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Raveh B, Eliasian R, Rashkovits S, Russel D, Hayama R, Sparks SE, Singh D, Lim R, Villa E, Rout MP, Cowburn D, Sali A. Integrative spatiotemporal map of nucleocytoplasmic transport. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.12.31.573409. [PMID: 38260487 PMCID: PMC10802240 DOI: 10.1101/2023.12.31.573409] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
The Nuclear Pore Complex (NPC) facilitates rapid and selective nucleocytoplasmic transport of molecules as large as ribosomal subunits and viral capsids. It is not clear how key emergent properties of this transport arise from the system components and their interactions. To address this question, we constructed an integrative coarse-grained Brownian dynamics model of transport through a single NPC, followed by coupling it with a kinetic model of Ran-dependent transport in an entire cell. The microscopic model parameters were fitted to reflect experimental data and theoretical information regarding the transport, without making any assumptions about its emergent properties. The resulting reductionist model is validated by reproducing several features of transport not used for its construction, such as the morphology of the central transporter, rates of passive and facilitated diffusion as a function of size and valency, in situ radial distributions of pre-ribosomal subunits, and active transport rates for viral capsids. The model suggests that the NPC functions essentially as a virtual gate whose flexible phenylalanine-glycine (FG) repeat proteins raise an entropy barrier to diffusion through the pore. Importantly, this core functionality is greatly enhanced by several key design features, including 'fuzzy' and transient interactions, multivalency, redundancy in the copy number of FG nucleoporins, exponential coupling of transport kinetics and thermodynamics in accordance with the transition state theory, and coupling to the energy-reliant RanGTP concentration gradient. These design features result in the robust and resilient rate and selectivity of transport for a wide array of cargo ranging from a few kilodaltons to megadaltons in size. By dissecting these features, our model provides a quantitative starting point for rationally modulating the transport system and its artificial mimics.
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2
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Patel MK, Chakrabarti B, Panwar AS. Emergence of selectivity and specificity in a coarse-grained model of the nuclear pore complex with sequence-agnostic FG-Nups. Phys Chem Chem Phys 2023; 25:32824-32836. [PMID: 38018404 DOI: 10.1039/d3cp03746k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2023]
Abstract
The role of hydrophobicity of phenylalanine-glycine nucleoporins (FG-Nups) in determining the transport of receptor-bound cargo across the nuclear pore complex (NPC) is investigated using Langevin dynamics simulations. A coarse-grained, minimal model of the NPC, comprising a cylindrical pore and hydrophobic-hydrophilic random copolymers for FG-Nups was employed. Karyopherin-bound receptor-cargo complexes (Kaps) were modeled as rigid, coarse-grained spheres without (inert) and with (patchy) FG-binding hydrophobic domains. With a sequence-agnostic description of FG-Nups and the absence of any anisotropies associated with either NPC or cargo, the model described tracer transport only as a function of FG-Nup hydrophobicity, f. The simulations showed the emergence of two important features of cargo transport, namely, NPC selectivity and specificity. NPC selectivity to patchy tracers emerged due to hydrophobic Kap-FG interactions and despite the sequence-agnostic description of FG-Nups. Furthermore, NPC selectivity was observed only in a specific range of FG-hydrophobic fraction, 0.05 ≤ f ≤ 0.20, resulting in specificity of NPC transport with respect to f. Significantly, this range corresponded to the number fraction of FG-repeats observed in both S. cerevisiae and H. sapiens NPCs. This established the central role of the FG-hydrophobic fraction in determining NPC transport, and provided a biophysical basis for conservation of the FG-Nup hydrophobic fraction across evolutionarily distant NPCs. Specificity in NPC transport emerged from the formation of a hydrogel-like network inside the pore with a characteristic mesh size dependent on f. This network rejected cargo for f > 0.2 based on size exclusion, which resulted in enhanced translocation probability for 0.05 ≤ f ≤ 0.20. Extended brush configurations outside the pore resulted in entropic repulsion and exclusion of inert cargo in this range. Thus, our minimal NPC model exhibited a hybrid cargo translocation mechanism, with aspects of both virtual gate and selective-phase models, in this range of FG-hydrophobic fraction.
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Affiliation(s)
- Manoj K Patel
- Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
| | | | - Ajay S Panwar
- Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
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3
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Rush C, Jiang Z, Tingey M, Feng F, Yang W. Unveiling the complexity: assessing models describing the structure and function of the nuclear pore complex. Front Cell Dev Biol 2023; 11:1245939. [PMID: 37876551 PMCID: PMC10591098 DOI: 10.3389/fcell.2023.1245939] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2023] [Accepted: 09/19/2023] [Indexed: 10/26/2023] Open
Abstract
The nuclear pore complex (NPC) serves as a pivotal subcellular structure, acting as a gateway that orchestrates nucleocytoplasmic transport through a selectively permeable barrier. Nucleoporins (Nups), particularly those containing phenylalanine-glycine (FG) motifs, play indispensable roles within this barrier. Recent advancements in technology have significantly deepened our understanding of the NPC's architecture and operational intricacies, owing to comprehensive investigations. Nevertheless, the conspicuous presence of intrinsically disordered regions within FG-Nups continues to present a formidable challenge to conventional static characterization techniques. Historically, a multitude of strategies have been employed to unravel the intricate organization and behavior of FG-Nups within the NPC. These endeavors have given rise to multiple models that strive to elucidate the structural layout and functional significance of FG-Nups. Within this exhaustive review, we present a comprehensive overview of these prominent models, underscoring their proposed dynamic and structural attributes, supported by pertinent research. Through a comparative analysis, we endeavor to shed light on the distinct characteristics and contributions inherent in each model. Simultaneously, it remains crucial to acknowledge the scarcity of unequivocal validation for any of these models, as substantiated by empirical evidence.
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Affiliation(s)
| | | | | | | | - Weidong Yang
- Department of Biology, Temple University, Philadelphia, PA, United States
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4
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Han L, Zhou Y, Tan Z, Zhu H, Hu Y, Ma X, Zheng F, Feng F, Wang C, Liu W. Confined Target-Triggered Hot Spots for In Situ SERS Analysis of Intranuclear Genotoxic Markers. Anal Chem 2023; 95:6312-6322. [PMID: 37000898 DOI: 10.1021/acs.analchem.2c05147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/03/2023]
Abstract
The γH2AX is a type of confined target in nuclei which is highly expressed around the damaged DNA during genotoxicity and has therefore been identified as a marker of genotoxicity. Convenient and intuitive in situ real-time detection of γH2AX is crucial for an accurate assessment of genotoxicity. Selective and nondestructive surface-enhanced Raman spectroscopy (SERS) is suitable to achieve this goal. However, the detection of substances in the nucleus by SERS is still limited due to the contradiction of probes between the nuclei entry efficiency and signal enhancement. This study utilized the characteristics of γH2AX as a confined target and constructed a γH2AX immunosensor based on gold nanoprobes with a small size (15 nm), which was modified with the TAT nuclear targeting peptide to ensure high nuclei entry efficiency. Once DNA damage was induced, the local overexpression of γH2AX further recruited the probe through immune recognition, so that hot spots could be assembled in situ to generate strong Raman signals, which were applied to evaluate the genotoxicity of drug impurities. This study proposed a novel SERS detection strategy, characterized by confined target-induced size conversion and hot spot formation, for in situ real-time analysis of intranuclear targets at the single-living-cell level, which intelligently simplified the structure of SERS probes and the operation process.
