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1.
Nat Commun ; 15(1): 3797, 2024 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-38714656

RESUMO

Nucleoporins rich in phenylalanine/glycine (FG) residues form the permeability barrier within the nuclear pore complex and are implicated in several pathological cellular processes, including oncogenic fusion condensates. The self-association of FG-repeat proteins and interactions between FG-repeats play a critical role in these activities by forming hydrogel-like structures. Here we show that mutation of specific FG repeats of Nup98 can strongly decrease the protein's self-association capabilities. We further present a cryo-electron microscopy structure of a Nup98 peptide fibril with higher stability per residue compared with previous Nup98 fibril structures. The high-resolution structure reveals zipper-like hydrophobic patches which contain a GLFG motif and are less compatible for binding to nuclear transport receptors. The identified distinct molecular properties of different regions of the nucleoporin may contribute to spatial variations in the self-association of FG-repeats, potentially influencing transport processes through the nuclear pore.


Assuntos
Microscopia Crioeletrônica , Complexo de Proteínas Formadoras de Poros Nucleares , Complexo de Proteínas Formadoras de Poros Nucleares/metabolismo , Complexo de Proteínas Formadoras de Poros Nucleares/química , Complexo de Proteínas Formadoras de Poros Nucleares/genética , Complexo de Proteínas Formadoras de Poros Nucleares/ultraestrutura , Humanos , Mutação , Poro Nuclear/metabolismo , Poro Nuclear/ultraestrutura , Poro Nuclear/química , Glicina/química , Glicina/metabolismo , Fenilalanina/química , Fenilalanina/metabolismo , Sequências Repetitivas de Aminoácidos , Ligação Proteica , Modelos Moleculares , Interações Hidrofóbicas e Hidrofílicas
2.
Biophys J ; 123(9): 1085-1097, 2024 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-38640928

RESUMO

As the main gatekeeper of the nucleocytoplasmic transport in eukaryotic cells, the nuclear pore complex (NPC) faces the daunting task of facilitating the bidirectional transport of a high volume of macromolecular cargoes while ensuring the selectivity, speed, and efficiency of this process. The competition between opposing nuclear import and export fluxes passing through the same channel is expected to pose a major challenge to transport efficiency. It has been suggested that phase separation-like radial segregation of import and export fluxes within the assembly of intrinsically disordered proteins that line the NPC pore could be a mechanism for ensuring efficient bidirectional transport. We examine the impact of radial segregation on the efficiency of bidirectional transport through the NPC using a coarse-grained computational model of the NPC. We find little evidence that radial segregation improves transport efficiency. By contrast, surprisingly, we find that NTR crowding may enhance rather than impair the efficiency of bidirectional transport although it decreases the available space in the pore. We identify mechanisms of this novel crowding-induced transport cooperativity through the self-regulation of cargo density and flux in the pore. These findings explain how the functional architecture of the NPC resolves the problem of efficient bidirectional transport, and provide inspiration for the alleviation of clogging in artificial selective nanopores.


Assuntos
Poro Nuclear , Poro Nuclear/metabolismo , Poro Nuclear/química , Cinética , Transporte Ativo do Núcleo Celular , Modelos Biológicos
3.
Genetics ; 226(4)2024 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-38302116

RESUMO

The nuclear pore complex (NPC) mediates the selective exchange of macromolecules between the nucleus and the cytoplasm. Neurodegenerative diseases such as amyotrophic lateral sclerosis are characterized by mislocalization of nucleoporins (Nups), transport receptors, and Ras-related nuclear proteins into nucleoplasmic or cytosolic aggregates, underscoring the importance of precise assembly of the NPC. The assembly state of large protein complexes is strictly monitored by the protein quality control system. The ubiquitin-proteasome system may eliminate aberrant, misfolded, and/or orphan components; however, the involvement of the ubiquitin-proteasome system in the degradation of nonnative Nups in the NPC remains unclear. Here, we show that in Saccharomyces cerevisiae, although Nup1 (the FG-Nup component of the central core of the NPC) was stable, C-terminally green fluorescent protein-tagged Nup1, which had been incorporated into the NPC, was degraded by the proteasome especially under heat stress conditions. The degradation was dependent on the San1 ubiquitin ligase and Cdc48/p97, as well as its cofactor Doa1. We also demonstrate that San1 weakly but certainly contributes to the degradation of nontagged endogenous Nup1 in cells defective in NPC biogenesis by the deletion of NUP120. In addition, the overexpression of SAN1 exacerbated the growth defect phenotype of nup120Δ cells, which may be caused by excess degradation of defective Nups due to the deletion of NUP120. These biochemical and genetic data suggest that San1 is involved in the degradation of nonnative Nups generated by genetic mutation or when NPC biogenesis is impaired.


