Sulfated glycosaminoglycans of cells grown in culture: dermatan sulfate disappearance in successive fibroblast subcultures

Identification of linear heparin-binding peptides derived from human respiratory syncytial virus fusion glycoprotein that inhibit infectivity

It has been shown previously that the fusion glycoprotein of human respiratory syncytial virus (RSV-F) interacts with cellular heparan sulfate. Synthetic overlapping peptides derived from the F-protein sequence of RSV subtype A (strain A2) were tested for their ability to bind heparin using heparin-agarose affinity chromatography (HAAC). This evaluation identified 15 peptides representing eight linear heparin-binding domains (HBDs) located within F1 and F2 and spanning the protease cleavage activation site. All peptides bound to Vero and A549 cells, and binding was inhibited by soluble heparins and diminished by either enzymatic treatment to remove cell surface glycosaminoglycans or by treatment with sodium chlorate to decrease cellular sulfation. RSV-F HBD peptides were less likely to bind to glycosaminoglycan-deficient CHO-745 cells than parental CHO-K1 cells that express these molecules. Three RSV-F HBD peptides (F16, F26, and F55) inhibited virus infectivity; two of these peptides (F16 and F55) inhibited binding of virus to Vero cells, while the third (F26) did not. These studies provided evidence that two of the linear HBDs mapped by peptides F16 and F55 may mediate one of the first steps in the attachment of virus to cells while the third, F26, inhibited infectivity at a postattachment step, suggesting that interactions with cell surface glycosaminoglycans may play a role in infectivity of some RSV strains.

Is there a glycosaminoglycan-related heterogeneity of the thymic epithelium?

We determined the synthesis and secretion of glycosaminoglycans by three distinct preparations of mouse cultured thymic epithelial cells. These comprised primary cultures of thymic nurse cells (TNCs), which are normally located within the cortex of the thymic lobules, as well as two murine thymic epithelial cells, bearing a mixed, yet distinct, cortico-medullary phenotype. We first identified and measured the relative proportions of the various glycosaminoglycans in the three epithelial cells. Non-sulfated glycosaminoglycans are preponderantly secreted by the TNCs, while the sulfated glycans (particularly heparan sulfate) are relatively more abundant on the cell surface. The three types of epithelial cells differ markedly in their heparan sulfate composition, mainly due to different patterns of N- and O-sulfation. In addition, the cells differ in the synthesis and secretion of other glycosaminoglycans. Thus, TNCs secrete high amounts of dermatan sulfate + chondroitin sulfate to the culture medium. IT-76M1 cells secrete high proportions of heparan sulfate while 2BH4 cells show a more equilibrated proportion of dermatan sulfate/chondroitin sulfate and heparan sulfate. The three epithelial cells also differ in their capacity to produce hyaluronic acid and 2BH4 cells are distinguished by their high rate of synthesis of this glycosaminoglycan. In conclusion, our results show that distinct thymic epithelial cells can synthesize different types of glycosaminoglycans. Although it remains to be definitely determined whether these differences reflect the in vivo situation, our data provide new clues for further understanding of how glycosaminoglycan-mediated interactions behave in the thymus.

Proteoglycans synthesized by the hepatic granulomas isolated from schistosome-infected mice and by the granuloma-derived connective tissue cell lines

Proteoglycans synthesized in vitro by periovular granulomas isolated from livers of schistosome-infected mice were compared with those produced by granuloma-derived cell lines: the primary cell line GR and the permanent cell line GRX. Proteoglycans were metabolically labelled with 35S-sulfate and extracted with 4 M guanidine-HCl containing 2.0% Triton X-100, in the presence of proteinase inhibitors. The radiolabelled proteoglycans were purified and characterized by anion-exchange, gel-filtration and affinity-column chromatography. Heparan sulfate proteoglycans (HS-PGs) and chondroitin sulfate/dermatan sulfate-containing proteoglycans (CS/DS-PGs) were detected in both the culture medium and the cell-associated fractions obtained from GR cells. More than 90% of the cell-associated HS-PG from these cells contained a hydrophobic portion, as evidenced by their ability to bind to octyl-Sepharose. In contrast, among the secreted proteoglycans, it was the CS/DS-PG and not the HS-PG that bound to this resin. The major fractions of cell-associated and secreted proteoglycans from GRX cells were HS-PGs. Similar to HS-PGs from GR cells, 50% of the cell-associated HS-PG bound to octyl-Sepharose, while only 20% of secreted proteoglycans (HS-PGs) bound to this resin. The proteoglycans purified from the whole granuloma were composed mainly of DS-PG, of a size and hydrophobicity similar to the CS/DS-PG from GR cells. Possible correlations among the structure, secretion, distribution and function of proteoglycans in granulomatous reactions are discussed.

