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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Fat-storing cells (perisinusoidal lipocytes, Ito cells) are the major connective tissue-producing cell type in liver. In areas of necroinflammation the cells proliferate and transform into desmin and smooth muscle alpha-actin-positive myofibroblast-like cells which synthesize a broad spectrum of significant amounts of collagens, proteoglycans, and matrix glycoproteins. Available data suggest a central role for these cells in the pathogenesis of fibrosis. Beta-D-Xyloside, an artificial initiation site for galactose-linked glycosaminoglycans, thereby uncoupling the synthesis of core protein and GAG, was used as a probe to study main cellular functions under conditions of abrogated proteoglycan synthesis. The exposure for 48 hr of fat-storing cells to p-nitrophenyl beta-D-xyloside (PNP-Xyl) increased dose-dependently the synthesis of [35S]sulfate-labeled medium GAG. Maximum stimulation of fivefold above normal was reached at 1.0 mM PNP-Xyl. Higher concentrations of PNP-Xyl progressively decreased the stimulatory effect on GAG synthesis. The relative composition of GAG in medium (60% chondroitin sulfate, 34% dermatan sulfate), at the cell surface, and intracellularly (mainly heparan sulfate) was not changed significantly by PNP-Xyl. The amounts of intracellular and cell surface-bound GAG were reduced by 40 and 30%, respectively, by PNP-Xyl leading to a depletion of heparan sulfate at the cell surface. Pulse-chase experiments revealed that xyloside-initiated GAG were secreted immediately after synthesis into the medium. GAG synthesized in the presence of 1 and 5 mM PNP-Xyl were free of core protein, and the molecular size of the GAG chains was smaller than that of GAG obtained from beta-eliminated proteoglycans synthesized in control cultures. At concentrations above 3 mM PNP-Xyl generated a dose-dependent inhibition of cell proliferation, which was at any stage of culture fully reversible upon removal of the drug. Viability and general protein synthesis were not reduced, but fat-storing cell transformation and deposition of matrix glycoproteins were retarded. Only a very small fraction of drug-treated cells (5 mM PNP-Xyl) did express on the 11th culture day smooth muscle iso-alpha-actin- and desmin-containing cytoskeletal filaments, which are important indicators of transformation into myofibroblast-like cells. Furthermore, the synthesis of hyaluronan and the expression of immunostained fibronectin, laminin, and tenascin were reduced in cultures exposed to 5 mM PNP-Xyl. The described cellular functions were not affected by exposure of fat-storing cells to p-nitrophenyl beta-D-galactoside.(ABSTRACT TRUNCATED AT 400 WORDS)
Exp Mol Pathol 1991 Oct
PMID:Proliferation and transformation of cultured liver fat-storing cells (perisinusoidal lipocytes) under conditions of beta-D-xyloside-induced abrogation of proteoglycan synthesis. 171 76

The use of specific inhibitors of proteoglycan synthesis have demonstrated essential functions for these molecules. Proteoglycans do not appear to be essential for cell viability or proliferation but are necessary for stable assembly of ECM and functional cell-ECM interaction. Because of their ability to nearly completely abolish ECM assembly in cell culture systems, proteoglycan synthesis inhibitors are useful tools to examine effects of ECM on the phenotypic behavior of cells. Despite its usefulness, the use of proteoglycan synthesis inhibitors has some drawbacks. The most significant of these is the fact that synthesis of all proteoglycans is inhibited, making it difficult to assign a particular function to a specific proteoglycan type. For this reason, inhibition studies need to be done in conjunction with additional biochemical, immunological or molecular biological studies.
Mol Cell Biochem
PMID:Biological functions of proteoglycans: use of specific inhibitors of proteoglycan synthesis. 192 2

The role of extracellular matrix (ECM) in the differentiation of tissue types was examined in embryos of Strongylocentrotus purpuratus. We have examined the expression of various tissue-specific molecular markers after disrupting the ECM by culturing embryos in the presence of beta-aminoproprionitrile fumarate (BAPN), which disrupts collagen deposition, and beta-D-xyloside, which disrupts proteoglycan metabolism. The markers examined included accumulation of primary mesenchyme-specific mRNA (SM 50); an aboral ectoderm-specific mRNA (Spec 1); and a gut-specific enzyme, alkaline phosphatase. Treatment with BAPN or beta-D-xyloside results in developmental arrest at the mesenchyme blastula stage. Although spicule formation is inhibited, the accumulation of SM 50 transcripts and the synthesis of most of the prominent spicule matrix proteins is similar to that of control embryos. Spec 1 mRNA, in contrast, while accumulating to a significant extent when collagen and proteoglycan metabolism is disrupted, does accumulate to a level somewhat lower than that seen in control embryos. Additionally, the postgastrula rise in gut-specific alkaline phosphatase is reversibly inhibited by BAPN and xyloside treatment. These results demonstrate a differential effect of the ECM on expression of tissue-specific molecular markers.
Mol Reprod Dev 1991 Jul
PMID:Role of the extracellular matrix in tissue-specific gene expression in the sea urchin embryo. 193 Oct 40

