1
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Taylor IA, Fassati A. The capsid revolution. J Mol Cell Biol 2024; 15:mjad076. [PMID: 38037430 PMCID: PMC11193064 DOI: 10.1093/jmcb/mjad076] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Revised: 11/23/2023] [Accepted: 11/29/2023] [Indexed: 12/02/2023] Open
Abstract
Lenacapavir, targeting the human immunodeficiency virus type-1 (HIV-1) capsid, is the first-in-class antiretroviral drug recently approved for clinical use. The development of Lenacapavir is attributed to the remarkable progress in our understanding of the capsid protein made during the last few years. Considered little more than a component of the virus shell to be shed early during infection, the capsid has been found to be a key player in the HIV-1 life cycle by interacting with multiple host factors, entering the nucleus, and directing integration. Here, we describe the key advances that led to this 'capsid revolution'.
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Affiliation(s)
- Ian A Taylor
- Macromolecular Structure Laboratory, The Francis Crick Institute, London NW1 1AT, UK
| | - Ariberto Fassati
- Division of Infection and Immunity, University College London, London WC1E 6JF, UK
- Institute of Immunity and Transplantation, University College London, London NW3 2PP, UK
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2
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Matsuda A, Mofrad MRK. On the nuclear pore complex and its emerging role in cellular mechanotransduction. APL Bioeng 2022; 6:011504. [PMID: 35308827 PMCID: PMC8916845 DOI: 10.1063/5.0080480] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 02/21/2022] [Indexed: 12/13/2022] Open
Abstract
The nuclear pore complex (NPC) is a large protein assembly that perforates the nuclear envelope and provides a sole gateway for traffic between the cytoplasm and the nucleus. The NPC controls the nucleocytoplasmic transport by selectively allowing cargoes such as proteins and mRNA to pass through its central channel, thereby playing a vital role in protecting the nuclear component and regulating gene expression and protein synthesis. The selective transport through the NPC originates from its exquisite molecular structure featuring a large scaffold and the intrinsically disordered central channel domain, but the exact mechanism underlying the selective transport remains elusive and is the subject of various, often conflicting, hypotheses. Moreover, recent studies have suggested a new role for the NPC as a mechanosensor, where the NPC changes its channel diameter depending on the nuclear envelope tension, altering the molecular transportability through this nanopore. In this mini-review, we summarize the current understandings of the selective nature of the NPC and discuss its emerging role in cellular mechanotransduction.
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Affiliation(s)
- Atsushi Matsuda
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California Berkeley, Berkeley, California 94720, USA
| | - Mohammad R. K. Mofrad
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California Berkeley, Berkeley, California 94720, USA
- Molecular Biophysics and Integrative Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
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3
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Davis LK, Ford IJ, Hoogenboom BW. Crowding-induced phase separation of nuclear transport receptors in FG nucleoporin assemblies. eLife 2022; 11:72627. [PMID: 35098921 PMCID: PMC8880993 DOI: 10.7554/elife.72627] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 01/28/2022] [Indexed: 11/13/2022] Open
Abstract
The rapid (< 1 ms) transport of biological material to and from the cell nucleus is regulated by the nuclear pore complex (NPC). At the core of the NPC is a permeability barrier consisting of intrinsically disordered Phe-Gly (FG) nucleoporins (FG Nups). Various types of nuclear transport receptors (NTRs) facilitate transport by partitioning in the FG Nup assembly, overcoming the barrier by their affinity to the FG Nups, and comprise a significant fraction of proteins in the NPC barrier. In previous work Zahn et al. (2016), we revealed a universal physical behaviour in the experimentally observed binding of two well-characterized NTRs, NTF2 and the larger Importin-β, to different planar assemblies of FG Nups, with the binding behaviour defined by negative cooperativity. This was further validated by a minimal physical model that treated the FG Nups as flexible homopolymers and the NTRs as uniformly cohesive spheres. Here, we build upon our original study by first parametrizing our model to experimental data, and next predicting the effects of crowding by different types of NTRs. We show how varying the amounts of one type of NTR modulates how the other NTR penetrates the FG Nup assembly. Notably, at similar and physiologically relevant NTR concentrations, our model predicts demixed phases of NTF2 and Imp-β within the FG Nup assembly. The functional implication of NTR phase separation is that NPCs may sustain separate transport pathways that are determined by inter-NTR competition.
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Affiliation(s)
- Luke K Davis
- Department of Physics and Astronomy, University College London, London, United Kingdom
| | - Ian J Ford
- Department of Physics and Astronomy, University College London, London, United Kingdom
| | - Bart W Hoogenboom
- London Centre for Nanotechnology, University College London, London, United Kingdom
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4
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Matsuda A, Mofrad MRK. Free energy calculations shed light on the nuclear pore complex's selective barrier nature. Biophys J 2021; 120:3628-3640. [PMID: 34339633 PMCID: PMC8456294 DOI: 10.1016/j.bpj.2021.07.025] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 05/27/2021] [Accepted: 07/27/2021] [Indexed: 12/27/2022] Open
Abstract
The nuclear pore complex (NPC) is the exclusive gateway for traffic control across the nuclear envelope. Although smaller cargoes (less than 5-9 nm in size) can freely diffuse through the NPC, the passage of larger cargoes is restricted to those accompanied by nuclear transport receptors (NTRs). This selective barrier nature of the NPC is putatively associated with the intrinsically disordered, phenylalanine-glycine repeat-domains containing nucleoporins, termed FG-Nups. The precise mechanism underlying how FG-Nups carry out such an exquisite task at high throughputs has, however, remained elusive and the subject of various hypotheses. From the thermodynamics perspective, free energy analysis can be a way to determine cargo's transportability because the traffic through the NPC must be in the direction of reducing the free energy. In this study, we developed a computational model to evaluate the free energy composed of the conformational entropy of FG-Nups and the energetic gain associated with binding interactions between FG-Nups and NTRs and investigated whether these physical features can be the basis of NPC's selectivity. Our results showed that the reduction in conformational entropy by inserting a cargo into the NPC increased the free energy by an amount substantially greater than the thermal energy (≫kBT), whereas the free energy change was negligible (
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Affiliation(s)
- Atsushi Matsuda
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California Berkeley, Berkeley, California
| | - Mohammad R K Mofrad
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California Berkeley, Berkeley, California; Molecular Biophysics and Integrative Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California.
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5
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Hoogenboom BW, Hough LE, Lemke EA, Lim RYH, Onck PR, Zilman A. Physics of the Nuclear Pore Complex: Theory, Modeling and Experiment. PHYSICS REPORTS 2021; 921:1-53. [PMID: 35892075 PMCID: PMC9306291 DOI: 10.1016/j.physrep.2021.03.003] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The hallmark of eukaryotic cells is the nucleus that contains the genome, enclosed by a physical barrier known as the nuclear envelope (NE). On the one hand, this compartmentalization endows the eukaryotic cells with high regulatory complexity and flexibility. On the other hand, it poses a tremendous logistic and energetic problem of transporting millions of molecules per second across the nuclear envelope, to facilitate their biological function in all compartments of the cell. Therefore, eukaryotes have evolved a molecular "nanomachine" known as the Nuclear Pore Complex (NPC). Embedded in the nuclear envelope, NPCs control and regulate all the bi-directional transport between the cell nucleus and the cytoplasm. NPCs combine high molecular specificity of transport with high throughput and speed, and are highly robust with respect to molecular noise and structural perturbations. Remarkably, the functional mechanisms of NPC transport are highly conserved among eukaryotes, from yeast to humans, despite significant differences in the molecular components among various species. The NPC is the largest macromolecular complex in the cell. Yet, despite its significant complexity, it has become clear that its principles of operation can be largely understood based on fundamental physical concepts, as have emerged from a combination of experimental methods of molecular cell biology, biophysics, nanoscience and theoretical and computational modeling. Indeed, many aspects of NPC function can be recapitulated in artificial mimics with a drastically reduced complexity compared to biological pores. We review the current physical understanding of the NPC architecture and function, with the focus on the critical analysis of experimental studies in cells and artificial NPC mimics through the lens of theoretical and computational models. We also discuss the connections between the emerging concepts of NPC operation and other areas of biophysics and bionanotechnology.
