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.

SourceResearch connectionFrom yearThrough year

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

At least 829 records · Page 46Linked to original sources

PubMed1983

The effect of cross-linking spectrin-actin complexes with band 4.1 on the state of polymerization of the actin.

The polymerization of actin in the presence of spectrin tetramers and band 4.1 isolated from the human erythrocyte has been measured using a fluorescence energy transfer technique. The results show that the cross-linking of spectrin-actin complexes by band 4.1 results in a limited depolymerization of actin filaments and a concomitant rise in the critical actin concentration. The phenomenon may explain in part the existence of actin in the erythrocyte cytoskeleton as short oligomers rather than as long filaments.

Actins↗

PubMed1983

Induction by chemically modified actin derivatives of antibody specificity. A relation between modified sites and antibody interactions with monomeric and filamentous actins.

A comparison of specific antibodies induced by unfolded actins modified either by oxidation or by arylation of lysine residues was reported. We have focused our work on binding properties with filamentous actin and located its preferential antigenic sites for the anti-arylated-actin antibodies in the C-part of the molecule. An interference of anti-oxidized actin antibodies upon actin polymerisation has also been reported.

Actins↗

PubMed1994

Actophorin preferentially binds monomeric ADP-actin over ATP-bound actin: consequences for cell locomotion.

Actophorin from Acanthamoeba castellanii severs actin filaments and sequesters actin monomers. Here we report that actophorin binds ADP-bound monomers with higher affinity than ATP-bound monomers. Actophorin is therefore much less efficient at severing actin filaments in the presence of ADP compared to ATP, particularly taking account of the higher critical concentration in ADP. Monomer binding is also reduced in the presence of 25 mM inorganic phosphate (which is assumed to form ADP.Pi-actin). These findings are discussed in the light of observations on the nucleotide specificity of other monomer binding proteins and related to the role of actin in lamellar protrusion and cell locomotion.

Actins↗

PubMed1995

The fastest actin-based motor protein from the green algae, Chara, and its distinct mode of interaction with actin.

The endoplasmic streaming in Characean cells is an actin-dependent movement. The motor protein responsible for the streaming was partially purified and characterized. It was soluble at low ionic strength, an ATPase of a molecular mass of 225 kDa and activated more than 100 times by muscle F-actin. Surprisingly, in an in vitro motility assay, the motor protein moved muscle F-actin at 60 microns/s, which is similar to the velocity of streaming in a living cell and 10 times faster than muscle myosin. Proteolytic cleavage of actin impaired movement crucially on muscle myosin, but did not affect movement at all on the Chara motor protein, suggesting that the Chara motor protein would interact with actin via a set of sites different from those of muscle myosin.

Actins↗

PubMed1987

Anti-actin antibodies. Detection and quantitation of total and skeletal muscle actin in human plasma using a competitive ELISA.

A competitive ELISA has been used to titrate skeletal muscle and total actins in human plasma. Specific antibodies directed against the variable N-terminal 1-7 sequence and conserved sequences respectively were used. The N-terminus of actin appears to be accessible in native and brevin-complexed actins. The skeletal muscle actin isoform represents about 1% of the total circulating actin (mean: 50 micrograms/ml plasma), but is markedly increased after severe muscle tissue injuries.

Actins↗

PubMed1995

Use of monoclonal antibody 1H1, anticortactin, to distinguish normal and neoplastic smooth muscle cells: comparison with anti-alpha-smooth muscle actin and antimuscle-specific actin.

In preliminary experiments, we found that 1H1, a monoclonal antibody directed against the v-src substrate cortactin, reacts with smooth muscle, myoepithelium, myofibroblasts, and macrophages in formaldehyde-fixed human tissues. To evaluate the use of this antibody as a diagnostic reagent, we tested the immunohistochemical distribution of cortactin in 61 mesenchymal neoplasms, 11 neuroectodermal neoplasms, and eight embryonal epithelial neoplasms. The results were compared with those obtained using antibodies against alpha-smooth muscle actin and muscle-specific actin on a similar set of tissues. With the exception of positive staining in rhabdomyosarcoma, in this series only tumors with smooth muscle differentiation appeared to contain cortactin (16 of 19 leiomyosarcomas, one infantile fibrosarcoma, one malignant fibrous histiocytoma). Immunoelectron microscopy localized cortactin to the actin-associated dense bodies of the microfilament network. We conclude that cortactin may be a useful adjunct to alpha-smooth muscle actin and muscle-specific actin as a marker for the study and diagnosis of smooth muscle neoplasms and related lesions.

