Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “ACTIN”

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 919 records · Page 51Linked to original sources
PubMed1981

Actin-dependent cell elongation in teleost retinal rods: requirement for actin filament assembly.

Teleost retinal rods elongate when exposed to light. Elongation is mediated by a narrow necklike region called the myoid. In the cichlid Sarotherodon mossambicus, the rod inner segment (composed of the myoid with adjacent ellipsoid) increases in length from 12 micrometers in the dark to 41 micrometers in the light. Long light-adapted myoids contain longitudinally oriented microtubules and bundles of parallel 60-A filaments that we have identified as actin by their ability to bind myosin subfragment 1. In short dark-adapted myoids, only microtubules are recognizable. Colchicine experiments reveal that light-induced rod elongation can occur in the absence of myoid microtubules. Intraocular injections of colchicine at concentrations that disrupt virtually all rod myoid microtubules do not block rod elongation. However, rod elongation is blocked by intraocular injections of cytochalasin B or cytochalasin D. The hierarchy of effectiveness of these drugs is consistent with their effectiveness in inhibiting actin assembly and in disrupting other actin-dependent motile processes. On the basis of ultrastructural observations and the results of these inhibitor studies, we propose that the forces responsible for rod elongation are dependent not on microtubules but on actin filament assembly.

Actins↗
PubMed2005

Actin is required for endocytosis at the apical surface of Madin-Darby canine kidney cells where ARF6 and clathrin regulate the actin cytoskeleton.

In epithelial cell lines, apical but not basolateral clathrin-mediated endocytosis has been shown to be affected by actin-disrupting drugs. Using electron and fluorescence microscopy, as well as biochemical assays, we show that the amount of actin dedicated to endocytosis is limiting at the apical surface of epithelia. In part, this contributes to the low basal rate of clathrin-dependent endocytosis observed at this epithelial surface. ARF6 in its GTP-bound state triggers the recruitment of actin from the cell cortex to the clathrin-coated pit to enable dynamin-dependent endocytosis. In addition, we show that perturbation of the apical endocytic system by expression of a clathrin heavy-chain mutant results in the collapse of microvilli. This phenotype was completely reversed by the expression of an ARF6-GTP-locked mutant. These observations indicate that concomitant to actin recruitment, the apical clathrin endocytic system is deeply involved in the morphology of the apical plasma membrane.

ADP-Ribosylation Factor 6↗
PubMed1984

Evolutionary conservation in the untranslated regions of actin mRNAs: DNA sequence of a human beta-actin cDNA.

We report the complete nucleotide sequence of a human beta actin cDNA. Both the 5' and 3' untranslated regions of the sequence are similar (greater than 80%) to the analogous regions of the rat beta-actin gene reported by Nudel et al (1983). When a segment of the 3' untranslated region is used as a radiolabelled probe, strong hybridization to chick beta actin mRNA is seen. This conservation of sequences suggests that strong selective pressures operate on non-translated segments of beta actin mRNA.

Actins↗
PubMed1979

Interaction of myosin subfragment-1 with actin. II. Location of the actin binding site in a fragment of subfragment-1 heavy chain.

The heavy chain of subfragment-1 prepared by chymotrypsin treatment had a molecular weight of about 96K. The heavy chain was split into 26 K, 50 K, and 21 K fragments by trypsin. When the trypsin-treated subfragment-1 was cross-linked with dimethyl suberimidate, cross-linked products of 26 K, 50 K, and 21 K fragments and of 50 K and 21 K fragments appeared, but there was little cross-linked product of 26 K and 50 K fragments or of 26 K and 21 K fragments. When the cross-linking experiments were carried out in the presence of actin, a new band appeared and the amount of cross-linked product of 26 K, 50 K, and 21 K fragments decreased by about 50%. The molecular weight of the new band was lower than that of the cross-linked product of 26 K, 50 K, and 21 K fragments, and higher than that of the dimer of actin. Based on this and some other results, we suggest that this band represented a cross-linked product of actin and the 50 K fragment. We also suggest that the decrease in the amount of cross-linked product of 26 K, 50 K, and 21 K fragments reflected the conformational change in subfragment-1 due to the binding of actin.

Actins↗
PubMed1982

Crystalline actin tubes. V. The effect of Th4+ on actin and the role of ionic charge in tube formation.