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Affiliation(s)
- Bart W. Hoogenboom
- London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom
| | - Loren E. Hough
- Department of Physics and BioFrontiers Institute, University of Colorado, Boulder CO 80309, United States of America
| | - Edward A. Lemke
- Biocenter Mainz, Departments of Biology and Chemistry, Johannes Gutenberg University and Institute of Molecular Biology, 55128 Mainz, Germany
| | - Roderick Y. H. Lim
- Biozentrum and the Swiss Nanoscience Institute, University of Basel, 4056 Basel, Switzerland
| | - Patrick R. Onck
- Zernike Institute for Advanced Materials, University of Groningen, 9747 AG Groningen, The Netherlands
| | - Anton Zilman
- Department of Physics and Institute for Biomedical Engineering (IBME), University of Toronto, Toronto, ON M5S 1A7, Canada
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6
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Blanco-Rodriguez G, Di Nunzio F. The Viral Capsid: A Master Key to Access the Host Nucleus. Viruses 2021; 13:v13061178. [PMID: 34203080 PMCID: PMC8234750 DOI: 10.3390/v13061178] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2021] [Revised: 06/02/2021] [Accepted: 06/16/2021] [Indexed: 12/15/2022] Open
Abstract
Viruses are pathogens that have evolved to hijack the cellular machinery to replicate themselves and spread to new cells. During the course of evolution, viruses developed different strategies to overcome the cellular defenses and create new progeny. Among them, some RNA and many DNA viruses require access to the nucleus to replicate their genome. In non-dividing cells, viruses can only access the nucleus through the nuclear pore complex (NPC). Therefore, viruses have developed strategies to usurp the nuclear transport machinery and gain access to the nucleus. The majority of these viruses use the capsid to manipulate the nuclear import machinery. However, the particular tactics employed by each virus to reach the host chromatin compartment are very different. Nevertheless, they all require some degree of capsid remodeling. Recent notions on the interplay between the viral capsid and cellular factors shine new light on the quest for the nuclear entry step and for the fate of these viruses. In this review, we describe the main components and function of nuclear transport machinery. Next, we discuss selected examples of RNA and DNA viruses (HBV, HSV, adenovirus, and HIV) that remodel their capsid as part of their strategies to access the nucleus and to replicate.
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Affiliation(s)
- Guillermo Blanco-Rodriguez
- Advanced Molecular Virology and Retroviral Dynamics Group, Department of Virology, Pasteur Institute, 75015 Paris, France;
- Immunity and Cancer Department, Curie Institute, PSL Research University, INSERM U932, 75005 Paris, France
| | - Francesca Di Nunzio
- Advanced Molecular Virology and Retroviral Dynamics Group, Department of Virology, Pasteur Institute, 75015 Paris, France;
- Correspondence:
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7
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AlBurtamani N, Paul A, Fassati A. The Role of Capsid in the Early Steps of HIV-1 Infection: New Insights into the Core of the Matter. Viruses 2021; 13:v13061161. [PMID: 34204384 PMCID: PMC8234406 DOI: 10.3390/v13061161] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Revised: 06/10/2021] [Accepted: 06/14/2021] [Indexed: 01/27/2023] Open
Abstract
In recent years, major advances in research and experimental approaches have significantly increased our knowledge on the role of the HIV-1 capsid in the virus life cycle, from reverse transcription to integration and gene expression. This makes the capsid protein a good pharmacological target to inhibit HIV-1 replication. This review covers our current understanding of the role of the viral capsid in the HIV-1 life cycle and its interaction with different host factors that enable reverse transcription, trafficking towards the nucleus, nuclear import and integration into host chromosomes. It also describes different promising small molecules, some of them in clinical trials, as potential targets for HIV-1 therapy.
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8
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Davis LK, Šarić A, Hoogenboom BW, Zilman A. Physical modeling of multivalent interactions in the nuclear pore complex. Biophys J 2021; 120:1565-1577. [PMID: 33617830 PMCID: PMC8204217 DOI: 10.1016/j.bpj.2021.01.039] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Revised: 01/25/2021] [Accepted: 01/27/2021] [Indexed: 01/10/2023] Open
Abstract
In the nuclear pore complex, intrinsically disordered proteins (FG Nups), along with their interactions with more globular proteins called nuclear transport receptors (NTRs), are vital to the selectivity of transport into and out of the cell nucleus. Although such interactions can be modeled at different levels of coarse graining, in vitro experimental data have been quantitatively described by minimal models that describe FG Nups as cohesive homogeneous polymers and NTRs as uniformly cohesive spheres, in which the heterogeneous effects have been smeared out. By definition, these minimal models do not account for the explicit heterogeneities in FG Nup sequences, essentially a string of cohesive and noncohesive polymer units, and at the NTR surface. Here, we develop computational and analytical models that do take into account such heterogeneity in a minimal fashion and compare them with experimental data on single-molecule interactions between FG Nups and NTRs. Overall, we find that the heterogeneous nature of FG Nups and NTRs does play a role in determining equilibrium binding properties but is of much greater significance when it comes to unbinding and binding kinetics. Using our models, we predict how binding equilibria and kinetics depend on the distribution of cohesive blocks in the FG Nup sequences and of the binding pockets at the NTR surface, with multivalency playing a key role. Finally, we observe that single-molecule binding kinetics has a rather minor influence on the diffusion of NTRs in polymer melts consisting of FG-Nup-like sequences.
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Affiliation(s)
- Luke K Davis
- Department of Physics and Astronomy; Institute for the Physics of Living Systems; London Centre for Nanotechnology, University College London, London, United Kingdom
| | - Anđela Šarić
- Department of Physics and Astronomy; Institute for the Physics of Living Systems
| | - Bart W Hoogenboom
- Department of Physics and Astronomy; Institute for the Physics of Living Systems; London Centre for Nanotechnology, University College London, London, United Kingdom.
| | - Anton Zilman
- Department of Physics, University of Toronto, Toronto, Ontario, Canada; Institute for Biomedical Engineering, Toronto, Ontario, Canada.
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9
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Modeling the nucleoporins that form the hairy pores. Biochem Soc Trans 2020; 48:1447-1461. [DOI: 10.1042/bst20190941] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Revised: 07/03/2020] [Accepted: 07/16/2020] [Indexed: 11/17/2022]
Abstract
Sitting on the nuclear envelope, nuclear pore complexes (NPCs) control the molecular transport between the nucleus and the cytoplasm. Without definite open or close states, the NPC uses a family of intrinsically disordered nucleoporins called FG-Nups to construct a selective permeability barrier whose functional structure is unclear. Experimental advances have offered high-resolution molecular knowledge of the NPC scaffold and docking of the unfolded FG-Nups, however, the ‘hairy’ barrier structure still appears as blurred lobes even under the state-of-the-art microscopy. Without accurate experimental visualization, the molecular mechanism for the NPC-mediated transport remains a matter of debate. Modeling provides an alternative way to resolve this long-standing mystery. Here, we briefly review different methods employed in modeling the FG-Nups, arranging from all-atom molecular dynamics to mean-field theories. We discuss the advantage and limit of each modeling technique, and summarize the theoretical insights that, despite certain controversy, deepened our understanding of the hairy pore.
