancer Stem Cell, Dalian Medical University, 116044, Dalian, China
| | | | - Fengzhou Li
- The First Affiliated Hospital of Dalian Medical University, 116011, Dalian, China
| | - Jiao J Hao
- Institute of Cancer Stem Cell, Dalian Medical University, 116044, Dalian, China
| | - Xiu Shan
- The First Affiliated Hospital of Dalian Medical University, 116011, Dalian, China
| | - Wendan Yu
- Institute of Cancer Stem Cell, Dalian Medical University, 116044, Dalian, China
| | - Wei Guo
- Institute of Cancer Stem Cell, Dalian Medical University, 116044, Dalian, China.
| | - Yu Qin
- The First Affiliated Hospital of Dalian Medical University, 116011, Dalian, China.
| | - Xin Cai
- The First Affiliated Hospital of Dalian Medical University, 116011, Dalian, China.
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16
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Choudhury P, Kretschmer J, Hackert P, Bohnsack KE, Bohnsack MT. The DExD box ATPase DDX55 is recruited to domain IV of the 28S ribosomal RNA by its C-terminal region. RNA Biol 2020; 18:1124-1135. [PMID: 33048000 PMCID: PMC8244758 DOI: 10.1080/15476286.2020.1829366] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
RNA helicases contribute to diverse aspects of RNA metabolism through their functions in re-arranging RNA structures. Identification of the remodelling targets of RNA helicases is a critical step in elucidating their cellular functions. Here, we show that, in contrast to many other ribosome biogenesis factors, the DExD box ATPase DDX55 predominantly localizes to the nucleoplasm and we identify a nuclear localization signal within the C-terminal region of the protein. DDX55 associates with pre-ribosomal subunits in human cells and is required for maturation of large subunit pre-rRNAs. Interestingly, in vitro analyses show that DDX55 selectively associates with double-stranded RNA substrates, which also stimulate its ATPase activity, and our data suggest that the C-terminal region of DDX55 contributes to this substrate specificity. The C-terminal region of DDX55 is also necessary for recruitment of the helicase to pre-ribosomes and, using in vivo crosslinking, we reveal a binding site for DDX55 in helix H62 of the 28S ribosomal RNA. Taken together, these data highlight the importance of the C-terminal region of DDX55 in substrate specificity and recruitment, and identify domain IV as a potential remodelling target of DDX55 during LSU biogenesis.
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Affiliation(s)
- Priyanka Choudhury
- Department of Molecular Biology, University Medical Centre Göttingen, Göttingen, Germany
| | - Jens Kretschmer
- Department of Molecular Biology, University Medical Centre Göttingen, Göttingen, Germany
| | - Philipp Hackert
- Department of Molecular Biology, University Medical Centre Göttingen, Göttingen, Germany
| | - Katherine E Bohnsack
- Department of Molecular Biology, University Medical Centre Göttingen, Göttingen, Germany
| | - Markus T Bohnsack
- Department of Molecular Biology, University Medical Centre Göttingen, Göttingen, Germany.,Göttingen Center for Molecular Biosciences, Georg-August University, Göttingen, Germany
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17
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Ernst S, Müller-Newen G. Nucleocytoplasmic Shuttling of STATs. A Target for Intervention? Cancers (Basel) 2019; 11:cancers11111815. [PMID: 31752278 PMCID: PMC6895884 DOI: 10.3390/cancers11111815] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Revised: 11/08/2019] [Accepted: 11/13/2019] [Indexed: 12/12/2022] Open
Abstract
Signal transducer and activator of transcription (STAT) proteins are transcription factors that in the latent state are located predominantly in the cytoplasm. Activation of STATs through phosphorylation of a single tyrosine residue results in nuclear translocation. The requirement of tyrosine phosphorylation for nuclear accumulation is shared by all STAT family members but mechanisms of nuclear translocation vary between different STATs. These differences offer opportunities for specific intervention. To achieve this, the molecular mechanisms of nucleocytoplasmic shuttling of STATs need to be understood in more detail. In this review we will give an overview on the various aspects of nucleocytoplasmic shuttling of latent and activated STATs with a special focus on STAT3 and STAT5. Potential targets for cancer treatment will be identified and discussed.
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Affiliation(s)
- Sabrina Ernst
- Institute of Biochemistry and Molecular Biology, RWTH Aachen University, 52074 Aachen, Germany;
- Confocal Microscopy Facility, Interdisciplinary Center for Clinical Research IZKF, RWTH Aachen University, 52074 Aachen, Germany
| | - Gerhard Müller-Newen
- Institute of Biochemistry and Molecular Biology, RWTH Aachen University, 52074 Aachen, Germany;
- Correspondence:
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18
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Vera Rodriguez A, Frey S, Görlich D. Engineered SUMO/protease system identifies Pdr6 as a bidirectional nuclear transport receptor. J Cell Biol 2019; 218:2006-2020. [PMID: 31023724 PMCID: PMC6548132 DOI: 10.1083/jcb.201812091] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Revised: 03/26/2019] [Accepted: 03/28/2019] [Indexed: 01/07/2023] Open
Abstract
Cleavage of affinity tags by specific proteases can be exploited for highly selective affinity chromatography. The SUMO/SENP1 system is the most efficient for such application but fails in eukaryotic expression because it cross-reacts with endogenous proteases. Using a novel selection system, we have evolved the SUMOEu/SENP1Eu pair to orthogonality with the yeast and animal enzymes. SUMOEu fusions therefore remain stable in eukaryotic cells. Likewise, overexpressing a SENP1Eu protease is nontoxic in yeast. We have used the SUMOEu system in an affinity-capture-proteolytic-release approach to identify interactors of the yeast importin Pdr6/Kap122. This revealed not only further nuclear import substrates such as Ubc9, but also Pil1, Lsp1, eIF5A, and eEF2 as RanGTP-dependent binders and thus as export cargoes. We confirmed that Pdr6 functions as an exportin in vivo and depletes eIF5A and eEF2 from cell nuclei. Thus, Pdr6 is a bidirectional nuclear transport receptor (i.e., a biportin) that shuttles distinct sets of cargoes in opposite directions.
