scholarly journals Das endoplasmatische Retikulum in der Mitose — ein wandelbares Netz

BIOspektrum ◽  
2020 ◽  
Vol 26 (7) ◽  
pp. 739-742
Author(s):  
Anne Schlaitz
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Division ◽  
Nuclear Envelope ◽  
Molecular Mechanisms ◽  
Detailed Understanding ◽  
Membrane Bound

AbstractIn order to divide successfully, cells need to reorganize their interior including membrane-bound organelles such as the endoplasmic reticulum (ER). The ER serves as sink and source for the nuclear envelope and undergoes distinct transformations in its morphology and dynamics during cell division. To fully appreciate the functions of ER remodeling during cell division it will be essential to first achieve a detailed understanding of the underlying molecular mechanisms.

scholarly journals Properties of membrane-bound bilirubin UDP-glucuronyltransferase in rough and smooth endoplasmic reticulum and in the nuclear envelope from rat liver

1989 ◽  
Vol 259 (3) ◽  
pp. 659-663 ◽  
Author(s):  
F Vanstapel ◽  
L Hammaker ◽  
K Pua ◽  
N Blanckaert
Keyword(s):  
Endoplasmic Reticulum ◽  
Nuclear Envelope ◽  
Rat Liver ◽  
Smooth Endoplasmic Reticulum ◽  
Membrane System ◽  
Permeability Barrier ◽  
Membrane Bound ◽  
Marker Studies ◽  
High Degree ◽  
Regulatory Properties

We examined regulatory properties of bilirubin UDP-glucuronyltransferase in sealed RER (rough endoplasmic reticulum)- and SER (smooth endoplasmic reticulum)-enriched microsomes (microsomal fractions), as well as in nuclear envelope from rat liver. Purity of membrane fractions was verified by electron microscopy and marker studies. Intactness of RER and SER vesicles was ascertained by a high degree of latency of the lumenal marker mannose-6-phosphatase. No major differences in the stimulation of UDP-glucuronyltransferase by detergent or by the presumed physiological activator, UDPGlcNAc, were observed between total microsomes and RER- or SER-enriched microsomes. Isolated nuclear envelopes were present as a partially disrupted membrane system, with approx. 50% loss of mannose-6-phosphatase latency. The nuclear transferase had lost its latency to a similar extent, and the enzyme failed to respond to UDPGlcNAc. Our results underscore the necessity to include data on the integrity of the membrane permeability barrier when reporting regulatory properties of UDP-glucuronyltransferase in different membrane preparations.

scholarly journals Nuclear Envelope Proteins Modulating the Heterochromatin Formation and Functions in Fission Yeast

Cells ◽  
2020 ◽  
Vol 9 (8) ◽  
pp. 1908 ◽  
Author(s):  
Yasuhiro Hirano ◽  
Haruhiko Asakawa ◽  
Takeshi Sakuno ◽  
Tokuko Haraguchi ◽  
Yasushi Hiraoka
Keyword(s):  
Endoplasmic Reticulum ◽  
Nuclear Envelope ◽  
Fission Yeast ◽  
Histone Deacetylase ◽  
Nuclear Pore Complex ◽  
Molecular Mechanisms ◽  
Nuclear Pore ◽  
Double Membrane ◽  
Heterochromatin Formation ◽  
Nuclear Membranes

The nuclear envelope (NE) consists of the inner and outer nuclear membranes (INM and ONM), and the nuclear pore complex (NPC), which penetrates the double membrane. ONM continues with the endoplasmic reticulum (ER). INM and NPC can interact with chromatin to regulate the genetic activities of the chromosome. Studies in the fission yeast Schizosaccharomyces pombe have contributed to understanding the molecular mechanisms underlying heterochromatin formation by the RNAi-mediated and histone deacetylase machineries. Recent studies have demonstrated that NE proteins modulate heterochromatin formation and functions through interactions with heterochromatic regions, including the pericentromeric and the sub-telomeric regions. In this review, we first introduce the molecular mechanisms underlying the heterochromatin formation and functions in fission yeast, and then summarize the NE proteins that play a role in anchoring heterochromatic regions and in modulating heterochromatin formation and functions, highlighting roles for a conserved INM protein, Lem2.

scholarly journals Peptide–Oleate Complexes Create Novel Membrane-Bound Compartments

2020 ◽  
Vol 37 (11) ◽  
pp. 3083-3093
Author(s):  
Jesper S Hansen ◽  
Tuan Hiep Tran ◽  
Michele Cavalera ◽  
Sanchari Paul ◽  
Arunima Chaudhuri ◽  
...  
Keyword(s):  
Oleic Acid ◽  
Cell Division ◽  
Molecular Mechanisms ◽  
Molecular Model ◽  
Lipid Vesicle ◽  
Helical Peptides ◽  
Membrane Bound ◽  
Molecular Information ◽  
Challenging Question ◽  
Alpha Helical Peptides

Abstract A challenging question in evolutionary theory is the origin of cell division and plausible molecular mechanisms involved. Here, we made the surprising observation that complexes formed by short alpha-helical peptides and oleic acid can create multiple membrane-enclosed spaces from a single lipid vesicle. The findings suggest that such complexes may contain the molecular information necessary to initiate and sustain this process. Based on these observations, we propose a new molecular model to understand protocell division.