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10
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Li CW, Merlitz H, Sommer JU. Mean-Field Model of the Collapse Transition of Brushes inside Cylindrical Nanopores. Macromolecules 2020. [DOI: 10.1021/acs.macromol.0c00618] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Cheng-Wu Li
- Leibniz-Institut of Polymer Research Dresden, 01069 Dresden, Germany
| | - Holger Merlitz
- Leibniz-Institut of Polymer Research Dresden, 01069 Dresden, Germany
| | - Jens-Uwe Sommer
- Leibniz-Institut of Polymer Research Dresden, 01069 Dresden, Germany
- Institute for Theoretical Physics, TU Dresden, Zellescher Weg 13, 01069 Dresden, Germany
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11
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Davis LK, Ford IJ, Šarić A, Hoogenboom BW. Intrinsically disordered nuclear pore proteins show ideal-polymer morphologies and dynamics. Phys Rev E 2020; 101:022420. [PMID: 32168597 DOI: 10.1103/physreve.101.022420] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2019] [Accepted: 02/03/2020] [Indexed: 06/10/2023]
Abstract
In the nuclear pore complex, intrinsically disordered nuclear pore proteins (FG Nups) form a selective barrier for transport into and out of the cell nucleus, in a way that remains poorly understood. The collective FG Nup behavior has long been conceptualized either as a polymer brush, dominated by entropic and excluded-volume (repulsive) interactions, or as a hydrogel, dominated by cohesive (attractive) interactions between FG Nups. Here we compare mesoscale computational simulations with a wide range of experimental data to demonstrate that FG Nups are at the crossover point between these two regimes. Specifically, we find that repulsive and attractive interactions are balanced, resulting in morphologies and dynamics that are close to those of ideal polymer chains. We demonstrate that this property of FG Nups yields sufficient cohesion to seal the transport barrier, and yet maintains fast dynamics at the molecular scale, permitting the rapid polymer rearrangements needed for transport events.
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Affiliation(s)
- Luke K Davis
- London Centre for Nanotechnology, University College London, London WC1H OAH, United Kingdom
- Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom
- Institute for the Physics of Living Systems, University College London, London WC1E 6BT, United Kingdom
| | - Ian J Ford
- London Centre for Nanotechnology, University College London, London WC1H OAH, United Kingdom
- Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom
| | - Anđela Šarić
- Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom
- Institute for the Physics of Living Systems, University College London, London WC1E 6BT, United Kingdom
| | - Bart W Hoogenboom
- London Centre for Nanotechnology, University College London, London WC1H OAH, United Kingdom
- Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom
- Institute for the Physics of Living Systems, University College London, London WC1E 6BT, United Kingdom
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12
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Enhanced Nucleocytoplasmic Transport due to Competition for Elastic Binding Sites. Biophys J 2019; 115:108-116. [PMID: 29972802 DOI: 10.1016/j.bpj.2018.05.034] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Revised: 05/21/2018] [Accepted: 05/31/2018] [Indexed: 01/08/2023] Open
Abstract
Nuclear pore complexes (NPCs) control all traffic into and out of the cell nucleus. NPCs are molecular machines that simultaneously achieve high selectivity and high transport rates. The biophysical details of how cargoes rapidly traverse the pore remain unclear but are known to be mediated by interactions between cargo-binding chaperone proteins and natively unstructured nucleoporin proteins containing many phenylalanine-glycine repeats (FG nups) that line the pore's central channel. Here, we propose a specific and detailed physical mechanism for the high speed of nuclear import based on the elasticity of FG nups and on competition between individual chaperone proteins for FG nup binding. We develop a mathematical model to support our proposed mechanism. We suggest that the recycling of nuclear import factors back to the cytoplasm is important for driving high-speed import and predict the existence of an optimal cytoplasmic concentration of cargo for enhancing the rate of import over a purely diffusive rate.
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13
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Stanley G, Akpinar B, Shen Q, Fisher PDE, Lusk CP, Lin C, Hoogenboom BW. Quantification of Biomolecular Dynamics Inside Real and Synthetic Nuclear Pore Complexes Using Time-Resolved Atomic Force Microscopy. ACS NANO 2019; 13:7949-7956. [PMID: 31241896 PMCID: PMC6660115 DOI: 10.1021/acsnano.9b02424] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2019] [Accepted: 06/26/2019] [Indexed: 05/30/2023]
Abstract
Over the past decades, atomic force microscopy (AFM) has emerged as an increasingly powerful tool to study the dynamics of biomolecules at nanometer length scales. However, the more stochastic the nature of such biomolecular dynamics, the harder it becomes to distinguish them from AFM measurement noise. Rapid, stochastic dynamics are inherent to biological systems comprising intrinsically disordered proteins. One role of such proteins is in the formation of the transport barrier of the nuclear pore complex (NPC): the selective gateway for macromolecular traffic entering or exiting the nucleus. Here, we use AFM to observe the dynamics of intrinsically disordered proteins from two systems: the transport barrier of native NPCs and the transport barrier of a mimetic NPC made using a DNA origami scaffold. Analyzing data recorded with 50-200 ms temporal resolution, we highlight the importance of drift correction and appropriate baseline measurements in such experiments. In addition, we describe an autocorrelation analysis to quantify time scales of observed dynamics and to assess their veracity-an analysis protocol that lends itself to the quantification of stochastic fluctuations in other biomolecular systems. The results reveal the surprisingly slow rate of stochastic, collective transitions inside mimetic NPCs, highlighting the importance of FG-nup cohesive interactions.
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Affiliation(s)
- George
J. Stanley
- London
Centre for Nanotechnology, University College
London, 17-19 Gordon Street, London WC1H 0AH, United Kingdom
| | - Bernice Akpinar
- London
Centre for Nanotechnology, University College
London, 17-19 Gordon Street, London WC1H 0AH, United Kingdom
- Department
of Chemistry, Imperial College London, London SW7 2AZ, United Kingdom
| | - Qi Shen
- Department
of Cell Biology, Yale School of Medicine, New Haven, Connecticut 06520, United States
- Nanobiology
Institute, Yale University, West Haven, Connecticut 06516, United States
| | - Patrick D. Ellis Fisher
- Department
of Cell Biology, Yale School of Medicine, New Haven, Connecticut 06520, United States
- Nanobiology
Institute, Yale University, West Haven, Connecticut 06516, United States
| | - C. Patrick Lusk
- Department
of Cell Biology, Yale School of Medicine, New Haven, Connecticut 06520, United States
| | - Chenxiang Lin
- Department
of Cell Biology, Yale School of Medicine, New Haven, Connecticut 06520, United States
- Nanobiology
Institute, Yale University, West Haven, Connecticut 06516, United States
| | - Bart W. Hoogenboom
- London
Centre for Nanotechnology, University College
London, 17-19 Gordon Street, London WC1H 0AH, United Kingdom
- Department
of Physics and Astronomy, University College
London, Gower Street, London WC1E 6BT, United Kingdom
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14
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Ro S, Gopinathan A, Kim YW. Interactions between a fluctuating polymer barrier and transport factors together with enzyme action are sufficient for selective and rapid transport through the nuclear pore complex. Phys Rev E 2018; 98:012403. [PMID: 30110828 DOI: 10.1103/physreve.98.012403] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Indexed: 01/13/2023]
Abstract
The nuclear pore complex, the only pathway for transport between the nucleus and cytoplasm, functions as a highly selective gate that blocks nonspecific macromolecules while allowing the rapid transport of tagged [transport factor (TF) bound] cargo up to an order of magnitude larger. The mechanism of this gate's operation is not yet fully understood and progress has been primarily hindered by the inherent complexity and multiscale nature of the problem. One needs to consider the hundreds of disordered proteins (phenylalanine glycine nucleoporins or FG nups) lining the pore, as well as their overall architecture and dynamics at the microsecond scale, while also accounting for transport at the millisecond scale across the entire pore. Here we formulate an approach that addresses transport properties over a large range of length and time scales. We do this by incorporating microscopic biophysical details, such as charge and specific TF-FG nup interactions, to compute the free energy landscape encountered by the cargo. We connect this to macroscopic transport by treating cargo translocation as a stochastic barrier crossing process and computing the current and the translocation time. We then identify distinct transport regimes (fast permeable, slow permeable, and impermeable) determined by the cargo size, TF affinity for FG nups, and the activity of the enzymes that cleave TFs from cargo. Our results, therefore provide an integrated picture of transport through the NPC, while highlighting how FG nup interactions with TFs and enzyme activity cooperate to produce selectivity and efficiency.
