Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Cytoskeleton”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 613 records · Page 34Linked to original sources
PubMed1994

Mediation of the physiological response of platelets by interactions of spectrin and protein 4.1 with the cytoskeleton.

Spectrin and protein 4.1 became associated with the Triton-insoluble cytoskeletons during platelet activation. Inhibition of platelet activation by a PGI2 analogue resulted in release of the proteins from the cytoskeletons. Changes in subcellular distributions of the proteins preceded changes in the state of platelet aggregation. These results suggest that interactions of spectrin and protein 4.1 with the cytoskeletons are involved in mediating the physiological response of the platelet.

Actins↗
PubMed1996

Antiproliferative activity of 3-aminobenzamide in A431 carcinoma cells is associated with a target effect on cytoskeleton.

3-Aminobenzamide (3-ABA) is an inhibitor of poly(ADP-ribose)polymerase (PARP), an enzyme involved in several cellular processes, and exerts its effects by acting at the cytoskeleton level. Here we show that 3-ABA has an antiproliferative effect on the human carcinoma cell line A431, as measured by different assays. 3-ABA was capable of inhibiting cell growth as well as colony formation, this inhibitory effect is reversible. Morphological analyses showed a series of cellular alterations, such as a remarkable increase of dendritic-like protrusions, quite unusual in epithelial cells, and suggestive of a differentiative triggering. Immunocytochemical studies suggested that a major target of 3-ABA was indeed the cytoskeleton. These data, together with those of the literature, indicate that 3-ABA, depending on cell histotype and drug concentration, is a versatile drug capable of exerting antiproliferative and cytostatic effects as well as cytotoxic and antiapoptotic effects, processes sharing an important involvement of cytoskeleton. These unique characteristics of 3-ABA may be of interest for cancer research.

Actins↗
PubMed1996

Phospholipase C-gamma 1 binds to actin-cytoskeleton via its C-terminal SH2 domain in vitro.

Association of phospholipase C (PLC)-gamma 1 with the cytoskeleton has been postulated to be one of the crucial steps for PLC-gamma 1 activation and translocation to the plasma membrane. In this report, direct binding assays were carried out to study which fragment of PLC-gamma 1 Src homology region has been able to bind to the actin-cytoskeleton. Using GST fusion proteins containing various deletions of the PLC-gamma 1 Src homology region, it was found that PLC-gamma 1 binds to the actin-cytoskeleton directly via its C-terminal SH2 domain but not the SH3 domain in vitro. However, the binding of the C-terminal SH2 domain of PLC-gamma 1 to actin did not interfere with the SH2 domain's ability to associate with phosphotyrosine, which suggested that actin and phosphotyrosine residues may bind to different sequences in the C-terminal SH2 domain of PLC-gamma 1.

Actins↗
PubMed1999

Disruption of beta(2)-integrin-cytoskeleton coupling abolishes the signaling capacity of these integrins on granulocytes.

Integrin-dependent adhesion and dynamic modulations of the actin network are prerequisites for normal cell locomotion. To investigate whether the actin microfilamentous system does play a role in regulation of beta(2)-integrin-induced signalling, we pretreated granulocytes with staurosporine, a well-known protein kinase inhibitor that has also been shown to disrupt the cytoskeleton of intact cells. Pretreatment with staurosporine completely inhibited the beta(2)-integrin-induced Ca(2+) signal and also its ability to trigger actin polymerisation. This inhibition was not related to phosphorylation of the CD18-chain of the beta(2)-integrin, nor to inhibition of protein kinases. Instead, association of beta(2)-integrins with the cortical cytoskeleton, which was observed in untreated cells, was abolished after exposure to staurosporine, indicating that beta(2)-integrin signalling depends on integrin-cytoskeleton interaction. These results suggest not only that the actin network provides an adhesive link to the extracellular matrix and a driving force for the locomotory response, but also that it participates in regulation of beta(2)-integrin signalling during granulocyte locomotion.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1993

The dual effects of Ca2+ on binding of the glycolytic enzymes, phosphofructokinase and aldolase, to muscle cytoskeleton.

