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At least 937 records · Page 52Linked to original sources
PubMed1992

The molecular architecture of an insect midgut brush border cytoskeleton.

The cytoskeletal apparatus of the vertebrate intestinal brush border (BB) has served as a model system for the actin-based cytoskeleton of nonmuscle cells. In this study, we examine the structural organization and molecular architecture of the BB cytoskeleton expressed in the midgut of lepidopteran larvae, Manduca sexta. Electron microscopy of the midgut of the 5th instar larvae revealed enterocytes with an apical BB surface comparable to that in the vertebrate intestine, with both microvillar (MV) and terminal web (TW) domains, the latter defined by a zone of organelle exclusion directly beneath the MV. As reported previously for the larval dragon fly, the MV contain a bundle of actin filaments, as determined by staining with rhodamine phalloidin (Kukulies, J., et al., Protoplasma 121, 157-162 (1984)) and heavy meromyosin decoration (Komnick, H., J. Kukulies, Zoomorphology 107, 241-253 (1987)). Two-dimensional gel analysis revealed the presence of multiple isoelectric variants of actin with the major isoform corresponding to the non-muscle actin isoform II, expressed in Drosophila. Like the vertebrate BB, the Manduca BB can be isolated intact from enterocytes by mechanical shear. Immunochemical analysis of isolated BB fractions or whole homogenates of midgut revealed proteins of appropriate molecular weight immunoreactive with antibodies to the MV core proteins: BB myosin I, villin and fimbrin, and the TW components: spectrin, myosin II and tropomyosin. Immunocytochemical localization of a subset of these proteins at the light microscopic (spectrin) and electron microscopic (actin, villin, spectrin, myosin II, and tropomyosin) level reveals that the molecular architecture of the Manduca BB cytoskeleton is homologous to that found in vertebrates.

Animals↗
PubMed1992

[Effects of McAbs HIP2, APT4 and HI117 on the human platelet cytoskeleton].

The effects of monoclonal antibodies HIP2, APT4 and HI117 on the platelet cytoskeleton were investigated. The results showed that HIP2, APT4 and HI117 could induce an increase of platelet cytoskeleton materials in PRP. The action of HIP2 and APT4 could be obviously inhibited by the calmodulin inhibitor EBB. The inhibition rates of EBB were 76.3% and 48.95%, respectively. But EBB couldn't inhibit the HI117-induced an increase of platelet cytoskeleton materials. EBB could completely inhibit APT4-induced platelet aggregation(100%) and partially inhibit HIP2-induced platelet aggregation (14.26%). It couldn't inhibit HI117-induced platelet aggregation. These McAbs couldn't induce aggregation and actin mobilization in washed platelets in the presence of EDTA. The results indicate that platelet aggregation and the increase of actin induced by these McAbs, in addition to Ca2+, could be related to a factor or factors in the plasma. The Ca(2+)-CM system might play an important role in platelet aggregation and actin mobilization induced by HIP2 and APT4.

Actins↗
PubMed2004

[Antioxidants-induced rearrangements of actin cytoskeleton in 3T3 and 3T3-SV40 fibroblasts].

Effect of antioxidants on actin cytoskeleton in 3T3 fibroblasts and 3T3 fibroblasts transformed with SV40 virus (3T3-SV40 cells) was studied. Antioxidants used were as follows: N-acetyl-L-cysteine (NAC), (-)-2-oxo-4-thiazolidine-carboxylic acid (OTZ), and glutathione in the reduced form (GSH). Both NAC and OTZ are precursors of GSH in the cell, but, in contrast to NAC, OTZ reduces inside the cell forming L-cysteine. The presence of NAC (5-20 mM) in the culture medium of both cell types resulted in loosening of monolayer, fragmentation of stress fibers, and the appearance of amorphous actin structures. As 3T3-SV40 cells contain less actin stress fibers than 3T3 cells, the NAC-induced rearrangements of actin cytoskeleton were stronger in these cells than in 3T3 cells. In contrast to NAC, OTZ (10-20 mM) did not destroy monolayer and did not induce any visible disappearance of stress fibers either in 3T3 or 3T3-SV40 cells. However, in the presence of OTZ, amorphous actin-containing structures were observed in 3T3-SV40 cells. The effect of glutathione on both cell types was similar to that of NAC. The time required for GSH-induced alterations of actin cytoskeleton (about 5 h) was consistent with the increase in the intracellular level of reactive oxygen species (4 h after addition of GSH to the culture medium). Upon removal of the antioxidants from the medium, actin filament structures were reconstructed. However, within 24 h after withdrawal of NAC or GSH, only a partial reconstruction of stress fibers was observed in 3T3 cells. On the contrary, 3T3-SV40 cells demonstrated formation of well-structured actin fibers similar to normal fibroblasts. These results suggest that GSH can act as a pro-oxidant in the absence of oxidative stress.