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Affiliation(s)
- Sunghan Ro
- Department of Physics, Korea Advanced Institute of Science and Technology, Deajeon 34141, Korea.,Graduate School of Nanoscience and Technology, Korea Advanced Institute of Science and Technology, Deajeon 34141, Korea
| | - Ajay Gopinathan
- Department of Physics, University of California at Merced, Merced, California 95343, USA
| | - Yong Woon Kim
- Department of Physics, Korea Advanced Institute of Science and Technology, Deajeon 34141, Korea.,Graduate School of Nanoscience and Technology, Korea Advanced Institute of Science and Technology, Deajeon 34141, Korea
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15
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Stanley GJ, Fassati A, Hoogenboom BW. Atomic force microscopy reveals structural variability amongst nuclear pore complexes. Life Sci Alliance 2018; 1:e201800142. [PMID: 30456374 PMCID: PMC6238600 DOI: 10.26508/lsa.201800142] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Revised: 08/10/2018] [Accepted: 08/13/2018] [Indexed: 12/31/2022] Open
Abstract
The nuclear pore complex (NPC) is a proteinaceous assembly that regulates macromolecular transport into and out of the nucleus. Although the structure of its scaffold is being revealed in increasing detail, its transport functionality depends upon an assembly of intrinsically disordered proteins (called FG-Nups) anchored inside the pore's central channel, which have hitherto eluded structural characterization. Here, using high-resolution atomic force microscopy, we provide a structural and nanomechanical analysis of individual NPCs. Our data highlight the structural diversity and complexity at the nuclear envelope, showing the interplay between the lamina network, actin filaments, and the NPCs. It reveals the dynamic behaviour of NPC scaffolds and displays pores of varying sizes. Of functional importance, the NPC central channel shows large structural diversity, supporting the notion that FG-Nup cohesiveness is in a range that facilitates collective rearrangements at little energetic cost. Finally, different nuclear transport receptors are shown to interact in qualitatively different ways with the FG-Nups, with particularly strong binding of importin-β.
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Affiliation(s)
- George J Stanley
- London Centre for Nanotechnology, University College London, London, UK
| | - Ariberto Fassati
- Division of Infection and Immunity, University College London, London, UK
| | - Bart W Hoogenboom
- London Centre for Nanotechnology, University College London, London, UK.,Department of Physics and Astronomy, University College London, London, UK
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16
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Li CW, Merlitz H, Wu CX, Sommer JU. Nanopores as Switchable Gates for Nanoparticles: A Molecular Dynamics Study. Macromolecules 2018. [DOI: 10.1021/acs.macromol.8b01149] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Affiliation(s)
- Cheng-Wu Li
- Research Institute for Biomimetics and Soft Matter, Fujian Provincial Key Laboratory for Soft Functional Materials Research, Department of Physics, Xiamen University, Xiamen 361005, China
| | - Holger Merlitz
- Leibniz-Institut für Polymerforschung Dresden, 01069 Dresden, Germany
| | - Chen-Xu Wu
- Research Institute for Biomimetics and Soft Matter, Fujian Provincial Key Laboratory for Soft Functional Materials Research, Department of Physics, Xiamen University, Xiamen 361005, China
| | - Jens-Uwe Sommer
- Leibniz-Institut für Polymerforschung Dresden, 01069 Dresden, Germany
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17
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Fisher PDE, Shen Q, Akpinar B, Davis LK, Chung KKH, Baddeley D, Šarić A, Melia TJ, Hoogenboom BW, Lin C, Lusk CP. A Programmable DNA Origami Platform for Organizing Intrinsically Disordered Nucleoporins within Nanopore Confinement. ACS NANO 2018; 12:1508-1518. [PMID: 29350911 PMCID: PMC5834394 DOI: 10.1021/acsnano.7b08044] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Nuclear pore complexes (NPCs) form gateways that control molecular exchange between the nucleus and the cytoplasm. They impose a diffusion barrier to macromolecules and enable the selective transport of nuclear transport receptors with bound cargo. The underlying mechanisms that establish these permeability properties remain to be fully elucidated but require unstructured nuclear pore proteins rich in Phe-Gly (FG)-repeat domains of different types, such as FxFG and GLFG. While physical modeling and in vitro approaches have provided a framework for explaining how the FG network contributes to the barrier and transport properties of the NPC, it remains unknown whether the number and/or the spatial positioning of different FG-domains along a cylindrical, ∼40 nm diameter transport channel contributes to their collective properties and function. To begin to answer these questions, we have used DNA origami to build a cylinder that mimics the dimensions of the central transport channel and can house a specified number of FG-domains at specific positions with easily tunable design parameters, such as grafting density and topology. We find the overall morphology of the FG-domain assemblies to be dependent on their chemical composition, determined by the type and density of FG-repeat, and on their architectural confinement provided by the DNA cylinder, largely consistent with here presented molecular dynamics simulations based on a coarse-grained polymer model. In addition, high-speed atomic force microscopy reveals local and reversible FG-domain condensation that transiently occludes the lumen of the DNA central channel mimics, suggestive of how the NPC might establish its permeability properties.
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Affiliation(s)
- Patrick D. Ellis Fisher
- Department of Cell Biology, Yale School of Medicine, New Haven, Connecticut 06520, USA
- Nanobiology Institute, Yale University, West Haven, Connecticut 06516, USA
| | - Qi Shen
- Department of Cell Biology, Yale School of Medicine, New Haven, Connecticut 06520, USA
- Nanobiology Institute, Yale University, West Haven, Connecticut 06516, USA
| | - Bernice Akpinar
- Department of Chemistry, Imperial College London, London, SW7 2AZ, UK
- London Centre for Nanotechnology, University College London, 17–19 Gordon Street, London WC1H 0AH, UK
| | - Luke K. Davis
- London Centre for Nanotechnology, University College London, 17–19 Gordon Street, London WC1H 0AH, UK
- Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
- Institute for the Physics of Living Systems, University College London, Gower Street, London WC1E 6BT, UK
| | - Kenny Kwok Hin Chung
- Department of Cell Biology, Yale School of Medicine, New Haven, Connecticut 06520, USA
- Nanobiology Institute, Yale University, West Haven, Connecticut 06516, USA
| | - David Baddeley
- Department of Cell Biology, Yale School of Medicine, New Haven, Connecticut 06520, USA
- Nanobiology Institute, Yale University, West Haven, Connecticut 06516, USA
| | - Anđela Šarić
- Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
- Institute for the Physics of Living Systems, University College London, Gower Street, London WC1E 6BT, UK
| | - Thomas J. Melia
- Department of Cell Biology, Yale School of Medicine, New Haven, Connecticut 06520, USA
| | - Bart W. Hoogenboom
- London Centre for Nanotechnology, University College London, 17–19 Gordon Street, London WC1H 0AH, UK
- Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
- Institute for the Physics of Living Systems, University College London, Gower Street, London WC1E 6BT, UK
| | - Chenxiang Lin
- Department of Cell Biology, Yale School of Medicine, New Haven, Connecticut 06520, USA
- Nanobiology Institute, Yale University, West Haven, Connecticut 06516, USA
- Correspondence to: Chenxiang Lin: or C. Patrick Lusk:
| | - C. Patrick Lusk
- Department of Cell Biology, Yale School of Medicine, New Haven, Connecticut 06520, USA
- Correspondence to: Chenxiang Lin: or C. Patrick Lusk:
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18
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Lopez LG, Nap RJ. Highly sensitive gating in pH-responsive nanochannels as a result of ionic bridging and nanoconfinement. Phys Chem Chem Phys 2018; 20:16657-16665. [DOI: 10.1039/c8cp02028k] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Multivalent counterions can be used to control both the conductivity and opening of a nanogate functionalized with weak polyelectrolytes.