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5
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Nag N, Sasidharan S, Uversky VN, Saudagar P, Tripathi T. Phase separation of FG-nucleoporins in nuclear pore complexes. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2022; 1869:119205. [PMID: 34995711 DOI: 10.1016/j.bbamcr.2021.119205] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Revised: 12/14/2021] [Accepted: 12/23/2021] [Indexed: 12/11/2022]
Abstract
The nuclear envelope (NE) is a bilayer membrane that separates and physically isolates the genetic material from the cytoplasm. Nuclear pore complexes (NPCs) are cylindrical structures embedded in the NE and remain the sole channel of communication between the nucleus and the cytoplasm. The interior of NPCs contains densely packed intrinsically disordered FG-nucleoporins (FG-Nups), consequently forming a permeability barrier. This barrier facilitates the selection and specificity of the cargoes that are imported, exported, or shuttled through the NPCs. Recent studies have revealed that FG-Nups undergo the process of liquid-liquid phase separation into liquid droplets. Moreover, these liquid droplets mimic the permeability barrier observed in the interior of NPCs. This review highlights the phase separation of FG-Nups occurring inside the NPCs rooted in the NE. We discuss the phase separation of FG-Nups and compare the different aspects contributing to their phase separation. Furthermore, several diseases caused by the aberrant phase separation of the proteins are examined with respect to NEs. By understanding the fundamental process of phase separation at the nuclear membrane, the review seeks to explore the parameters influencing this phenomenon as well as its importance, ultimately paving the way for better research on the structure-function relationship of biomolecular condensates.
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Affiliation(s)
- Niharika Nag
- Molecular and Structural Biophysics Laboratory, Department of Biochemistry, North-Eastern Hill University, Shillong 793022, India
| | - Santanu Sasidharan
- Department of Biotechnology, National Institute of Technology Warangal, Warangal 506004, India
| | - Vladimir N Uversky
- Department of Molecular Medicine and Byrd Alzheimer's Research Institute, Morsani College of Medicine, University of South Florida, Tampa, FL 33620, United States; Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Institutskiy pereulok, 9, Dolgoprudny, Moscow Region 141700, Russia
| | - Prakash Saudagar
- Department of Biotechnology, National Institute of Technology Warangal, Warangal 506004, India.
| | - Timir Tripathi
- Molecular and Structural Biophysics Laboratory, Department of Biochemistry, North-Eastern Hill University, Shillong 793022, India.
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6
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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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7
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Raices M, D'Angelo MA. Structure, Maintenance, and Regulation of Nuclear Pore Complexes: The Gatekeepers of the Eukaryotic Genome. Cold Spring Harb Perspect Biol 2022; 14:a040691. [PMID: 34312247 PMCID: PMC8789946 DOI: 10.1101/cshperspect.a040691] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
In eukaryotic cells, the genetic material is segregated inside the nucleus. This compartmentalization of the genome requires a transport system that allows cells to move molecules across the nuclear envelope, the membrane-based barrier that surrounds the chromosomes. Nuclear pore complexes (NPCs) are the central component of the nuclear transport machinery. These large protein channels penetrate the nuclear envelope, creating a passage between the nucleus and the cytoplasm through which nucleocytoplasmic molecule exchange occurs. NPCs are one of the largest protein assemblies of eukaryotic cells and, in addition to their critical function in nuclear transport, these structures also play key roles in many cellular processes in a transport-independent manner. Here we will review the current knowledge of the NPC structure, the cellular mechanisms that regulate their formation and maintenance, and we will provide a brief description of a variety of processes that NPCs regulate.
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Affiliation(s)
- Marcela Raices
- Cell and Molecular Biology of Cancer Program, NCI-Designated Cancer Center, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California 92037, USA
| | - Maximiliano A D'Angelo
- Cell and Molecular Biology of Cancer Program, NCI-Designated Cancer Center, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California 92037, USA
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8
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Corti HR, Appignanesi GA, Barbosa MC, Bordin JR, Calero C, Camisasca G, Elola MD, Franzese G, Gallo P, Hassanali A, Huang K, Laria D, Menéndez CA, de Oca JMM, Longinotti MP, Rodriguez J, Rovere M, Scherlis D, Szleifer I. Structure and dynamics of nanoconfined water and aqueous solutions. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2021; 44:136. [PMID: 34779954 DOI: 10.1140/epje/s10189-021-00136-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Accepted: 10/06/2021] [Indexed: 06/13/2023]
Abstract
This review is devoted to discussing recent progress on the structure, thermodynamic, reactivity, and dynamics of water and aqueous systems confined within different types of nanopores, synthetic and biological. Currently, this is a branch of water science that has attracted enormous attention of researchers from different fields interested to extend the understanding of the anomalous properties of bulk water to the nanoscopic domain. From a fundamental perspective, the interactions of water and solutes with a confining surface dramatically modify the liquid's structure and, consequently, both its thermodynamical and dynamical behaviors, breaking the validity of the classical thermodynamic and phenomenological description of the transport properties of aqueous systems. Additionally, man-made nanopores and porous materials have emerged as promising solutions to challenging problems such as water purification, biosensing, nanofluidic logic and gating, and energy storage and conversion, while aquaporin, ion channels, and nuclear pore complex nanopores regulate many biological functions such as the conduction of water, the generation of action potentials, and the storage of genetic material. In this work, the more recent experimental and molecular simulations advances in this exciting and rapidly evolving field will be reported and critically discussed.
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Affiliation(s)
- Horacio R Corti
- Departmento de Física de la Materia Condensada & Instituto de Nanociencia y Nanotecnología (CNEA-CONICET), Comisión Nacional de Energía Atómica, B1650LWP, Buenos Aires, Argentina.
| | - Gustavo A Appignanesi
- INQUISUR, Departamento de Química, Universidad Nacional del Sur (UNS)-CONICET, 8000, Bahía Blanca, Argentina
| | - Marcia C Barbosa
- Institute of Physics, Federal University of Rio Grande do Sul, 91501-970, Porto Alegre, Brazil
| | - J Rafael Bordin
- Department of Physics, Institute of Physics and Mathematics, 96050-500, Pelotas, RS, Brazil
| | - Carles Calero
- Secció de Física Estadística i Interdisciplinària - Departament de Física de la Matèria Condensada, Universitat de Barcelona & Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, 08028, Barcelona, Spain
| | - Gaia Camisasca
- Dipartimento di Matematica e Fisica, Università degli Studi Roma Tre, 00146, Roma, Italy
| | - M Dolores Elola
- Departmento de Física de la Materia Condensada & Instituto de Nanociencia y Nanotecnología (CNEA-CONICET), Comisión Nacional de Energía Atómica, B1650LWP, Buenos Aires, Argentina
| | - Giancarlo Franzese
- Secció de Física Estadística i Interdisciplinària - Departament de Física de la Matèria Condensada, Universitat de Barcelona & Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, 08028, Barcelona, Spain
| | - Paola Gallo
- Dipartimento di Matematica e Fisica, Università degli Studi Roma Tre, 00146, Roma, Italy
| | - Ali Hassanali
- Condensed Matter and Statistical Physics Section (CMSP), The International Center for Theoretical Physics (ICTP), Trieste, Italy
| | - Kai Huang
- Institute of Systems and Physical Biology, Shenzhen Bay Laboratory, Shenzhen, Guangdong, China
| | - Daniel Laria
- Departmento de Física de la Materia Condensada & Instituto de Nanociencia y Nanotecnología (CNEA-CONICET), Comisión Nacional de Energía Atómica, B1650LWP, Buenos Aires, Argentina
- Instituto de Química Física de los Materiales, Medio Ambiente y Energía (INQUIMAE-CONICET), Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Cintia A Menéndez
- INQUISUR, Departamento de Química, Universidad Nacional del Sur (UNS)-CONICET, 8000, Bahía Blanca, Argentina
| | - Joan M Montes de Oca
- INQUISUR, Departamento de Química, Universidad Nacional del Sur (UNS)-CONICET, 8000, Bahía Blanca, Argentina
| | - M Paula Longinotti
- Instituto de Química Física de los Materiales, Medio Ambiente y Energía (INQUIMAE-CONICET), Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Javier Rodriguez
- Departmento de Física de la Materia Condensada & Instituto de Nanociencia y Nanotecnología (CNEA-CONICET), Comisión Nacional de Energía Atómica, B1650LWP, Buenos Aires, Argentina
- Escuela de Ciencia y Tecnología, Universidad Nacional de General San Martín, San Martín, Buenos Aires, Argentina
| | - Mauro Rovere
- Dipartimento di Matematica e Fisica, Università degli Studi Roma Tre, 00146, Roma, Italy
| | - Damián Scherlis
- Instituto de Química Física de los Materiales, Medio Ambiente y Energía (INQUIMAE-CONICET), Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Igal Szleifer
- Biomedical Engineering Department, Northwestern University, Evanston, USA
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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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10
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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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Koo K, Lalitha Sridhar S, Clark N, Vernerey F, Hough L. Moving while you're stuck: a macroscopic demonstration of an active system inspired by binding-mediated transport in biology. SOFT MATTER 2021; 17:2957-2962. [PMID: 33595051 PMCID: PMC9205265 DOI: 10.1039/d0sm01808b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Diffusive motion is typically constrained when particles bind to the medium through which they move. However, when binding is transient and the medium is made of flexible filaments, each association or dissociation event produces a stochastic force that can overcome the medium stickiness and enable motion. This mechanism is amply used by biological systems where the act of balancing binding and displacement robustly achieves key functionalities, including bacterial locomotion or selective active filtering in cells. Here we demonstrate the feasibility of making a dynamic system with macroscopic features, in which analogous binding-mediated motion can be actively driven, precisely tuned, and conveniently studied. We find an optimal binding affinity and number of binding sites for diffusive motion, and an inverse relationship between viscosity and diffusivity.
