Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: HUMANGGP:009431 (fibronectin)
 32,104 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Treatment of murine erythroleukemia cells (MELC) attached to fibronectin-coated dishes with dimethyl sulfoxide causes the cells to become committed to the erythroid differentiation pathway. These cells mature extensively and acquire the characteristics of erythroid cells. The cells lose their cell-surface fibronectin receptors and accumulate red cell-specific membrane proteins, such as band 3, in amounts comparable to those in erythrocytes. Previous studies of MELC have shown that the presence of protein kinase C (PKC) is required for commitment to differentiation, but that the level of PKC activity declines progressively during maturation. In this study, we have established a role for PKC in the maturation of MELC committed to differentiation. Our results show that down-regulation of PKC by addition of phorbol 12-myristate 13-acetate (PMA) to committed MELC blocks subsequent maturation of the cells. Treatment of MELC with the PKC inhibitors H7 and sphingosine had similar effects. Down-regulation of PKC was assayed by measuring cytosolic PKC activity as well as by Western blotting using PKC antibodies. MELC maturation was monitored by loss of the cell-surface fibronectin receptor, release of cells from fibronectin plates, and accumulation of the band 3 anion transport protein. Immunoprecipitation of surface-labeled proteins by an anti-fibronectin receptor (integrin) antibody showed that PMA-treated cultures had more fibronectin receptor protein than untreated cultures 6 days post-induction. As a result, cultures of committed MELC treated with PMA remained attached to fibronectin-coated plates, whereas non-PMA-treated cells were released into the culture medium. Furthermore, PKC-depleted cells accumulated much smaller amounts of band 3 protein and band 3 mRNA than did non-PKC-depleted controls. Our results show that although PKC activity declines progressively during post-commitment maturation of MELC, its continued presence is critical for the process of cellular maturation.
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PMID:Maturation of murine erythroleukemia cells committed to differentiation requires protein kinase C. 138 58

The spectrum of serum proteins was evaluated in 46 horses affected with spontaneous laminitis and correlations between the severity of the disease and changes of the protein pattern were analyzed. The investigation was made in two groups; group A consisted of 21 horses of various breeds (warmblood, thoroughbred, standardbred) and group B of 25 ponys. Each group was subdivided according to the severity of the disease, using the OBEL-grade (OG) classification system. Serum proteins were separated by different one- and two-dimensional electrophoretic methods. Sera analysed by cellulose acetate electrophoresis showed a significant difference in the alpha 1-globulin fraction between OG II and OG IV affected horses. An increasing severity of the disease was correlated with a decrease of the alpha 1-globulins. The other protein fractions didn't show a uniform tendency. In group B there was a significant difference in the alpha 1-globulin fractions of OG II and OG III and in the beta 2-globulin fractions of OG I and OG II affected ponys. The acute phase proteins C3c, C4, Hp and fibronectin could be determined in a preliminary study in horse serum using the cross-reactivity of antibodies against the homologous human proteins.
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PMID:[Electrophoretic studies of serum protein fractions in horses with laminitis]. 142 23

Cell-substrate adhesion is crucial at various stages of development and for the maintenance of normal tissues. Little is known about the regulation of these adhesive interactions. To investigate the role of GTPases in the control of cell morphology and cell-substrate adhesion we have injected guanine nucleotide analogs into Xenopus XTC fibroblasts. Injection of GTP gamma S inhibited ruffling and increased spreading, suggesting an increase in adhesion. To further investigate this, we made use of GRGDSP, a peptide which inhibits binding of integrins to vitronectin and fibronectin. XTC fibroblasts injected with non-hydrolyzable analogs of GTP took much more time to round up than mock-injected cells in response to treatment with GRGDSP, while GDP beta S-injected cells rounded up in less time than controls. Injection with GTP gamma S did not inhibit cell rounding induced by trypsin however, showing that cell contractility is not significantly affected by the activation of GTPases. These data provide evidence for the existence of a GTPase which can control cell-substrate adhesion from the cytoplasm. Treatment of XTC fibroblasts with the phorbol ester 12-o-tetradecanoylphorbol-13-acetate reduced cell spreading and accelerated cell rounding in response to GRGDSP, which is essentially opposite to the effect exerted by non-hydrolyzable GTP analogs. These results suggest the existence of at least two distinct pathways controlling cell-substrate adhesion in XTC fibroblasts, one depending on a GTPase and another one involving protein kinase C.
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PMID:A GTPase controls cell-substrate adhesion in Xenopus XTC fibroblasts. 151 94