NMR and UV spectroscopy reveal that the tetravalent thorium ion interacts with actin in an identical fashion to the trivalent lanthanide ions. UV spectra and viscometry data suggest that the actin-bound Th4+ has an ionic radius of about 110 pm. Th4+ also contributes to the formation of crystalline actin tubes under appropriate conditions. The factors governing whether tubes form appear to be cationic radius and total charge on the actin monomer, rather than the valency of the ion per se.

Actins↗
PubMed1983

Electron microscopic determination of the actin filament end at which cytochalasin B blocks monomer addition using the acrosomal actin bundle from horseshoe crab sperm.

G-actin freed from exogenous ATP was added to the pieces of isolated acrosomal actin bundles from horseshoe crab sperm to form filaments as reported earlier (Tilney, L.G., Bonder, E.M., & DeRosier, D.J. (1981) J. Cell Biol. 90, 485-494). The growth of a filament was far more rapid at one end (the preferred end) than the other end. These ends were shown to correspond to the barbed and pointed ends, respectively, by decoration of the filaments with myosin subfragment 1. Cytochalasin B inhibited the monomer addition at the preferred end. This technique is useful in determining the ends to which actin filament end-binding proteins from nonmuscle cells bind, which are considered to regulate the actin polymerization in the cells.

Acrosome↗
PubMed1982

Isolation from thyroid cells or purified plasma membranes with associated actin microfilaments. Proteins bound to actin.

Plasma membranes of thyroid cells were purified from hog thyroid glands following two procedures. Their homogeneity was tested by electron microscopy and by measurements of the activity of membrane-bound enzyme markers. According to the procedure used the membrane fractions obtained present some differences in their morphological features as well as in the repartition of the activities of the membrane-bound enzyme markers. However, whatever the composition of the membrane fraction examined (membrane vesicles, single membrane sheets with junctional complexes), decoration with heavy meromyosin clearly shows the presence of actin filaments attached to these fragments. Analysis of proteins by polyacrylamide gel electrophoresis indicates the presence of about twelve major components with actin. Treatment of membranes with Triton X-100 results in an insoluble core which contains all the actin and most of the major proteins. The selective extraction of these components by buffers differing in their ionic strength, pH, or the presence or absence of ATP X Mg has been used to characterize some of the proteins associated to actin; among them are filamin, myosin, alpha-actinin, tropomyosin.

Actins↗
PubMed1997

Molecular cloning of actin genes in Trichomonas vaginalis and phylogeny inferred from actin sequences.

The parasitic protozoan Trichomonas vaginalis is known to contain the ubiquitous and highly conserved protein actin. A genomic library and a cDNA library have been screened to identify and clone the actin gene(s) of T. vaginalis. The nucleotide sequence of one gene and its flanking regions have been determined. The open reading frame encodes a protein of 376 amino acids. The sequence is not interrupted by any introns and the promoter could be represented by a 10 bp motif close to a consensus motif also found upstream of most sequenced T. vaginalis genes. The five different clones isolated from the cDNA library have similar sequences and encode three actin proteins differing only by one or two amino acids. A phylogenetic analysis of 31 actin sequences by distance matrix and parsimony methods, using centractin as outgroup, gives congruent trees with Parabasala branching above Diplomonadida.

Actins↗
PubMed1989

A yeast actin-binding protein is encoded by SAC6, a gene found by suppression of an actin mutation.

The protein encoded by SAC6, a gene that can mutate to suppress a temperature-sensitive defect in the yeast actin gene, has been identified as a 67-kilodalton actin-binding protein (ABP 67) that associates with all identifiable actin structures. This finding demonstrates the in vivo functional importance of the actin-ABP 67 interaction previously established in vitro and illustrates the use of suppressor analysis to identify physically interacting proteins.

Actins↗
PubMed2005

Actin-binding proteins from Burkholderia mallei and Burkholderia thailandensis can functionally compensate for the actin-based motility defect of a Burkholderia pseudomallei bimA mutant.

Recently we identified a bacterial factor (BimA) required for actin-based motility of Burkholderia pseudomallei. Here we report that Burkholderia mallei and Burkholderia thailandensis are capable of actin-based motility in J774.2 cells and that BimA homologs of these bacteria can restore the actin-based motility defect of a B. pseudomallei bimA mutant. While the BimA homologs differ in their amino-terminal sequence, they interact directly with actin in vitro and vary in their ability to bind Arp3.