3T3 Cells↗
PubMed2005

Interaction of cadherin with the actin cytoskeleton.

Cadherins regulate cell-cell adhesion throughout embryonic development and in the adult organism, and defects in cadherin expression and function are characteristic of many disease states including cancer. Although extracellular binding between cadherins specifies adhesion between cells, the strength of the interaction is thought to be regulated by cadherin clustering through reorganization of the actin cytoskeleton. Protein-protein interactions have been described that could link cadherins either directly or indirectly to the actin cytoskeleton. Here, we describe these protein interactions, and examine critically the evidence that they link cadherins to the actin cytoskeleton.

Actins↗
PubMed2005

[Diffusional attenuation of proton echo and control of changes in the cytoskeleton hydration level].

Using the pulsed NMR-method with pulse gradient of the magnetic field, a study was made of changes in diffusional attenuation (DA) of proton echo in germs of triticum grains under the influence of agents depolymerizing cytoskeleton elements or inhibiting their ATP-activity. At a short diffusion time, we observed respective alterations of NMR-population in a fraction of cell water molecules contributing to DA at large values of pulse gradient. It is shown that the presence in DA of a site with essentially smaller coefficient of self-diffusion, as compared with basic cell water fraction, is not a consequence of restricted diffusion phenomenon. The observed changes in NMR-population of the appropriate fraction of cell water molecules are interpreted as changes in the level of cytoskeleton hydratation occurring under the influence of the used agents. A hypothesis is proposed for the functional role of similar changes in the level of hydratation of cytoskeleton elements located inside plamodesmata in the mechanism of plasmodesmatal water permeability regulation.

Cytoskeleton↗
PubMed2006

[Dynamics of microtubular cytoskeleton in higher plant meiosis. VII. Mechanisms of the simultaneous cytokinesis].

Rearrangements of microtubular cytoskeleton during telophase in pollen mother cells of some dicotyledon plants with the simultaneous cytokinesis during normal and abnormal meiosis were studied. At telophase I, a potentially functional phragmoplast forms between daughter nuclei, but no cell plate is present. During interkinesis, the phragmoplast plays the role of an interphase cytoskeleton array. Dynamics of microtubule reorganization in polar regions of the telophase spindle is discussed in addition to the role played by microtubule convergence centers in cytoskeleton rearrangements during meiosis.

Cytokinesis↗
PubMed1991

The Alzheimer amyloid precursor is associated with the detergent-insoluble cytoskeleton.

The amyloid beta-protein (A beta P), the main component of neuritic plaques in Alzheimer's disease (AD), is derived by unknown mechanisms from a family of amyloid precursor proteins (APPs). Using a detergent extraction procedure, we have found that in brain and in neural cell lines, 50-90% of APP is bound to detergent-insoluble cytoskeleton. Labeling experiments performed in a C6 glioma cell line indicated that both cell surface and intracellular APPs are associated with the cytoskeleton. This association requires intact microtubules and is modulated by protein phosphorylation and by cell density. These findings suggest that the function of cellular APP, presently unknown, involves the cytoskeleton and particularly microtubules. The dynamic nature of the binding and its dependence on microtubules and protein phosphorylation suggest it as a possible target in AD, where abnormal cytoskeletal structures and protein phosphorylation have been reported. Altered cytoskeletal binding of APP might lead to its aberrant proteolysis and generation of the A beta P.

Alzheimer Disease↗
PubMed2006

[Dynamics of microtubular cytoskeleton in higher plant meiosis. X. General scheme of cytoskeletal cycle].

An overview of a set of our previous papers titled "Dynamics of microtubular cytoskeleton in higher plant meiosis" is presented, in addition to some data on subcellular mechanisms underlying cytoskeleton reorganization during meiotic division in pollen mother cells. An illustrated scheme of cytoskeleton rearrangements during plant meiosis, both with successive and simultaneous cytokinesis, is given.

Chimera↗
PubMed1990

Role of cytoskeleton in canalicular contraction in cultured differentiated hepatocytes.

