scholarly journals Nuclear envelope budding is an evolutionary conserved phenomenon

2018 ◽  
Author(s):  
Dimitra Panagaki ◽  
Richard Neutze ◽  
Johanna L. Höög
Keyword(s):  
Nuclear Envelope ◽  
Trypanosoma Brucei ◽  
Electron Tomography ◽  
Human Cell Line ◽  
Eukaryotic Cells ◽  
Nuclear Pores ◽  
Dna Transport ◽  
Parasitic Protist ◽  
3D Architecture ◽  
Cellular Dna

AbstractEukaryotic cells are defined by the compartmentalization of the cytoplasm into organelles, the largest of which is the nucleus, which contains the cellular DNA. Transport into and out of the nucleus is highly regulated and is traditionally thought to occur solely through nuclear pores. However, a small number of papers has repeatedly shown vesicular budding from the nuclear envelopes in different organisms. We used electron microscopy to identify such nuclear envelope budding events in a human cell line,Caenorhabditis elegansworms, the two yeastsSaccharomyces cerevisiaeandSchizosaccharomyces pombeand the parasitic protistTrypanosoma brucei. Progressing to electron tomography, the finer details of the 3D architecture of such budding events was revealed. We summarize all the organisms in which this mode of translocation over the nuclear envelope has been observed and conclude that this may be a fundamental, evolutionary conserved mechanism of transport inside eukaryotic cells.

scholarly journals Structure of the trypanosome paraflagellar rod and insights into non-planar motility of eukaryotic cells

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Jiayan Zhang ◽  
Hui Wang ◽  
Simon Imhof ◽  
Xueting Zhou ◽  
Shiqing Liao ◽  
...  
Keyword(s):  
Trypanosoma Brucei ◽  
Disease Transmission ◽  
Electron Tomography ◽  
Signal Transmission ◽  
Protozoan Parasite ◽  
Empty Space ◽  
Eukaryotic Cells ◽  
Critical Gap ◽  
Proximal Zone ◽  
Paracrystalline Array

AbstractEukaryotic flagella (synonymous with cilia) rely on a microtubule-based axoneme, together with accessory filaments to carryout motility and signaling functions. While axoneme structures are well characterized, 3D ultrastructure of accessory filaments and their axoneme interface are mostly unknown, presenting a critical gap in understanding structural foundations of eukaryotic flagella. In the flagellum of the protozoan parasite Trypanosoma brucei (T. brucei), the axoneme is accompanied by a paraflagellar rod (PFR) that supports non-planar motility and signaling necessary for disease transmission and pathogenesis. Here, we employed cryogenic electron tomography (cryoET) with sub-tomographic averaging, to obtain structures of the PFR, PFR-axoneme connectors (PACs), and the axonemal central pair complex (CPC). The structures resolve how the 8 nm repeat of the axonemal tubulin dimer interfaces with the 54 nm repeat of the PFR, which consist of proximal, intermediate, and distal zones. In the distal zone, stacked “density scissors” connect with one another to form a “scissors stack network (SSN)” plane oriented 45° to the axoneme axis; and ~370 parallel SSN planes are connected by helix-rich wires into a paracrystalline array with ~90% empty space. Connections from these wires to the intermediate zone, then to overlapping layers of the proximal zone and to the PACs, and ultimately to the CPC, point to a contiguous pathway for signal transmission. Together, our findings provide insights into flagellum-driven, non-planar helical motility of T. brucei and have broad implications ranging from cell motility and tensegrity in biology, to engineering principles in bionics.

scholarly journals Exotic mitotic mechanisms

Open Biology ◽  
2012 ◽  
Vol 2 (12) ◽  
pp. 120140 ◽  
Author(s):  
Hauke Drechsler ◽  
Andrew D. McAinsh
Keyword(s):  
Nuclear Envelope ◽  
Chromosome Segregation ◽  
Eukaryotic Cells ◽  
Nuclear Pores ◽  
Physical Relationship ◽  
Physical Separation ◽  
Microtubule Organizing Centres ◽  
New Challenges ◽  
Linear Chromosomes

The emergence of eukaryotes around two billion years ago provided new challenges for the chromosome segregation machineries: the physical separation of multiple large and linear chromosomes from the microtubule-organizing centres by the nuclear envelope. In this review, we set out the diverse solutions that eukaryotic cells use to solve this problem, and show how stepping away from ‘mainstream’ mitosis can teach us much about the mechanisms and mechanics that can drive chromosome segregation. We discuss the evidence for a close functional and physical relationship between membranes, nuclear pores and kinetochores in generating the forces necessary for chromosome segregation during mitosis.

High-voltage cytochemistry for three-dimensional observation of nuclei and calculation of total numbers of nuclear pores in retinal Mueller glia

1990 ◽  
Vol 48 (3) ◽  
pp. 956-957
Author(s):  
H. Ishigooka ◽  
S. Ueno ◽  
L.M. Hjelmeland ◽  
M.B. Landers ◽  
K. Ogawa
Keyword(s):  
Nuclear Envelope ◽  
High Voltage ◽  
Three Dimensional ◽  
Reaction Medium ◽  
Nuclear Pores ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
High Voltage Electron ◽  
G6pase Activity ◽  
Mueller Glia