Membrane-associated and secreted proteoglycans from a continuous cell line derived from fibrotic schistosomal granulomas

Proteoglycans were isolated from a continuous murine cell line (GRX) established from fibrotic granulomas induced in mouse liver by schistosomal infection, representative of liver connective tissue cells. The proteoglycans were labelled with 35SO4, extracted by guanidine-HCl + Triton X-100 in the presence of proteinase inhibitors, and purified by anion-exchange, gel-filtration and affinity-column chromatography. The major fractions of cell-associated and secreted proteoglycans are heparan sulfate proteoglycans. Gel-filtration chromatography on Sephacryl S-400 revealed Kav values of 0.20 and 0.30 for the cell-associated and secreted heparan sulfate proteoglycans, respectively. About 50% of the cell-associated heparan sulfate proteoglycans contained hydrophobic regions, as evidenced by their ability to bind to octyl-Sepharose, while only about 20% of secreted proteoglycans bound to this resin. In addition, no proteoglycan was competitively displaced from the cell surface by heparin. Taken together with other reports on proteoglycan synthesis by a variety of cell types in culture, these observations suggest that cell-surface heparan sulfate proteoglycans possibly contain a hydrophobic domain that functions as a membrane anchor in their attachment to cells. Addition of beta-D-xyloside to the cultures greatly enhanced the release of 35S-dermatan sulfate to the medium. Interestingly, dermatan sulfate is the major glycosaminoglycan found in the schistosoma-induced granuloma, from which the GRX cell line is derived. These studies provide the first biochemical description of the proteoglycans produced by a liver connective tissue cell line derived from schistosomal granulomas.

Sulfated glycosaminoglycans synthesized by fibroblast, smooth muscle and endothelium-like cells grown in culture

Monolayer cultures of fibroblast, smooth muscle and endothelium-like cells incorporated 35SO2-(4) into glycosaminoglycans of the extracellular, pericellular and intracellular compartments. These glycosaminoglycans have been identified on the basis of electrophoretic mobility, enzymatic degradation with specific mucopolysaccharidases and by the type of degradation products formed. The sulfated glycosaminoglycans from the extracellular pool of the three cell types show a similar composition, while the intracellular and pericellular pools of the three cells have a different glycosaminoglycans composition. They differ in the relative proportion of heparitin sulfate and chondroitin sulfate and in the structure of isomeric chondroitin sulfate.

Sulfated glycosaminoglycan and collagen patterns in parietal yolk sac carcinoma (PYSC)

Electrophoretic analyses of collagenous material have shown that the parietal yolk sac carcinoma (PYSC) ascitic tumour synthesizes polypeptide chains that migrate as type IV procollagen. Having molecular weights of 185,000 and 160,000, these polypeptides are sensitive to collagenase. When the PYSC cells are injected subcutaneously, they form a solid tumour, and type I collagen predominates. The electrophoretic analyses of sulfated glycosaminoglycans and enzymatic degradation have shown a predominance of heparan sulfate in the ascitic tumour, and of chondroitin sulfate B in the solid tumour. Cells cultured from ascitic tumours have maintained the same collagen and sulfated glycosaminoglycan patterns as the original cells, whereas in the solid tumour culture only chondroitin sulfate AC has been detected.

Werner's syndrome: a review of recent research with an analysis of connective tissue metabolism, growth control of cultured cells, and chromosomal aberrations

Werner's syndrome is a rare, autosomal recessive condition with multiple progeroid features, but it is an imitation of aging rather than accelerated or premature senescence. Somatic chromosome aberrations occur in multiple tissues in vivo and in vitro, and there is an increased incidence of neoplasia. Thus. Werner's syndrome can be classified in the group of chromosome instability syndromes. Recent findings provide additional support for the concept that there is an aberration of connective tissue metabolism in Werner's syndrome, but it is unclear whether this is a primary or secondary manifestation of the underlying genetic defect. Abnormal growth characteristics are observed in cultured skin fibroblast-like cells and this provides another avenue for current research. Identification of the basic genetic defect in Werner's syndrome might clarify our understanding of the normal aging process in general, or might elucidate specific aspects such as the development of neoplasia, atherosclerosis, diabetes, or osteoporosis.