Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Talin”

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 127 records · Page 7Linked to original sources
PubMed1995

A talin homologue of Dictyostelium rapidly assembles at the leading edge of cells in response to chemoattractant.

In an attempt to identify unknown actin-binding proteins in cells of Dictyostelium discoideum that may be involved in the control of cell motility and chemotaxis, monoclonal antibodies were raised against proteins that had been enriched on an F-actin affinity matrix. One antibody recognized a protein distinguished by its strong accumulation at the tips of filopods. These cell-surface extensions containing a core of bundled actin filaments are rapidly protruded and retracted by cells in the growth-phase stage. The protein of 269 kD turned out to resemble mouse fibroblast talin (Rees et al., 1990) in its primary structure. The fit is best among the first 400-amino acid residues of the NH2-terminal region where identity between the two proteins is 44% and the last 200-amino acid residues of the COOH-terminal region with 36% identity. In the elongated cells of the aggregation stage the Dictyostelium talin is accumulated at the entire front where also F-actin is enriched. Since this protein exists in a soluble state in the cytoplasm, mechanisms are predicted that cause accumulation at sites of the cell where a front is established. Evidence for receptor-mediated accumulation was obtained by local stimulation of cells with cAMP. When a new front was induced by the chemoattractant, the talin accumulated there within half a minute, indicating a signal cascade in Dictyostelium responsible for assembly of the talin beneath sites of the plasma membrane where chemoattractant receptors are strongly activated. The ordered assembly of the talin homologue together with actin and a series of other proteins is considered to play a key role in chemotactic orientation.

Actins↗
PubMed1998

Layilin, a novel talin-binding transmembrane protein homologous with C-type lectins, is localized in membrane ruffles.

Changes in cell morphology and motility are mediated by the actin cytoskeleton. Recent advances in our understanding of the regulators of microfilament structure and dynamics have shed light on how these changes are controlled, and efforts continue to define all the structural and signaling components involved in these processes. The actin cytoskeleton-associated protein talin binds to integrins, vinculin, and actin. We report a new binding partner for talin that we have named layilin, which contains homology with C-type lectins, is present in numerous cell lines and tissue extracts, and is expressed on the cell surface. Layilin colocalizes with talin in membrane ruffles, and is recruited to membrane ruffles in cells induced to migrate in in vitro wounding experiments and in peripheral ruffles in spreading cells. A ten-amino acid motif in the layilin cytoplasmic domain is sufficient for talin binding. We have identified a short region within talin's amino-terminal 435 amino acids capable of binding to layilin in vitro. This region overlaps a binding site for focal adhesion kinase.

Amino Acid Sequence↗
PubMed2003

Tyrosine phosphorylation of type Igamma phosphatidylinositol phosphate kinase by Src regulates an integrin-talin switch.

Engagement of integrin receptors with the extracellular matrix induces the formation of focal adhesions (FAs). Dynamic regulation of FAs is necessary for cells to polarize and migrate. Key interactions between FA scaffolding and signaling proteins are dependent on tyrosine phosphorylation. However, the precise role of tyrosine phosphorylation in FA development and maturation is poorly defined. Here, we show that phosphorylation of type Igamma phosphatidylinositol phosphate kinase (PIPKIgamma661) on tyrosine 644 (Y644) is critical for its interaction with talin, and consequently, localization to FAs. PIPKIgamma661 is specifically phosphorylated on Y644 by Src. Phosphorylation is regulated by focal adhesion kinase, which enhances the association between PIPKIgamma661 and Src. The phosphorylation of Y644 results in an approximately 15-fold increase in binding affinity to the talin head domain and blocks beta-integrin binding to talin. This defines a novel phosphotyrosine-binding site on the talin F3 domain and a "molecular switch" for talin binding between PIPKIgamma661 and beta-integrin that may regulate dynamic FA turnover.

Amino Acid Sequence↗
PubMed2004

A role for talin in presynaptic function.