We show here that in rat diaphragm muscle, a short time of incubation with the Ca(2+)-ionophore A23187 induced an increase in cytoskeleton-bound phosphofructokinase (EC 2.7.1.11) and aldolase (EC 4.1.2.13), whereas a longer period of incubation, which causes a pathological rise in intracellular Ca2+, induced a decrease in bound enzymes. Lactate concentration correlated with both phases of Ca2+ action on the binding of the enzymes. The increase in cytoskeleton-bound enzymes could be prevented by treatment with the calmodulin antagonists trifluoperazine or CGS 9343B (a novel, potent, and selective inhibitor of calmodulin activity). These results suggest that calmodulin is involved in the Ca(2+)-induced binding of the enzymes to muscle cytoskeleton.

Animals↗
PubMed1993

Stimulatory effect of epidermal growth factor on binding of glycolytic enzymes to muscles cytoskeleton and the antagonistic action of calmodulin inhibitors.

We report here on a novel mechanism involved in epidermal growth factor (EGF) action, which shows that EGF rapidly stimulates binding of the glycolytic enzymes, phosphofructokinase (EC 2.7.1.11), and aldolase (EC 4.1.2.13) to muscle cytoskeleton. This effect was demonstrated both in vivo, in the tibialis anterior muscle from rats injected with EGF, and in vitro, in the isolated rat diaphragm muscle incubated with EGF. The increase in cytoskeleton-bound glycolytic enzymes induced by EGF was prevented, in both the in vivo and in vitro experiments, by treatment with the calmodulin antagonists trifluoperazine or CGS 9343B (a potent and selective inhibitor of calmodulin activity), which strongly suggests that Ca2+ and calmodulin are involved in this effect of EGF. Our previous findings have revealed that insulin or Ca2+ exert a similar rapid stimulation of cytoskeletal glycolysis, which is also calmodulin mediated. We now hypothesize that this may be a general mechanism of signal transduction in the cell, involving Ca(2+)-mobilizing hormones and growth factors, and supplying local ATP, in the vicinity of cytoskeleton-membrane, which is required for the rapid cytoskeletal-membrane rearrangements upon membrane-induced events.

Animals↗
PubMed1995

Effect of insulin-induced hypoglycemia on cytoskeleton-bound and cytosolic phosphofructokinase and the levels of glucose 1,6-bisphosphate in rat brain.

We investigated the regulatory mechanisms which may account for the reduction of glycolysis in brain during severe hypoglycemia. Phosphofructokinase (PFK), the rate-limiting enzyme in glycolysis, is known to be regulated by allosteric effectors, as well as by a reversible binding to cell cytoskeleton. These two mechanisms were studied, in rat brain, during insulin-induced hypoglycemia. Our experiments revealed that the intracellular distribution of PFK was not changed during severe hypoglycemia. However, the allosteric activity of the enzyme (assayed under conditions in which it is sensitive to allosteric effectors) from both the cytosolic (soluble) and cytoskeletal fractions, was significantly reduced. This reduction may be attributed to the marked fall in the level of glucose 1,6-bisphosphate (Glc-1,6-P2), the potent allosteric activator of PFK, as well as to the more moderate decrease in fructose 2,6-bisphosphate and the decrease in fructose 1,6-bisphosphate (the product and allosteric activator of the enzyme). In contrast to our previous findings in muscle, the cytoskeleton-bound PFK from brain was found to be sensitive to allosteric effectors like the soluble enzyme. This may explain the reduction in the allosteric activity of PFK in both the cytosolic and cytoskeletal fractions from brain. The decline in cytoskeleton-bound and cytosolic PFK activity, induced by the fall in its allosteric activators, may lead to the reduction in brain glycolytic rate, which was reflected by the marked decrease in lactate content during hypoglycemia.

