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At least 1,693 records · Page 94Linked to original sources
PubMed2001

Gelsolin functions as a metastasis suppressor in B16-BL6 mouse melanoma cells and requirement of the carboxyl-terminus for its effect.

Gelsolin, an actin-binding protein, is implicated as a critical regulator in cell motility. In addition, we have reported that cellular levels of gelsolin are decreased in various tumor cells, and overexpression of gelsolin by gene transfer suppresses tumorigenicity. We sought to assess the effects of gelsolin overexpression on metastasis and to determine the importance of a carboxyl-terminus that confers Ca(2+) dependency on gelsolin for effects of its overexpression. Expression vectors with cDNA encoding either full-length wild-type or His321 mutant form, isolated from a flat revertant of Ras-transformed cells and a carboxyl-terminal truncate, C-del of gelsolin, were transfected into a highly metastatic murine melanoma cell line, B16-BL6. Expression of introduced cDNA in transfectants was confirmed using Western blotting, 2-dimensional gel electrophoresis and reverse transcription-polymerase chain reaction (RT-PCR). We characterized phenotypes of transfectants, such as growth rate, colony formation in soft agar, cell motility and metastasis formation in vivo. Transfectants expressing the wild-type, His321 mutant and C-del gelsolin exhibited reduced growth ability in soft agar. Although expression of integrin beta1 or alpha4 on the cell surface of transfectants was not changed, wild-type and His321 mutant gelsolin, except for C-del gelsolin, exhibited retardation of cell spreading, reduced chemotatic migration to fibronectin and suppressed lung colonization in spontaneous metastasis assay. Gelsolin may function as a metastasis suppressor as well as a tumor suppressor gene. The carboxyl-terminus of gelsolin is important for retardation of cell spreading, reduced chemotasis and metastasis suppression.

Animals↗
PubMed1993

Altered glycosylation of beta 1 integrins associated with reduced adhesiveness to fibronectin and laminin.

The carbohydrate structures of the beta 1 integrins obtained from a mouse metastatic melanoma B16 F1 and its weakly metastatic wheat-germ agglutinin-resistant mutant Wa4-b1 were studied comparatively. The results indicated that the integrins from both cells contain high mannose-type and bi-, tri- and tetra-antennary complex-type sugar chains. No significant difference was found in the outer chain branching between both integrins, but sialylation of the sugar chains of the mutant's integrin was markedly decreased and almost all the outer chain moieties of tri- and tetra-antennary oligosaccharides of the mutant's integrin were fucosylated, resulting in the formation of X-antigenic determinants, Gal beta 1-->4 (Fuc alpha 1-->3) GlcNAc. In contrast, the integrin from parental cell contained no X-antigenic determinant. These structural differences found in the integrin are thought to account for the reduction in the metastatic potential of the mutant which also shows reduced adhesion to fibronectin and laminin as compared with the parental cell.

Animals↗
PubMed1995

Glycosylation of beta-1 integrins in B16-F10 mouse melanoma cells as determinant of differential binding and acquisition of biological activity.

Studying B16-F10 cells we could identify beta-1 integrins as laminin, fibronectin and collagen receptors. Gradient ionic strength elution analysis of affinity chromatography showed differential interactions between laminin-binding beta-1 integrins (two beta-1 polypeptides of 105 and 120 kDa) and fibronectin and collagen-binding beta-1 integrins (elution of one major beta-1 polypeptide of 120 kDa) and their respective ligands. To evaluate this diversity we submitted B16-F10 extracts to IEF and SDS-PAGE and found that one beta-1 integrin formed acidic and larger isoforms, while another formed basic and smaller isoforms. To study this difference we also submitted material eluted from WGA-Sepharose columns to IEF but now only the acidic beta-1 isoform was found. Extracts of B16-F10 treated with neuraminidase showed only the basic beta-1 isoform, suggesting that terminal sialic acid residues may be responsible for this acidic pattern, an interpretation supported by the fact that MAA (Maackia ammurensis agglutinin) reacts only with the acidic isoform. Differential glycosylation of beta-1 integrin isoforms in B16-F10 was also demonstrated since the smaller laminin-binding beta-1 integrin isoform reacted only with GNA (Galanthus nivalis agglutinin), whereas the mature larger form reacted with DSA (Datura stramonium agglutinin) and MAA; thus this heterogeneity of beta-1 chains is essentially due to variable glycosylation. Autoradiography and immunoblotting analysis of material separated by 2-dimensional electrophoresis show that only the processed forms of beta-1 integrins are expressed at the cell surface.