Actin-Related Protein 3↗
PubMedDate not supplied

Effect of liver plasma membranes on G-actin. I. Possible implication of membrane NPases in inactivation of G-actin.

G-actin incubated in the presence of a liver fraction enriched in plasma membranes is rapidly inactivated, as indicated by the biphasic loss of polymerizability and DNase inhibition. The rates of inactivation as measured by viscosity are greatly influenced by temperature, but almost independent of membrane concentrations at least in the low range of concentrations tested (less than 250 micrograms protein/ml). The loss of DNase inhibition capacity proceeds at rates two to three times slower than the loss of polimerizability. The inactivation of actin in the presence of membranes cannot be attributed to proteolysis nor to a phosphorylation of actin by membranes. However, it is shown that in the course of the incubation, medium ATP is rapidly converted into AMP and adenosine and that the destruction of ATP is almost complete at the start of the inactivation process. A mechanism is presented relating the destruction of ATP to actin inactivation.

Actins↗
PubMed1998

Deposition of IgG anti-actin antibodies on kidneys of glomerular nephropathy patients with an enhanced glomerular alpha smooth muscle actin expression.

In this study, we have attempted to evaluate by immunohistochemistry assay the glomerular alpha smooth muscle actin (ASMA) expression in 53 kidney biopsy specimens obtained from patients with glomerular nephropathy as compared with 16 histologically normal human kidneys. An enhanced mesangial ASMA expression was observed in 26 of 53 specimens of patients with glomerulonephritis. In contrast, normal glomeruli showed no ASMA-positive mesangial cells. Furthermore, we have analyzed the specificities of antibodies eluted from kidney biopsy specimens from patients and controls using an enzyme immunoassay against a panel of self antigens composed of actin, myosin, tubulin and DNA. The antibodies eluted from exclusively renal biopsy specimens of patients with an enhanced glomerular ASMA expression showed high IgG activity restricted to actin. Our results demonstrated the presence of IgG anti-actin activity in glomerular nephropathy patients with an enhanced mesangial ASMA expression.

Actins↗
PubMed1999

Three actin cross-linking proteins, the 34 kDa actin-bundling protein, alpha-actinin and gelation factor (ABP-120), have both unique and redundant roles in the growth and development of Dictyostelium.

The contribution of three actin cross-linking proteins, alpha-actinin (alphaA), gelation factor (ABP-120), and the 34 kDa actin-bundling protein to cellular functions has been studied in three single mutant (alphaA-, 120-, and 34-) and three double mutant (alphaA-/120-, 34-/alphaA-, 34-/120-) strains of Dictyostelium generated by homologous recombination. Strains alphaA-/120- and 34-/alphaA- exhibited a reduced rate of pinocytosis, grew to lower saturation densities, and produced small cells in shaking cultures. All strains grew normally in bacterial suspensions and on agar plates with a bacterial lawn. Slow growth under conditions of reduced temperature and increased osmolarity was observed in single mutants 34- and alphaA-, respectively, as well as in some of the double mutant strains. Motility, chemotaxis, and development were largely unaltered in 34-/alphaA- and 34-/120- cells. However, 34-/alphaA- cells showed enhanced aggregation when starved in suspension. Moreover, morphogenesis was impaired in both double mutant strains and fruiting bodies of aberrant morphology were observed. These defects were reverted by re-expression of one of the lacking cross-linking proteins. The additive and synthetic phenotypes of these mutations indicate that actin cross-linking proteins serve both unique and overlapping functions in the actin cytoskeleton.

Actinin↗
PubMed1998

Osteocyte shape is dependent on actin filaments and osteocyte processes are unique actin-rich projections.

Osteocytes are derived from a select group of osteoblasts that have undergone a final differentiation. Due to their inaccessibility when embedded in the bone matrix, very little is known about the osteocyte cytoskeleton. This study provides an extensive analysis of the osteocyte cytoskeleton, based on the successful isolation of osteocytes from 16-day embryonic chick calvariae. We used OB7.3, a chicken osteocyte-specific monoclonal antibody, to confirm the osteocytic phenotype of the isolated cells and established culture conditions to promote growth of cells that most resemble osteocytes in vivo. Immunofluorescence staining with antitubulin, antivimentin, and antiactin showed the relative distribution of the microtubules, intermediate filaments, and actin filaments in both osteocyte cell body and processes. Field emission scanning electron microscopy revealed the three-dimensional relationships of the cytoskeletal elements and a unique organization of actin bundles that spanned the cell body and osteocyte processes. When combined with drug studies, these experiments demonstrate that actin filaments are crucial for the maintenance of osteocyte shape. Furthermore, we identified two actin-bundling proteins, alpha-actinin and fimbrin, in osteocyte processes. The prominence and unique distribution of fimbrin in osteocyte processes provides the possibility of its use as an intracellular marker to distinguish osteocytes from osteoblasts.