Transformed fat storing cells, i.e. myofibroblast-like cells are the major source of proteoglycans in injured liver. In the present study p-nitrophenyl-beta-D-xylopyranoside (PNP-Xyl), a specific metabolic inhibitor of proteoglycan synthesis, was used to analyze some details of altered glycosaminoglycan metabolism, proliferation, morphology and cytoskeletal organization of myofibroblast-like cells (secondary cultures of fat storing cells) under conditions of abrogated proteoglycan synthesis. PNP-Xyl increased dose-dependently the synthesis of [35S] sulfate-labelled medium glycosaminoglycans, among which chondroitin sulfate formation was stimulated predominantly. The distribution and composition of glycosaminoglycans in the cellular and cell surface compartments were affected differently. Production of medium hyaluronan was reduced by more than 40% at 5 mM PNP-Xyl. The compound inhibited dose-dependently the mitotic activity of myofibroblast-like cells without affecting viability. The morphologic appearance was changed at 5 mM PNP-Xyl and the organization and expression of desmin and smooth muscle iso-alpha-actin, both important markers of myofibroblast-like cells, were also modified by PNP-Xyl. Inhibition of proliferation, morphologic changes, and cytoskeletal disorganization were fully and rapidly reversible upon removal of the drug. The results support the notion of a direct or indirect role of proteoglycans in maintaining important functions of myofibroblast-like cells in culture.
Cell Mol Biol 1991
PMID:Beta-D-xyloside induced modulations of glycosaminoglycans, proliferation, and cytoskeletal organization of rat liver myofibroblast-like cells (transformed fat storing cells). 193 24

The turnover of proteoglycans in the extracellular matrix was studied in fibroblasts cultures derived from patients with mucopolysaccharidosis (MPS) and healthy donors. The cells were labelled with 35S-sulfate and 14C-glucosamine and it was found that in MPS-fibroblasts the rate of extracellular matrix turnover was hardly affected, where as the intracellular turnover was severely inhibited. Similar results were obtained with normal fibroblasts treated with 20 mM ammonia. Autoradiography revealed that MPS fibroblasts have a preferential accumulation of 35S-sulfate labelled material in the nuclear area, indicating that the nucleus may also be affected in MPS pathology. It is suggested that, although lysosomal enzymes are an important factor in intracellular proteoglycan turnover, they do not play a crucial role in the turnover of extracellular matrix proteoglycans.
Cell Mol Biol 1990
PMID:Turnover of proteoglycans in skin fibroblast cultures derived from patients with mucopolysaccharidoses. 212 43

Proliferation of smooth muscle cells is an important component of pulmonary arterial morphogenesis, both during normal development and pathologic remodeling. However, little is known of the factors that regulate smooth muscle proliferation in these vessels. To investigate the hypothesis that factors produced by endothelial cells may regulate smooth muscle cell growth, we studied the effects of culture medium conditioned by fetal bovine pulmonary arterial endothelium on proliferation of smooth muscle cells in culture. This conditioned medium contains an inhibitor of smooth muscle proliferation that is degraded by nitrous acid, heparinase, and heparitinase, but resists degradation by protease, boiling, and chondroitin ABC lyase, indicating that the inhibitor is structurally similar to heparin. Inhibitor release occurs in both growing and confluent endothelial cell cultures and in the presence and absence of serum. A growth-inhibiting proteoglycan purified to homogeneity from endothelial cell-conditioned medium has physicochemical characteristics similar to those of the prototypic basement membrane heparan sulfate proteoglycan of the Englebreth-Holm-Swarm tumor: an overall size of approximately 10(6) D, heparan sulfate chains of 60,000 D, and a buoyant density of 1.33 g/ml. Antibody raised against the tumor basement proteoglycan recognizes this endothelial heparan sulfate proteoglycan, and Western blotting after SDS-PAGE demonstrates that the core proteins of both proteoglycans migrate as a doublet at apparent molecular weights of 450,000 and 360,000 D. Heparan sulfate glycosaminoglycan prepared from purified medium proteoglycan is a potent inhibitor of smooth muscle cell growth, exhibiting activity approximately 1,000 times greater than that of heparin. These results indicate that endothelial cells cultured from fetal bovine pulmonary arteries produce a basement membrane heparan sulfate proteoglycan that is a potent inhibitor of smooth muscle proliferation. This proteoglycan may mediate endothelial regulation of smooth muscle growth during development or pathologic pulmonary arterial remodeling.
Am J Respir Cell Mol Biol 1990 Jan
PMID:Endothelial heparan sulfate proteoglycan. I. Inhibitory effects on smooth muscle cell proliferation. 213 6