Allosteric Regulation↗
PubMed1996

Association of murine splenocyte CD3 complex to the cytoskeleton: absence of modulation by exogenous fatty acids.

The cytoplasmic regions of the CD3 complex are presumably involved in signal transduction following ligand-receptor binding. We investigated the effects of incubating either stearic or oleic acid on the association of murine lymphocyte CD3 complex with the cytoskeleton. Both cytochalasin D, an inhibitor of microfilament formation, and W7, an inhibitor of calmodulin, inhibited capping of CD3. The association of CD3 with the cytoskeleton was confirmed by confocal laser scanning microscopy studies, which showed co-localization of the cross-linked CD3 receptors and the membrane attachment proteins ankyrin and fodrin. Although exogenous oleic acid increased plasma membrane fluidity, neither expression nor capping of CD3 receptors was increased. Nonetheless, oleic acid did increase uptake of tritiated thymidine after binding of anti-CD3 antibodies. Lymphoproliferation was progressively inhibited by both cytochalasin D and W7, confirming the importance of intact cytoskeleton for cellular activation.

Animals↗
PubMed1999

The pleckstrin homology domain of the Wiskott-Aldrich syndrome protein is involved in the organization of actin cytoskeleton.

In this study, we investigated the role of the pleckstrin homology (PH) domain of the Wiskott-Aldrich syndrome protein (WASP) in the regulation of actin cytoskeleton, which is defective in patients with Wiskott-Aldrich syndrome (WAS) and X-linked thrombocytopenia (XLT). Overexpression of the WASP in COS-7 cells cultured in the presence of fetal calf serum (FCS) resulted in large cluster formation of polymerized actin and WASP in the cytoplasm. In contrast, when the WASP transfected cells were cultured in the absence of FCS, activation with PMA or EGF was required to induce cluster formation. Overexpression of WASP with a missense mutation in the N-terminus of the PH domain failed to induce the large cluster formation in COS-7 cells even in the presence of FCS. We also found that phosphatidylinositol 4,5-bisphosphate (PIP(2)), which is known to regulate the actin cytoskeleton, binds to the PH domain of WASP, and the binding was abolished by the introduction of a missense mutation into the N-terminus but not the C-terminus of the PH domain. Together with the observations that most of the missense mutations observed in patients with WAS and XLT are located within the PH domain, these results indicate that the PH domain of WASP plays important roles in the regulation of actin cytoskeleton and suggested that the binding of PIP(2) to the PH domain is necessary for WASP to function properly.

Actins↗
PubMed1997

Phosphatidylinositol 3-kinase association with the osteoclast cytoskeleton, and its involvement in osteoclast attachment and spreading.

Osteoclast activation involves attachment to the mineralized bone matrix and reorganization of the cytoskeleton, leading to polarization of the cell. Signaling molecules, PI3-kinase, rho A, and pp60c-src, were shown to be essential for osteoclastic bone resorption. In this study we have focused on the involvement of these signaling molecules in the early event of osteoclast activation: attachment, spreading, and organization of the cytoskeleton. Highly purified osteoclasts were fractionated into Triton X-100-soluble or cytosolic and Triton X-100-insoluble or cytoskeletal fractions, and the distribution of above-mentioned signaling molecules between the two fractions was examined. PI3-kinase, rho A, and pp60c-src all showed translocation to the cytoskeletal fraction upon osteoclast attachment to plastic. However, PI3-kinase and rho A, but not pp60c-src, showed further translocation of 2.4- and 3.2-fold, respectively, upon attachment of osteoclasts to bone. PI3-kinase translocation to the cytoskeleton was inhibited by either cytochalasin B or colchicine. Furthermore, treatment of osteoclasts with the PI3-kinase inhibitor wortmannin decreased its translocation, suggesting that PI3-kinase activity was needed for its translocation. Moreover, wortmannin inhibited osteoclast attachment to both bone and plastic and caused drastic changes in osteoclast morphology resulting in rounding of the cells, disappearance of F-actin structures or podosomes, and appearance of punctate or vesicular structures inside the cells. Osteoblastic MB1.8 cells and IC-21 macrophages did not show additional translocation of PI3-kinase or rho A upon attachment to bone or changes in attachment or morphology in response to wortmannin. Finally, PI3-kinase coimmunoprecipitated with alpha v beta 3 integrin from osteoclasts.