Actins↗

PubMed1983

Distribution of actin, myosin and actin binding protein in platelets of patients with hyperlipoproteinemia.

Significant anomalies in the quantity and relative distribution of the contractile proteins actin, myosin and actin binding protein (ABP) were observed in platelets obtained from patients with hyperbetalipoproteinemia (type IIa) and in patients with hypertriglyceridemia (type IV). Changes were observed in unfractionated platelets, (increased ABP in type IIa patients and increased actin in both type IIa and type IV) in isolated platelet membranes (increased ABP and actin in type IV, and increased myosin in type IIa) and in the KCl extract of platelets (increased actin in type IV and increased myosin in type IIa). The myosin ATPase specific activity was increased in platelets of type IV patients. No changes were observed in the concentrations and distribution of membrane glycoproteins in the platelets of these patients. The above anomalies in the contractile proteins might be relevant to the known functional anomalies of the platelets of patients with hyperlipoproteinemias.

Actins↗

PubMed1986

Fluorescence resonance energy transfer between the nucleotide binding site and Cys-10 in G-actin and F-actin.

Intramonomer fluorescence resonance energy transfer between the donor epsilon-ATP bound to the nucleotide site and the acceptor N-(4-dimethylamino-3,5-dinitrophenyl)maleimide (DDPM) or 4-dimethylaminophenyl-azophenyl-4'-maleimide bound to Cys-10 in G-actin was measured. The donor-acceptor distance was calculated to be about 40 A. The intermonomer energy transfer in F-actin occurring between epsilon-ADP and DABMI was also measured. The radial coordinate of Cys-10 was calculated to be 25 A based on the helical symmetry of F-actin and the recently calculated radial coordinate of the nucleotide binding site in F-actin i.e. 25 A (Miki, M., Hambly, B. and dos Remedios, C.G. (1986) Biochim. Biophys. Acta 871, 137-141). (The assumption has been made in calculating these distances that the energy donor and acceptor rotate rapidly relative to the fluorescence lifetime.) Corresponding distances separating the donor nucleotide in one monomer from acceptors on Cys-10 in the first and second nearest neighbours in F-actin are 39-40 A and 41-43 A.

Actins↗

PubMed1976

Fluorescence and flow dichroism of F-actin-epsilon-ADP; the orientation of the admine plane relative to the long axis of F-actin.

The excitation polarization spectrum of epsilon-ADP bound to F-actin shows that two absorption dipoles at 260 nm and 340 nm are oriented in different directions relative to the emission dipole. On the other hand, the linear dichroism of F-actin-epsilon-ADP gives that the dichroic ratio of the bound epsilon-ADP is approximately constant (about-0.5) in the wavelength region form 250 to 350nm. Furthermore, the fluorescence polarization of epsilon-ADP bound to F-actin which is oriented in the field of flow shows that the emission dipole is nearly perpendicular to the long axis of F-actin. From these observations we conclude that the adenine plane of the bound nucleotide is almost perpendicular to the long axis of F-actin.

Actins↗

PubMed1982

Fluorescence anisotropy of labelled F-actin. Influence of Ca2+ on the flexibility of F-actin.

We measured the fluorescence static anisotropy and the time-resolved fluorescence anisotropy decay of F-actin labelled with N-iodoacetyl-N'-(5-sulfo-1-naphthyl)ethylenediamine at 20 degrees C in solutions containing 100 mM KCl and free Ca2+ at various concentrations. The average fluorescence anisotropy and the fluorescence rotational correlation time of actin decreased in the presence of micromolar concentrations of free Ca2+. The change of the rotational correlation time of labelled actin could not be explained by a variation of the actin critical concentration. We concluded therefore that F-actin undergoes a conformational change induced by Ca2+ binding. The binding constant was 6 X 10(6) M-1.

Actins↗

PubMed1989

Subunit flow in F-actin under steady-state conditions. Application of a novel method to determination of the rate of subunit exchange of F-actin at the terminals.

We developed a novel method to determine the subunit exchange rates of F-actin at its terminals under quasi-steady-state conditions by using a powerful fluorescent probe, N-(1-pyrenyl)iodoacetamide. The applicability of the method was checked with regard to both theoretical and experimental aspects. We determined the rates of subunit exchange of F-actin and F-actin-tropomyosin complex under various ionic conditions. We found that: (i) KCl accelerated both on and off rates at each end, and lowered the critical concentration of the P-end while the critical concentration of the B-end was not affected; (ii) binding of tropomyosin drastically reduced the subunit flow in F-actin by suppressing the off rate principally of the P-end. It is therefore believed that tropomyosin exerts an anisotropic constraint on F-actin and regulates its dynamic polarity.

