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J D Gregory

Publications and source records attributed to J D Gregory.

28 records · Page 2Linked to original sources
PubMed1983

Receptor-mediated endocytosis of proteoglycans by human fibroblasts involves recognition of the protein core.

Endocytosis by cultured human skin fibroblasts of 35SO4(2-)-labelled or [3H]leucine-labelled proteoglycans from fibroblast secretions and of 125I-proteodermatan sulphate from pig skin was quantitatively investigated. The following results were obtained. (1) Core proteins prepared by digestion with chondroitin ABC lyase were at least as efficiently endocytosed as native proteoglycans. Pig skin proteodermatan sulphate was a competitive inhibitor of endocytosis of 35SO4(2-)-labelled proteoglycans. (2) Proteoglycans produced in the presence of tunicamycin and native proteoglycans degraded with endoglycosaminidase H were internalized at a normal rate. Several monosaccharides that can be bound by mammalian lectins were unable to influence the internalization of proteoglycans. Treatment of proteoglycans with neuraminidase, however, resulted in an increased clearance rate. (3) Reductive methylation or acetoacetylation of lysine residues was accompanied by a parallel decrease in the rate of proteoglycan endocytosis. Reversal of acetoacetylation normalized the uptake properties. Endocytosis of native proteoglycans was also reduced in the presence of poly-L-lysine, and this reduction in endocytosis was observed as well with proteoglycans synthesized in the presence of the lysine analogue S-2-aminoethylcysteine. These results suggest that the recognition marker required for receptor-mediated endocytosis of proteodermatan sulphate resides in its protein moiety and involves lysine residues.

Amino Acids↗
PubMed1983

Proteoglycans of rabbit cornea: labelling in organ culture and in vivo.

Rabbit corneas maintained with radioactively-labelled precursors in organ culture for up to 42 hr produced labelled proteoglycans of the same kind as those that exist normally or that are produced by labelling in vivo. Whole corneas, including a narrow strip of sclera, were kept in culture in the presence of [3H]-glucosamine and [35S]-sulfate. The rate of incorporation of sulfate into extractable proteoglycans was linear over the time investigated, as was the rate of incorporation of glucosamine after a short lag. Three labelled proteoglycans were isolated and found to behave in ion-exchange chromatography and gel chromatography in the same way as they did in previous studies by chemical analysis. Their labelled glycosaminoglycans were primarily dermatan sulfate and keratan sulfate, with traces of hyaluronic acid and heparan sulfate. When labelled precursors were injected directly into the anterior chamber of rabbit eyes, the resulting labelled proteoglycans were similar to those obtained in organ culture. Both in vivo and during organ culture, the specific activity of hexosamine in the keratan sulfate proteoglycans was about one-half that in dermatan sulfate, probably because of different synthetic rates or different specific activities of immediate precursors.

Animals↗
PubMed1982

Proteoglycans of rabbit corneal stroma. Isolation and partial characterization.

Proteoglycans extracted from rabbit corneal stroma can be separated by ion exchange and gel chromatography into two proteokeratan sulfates (PKS-I, PKS-II) and two proteodermatan sulfates (PDS-I, PDS-II). PKS-I (21% of the total glycosaminoglycans) contains 48% protein, and PKS-II (43% of the total) has 57% protein. In both, the only hexosamine is glucosamine, 7% of which is found in oligosaccharides. There is much more sialic acid in the oligosaccharides of PKS-II than of PKS-I, and the amino acid compositions of the two proteoglycans differ significantly. The keratan sulfates isolated from them by papain digestion are different in size, but both are digested by endo-beta-galactosidase. PDS-I (30% of the total glycosaminoglycans) has 32% protein, and 35% of its uronic acid is iduronic acid. PDS-II (6% of the total) has 42% of its uronic acid as iduronic. In general, the four rabbit proteoglycans resembled those of human and bovine corneal stroma in being smaller and more protein-rich than those of cartilage.

Amino Acids↗
PubMed1982

Proteodermatan sulfate isolated from pig skin.

The major proteoglycan of pig skin, a proteodermatan sulfate, has been isolated under mild conditions in the presence of protease inhibitors. After purification by ion exchange and gel chromatography, it has a Mr of 70 x 10(3) and it does not form aggregates with hyaluronic acid. It contains about 60% protein, one chain of dermatan sulfate, and several oligosaccharide chains. The dermatan sulfate is high in iduronic acid (85% of the uronic acid) and there are no chains of chondroitin sulfate present. The oligosaccharides contain glucosamine, sialic acid, and neutral sugars.

Amino Acids↗
PubMed1979

Isolation of proteoglycan-hyaluronate complexes from bovine aorta.

Two proteoglycan-hyaluronate complexes were extracted from bovine aorta with 4.0 M guanidinium chloride in the presence of protease inhibitors and purified by cesium chloride density gradient centrifugation under associative conditions. Complex I with higher buoyant density had 22% protein and 18% uronate, whereas Complex II had 11% protein and 23.6% uronate. Glycosaminoglycan (GAG) analysis of the complexes indicated that both complexes contained large amounts of hyaluronic acid, 13.6% and 24.0% of the total GAG in Complexes I and II, respectively. Chondroitin sulfates and dermatan sulfate constituted the remainder of the GAG. Chromatography on Sepharose CL 6B suggested that Complex I had an estimated molecular weight of 800,000 and Complex II, 250,000. The complexes were dissociated into proteoglycan and hyaluronate by cesium chloride density gradient centrifugation under dissociative conditions. The proteoglycans free of hyaluronic obtained from the complexes had similar protein and GAG composition. The molecular weight of the proteoglycan was estimated to be 80,000 and that of the hyaluronate of the complex, 90,000.

Animals↗
PubMed1973

Multiple aggregation factors in cartilage proteoglycan.

Proteoglycan as isolated from bovine nasal septa is a partially aggregated complex containing linking factors. Two essential factors can be separated from proteoglycan subunits and resolved in a CsCl density gradient. Chondroitinase digestion of the purified proteoglycan subunits does not interfere with their aggregation when the linking factors are added.

Animals↗