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Nucleus (Austin, Tex.) 2014Nuclear pore complexes are large macromolecular assemblies that facilitate the nucleocytoplasmic exchange of macromolecules. Because of their intricate composition,... (Review)
Review
Nuclear pore complexes are large macromolecular assemblies that facilitate the nucleocytoplasmic exchange of macromolecules. Because of their intricate composition, membrane association, and sheer size, the integration of various, complementary structure determination approaches is a prerequisite for elucidating their structure. We have recently employed such an integrated strategy to analyze the scaffold structure of the cytoplasmic and nuclear rings of the human nuclear pore complex. In this extra view, we highlight two specific aspects of this work: the power of electron microscopy for bridging different resolution regimes and the importance of post-translational modifications for regulating nucleoporin interactions. We review recent technological developments and give a perspective toward future structure determination approaches.
Topics: Animals; Humans; Nuclear Pore; Spine
PubMed: 24699243
DOI: 10.4161/nucl.28739 -
Cell May 2018Fusion is thought to open a pore to release vesicular cargoes vital for many biological processes, including exocytosis, intracellular trafficking, fertilization, and...
Fusion is thought to open a pore to release vesicular cargoes vital for many biological processes, including exocytosis, intracellular trafficking, fertilization, and viral entry. However, fusion pores have not been observed and thus proved in live cells. Its regulatory mechanisms and functions remain poorly understood. With super-resolution STED microscopy, we observed dynamic fusion pore behaviors in live (neuroendocrine) cells, including opening, expansion, constriction, and closure, where pore size may vary between 0 and 490 nm within 26 milliseconds to seconds (vesicle size: 180-720 nm). These pore dynamics crucially determine the efficiency of vesicular cargo release and vesicle retrieval. They are generated by competition between pore expansion and constriction. Pharmacology and mutation experiments suggest that expansion and constriction are mediated by F-actin-dependent membrane tension and calcium/dynamin, respectively. These findings provide the missing live-cell evidence, proving the fusion-pore hypothesis, and establish a live-cell dynamic-pore theory accounting for fusion, fission, and their regulation.
Topics: Actins; Animals; Calcium; Cattle; Cell Membrane; Chromaffin Cells; Dynamins; Electric Stimulation; Endocytosis; Fluorescent Dyes; Male; Membrane Fusion; Microscopy, Confocal; Models, Biological; Patch-Clamp Techniques; Secretory Vesicles
PubMed: 29606354
DOI: 10.1016/j.cell.2018.02.062 -
Current Opinion in Cell Biology Jun 2017The study of the nuclear pore complex (NPC) is a fascinating endeavor, as it not only implies uncovering the 'engineering marvel' of its architecture and function, but... (Review)
Review
The study of the nuclear pore complex (NPC) is a fascinating endeavor, as it not only implies uncovering the 'engineering marvel' of its architecture and function, but also provides a key window into a significant evolutionary event: the origin of the eukaryotic cell. The combined efforts of many groups in the field, with the help of novel methodologies and new model organisms, are facilitating a much deeper understanding of this complex assembly. Here we cover recent advances on the characterization of the structure of the NPC scaffold and of the biophysical mechanisms that define the permeability barrier. We identify common architectural and functional principles between those two NPC compartments, expanding the previous protocoatomer hypothesis to suggest possible evolutionary origins for the FG nucleoporins and the NPC permeability barrier.
Topics: Active Transport, Cell Nucleus; Cell Nucleus; Eukaryotic Cells; Evolution, Molecular; Nuclear Pore; Nuclear Pore Complex Proteins
PubMed: 28624666
DOI: 10.1016/j.ceb.2017.05.003 -
Scientific Reports Nov 2017Nuclear pore complexes (NPCs) maintain cellular homeostasis by mediating nucleocytoplasmic transport. Although cyclin-dependent kinases (CDKs) regulate NPC assembly in...
Nuclear pore complexes (NPCs) maintain cellular homeostasis by mediating nucleocytoplasmic transport. Although cyclin-dependent kinases (CDKs) regulate NPC assembly in interphase, the location of NPC assembly on the nuclear envelope is not clear. CDKs also regulate the disappearance of pore-free islands, which are nuclear envelope subdomains; this subdomain gradually disappears with increase in homogeneity of the NPC in response to CDK activity. However, a causal relationship between pore-free islands and NPC assembly remains unclear. Here, we elucidated mechanisms underlying NPC assembly from a new perspective by focusing on pore-free islands. We proposed a novel framework for image-based analysis to automatically determine the detailed 'landscape' of pore-free islands from a large quantity of images, leading to the identification of NPC intermediates that appear in pore-free islands with increased frequency in response to CDK activity. Comparison of the spatial distribution between simulated and the observed NPC intermediates within pore-free islands showed that their distribution was spatially biased. These results suggested that the disappearance of pore-free islands is highly related to de novo NPC assembly and indicated the existence of specific regulatory mechanisms for the spatial arrangement of NPC assembly on nuclear envelopes.