We and others have published data that indicate that the role played by microtubules and microfilaments in biliary secretion is as follows: microtubules play a part in secretion and microfilaments play a part in the canalicular contraction. To further study the role of the cytoskeleton in canalicular contraction, we observed the contraction of bile canaliculi (BC) induced by vasopressin (VP) in cultured differentiated hepatocytes treated with several agents that selectively rearrange the cytoskeleton. The hepatocytes obtained from 14-day-old rats were cultured for 48 hours. The BC formed between the cells were dilated and closely sealed by junctional complexes. Ruthenium red stain showed that the junctional complexes of the BC were tightly sealed. Cytoskeletal changes were observed by double-labeled fluorescence microscopy. A spontaneous contraction of the BC was rarely seen during a 60-minute observation period in controls. When the hepatocytes were incubated with VP (10(-8) M), the canalicular contraction began at 30 minutes, gradually progressed, and was complete by 60 minutes. The contraction was reversed after 60 minutes of incubation in VP-free medium. In cytochalasin B-treated hepatocytes, actin appeared to form pools around the dilated BC, and the canalicular contraction after VP was rarely observed. In colchicine-treated hepatocytes, the microtubules were depolymerized. Although the BC appeared unaffected by colchicine alone, the canalicular contraction induced by VP was markedly decreased. beta-lumicolchicine had no effect on the cytoskeleton or on the canalicular contraction. Mg2(+)-ATPase histochemistry revealed that the BC that did not contract after VP contained little Mg2(+)-ATPase reaction product. When the BC contracted, diverticula came off to form diacytotic vesicles, as indicated by the presence of the BC marker enzyme reaction product within the vesicles. Colchicine treatment blocked the diacytotic process. This prevented the contraction stimulated by VP, because all of the routes of escape of the canalicular contents were blocked off, including diacytosis. In conclusion, the integrity of actin filaments and Mg2(+)-ATPase is necessary for VP-induced contraction, and the integrity of microtubules is essential for regurgitation of BC content (diacytosis).

Adenosine Triphosphatases↗
PubMed2006

[The role of SM22 alpha in cytoskeleton organization and vascular remodeling].

Phenotypic modulation of vascular smooth muscle cells (VSMCs) plays a key role in vascular remodeling diseases, such as atherosclerosis, hypertension and restenosis. Recent researches have focused on the expression regulation of VSMC-specific marker genes and cytoskeleton organization in association with phenotypic modulation of VSMCs. Smooth muscle 22 alpha (SM22 alpha) is a novel differentiated VSMC marker, which is characterized by its smooth muscle tissue-specific and VSMC phenotype-specific expression pattern, and serves as an actin-association protein to participate in VSMC cytoskeleton organization and vascular remodeling. This article reviews recent advances in the characterization of SM22 alpha structure and its mechanism in VSMC cytoskeleton organization and vascular remodeling.

Cells, Cultured↗
PubMed2006

[Listeria-induced host cellular actin cytoskeleton rearrangement and phospholipase D].

Either phagocytosis of macrophage to pathogen or pathogen-induced invasion into non-professional phagocytes, such as epithelial cells, require actin cytoskeletal rearrangements and remodeling of the plasma membrane, which are regulated precisely by monogeric GTPase and the correlated proteins. As a key signaling molecule in the cell, phosphotidicphospholipase D (PLD) regulates or interacts directly with cellular actin cytoskeleton rearrangement. Phospholipase D plays an important role in FcgammaRI and C-reactive protein-mediated phagocytosis and phosphorylated cofilin, a ADF (actin depolymerizing factor) is able to bind to phospholipase D and stimulate it; meanwhile, the Listeria-induced actin cytoskeleton rearrangement during the infection is controlled by the phosphorylation of cofilin. Thus, it made challenge to disclose the function of PLD on the regulation of Listeria-induced actin cytoskeleton rearrangement during infection, furthermore, it may provide us more understanding on the role of PLD in the infection and inflammation, which is essential to dissect the molecular mechanism of bacterial-host interaction more thoroughly.

Actins↗
PubMed1991

Polar axis fixation in Fucus zygotes: components of the cytoskeleton and extracellular matrix.