Assuntos
Complexo de Endopeptidases do Proteassoma , Proteínas de Saccharomyces cerevisiae , Poro Nuclear/genética , Poro Nuclear/química , Poro Nuclear/metabolismo , Complexo de Proteínas Formadoras de Poros Nucleares/genética , Complexo de Proteínas Formadoras de Poros Nucleares/metabolismo , Complexo de Endopeptidases do Proteassoma/metabolismo , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Ubiquitina/análise , Ubiquitina/genética , Ubiquitina/metabolismo , Ubiquitina-Proteína Ligases/genética , Ubiquitina-Proteína Ligases/metabolismo
4.
Nature ; 626(8000): 843-851, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-38267583

RESUMO

HIV-1 infection requires nuclear entry of the viral genome. Previous evidence suggests that this entry proceeds through nuclear pore complexes (NPCs), with the 120 × 60 nm capsid squeezing through an approximately 60-nm-wide central channel1 and crossing the permeability barrier of the NPC. This barrier can be described as an FG phase2 that is assembled from cohesively interacting phenylalanine-glycine (FG) repeats3 and is selectively permeable to cargo captured by nuclear transport receptors (NTRs). Here we show that HIV-1 capsid assemblies can target NPCs efficiently in an NTR-independent manner and bind directly to several types of FG repeats, including barrier-forming cohesive repeats. Like NTRs, the capsid readily partitions into an in vitro assembled cohesive FG phase that can serve as an NPC mimic and excludes much smaller inert probes such as mCherry. Indeed, entry of the capsid protein into such an FG phase is greatly enhanced by capsid assembly, which also allows the encapsulated clients to enter. Thus, our data indicate that the HIV-1 capsid behaves like an NTR, with its interior serving as a cargo container. Because capsid-coating with trans-acting NTRs would increase the diameter by 10 nm or more, we suggest that such a 'self-translocating' capsid undermines the size restrictions imposed by the NPC scaffold, thereby bypassing an otherwise effective barrier to viral infection.


Assuntos
Proteínas do Capsídeo , Capsídeo , Glicina , HIV-1 , Complexo de Proteínas Formadoras de Poros Nucleares , Poro Nuclear , Fenilalanina , Humanos , Transporte Ativo do Núcleo Celular , Capsídeo/química , Capsídeo/metabolismo , Glicina/metabolismo , HIV-1/química , HIV-1/genética , HIV-1/metabolismo , Poro Nuclear/química , Poro Nuclear/metabolismo , Poro Nuclear/virologia , Complexo de Proteínas Formadoras de Poros Nucleares/química , Complexo de Proteínas Formadoras de Poros Nucleares/metabolismo , Permeabilidade , Fenilalanina/metabolismo , Solubilidade , Internalização do Vírus , Proteínas do Capsídeo/química , Proteínas do Capsídeo/metabolismo
5.
Nature ; 626(8000): 836-842, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-38267582

RESUMO

HIV can infect non-dividing cells because the viral capsid can overcome the selective barrier of the nuclear pore complex and deliver the genome directly into the nucleus1,2. Remarkably, the intact HIV capsid is more than 1,000 times larger than the size limit prescribed by the diffusion barrier of the nuclear pore3. This barrier in the central channel of the nuclear pore is composed of intrinsically disordered nucleoporin domains enriched in phenylalanine-glycine (FG) dipeptides. Through multivalent FG interactions, cellular karyopherins and their bound cargoes solubilize in this phase to drive nucleocytoplasmic transport4. By performing an in vitro dissection of the nuclear pore complex, we show that a pocket on the surface of the HIV capsid similarly interacts with FG motifs from multiple nucleoporins and that this interaction licences capsids to penetrate FG-nucleoporin condensates. This karyopherin mimicry model addresses a key conceptual challenge for the role of the HIV capsid in nuclear entry and offers an explanation as to how an exogenous entity much larger than any known cellular cargo may be able to non-destructively breach the nuclear envelope.