Androstadienes↗
PubMed1994

Protein kinase C association with the retinal cytoskeleton and phosphorylation of vimentin.

Protein kinase C plays an important role in regulation of the cytoskeleton. We found that protein kinase C activity is associated with the retinal cytoskeleton, and that it catalyses the stoichiometric phosphorylation of two cytoskeletal proteins, with apparent molecular masses of 56 kDa and 100 kDa. The 56-kDa substrate was identified as vimentin on the basis of its apparent molecular mass, pI, solubility, immunoreactivity, pattern of proteolysis by Lys-C and a partial amino acid sequence. Immunomicroscopy was consistent with previous reports that in the retina vimentin has the unusual property of being present in neuronal cells--horizontal cells--as well as non-neuronal cells. The characteristics of protein kinase C phosphorylation of vimentin that was enriched in neuronal vimentin were determined. Hyperactivation of protein kinase C by treatment of retinas with phorbol myristate acetate resulted in the phosphorylation of vimentin in situ, indicating that the phosphorylation is physiologically relevant. In vitro, purified retinal protein kinase C catalysed the incorporation of nearly 2 mol phosphate per mole of monomeric vimentin. The phosphorylation was highly dependent on the presence of phosphatidylserine. Thus, protein kinase C functions in the retinal cytoskeleton, where a major role is in the modification of vimentin. The characterization of the phosphorylation of outer retinal vimentin by protein kinase C provides a basis for further studies on the regulation and function of this cytoskeletal element.

Animals↗
PubMed1996

A 23Na multiple-quantum-filtered NMR study of the effect of the cytoskeleton conformation on the anisotropic motion of sodium ions in red blood cells.

Recently, it has been shown that 23Na double-quantum-filtered NMR spectroscopy can be used to detect anisotropic motion of bound sodium ions in biological systems. The technique is based on the formation of the second-rank tensor when the quadrupolar interaction is not averaged to zero. Using this method, anisotropic motion of bound sodium in human and dog red blood cells was detected, and the effect was shown to depend on the integrity of the membrane cytoskeleton. In the present study, multiple-quantum-filtered techniques were applied in combination with a quadrupolar echo to measure the transverse-relaxation times, T2f and T2s. Line fitting was performed to obtain the values of the residual quadrupolar interaction, which was measured for sodium in a variety of mammalian erythrocytes of different size, shape, rheological properties, and sodium concentrations. Human unsealed white ghosts were used to study sodium bound at the anisotropic sites on the inner side of the RBC membrane. Modulations of the conformation of the cytoskeleton by the variation of either the ionic strength or pH of the suspending medium caused drastic changes in both the residual quadrupolar interaction and T2f due to changes in the fraction of bound sodium ions as well as changes in the structure of the binding sites. By combining the two spectroscopic parameters, structural change can be followed. The changes in the structure of the sodium anisotropic binding sites deduced by this method were found to correlate with known conformational changes of the membrane cytoskeleton. Variations of the medium pH affected both the fraction of bound sodium ions and the structure of the anisotropic binding sites. Sodium and potassium were shown to bind to the anisotropic binding sites with the same affinity.

Algorithms↗
PubMed2001

Activator protein 1 activation following hypoosmotic stress in HepG2 cells is actin cytoskeleton dependent.