Topics: Active Transport, Cell Nucleus; Animals; Cell Line, Tumor; Cyclin-Dependent Kinases; HeLa Cells; Humans; Membrane Glycoproteins; Nuclear Envelope; Nuclear Pore; Nuclear Pore Complex Proteins; Rats
PubMed: 29176624
DOI: 10.1038/s41598-017-16386-2 -
International Journal of Pharmaceutics:... Dec 2019In this study, the influence of the mesoporous silica (MS) textural properties (surface area, pore diameter, and pore volume) on drug loading capacity (monomolecular...
In this study, the influence of the mesoporous silica (MS) textural properties (surface area, pore diameter, and pore volume) on drug loading capacity (monomolecular loading capacity and pore filling capacity) was investigated theoretically and experimentally using a thermoanalytical method. The loading capacities of three model drugs (celecoxib, cinnarizine, and paracetamol) were determined in five different MS grades of Sylysia® with identical chemical composition, but varying surface area, pore diameter and pore volume. The experimentally determined loading capacities were compared to theoretical loading capacities, calculated based on the surface area and amorphous density of the drugs, and the surface area and pore volume of the MS. The findings of the study showed that the monomolecular loading capacity generally increased with increasing surface area and decreasing pore volume of the MS. However, the MS grade with the highest surface area did not display the highest monomolecular loading capacity for any of the three drugs. This was probably a result of the decreasing pore diameter necessary to accommodate the increasing surface area of the MS i.e., if the pore is smaller than the drug molecule, the drug cannot access the available surface area. For these systems, the amorphous density of the drug and the pore volume of the MS was used to estimate the theoretical pore filling capacity, which was in good agreement with the experimentally determined loading capacity. In conclusion, this study showed that both the pore volume and surface area of the MS will have an influence on the drug loading capacity and that this can be estimated with good accuracy both theoretically and experimentally.
PubMed: 31517273
DOI: 10.1016/j.ijpx.2019.100008 -
Cell Calcium Jul 2018Mitochondria from different organisms can undergo a sudden process of inner membrane unselective leakiness to molecules known as the mitochondrial permeability... (Review)
Review
Mitochondria from different organisms can undergo a sudden process of inner membrane unselective leakiness to molecules known as the mitochondrial permeability transition (MPT). This process has been studied for nearly four decades and several proteins have been claimed to constitute, or at least regulate the usually inactive pore responsible for this transition. However, no protein candidate proposed as the actual pore-forming unit has passed rigorous gain- or loss-of-function genetic tests. Here we review evidence for -and against- putative channel-forming components of the MPT pore. We conclude that the structure of the MPT pore still remains largely undefined and suggest that future studies should follow established technical considerations to unambiguously consolidate the channel forming constituent(s) of the MPT pore.
Topics: Animals; Apoptosis; Calcium; Cyclophilins; Humans; Mitochondria; Mitochondrial Membrane Transport Proteins; Mitochondrial Membranes; Mitochondrial Permeability Transition Pore
PubMed: 29793100
DOI: 10.1016/j.ceca.2018.05.003 -
ACS Omega Oct 2022A major historical breakthrough has been made in the exploration of the GK (the first member of the Qingshankou Formation (K2qn), Gulong Sag) shale oil of the Songliao...
A major historical breakthrough has been made in the exploration of the GK (the first member of the Qingshankou Formation (K2qn), Gulong Sag) shale oil of the Songliao Basin. However, few reports have been reported on the pore structure characteristics of this large-scale lacustrine medium-high maturity shale. In addition, the difference between the pore structure characteristics of the GK shale and medium-low maturity marine/continental shale is unknown, and the affecting factors of pore development are still unclear. Therefore, in order to clarify the pore structure characteristics of the GK shale and its affecting factors, this study characterized them experimentally and revealed the law of pore evolution using the mineral composition and geochemical analysis, microscopic observations, and pore quantification techniques. Results indicate that (1) the pore system of GK shale reservoirs is divided into micropores (pore diameter < 10 nm), mesopores (10 nm < pore diameter < 50 nm), and macropores (pore diameter > 50 nm); (2) the pore structure of the GK shale is mainly affected by the clay content, siliceous mineral content, and thermal maturity; and (3) when the content of clay minerals and siliceous minerals in the GK shale reservoir is high, and ∼0.8% < < ∼1.4%, the storage capacity and oil content of the GK shale show high values, and it can be considered as a strong candidate for further exploration and development. This research can push the shale oil revolution to a new height and is significant to promote the development of the petroleum industry.