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Affiliation(s)
- Kanghyeon Koo
- Civil, Environmental and Architectural Engineering, University of Colorado Boulder, Boulder, CO 80309, USA
| | - Shankar Lalitha Sridhar
- Mechanical Engineering, University of Colorado Boulder, Boulder, CO 80309, USA. and BioFrontiers Institute, University of Colorado, Boulder, USA
| | - Noel Clark
- Department of Physics, University of Colorado Boulder, Boulder, CO 80309, USA.
| | - Franck Vernerey
- Mechanical Engineering, University of Colorado Boulder, Boulder, CO 80309, USA.
| | - Loren Hough
- BioFrontiers Institute, University of Colorado, Boulder, USA and Department of Physics, University of Colorado Boulder, Boulder, CO 80309, USA.
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Lalitha Sridhar S, Dunagin J, Koo K, Hough L, Vernerey F. Enhanced Diffusion by Reversible Binding to Active Polymers. Macromolecules 2021; 54:1850-1858. [PMID: 35663922 PMCID: PMC9161825 DOI: 10.1021/acs.macromol.0c02306] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Cells are known to use reversible binding to active biopolymer networks to allow diffusive transport of particles in an otherwise impenetrable mesh. We here determine the motion of a particle that experiences random forces during binding and unbinding events while being constrained by attached polymers. Using Monte-Carlo simulations and a statistical mechanics model, we find that enhanced diffusion is possible with active polymers. However, this is possible only under optimum conditions that has to do with the relative length of the chains to that of the plate. For example, in systems where the plate is shorter than the chains, diffusion is maximum when many chains have the potential to bind but few remain bound at any one time. Interestingly, if the chains are shorter than the plate, we find that diffusion is maximized when more active chains remain transiently bound. The model provides insight into these findings by elucidating the mechanisms for binding-mediated diffusion in biology and design rules for macromolecular transport in transient synthetic polymers.
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Affiliation(s)
- Shankar Lalitha Sridhar
- Department of Mechanical Engineering, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Jeffrey Dunagin
- Department of Physics, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Kanghyeon Koo
- Civil, Environmental and Architectural Engineering, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Loren Hough
- Department of Physics, University of Colorado Boulder, Boulder, Colorado 80309, United States
- BioFrontiers Institute, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Franck Vernerey
- Department of Mechanical Engineering, University of Colorado Boulder, Boulder, Colorado 80309, United States
- Materials Science and Engineering Program, University of Colorado Boulder, Boulder, Colorado 80309, United States
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13
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Carbon Nanodots for On Demand Chemophotothermal Therapy Combination to Elicit Necroptosis: Overcoming Apoptosis Resistance in Breast Cancer Cell Lines. Cancers (Basel) 2020; 12:cancers12113114. [PMID: 33113761 PMCID: PMC7692354 DOI: 10.3390/cancers12113114] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2020] [Revised: 10/20/2020] [Accepted: 10/21/2020] [Indexed: 12/12/2022] Open
Abstract
Simple Summary Carbon nanodots (CDs) are considered a versatile family of fluorescent, near infrared (NIR) active, and bioeliminable nanoparticles. Accordingly, the CDs application in photothermal therapy and theranostics increased. Problems limiting their use arise from the heterogeneity of most CDs and the lack of exhaustive information on their nanotoxicity at cellular and molecular levels. The lack of these data is often quite dramatic and causes substantial loss of translational value. To overcome this, we developed biocompatible homogenous CDs with a well-known structure as well as efficient red fluorescence and NIR photothermal conversion. The controlled photothermal effect and the on-demand release of the irinotecan successfully kill breast cancer cell lines in absence of relevant cell stress after internalization. We believe that these results provide insights to advance the field with significant impact, paving the way for the design of effective and safe nanomedicines for precision photothermal cancer therapies. Abstract Background: Engineered luminescent carbon nanodots (CDs) are appealing nanomaterials for cancer image-guided photothermal therapy combining near infrared (NIR)–triggered hyperthermia, imaging, and drug delivery in a single platform for efficient killing of cancer cells. This approach would allow eliciting synergistic regulated cell death (RCD) routes such as necroptosis, targeting breast cancer cells refractory to apoptosis, thus overcoming drug resistance. Methods: We report the preparation of CDs bearing biotin as a targeting agent (CDs-PEG-BT), which are able to load high amounts of irinotecan (23.7%) to be released in a pulsed on-demand fashion. CDs-PEG-BT have narrow size distribution, stable red luminescence, and high photothermal conversion in the NIR region, allowing imaging of MDA-MB231 and MCF-7 cancer cells and killing them by photothermal and chemotherapeutic insults. Results: Cellular uptake, viability profiles, and RCD gene expression analyses provided insights about the observed biocompatibility of CDs-PEG-BT, indicating that necroptosis can be induced on-demand after the photothermal activation. Besides, photothermal activation of drug-loaded CDs-PEG-BT implies both necroptosis and apoptosis by the TNFα and RIPK1 pathway. Conclusions: The controlled activation of necroptosis and apoptosis by combining phototherapy and on-demand release of irinotecan is the hallmark of efficient anticancer response in refractory breast cancer cell lines in view of precision medicine applications.