BACKGROUND: Following hypoosmotic stress-induced cell volume change, the actin cytoskeleton reorganizes itself. The role of this reorganization in the activation of the phosphatidylinositol 3-OH-kinase/protein kinase B/activator protein 1 (PI-3-K/PKB/AP-1) proliferative signaling cascade is unknown. Focal adhesion kinase (FAK) participates in the cytoskeleton-based activation of PI-3-K. We hypothesized that hypoosmotic stress-induced activation of PKB and AP-1 in HepG2 cells is dependent on an intact actin cytoskeleton and subsequent FAK phosphorylation. METHODS: HepG2 cells were incubated for 1 h with or without 20 microM cytochalasin D, an actin disrupter, and were then exposed for up to 30 min to hypoosmotic medium (200 mOsm/L) to induce swelling. Tumor necrosis factor alpha (1.4 nM) and medium alone served as positive and negative controls, respectively. Western blots measured cytoplasmic phosphorylated or total FAK and PKB. EMSAs measured nuclear AP-1. All experiments were performed in triplicate. RESULTS: Exposure to hypoosmotic stress resulted in activation of the following signaling messengers in a sequential fashion: (1) phosphorylation of FAK occurred by 2 min, (2) phosphorylation of PKB occurred by 10 min, (3) nuclear translocation of AP-1 occurred by 30 min. All three signaling events were abolished when these cells were pretreated with cytochalasin D. CONCLUSION: Actin reorganization following hypoosmotic stress is essential for the FAK-mediated activation of the PI-3-K/PKB/AP-1 proliferative cascade. These data delineate a possible mechanism by which the cell swelling-induced cytoskeletal changes can initiate proliferative signal transduction in human liver cancer.

Actins↗
PubMed2000

A probabilistic model for ligand-cytoskeleton transmembrane adhesion: predicting the behavior of microspheres on the surface of migrating cells.

A theoretical model describing the attachment and cytoskeletal coupling of microspheres to the dorsal surface of motile cells was developed. Integral membrane receptors beneath a ligand-coated microsphere are allowed to be either free, attached to the microsphere, bound to the rearward moving actin network, or linked to both the bead and the cytoskeleton, and to switch between these four states. The binding transitions being modeled as chemical reactions governed by rate constants taken from literature, the chance for a receptor to be in each binding state over time is obtained by solving mass-balance equations for the probability functions. The population of n such receptors beneath the microsphere is accounted for by a binomial distribution for each state. Adhesion and transmembrane coupling (resulting in microsphere transport) being defined by a minimal number of ligand-receptor and receptor-cytoskeleton bonds, respectively, the probabilities of attachment and transport of the microsphere over time are expressed in terms of state probability distributions. It is found that increasing the ligand density raises the attachment and transport probabilities, in good quantitative agreement with recent experiments using optical tweezers and accurate position tracking. Increasing the bead size does not affect attachment, but raises the transport probability with a marked transition for bead diameter around 100 nm, as for experimental data. Increasing the restraining force decreases the transport probability, probably by inducing a rupture of receptor-cytoskeleton bonds. This study thus provides a framework that helps understand the process of cortical flow associated with cell locomotion.

Animals↗
PubMed1993

Isolation of myosin from Dictyostelium cytoskeletons.

Dictyostelium has several isoforms of "unconventional" single-headed myosins that do not assemble into filaments (myosin I). In contrast, there is only one form of conventional myosin (myosin II) that self-assembles into bipolar thick filaments, and molecular genetic studies have shown that this myosin is an essential motor protein for several cell functions, including cytokinesis. Myosin II is phosphorylated on both the heavy chain and light chain, and these modifications regulate assembly and ATPase activity. A large fraction of the myosin II remains associated with structures that are resistant to extraction with nonionic detergents (the Triton cytoskeleton). These cytoskeletons retain the ability to contract in an ATP-dependent manner and can easily be isolated by low-speed centrifugation. A method for the rapid purification of myosin II from cytoskeletons is described. This method is simple and avoids the need for sonication, ultracentrifugation of large volumes, and overnight dialysis. The subunit composition, assembly properties, and enzyme activity are similar to those reported for myosin prepared from soluble extracts.