Talin, an adaptor between integrin and the actin cytoskeleton at sites of cell adhesion, was recently found to be present at neuronal synapses, where its function remains unknown. Talin interacts with phosphatidylinositol-(4)-phosphate 5-kinase type Igamma, the major phosphatidylinositol-(4,5)-bisphosphate [PI(4,5)P(2)]-synthesizing enzyme in brain. To gain insight into the synaptic role of talin, we microinjected into the large lamprey axons reagents that compete the talin-PIP kinase interaction and then examined their effects on synaptic structure. A dramatic decrease of synaptic actin and an impairment of clathrin-mediated synaptic vesicle endocytosis were observed. The endocytic defect included an accumulation of clathrin-coated pits with wide necks, as previously observed after perturbing actin at these synapses. Thus, the interaction of PIP kinase with talin in presynaptic compartments provides a mechanism to coordinate PI(4,5)P(2) synthesis, actin dynamics, and endocytosis, and further supports a functional link between actin and clathrin-mediated endocytosis.

Actins↗
PubMed1990

Colocalization of F-actin and talin during Fc receptor-mediated phagocytosis in mouse macrophages.

We have studied the distribution of talin in J774 cells and mouse peritoneal macrophages undergoing Fc receptor-mediated phagocytosis. At early stages of phagocytosis, talin accumulates in the cells' cortical cytoplasm adjacent to the forming phagosome and extends into pseudopods that are encircling the particle. Talin colocalizes with F-actin at these sites. After particle ingestion is completed, F-actin and talin are no longer concentrated adjacent to phagosomes. Thus, talin and F-actin undergo dynamic and coordinate changes in their cytoplasmic location during Fc receptor-mediated phagocytosis.

Actins↗
PubMed1995

Localization of vinculin and talin at perineurial cells of human sural nerve.

Immunolocalization of spectrin, vinculin, talin, desmin and titin was investigated in human sural nerve. No binding for spectrin and titin was seen in any structure of the nerve. Antibody against desmin immunostained sporadic epineurial vessels only. Endoneurial and epineurial vessels were intensely positive for vinculin and talin. We found expression of vinculin and talin at the perineurial cells, using immunocytochemistry and gold immunoelectron microscopy. Since vinculin and talin are known to be involved in cell-cell and cell-extracellular matrix transmembrane connections, we propose that they, possibly together with other cytoskeletal proteins, may be implicated in the permeability barrier property of the perineurium. In pathological conditions, perineurium plays an as yet unknown role. Future studies are needed to investigate expression of vinculin and talin in neuropathies.

Adolescent↗
PubMed1986

Spatial and temporal relationships between vinculin and talin in the developing chicken gizzard smooth muscle.

The spatiotemporal relationships between vinculin and talin in developing chicken gizzard smooth muscle were investigated. Immunofluorescence and immunoelectron-microscopic labeling revealed that both proteins are associated with membrane-bound dense plaques in muscle cells; however, the most intense labeling for vinculin was located rather closer to the membrane than that for talin. The localization of vinculin and talin in embryonic chicken gizzards indicated that both are primarily cytoplasmic during the first 2 embryonic weeks. Only around days 16-18 does talin apparently become associated with the plasma membrane, this being concomitant with the appearance of distinct myofilament-bound dense plaques. Vinculin, on the other hand, remains primarily cytoplasmic and appears in the plaques only 1-3 days after hatching. It is thus proposed that the interactions of the dense plaque with myofilaments or with the membrane do not depend on the presence of vinculin in the plaque. Electrophoretic analyses indicated that, during development, there is no major change in the differential expression of specific vinculin isoforms. Quantitative immunoblotting analysis indicated that the vinculin content (relative to total extracted protein) is virtually constant during the last week of embryonic life. However, within 3 days of hatching, the vinculin concentration increases remarkably to over twice the embryonic level, and then slowly increases until it reaches the adult levels, which are three to four times higher than the embryonic level. The concentration of metavinculin (a 160-Kd vinculin-related protein) showed only a limited increase after hatching. We discuss the possible roles of vinculin and talin in the assembly of membrane-bound dense plaques during the different phases of smooth-muscle development.