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14
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Theoretical Modeling of Chemical Equilibrium in Weak Polyelectrolyte Layers on Curved Nanosystems. Polymers (Basel) 2020; 12:polym12102282. [PMID: 33027995 PMCID: PMC7601300 DOI: 10.3390/polym12102282] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 09/24/2020] [Accepted: 09/24/2020] [Indexed: 12/19/2022] Open
Abstract
Surface functionalization with end-tethered weak polyelectrolytes (PE) is a versatile way to modify and control surface properties, given their ability to alter their degree of charge depending on external cues like pH and salt concentration. Weak PEs find usage in a wide range of applications, from colloidal stabilization, lubrication, adhesion, wetting to biomedical applications such as drug delivery and theranostics applications. They are also ubiquitous in many biological systems. Here, we present an overview of some of the main theoretical methods that we consider key in the field of weak PE at interfaces. Several applications involving engineered nanoparticles, synthetic and biological nanopores, as well as biological macromolecules are discussed to illustrate the salient features of systems involving weak PE near an interface or under (nano)confinement. The key feature is that by confining weak PEs near an interface the degree of charge is different from what would be expected in solution. This is the result of the strong coupling between structural organization of weak PE and its chemical state. The responsiveness of engineered and biological nanomaterials comprising weak PE combined with an adequate level of modeling can provide the keys to a rational design of smart nanosystems.
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15
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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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16
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Maguire L, Betterton MD, Hough LE. Bound-State Diffusion due to Binding to Flexible Polymers in a Selective Biofilter. Biophys J 2019; 118:376-385. [PMID: 31858976 DOI: 10.1016/j.bpj.2019.11.026] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Revised: 11/05/2019] [Accepted: 11/14/2019] [Indexed: 01/02/2023] Open
Abstract
Selective biofilters are used by cells to control the transport of proteins, nucleic acids, and other macromolecules. Biological filters demonstrate both high specificity and rapid motion or high flux of proteins. In contrast, high flux comes at the expense of selectivity in many synthetic filters. Binding can lead to selective transport in systems in which the bound particle can diffuse, but the mechanisms that lead to bound diffusion remain unclear. Previous theory has proposed a molecular mechanism of bound-state mobility based only on transient binding to flexible polymers. However, this mechanism has not been directly tested in experiments. We demonstrate that bound mobility via tethered diffusion can be engineered into a synthetic gel using protein fragments derived from the nuclear pore complex. The resulting bound-state diffusion is quantitatively consistent with theory. Our results suggest that synthetic biological filters can be designed to take advantage of tethered diffusion to give rapid, selective transport.
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Affiliation(s)
- Laura Maguire
- Department of Physics, University of Colorado Boulder, Boulder, Colorado; BioFrontiers Institute, University of Colorado Boulder, Boulder, Colorado
| | - Meredith D Betterton
- Department of Physics, University of Colorado Boulder, Boulder, Colorado; Molecular, Cellular and Developmental Biology, University of Colorado Boulder, Boulder, Colorado
| | - Loren E Hough
- Department of Physics, University of Colorado Boulder, Boulder, Colorado; BioFrontiers Institute, University of Colorado Boulder, Boulder, Colorado.
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17
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Huang K, Tagliazucchi M, Park SH, Rabin Y, Szleifer I. Nanocompartmentalization of the Nuclear Pore Lumen. Biophys J 2019; 118:219-231. [PMID: 31839259 DOI: 10.1016/j.bpj.2019.11.024] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Revised: 09/23/2019] [Accepted: 11/18/2019] [Indexed: 12/12/2022] Open
Abstract
The nuclear pore complex (NPC) employs the intrinsically disordered regions (IDRs) from a family of phenylalanine-glycine-rich nucleoporins (FG-Nups) to control nucleocytoplasmic transport. It has been a long-standing mystery how the IDR-mediated mass exchange can be rapid yet selective. Here, we use a computational microscope to show that nanocompartmentalization of IDR subdomains leads to a remarkably elaborate gating structure as programmed by the amino acid sequences. In particular, we reveal a heterogeneous permeability barrier that combines an inner ring barrier with two vestibular condensates. Throughout the NPC, we find a polarized electrostatic potential and a diffuse thermoreversible FG network featuring mosaic FG territories with low FG-FG pairing fraction. Our theoretical anatomy of the central transporter sheds light into the sequence-structure-function relationship of the FG-Nups and provides a picture of nucleocytoplasmic mass exchange that allows a reconciliation of transport efficiency and specificity.
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Affiliation(s)
- Kai Huang
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois
| | - Mario Tagliazucchi
- DQIAQF and INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II, Ciudad Autónoma de Buenos Aires, Argentina
| | - Sung Hyun Park
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois
| | - Yitzhak Rabin
- Department of Physics and Institute for Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan, Israel
| | - Igal Szleifer
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois; Department of Chemistry, and Chemistry of Life Processes Institute, Northwestern University, Evanston, Illinois.
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18
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Maguire L, Stefferson M, Betterton MD, Hough LE. Design principles of selective transport through biopolymer barriers. Phys Rev E 2019; 100:042414. [PMID: 31770897 PMCID: PMC7502277 DOI: 10.1103/physreve.100.042414] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Indexed: 12/20/2022]
Abstract
In biological systems, polymeric materials block the movement of some macromolecules while allowing the selective passage of others. In some cases, binding enables selective transport, while in others the most inert particles appear to transit most rapidly. To study the general principles of filtering, we develop a model motivated by features of the nuclear pore complex (NPC) which are highly conserved and could potentially be applied to other biological systems. The NPC allows selective transport of proteins called transport factors, which transiently bind to disordered flexible proteins called phenylalanine-glycine-nucleoporins. While the NPC is tuned for transport factors and their cargo, we show that a single feature is sufficient for selective transport: the bound-state motion resulting from transient binding to flexible filaments. Interchain transfer without unbinding can further improve selectivity, especially for cross-linked chains. We generalize this observation to model nanoparticle transport through mucus and show that bound-state motion accelerates transport of transient nanoparticle application, even with clearance by mucus flow. Our model provides a framework to control binding-induced selective transport in biopolymeric materials.
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Affiliation(s)
- Laura Maguire
- Department of Physics, University of Colorado Boulder
- BioFrontiers Institute, University of Colorado Boulder
| | - Michael Stefferson
- Department of Physics, University of Colorado Boulder
- Molecular, Cellular and Developmental Biology, University of Colorado Boulder
| | - Meredith D. Betterton
- Department of Physics, University of Colorado Boulder
- Molecular, Cellular and Developmental Biology, University of Colorado Boulder
| | - Loren E. Hough
- Department of Physics, University of Colorado Boulder
- BioFrontiers Institute, University of Colorado Boulder
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19
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Zhang L, Becton MD, Liu N, Averett RD, Pidaparti RM, Wang X. Physiochemical Effects of Nanoparticles on Cell Nuclear Complex Pore Transport: A Coarse-Grained Computational Model. J Chem Theory Comput 2019; 15:6382-6392. [DOI: 10.1021/acs.jctc.9b00335] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Liuyang Zhang
- State Key Laboratory for Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an, Shaanxi 710049, China
| | - Matthew D. Becton
- College of Engineering, University of Georgia, Athens, Georgia 30602, United States
| | - Ning Liu
- College of Engineering, University of Georgia, Athens, Georgia 30602, United States
| | - Rodney D. Averett
- College of Engineering, University of Georgia, Athens, Georgia 30602, United States
| | - Ramana M. Pidaparti
- College of Engineering, University of Georgia, Athens, Georgia 30602, United States
| | - Xianqiao Wang
- College of Engineering, University of Georgia, Athens, Georgia 30602, United States
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20
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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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21
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Gu C, Vovk A, Zheng T, Coalson RD, Zilman A. The Role of Cohesiveness in the Permeability of the Spatial Assemblies of FG Nucleoporins. Biophys J 2019; 116:1204-1215. [PMID: 30902367 DOI: 10.1016/j.bpj.2019.02.028] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Revised: 11/02/2018] [Accepted: 02/26/2019] [Indexed: 12/31/2022] Open
Abstract
Nuclear pore complexes (NPCs) conduct selective, bidirectional transport across the nuclear envelope. The NPC passageway is lined by intrinsically disordered proteins that contain hydrophobic phenylalanine-glycine (FG) motifs, known as FG nucleoporins (FG nups), that play the key role in the NPC transport mechanism. Cohesive interactions among the FG nups, which arise from the combination of hydrophobic, electrostatic, and other forces, have been hypothesized to control the morphology of the assemblies of FG nups in the NPC, as well as their permeability with respect to the transport proteins. However, the role of FG nup cohesiveness is still vigorously debated. Using coarse-grained polymer theory and numerical simulations, we study the effects of cohesiveness on the selective permeability of in vitro FG nup assemblies in different geometries that have served as proxies for the morphological and transport properties of the NPC. We show that in high-density FG nup assemblies, increase in cohesiveness leads to the decrease in their permeability, in accordance with the accepted view. On the other hand, the permeability of low-density assemblies is a nonmonotonic function of the cohesiveness, and a moderate increase in cohesiveness can enhance permeability. The density- and cohesiveness-dependent effects on permeability are explained by considering the free-energy cost associated with penetrating the FG nup assemblies. We discuss the implications of these findings for the organization and function of the NPC.