Fibronectin is a major component of decidual basement membrane. In the present study, we have investigated the effect of progestin on the synthesis and secretion of fibronectin in human endometrial stromal cells. Stromal cells were isolated during the menstrual cycle and cultured in RPMI-1640 with 2% fetal calf serum supplemented with progesterone or medroxyprogesterone acetate (MPA) in a long-term culture system. Indirect immunofluorescent staining showed that fibronectin was uniformly distributed in the intracellular and extracellular regions of stromal cells treated with MPA for 14 days. The biosynthesis and secretion of this protein and the accumulation of cellular fibronectin mRNA were studied after various culture periods. Cells were pulse-labelled with [35S]methionine to determine the amount of newly synthesized fibronectin secreted into the culture medium. A monoclonal antibody (Mab) identified human fibronectin on SDS-polyacrylamide gel electrophoresis (SDS-PAGE), showing a predominant band (Mr 230-250 kDa) which migrated with authentic fibronectin run in parallel. In six endometrial specimens, the amount of radioactivity incorporated as [35S]fibronectin was increased by progestin. Maximal stimulation occurred after 6 days treatment with MPA. Culture beyond 16 days reduced the rate of synthesis and secretion to 40% of the maximum. The effect of progestin was dose dependent with 0.02, 0.2 and 1 microM progesterone, producing 2.0, 3.8 and 11-fold increases respectively, over the control. Medroxyprogesterone acetate was more effective than progesterone, the maximal response (10-fold increase) being achieved at 0.02 microM MPA.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Progestin stimulates the biosynthesis of fibronectin and accumulation of fibronectin mRNA in human endometrial stromal cells. 153 46

The ability of peripheral blood neutrophils to injure elements of the alveolar septum was assessed. Experiments consisted of activating previously isolated neutrophils (PMNs) with a soluble (phorbol myristate acetate, PMA) and a particulate (zymosan) trigger, and measuring detachment of 51Cr-labeled epithelial cells. In addition, the mechanisms of epithelial injury were investigated by including anti-proteinase and antioxidants in the system. Untriggered PMNs produced only slight detachment injury to epithelial cells at two effector-target cell ratios, this effect being dramatically increased after triggering with PMA; zymosan caused triggering but less than was produced by PMA. Alpha-1-protease inhibitor produced a decrease in detachment when both PMA- and zymosan-triggered cells were the effectors; superoxide dismutase did not significantly reduce detachment. The ability of triggered PMNs to cause proteolysis of fibronectin, as measured in a radiolabeled fibronectin matrix degradation assay, was related to their triggerability in the detachment assay, zymosan being largely ineffective in triggering enhanced proteolysis. These findings suggest that fibronectin is important in maintaining the integrity of the alveolar epithelial surfaces. Furthermore, in inflamed alveoli, activated PMNs can release proteinases, which cause degradation of this matrix component leading to compromise of the alveolar epithelial barrier.
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PMID:Activated human peripheral blood neutrophils produce epithelial injury and fibronectin breakdown in vitro. 154 80