Animals↗
PubMed2003

Calpain mediates progressive plasma membrane permeability and proteolysis of cytoskeleton-associated paxillin, talin, and vinculin during renal cell death.

The goal of the present study was to determine the role of calpain in changes in plasma membrane permeability and cytoskeleton-associated paxillin, vinculin, talin, and alpha-actinin levels during acute renal cell death. The mitochondrial inhibitor antimycin A or hypoxia produced graded plasma membrane permeability in renal proximal tubules (RPTs), first allowing propidium iodide (PI, molecular mass 668 Da) influx and then lactate dehydrogenase (LDH, molecular mass 130 kDa) release. Cytoskeleton-associated paxillin levels decreased concomitantly with PI influx and before LDH release, whereas cytoskeleton-associated talin and vinculin levels decreased concomitantly with LDH release. Cytoskeleton-associated alpha-actinin levels did not change during antimycin A exposure or hypoxia. Purified micro-calpain cleaved paxillin, talin, vinculin, but not alpha-actinin. The dissimilar calpain inhibitors 3-(4-iodophenyl)-2-mercapto-(Z)-2-propenoic acid (PD150606) or chloroacetic acid N'-[6,7-dichloro-4-phenyl)-3-oxo-3,4-dihydroquinoxalin-2-yl] hydrazide (SJA7029) preserved cytoskeleton-associated paxillin, talin, and vinculin levels and prevented PI influx and LDH release in antimycin A-exposed or hypoxic RPTs. These results suggest that calpain mediates increased plasma membrane permeability and hydrolysis of cytoskeleton-associated paxillin, vinculin, and talin during renal cell death.

Acrylates↗
PubMed1995

Phosphorylation of dense-plaque proteins talin and paxillin during tracheal smooth muscle contraction.

Reorganization of cytoskeletal-membrane interactions during contractile stimulation may contribute to the regulation of airway smooth muscle contraction. We investigated the effect of contractile stimulation on the phosphorylation of the actin-membrane attachment proteins talin, vinculin, and paxillin. Stimulation of 32P-labeled canine tracheal smooth muscle strips with acetylcholine (ACh; 10(-3) M) resulted in a rapid 2.6-fold increase in phosphorylation of serine and/or threonine residues, compared with resting levels of 0.22 mol PO4(3-)/mol talin. After stimulation with ACh, phosphorylation of tyrosine residues on paxillin increased approximately threefold. Two-dimensional phosphopeptide mapping of in vivo labeled talin and paxillin indicated phosphorylation on a limited number of sites. Vinculin phosphorylation was undetectable in either resting or ACh-stimulated muscle. We conclude that phosphorylation of talin and paxillin occurs during ACh-stimulated contraction of tracheal smooth muscle and that distinct signaling pathways activate a serine/threonine kinase that phosphorylates talin and a tyrosine kinase that phosphorylates paxillin. The pharmacological activation of airway smooth muscle cells might involve the anchoring of contractile filaments to the membrane.

Acetylcholine↗
PubMed2006

Culture of human skeletal muscle myoblasts: timing appearance and localization of dystrophin-glycoprotein complex and vinculin-talin-integrin complex.

The dystrophin-glycoprotein complex together with the vinculin-talin-integrin complex plays an important role in muscle function; in fact the mutations of their elements lead to diverse forms of muscular dystrophies. The relationship between the elements of dystrophin-glycoprotein complex and vinculin-talin-integrin and the time course of their formation are still not known in detail. In order to better understand this relationship we studied their expression during development in normal human skeletal muscle culture. Using a standardized muscle cell culture procedure, this study was performed to analyze the timing, appearance and the localization of some proteins of the dystrophin-glycoprotein complex and vinculin-talin-integrin complex during cellular proliferation (myoblast) and differentiation (4, 7, 15 and 21 days). The indirect immunofluorescence technique was used and cells were examined using a Meta Zeiss LSM510 confocal laser scanning inverted microscope. We examined the progressive appearance of the following proteins: alpha, beta, gamma, delta-sarcoglycans, beta-dystroglycan, dystrophin, talin, vinculin and integrin isoform alpha7/beta1. Immunofluorescence of these proteins, in satellite cells entering myogenic differentiation, revealed different patterns of localization depending on the time of culture. We showed that nondifferentiated cultures of human myoblasts expressed a perinuclear distribution of all proteins tested. During myoblast differentiation into myotubes (4 days) immunofluorescence gradually increased and was located in the whole cytoplasm. Subsequently, at day 7, a strong and homogeneous cytoplasmic labelling of all proteins was seen. At 15 days the distribution of the proteins was on the membrane. At this time some myotubes displayed a significant degree of precostameric banding pattern. As fusion proceeded at 21 days, the cytodistribution progressively changed and appeared along fibrillar longitudinal structures, and myotubes showed a clear periodic distribution (costameres). In conclusion, in normal human muscle cultures DGC and vinculin-talin-integrin proteins are first localized in the perinuclear region, then they diffuse in the cytoplasm and finally form at the plasma membrane into typical rib-like structures that are sarcolemma-associated.