Animals↗
PubMed2002

Initial interaction of U2OS cells with noncoated and calcium phosphate coated titanium substrates.

From previous studies, we know that calcium phosphate (CaP) coated implants stimulate bone formation compared to uncoated implants. Nevertheless, the mechanism by which substrate surface characteristics affect cell function is unclear. In this study, we examined the initial interaction (30 min to 24 h) of U2OS cells with titanium substrates with or without a CaP coating. The effect of substrate roughness was also studied. When cell attachment was studied, we found that cells attached more readily to rough than to smooth surfaces. Also, more cells attached to the uncoated than to the CaP coated surface. After 24 h, cell numbers were similar for all substrate surfaces. Further, cells spread to a larger area on noncoated titanium than on the CaP coated substrates. At 24 h, the sequence of cell size was smooth titanium > rough titanium > CaP coated titanium. Shape measurements showed differences in cell shape between the cells on the different materials only at 7 h, not at different culture times. Cells expressed alpha2, alpha3, alpha5, alpha6, alphav, and beta1 subunits. Expression of alpha1, alpha4, alphavbeta3, beta3, beta4, and beta7 was extremely low or was not found. The beta1 integrin expression was higher on the coated than on the noncoated titanium at 3 h, but not on the other studied times. Expression of alpha2, alpha5, alpha6, and alphav expression was found to be upregulated at 24 h compared to earlier culture times on coated titanium, but not on uncoated titanium substrates. From this we conclude that the surface characteristics of a material (roughness and composition) can affect the initial interaction of cells with the material.

Calcium Phosphates↗
PubMed2005

Osteoblast response to thermally oxidized Ti6Al4V alloy.

We have recently reported that thermal oxidation treatments of Ti6Al4V at 500 degrees and 700 degrees C for 1 h result in the formation of an outer "ceramic" layer of rutile that do not decrease the high in vitro corrosion resistance of the alloy. In the present work, surface roughness was measured and found marginally increased as a consequence of oxidation of the alloy at 700 degrees C, but not at 500 degrees C. We have evaluated the biocompatibility of the oxidized surfaces, by assessing cell adhesion, proliferation, and differentiation of primary cultures of human osteoblastic cells. Compared with polished alloy, both thermal treatments increased osteoblast adhesion measured as cell attachment, beta1 integrin and FAK-Y397 expression, as well as cytoskeletal reorganization. Compared with treatment at 500 degrees C, thermal oxidation at 700 degrees C enhanced cell adhesion. Treatment at 700 degrees C transiently impaired cell proliferation and viability, which were not altered in alloys oxidized at 500 degrees C. Several markers of osteoblastic differentiation such as procollagen I peptide, alkaline phosphatase, osteocalcin, and mineralized nodule formation were found either unaffected or differentially increased by alloys treated either at 500 degrees or 700 degrees C. In addition, thermal oxidation at 700 degrees C also increased osteoprotegerin secretion. Taken together, our results indicate that thermal oxidation treatments at 500 degrees or 700 degrees C for 1 h improve the in vitro biocompatibility of Ti6Al4V.

Actins↗
PubMed2006

Cartilage tissue engineering using human auricular chondrocytes embedded in different hydrogel materials.