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Affiliation(s)
- Chad Gu
- Department of Physics, University of Toronto, Toronto, Ontario, Canada
| | - Andrei Vovk
- Department of Physics, University of Toronto, Toronto, Ontario, Canada
| | - Tiantian Zheng
- Department of Physics, University of Toronto, Toronto, Ontario, Canada
| | - Rob D Coalson
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Anton Zilman
- Department of Physics, University of Toronto, Toronto, Ontario, Canada; Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada.
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22
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Zhang S, Li ZT, Liu M, Wang JR, Xu MQ, Li ZY, Duan XC, Hao YL, Zheng XC, Li H, Feng ZH, Zhang X. Anti-tumour activity of low molecular weight heparin doxorubicin nanoparticles for histone H1 high-expressive prostate cancer PC-3M cells. J Control Release 2018; 295:102-117. [PMID: 30582952 DOI: 10.1016/j.jconrel.2018.12.034] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 12/14/2018] [Accepted: 12/19/2018] [Indexed: 11/30/2022]
Abstract
Nucleus-targeting drug delivery systems (NTDDs) deliver chemotherapeutic agents to nuclei in order to improve the efficacy of anti-tumour therapy. Histone H1 (H1) plays a key role in establishing and maintaining higher order chromatin structures and could bind to cell membranes. In the present study, we selected H1 as a target to prepare a novel H1-mediated NTDD. Low molecular weight heparin (LMHP) and doxorubicin (DOX) were combined to form LMHP-DOX. Then, a novel NTDD consisting of LMHP-DOX nanoparticles (LMHP-DOX NPs) was prepared by self-assembly. The characteristics of LMHP-DOX and LMHP-DOX NPs were investigated. Histone H1 high-expressive prostate cancer PC-3M cell line was selected as the cell model. Cellular uptake, and the in vitro and in vivo anti-tumour activity of LMHP-DOX NPs were evaluated on H1 high-expressive human prostate cancer PC-3M cells. Our results indicated that intact LMHP-DOX NPs mediated by H1 could be absorbed by H1 high-expressive PC-3M cells, escape from the lysosomes to the cytoplasm, and localize in the perinuclear region via H1-mediated, whereby DOX could directly enter the cell nucleus and quickly increase the concentration of DOX in the nuclei of H1 high-expressive PC-3M cells to enhance the apoptotic activity of cancer cells. The anti-coagulant activity of LMHP-DOX NPs was almost completely diminished in rat blood compared with that of LMHP, indicating the safety of LMHP-DOX NPs. Compared to traditional NTDD strategies, LMHP-DOX NPs avoid the complicated modification of nucleus-targeting ligands and provide a compelling solution for the substantially enhanced nuclear uptake of chemotherapeutic agents for the development of more intelligent NTDDs.
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Affiliation(s)
- Shuang Zhang
- Beijing Key Laboratory of Molecular Pharmaceutics and New Drug Delivery Systems, School of Pharmaceutical Sciences, Peking University, Beijing 100191, China; Department of Pharmaceutics, School of Pharmaceutical Sciences, Peking University, Beijing 100191, China
| | - Zhan-Tao Li
- Beijing Key Laboratory of Molecular Pharmaceutics and New Drug Delivery Systems, School of Pharmaceutical Sciences, Peking University, Beijing 100191, China; Department of Pharmaceutics, School of Pharmaceutical Sciences, Peking University, Beijing 100191, China
| | - Man Liu
- Beijing Key Laboratory of Molecular Pharmaceutics and New Drug Delivery Systems, School of Pharmaceutical Sciences, Peking University, Beijing 100191, China; Department of Pharmaceutics, School of Pharmaceutical Sciences, Peking University, Beijing 100191, China
| | - Jing-Ru Wang
- Beijing Key Laboratory of Molecular Pharmaceutics and New Drug Delivery Systems, School of Pharmaceutical Sciences, Peking University, Beijing 100191, China; Department of Pharmaceutics, School of Pharmaceutical Sciences, Peking University, Beijing 100191, China
| | - Mei-Qi Xu
- Beijing Key Laboratory of Molecular Pharmaceutics and New Drug Delivery Systems, School of Pharmaceutical Sciences, Peking University, Beijing 100191, China; Department of Pharmaceutics, School of Pharmaceutical Sciences, Peking University, Beijing 100191, China
| | - Zhuo-Yue Li
- Beijing Key Laboratory of Molecular Pharmaceutics and New Drug Delivery Systems, School of Pharmaceutical Sciences, Peking University, Beijing 100191, China; Department of Pharmaceutics, School of Pharmaceutical Sciences, Peking University, Beijing 100191, China
| | - Xiao-Chuan Duan
- Beijing Key Laboratory of Molecular Pharmaceutics and New Drug Delivery Systems, School of Pharmaceutical Sciences, Peking University, Beijing 100191, China; Department of Pharmaceutics, School of Pharmaceutical Sciences, Peking University, Beijing 100191, China
| | - Yan-Li Hao
- Beijing Key Laboratory of Molecular Pharmaceutics and New Drug Delivery Systems, School of Pharmaceutical Sciences, Peking University, Beijing 100191, China; Department of Pharmaceutics, School of Pharmaceutical Sciences, Peking University, Beijing 100191, China
| | - Xiu-Chai Zheng
- Department of Pharmaceutics, School of Pharmaceutical Sciences, Peking University, Beijing 100191, China
| | - Hui Li
- Beijing Key Laboratory of Molecular Pharmaceutics and New Drug Delivery Systems, School of Pharmaceutical Sciences, Peking University, Beijing 100191, China
| | - Zhen-Han Feng
- Beijing Key Laboratory of Molecular Pharmaceutics and New Drug Delivery Systems, School of Pharmaceutical Sciences, Peking University, Beijing 100191, China
| | - Xuan Zhang
- Beijing Key Laboratory of Molecular Pharmaceutics and New Drug Delivery Systems, School of Pharmaceutical Sciences, Peking University, Beijing 100191, China; Department of Pharmaceutics, School of Pharmaceutical Sciences, Peking University, Beijing 100191, China.