PubMed: 36249366
DOI: 10.1021/acsomega.2c03804 -
Materials (Basel, Switzerland) Oct 2021To explore the effects of thermal actions on the pore structural features of granite, scanning electron microscope (SEM) and mercury injection experiments were carried...
To explore the effects of thermal actions on the pore structural features of granite, scanning electron microscope (SEM) and mercury injection experiments were carried out on granite after thermal treatment (25 °C to 400 °C). The pore structure was investigated from various perspectives, including the capillary pressure curve, the pore-throat ratio, the median saturation pressure, the median pore-throat radius, the porosity, the pore volume, and the pore size distribution. Based on mercury intrusion test data, the Winland model of permeability prediction was modified for a high-temperature tight granite reservoir. The results showed that: (1) As the temperature rose, the mercury injection curve was gradually flattened, and the mercury ejection efficiency gradually increased. Meanwhile, the pore-throat ratio and the median saturation pressure decreased exponentially, and the pore connectivity was enhanced. (2) The median pore-throat radius and the porosity of granite increased exponentially as the temperature increased. Above 200 °C, the median pore-throat radius and the porosity increased substantially. (3) The pore volumes of the transitional pores, mesopores and macropores, and the total pore volume inside the granite, increased as the temperature rose. Especially above 200 °C, the transitional pores and the mesopores were prominently developed, and the pore volumes of the transitional pores and the mesopores took up a significantly greater proportion of the total pore volume. (4) As the temperature rose, the pore size distribution of granite became more extensive, the pore-throat structure was obviously developed, and the pore-throat connectivity was enhanced. (5) The relationship between the micropores' characteristic parameters and the macro-permeability in engineering was established though a modified Winland model, and the modified Winland model had a better prediction effect. The findings provide a solid basis for rock geothermal mining projects and related geotechnical engineering.
PubMed: 34771994
DOI: 10.3390/ma14216470 -
Methods in Molecular Biology (Clifton,... 2022The nuclear pore complex (NPC) is the conduit in the nuclear envelope through which proteins and RNA are transported between the cytoplasm and nucleus. Xenopus egg...
The nuclear pore complex (NPC) is the conduit in the nuclear envelope through which proteins and RNA are transported between the cytoplasm and nucleus. Xenopus egg extracts that support de novo assembly of nuclei have provided a robust system to study NPC structure and function because the biochemical composition of the extract can be easily manipulated. Here we describe how to assemble nuclei in Xenopus egg extract, how to visualize and analyze NPCs in both live and fixed samples, and different approaches to altering nucleocytoplasmic transport in extract.
Topics: Active Transport, Cell Nucleus; Animals; Cell Nucleus; Microscopy; Nuclear Envelope; Nuclear Pore; Nuclear Pore Complex Proteins; Xenopus laevis
PubMed: 35412252
DOI: 10.1007/978-1-0716-2337-4_25 -
Frontiers in Physiology 2018In the last three decades, all efforts in bone tissue engineering were driven by the dogma that the ideal pore size in bone substitutes lies between 0.3 and 0.5 mm in...
In the last three decades, all efforts in bone tissue engineering were driven by the dogma that the ideal pore size in bone substitutes lies between 0.3 and 0.5 mm in diameter. Newly developed additive manufacturing methodologies for ceramics facilitate the total control over pore size, pore distribution, bottleneck size, and bottleneck distribution. Therefore, this appears to be the method of choice with which to test the aforementioned characteristics of an ideal bone substitute. To this end, we produced a library of 15 scaffolds with diverse defined pore/bottleneck dimensions and distributions, tested them in a calvarial bone defect model in rabbits, and assessed the clinically most relevant parameters: defect bridging and bony regenerated area. Our data revealed that the ideal pore/bottleneck dimension for bone substitutes is in the range of 0.7-1.2 mm, and appears therefore to be twofold to fourfold more extended than previously thought. Pore/bottleneck dimensions of 1.5 and 1.7 mm perform significantly worse and appear unsuitable in bone substitutes. Thus, our results set the ideal range of pore/bottleneck dimensions and are likely to have a significant impact on the microarchitectural design of future bone substitutes for use in orthopedic, trauma, cranio-maxillofacial and oral surgery.
PubMed: 30072920
DOI: 10.3389/fphys.2018.00960