Under normal conditions, the morphology of cultured endothelial cells (EC) is characterized by a contact-inhibited monolayer with a distinct cobblestone appearance. However, when treated with phorbol esters, EC acquire fibroblast-like growth characteristics, are no longer contact-inhibited in growth, become invasive and form pre-capillary, tubular structures within collagen matrices. These events describe the basic processes of angiogenesis. We characterized the early effects of phorbol-12-myristate-13-acetate (TPA) on the attachment and spreading of rat aortic endothelial cells (RAEC) to purified extracellular matrix proteins by analyzing the distribution of fibronectin integrin receptors and the organization of cytoskeleton microfilaments during RAEC spreading on four different extracellular matrix peptides (i.e., Collagen Types I and IV, fibronectin and laminin). Type IV collagen appeared to be the best substrate for RAEC adhesion and spreading while laminin proved to be the poorest. TPA (0.1 micron) decreased the rate of RAEC spreading on Type IV collagen with a subsequent delay in cell-cell contact formation. In contrast, TPA increases the rate of spreading and cell-cell contact formation of RAEC plated on laminin.
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PMID:TPA-induced differentiation of rat aortic endothelial cells is substrate-specific and receptor mediated. 161 27

The complete structure of the human gene for 92-kDa type IV collagenase was determined. Two overlapping genomic clones spanning 26 kilobases (kb) of genomic DNA were shown to contain the entire 7.7-kb structural gene together with 15 and 3.5 kb of 5'-end and 3'-end flanking regions, respectively. The 92-kDa type IV collagenase gene contains 13 exons as does the 72-kDa type IV collagenase gene. All intron locations of the 92-kDa enzyme gene coincided with intron locations in the 72-kDa enzyme gene. Exons 5, 6, and 7 which were 174, 174, and 177 base pairs long, respectively, each encoded one complete internal repeat which resembles the collagen-binding domains of fibronectin. The sequence coding for a unique 48-residue segment in the 92-kDa type IV collagenase that has no counterpart in other metalloproteinases was not present in a separate exon, but was contained in exon 9 which also codes for sequences with homology to the other metalloproteinases. The initiation site for transcription was determined by primer extension analysis. Sequencing analysis of 599 base pairs of the 5'-end flanking region showed that the promoter does not have a TATA motif, but a TTAAA sequence at position -29 to -25. A CAAT motif was not observed but there was one GC box. Two putative 12-O-tetradecanoyl-phorbol-13-acetate (TPA) response elements, that might serve as binding sites for the transcription factor AP-1 and a consensus sequence of a transforming growth factor beta 1 (TGF-beta 1) inhibitory element were found in the promoter region. Gelatinase assay of enzyme secreted by cultured human fibrosarcoma cells (HT-1080) revealed only low levels of 92-kDa type IV collagenase activity, whereas considerable activity of the 72-kDa enzyme was present. Northern hybridization analysis confirmed these findings. Treatment of the HT-1080 cells with TPA resulted in induction of the secretion of 92-kDa type IV collagenase activity. This induction could not be significantly inhibited by concomitant incubation with TGF-beta 1. TPA and TGF-beta 1 did not markedly affect the activities of the 72-kDa enzyme. The activities of the secreted 92- and 72-kDa enzymes by HT-1080 cells correlated with the amounts of mRNA as estimated by Northern analyses.
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PMID:Complete structure of the human gene for 92-kDa type IV collagenase. Divergent regulation of expression for the 92- and 72-kilodalton enzyme genes in HT-1080 cells. 165 38

Human aortic endothelial cells, isolated at autopsy from a 52-year-old male dying from lung cancer, were treated with simian virus 40 (SV40). One colony was isolated from the infected endothelial cell culture 4 weeks after infection. The cells expressed SV40 large T antigen and p53 protein (p53) in their nuclei but lacted the characteristics of a transformed phenotype. The cells grew well in a monolayer over the 97th passage and exhibited Factor VIII-related antigen, Ulex europaeus 1 agglutinin (UEA-1) as endothelial cell markers, and a well-developed fibronectin network. The amount of prostacyclin synthesized by the cells was less than the amount synthesized by normal aortic or umbilical cord vein endothelial cells. The cells produced relatively large amounts of procollagenase, and 12-o-tetradecanoyl-phorbol-13-acetate (TPA) augmented the ability of the cells to produce this enzyme. These immortalized human aortic endothelial cells, which have some characteristics of normal endothelial cells and, like capillary endothelial cells, have the ability to produce collagenase, will probably prove useful for studies of atherosclerosis and angiogenesis.
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PMID:Collagenase production by immortalized human aortic endothelial cells infected with simian virus 40. 167 13