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Affiliation(s)
- Luis G. Lopez
- Department of Biomedical Engineering
- Department of Chemistry, and Chemistry of Life Processes Institute
- Northwestern University
- Evanston
- USA
| | - Rikkert J. Nap
- Department of Biomedical Engineering
- Department of Chemistry, and Chemistry of Life Processes Institute
- Northwestern University
- Evanston
- USA
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19
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Shams H, Soheilypour M, Peyro M, Moussavi-Baygi R, Mofrad MRK. Looking "Under the Hood" of Cellular Mechanotransduction with Computational Tools: A Systems Biomechanics Approach across Multiple Scales. ACS Biomater Sci Eng 2017; 3:2712-2726. [PMID: 33418698 DOI: 10.1021/acsbiomaterials.7b00117] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Signal modulation has been developed in living cells throughout evolution to promote utilizing the same machinery for multiple cellular functions. Chemical and mechanical modules of signal transmission and transduction are interconnected and necessary for organ development and growth. However, due to the high complexity of the intercommunication of physical intracellular connections with biochemical pathways, there are many missing details in our overall understanding of mechanotransduction processes, i.e., the process by which mechanical signals are converted to biochemical cascades. Cell-matrix adhesions are mechanically coupled to the nucleus through the cytoskeleton. This modulated and tightly integrated network mediates the transmission of mechanochemical signals from the extracellular matrix to the nucleus. Various experimental and computational techniques have been utilized to understand the basic mechanisms of mechanotransduction, yet many aspects have remained elusive. Recently, in silico experiments have made important contributions to the field of mechanobiology. Herein, computational modeling efforts devoted to understanding integrin-mediated mechanotransduction pathways are reviewed, and an outlook is presented for future directions toward using suitable computational approaches and developing novel techniques for addressing important questions in the field of mechanotransduction.
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Affiliation(s)
- Hengameh Shams
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, California 94720-1762, United States
| | - Mohammad Soheilypour
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, California 94720-1762, United States
| | - Mohaddeseh Peyro
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, California 94720-1762, United States
| | - Ruhollah Moussavi-Baygi
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, California 94720-1762, United States
| | - Mohammad R K Mofrad
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, California 94720-1762, United States
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20
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Sakiyama Y, Panatala R, Lim RYH. Structural dynamics of the nuclear pore complex. Semin Cell Dev Biol 2017; 68:27-33. [PMID: 28579449 DOI: 10.1016/j.semcdb.2017.05.021] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Accepted: 05/29/2017] [Indexed: 11/18/2022]
Abstract
Nuclear pore complexes (NPCs) are the sole conduits that facilitate macromolecular exchange between the nucleus and cytosol. Recent advancements have led to a more highly resolved NPC structure. However, our understanding of the NPC modus operandi that facilitates transport selectivity, and speed, of diverse cargoes remains incomplete. For the most part, assorted cargo-complexes of different sizes traverse the NPC central channel in milliseconds, yet little is known about the nanoscopic movements of its barrier-forming Phe-Gly nucleoporins (FG Nups) and related sub-structures at transport-relevant time and length scales. Here, we discuss how dynamic FG Nup behavior may confer NPCs with an effective permeability barrier according to the functional needs of the cell. Moreover, we postulate that structural flexibility might resonate throughout the NPC framework from the cytoplasmic filaments to the nuclear basket.
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Affiliation(s)
- Yusuke Sakiyama
- Biozentrum and the Swiss Nanoscience Institute, University of Basel, Klingelbergstrasse 70, 4056 Basel, Switzerland
| | - Radhakrishnan Panatala
- Biozentrum and the Swiss Nanoscience Institute, University of Basel, Klingelbergstrasse 70, 4056 Basel, Switzerland
| | - Roderick Y H Lim
- Biozentrum and the Swiss Nanoscience Institute, University of Basel, Klingelbergstrasse 70, 4056 Basel, Switzerland.
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21
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Huang K, Szleifer I. Design of Multifunctional Nanogate in Response to Multiple External Stimuli Using Amphiphilic Diblock Copolymer. J Am Chem Soc 2017; 139:6422-6430. [PMID: 28421749 DOI: 10.1021/jacs.7b02057] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Nature uses the interplay between hydrophobic and electrostatic interactions of disordered proteins to orchestrate complicated molecular gates such as the nuclear pore complex to control the transport of biological masses. Inspired by nature, we here theoretically show that well-defined gate shape, sensitive response to pH and salt concentration, and selectivity in cargo transport can be simultaneously achieved by grafting amphiphilic diblock copolymers made of sequence-controlled hydrophobic and ionizable monomers on the inner surface of solid-state nanopore. As a result, multiple functions such as ionic gating and molecular filtering can be implemented into one single copolymer nanogate. The gate structure and thermodynamics is a result of the self-assembly of the sequence-designed copolymer in the confined geometry that minimizes the free energy of the system. Our theory further predicts a phase transition and discontinuous charge regulation of the confined copolymer that allows logical gating in biosensors and nanofluidic devices. As an example of application, a nanolocker with the potential of molecular pumping has also been designed with the cooperation of two amphiphilic copolymer gates. Our results highlight the importance of polymer sequence in nanogating, and these insights can be used to guide the rational design of polymer-coated smart nanopores.
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Affiliation(s)
- Kai Huang
- Department of Biomedical Engineering, Northwestern University , Evanston, Illinois 60208, United States
| | - Igal Szleifer
- Department of Biomedical Engineering and Department of Chemistry and Chemistry of Life Processes Institute, Northwestern University , Evanston, Illinois 60208, United States
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22
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Ando D, Gopinathan A. Cooperative Interactions between Different Classes of Disordered Proteins Play a Functional Role in the Nuclear Pore Complex of Baker's Yeast. PLoS One 2017; 12:e0169455. [PMID: 28068389 PMCID: PMC5222603 DOI: 10.1371/journal.pone.0169455] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Accepted: 12/16/2016] [Indexed: 12/02/2022] Open
Abstract
Nucleocytoplasmic transport is highly selective, efficient, and is regulated by a poorly understood mechanism involving hundreds of disordered FG nucleoporin proteins (FG nups) lining the inside wall of the nuclear pore complex (NPC). Previous research has concluded that FG nups in Baker's yeast (S. cerevisiae) are present in a bimodal distribution, with the "Forest Model" classifying FG nups as either di-block polymer like "trees" or single-block polymer like "shrubs". Using a combination of coarse-grained modeling and polymer brush modeling, the function of the di-block FG nups has previously been hypothesized in the Di-block Copolymer Brush Gate (DCBG) model to form a higher-order polymer brush architecture which can open and close to regulate transport across the NPC. In this manuscript we work to extend the original DCBG model by first performing coarse grained simulations of the single-block FG nups which confirm that they have a single block polymer structure rather than the di-block structure of tree nups. Our molecular simulations also demonstrate that these single-block FG nups are likely cohesive, compact, collapsed coil polymers, implying that these FG nups are generally localized to their grafting location within the NPC. We find that adding a layer of single-block FG nups to the DCBG model increases the range of cargo sizes which are able to translocate the pore through a cooperative effect involving single-block and di-block FG nups. This effect can explain the puzzling connection between single-block FG nup deletion mutants in S. cerevisiae and the resulting failure of certain large cargo transport through the NPC. Facilitation of large cargo transport via single-block and di-block FG nup cooperativity in the nuclear pore could provide a model mechanism for designing future biomimetic pores of greater applicability.