Assuntos
Proteínas do Capsídeo , Glicina , HIV , Carioferinas , Mimetismo Molecular , Complexo de Proteínas Formadoras de Poros Nucleares , Poro Nuclear , Fenilalanina , Humanos , Transporte Ativo do Núcleo Celular , Proteínas do Capsídeo/química , Proteínas do Capsídeo/metabolismo , Difusão , Dipeptídeos/química , Dipeptídeos/metabolismo , Glicina/metabolismo , HIV/química , HIV/metabolismo , Técnicas In Vitro , Proteínas Intrinsicamente Desordenadas/química , Proteínas Intrinsicamente Desordenadas/metabolismo , Carioferinas/metabolismo , Poro Nuclear/química , Poro Nuclear/metabolismo , Poro Nuclear/virologia , Complexo de Proteínas Formadoras de Poros Nucleares/química , Complexo de Proteínas Formadoras de Poros Nucleares/metabolismo , Permeabilidade , Fenilalanina/metabolismo , Solubilidade , Internalização do Vírus , Capsídeo/química , Capsídeo/metabolismo
6.
Phys Chem Chem Phys ; 25(48): 32824-32836, 2023 Dec 13.
Artigo em Inglês | MEDLINE | ID: mdl-38018404

RESUMO

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.


Assuntos
Poro Nuclear , Saccharomyces cerevisiae , Poro Nuclear/química , Complexo de Proteínas Formadoras de Poros Nucleares/análise , Complexo de Proteínas Formadoras de Poros Nucleares/química , Glicina/química , Fenilalanina/química
7.
Bioinformatics ; 39(10)2023 10 03.
Artigo em Inglês | MEDLINE | ID: mdl-37756700

RESUMO

MOTIVATION: The nuclear pore complex (NPC) is the only passageway for macromolecules between nucleus and cytoplasm, and an important reference standard in microscopy: it is massive and stereotypically arranged. The average architecture of NPC proteins has been resolved with pseudoatomic precision, however observed NPC heterogeneities evidence a high degree of divergence from this average. Single-molecule localization microscopy (SMLM) images NPCs at protein-level resolution, whereupon image analysis software studies NPC variability. However, the true picture of this variability is unknown. In quantitative image analysis experiments, it is thus difficult to distinguish intrinsically high SMLM noise from variability of the underlying structure. RESULTS: We introduce CIR4MICS ('ceramics', Configurable, Irregular Rings FOR MICroscopy Simulations), a pipeline that synthesizes ground truth datasets of structurally variable NPCs based on architectural models of the true NPC. Users can select one or more N- or C-terminally tagged NPC proteins, and simulate a wide range of geometric variations. We also represent the NPC as a spring-model such that arbitrary deforming forces, of user-defined magnitudes, simulate irregularly shaped variations. Further, we provide annotated reference datasets of simulated human NPCs, which facilitate a side-by-side comparison with real data. To demonstrate, we synthetically replicate a geometric analysis of real NPC radii and reveal that a range of simulated variability parameters can lead to observed results. Our simulator is therefore valuable to test the capabilities of image analysis methods, as well as to inform experimentalists about the requirements of hypothesis-driven imaging studies. AVAILABILITY AND IMPLEMENTATION: Code: https://github.com/uhlmanngroup/cir4mics. Simulated data: BioStudies S-BSST1058.


Assuntos
Microscopia , Poro Nuclear , Humanos , Poro Nuclear/química , Poro Nuclear/metabolismo , Complexo de Proteínas Formadoras de Poros Nucleares/análise , Complexo de Proteínas Formadoras de Poros Nucleares/metabolismo , Imagem Individual de Molécula/métodos , Software
8.
Mol Biol (Mosk) ; 57(4): 573-586, 2023.
Artigo em Russo | MEDLINE | ID: mdl-37528778

RESUMO

Nucleocytoplasmic exchange in the cell occurs through the nuclear pore complexes (NPCs). NPCs are large multiprotein complexes with octagonal symmetry about their axis and imperfect mirror symmetry about a plane parallel with the nuclear envelop (NE). NPC fuses the inner and outer nuclear membranes and opens up a channel between nucleus and cytoplasm. NPC is built of nucleoporins. Each nucleoporin occurs in at least eight copies per NPC. Inside the NPC a permeability barrier forms by which NPCs can provide fast and selectable transport of molecules from one side of the nuclear membrane to the other. NPC architecture is based on hierarchical principle of organization. Nucleoporins are integrated into complexes that oligomerizes into bigger octomeric high-order structures. These structures are the main components of NPCs. In the first part of this work, the main attention is paid to NPC structure and nucleoporin properties. The second part is dedicated to mechanisms of NPC assembly and disassembly at different stages of the cell cycle.