scholarly journals Cisternal Organization of the Endoplasmic Reticulum during Mitosis

2009 ◽  
Vol 20 (15) ◽  
pp. 3471-3480 ◽  
Author(s):  
Lei Lu ◽  
Mark S. Ladinsky ◽  
Tom Kirchhausen
Keyword(s):  
Endoplasmic Reticulum ◽  
Nuclear Envelope ◽  
Mammalian Cells ◽  
Three Dimensional ◽  
Freeze Substitution ◽  
High Resolution Electron Microscopy ◽  
Animal Cells ◽  
Resolution Electron ◽  
Major Transformation ◽  
Membrane Bound

The endoplasmic reticulum (ER) of animal cells is a single, dynamic, and continuous membrane network of interconnected cisternae and tubules spread out throughout the cytosol in direct contact with the nuclear envelope. During mitosis, the nuclear envelope undergoes a major rearrangement, as it rapidly partitions its membrane-bound contents into the ER. It is therefore of great interest to determine whether any major transformation in the architecture of the ER also occurs during cell division. We present structural evidence, from rapid, live-cell, three-dimensional imaging with confirmation from high-resolution electron microscopy tomography of samples preserved by high-pressure freezing and freeze substitution, unambiguously showing that from prometaphase to telophase of mammalian cells, most of the ER is organized as extended cisternae, with a very small fraction remaining organized as tubules. In contrast, during interphase, the ER displays the familiar reticular network of convolved cisternae linked to tubules.

scholarly journals Endoplasmic reticulum remains continuous and undergoes sheet-to-tubule transformation during cell division in mammalian cells

2007 ◽  
Vol 179 (5) ◽  
pp. 895-909 ◽  
Author(s):  
Maija Puhka ◽  
Helena Vihinen ◽  
Merja Joensuu ◽  
Eija Jokitalo
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Division ◽  
3D Modeling ◽  
Mammalian Cells ◽  
Structural Changes ◽  
Electron Tomography ◽  
Morphological Changes ◽  
Homogenous Distribution ◽  
Membrane Bound ◽  
Cycle Dependent

The endoplasmic reticulum (ER) is a multifaceted cellular organelle both structurally and functionally, and its cell cycle–dependent morphological changes are poorly understood. Our quantitative confocal and EM analyses show that the ER undergoes dramatic reorganization during cell division in cultured mammalian cells as mitotic ER profiles become shorter and more branched. 3D modeling by electron tomography reveals that the abundant interphase structures, sheets, are lost and subsequently transform into a branched tubular network that remains continuous. This is confirmed by observing the most prominent ER subdomain, the nuclear envelope (NE). A NE marker protein spreads to the mitotic ER tubules, although it does not show a homogenous distribution within the network. We mimicked the mitotic ER reorganization using puromycin to strip the membrane-bound ribosomes from the interphase ER corresponding to the observed loss of ribosomes normally occurring during mitosis. We propose that the structural changes in mitotic ER are linked to ribosomal action on the ER membranes.

The ultrastructure of the zoospore of Hyphochytrium catenoides

1985 ◽  
Vol 63 (3) ◽  
pp. 497-505 ◽  
Author(s):  
Elizabeth W. Cooney ◽  
Donald J. S. Barr ◽  
William E. Barstow
Keyword(s):  
Endoplasmic Reticulum ◽  
Nuclear Envelope ◽  
Transition Zone ◽  
Multivesicular Bodies ◽  
Dense Matrix ◽  
Flagellar Membrane ◽  
Membrane Bound

The ultrastructure of the zoospore of Hyphochytrium catenoides Karling is described. The zoospore has a single, anterior, tinsel flagellum. The nucleus is elongate and convoluted with an indentation at the anterior end in which the Golgi cisternae are located. There are large lipid globules in the posterior end of the cell. The ribosomes are loosely enclosed by endoplasmic reticulum, the nuclear envelope, and mitochondria. The mitochondria have tubular cristae in a dense matrix. Microbodies are found appressed to the nuclear envelope and also free in the ribosomal region. Endoplasmic reticulum sheets traverse the ribosome region. The vesiculate cytoplasm has several distinct types of membrane-bound inclusions: (i) multivesicular bodies, (ii) vesicles containing presumptive mastigonemes, (iii) vesicles having an electron-dense cortex with an electron-transparent center, and (iv) electron-opaque vesicles whose contents seem condensed and only partially fill the vesicles. The transition zone from the flagellum to the kinetosome has three segments: a distal set of struts extending from the axonemal doublets into the axoneme core, a midsection of electron-opaque rings, and a distinctive "disclike" terminal plate with a thickened portion between the doublets and the flagellar membrane. The three-part rootlet system has (i) a "ribbed" pair of microtubules on one side of the kinetosome, (ii) a curved "ribbed," single microtubule with electron-opaque backing which originates near the nonfunctional centriole, and (iii) a straight doublet of microtubules without ribs extending from the nonfunctional centriole posteriorly to the midregion of the zoospore.