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Affiliation(s)
- David Ando
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, United States of America
- Joint BioEnergy Institute, Emeryville, CA, United States of America
| | - Ajay Gopinathan
- Department of Physics, University of California, Merced, CA, United States of America
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23
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Sakiyama Y, Mazur A, Kapinos LE, Lim RYH. Spatiotemporal dynamics of the nuclear pore complex transport barrier resolved by high-speed atomic force microscopy. NATURE NANOTECHNOLOGY 2016; 11:719-23. [PMID: 27136131 DOI: 10.1038/nnano.2016.62] [Citation(s) in RCA: 110] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Accepted: 03/15/2016] [Indexed: 05/27/2023]
Abstract
Nuclear pore complexes (NPCs) are biological nanomachines that mediate the bidirectional traffic of macromolecules between the cytoplasm and nucleus in eukaryotic cells. This process involves numerous intrinsically disordered, barrier-forming proteins known as phenylalanine-glycine nucleoporins (FG Nups) that are tethered inside each pore. The selective barrier mechanism has so far remained unresolved because the FG Nups have eluded direct structural analysis within NPCs. Here, high-speed atomic force microscopy is used to visualize the nanoscopic spatiotemporal dynamics of FG Nups inside Xenopus laevis oocyte NPCs at timescales of ∼100 ms. Our results show that the cytoplasmic orifice is circumscribed by highly flexible, dynamically fluctuating FG Nups that rapidly elongate and retract, consistent with the diffusive motion of tethered polypeptide chains. On this basis, intermingling FG Nups exhibit transient entanglements in the central channel, but do not cohere into a tightly crosslinked meshwork. Therefore, the basic functional form of the NPC barrier is comprised of highly dynamic FG Nups that manifest as a central plug or transporter when averaged in space and time.
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Affiliation(s)
- Yusuke Sakiyama
- Biozentrum and the Swiss Nanoscience Institute, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland
| | - Adam Mazur
- Research IT, Biozentrum, University of Basel, CH-4056 Basel, Switzerland
| | - Larisa E Kapinos
- Biozentrum and the Swiss Nanoscience Institute, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland
| | - Roderick Y H Lim
- Biozentrum and the Swiss Nanoscience Institute, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland
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24
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Vovk A, Gu C, Opferman MG, Kapinos LE, Lim RY, Coalson RD, Jasnow D, Zilman A. Simple biophysics underpins collective conformations of the intrinsically disordered proteins of the Nuclear Pore Complex. eLife 2016; 5. [PMID: 27198189 PMCID: PMC4874778 DOI: 10.7554/elife.10785] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Accepted: 03/24/2016] [Indexed: 12/13/2022] Open
Abstract
Nuclear Pore Complexes (NPCs) are key cellular transporter that control nucleocytoplasmic transport in eukaryotic cells, but its transport mechanism is still not understood. The centerpiece of NPC transport is the assembly of intrinsically disordered polypeptides, known as FG nucleoporins, lining its passageway. Their conformations and collective dynamics during transport are difficult to assess in vivo. In vitro investigations provide partially conflicting results, lending support to different models of transport, which invoke various conformational transitions of the FG nucleoporins induced by the cargo-carrying transport proteins. We show that the spatial organization of FG nucleoporin assemblies with the transport proteins can be understood within a first principles biophysical model with a minimal number of key physical variables, such as the average protein interaction strengths and spatial densities. These results address some of the outstanding controversies and suggest how molecularly divergent NPCs in different species can perform essentially the same function. DOI:http://dx.doi.org/10.7554/eLife.10785.001 Animal, plant and fungal cells contain a structure called the nucleus, inside which the genetic material of the cell is stored. For the cell to work properly, certain proteins and other molecules need to be able to enter and exit the nucleus. This transport is carried out by pore-like molecular “devices” known as Nuclear Pore Complexes, whose architecture and mode of operation are unique among cellular transporters. Nuclear Pore Complexes are charged with a daunting task of deciding which of the hundreds of molecules it conducts per second should go through and which should not. Small molecules can pass freely through Nuclear Pore Complexes. However, larger molecules can only pass through the pore efficiently if they are bound to specialized transport proteins that interact with the proteins – called FG nucleoporins – that line the pore. A unique feature of the FG nucleoporins is that, unlike typical proteins, they do not have a defined three-dimensional structure. Instead, they form a soft and pliable lining inside the Nuclear Pore Complex passageway. Exactly how interacting with transport proteins affects the structure and spatial arrangements of the FG nucleoporins in a way that allows them to control transport is not well understood. This is in part because existing experimental techniques are unable to study the structures of the FG nucleoporins in enough detail to track how they change during transport. The complexity and the diversity of the FG nucleoporins also make them difficult to model in detail. Vovk, Gu et al. have developed a theoretical model that is based on just three basic physical properties of the FG nucleoporins – their flexibility, their ability to interact with each other, and their binding with the transport proteins. Future work can refine the model by incorporating further molecular details about the interactions between FG nucleoporins and transport proteins. The predictions made by this simple model agree well with experimental results in a wide range of situations – from single molecules to complex spatial assemblies. They also explain why some of the experimental results appear to contradict each other and suggest how several outstanding controversies in the field can be reconciled. Because the model invokes only fundamental physical principles of FG nucleoporin assemblies, it shows that some of their general properties do not depend on the exact conditions. In particular, this might shed light on why Nuclear Pore Complexes in different organisms perform essentially the same function, although the details of their molecular structure may differ. This also suggests how the FG nucleoporins can be manipulated to build artificial devices based on the same principles. DOI:http://dx.doi.org/10.7554/eLife.10785.002
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Affiliation(s)
- Andrei Vovk
- Department of Physics, University of Toronto, Toronto, Canada
| | - Chad Gu
- Department of Physics, University of Toronto, Toronto, Canada
| | - Michael G Opferman
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, United States
| | - Larisa E Kapinos
- Biozentrum and the Swiss Nanoscience Institute, University of Basel, Basel, Switzerland
| | - Roderick Yh Lim
- Biozentrum and the Swiss Nanoscience Institute, University of Basel, Basel, Switzerland
| | - Rob D Coalson
- Department of Chemistry, University of Pittsburgh, Pittsburgh, United States
| | - David Jasnow
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, United States
| | - Anton Zilman
- Department of Physics, University of Toronto, Toronto, Canada.,Institute for Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Canada
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25
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Zahn R, Osmanović D, Ehret S, Araya Callis C, Frey S, Stewart M, You C, Görlich D, Hoogenboom BW, Richter RP. A physical model describing the interaction of nuclear transport receptors with FG nucleoporin domain assemblies. eLife 2016; 5. [PMID: 27058170 PMCID: PMC4874776 DOI: 10.7554/elife.14119] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Accepted: 04/07/2016] [Indexed: 11/13/2022] Open
Abstract
The permeability barrier of nuclear pore complexes (NPCs) controls bulk nucleocytoplasmic exchange. It consists of nucleoporin domains rich in phenylalanine-glycine motifs (FG domains). As a bottom-up nanoscale model for the permeability barrier, we have used planar films produced with three different end-grafted FG domains, and quantitatively analyzed the binding of two different nuclear transport receptors (NTRs), NTF2 and Importin β, together with the concomitant film thickness changes. NTR binding caused only moderate changes in film thickness; the binding isotherms showed negative cooperativity and could all be mapped onto a single master curve. This universal NTR binding behavior - a key element for the transport selectivity of the NPC - was quantitatively reproduced by a physical model that treats FG domains as regular, flexible polymers, and NTRs as spherical colloids with a homogeneous surface, ignoring the detailed arrangement of interaction sites along FG domains and on the NTR surface.