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23
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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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24
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Pulupa J, Rachh M, Tomasini MD, Mincer JS, Simon SM. A coarse-grained computational model of the nuclear pore complex predicts Phe-Gly nucleoporin dynamics. J Gen Physiol 2017; 149:951-966. [PMID: 28887410 PMCID: PMC5694938 DOI: 10.1085/jgp.201711769] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Revised: 06/27/2017] [Accepted: 08/10/2017] [Indexed: 11/25/2022] Open
Abstract
The phenylalanine-glycine–repeat nucleoporins are essential for transport through the nuclear pore complex. Pulupa et al. observe reptation of these nucleoporins on a physiological timescale in coarse-grained computational simulations. The phenylalanine-glycine–repeat nucleoporins (FG-Nups), which occupy the lumen of the nuclear pore complex (NPC), are critical for transport between the nucleus and cytosol. Although NPCs differ in composition across species, they are largely conserved in organization and function. Transport through the pore is on the millisecond timescale. Here, to explore the dynamics of nucleoporins on this timescale, we use coarse-grained computational simulations. These simulations generate predictions that can be experimentally tested to distinguish between proposed mechanisms of transport. Our model reflects the conserved structure of the NPC, in which FG-Nup filaments extend into the lumen and anchor along the interior of the channel. The lengths of the filaments in our model are based on the known characteristics of yeast FG-Nups. The FG-repeat sites also bind to each other, and we vary this association over several orders of magnitude and run 100-ms simulations for each value. The autocorrelation functions of the orientation of the simulated FG-Nups are compared with in vivo anisotropy data. We observe that FG-Nups reptate back and forth through the NPC at timescales commensurate with experimental measurements of the speed of cargo transport through the NPC. Our results are consistent with models of transport where FG-Nup filaments are free to move across the central channel of the NPC, possibly informing how cargo might transverse the NPC.
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Affiliation(s)
- Joan Pulupa
- Laboratory of Cellular Biophysics, The Rockefeller University, New York, NY
| | - Manas Rachh
- Courant Institute of Mathematical Sciences, New York, NY
| | - Michael D Tomasini
- Laboratory of Cellular Biophysics, The Rockefeller University, New York, NY
| | - Joshua S Mincer
- Laboratory of Cellular Biophysics, The Rockefeller University, New York, NY .,Department of Anesthesiology, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Sanford M Simon
- Laboratory of Cellular Biophysics, The Rockefeller University, New York, NY
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25
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Jovanovic-Talisman T, Zilman A. Protein Transport by the Nuclear Pore Complex: Simple Biophysics of a Complex Biomachine. Biophys J 2017; 113:6-14. [PMID: 28700925 DOI: 10.1016/j.bpj.2017.05.024] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Revised: 05/01/2017] [Accepted: 05/08/2017] [Indexed: 01/07/2023] Open
Abstract
In eukaryotic cells, transport of molecules between the nucleus and the cytoplasm is facilitated by highly selective and efficient biomachines known as nuclear pore complexes (NPCs). The structural details of NPCs vary across species, with many of their constituent proteins exhibiting relatively low sequence conservation; yet the NPC as a whole retains its general architecture and mechanism of action in all eukaryotes from yeast to humans. This functional conservation in the absence of precise molecular conservation suggests that many aspects of the NPC transport mechanism may be understood based on general biophysical considerations. Accordingly, some aspects of NPC function have been recapitulated in artificial nanochannel mimics, even though they lack certain molecular elements of the endogenous NPC. Herein, we review biophysical aspects of NPC architecture and function and cover recent progress in the field. We also review recent advances in man-made molecular filters inspired by NPCs, and their applications in nanotechnology. We conclude the review with an outlook on outstanding questions in the field and biomedical aspects of NPC transport.
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Affiliation(s)
- Tijana Jovanovic-Talisman
- Department of Molecular Medicine, Beckman Research Institute of the City of Hope Comprehensive Cancer Center, Duarte, California.
| | - Anton Zilman
- Department of Physics, University of Toronto, Toronto, Ontario, Canada; Institute for Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada.
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26
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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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27
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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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28
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Flatt JW, Greber UF. Viral mechanisms for docking and delivering at nuclear pore complexes. Semin Cell Dev Biol 2017; 68:59-71. [PMID: 28506891 DOI: 10.1016/j.semcdb.2017.05.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Accepted: 05/11/2017] [Indexed: 12/22/2022]
Abstract
Some viruses possess the remarkable ability to transport their genomes across nuclear pore complexes (NPCs) for replication inside the host cell's intact nuclear compartment. Viral mechanisms for crossing the restrictive NPC passageway are highly complex and astonishingly diverse, requiring in each case stepwise interaction between incoming virus particles and components of the nuclear transport machinery. Exactly how a large viral genome loaded with accessory proteins is able to pass through the relatively narrow central channel of the NPC without causing catastrophic structural damage is not yet fully understood. It appears likely, however, that the overall structure of the NPC changes in response to the cargo. Translocation may result in nucleic acids being misdelivered to the cytoplasm. Here we consider in detail the diverse strategies that viruses have evolved to target and subvert NPCs during infection. For decades, this process has both captivated and confounded researchers in the fields of virology, cell biology, and structural biology.
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Affiliation(s)
- Justin W Flatt
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Urs F Greber
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
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29
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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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30
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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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31
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Timney BL, Raveh B, Mironska R, Trivedi JM, Kim SJ, Russel D, Wente SR, Sali A, Rout MP. Simple rules for passive diffusion through the nuclear pore complex. J Cell Biol 2016; 215:57-76. [PMID: 27697925 PMCID: PMC5057280 DOI: 10.1083/jcb.201601004] [Citation(s) in RCA: 286] [Impact Index Per Article: 35.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Accepted: 09/06/2016] [Indexed: 02/07/2023] Open
Abstract
Passive macromolecular diffusion through nuclear pore complexes is thought to decrease dramatically beyond ∼40 kD. Using time-resolved fluorescence microscopy and Brownian dynamics simulations, Timney et al. show that this barrier is in fact much softer, decreasing along a continuum. Passive macromolecular diffusion through nuclear pore complexes (NPCs) is thought to decrease dramatically beyond a 30–60-kD size threshold. Using thousands of independent time-resolved fluorescence microscopy measurements in vivo, we show that the NPC lacks such a firm size threshold; instead, it forms a soft barrier to passive diffusion that intensifies gradually with increasing molecular mass in both the wild-type and mutant strains with various subsets of phenylalanine-glycine (FG) domains and different levels of baseline passive permeability. Brownian dynamics simulations replicate these findings and indicate that the soft barrier results from the highly dynamic FG repeat domains and the diffusing macromolecules mutually constraining and competing for available volume in the interior of the NPC, setting up entropic repulsion forces. We found that FG domains with exceptionally high net charge and low hydropathy near the cytoplasmic end of the central channel contribute more strongly to obstruction of passive diffusion than to facilitated transport, revealing a compartmentalized functional arrangement within the NPC.