The effects of herpes simplex virus type 1 (HSV-1) infection on proteoglycan synthesis by human endothelial cells were studied as a model of endothelial cell injury. Confluent cultures of early passage endothelial cells from human umbilical vein were infected with HSV-1 at multiplicities of infection from 0.001 to 1.0. HSV-1 infection produced a dose-dependent inhibition of total proteoglycan synthesis of up to 85%. Although there was a 2- to 3-fold increase in the quantity of virus necessary to cause 50% inhibition of heparan sulfate compared to chondroitin/dermatan sulfate proteoglycan, the inhibition was relatively parallel, even up to high virus doses. There was no inhibition of an undersulfated heparan sulfate proteoglycan that contained glycosaminoglycan chains shorter than the predominant species. The results indicate that HSV-1 infection of human endothelial cells produces complex effects on host-cell metabolism. The viral-induced changes in proteoglycan metabolism may influence cell-matrix interactions and lead to altered vessel wall function.
Am J Respir Cell Mol Biol 1990 May
PMID:Inhibition of proteoglycan synthesis in human endothelial cells after infection with herpes simplex virus type 1 in vitro. 216 Feb 54

Syndecan, a cell surface proteoglycan, is an integral membrane protein acting as a receptor for the extracellular matrix. For chromosomal localization of the human syndecan gene, a panel of mouse-human somatic cell hybrids was analyzed by Southern blotting using the cDNA probe for human syndecan. The hybrids were karyotyped at the time of DNA extraction. A band corresponding to the human syndecan gene in Southern blots was found only in a hybrid cell line containing human chromosome 2. This hybrid was subcloned and its subclones were analyzed by Southern blotting and karyotyped. Subclones carrying human chromosome 2 contained the syndecan gene, while subclones not carrying this chromosome did not. The human syndecan gene is thus assigned to chromosome 2.
Somat Cell Mol Genet 1990 Sep
PMID:Localization of gene for human syndecan, an integral membrane proteoglycan and a matrix receptor, to chromosome 2. 217 54

Vascular basement membrane contains laminin, fibronectin, proteoglycan and collagens. These molecules have been identified in various tissues by immunolabeling methods and biochemical analyses. We have previously localized laminin, fibronectin and type IV collagen to the basement membrane of rat retinal vessels at the ultrastructural level using an immunoperoxidase method. In this study, we use an immunogold method to re-examine the distribution of these molecules and also to study the localization of heparan sulfate proteoglycan and types I, III and V collagen in the retinal capillary basement membrane. Gold labeling for laminin, type IV collagen and proteoglycan were found diffusely on the basement membrane of the endothelium and pericyte, while that for fibronectin and type V collagen was spotty and variable and that for types I and III collagen was negligible. The segment of basement membrane between the endothelial cell and pericyte appeared less reactive to anti-laminin and anti-type IV collagen than the membrane between the pericyte and perivascular neuroretina. The immunogold method may be useful in quantitative studies of thickened basement membranes under abnormal conditions.
Cell Mol Biol 1990
PMID:Immunogold localization of basement membrane molecules in rat retinal capillaries. 233 11

The MHC Class II molecular complex is composed of polymorphic alpha and beta chains and a non-polymorphic "invariant" chain (Ii) that can be converted to a chondroitin sulfate proteoglycan. To determine whether the proteoglycan form of invariant chain (Ii-CS) had a role in the expression of the Class II complex, we studied the biosynthetic fate of alpha-beta in cells transfected either with normal Ii cDNA or with a site-directed mutant of Ii (IiAla201) that lacked the site of glycosaminoglycan addition. We had reported [Miller J., Hatch J. A., Simonis S. and Cullen S. E. (1988) Proc. Natl. Acad. Sci. U.S.A. 85, 1359-1363] that the mutant protein associated stably with alpha and beta chains, and that it showed charge heterogeneity suggesting some oligosaccharide processing. In this study we demonstrated that the rate and extent of alpha-beta processing and the rate of alpha-beta cell surface expression is the same in the presence of either normal or mutant Ii. Examination of the mutant Ii protein itself revealed normal transport through different processing compartments, as evidenced by the addition of fatty acid and by maturation of N-linked oligosaccharides. Moreover, though the rate of conversion of IiAla201 into more processed forms was slower in the absence of alpha-beta than in its presence, this was also typical of the wild type invariant chain. The ability to alter glycosaminoglycan addition without significantly disturbing other processing events or trafficking should allow a rigorous assessment of the impact of glycosaminoglycan addition on Class II function.
Mol Immunol 1990 May
PMID:Biosynthesis and intracellular transport of MHC class II molecules associated with a mutated, glycosaminoglycan-negative invariant chain. 236 58


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