Polar axis formation and polar axis stabilization (or fixation) can be separated and analyzed in synchronously developing zygotes of the brown alga Fucus. Extensive experimental evidence points to a role for both the cytoskeleton and the extracellular matrix (ECM) in the process of axis fixation in Fucus. A structural complex composed of the cytoskeleton and the ECM has been postulated to stabilize membrane asymmetries generated as a result of axis-forming vectors. This axis stabilizing complex (ASC) may take the form of transmembrane connections between the cytoskeleton on the cytoplasmic face and the ECM on the external side of the plasma membrane, similar to focal contacts in animal cells. At present we know of two components in the proposed ASC of Fucus: an adhesive sulfated glycoprotein which is localized in the ECM, and an actin network which is localized on the adjoining cytoplasmic face. This preliminary report describes evidence for the presence of molecules in two-celled Fucus embryos that are similar to those found in focal contacts in animal cells, i.e. vinculin, integrin and vitronectin. However, their localization and interaction with each other relative to the polar axis has yet to be determined. These initial observations will provide the basis to pursue further an analysis of these components in the process of polar axis fixation.

Cell Polarity↗
PubMed1991

Isolation and characterization of protein kinase C from rat brain synaptosome cytoskeleton.

Synaptosomes prepared from brain tissues are known to retain morphological and functional characteristics of the nerve ending. Little information is available, however, as to the biochemical events underlying synaptogenesis and transmitter release. Increasing body of evidence suggests that protein kinase C (PKC) plays crucially important roles through phosphorylation of membrane proteins such as GAP-43 (for 43-kDa growth-associated protein) and 87-kDa MARCKS (for myristoylated, alanine-rich C kinase substrate) in many aspects of the neuronal function. Among them, arrangement of membrane cytoskeletal protein is proposed to be one of the primary sites of PKC action. The present study is an attempt to isolate and characterize PKC associated with synaptosomal membrane cytoskeleton. Rat brain synaptosomal Triton X-100 insoluble elements (cytoskeleton) contains specific [3H]phorbol dibutyrate binding activity and 78-kDa protein which reacts with an antibody against beta II-PKC subspecies. Although 78-kDa protein could not be solublized by the treatment with various ionic and non-ionic detergents and/or high concentrations of salts such as NaCl and LiBr, the fragment of 78-kDa protein was produced and solublized from cytoskeleton by limited proteolysis with calpain II, which cleaves PKC at one or two specific sites of the enzyme to produce catalytic and regulatory fragments. The solubilized 46-kDa fragment was identical with the catalytic fragment of beta II-PKC. The results indicate that this PKC subspecies is tightly associated with the cytoskeletal network of synaptic membranes.

Amino Acid Sequence↗
PubMed1991

The spatial organization of the cytoskeleton in crayfish stretch receptor.

An electron microscopic study of the cytoskeleton of the crayfish stretch receptor was carried out. Longitudinal sections of the sensory neuron axons and dendrites showed wave-like arrays of microtubules with a period of about 5 microns. Transverse sections showed that the microtubules displayed no regularity in the arrays. In oblique sections, transverse and longitudinal views of microtubules (or shorter and longer segments of microtubules) alternated yielding a festoon-like pattern. The data obtained indicate that the cytoskeleton of the stretch receptor has a helical structure in which all the microtubules, the major cytoskeletal components, are arranged in parallel helices that are in register along the length of axons and dendrites. The helical organization of the cytoskeleton is probably responsible for the banded appearance of sensory axons and primary dendrites as seen in the polarized light. Decrease of contrast and disappearance of the banding during stretch of the receptor muscle are supposedly due to the desynchronization of the helical trajectories of the microtubules and to the decrease of the helical amplitude.

Animals↗
PubMed1991

[The cytoskeleton of the Mauthner neurons in the guppy after returning from an orbital flight].

The ultrastructural investigations of the Mauthner neurons (M-cells) of P. reticulata were performed on the return of the fishes after a two weeks orbital flight, the M-cells of fishes from different control groups being simultaneously examined. The structure of M-cells from the experimental fishes was shown to be severely damaged. The changes involved the synaptic apparatus, postsynaptic areas, mitochondria and other organelles of the cytoplasm and the nucleus. Particular changes were seen in the neuronal cytoskeleton. While in the M-cells of intact fishes these were seen as evenly distributed microfilaments and neurofilaments, in the M-cells of experimental fishes the cytoskeleton looked as alternating bundles of condensed filaments. The first indications of cytoskeleton damage appeared in M-cells of the guppy from transport control group and strengthened in fishes from the group of synchronous control. Thus, the data obtained give us a possibility to suggest that the return on the Earth and following readaptation after a prolonged flight at conditions of microgravity and consequent disfunction of vestibular apparatus may result in the damage of central neurons receiving vestibular afferentation (such as M-cells). That, in turn, may be a cause of functional disorders of the central nervous system, including the nerve centres maintaining the organs of motion. These facts are necessary to take into consideration when more prolonged cosmic flights are planned.