To seek a suitable scaffold for cartilage tissue engineering, we compared various hydrogel materials originating from animals, plants, or synthetic peptides. Human auricular chondrocytes were embedded in atelopeptide collagen, alginate, or PuraMatrix, all of which are or will soon be clinically available. The chondrocytes in the atelopeptide collagen proliferated well, while the others showed no proliferation. A high-cell density culture within each hydrogel enhanced the expression of collagen type II mRNA, when compared with that without hydrogel. By stimulation with insulin and BMP-2, collagen type II and glycosaminoglycan were significantly accumulated within all hydrogels. Chondrocytes in the atelopeptide collagen showed high expression of beta1 integrin, seemingly promoting cell-matrix signaling. The N-cadherin expression was inhibited in the alginate, implying that decrease in cell-to-cell contacts may maintain chondrocyte activity. The matrix synthesis in PuraMatrix was less than that in others, while its Young's modulus was the lowest, suggesting a weakness in gelling ability and storage of cells and matrices. Considering biological effects and clinical availability, atelopeptide collagen may be accessible for clinical use. However, because synthetic peptides can control the risk of disease transmission and immunoreactivities, some improvement in gelling ability would provide a more useful hydrogel for ideal cartilage regeneration.

Atrial Appendage↗
PubMed2006

Isolation of epithelial stem cells from dermis by a three-dimensional culture system.

Skin is a representative self-renewing tissue containing stem cells. Although many attempts have been made to define and isolate skin-derived stem cells, establishment of a simple and reliable isolation procedure remains a goal to be achieved. Here, we report the isolation of cells having stem cell properties from mouse embryonic skin using a simple selection method based on an assumption that stem cells may grow in an anchorage-independent manner. We inoculated single cell suspensions prepared from mouse embryonic dermis into a temperature-sensitive gel and propagated the resulting colonies in a monolayer culture. The cells named dermis-derived epithelial progenitor-1 (DEEP) showed epithelial morphology and grew rapidly to a more than 200 population doubling level over a period of 250 days. When the cells were kept confluent, they spontaneously formed spheroids and continuously grew even in spheroids. Immunostaining revealed that all of the clones were positive for the expression of cytokeratin-8, -18, -19, and E-cadherin and negative for the expression of cytokeratin-1, -5, -6, -14, -20, vimentin, nestin, a ckit. Furthermore, they expressed epithelial stem cell markers such as p63, integrin beta1, and S100A6. On exposure to TGFbeta in culture, some of DEEP-1 cells expressed alpha-smooth muscle actin. When the cells were transplanted into various organs of adult SCID mice, a part of the inoculated cell population acquired neural, hepatic, and renal cell properties. These results indicate that the cells we isolated were of epithelial stem cell origin and that our new approach is useful for isolation of multipotent stem cells from skin tissues.

Animals↗
PubMed1992

Beta 1 integrins isolated from embryonic chicken fibroblasts bind to monomers and polymers of type I collagen.

The avian integrin beta 1 subfamily consists of multiple alpha-beta subunit heterodimers. We employed two different physical states of type I collagen, monomers and fibrils, in the isolation and characterization of avian collagen integrins. Affinity chromatography showed that three integrins, tentatively designated alpha 155 beta 1 (band 1), alpha 5a beta 1, and alpha 3 beta 1 (band 2), bind fibrillar and monomeric collagen under physiological ionic conditions and require divalent cations for binding activity. Sodium chloride gradients (0-0.5 M) were used to assess the functional ability of the integrins to remain bound to the two forms of type I collagen. The results show that integrins elute from the two forms of collagen with distinct fractionation profiles. One integrin, alpha 155 beta 1, binds fibrillar collagen with relatively higher affinity than the other beta 1 receptors. This same avian integrin, alpha 155 beta 1, is immunoreactive with an antiserum (Hynes et al., 1989) raised against a peptide that corresponds to the entire alpha 5 cytoplasmic domain, and coincidently, part of the alpha 6 cytoplasmic domain (de Curtis et al., 1991). Cell biological studies employing double immunofluorescence show that integrins recognized by this antiserum co-localize with extracellular deposits of type I collagen.