Actinin↗
PubMed1989

Immunoelectron microscopic localization of actin, alpha-actinin, actin-binding protein and myosin in resting and activated human blood platelets.

Blood platelets are particularly rich in cytoskeletal proteins and respond to stimulation and activation by changes in shape. We examined the effect of blood platelet activation on the subcellular distribution of the cytoskeletal proteins, actin, myosin, alpha-actinin and actin-binding protein. These studies were performed with immunofluorescent staining on thin cryosections of paraformaldehyde-fixed platelets and by immunogold labeling of ultrathin cryosections of glutaraldehyde-fixed blood platelets. Platelets were studied immediately at blood collection (resting platelets), in platelet-rich plasma and after gel filtration (partially activated platelets), and after gel filtration and thrombin activation (0.5 U/ml, 10 min, 37 degrees C) (activated platelets). Resting platelets were disk-shaped and showed homogeneous distribution of cytoskeletal proteins. Partially activated platelets were more spherical and showed at least one protrusion. Immunofluorescence and immunogold labeling showed a more intense staining of the peripheral 0.2 to 0.3 micron of cytoplasm of these platelets. In the immunofluorescence photographs this resulted in the appearance of small fluorescent rings with staining at the periphery of cross-sectioned cells. Activated platelets showed an irregular outline composed of broad based pseudopods. Cell centers were composed of poorly delineated electron-dense material, interspersed with profiles of surface-connected tubules. The broad based pseudopods stained uniformely for actin, alpha-actinin and actin-binding protein. The cell center stained poorly for these proteins. Myosin staining was found in the peripheral cortex, but also in the cell center. Partially activated platelets that had returned to the disk shape after incubation at 37 degrees C showed increased submembranous concentration of microfilament proteins. These data reveal the profound cytoskeletal rearrangements that already occur upon minimal platelet activation and emphasize that platelets that have returned to the disk shape are not identical to resting platelets.

Actinin↗
PubMed1980

Actin-myosin interaction in oriented F-actin filament system.

The decorated actin technique combined with the spin label method was used to study the interaction of skeletal muscle actin and myosin in synthetic filament system. If follows from the orientation dependence of the EPR spectra of the rigidly attached spin label in F-action filaments that the spin-label is sensitive to the dynamic state of the filaments. The interaction of myosin heads with actin reduces the intrinsic order of the F-actin filaments. The interaction seems to be cooperative.

Actins↗
PubMed1981

Fluorimetry study of N-(1-pyrenyl)iodoacetamide-labelled F-actin. Local structural change of actin protomer both on polymerization and on binding of heavy meromyosin.

A fluorescent reagent, N-(1-pyrenyl)iodoacetamide, was conjugated to rabbit skeletal muscle actin at the site of the most reactive sulfhydryl group, and fluorescence characteristics (excitation and emission spectra, quantum yields, lifetimes) of the conjugate were investigated. Associated with polymerization of labelled G-actin, the fluorescence intensity at 407 nm, after excitation at 365 nm, was enhanced by a factor of about 25. It was reduced to about 25% on the binding of heavy meromyosin (or subfragment 1). The results suggest that binding of heavy meromyosin to the protomer of F-actin alters the local structure of the protomer towards a G-actin-like one.

Actins↗
PubMed1981

Crystalline actin tubes. IV. Structural information on actin monomers obtained from computer-averaged lattice images.

Crystalline actin tubes can be formed in the presence of Pr(III) and examples can be selected which are opened along their length. The structural unit cell seen in electron micrographs were computer-averaged to obtain the projected size and shape of the actin monomer. There are two monomers per unit cell, each related by a two-fold axis perpendicular to the plane of the projection. Each 3.3 x 5.5 nm monomer was markedly asymmetric. Skeletal muscle actin strongly resembles Acanthamoeba actin (Aebi et al. (1980) Nature 288, 296) although the projected dimensions may vary slightly.

Actins↗