Assuntos
Complexo de Proteínas Formadoras de Poros Nucleares , Poro Nuclear , Poro Nuclear/química , Poro Nuclear/metabolismo , Complexo de Proteínas Formadoras de Poros Nucleares/genética , Complexo de Proteínas Formadoras de Poros Nucleares/análise , Complexo de Proteínas Formadoras de Poros Nucleares/química , Membrana Nuclear/metabolismo , Citoplasma/metabolismo , Complexos Multiproteicos/análise , Complexos Multiproteicos/metabolismo , Transporte Ativo do Núcleo Celular
9.
J Cell Biol ; 222(9)2023 09 04.
Artigo em Inglês | MEDLINE | ID: mdl-37358474

RESUMO

The nuclear pore complex (NPC) physically interacts with chromatin and regulates gene expression. The Saccharomyces cerevisiae inner ring nucleoporin Nup170 has been implicated in chromatin organization and the maintenance of gene silencing in subtelomeric regions. To gain insight into how Nup170 regulates this process, we used protein-protein interactions, genetic interactions, and transcriptome correlation analyses to identify the Ctf18-RFC complex, an alternative proliferating cell nuclear antigen (PCNA) loader, as a facilitator of the gene regulatory functions of Nup170. The Ctf18-RFC complex is recruited to a subpopulation of NPCs that lack the nuclear basket proteins Mlp1 and Mlp2. In the absence of Nup170, PCNA levels on DNA are reduced, resulting in the loss of silencing of subtelomeric genes. Increasing PCNA levels on DNA by removing Elg1, which is required for PCNA unloading, rescues subtelomeric silencing defects in nup170Δ. The NPC, therefore, mediates subtelomeric gene silencing by regulating PCNA levels on DNA.


Assuntos
Cromatina , Inativação Gênica , Poro Nuclear , Antígeno Nuclear de Célula em Proliferação , Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae , Telômero , Proteínas de Transporte/genética , Proteínas de Transporte/metabolismo , Cromatina/genética , Cromatina/metabolismo , Poro Nuclear/química , Poro Nuclear/metabolismo , Antígeno Nuclear de Célula em Proliferação/genética , Antígeno Nuclear de Célula em Proliferação/metabolismo , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Telômero/genética , Telômero/metabolismo , DNA Fúngico/metabolismo
10.
Nature ; 618(7964): 411-418, 2023 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-37258668

RESUMO

The nuclear pore complex (NPC) is the bidirectional gate that mediates the exchange of macromolecules or their assemblies between nucleus and cytoplasm1-3. The assembly intermediates of the ribosomal subunits, pre-60S and pre-40S particles, are among the largest cargoes of the NPC and the export of these gigantic ribonucleoproteins requires numerous export factors4,5. Here we report the cryo-electron microscopy structure of native pre-60S particles trapped in the channel of yeast NPCs. In addition to known assembly factors, multiple factors with export functions are also included in the structure. These factors in general bind to either the flexible regions or subunit interface of the pre-60S particle, and virtually form many anchor sites for NPC binding. Through interactions with phenylalanine-glycine (FG) repeats from various nucleoporins of NPC, these factors collectively facilitate the passage of the pre-60S particle through the central FG repeat network of the NPC. Moreover, in silico analysis of the axial and radial distribution of pre-60S particles within the NPC shows that a single NPC can take up to four pre-60S particles simultaneously, and pre-60S particles are enriched in the inner ring regions close to the wall of the NPC with the solvent-exposed surface facing the centre of the nuclear pore. Our data suggest a translocation model for the export of pre-60S particles through the NPC.