Adult↗
PubMedDate not supplied

Activation of calpain I and hydrolysis of calpain substrates (actin-binding protein, glycoprotein Ib, and talin) are not a function of thrombin-induced platelet aggregation.

Calcium-activated neutral proteinase (calpain) has been shown to cleave proteins involved in the maintenance of cell structure. In human platelets, substrates of calpain include glycoprotein Ib (GPIb), actin-binding protein (ABP), and talin. GPIb-ABP complexes can be isolated in detergent extracts and are thought to represent membrane-cytoskeleton attachment sites. It has been hypothesized that the hydrolysis of GPIb-ABP by calpain is regulated by the extent of binding of this proteinase to the plasma membrane-cytoskeleton interface with platelet activation. Recently, another calpain substrate (talin) has been shown to redistribute from the cytoplasm to the plasma membrane-cytoskeleton interface as the result of thrombin stimulation. To investigate the intracellular distribution of calpain I, we employed the monoclonal antibody B27D8, specific for the heavy chain (catalytic subunit) of calpain I. Indirect immunofluorescent staining of resting human platelets revealed undetectable surface antigen. Permeabilization with Triton X-100, however, revealed a diffuse intracellular antigen consistent with a cytosolic distribution. To determine whether this antigen distribution reflected the proenzyme or the activated form of calpain I and to assess the degree of hydrolysis of ABP, GPIb, and talin, we employed B27D8 and murine monoclonal antibodies against ABP (1B3 and 3D1), GPIb (LJIb10), and rabbit polyclonal antibodies against talin (A2 and B11) in a quantitative immunotransblot assay. Examination of resting platelets revealed that calpain I existed as the 85-kd proenzyme form and that ABP, GPIb, and talin existed in their native intact forms. When platelets were aggregated with thrombin, autoproteolysis of calpain I occurred within the 30 seconds required to completely solubilize platelet aggregates in sodium dodecyl sulfate-containing buffer and not as a direct result of thrombin-induced activation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

The role of phosphorylation and limited proteolytic cleavage of talin and vinculin in the disruption of focal adhesion integrity.

Chemical agents which activate specific kinases were employed to disrupt the stress fiber and focal adhesion organization of cells spread on a substratum. The phorbol ester 12-O-tetradecanoylphorbol-13-acetate, an activator of protein kinase C, promoted a rapid loss of stress fibers and focal adhesions from African green monkey kidney (BSC-1) cells. This was paralleled by an increase in the level of talin phosphorylation suggesting that this may play a role in the removal of talin from focal adhesions. Similar morphological changes were produced in the rat embryo fibroblast line (REF 52) by dibutyryl-cAMP, which stimulates protein kinase A. In contrast, however, the phosphorylation of talin was reduced in REF 52 cells when treated with dibutyryl cAMP. In untreated cells we found that the levels of vinculin phosphorylation were very low relative to the levels of talin phosphorylation and did not change following drug treatment in either cell line. Although limited proteolytic cleavage of cytoskeletal proteins represents a potential mechanism for focal adhesion disruption, we observed no proteolysis of talin or vinculin in response to either drug treatment.