Introduction: We have demonstrated that Glucose-6-phosphatase (G6Pase) activity is localized to the endoplasmic reticulum and nuclear envelope of Mueller glia in the normal and pathological guinea pig retina. Using a combination of this cytochemical technique and high voltage electron microscopy, the distribution of nuclear pores could be clearly observed on the nuclear envelope of Mueller glia because of their anatomical lack of reaction products. This technique was developed to study the three-dimensional structure of nuclei and to calculate total numbers of nuclear pores utilizing a computer graphic analysis system in the normal and pathological retina.Materials and methods: Normal and photocoagulated retina of pigmented adult guinea pigs were perfused with a cold mixture of 0.25% glutaraldehyde and 2% paraformaldehyde in 0.1M cacodylate buffer, and the enucleated globes were hemisected and immersed in the same fixative for 30 min. After sectioning and incubation in the reaction medium for the detection of G6Pase activity by the method of Wachstein-Meisel, the sections were postfixed, dehydrated and embedded in Spurr’s epoxy resin. Serial thick sections (1.0um) were prepared for the observation by a Hitachi high voltage electron microscope (H 1250-M) with an accelerating voltage of 1000 Kv. and pictures were analyzed and three-dimensionally reconstructed by TRI (RATOC Co., Ltd.).

scholarly journals Mating compatibility in the parasitic protist Trypanosoma brucei

2014 ◽  
Vol 7 (1) ◽  
pp. 78 ◽  
Author(s):  
Lori Peacock ◽  
Vanessa Ferris ◽  
Mick Bailey ◽  
Wendy Gibson
Keyword(s):  
Trypanosoma Brucei ◽  
Mating Compatibility ◽  
Parasitic Protist

The plant nuclear envelope in focus

2010 ◽  
Vol 38 (1) ◽  
pp. 307-311 ◽  
Author(s):  
Katja Graumann ◽  
David E. Evans
Keyword(s):  
Nuclear Envelope ◽  
Recent Progress ◽  
Protein Targeting ◽  
Nuclear Pores ◽  
Associated Proteins ◽  
Pore Domain

Recent progress in understanding the plant NE (nuclear envelope) has resulted from significant advances in identifying and characterizing the protein constituents of the membranes and nuclear pores. Here, we review recent findings on the membrane integral and membrane-associated proteins of the key domains of the NE, the pore domain and inner and outer NEs, together with information on protein targeting and NE function.

Further observations on nucleolar tails in amphibian oocytes

1991 ◽  
Vol 99 (3) ◽  
pp. 515-521
Author(s):  
PEDRO LEÓN ◽  
JAMES KEZER ◽  
ERIC SCHABTACH
Keyword(s):  
Electron Microscopy ◽  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Outer Surface ◽  
Light And Electron Microscopy ◽  
Nuclear Pores ◽  
Core Component ◽  
Amphibian Species ◽  
Attachment Structures ◽  
Convoluted Tubules

Large oocytes from some amphibian species possess beaded or unbeaded intranuclear tails that penetrate the extrachromosomal nucleoli through a distinct pit in their surface and attach to the central core component Here we show, using light and electron microscopy, that tails anchor nucleoli to the nuclear envelope through intricate attachment structures. These structures are composed of interconnected spherical masses containing highly convoluted tubules and associated extratubular proteins, directly directly in contact with the inner nuclear membrane. Fibers emerging from the nuclear pores seemingly hold the attachment complex in place. Beads on the nucleolar tails are formed by the accumulation of proteins on the outer surface of smooth tubules. The function of these intranuclear tubules is unknown

Sequential degradation of proteins from the nuclear envelope during apoptosis

2001 ◽  
Vol 114 (20) ◽  
pp. 3643-3653 ◽  
Author(s):  
Madeleine Kihlmark ◽  
Gabriela Imreh ◽  
Einar Hallberg
Keyword(s):  
Nuclear Envelope ◽  
Apoptotic Cell ◽  
Nuclear Periphery ◽  
Condensed Chromatin ◽  
Nuclear Pore ◽  
Dependent Manner ◽  
Nuclear Pores ◽  
Double Labeling ◽  
Lamin B ◽  
Nuclear Apoptosis

We have produced new antibodies specific for the integral pore membrane protein POM121. Using these antibodies we show that during apoptosis POM121 becomes proteolytically degraded in a caspase-dependent manner. The POM121 antibodies and antibodies specific for other proteins of the nuclear envelope were used in a comparative study of nuclear apoptosis in staurosporine-treated buffalo rat liver cells. Nuclei from these cells were classified in three different stages of apoptotic progression: stage I, moderately condensed chromatin surrounded by a smooth nuclear periphery; stage II, compact patches of condensed chromatin collapsing against a smooth nuclear periphery; stage III, round compact chromatin bodies surrounded by grape-shaped nuclear periphery. We have performed double labeling immunofluorescence microscopy of individual apoptotic cells and quantitative immunoblotting analysis of total proteins from apoptotic cell cultures. The results showed that degradation of nuclear envelope marker proteins occurred in a specific order. POM121 degradation occurred surprisingly early and was initiated before nucleosomal DNA degradation could be detected using TUNEL assay and completed before clustering of the nuclear pores. POM121 was eliminated significantly more rapid compared with NUP153 (a peripheral protein located in the nucleoplasmic basket of the nuclear pore complex) and lamin B (a component of the nuclear lamina). Disappearance of NUP153 and lamin B was coincident with onset of DNA fragmentation and clustering of nuclear pores. By contrast, the peripheral NPC protein p62 was degraded much later. The results suggest that degradation of POM121 may be an important early step in propagation of nuclear apoptosis.

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