Animals↗
PubMed1993

Regulation of platelet function by the cytoskeleton.

The platelet cytoskeleton contains two actin filament-based components. One is the cytoplasmic actin filaments that fill the cytoplasm and mediate contractile events. The other is the membrane skeleton that coats the plasma membrane and regulates properties of the membrane such as its contours and stability and the lateral distribution of membrane glycoproteins. Recent work reviewed in this article indicates that the GP IIb-IIIa complex can associate with the membrane skeleton. Upon platelet activation, GP IIb-IIIa becomes competent to bind its adhesive ligand, fibrinogen. This induces a reorganization of the cytoskeleton such that the membrane skeletal proteins with which GP IIb-IIIa is associated become associated with underlying cytoplasmic filaments. As in focal contacts of cultured cells, this ligand-induced association of GP IIb-IIIa with cytoplasmic actin filaments regulates the ability of GP IIb-IIIa to bind adhesive ligand. Intracellular enzymes that are activated as a consequence of ligand binding to the GP IIb-IIIa complex include tyrosine kinase(s) and calpain, making these potential candidates for enzymes inducing the two-way signaling across the membrane. Additional candidates include phosphoinositide 3-kinase and protein kinase C, other enzymes that have been detected in focal contacts of aggregating platelets. Future studies identifying interactions between the GP IIb-IIIa complex and membrane skeletal proteins should help to further elucidate the significance of the GP IIb-IIIa in cytoskeleton interaction in regulating integrin-mediated transmembrane signaling in platelets.

Actins↗
PubMed2000

Cell-anchorage, cell cytoskeleton, and Rho-GTPase family in regulation of cell cycle progression.

It has been well known that cell-anchorage and the cell cytoskeleton are deeply involved in the regulation of cell proliferation and cell cycle. However, the precise molecular mechanism involved in cell-anchorage and the cell cytoskeleton have remained be to elucidated. The recent great volume of information regarding cell cycle regulators such as cyclin, cyclin-dependent kinases (CDKs) and CDK inhibitors (CKI) has facilitated the understanding of the cell cycle in mammalian cells. In this review, we will focus on these cell cycle regulators to discuss the regulation of cell proliferation controlled by cell-anchorage and the cytoskeleton, and especially the roles of Rho family GTPases.

Animals↗
PubMed1987

The cytoskeleton of cryofixed Purkinje cells of the chicken cerebellum.

Cerebella of 3- to 6-week-old chickens were cryofixed in a nitrogen-cooled propane jet, deep-etched and rotary-shadowed. The use of a brief perfusion of 0.32 M sucrose improved the quality of the cryofixation and allowed the study of the deeper layers of the cerebellar cortex. It is reported that the cytoskeleton of the Purkinje cells (PC) shows distinct domains and composition of filamentous structures in the different regions of the cell cytoplasm, such as the perikaryon, the cytoplasm of dendrites and the axoplasm. The perikaryon is occupied by a meshwork of fine filaments, 4-7 nm in diameter, that extends from the nuclear outer membrane to the cell membrane. In this zone the cell organelles (e.g., endoplasmic reticulum, mitochondria) adopt a circular arrangement around the nucleus. All structures are anchored by microfilaments to the cytoplasmic network. The dendrites show a dense cytoplasmic network including bundles of microtubules, neurofilaments and microfilaments. Numerous aggregated globular components are attached to this cytoskeleton. The cytoskeleton of the dendritic spines shows axially oriented 10-nm bundles of filaments, which are interconnected and anchored also to the cell membrane and the components of the agranular endoplasmic reticulum by cross-linkers. As described in peripheral nerves, the axoplasm of axons in the central nervous system exhibits predominantly neurofilaments and microtubules aligned along the axis of the neurites in a three-dimensional arrangement and interconnected by cross-linker filaments and filamentous structures.

Animals↗