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Affiliation(s)
- Raphael Zahn
- Biosurfaces Lab, CIC biomaGUNE, San Sebastian, Spain
| | - Dino Osmanović
- London Centre for Nanotechnology, University College London, London, United Kingdom.,Department of Physics and Astronomy, University College London, London, United Kingdom.,Department of Physics, Bar-Ilan University, Ramat Gan, Israel.,Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat Gan, Israel
| | - Severin Ehret
- Biosurfaces Lab, CIC biomaGUNE, San Sebastian, Spain
| | | | - Steffen Frey
- Department of Cellular Logistics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Murray Stewart
- Medical Research Council Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Changjiang You
- Department of Biology, University of Osnabrück, Osnabrück, Germany
| | - Dirk Görlich
- Department of Cellular Logistics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Bart W Hoogenboom
- London Centre for Nanotechnology, University College London, London, United Kingdom.,Department of Physics and Astronomy, University College London, London, United Kingdom
| | - Ralf P Richter
- Biosurfaces Lab, CIC biomaGUNE, San Sebastian, Spain.,Laboratory of Interdisciplinary Physics, University Grenoble Alpes - CNRS, Grenoble, France.,Max-Planck-Institute for Intelligent Systems, Stuttgart, Germany
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26
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Osmanović D, Kerr-Winter M, Eccleston RC, Hoogenboom BW, Ford IJ. Effects of rotational symmetry breaking in polymer-coated nanopores. J Chem Phys 2015; 142:034901. [DOI: 10.1063/1.4905719] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- D. Osmanović
- London Centre for Nanotechnology (LCN) and Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - M. Kerr-Winter
- Centre for Mathematics, Physics and Engineering in the Life Sciences and Experimental Biology, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - R. C. Eccleston
- Centre for Mathematics, Physics and Engineering in the Life Sciences and Experimental Biology, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - B. W. Hoogenboom
- London Centre for Nanotechnology (LCN) and Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - I. J. Ford
- London Centre for Nanotechnology (LCN) and Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
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27
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Bestembayeva A, Kramer A, Labokha AA, Osmanović D, Liashkovich I, Orlova EV, Ford IJ, Charras G, Fassati A, Hoogenboom BW. Nanoscale stiffness topography reveals structure and mechanics of the transport barrier in intact nuclear pore complexes. NATURE NANOTECHNOLOGY 2015; 10:60-64. [PMID: 25420031 PMCID: PMC4286247 DOI: 10.1038/nnano.2014.262] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2013] [Accepted: 10/13/2014] [Indexed: 05/17/2023]
Abstract
The nuclear pore complex (NPC) is the gate for transport between the cell nucleus and the cytoplasm. Small molecules cross the NPC by passive diffusion, but molecules larger than ∼5 nm must bind to nuclear transport receptors to overcome a selective barrier within the NPC. Although the structure and shape of the cytoplasmic ring of the NPC are relatively well characterized, the selective barrier is situated deep within the central channel of the NPC and depends critically on unstructured nuclear pore proteins, and is therefore not well understood. Here, we show that stiffness topography with sharp atomic force microscopy tips can generate nanoscale cross-sections of the NPC. The cross-sections reveal two distinct structures, a cytoplasmic ring and a central plug structure, which are consistent with the three-dimensional NPC structure derived from electron microscopy. The central plug persists after reactivation of the transport cycle and resultant cargo release, indicating that the plug is an intrinsic part of the NPC barrier. Added nuclear transport receptors accumulate on the intact transport barrier and lead to a homogenization of the barrier stiffness. The observed nanomechanical properties in the NPC indicate the presence of a cohesive barrier to transport and are quantitatively consistent with the presence of a central condensate of nuclear pore proteins in the NPC channel.
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Affiliation(s)
- Aizhan Bestembayeva
- London Centre for Nanotechnology, University College London, 17-19 Gordon Street, London WC1H 0AH, United Kingdom
- Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Armin Kramer
- London Centre for Nanotechnology, University College London, 17-19 Gordon Street, London WC1H 0AH, United Kingdom
- Institute of Physiology II, University of Münster, Robert-Koch Strasse 27b, 48149 Münster, Germany
| | - Aksana A. Labokha
- Wohl Virion Centre, Division of Infection & Immunity, MRC Centre for Medical Molecular Virology, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Dino Osmanović
- London Centre for Nanotechnology, University College London, 17-19 Gordon Street, London WC1H 0AH, United Kingdom
- Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Ivan Liashkovich
- Institute of Physiology II, University of Münster, Robert-Koch Strasse 27b, 48149 Münster, Germany
| | - Elena V. Orlova
- Department of Biological Sciences, Birkbeck College, Institute of Structural and Molecular Biology, Malet Street, London WC1E 7HX, United Kingdom
| | - Ian J. Ford
- London Centre for Nanotechnology, University College London, 17-19 Gordon Street, London WC1H 0AH, United Kingdom
- Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Guillaume Charras
- London Centre for Nanotechnology, University College London, 17-19 Gordon Street, London WC1H 0AH, United Kingdom
- Department of Cell and Developmental Biology, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Ariberto Fassati
- Wohl Virion Centre, Division of Infection & Immunity, MRC Centre for Medical Molecular Virology, University College London, Gower Street, London WC1E 6BT, United Kingdom
- Correspondence and requests for materials should be addressed to A.F. () and B.W.H. ()
| | - Bart W. Hoogenboom
- London Centre for Nanotechnology, University College London, 17-19 Gordon Street, London WC1H 0AH, United Kingdom
- Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
- Correspondence and requests for materials should be addressed to A.F. () and B.W.H. ()
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Osmanović D, Ford IJ, Hoogenboom BW. Model inspired by nuclear pore complex suggests possible roles for nuclear transport receptors in determining its structure. Biophys J 2014; 105:2781-9. [PMID: 24359750 DOI: 10.1016/j.bpj.2013.11.013] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Revised: 10/25/2013] [Accepted: 11/04/2013] [Indexed: 12/20/2022] Open
Abstract
Nuclear transport receptors (NTRs) mediate nucleocytoplasmic transport via their affinity for unstructured proteins (polymers) in the nuclear pore complex (NPC). Here, we have modeled the effect of NTRs on polymeric structure in the nanopore confinement of the NPC central conduit. The model explicitly takes into account inter- and intramolecular interactions, as well as the finite size of the NTRs (∼20% of the NPC channel diameter). It reproduces various proposed scenarios for the channel structure, ranging from a central polymer condensate (selective phase) to brushlike polymer arrangements localized at the channel wall (virtual gate, reduction of dimensionality), with the transport receptors lining the polymer surface. In addition, it predicts a new structure in which NTRs become an integral part of the transport barrier by forming a cross-linked network with the unstructured proteins stretching across the pore. The model provides specific and distinctive predictions for the equilibrium spatial distributions of NTRs for these different scenarios that can be experimentally verified by, e.g., superresolution fluorescence microscopy. Moreover, it suggests mechanisms by which globular macromolecules (colloidal particles) can cause polymer-coated nanopores to switch between open and closed configurations, a possible explanation of the biological function of the NPC, and suggests potential technological applications for filtration and single-molecule sensing.