Assuntos
Transporte Ativo do Núcleo Celular , Poro Nuclear , Saccharomyces cerevisiae , Microscopia Crioeletrônica , Poro Nuclear/química , Poro Nuclear/metabolismo , Poro Nuclear/ultraestrutura , Complexo de Proteínas Formadoras de Poros Nucleares/química , Complexo de Proteínas Formadoras de Poros Nucleares/metabolismo , Complexo de Proteínas Formadoras de Poros Nucleares/ultraestrutura , Saccharomyces cerevisiae/citologia , Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/ultraestrutura , Proteínas de Saccharomyces cerevisiae/química , Proteínas de Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/ultraestrutura , Subunidades Proteicas/química , Subunidades Proteicas/metabolismo , Fenilalanina , Glicina , Simulação por Computador , Solventes
11.
J Mol Biol ; 435(9): 168051, 2023 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-36933820

RESUMO

The nuclear pore complex (NPC) is a giant protein assembly that penetrates the double layers of the nuclear membrane. The overall structure of the NPC has approximately eightfold symmetry and is formed by approximately 30 nucleoporins. The great size and complexity of the NPC have hindered the study of its structure for many years until recent breakthroughs were achieved by integrating the latest high-resolution cryo-electron microscopy (cryo-EM), the emerging artificial intelligence-based modeling and all other available structural information from crystallography and mass spectrometry. Here, we review our latest knowledge of the NPC architecture and the history of its structural study from in vitro to in situ with progressively improved resolutions by cryo-EM, with a particular focus on the latest subnanometer-resolution structural studies. The future directions for structural studies of NPCs are also discussed.


Assuntos
Inteligência Artificial , Complexo de Proteínas Formadoras de Poros Nucleares , Poro Nuclear , Microscopia Crioeletrônica/métodos , Membrana Nuclear , Poro Nuclear/química , Complexo de Proteínas Formadoras de Poros Nucleares/química
12.
Nanoscale ; 15(12): 5756-5770, 2023 Mar 23.
Artigo em Inglês | MEDLINE | ID: mdl-36786384

RESUMO

Nuclear pore complexes (NPCs) are the only gateways between the nucleus and cytoplasm in eukaryotic cells. They restrict free diffusion to molecules below 5 nm while facilitating the active transport of selected cargoes, sometimes as large as the pore itself. This versatility implies an important pore plasticity. Recently, cryo-EM and AI-based protein modeling of human NPC revealed with acute precision how most constituents are arranged. But the basket, a fish trap-like structure capping the nucleoplasmic side of the pore, remains poorly resolved. Here by atomic force microscopy (AFM) coupled to single molecule localization microscopy (SMLM) we revealed that the basket is very soft and explores a large conformational landscape: apart from its canonical basket shape, it dives into the central pore channel or opens, with filaments reaching to the pore sides. Our observations highlight how this structure can adapt and let morphologically diverse cargoes shuttle through NPCs.


Assuntos
Núcleo Celular , Poro Nuclear , Animais , Humanos , Poro Nuclear/química , Poro Nuclear/metabolismo , Microscopia de Força Atômica , Núcleo Celular/metabolismo , Citoplasma/metabolismo , Células Eucarióticas/metabolismo
13.
Curr Opin Struct Biol ; 78: 102523, 2023 02.
Artigo em Inglês | MEDLINE | ID: mdl-36641895

RESUMO

The nuclear pore complex (NPC) is a supra-molecular assembly that mediates substance and information flow across the nuclear envelope (NE). Due to its extraordinary size and complexity, the NPC remains one of the most challenging tasks in structural elucidation at atomic resolution. Recent breakthroughs in cryo-electron microscopy (cryo-EM) reconstruction, Machine Learning empowered structure prediction and biochemical reconstitution have combined to yield molecular models of the NPC at unprecedented accuracy. Furthermore, in cellulo cryo-electron tomography (cryo-ET) structures reveal substantial structural dynamics of the NPC. These advances shed light on the organizational principles and functions of the NPC.