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Affiliation(s)
- Benjamin L Timney
- Laboratory of Cellular and Structural Biology, The Rockefeller University, New York, NY 10065
| | - Barak Raveh
- Department of Bioengineering and Therapeutic Sciences, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, CA 94158 Department of Pharmaceutical Chemistry, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, CA 94158
| | - Roxana Mironska
- Laboratory of Cellular and Structural Biology, The Rockefeller University, New York, NY 10065
| | - Jill M Trivedi
- Laboratory of Cellular and Structural Biology, The Rockefeller University, New York, NY 10065
| | - Seung Joong Kim
- Department of Bioengineering and Therapeutic Sciences, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, CA 94158 Department of Pharmaceutical Chemistry, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, CA 94158
| | - Daniel Russel
- Department of Bioengineering and Therapeutic Sciences, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, CA 94158 Department of Pharmaceutical Chemistry, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, CA 94158
| | - Susan R Wente
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Andrej Sali
- Department of Bioengineering and Therapeutic Sciences, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, CA 94158 Department of Pharmaceutical Chemistry, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, CA 94158
| | - Michael P Rout
- Laboratory of Cellular and Structural Biology, The Rockefeller University, New York, NY 10065
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32
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Eskandari Nasrabad A, Jasnow D, Zilman A, Coalson RD. Precise control of polymer coated nanopores by nanoparticle additives: Insights from computational modeling. J Chem Phys 2016. [DOI: 10.1063/1.4955191] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Affiliation(s)
| | - David Jasnow
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
| | - Anton Zilman
- Department of Physics, University of Toronto, Toronto, Ontario M5S 1A7, Canada
| | - Rob D. Coalson
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
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33
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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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34
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Lemke EA. The Multiple Faces of Disordered Nucleoporins. J Mol Biol 2016; 428:2011-24. [PMID: 26791761 PMCID: PMC7611686 DOI: 10.1016/j.jmb.2016.01.002] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Revised: 12/30/2015] [Accepted: 01/04/2016] [Indexed: 11/26/2022]
Abstract
An evolutionary advantage of intrinsically disordered proteins (IDPs) is their ability to bind a variety of folded proteins-a paradigm that is central to the nucleocytoplasmic transport mechanism, in which nuclear transport receptors mediate the translocation of various cargo through the nuclear pore complex by binding disordered phenylalanine-glycine-rich nucleoporins (FG-Nups). FG-Nups are highly dynamic, which poses a substantial problem when trying to determine precisely their function using common experimental approaches. FG-Nups have been studied under a variety of conditions, ranging from those that constitute single-molecule measurements to physiological concentrations at which they can form supramolecular structures. In this review, I describe the physicochemical properties of FG-Nups and compare them to those of other disordered systems, including well-studied IDPs. From this comparison, it is apparent that FG-Nups not only share some properties with IDPs in general but also possess unique characteristics that might be key to their central role in the nucleocytoplasmic transport machinery.
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Affiliation(s)
- Edward A Lemke
- Structural and Computational Biology Unit, Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany.
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35
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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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36
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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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37
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Fan Y, Li C, Li F, Chen D. pH-activated size reduction of large compound nanoparticles for in vivo nucleus-targeted drug delivery. Biomaterials 2016; 85:30-9. [DOI: 10.1016/j.biomaterials.2016.01.057] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Revised: 01/26/2016] [Accepted: 01/27/2016] [Indexed: 10/24/2022]
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38
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Musser SM, Grünwald D. Deciphering the Structure and Function of Nuclear Pores Using Single-Molecule Fluorescence Approaches. J Mol Biol 2016; 428:2091-119. [PMID: 26944195 DOI: 10.1016/j.jmb.2016.02.023] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Revised: 01/05/2016] [Accepted: 02/17/2016] [Indexed: 01/06/2023]
Abstract
Due to its central role in macromolecular trafficking and nucleocytoplasmic information transfer, the nuclear pore complex (NPC) has been studied in great detail using a wide spectrum of methods. Consequently, many aspects of its architecture, general function, and role in the life cycle of a cell are well understood. Over the last decade, fluorescence microscopy methods have enabled the real-time visualization of single molecules interacting with and transiting through the NPC, allowing novel questions to be examined with nanometer precision. While initial single-molecule studies focused primarily on import pathways using permeabilized cells, it has recently proven feasible to investigate the export of mRNAs in living cells. Single-molecule assays can address questions that are difficult or impossible to answer by other means, yet the complexity of nucleocytoplasmic transport requires that interpretation be based on a firm genetic, biochemical, and structural foundation. Moreover, conceptually simple single-molecule experiments remain technically challenging, particularly with regard to signal intensity, signal-to-noise ratio, and the analysis of noise, stochasticity, and precision. We discuss nuclear transport issues recently addressed by single-molecule microscopy, evaluate the limits of existing assays and data, and identify open questions for future studies. We expect that single-molecule fluorescence approaches will continue to be applied to outstanding nucleocytoplasmic transport questions, and that the approaches developed for NPC studies are extendable to additional complex systems and pathways within cells.
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Affiliation(s)
- Siegfried M Musser
- Department of Molecular and Cellular Medicine, College of Medicine, The Texas A&M Health Science Center, 1114 TAMU, College Station, TX 77843, USA.
| | - David Grünwald
- RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, MA 01605, USA.
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39
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Energetics of Transport through the Nuclear Pore Complex. PLoS One 2016; 11:e0148876. [PMID: 26894898 PMCID: PMC4764519 DOI: 10.1371/journal.pone.0148876] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Accepted: 01/25/2016] [Indexed: 01/30/2023] Open
Abstract
Molecular transport across the nuclear envelope in eukaryotic cells is solely controlled by the nuclear pore complex (NPC). The NPC provides two types of nucleocytoplasmic transport: passive diffusion of small molecules and active chaperon-mediated translocation of large molecules. It has been shown that the interaction between intrinsically disordered proteins that line the central channel of the NPC and the transporting cargoes is the determining factor, but the exact mechanism of transport is yet unknown. Here, we use coarse-grained molecular dynamics simulations to quantify the energy barrier that has to be overcome for molecules to pass through the NPC. We focus on two aspects of transport. First, the passive transport of model cargo molecules with different sizes is studied and the size selectivity feature of the NPC is investigated. Our results show that the transport probability of cargoes is significantly reduced when they are larger than ∼5 nm in diameter. Secondly, we show that incorporating hydrophobic binding spots on the surface of the cargo effectively decreases the energy barrier of the pore. Finally, a simple transport model is proposed which characterizes the energy barrier of the NPC as a function of diameter and hydrophobicity of the transporting particles.
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40
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Vuković LD, Jevtić P, Edens LJ, Levy DL. New Insights into Mechanisms and Functions of Nuclear Size Regulation. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2016; 322:1-59. [PMID: 26940517 DOI: 10.1016/bs.ircmb.2015.11.001] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Nuclear size is generally maintained within a defined range in a given cell type. Changes in cell size that occur during cell growth, development, and differentiation are accompanied by dynamic nuclear size adjustments in order to establish appropriate nuclear-to-cytoplasmic volume relationships. It has long been recognized that aberrations in nuclear size are associated with certain disease states, most notably cancer. Nuclear size and morphology must impact nuclear and cellular functions. Understanding these functional implications requires an understanding of the mechanisms that control nuclear size. In this review, we first provide a general overview of the diverse cellular structures and activities that contribute to nuclear size control, including structural components of the nucleus, effects of DNA amount and chromatin compaction, signaling, and transport pathways that impinge on the nucleus, extranuclear structures, and cell cycle state. We then detail some of the key mechanistic findings about nuclear size regulation that have been gleaned from a variety of model organisms. Lastly, we review studies that have implicated nuclear size in the regulation of cell and nuclear function and speculate on the potential functional significance of nuclear size in chromatin organization, gene expression, nuclear mechanics, and disease. With many fundamental cell biological questions remaining to be answered, the field of nuclear size regulation is still wide open.
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Affiliation(s)
- Lidija D Vuković
- Department of Molecular Biology, University of Wyoming, Laramie, WY, United States of America
| | - Predrag Jevtić
- Department of Molecular Biology, University of Wyoming, Laramie, WY, United States of America
| | - Lisa J Edens
- Department of Molecular Biology, University of Wyoming, Laramie, WY, United States of America
| | - Daniel L Levy
- Department of Molecular Biology, University of Wyoming, Laramie, WY, United States of America.