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Affiliation(s)
- Arturo Vera Rodriguez
- Department of Cellular Logistics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Steffen Frey
- Department of Cellular Logistics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Dirk Görlich
- Department of Cellular Logistics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
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19
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Aksu M, Trakhanov S, Vera Rodriguez A, Görlich D. Structural basis for the nuclear import and export functions of the biportin Pdr6/Kap122. J Cell Biol 2019; 218:1839-1852. [PMID: 31023722 PMCID: PMC6548137 DOI: 10.1083/jcb.201812093] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Revised: 03/26/2019] [Accepted: 03/28/2019] [Indexed: 12/26/2022] Open
Abstract
Importins ferry proteins into nuclei while exportins carry cargoes to the cytoplasm. In the accompanying paper in this issue (Vera Rodriguez et al. 2019. J. Cell Biol. https://doi.org/10.1083/jcb.201812091), we discovered that Pdr6 is a biportin that imports, e.g., the SUMO E2 ligase Ubc9 while depleting the translation factor eIF5A from the nuclear compartment. In this paper, we report the structures of key transport intermediates, namely, of the Ubc9•Pdr6 import complex, of the RanGTP•Pdr6 heterodimer, and of the trimeric RanGTP•Pdr6•eIF5A export complex. These revealed nonlinear transport signals, chaperone-like interactions, and how the RanGTPase system drives Pdr6 to transport Ubc9 and eIF5A in opposite directions. The structures also provide unexpected insights into the evolution of transport selectivity. Specifically, they show that recognition of Ubc9 by Pdr6 differs fundamentally from that of the human Ubc9-importer Importin 13. Likewise, Pdr6 recognizes eIF5A in a nonhomologous manner compared with the mammalian eIF5A-exporter Exportin 4. This suggests that the import of Ubc9 and active nuclear exclusion of eIF5A evolved in different eukaryotic lineages more than once and independently from each other.
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Affiliation(s)
- Metin Aksu
- Department of Cellular Logistics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Sergei Trakhanov
- Department of Cellular Logistics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Arturo Vera Rodriguez
- Department of Cellular Logistics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Dirk Görlich
- Department of Cellular Logistics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
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20
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Abstract
Nuclear pore complexes (NPCs) mediate nucleocytoplasmic exchange. They are exceptionally large protein complexes that fuse the inner and outer nuclear membranes to form channels across the nuclear envelope. About 30 different protein components, termed nucleoporins, assemble in multiple copies into an intricate cylindrical architecture. Here, we review our current knowledge of the structure of nucleoporins and how those come together in situ. We delineate architectural principles on several hierarchical organization levels, including isoforms, posttranslational modifications, nucleoporins, and higher-order oligomerization of nucleoporin subcomplexes. We discuss how cells exploit this modularity to faithfully assemble NPCs.
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Affiliation(s)
- Bernhard Hampoelz
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany; , ,
| | - Amparo Andres-Pons
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany; , , .,Current affiliation: Friedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland;
| | - Panagiotis Kastritis
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany; , , .,Current affiliation: ZIK HALOmem, Martin Luther University of Halle-Wittenberg, 06120 Halle (Saale), Germany
| | - Martin Beck
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany; , , .,Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany.,Max Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany
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21
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Abstract
The molecular mechanisms of nuclear transport have been described in great detail and we are beginning to understand the structures of transport complexes and even of subcomplexes of the nuclear pore at an atomic or near-atomic resolution. The complexity of the clients that use the transport machinery, by contrast, is less well understood, although some transport receptors are reported to have hundreds of different cargoes and others only a few. Here, we review the recent attempts to define the cargo spectrum of individual nuclear transport receptors using bioinformatic, biochemical and cell biological approaches and compare the results obtained by these complementary methods. Remarkably, a large fraction of the soluble proteome can be subject to nucleocytoplasmic transport.
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Affiliation(s)
- Imke Baade
- Department of Molecular Biology, Faculty of Medicine, Göttingen Center of Biosciences (GZMB), Georg-August-University Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
| | - Ralph H Kehlenbach
- Department of Molecular Biology, Faculty of Medicine, Göttingen Center of Biosciences (GZMB), Georg-August-University Göttingen, Humboldtallee 23, 37073 Göttingen, Germany.
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