Assuntos
Membrana Nuclear , Poro Nuclear , Poro Nuclear/química , Microscopia Crioeletrônica , Complexo de Proteínas Formadoras de Poros Nucleares/química , Modelos Moleculares
14.
Nature ; 613(7944): 575-581, 2023 01.
Artigo em Inglês | MEDLINE | ID: mdl-36599981

RESUMO

Understanding how the nuclear pore complex (NPC) is assembled is of fundamental importance to grasp the mechanisms behind its essential function and understand its role during the evolution of eukaryotes1-4. There are at least two NPC assembly pathways-one during the exit from mitosis and one during nuclear growth in interphase-but we currently lack a quantitative map of these events. Here we use fluorescence correlation spectroscopy calibrated live imaging of endogenously fluorescently tagged nucleoporins to map the changes in the composition and stoichiometry of seven major modules of the human NPC during its assembly in single dividing cells. This systematic quantitative map reveals that the two assembly pathways have distinct molecular mechanisms, in which the order of addition of two large structural components, the central ring complex and nuclear filaments are inverted. The dynamic stoichiometry data was integrated to create a spatiotemporal model of the NPC assembly pathway and predict the structures of postmitotic NPC assembly intermediates.


Assuntos
Complexo de Proteínas Formadoras de Poros Nucleares , Poro Nuclear , Humanos , Interfase , Mitose , Poro Nuclear/química , Poro Nuclear/metabolismo , Complexo de Proteínas Formadoras de Poros Nucleares/química , Complexo de Proteínas Formadoras de Poros Nucleares/metabolismo , Espectrometria de Fluorescência
15.
Front Biosci (Landmark Ed) ; 28(12): 350, 2023 12 27.
Artigo em Inglês | MEDLINE | ID: mdl-38179752

RESUMO

Nuclear pore complexes (NPCs) are intricate intracellular structures composed of approximately 30 nuclear pore proteins (NUPs) that regulate the transport of materials between the nucleus and cytoplasm in eukaryotic cells. The heart is a crucial organ for sustaining the vital functions of the body, pumping blood rich in nutrients and energy to all organs and tissues. Recent studies have shown that NPCs play pivotal roles not only in normal cardiac physiological processes such as myocardial cell proliferation and differentiation but also in various pathological processes such as ischemic and hypoxic myocardial injury. Due to their mass and complicated nature, the structures of NPCs have been challenging to identify by the scientific community. With the development of cryo-electron microscopy and advanced sampling techniques, researchers have made significant progress in understanding the structures of NPCs. This review aims to summarize the latest research on the structural aspects of NPCs and their roles in cardiac physiology and pathology, increase the understanding of the intricate mechanisms of NPC actions, provide valuable insights into the pathogenesis of heart diseases and describe the development of potential novel therapeutic strategies.


Assuntos
Complexo de Proteínas Formadoras de Poros Nucleares , Poro Nuclear , Complexo de Proteínas Formadoras de Poros Nucleares/análise , Complexo de Proteínas Formadoras de Poros Nucleares/química , Complexo de Proteínas Formadoras de Poros Nucleares/metabolismo , Transporte Ativo do Núcleo Celular/fisiologia , Microscopia Crioeletrônica , Poro Nuclear/química , Poro Nuclear/metabolismo , Citoplasma/metabolismo
16.
Nat Chem ; 14(11): 1278-1285, 2022 11.
Artigo em Inglês | MEDLINE | ID: mdl-36138110

RESUMO

Proteins that contain repeat phenylalanine-glycine (FG) residues phase separate into oncogenic transcription factor condensates in malignant leukaemias, form the permeability barrier of the nuclear pore complex and mislocalize in neurodegenerative diseases. Insights into the molecular interactions of FG-repeat nucleoporins have, however, remained largely elusive. Using a combination of NMR spectroscopy and cryoelectron microscopy, we have identified uniformly spaced segments of transient ß-structure and a stable preformed α-helix recognized by messenger RNA export factors in the FG-repeat domain of human nucleoporin 98 (Nup98). In addition, we have determined at high resolution the molecular organization of reversible FG-FG interactions in amyloid fibrils formed by a highly aggregation-prone segment in Nup98. We have further demonstrated that amyloid-like aggregates of the FG-repeat domain of Nup98 have low stability and are reversible. Our results provide critical insights into the molecular interactions underlying the self-association and phase separation of FG-repeat nucleoporins in physiological and pathological cell activities.