Animals↗
PubMed1995

In vitro structural and functional relationships between preosteoclastic and bone endothelial cells: a juxtacrine model for migration and adhesion of osteoclast precursors.

The role of vascularization in the process of bone resorption has not been clarified. The interactions between vascular endothelium and osteoclast progenitors were analyzed using clonal cell lines of bone-derived endothelial and preosteoclastic cells. Insulin-like growth factor I is a major chemotactic stimulator of preosteoclastic cell migration mediated by bone endothelial cells. Osteoclast precursors rapidly adhered to bone endothelial monolayers. This phenomenon appeared to be cell-specific and mediated through the binding of vitronectin and fibronectin receptors to fibronectin. In addition, direct contact with bone endothelial cells induced osteoclast progenitors to differentiate into more mature elements, with the tendency to cluster together to form large multinucleated cells. These findings demonstrated specific in vitro interactions between bone endothelial cells and osteoclast progenitors, offering a new model for understanding the molecular mechanisms which direct the processes of osteoclast recruitment and ontogeny.

Animals↗
PubMed2001

Phosphorylation of focal adhesion kinase (pp125(FAK)) is increased in human keratinocytes induced to migrate by extracellular matrices.

During the healing process of skin wounds, human keratinocytes migrate across a provisional matrix of the wound bed. The mechanisms by which keratinocytes migrate on connective tissue are not known. In this study, we examined the role of focal adhesion kinase (FAK), an 125 kDa protein that co-localizes with focal adhesions in cells plated on extracellular matrix. We induced human keratinocytes into various states of migration by plating them on extracellular matrices that minimally, moderately, or strongly induce cellular migration, and then examined the expression of FAK at the protein level and its degree of tyrosine phosphorylation using Western immunoblotting and immunoprecipitation. In highly migratory human keratinocytes, we found that three proteins were predominantly tyrosine phosphorylated, one of them being FAK. Tyrosine phosphorylation of FAK tightly correlated with the level of cellular motility but not cell attachment to the matrix. Time course experiments demonstrated that in highly motile keratinocytes, tyrosine phosphorylation of FAK peaked at 12 h, the time when maximal migration on the matrix ensues. In contrast to FAK, the beta1 integrin subunit of human keratinocytes that configures with the alpha2, alpha3, and alpha5 integrin subunits to form integrin receptors for matrix, did not display tyrosine phosphorylation linked to motility. Using anti-sense oligonucleotides to FAK, we demonstrate that FAK is required for human keratinocyte migration, but not for focal adhesion formation.

Cell Movement↗
PubMed2005

Interactions among IQGAP1, Cdc42, and the cadherin/catenin protein complex regulate Sertoli-germ cell adherens junction dynamics in the testis.