Animals↗
PubMed1995

Abnormal subcellular distribution of myosin and talin in Wistar Furth rat platelets.

The roles of most cytoskeletal proteins in platelet formation and function remain largely undefined. We earlier detected megakaryocyte membrane blebbing and a unique antigenic determinant associated with a missense mutation in the cytoskeletal protein, talin, in an animal model of hereditary macrothrombocytopenia, the Wistar Furth (WF) rat, which led us to examine the distribution of talin and other cytoskeletal proteins in resting normal and WF rat platelets. In contrast to the conclusions of an earlier ultrastructural analysis, our biochemical and ultrastructural immunogold studies indicate a significant membrane-association of talin in both resting normal and WF rat platelets as found earlier for rat megakaryocytes. Talin was associated with plasma membranes, membranes of the surface-connected canalicular system, and with alpha-granule membranes of both normal and WF rat platelets, but as in WF megakaryocytes, talin was absent from the large membrane complexes of WF platelets. An even more striking difference was seen in the distribution of myosin in subcellular fractions of normal and WF rat platelets separated in density gradients, in which the proportion of myosin in the least dense WF rat platelet membrane fraction was one half that in the same normal platelet fraction. This difference was balanced by a fourfold increase in myosin in the most dense WF rat subcellular fraction, which is highly enriched for alpha-granules. These results support our hypothesis that the platelet abnormalities of the WF rat are related to defects in the megakaryocyte-platelet cytoskeleton.

Animals↗
PubMed1997

Vinculin and talin: kinetics of entry and exit from the cytoskeletal pool.

Vinculin and talin, two major components of focal contacts, exist in cytosolic and cytoskeletal pools. The kinetics of entry and exit of the two proteins between the two pools were investigated in normal and transformed cells. In cultured chick embryo fibroblasts, a fraction (2-5%) of the newly synthesized vinculin and talin reached maximal levels in the cytoskeleton in 30-45 min. Both proteins had 2-3 times shorter half-lives in the cytoskeletal pool (t1/2 = 6-7 h) than in the cytosolic pool (t1/2 = 14-15 h), which suggests that the incorporation of cytosolic vinculin and talin into the cytoskeleton does not involve a simple equilibrium between the two pools. However, after disruption of cell-to-substrate adhesion by trypsinization, an equilibrium in the incorporation between the two pools was transiently established, resulting in the use of the preexisting cytosolic pools of the two proteins during re-establishment of cell-to-matrix contacts. Viral transformation did not cause a significant change in the incorporation rates into the cytoskeleton. However, it decreased the half-lives of both proteins in the cytoskeletal pool (t1/2 = approximately 4 h) and in the cytosolic pool (t1/2 = 9-10 h). The increased turn-over rates of vinculin and talin in the cytoskeletal pool in transformed cells may contribute to the enhanced motility of transformed cells.

Animals↗
PubMed1997

Monoclonal antibodies recognizing the N- and C-terminal regions of talin disrupt actin stress fibers when microinjected into human fibroblasts.

We have characterized a panel of 6 monoclonal antibodies raised against human platelet talin by Western blotting, immune precipitation, and immunofluorescence, and shown that antibodies TA205 and TD77 disrupt actin stress fibers and focal adhesions, and inhibit cell motility when microinjected into human fibroblasts. Using a series of chick talin fusion proteins spanning the entire length of the molecule, we have mapped the epitopes recognized by these antibodies to the conserved N- and C-terminal regions of the protein. TA205 bound to an epitope contained within residues 139-433, a region which overlaps an F-actin binding site, and which shows homology with the ezrin/radixin/moesin family of cytoskeletal proteins. The epitope recognized by TD77 was located within the C-terminal region of the protein (residues 2269-2541) which also contains an F-actin binding site homologous to that in the yeast actin-binding protein SIa2p. To investigate the possibility that TD77 disrupts actin stress fibers by binding directly to the C-terminal actin binding site, additional talin fusion proteins were generated and analyzed for TD77 and actin binding. Fusion proteins containing residues 2269-2541, 2304-2541, and 2304-2463 all cosedimented with F-actin, whereas TD77 did not recognize the latter fusion protein. These results show that the C-terminal actin-binding site is distinct from the region recognized by the anti-functional antibody TD77, raising the possibility that it binds to a novel functionally important ligand-binding site in the talin molecule.