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Peyro M, Soheilypour M, Ghavami A, Mofrad MRK. Nucleoporin's Like Charge Regions Are Major Regulators of FG Coverage and Dynamics Inside the Nuclear Pore Complex. PLoS One 2015; 10:e0143745. [PMID: 26658558 PMCID: PMC4676729 DOI: 10.1371/journal.pone.0143745] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2015] [Accepted: 11/09/2015] [Indexed: 11/19/2022] Open
Abstract
Nucleocytoplasmic transport has been the subject of a large body of research in the past few decades. Recently, the focus of investigations in this field has shifted from studies of the overall function of the nuclear pore complex (NPC) to the examination of the role of different domains of phenylalanine-glycine nucleoporin (FG Nup) sequences on the NPC function. In our recent bioinformatics study, we showed that FG Nups have some evolutionarily conserved sequence-based features that might govern their physical behavior inside the NPC. We proposed the ‘like charge regions’ (LCRs), sequences of charged residues with only one type of charge, as one of the features that play a significant role in the formation of FG network inside the central channel. In this study, we further explore the role of LCRs in the distribution of FG Nups, using a recently developed coarse-grained molecular dynamics model. Our results demonstrate how LCRs affect the formation of two transport pathways. While some FG Nups locate their FG network at the center of the NPC forming a homogeneous meshwork of FG repeats, other FG Nups cover the space adjacent to the NPC wall. LCRs in the former group, i.e. FG Nups that form an FG domain at the center, tend to regulate the size of the highly dense, doughnut-shaped FG meshwork and leave a small low FG density area at the center of the pore for passive diffusion. On the other hand, LCRs in the latter group of FG Nups enable them to maximize their interactions and cover a larger space inside the NPC to increase its capability to transport numerous cargos at the same time. Finally, a new viewpoint is proposed that reconciles different models for the nuclear pore selective barrier function.
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Affiliation(s)
- Mohaddeseh Peyro
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, California, United States of America
| | - Mohammad Soheilypour
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, California, United States of America
| | - Ali Ghavami
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, California, United States of America
| | - Mohammad R. K. Mofrad
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, California, United States of America
- * E-mail:
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42
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Peyro M, Soheilypour M, Lee BL, Mofrad MRK. Evolutionarily Conserved Sequence Features Regulate the Formation of the FG Network at the Center of the Nuclear Pore Complex. Sci Rep 2015; 5:15795. [PMID: 26541386 PMCID: PMC4635341 DOI: 10.1038/srep15795] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Accepted: 09/29/2015] [Indexed: 12/29/2022] Open
Abstract
The nuclear pore complex (NPC) is the portal for bidirectional transportation of cargos between the nucleus and the cytoplasm. While most of the structural elements of the NPC, i.e. nucleoporins (Nups), are well characterized, the exact transport mechanism is still under much debate. Many of the functional Nups are rich in phenylalanine-glycine (FG) repeats and are believed to play the key role in nucleocytoplasmic transport. We present a bioinformatics study conducted on more than a thousand FG Nups across 252 species. Our results reveal the regulatory role of polar residues and specific sequences of charged residues, named 'like charge regions' (LCRs), in the formation of the FG network at the center of the NPC. Positively charged LCRs prepare the environment for negatively charged cargo complexes and regulate the size of the FG network. The low number density of charged residues in these regions prevents FG domains from forming a relaxed coil structure. Our results highlight the significant role of polar interactions in FG network formation at the center of the NPC and demonstrate that the specific localization of LCRs, FG motifs, charged, and polar residues regulate the formation of the FG network at the center of the NPC.
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Affiliation(s)
- M Peyro
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, CA 94720
| | - M Soheilypour
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, CA 94720
| | - B L Lee
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, CA 94720
| | - M R K Mofrad
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, CA 94720
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Abstract
Many viruses deliver their genomes into the host cell’s nucleus before they replicate. While onco-retroviruses and papillomaviruses tether their genomes to host chromatin upon mitotic breakdown of the nuclear envelope, lentiviruses, such as human immunodeficiency virus, adenoviruses, herpesviruses, parvoviruses, influenza viruses, hepatitis B virus, polyomaviruses, and baculoviruses deliver their genomes into the nucleus of post-mitotic cells. This poses the significant challenge of slipping a DNA or RNA genome past the nuclear pore complex (NPC) embedded in the nuclear envelope. Quantitative fluorescence imaging is shedding new light on this process, with recent data implicating misdelivery of viral genomes at nuclear pores as a bottleneck to virus replication. Here, we infer NPC functions for nuclear import of viral genomes from cell biology experiments and explore potential causes of misdelivery, including improper virus docking at NPCs, incomplete translocation, virus-induced stress and innate immunity reactions. We conclude by discussing consequences of viral genome misdelivery for viruses and host cells, and lay out future questions to enhance our understanding of this phenomenon. Further studies into viral genome misdelivery may reveal unexpected aspects about NPC structure and function, as well as aid in developing strategies for controlling viral infections to improve human health.
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44
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Molecular dynamics simulations of large macromolecular complexes. Curr Opin Struct Biol 2015; 31:64-74. [PMID: 25845770 DOI: 10.1016/j.sbi.2015.03.007] [Citation(s) in RCA: 264] [Impact Index Per Article: 29.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Revised: 03/13/2015] [Accepted: 03/16/2015] [Indexed: 12/11/2022]
Abstract
Connecting dynamics to structural data from diverse experimental sources, molecular dynamics simulations permit the exploration of biological phenomena in unparalleled detail. Advances in simulations are moving the atomic resolution descriptions of biological systems into the million-to-billion atom regime, in which numerous cell functions reside. In this opinion, we review the progress, driven by large-scale molecular dynamics simulations, in the study of viruses, ribosomes, bioenergetic systems, and other diverse applications. These examples highlight the utility of molecular dynamics simulations in the critical task of relating atomic detail to the function of supramolecular complexes, a task that cannot be achieved by smaller-scale simulations or existing experimental approaches alone.
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45
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Probing the disordered domain of the nuclear pore complex through coarse-grained molecular dynamics simulations. Biophys J 2015; 107:1393-402. [PMID: 25229147 DOI: 10.1016/j.bpj.2014.07.060] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2013] [Revised: 07/11/2014] [Accepted: 07/22/2014] [Indexed: 01/27/2023] Open
Abstract
The distribution of disordered proteins (FG-nups) that line the transport channel of the nuclear pore complex (NPC) is investigated by means of coarse-grained molecular dynamics simulations. A one-bead-per-amino-acid model is presented that accounts for the hydrophobic/hydrophilic and electrostatic interactions between different amino acids, polarity of the solvent, and screening of free ions. The results indicate that the interaction of the FG-nups forms a high-density, doughnut-like distribution inside the NPC, which is rich in FG-repeats. We show that the obtained distribution is encoded in the amino-acid sequence of the FG-nups and is driven by both electrostatic and hydrophobic interactions. To explore the relation between structure and function, we have systematically removed different combinations of FG-nups from the pore to simulate inviable and viable NPCs that were previously studied experimentally. The obtained density distributions show that the maximum density of the FG-nups inside the pore does not exceed 185 mg/mL in the inviable NPCs, whereas for the wild-type and viable NPCs, this value increases to 300 mg/mL. Interestingly, this maximum density is not correlated to the total mass of the FG-nups, but depends sensitively on the specific combination of essential Nups located in the central plane of the NPC.
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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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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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50
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Roberts E. Cellular and molecular structure as a unifying framework for whole-cell modeling. Curr Opin Struct Biol 2014; 25:86-91. [PMID: 24509245 DOI: 10.1016/j.sbi.2014.01.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2013] [Accepted: 01/07/2014] [Indexed: 10/25/2022]
Abstract
Whole-cell modeling has the potential to play a major role in revolutionizing our understanding of cellular biology over the next few decades. A computational model of the entire cell would allow cellular biologists to integrate data from many disparate sources in a single consistent framework. Such a comprehensive model would be useful both for hypothesis testing and in the discovery of new behaviors that emerge from complex biological networks. Cellular and molecular structure can and should be a key organizing principle in a whole-cell model, connecting models across time and length scales in a multiscale approach. Here I present a summary of recent research centered around using molecular and cellular structure to model the behavior of cells.
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Affiliation(s)
- Elijah Roberts
- Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218, USA.
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