Animals↗
PubMed1991

Modulation of pulmonary permeability in vivo with agents that affect the cytoskeleton.

In vitro studies show that the cytoskeleton of the microvascular barrier moderates polymorphonuclear leukocyte (PMN) diapedesis and the transport of macromolecules. This in vivo study tests indirectly whether the cytoskeleton of the pulmonary microvasculature responds similarly to agents known to reorganize the cytoskeleton to alter diapedesis and permeability in vitro. One of four agents, saline solution, cytochalasin B (which promotes actin microfilament disassembly), leukotriene (LT) B4 (PMN chemoattractant), or phalloidin (which promotes and stabilizes F-actin polymerization) was introduced into the bronchus of the anterior segment of the left lung of anesthetized rats (n = 152) through a tracheostomy and fine-bore cannula. Twenty minutes later, saline solution, cytochalasin B, LTB4, or phalloidin was similarly introduced. PMN accumulations (x 10(4) cells/ml), protein concentration in bronchoalveolar lavage fluid, and lung wet/dry weight ratios were measured 3 hours later. When the initial and secondary treatments were saline solution, PMN accumulations were 3 +/- 1 cells/ml and the protein level was 274 +/- 48 micrograms/ml. Secondary treatment of the saline-treated group with cytochalasin B or LTB4 led to increases in PMN to 18 +/- 2 and 9 +/- 2 cells/ml and protein to 960 +/- 50 and 840 +/- 40 micrograms/ml (p less than 0.05); secondary treatment with phalloidin was similar to that with saline solution. With saline solution used for both treatments, the wet/dry ratio was 3.4 +/- 0.2. Primary saline solution and secondary treatments with either cytochalasin B or LTB4 led to a similar increase in wet/dry ratios to 3.9 +/- 0.1 (p less than 0.05), whereas phalloidin was without effect (3.5 +/- 0.3). Initial cytochalasin B treatment followed by LTB4 led to increased PMN diapedesis (43 +/- 6 cells/ml and wet/dry ratio 4.3 +/- 0.2) (p less than 0.05). Secondary phalloidin treatment attenuated the cytochalasin B effect with counts of 12 +/- 2 PMN/ml, protein levels of 460 +/- 30 micrograms/ml, and a lower wet/dry ratio of 3.7 +/- 0.1 (p less than 0.05). Even more striking, phalloidin as initial treatment further reduced the cytochalasin B effect to 7 +/- 1 PMN/ml, whereas protein level was 490 +/- 60 micrograms/ml and wet/dry ratio was 3.5 +/- 0.1 (p less than 0.05). Further, phalloidin, given initially, attenuated the effect of secondary treatment with LTB4, resulting in fewer cells (4 +/- 2 PMN/ml), a lower wet/dry ratio (3.4 +/- 0.1), and protein level of 650 +/- 20 micrograms/ml (p less than 0.05).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Patterning of the membrane cytoskeleton by the extracellular matrix.

The extracellular matrices of different tissues contain components which affect the migration, morphology and differentiation of many types of cells. These forms of cell behavior often involve dramatic changes in cytoskeletal organization. Extracellular matrix components are recognized by specific cell surface receptors which span the membrane and interact with the actin cytoskeleton. In cultured cells, the matrix receptors are concentrated in sites of cell attachment called focal adhesions. Information that is conveyed from the extracellular matrix to the cytoskeleton may involve matrix components, cell surface receptors, as well as the proteins at the cytoplasmic face of the focal adhesion which link the receptors to the actin cytoskeleton.

Actins↗
PubMed1990

Zinc induces specific association of PKC with membrane cytoskeleton.

Putative binding sites for zinc are present in the regulatory domain of protein kinase C but a distinct role for zinc has not yet been proposed. Here we show that micromolar concentrations of zinc chloride cause pure rat brain protein kinase C to localize in a detergent-insoluble, cytoskeletal fraction of red cell membranes and to bind to isolated cytoskeleton in the presence of phosphatidylserine. Attachment of protein kinase C to cytoskeleton was accompanied by enhanced expression of binding sites for 3H-phorbol ester, a regulatory ligand of protein kinase C. The active factor in the cytoskeleton was labile to protease suggesting that protein kinase C binds to a cytoskeletal protein.

Animals↗