The movement of developing germ cells across the seminiferous epithelium during spermatogenesis involves extensive adherens junction (AJ) restructuring between Sertoli cells, as well as between Sertoli and germ cells. In this report, we show that the intricate interactions between Cdc42 (a Rho family protein of Mr approximately 23 kDa originally identified in membranes of human platelets and placenta, and is the homolog of CDC42Sc, which is known to regulate of bud-site assembly in Saccharomyces cerevisiae) and its effector, IQ motif containing GTPase activating protein (IQGAP1, Mr approximately 189 kDa, it is also an actin-binding protein known to interact with Cdc42 and Rac1 GTPases), regulate Sertoli-germ cell, but not Sertoli-Sertoli cell, AJ dynamics. Using testis lysates for immunoprecipitation (IP), IQGAP1 was shown to associate with E-cadherin, N-cadherin, and beta-catenin (but not beta1-integrin and nectin-2), as well as with actin and vimentin (but not alpha-tubulin). Moreover, IQGAP1 was found to localize to the periphery of both Sertoli and germ cells in the seminiferous epithelium, at sites of cell-cell contacts. Using fluorescent microscopy with dual fluorescent probes, IQGAP1 was found to co-localize, at least in part, with N-cadherin in the seminiferous epithelium consistent with their localization at the basal and apical ES. Using Sertoli-germ cell cocultures, it was demonstrated that AJ assembly associated with a transient induction of Cdc42 and IQGAP1, which was not found when Sertoli cells were cultured alone. Lastly, a shift in the interactions of Cdc42, IQGAP1, beta-catenin, and N-cadherin was detected in Sertoli-germ cell cocultures using an Ca2+-induced AJ disruption model, which was used to examine AJ disassembly and its reassembly. In the presence of Ca2+, IQGAP1 bound preferentially to Cdc42 rather than to beta-catenin. However, when Ca2+ was depleted from cocultures using EGTA, a Ca2+ chelating agent, IQGAP1 lost its affinity for Cdc42 and became tightly associated with beta-catenin, destabilizing cadherin-mediated AJs between Sertoli and germ cells. Yet this shift of protein-protein interaction was not detected in Sertoli cells cultured alone. These results illustrate that the interactions among IQGAP1, Cdc42, and beta-catenin are crucial to the regulation of Sertoli-germ cell, but not Sertoli-Sertoli cell, AJ dynamics in the seminiferous epithelium.

Adherens Junctions↗
PubMed2005

The class II phosphoinositide 3-kinase PI3K-C2beta regulates cell migration by a PtdIns3P dependent mechanism.

The biological and pathophysiological significance of class II phosphoinositide 3-kinase enzyme expression currently remains unclear. Using an in vitro scrape wound assay and time-lapse video microscopy, we demonstrate that cell motility is increased in cultures expressing recombinant PI3K-C2beta enzyme. In addition, overexpression of PI3K-C2beta transiently decreased cell adhesion, stimulated the formation of cytoplasmic processes, and decreased the rate of cell proliferation. Consistent with these observations, expression of PI3K-C2beta also decreased expression of alpha4 beta1 integrin subunits. Using asynchronous cultures, we show that endogenous PI3K-C2beta is present in lamellipodia of motile cells. When cells expressing recombinant PI3K-C2beta were plated onto fibronectin, cortical actin staining increased markedly and actin rich lamellipodia and filopodia became evident. Overexpression of a 2xFYVE(Hrs) domain fusion protein abolished this response demonstrating that the effect of PI3K-C2beta on the reorganization of actin filaments is dependent upon PtdIns3P. Finally, overexpression of PI3K-C2beta increased GTP loading of Cdc42. Our data demonstrates for the first time, that PI3K-C2beta plays a regulatory role in cell motility and that the mechanism by which it reorganizes the actin cytoskeleton is dependent upon PtdIns3P production.

Actins↗
PubMed2006

Effect of laminin-1 on intestinal cell differentiation involves inhibition of nuclear nucleolin.

Intestinal epithelial cells are characterized by continuous renewal and differentiation events, which may be influenced by the basement membrane, and in particular laminins, which are major components of this specialized extracellular matrix. The function and signaling pathways of laminins in these processes are still poorly documented. In this study, we investigated the possible role and the subcellular localization of nucleolin, a nuclear shuttling protein, in relation to differentiation of human intestinal epithelial Caco2/TC7 cells triggered by exogenous laminin-1. Immunofluorescence and Western blot analysis indicated that laminin-1 induced early differentiation of the cells concomitantly to a decrease in nuclear nucleolin and its a cell surface location. We also showed that both effects of laminin-1 on Caco2/TC7 cells--induction of the differentiation marker sucrase-isomaltase and redistribution of nucleolin--could be mediated by a beta1-integrin dependent cascade that implicated activation of the p38 MAPK pathway. In addition, knock-down of nucleolin expression by the small interfering RNA strategy mimicked the effect of laminin-1 as it resulted in the induction of cell polarization and differentiation. Thus, our study suggests that changes in the subcellular distribution and expression level of nucleolin play an important role in intestinal cell differentiation and relay the signaling pathway induced by laminin-1.