Actins↗

PubMed1985

Nucleotide sequence of the chicken cardiac alpha actin gene: absence of strong homologies in the promoter and 3'-untranslated regions with the skeletal alpha actin sequence.

The entire nucleotide sequence of the chicken cardiac alpha-actin (CC alpha A) gene has been determined. This is the first complete sequence of a cardiac actin gene that includes the promoter region, cap site, all the introns, and the polyadenylation site. The gene contains six introns, five of which interrupt the coding region at amino acids (aa) 41, 150, 204, 267, and 327. The first intron is in the 5'-noncoding region and is 438 bp in length. The CC alpha A gene encodes an mRNA of approx. 1400 bp with 5'- and 3'-untranslated region of 59 and 184 nucleotides (nt), respectively. Like the chicken skeletal alpha-actin gene, the CC alpha A gene has the codon for the aa cysteine between the initiator ATG and the codon for the N-terminal aspartic acid residue of the mature protein. There are no strong homologies (less than 13 consecutive nt) in the promoter or 3'-untranslated regions between the CC alpha A and chicken skeletal alpha-actin genes even though both are expressed in skeletal muscle during development. However, the 3'-untranslated region of the CC alpha A gene demonstrates significant sequence homology (76% over a 200-nt region) with the same region in the partial sequence of the human cardiac gene. The conservation of these sequence homologies between identical isoforms rather than the different alpha actin genes suggests these conserved regions may have a role in regulation rather than tissue-specific expression, as previously proposed.

Actins↗

PubMed2004

The PDZ-LIM protein RIL modulates actin stress fiber turnover and enhances the association of alpha-actinin with F-actin.

ALP, CLP-36 and RIL form the ALP subfamily of PDZ-LIM proteins. ALP has been implicated in sarcomere function in muscle cells in association with alpha-actinin. The closely related CLP-36 is predominantly expressed in nonmuscle cells, where it localizes to actin stress fibers also in association with alpha-actinin. Here we have studied the expression and functions of RIL originally identified as a gene downregulated in H-ras-transformed cells. RIL was mostly expressed in nonmuscle epithelial cells with a pattern distinct from that of CLP-36. RIL protein was found to localize to actin stress fibers in nonmuscle cells similarly to CLP-36. However, RIL expression led to partially abnormal actin filaments showing thick irregular stress fibers not seen with CLP-36. Furthermore, live cell imaging demonstrated altered stress fiber dynamics with rapid formation of new fibers and frequent collapse of thick irregular fibers in EGFP-RIL-expressing cells. These effects may be mediated through the association of RIL with alpha-actinin, as RIL was found to associate with alpha-actinin via its PDZ domain, and RIL enhanced the ability of alpha-actinin to cosediment with actin filaments. These results implicate the RIL PDZ-LIM protein as a regulator of actin stress fiber turnover.

Actinin↗

PubMed2004

Enaptin, a giant actin-binding protein, is an element of the nuclear membrane and the actin cytoskeleton.

Enaptin belongs to a family of recently identified giant proteins that associate with the F-actin cytoskeleton as well as the nuclear membrane. It is composed of an N-terminal alpha-actinin type actin-binding domain (ABD) followed by a long coiled coil rod and a transmembrane domain at the C-terminus. The ABD binds to F-actin in vivo and in vitro and leads to bundle formation. The human Enaptin gene spreads over 515 kb and gives rise to several splicing isoforms (Nesprin-1, Myne-1, Syne-1, CPG2). The longest assembled cDNA encompasses 27,669 bp and predicts a 1014 kDa protein. Antibodies against the ABD of Enaptin localise the protein at F-actin-rich structures throughout the cell and in focal contacts as well as at the nuclear envelope. In COS7 cells, the protein is also present within the nuclear compartment. With the discovery of the actin-binding properties of Enaptin and the highly homologous Nuance, we define a family of proteins that integrate the cytoskeleton with the nucleoskeleton.

Actinin↗

PubMed1995

Physics of actin networks. I. Rheology of semi-dilute F-actin.