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Affiliation(s)
- Dino Osmanović
- London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, London, United Kingdom.
| | - Ian J Ford
- London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, London, United Kingdom
| | - Bart W Hoogenboom
- London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, London, United Kingdom
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Eisele NB, Labokha AA, Frey S, Görlich D, Richter RP. Cohesiveness tunes assembly and morphology of FG nucleoporin domain meshworks - Implications for nuclear pore permeability. Biophys J 2014; 105:1860-70. [PMID: 24138862 DOI: 10.1016/j.bpj.2013.09.006] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Revised: 08/25/2013] [Accepted: 09/04/2013] [Indexed: 12/20/2022] Open
Abstract
Nuclear pore complexes control the exchange of macromolecules between the cytoplasm and the nucleus. A selective permeability barrier that arises from a supramolecular assembly of intrinsically unfolded nucleoporin domains rich in phenylalanine-glycine dipeptides (FG domains) fills the nuclear pore. There is increasing evidence that selective transport requires cohesive FG domain interactions. To understand the functional roles of cohesive interactions, we studied monolayers of end-grafted FG domains as a bottom-up nanoscale model system of the permeability barrier. Based on detailed physicochemical analysis of the model films and comparison of the data with polymer theory, we propose that cohesiveness is tuned to promote rapid assembly of the permeability barrier and to generate a stable and compact pore-filling meshwork with a small mesh size. Our results highlight the functional importance of weak interactions, typically a few kBT per chain, and contribute important information to understand the mechanism of size-selective transport.
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Affiliation(s)
- Nico B Eisele
- Biosurfaces Unit, CIC biomaGUNE, San Sebastian, Spain; Department of Cellular Logistics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
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Ando D, Zandi R, Kim YW, Colvin M, Rexach M, Gopinathan A. Nuclear pore complex protein sequences determine overall copolymer brush structure and function. Biophys J 2014; 106:1997-2007. [PMID: 24806932 PMCID: PMC4017316 DOI: 10.1016/j.bpj.2014.03.021] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Revised: 03/07/2014] [Accepted: 03/11/2014] [Indexed: 11/15/2022] Open
Abstract
The transport of cargo across the nuclear membrane is highly selective and accomplished by a poorly understood mechanism involving hundreds of nucleoporins lining the inside of the nuclear pore complex (NPC). Currently, there is no clear picture of the overall structure formed by this collection of proteins within the pore, primarily due to their disordered nature. We perform coarse-grained simulations of both individual nucleoporins and grafted rings of nups mimicking the in vivo geometry of the NPC and supplement this with polymer brush modeling. Our results indicate that different regions or blocks of an individual NPC protein can have distinctly different forms of disorder and that this property appears to be a conserved functional feature. Furthermore, this block structure at the individual protein level is critical to the formation of a unique higher-order polymer brush architecture that can exist in distinct morphologies depending on the effective interaction energy between the phenylalanine glycine (FG) domains of different nups. Because the interactions between FG domains may be modulated by certain forms of transport factors, our results indicate that transitions between brush morphologies could play an important role in regulating transport across the NPC, suggesting novel forms of gated transport across membrane pores with wide biomimetic applicability.
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Affiliation(s)
- David Ando
- Department of Physics, University of California at Merced, Merced, California
| | - Roya Zandi
- Department of Physics, University of California at Riverside, Riverside, California
| | - Yong Woon Kim
- Graduate School of Nanoscience and Technology, Korea Advanced Institute of Science and Technology, Daejeon, Korea
| | - Michael Colvin
- Department of Chemistry and Chemical Biology, University of California at Merced, Merced, California
| | - Michael Rexach
- Department of Molecular, Cell, and Developmental Biology, University of California at Santa Cruz, Santa Cruz, California
| | - Ajay Gopinathan
- Department of Physics, University of California at Merced, Merced, California.
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Milchev A, Müller M, Klushin L. Arm Retraction Dynamics and Bistability of a Three-Arm Star Polymer in a Nanopore. Macromolecules 2014. [DOI: 10.1021/ma500053n] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- A. Milchev
- Institute
for Physical Chemistry, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
- Institut für Theoretische Physik, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - M. Müller
- Institut für Theoretische Physik, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - L. Klushin
- Department
of Physics, American University of Beirut, Beirut, Lebanon
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32
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Osmanović D, Fassati A, Ford IJ, Hoogenboom BW. Physical modelling of the nuclear pore complex. SOFT MATTER 2013; 9:10442. [PMCID: PMC4046875 DOI: 10.1039/c3sm50722j] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2013] [Accepted: 07/18/2013] [Indexed: 05/24/2023]
Abstract
An in-depth discussion of nuclear pore complexes illustrates the importance of macromolecular confinement in biological systems.
Physically interesting behaviour can arise when soft matter is confined to nanoscale dimensions. A highly relevant biological example of such a phenomenon is the Nuclear Pore Complex (NPC) found perforating the nuclear envelope of eukaryotic cells. In the central conduit of the NPC, of ∼30–60 nm diameter, a disordered network of proteins regulates all macromolecular transport between the nucleus and the cytoplasm. In spite of a wealth of experimental data, the selectivity barrier of the NPC has yet to be explained fully. Experimental and theoretical approaches are complicated by the disordered and heterogeneous nature of the NPC conduit. Modelling approaches have focused on the behaviour of the partially unfolded protein domains in the confined geometry of the NPC conduit, and have demonstrated that within the range of parameters thought relevant for the NPC, widely varying behaviour can be observed. In this review, we summarise recent efforts to physically model the NPC barrier and function. We illustrate how attempts to understand NPC barrier function have employed many different modelling techniques, each of which have contributed to our understanding of the NPC.
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Affiliation(s)
- Dino Osmanović
- London Centre for Nanotechnology and Department of Physics and Astronomy , University College London , Gower Street , WC1E 6BT , UK .
| | - Ariberto Fassati
- Wohl Virion Centre and MRC Centre for Medical Molecular Virology , University College London , Gower Street , WC1E 6BT , UK
| | - Ian J. Ford
- London Centre for Nanotechnology and Department of Physics and Astronomy , University College London , Gower Street , WC1E 6BT , UK .
| | - Bart W. Hoogenboom
- London Centre for Nanotechnology and Department of Physics and Astronomy , University College London , Gower Street , WC1E 6BT , UK .
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Labokha AA, Fassati A. Viruses challenge selectivity barrier of nuclear pores. Viruses 2013; 5:2410-23. [PMID: 24084236 PMCID: PMC3814595 DOI: 10.3390/v5102410] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Revised: 09/24/2013] [Accepted: 09/25/2013] [Indexed: 01/04/2023] Open
Abstract
Exchange between the nucleus and the cytoplasm occurs through nuclear pore complexes (NPCs) embedded in the double membrane of the nuclear envelope. NPC permeability barrier restricts the entry of inert molecules larger than 5 nm in diameter but allows facilitated entry of selected cargos, whose size can reach up to 39 nm. The translocation of large molecules is facilitated by nuclear transport receptors (NTRs) that have affinity to proteins of NPC permeability barrier. Viruses that enter the nucleus replicate evolved strategies to overcome this barrier. In this review, we will discuss the functional principles of NPC barrier and nuclear transport machinery, as well as the various strategies viruses use to cross the selective barrier of NPCs.
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Affiliation(s)
- Aksana A. Labokha
- Authors to whom correspondence should be addressed; E-Mails: (A.A.L.); (A.F.); Tel.: (+44(0)2031082141); Fax: (+44(0)2031082123); Tel.: (+44(0)2031082138); Fax: (+44(0)2031082123)
| | - Ariberto Fassati
- Authors to whom correspondence should be addressed; E-Mails: (A.A.L.); (A.F.); Tel.: (+44(0)2031082141); Fax: (+44(0)2031082123); Tel.: (+44(0)2031082138); Fax: (+44(0)2031082123)
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