Assuntos
Complexo de Proteínas Formadoras de Poros Nucleares , Poro Nuclear , Humanos , Microscopia Crioeletrônica , Poro Nuclear/química , Poro Nuclear/metabolismo , Complexo de Proteínas Formadoras de Poros Nucleares/genética , Complexo de Proteínas Formadoras de Poros Nucleares/análise , Complexo de Proteínas Formadoras de Poros Nucleares/química , Fenilalanina/química , Sequências Repetitivas de Aminoácidos
17.
Artigo em Inglês | MEDLINE | ID: mdl-36096637

RESUMO

The nucleus, a genome-containing organelle eponymous of eukaryotes, is enclosed by a double membrane continuous with the endoplasmic reticulum. The nuclear pore complex (NPC) is an ∼110-MDa, ∼1000-protein channel that selectively transports macromolecules across the nuclear envelope and thus plays a central role in the regulated flow of genetic information from transcription to translation. Its size, complexity, and flexibility have hindered determination of atomistic structures of intact NPCs. Recent studies have overcome these hurdles by combining biochemical reconstitution and docking of high-resolution structures of NPC subcomplexes into cryo-electron tomographic reconstructions with biochemical and physiological validation. Here, we provide an overview of the near-atomic composite structure of the human NPC, a milestone toward unlocking a molecular understanding of mRNA export, NPC-associated diseases, and viral host-pathogen interactions, serving as a paradigm for studying similarly large complexes.


Assuntos
Núcleo Celular , Poro Nuclear , Humanos , Poro Nuclear/química , Poro Nuclear/metabolismo , Transporte Ativo do Núcleo Celular , Retículo Endoplasmático , Eucariotos , Membrana Nuclear/metabolismo
18.
mBio ; 13(5): e0181522, 2022 10 26.
Artigo em Inglês | MEDLINE | ID: mdl-36040030

RESUMO

Twenty years since the publication of the Plasmodium falciparum and P. berghei genomes one-third of their protein-coding genes still lack functional annotation. In the absence of sequence and structural homology, protein-protein interactions can facilitate functional prediction of such orphan genes by mapping protein complexes in their natural cellular environment. The Plasmodium nuclear pore complex (NPC) is a case in point: it remains poorly defined; its constituents lack conservation with the 30+ proteins described in the NPC of many opisthokonts, a clade of eukaryotes that includes fungi and animals, but not Plasmodium. Here, we developed a labeling methodology based on TurboID fusion proteins, which allows visualization of the P. berghei NPC and facilitates the identification of its components. Following affinity purification and mass spectrometry, we identified 4 known nucleoporins (Nups) (138, 205, 221, and the bait 313), and verify interaction with the putative phenylalanine-glycine (FG) Nup637; we assigned 5 proteins lacking annotation (and therefore meaningful homology with proteins outside the genus) to the NPC, which is confirmed by green fluorescent protein (GFP) tagging. Based on gene deletion attempts, all new Nups - Nup176, 269, 335, 390, and 434 - are essential to parasite survival. They lack primary sequence homology with proteins outside the Plasmodium genus; albeit 2 incorporate short domains with structural homology to human Nup155 and yeast Nup157, and the condensin SMC (Structural Maintenance Of Chromosomes 4). The protocols developed here showcase the power of proximity labeling for elucidating protein complex composition and annotation of taxonomically restricted genes in Plasmodium. It opens the door to exploring the function of the Plasmodium NPC and understanding its evolutionary position. IMPORTANCE The nuclear pore complex (NPC) is a platform for constant evolution and has been used to study the evolutionary patterns of early-branching eukaryotes. The Plasmodium NPC is poorly defined due to its evolutionary divergent nature making it impossible to characterize it via homology searches. Although 2 decades have passed since the publication of the Plasmodium genome, 30% of the genes still lack functional annotation. Our study demonstrates the ability of proximity labeling using TurboID to assign function to orphan proteins in the malaria parasite. We have identified a total of 10 Nups that will allow further study of NPC dynamics, structural elements, involvement in nucleocytoplasmic transport, and unique non-transport functions of nucleoporins that provide adaptability to this malaria parasite.


Assuntos
Malária , Poro Nuclear , Humanos , Transporte Ativo do Núcleo Celular/genética , Glicina/metabolismo , Proteínas de Fluorescência Verde/análise , Malária/metabolismo , Poro Nuclear/química , Poro Nuclear/genética , Poro Nuclear/metabolismo , Complexo de Proteínas Formadoras de Poros Nucleares/genética , Complexo de Proteínas Formadoras de Poros Nucleares/metabolismo , Fenilalanina/química , Plasmodium berghei/genética , Plasmodium berghei/metabolismo , Saccharomyces cerevisiae/metabolismo
19.
Science ; 376(6598): eabm9506, 2022 06 10.
Artigo em Inglês | MEDLINE | ID: mdl-35679397