The mechanical properties of cytoplasm are considered to be of underlying importance in the mechanism of cell movement and are to a large extent determined by an actin-containing cytoskeleton. Several laboratories have begun to accumulate data on the mechanical or rheologic properties of protein systems derived from the actin cytoskeleton. The focus of this manuscript is to attempt to reproduce the experimentally determined mechanical properties of non-cross-linked F-actin from theoretical considerations. It was found that a mechanical spectrum for 1 mg/ml F-actin could be calculated, which approximated experimental data, from a relaxation spectrum consisting of a long range rotational diffusion motion and short range bending motion, assuming an exponential distribution of filament lengths with a weight average length of 4 mu. The calculated spectrum underestimated the dynamic moduli at high frequencies, suggesting that a more complex actin structure is present that enhances the high frequency component.

Actins↗

PubMed2001

Neurotrophin-induced transport of a beta-actin mRNP complex increases beta-actin levels and stimulates growth cone motility.

Neurotrophin regulation of actin-dependent changes in growth cone motility may depend on the signaling of beta-actin mRNA transport. Formation of an RNP complex between the beta-actin mRNA zipcode sequence and Zipcode Binding Protein 1 (ZBP1) was required for its localization to growth cones. Antisense oligonucleotides to the zipcode inhibited formation of this RNP complex in vitro and the neurotrophin-induced localization of beta-actin mRNA and ZBP1 granules. Live cell imaging of neurons transfected with EGFP-ZBP1 revealed fast, bidirectional movements of granules in neurites that were inhibited by antisense treatment, as visualized by FRAP analysis. NT-3 stimulation of beta-actin protein localization was dependent on the 3'UTR and inhibited by antisense treatment. Growth cones exhibited impaired motility in the presense of antisense. These results suggest a novel mechanism to influence growth cone dynamics involving the regulated transport of mRNA.

3' Untranslated Regions↗

PubMed1998

Defects in actin-cap formation in Vav-deficient mice implicate an actin requirement for lymphocyte signal transduction.

BACKGROUND: Antigen-receptor interactions on lymphocytes result in local clustering of actin, receptors and signaling molecules into an asymmetric membrane structure termed a cap. Although actin polymerization is known to be required, the mechanisms underlying cap formation are unclear. We have studied the events underlying cap formation using mice bearing a null mutation in vav (vav-/-), a gene that encodes a guanine-nucleotide exchange factor for the GTPase Rac. RESULTS: Lymphocytes from vav-/- mice failed to form T-cell receptor caps following activation and had a defective actin cytoskeleton. The vav-/- T cells were deficient in interleukin-2 (IL-2) production and proliferation, and the peak of Ca2+ mobilization was reduced although of normal duration. Activation of Jun N-terminal kinase or stress-activated kinase (JNK or SAPK) and mitogen-activated protein kinase (MAPK) and the induction of the transcription factor NF-ATc1 and egr-1 genes was normal. Despite the reduced Ca2+ mobilization, translocation of cytoplasmic NF-ATc to the nucleus was normal, reflecting that the lower levels of Ca2+ in vav-/- cells were still sufficient to activate calcineurin. Treatment of lymphocytes with cytochalasin D, which blocks actin polymerization, inhibited cap formation and produced defects in signaling and IL-2 transcriptional induction in response to antigen-receptor signaling that were nearly identical to those seen in vav-/- cells. In transfection studies, either constitutively active Vav or Rac could complement constitutively active calcineurin to activate NF-AT-dependent transcription. CONCLUSIONS: These results indicate that Vav is required for cap formation in lymphocytes. Furthermore, the correlation between cap formation, IL-2 production and proliferation supports the hypothesis that an actin-dependent pathway is a source of specialized growth regulatory signals.

Actins↗

PubMed1992

Profilin-actin complexes directly elongate actin filaments at the barbed end.

We demonstrate that the profilin-G-actin complex can elongate actin filaments directly at the barbed end but cannot bind to the pointed end. During elongation, the profilin-actin complex binds to the barbed filament end, whereupon profilin is released, leaving the actin molecule behind. This was first proposed by Tilney [Tilney, L. G., et al. (1983) J. Cell Biol. 97, 112-124] and demonstrated by Pollard and Cooper [(1984) Biochemistry 23, 6631-6641] by electron microscopy. We show that a model without any outside energy supply, in contrast to the mechanism proposed by Pollard and Cooper, can be fitted to our and their [Kaiser et al. (1986) J. Cell Biol. 102, 221-226] findings. Input of outside energy is necessary only if profilin-mediated elongation continues after free G-actin has been lowered to or below the critical concentration observed at the barbed end in the absence of profilin.

Acanthamoeba↗