The effects of differentiation-modulating drugs were studied on the expression of intermediate filaments (IFs) in the human K562 erythroleukemic cell line. The untreated cells contained typical cytoplasmic coiling bundles, positive for both vimentin and cytokeratin as judged by indirect immunofluorescence microscopy with monoclonal antibodies (Mabs). Some of the cells also showed bright immunoreactivity for epithelial membrane antigen (EMA), as revealed with a Mab and polyclonal antiserum. When exposed to hemin or to sodium butyrate, most of the cells became cytokeratin negative within 3 days and showed dispersion of vimentin fibrils. Upon exposure to the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA), the amount of both vimentin and cytokeratin appeared to be greatly increased within 3 days and was found both in dispersed cytoplasmic fibrils, in large spherical, eccentric aggregates, as well as in cytoplasmic fibrils in cells spreading on fibronectin. TPA induced a complete loss of proliferation, as judged by immunostaining with the Mab Ki-67. The effects of TPA were found to be irreversible and could be induced by only a short exposure to the drug. Western blotting analysis and monoclonal antibodies to individual cytokeratins revealed that untreated K562 cells expressed Mr 52,000 (No. 8), 46,000 (No. 18), and 40,000 (No. 19) cytokeratin polypeptides, which disappeared when the cells were exposed to hemin or to sodium butyrate to induce erythroid differentiation but were greatly enhanced when exposed to TPA. The monoclonal anti EMA antibody reacted in K562 cells with a single Mr 320,000 polypeptide that was also revealed in MCF-7 breast carcinoma cells. Human bone marrow cells or other leukemic cell lines with erythroid differentiation capacity (HEL and KG-1) did not contain cytokeratin- or EMA-immunoreactive cells, suggesting that in K562 cells these properties may rather represent abnormal cytodifferentiation or retrodifferentiation toward early embryonic mesenchymal cells, than a more general expression of epithelial features in human leukemic cells.
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PMID:K562 erythroleukemia cells express cytokeratins 8, 18, and 19 and epithelial membrane antigen that disappear after induced differentiation. 169 28

The localization of five integrin subunit proteins was studied in human erythroleukemia (HEL) cells spreading on various culture substrata in the presence of 12-O-tetradecanoylphorbol-13-acetate (TPA) and the absence of serum. The cells readily adhered on fibronectin, but TPA was needed for adherence on vitronectin and for the spreading of the cells on both substrata. Indirect immunofluorescence microscopy showed that in the spread cells cultured on vitronectin or fibronectin for 2 hours, beta 1, beta 3, alpha 5, and alpha IIb integrin subunits were localized at focal adhesions as identified by talin-immunoreactivity. The alpha v integrin immunoreactivity was initially found at the focal adhesions when the cells were cultured on vitronectin, but was also found later in cells cultured on fibronectin. The alpha IIb integrin immunoreactivity disappeared from focal adhesions within 24 hours. The alpha 5 and beta 1 integrin immunoreactivities disappeared from the focal adhesions in cells cultured on vitronectin, but not in cells cultured on fibronectin. When the cells were plated on glass substratum in the presence of TPA, they spread much slower than on vitronectin or fibronectin, but some cells showed focal adhesions after only 8 hours in culture. In this case, the alpha v and beta 3 integrin subunits were found at focal adhesions. After TPA treatment, HEL cells deposited thrombospondin-immunoreactive material onto their culture substratum, but synthesis of fibronectin, vitronectin, fibrinogen, or von Willebrand factor was not detected. Thus, the results suggest that TPA would activate several integrin receptors in HEL cells and also stimulate the secretion of thrombospondin, which might be used as an adhesion ligand for the integrin vitronectin receptor alpha v/beta 3 complex.
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PMID:Localization of beta 1, beta 3, alpha 5, alpha v, and alpha IIb subunits of the integrin family in spreading human erythroleukemia cells. 169 47


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