Base Sequence↗
PubMed2006

Junctional adhesion molecule-A regulates cell migration and resistance to shear stress.

Junctional adhesion molecule-A (JAM-A) is an adhesive protein expressed in endothelial cells, epithelial cells, platelets, and some leukocytes. JAM-A localizes to the tight junctions between contacting endothelial and epithelial cells, where it contributes to cell-cell adhesion and to the control of paracellular permeability. JAM-A also regulates cell motility, even though the quantitative biophysical features have not been characterized. In this study, we evaluated the role of JAM-A in the regulation of cell motility using JAM-A-expressing and JAM-A-deficient murine endothelial cells. We report that, in the absence of shear stress, JAM-A absence increases cell motility by increasing directional persistence but not cell speed. In addition, in the presence of shear stress, JAM-A absence increases protrusion extension in the direction of flow and increased downstream cellular displacement (while, conversely, decreasing upstream displacement). All these effects of JAM-A absence are mitigated by the microtubule-stabilizing compound taxol. A motility- and microtubule-related function, integrin-mediated adhesiveness, was only slightly reduced in JAM-A-deficient cells compared with JAM-A-expressing cells. However, overexpression of JAM-A in the JAM-A-deficient cells increased integrin adhesiveness to the same levels as those observed in taxol-treated JAM-A-deficient cells. Taken together, these data indicate that JAM-A regulates cell motility by cooperating with microtubule-stabilizing pathways.

Animals↗
PubMed2003

Farnesyl pyrophosphate promotes and is essential for the binding of RACK1 with beta-tubulin.

Receptors for activated C kinase (RACKs) are a group of protein kinase C (PKC) binding proteins that have been shown to be crucial in the translocation and subsequent functioning of PKC on activation. RACK1 isolated from BALB/3T3 cells transformed with S-ras(Q61K) exhibits receptor activity for PKCgamma as competent as that of RACK1 from BALB/3T3 cells without transformation. However, the ability of RACK1 from transformed cells to bind with beta-tubulin peptide specific for Taxol (PEPtaxol) is defective. Interestingly, when farnesyl pyrophosphate was added at the submicrogram level, the association between RACK1 and PEPtaxol was enhanced significantly in a dosage-dependent manner. A parallel finding for the enhanced effect of farnesyl pyrophosphate on tubulin binding was established with mice RACK1 expressed in vitro. On the other hand, geranylgeranyl pyrophosphate, and retinoic acid failed to modulate the binding between RACK1 and tubulin. The dissociation of RACK1 and tubulin was not effective at damaging the binding between RACK1 and membrane receptor integrin beta1 in transformed cells. These findings indicate that depletion of farnesyl pyrophosphate provides a mechanism to seal PKC signaling on the membrane with immobile RACK1 and to divert cells to aberrant growth, such as transformation.

3T3 Cells↗
PubMed1992

Regulation of T cell proliferation by anti-CD49d and anti-CD29 monoclonal antibodies.

The beta 1 integrin VLA-4 (alpha 4 beta 1, CD49d/CD29), which is expressed on a large subpopulation of peripheral blood T lymphocytes, functions as a receptor for the endothelial adhesion protein VCAM-1 and the extracellular matrix protein fibronectin. Previous studies showed that immobilized fibronectin enhanced anti-CD3 monoclonal antibody (mAb)-induced T cell proliferation through binding to the integrins VLA-4 and VLA-5 (alpha 5 beta 1, CD49e/CD29). We studied the ability of the anti-CD49d mAb L25 to potentiate proliferation. T cell proliferation was induced by subthreshold concentrations of anti-CD3 mAb (mAb OKT3) coimmobilized with mAb L25 but not with coimmobilized anti-CD29 (beta 1) mAb. Soluble anti-CD29 mAb inhibited the proliferation induced by coimmobilized mAb OKT3 and L25 but not proliferation induced by mAb OKT3 with PMA or coimmobilized anti-CD26 mAb.