Actins↗
PubMed2000

Disruption of the talin gene arrests mouse development at the gastrulation stage.

Studies on cultured cells show that the cytoskeletal protein talin plays a key role in cell spreading and the assembly of cell-extracellular matrix junctions. To examine the role of talin in vivo, we have generated mice with a targeted disruption of the talin gene. Heterozygotes are normal, but no surviving homozygous mutant animals were obtained, proving that talin is required for embryogenesis. Mutant embryos develop normally to the blastocyst stage and implant, but there is a gross disorganization of the embryos at gastrulation (6.5-7.5 days post coitum), and they die around 8.5-9.5 days post coitum. The embryonic ectoderm is reduced in size, with fewer cells, and is incompletely organised compared with wild-type embryos. The mutant embryos show disorganised extraembryonic tissues, and the ectoplacental and excocoelomic cavities are not formed. This seems to be because embryonic mesoderm accumulates as a mass on the posterior side of the embryos and fails to migrate to extraembryonic regions, although mesodermal cells are evident in the embryo proper. Spreading of trophoblast cells derived from cultured mutant blastocysts on fibronectin and laminin is also considerably reduced. Therefore, the fundamental deficit in these embryos seems to be a failure of cell migration at gastrulation.

Animals↗
PubMed1995

Platelet talin is phosphorylated by calyculin A.

Calyculin A and okadaic acid, potent and cell permeable inhibitors of type 1 and type 2A protein phosphatases, inhibit platelet aggregation and secretion. However, the relationship between phosphatase inhibition and inhibition of platelet function is not well understood. We found that in unstimulated platelets, talin (P235) was phosphorylated at threonine residues by calyculin A. Furthermore, the extent of talin phosphorylation by calyculin A was closely correlated with its inhibition of thrombin-induced platelet aggregation. Since the binding of talin to platelet glycoprotein IIb/IIIa complex has been shown to be affected by its phosphorylation, these results suggest that type 1 and/or type 2A protein phosphatases may play a role in the regulation of membrane-cytoskeleton interaction through dephosphorylation of talin.

Alkalies↗
PubMed1995

Effects of microcystin-LR on actin and the actin-associated proteins alpha-actinin and talin in hepatocytes.

Microcystin-LR (MCLR) is a commonly encountered blue-green algal hepatotoxin and a known inhibitor of cellular protein phosphatase types 1 and 2A. The toxin causes alterations in, and redistribution of, intermediate filaments, microtubules, and actin microfilaments (MFs) in affected cells. In this study, the effect of MCLR on the sequence of alterations in MFs and actin-associated proteins (AAPs) of isolated hepatocytes was examined in an effort to determine whether morphologic changes induced in MFs by microcystins are a result of prior dislocation of AAPs. We studied the effects of MCLR exposure on alpha-actinin and talin, two AAPs that play a role in the orientation of the MFs. Primary hepatocytes were incubated with 10 microns MCLR for 0-64 min. The distribution of actin, alpha-actinin, and talin were examined using fluorescence microscopy. MCLR induced similar changes in the distribution of actin and the AAPs. Actin filament redistribution was first observed after 12 min of MCLR exposure, and was characterized by detachment of MFs from the cell periphery, followed by condensation at distinct focal points and progressive collapse into the interior of affected cells. Changes in alpha-actinin and talin distribution were first observed after 20 min of toxin exposure. The AAPs appeared to detach from focal contacts on the cytoplasmic surface of the plasma membrane, condense into cytoplasmic aggregates, and ultimately collapse into a juxtanuclear bundle. The results of this study indicate that, in hepatocytes exposed to MCLR, the collapse of actin MFs occurs prior to the dislocation of alpha-actinin and talin. Changes in these actin associated proteins are not likely to account for the initial changes in actin MFs.

Actin Cytoskeleton↗