RESUMO

INTRODUCTION The eukaryotic nucleus pro-tects the genome and is enclosed by the two membranes of the nuclear envelope. Nuclear pore complexes (NPCs) perforate the nuclear envelope to facilitate nucleocytoplasmic transport. With a molecular weight of ∼120 MDa, the human NPC is one of the larg-est protein complexes. Its ~1000 proteins are taken in multiple copies from a set of about 30 distinct nucleoporins (NUPs). They can be roughly categorized into two classes. Scaf-fold NUPs contain folded domains and form a cylindrical scaffold architecture around a central channel. Intrinsically disordered NUPs line the scaffold and extend into the central channel, where they interact with cargo complexes. The NPC architecture is highly dynamic. It responds to changes in nuclear envelope tension with conforma-tional breathing that manifests in dilation and constriction movements. Elucidating the scaffold architecture, ultimately at atomic resolution, will be important for gaining a more precise understanding of NPC function and dynamics but imposes a substantial chal-lenge for structural biologists. RATIONALE Considerable progress has been made toward this goal by a joint effort in the field. A synergistic combination of complementary approaches has turned out to be critical. In situ structural biology techniques were used to reveal the overall layout of the NPC scaffold that defines the spatial reference for molecular modeling. High-resolution structures of many NUPs were determined in vitro. Proteomic analysis and extensive biochemical work unraveled the interaction network of NUPs. Integra-tive modeling has been used to combine the different types of data, resulting in a rough outline of the NPC scaffold. Previous struc-tural models of the human NPC, however, were patchy and limited in accuracy owing to several challenges: (i) Many of the high-resolution structures of individual NUPs have been solved from distantly related species and, consequently, do not comprehensively cover their human counterparts. (ii) The scaf-fold is interconnected by a set of intrinsically disordered linker NUPs that are not straight-forwardly accessible to common structural biology techniques. (iii) The NPC scaffold intimately embraces the fused inner and outer nuclear membranes in a distinctive topol-ogy and cannot be studied in isolation. (iv) The conformational dynamics of scaffold NUPs limits the resolution achievable in structure determination. RESULTS In this study, we used artificial intelligence (AI)-based prediction to generate an exten-sive repertoire of structural models of human NUPs and their subcomplexes. The resulting models cover various domains and interfaces that so far remained structurally uncharac-terized. Benchmarking against previous and unpublished x-ray and cryo-electron micros-copy structures revealed unprecedented accu-racy. We obtained well-resolved cryo-electron tomographic maps of both the constricted and dilated conformational states of the hu-man NPC. Using integrative modeling, we fit-ted the structural models of individual NUPs into the cryo-electron microscopy maps. We explicitly included several linker NUPs and traced their trajectory through the NPC scaf-fold. We elucidated in great detail how mem-brane-associated and transmembrane NUPs are distributed across the fusion topology of both nuclear membranes. The resulting architectural model increases the structural coverage of the human NPC scaffold by about twofold. We extensively validated our model against both earlier and new experimental data. The completeness of our model has enabled microsecond-long coarse-grained molecular dynamics simulations of the NPC scaffold within an explicit membrane en-vironment and solvent. These simulations reveal that the NPC scaffold prevents the constriction of the otherwise stable double-membrane fusion pore to small diameters in the absence of membrane tension. CONCLUSION Our 70-MDa atomically re-solved model covers >90% of the human NPC scaffold. It captures conforma-tional changes that occur during dilation and constriction. It also reveals the precise anchoring sites for intrinsically disordered NUPs, the identification of which is a prerequisite for a complete and dy-namic model of the NPC. Our study exempli-fies how AI-based structure prediction may accelerate the elucidation of subcellular ar-chitecture at atomic resolution. [Figure: see text].


Assuntos
Inteligência Artificial , Complexo de Proteínas Formadoras de Poros Nucleares , Poro Nuclear , Transporte Ativo do Núcleo Celular , Microscopia Crioeletrônica , Humanos , Simulação de Dinâmica Molecular , Poro Nuclear/química , Complexo de Proteínas Formadoras de Poros Nucleares/química , Proteômica
20.
Science ; 376(6598): 1158-1159, 2022 06 10.
Artigo em Inglês | MEDLINE | ID: mdl-35679398
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