The BiP protein and the endoplasmic reticulum of Schizosaccharomyces pombe: fate of the nuclear envelope during cell division

1993 ◽  
Vol 105 (4) ◽  
pp. 1115-1120 ◽  
Author(s):  
A.L. Pidoux ◽  
J. Armstrong
Keyword(s):  
Cell Cycle ◽  
Molecular Weight ◽  
Endoplasmic Reticulum ◽  
Cell Division ◽  
Nuclear Envelope ◽  
Schizosaccharomyces Pombe ◽  
Polyclonal Antibody ◽  
Elevated Temperatures ◽  
Kluyveromyces Lactis ◽  
Similar Molecular Weight

A polyclonal antibody was raised to the C-terminal region of fission yeast BiP. The use of this antibody for immunoprecipitation, western blotting and immunofluorescence has confirmed and extended the observations made previously with an epitope-tagged BiP molecule. A fraction of BiP protein is glycosylated in Schizosaccharomyces pombe cells. Pulse-chase experiments showed that this modification occurs rapidly upon synthesis and that the extent of glycosylation does not then change with time. BiP protein is induced by elevated temperatures and by treatment with tunicamycin. The antibody cross-reacts with proteins of similar molecular weight in the yeasts Kluyveromyces lactis and Schizosaccharomyces japonicus. Immunofluorescence of BiP has been used to follow the behaviour of the ER and in particular the nuclear envelope through the cell cycle.

Endoplasmic reticulum proteins in cardiac development and dysfunction

2009 ◽  
Vol 87 (6) ◽  
pp. 419-425 ◽  
Author(s):  
Daniel Prins ◽  
Marek Michalak
Keyword(s):  
Endoplasmic Reticulum ◽  
Molecular Mechanisms ◽  
Cardiac Development ◽  
Heart Function ◽  
Heart Diseases ◽  
Secretory Proteins ◽  
Hypoxic Conditions ◽  
Catalytic Role ◽  
Membrane Bound ◽  
And Function

An understanding of cardiac pathologies and the molecular mechanisms thereof is essential for the development of therapies for cardiovascular disease, a common cause of death in Western societies. Investigations into heart diseases have shown that the endoplasmic reticulum and its diverse functions may lie at the center of many cardiac pathologies. Animal models have demonstrated that in numerous cases, faulty endoplasmic reticulum activity is manifested in defective cardiogenesis or impaired heart function. These findings suggest that the endoplasmic and sarcoplasmic reticulum membranes may represent functionally independent organelles responsible for specialized functions in the heart. This review addresses the molecular pathways linking endoplasmic reticulum function and malfunction with impaired cardiac phenotypes. The endoplasmic reticulum affects cardiac development and function through Ca2+-dependent pathways, its catalytic role in the proper folding and targeting of membrane-bound and secretory proteins, and its response to cellular stress events, particularly hypoxic conditions. These pathways present potential novel targets for treatment of cardiac disease.

The Ultrastructure of the Nuclear Events of Binary Fission in Paramecium bursaria and the Effects of Colchicine on Cell Division

1974 ◽  
Vol 32 ◽  
pp. 276-277
Author(s):  
L. M. Lewis
Keyword(s):  
Cell Division ◽  
Nuclear Envelope ◽  
Condensed Chromatin ◽  
Binary Fission ◽  
Paramecium Bursaria ◽  
Nuclear Events ◽  
Division Axis

The effects of colchicine on extranuclear microtubules associated with the macronucleus of Paramecium bursaria were studied to determine the possible role that these microtubules play in controlling the shape of the macronucleus. In the course of this study, the ultrastructure of the nuclear events of binary fission in control cells was also studied.During interphase in control cells, the micronucleus contains randomly distributed clumps of condensed chromatin and microtubular fragments. Throughout mitosis the nuclear envelope remains intact. During micronuclear prophase, cup-shaped microfilamentous structures appear that are filled with condensing chromatin. Microtubules are also present and are parallel to the division axis.

Compound Symbiosis in Peridinium Balticum

1973 ◽  
Vol 31 ◽  
pp. 500-501
Author(s):  
R. N. Tomas
Keyword(s):  
Endoplasmic Reticulum ◽  
Nuclear Envelope ◽  
The Other ◽  
Exact Nature ◽  
Symbiotic Relationship

Peridinium balticum appears to be unusual among the dinoflagellates in that it possesses two DNA-containing structures as determined by histochemical techniques. Ultrastructurally, the two dissimilar nuclei are contained within different protoplasts; one of the nuclei is characteristically dinophycean in nature, while the other is characteristically eucaryotic. The chloroplasts observed within P. balticum are intrinsic to an eucaryotic photosynthetic endosymbiont and not to the dinoflagellate. These organelles are surrounded by outpocketings of endoplasmic reticulum which are continuous with the eucaryotic nuclear envelope and are characterized by thylakoids composed of three apposed lamellae. Girdle lamellae and membranebounded interlamellar pyrenoids are also present. Only the plasmalemma of the endosymbiont segregates its protoplast from that of the dinophycean cytoplasm. The exact nature of this symbiotic relationship is at present not known.

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