Antigens, CD↗
PubMed1994

Priming of human monocyte superoxide production and arachidonic acid metabolism by adherence to collagen- and basement membrane-coated surfaces.

Monocytes (m phi s) come into intimate contact with basement membranes and extracellular matrix proteins as they extravasate from the blood to the interstitium or to sites of tissue injury. We examined the in vitro effects of m phi adherence to an endothelial cell-derived basement membrane or to purified extracellular matrix proteins on phorbol myristate acetate (PMA)-stimulated superoxide production and prostanoid secretion. Elutriation-purified human peripheral blood m phi s were adhered to tissue culture wells that were precoated with the following purified proteins: bovine serum albumin (BSA), collagen type I (COL I), collagen type IV (COL IV), fibronectin (FN), or laminin (LM). To model the provisional matrix at sites of tissue injury, m phi s were also adhered to wells coated with either denatured collagen type I or gelatin (GEL) or coated with basement membrane (BM) derived from endothelial cell monolayers. The m phi s were adhered to the protein-coated surfaces for 1 h at 37 degrees C in serum-free medium and washed to remove nonadherent cells, and the number of adherent m phi s was measured. Monolayers of m phi s were also incubated for an additional 18 h, at which time both adherence and cell spreading were measured. PMA-stimulated superoxide production by adherent m phi s was determined after 1 and 18 h of adherence to the protein-coated surfaces. PMA-stimulated release of two prostanoids, prostaglandin E2 (PGE2) and thromboxane B2 (TxB2) was measured after 18 h of m phi adherence to the surfaces. Following 18 h of adherence, PMA-stimulated superoxide anion secretion and secretion of PGE2 and TxB2 were augmented of primed by m phi s adherent to COL I, GEL, or BM. In contrast, no such priming effects were observed by m phi s adherent to COL IV, FN, or LM. The results suggest that adherence to basement membranes, collagen type I-containing surfaces in the interstitium, or denatured collagen at sites of tissue injury primes m phi respiratory burst and arachidonate metabolism to inflammatory agonists. Induction of priming events by substrate-specific adherence may be an important factor regulating host defense functions of m phi s in the extracellular matrix.

Antigens, CD↗
PubMed1995

Mechanisms of beta 1 integrin-dependent adherence of granulocytic HL60 to fibronectin.

We investigated the mechanism of beta 1 integrin-mediated adherence of stimulated granulocytic HL60 cells to fibronectin using a monoclonal antibody (15/7) that recognizes beta 1 integrins only when the receptors are active for ligand binding. Phorbol myristate acetate (PMA) stimulated expression of the 15/7 epitope on granulocytic HL60 by nearly fivefold but had an insignificant effect on the expression of the epitope on undifferentiated HL60 cells. These results paralleled the effect of PMA on HL60 and granulocytic HL60 adhesion to fibronectin, indicating that activation of beta 1 integrins is important for beta 1-mediated adherence of granulocytic HL60 cells to fibronectin. Agonists that stimulate alpha 5 beta 1-dependent human polymorphonuclear leukocyte (PMN) adhesion to fibronectin (C5a and PMA) also upregulated the 15/7 epitope on purified human PMNs. Although PMA rapidly induces increased levels of filamentous actin (F-actin) in granulocytic HL60 cells and a decrease in F-actin levels in undifferentiated HL60 cells, depolymerization of the actin cytoskeleton with cytochalasin B did not affect increased expression of the 15/7 epitope on granulocytic HL60 cells. Cytochalasin B did, however, inhibit granulocytic HL60 adherence to fibronectin by 50%, demonstrating that actin polymerization is important for optimal beta 1-dependent granulocytic adherence.

Actins↗