3,6-Anhydroglucosaminyl formation in mucopolysaccharides

Establishment of a cell line from the EHS tumor: biosynthesis of basement membrane constituents and characterization of a hybrid proteoglycan containing heparan and chondroitin sulfate chains

We have established a continuous cell line from the Engelbreth-Holm-Swarm (EHS) tumor, a transplantable murine neoplasm that has been extensively utilized to investigate basement membrane constituents. The EHS-derived cells, designated BAM cells, have been subcultured for over 40 passages and have maintained phenotypic and biological properties of the parent EHS tumor cells. BAM cells have retained an epithelioid morphology and the ability to induce EHS-like tumors in mice. Biochemical and immunochemical studies demonstrated that BAM cells synthesize laminin A and B chains, collagen type IV, entactin and the basement membrane specific heparan sulfate proteoglycan. Interestingly, the proteoglycan synthesized by BAM cells was a hybrid molecule containing 2-3 heparan sulfate chains of 25-35 kDa and 1 chondroitin sulfate chain of approximately 17 kDa attached to a 400-kDa protein core. This cell line will be useful to investigations concerning biosynthesis of basement membrane constituents and will be a valuable source of extracellular matrix for testing cellular properties such as attachment, locomotion and differentiation.

Neoplastic modulation of extracellular matrix: stimulation of chondroitin sulfate proteoglycan and hyaluronic acid synthesis in co-cultures of human colon carcinoma and smooth muscle cells

Previous studies have shown that human colon carcinomas contain elevated amounts of chondroitin sulfate proteoglycan (CS-PG) and hyaluronic acid, and that the major site of synthesis of these products is the host mesenchyme surrounding the tumor. These findings have led to the proposal that the abnormal formation of the tumor stroma is modulated by the neoplastic cells. The experiments of this paper were designed to explore further this complex phenomenon in an in vitro system using co-cultures of phenotypically stable human colon smooth muscle (SMC) and carcinoma cells (WiDr). The results showed a 3-5-fold stimulation of CS-PG and hyaluronic acid biosynthesis in the co-cultures as compared to the values predicted from the individual cell type cultured separately. The increase in CS-PG was not due to changes in specific activity of the precursor pool, but was rather due to a net increase in synthesis, inasmuch as it was associated with neither a stimulation of cell proliferation nor with an inhibition of intracellular breakdown. These biochemical changes were corroborated by ultrastructural studies which showed a marked deposition of proteoglycan granules in the co-cultures. Several lines of evidence indicated that the SMC were responsible for the overproduction of CS-PG: i) SMC synthesized primarily CS-PG when cultured alone, in contrast to the WiDr, which synthesized exclusively heparan sulfate proteoglycan; ii) only the SMC in co-culture stained with an antibody raised against the amino terminal peptide of a CS-PG (PG-40), structurally and immunologically related to that synthesized by the SMC; iii) the stimulation of CS-PG in SMC could be reproduced, though to a lesser extent, using medium conditioned by WiDr, whereas medium conditioned by SMC had no effects on WiDr. In conclusion this study has reproduced in vitro a tumor-associated matrix with a proteoglycan composition similar to that observed in vivo and provides further support to the concept that production of a proteoglycan-rich extracellular environment is regulated by specific tumor-host cell interactions.

Structural characteristics of heparan sulfates with varying sulfate contents

Structural properties of heparan sulfate preparations from hog mucosa and beef lung sources were obtained by application of Smith degradation and nitrous acid reactions. Products formed by these reactions indicated that most of the iduronic acid present in these mucopolysaccharides is ester sulfated, whereas N-sulfated glucosamine residues are ester sulfated much less frequently. Repeating units with sulfated iduronic acid found to occur almost entirely in single sequences. Futhermore, the iduronic acid moieties may be bound to either N-acetylated or N-sulfated glucosamine units, with these occuring at either end of the uronic acid unit.

Depolymerization and de-N-acetylation of glycosaminoglycuronans by the action of alkali in the presence of sodium borohydride

Depolymerization of Ch-4-S, Ch-6-S, HA and HP was observed by gel filtration after treatment with 2-10 N NaOH or Ba(OH)2 in the presence of NaBH4 at 80-83 degrees for 1-5 hr. Depolymerized products were isolated after these treatments. 4-Deoxy-alpha-L-threo-4-enohexopyranosyluronic acid residue as the nonreducing end group was demonstrated by the H-1 and H-4 proton signals in the NMR spectra and by the absorption at 225-230 nm. L-Gulonic acid, which was produced from D-glucuronic acid by the action of NaBH4, was detected as the reducing end group in the depolymerized products of Ch-6-S, but no hexosaminitol was detected. De-N-acetylation to the extent of 34-50% occurred after treatment with 2.5 N NaOH in the presence of NaBH4, and almost complete de-N-acetylation accompanied by considerable destruction was observed with Ch-4-S and Ch-6-S after treatment with 5.5-10.0 N NaOH. A reaction mechanism is proposed for the depolymerization of glycosaminoglycuronans by the action of alkali.

The distribution of sulfated uronic acid and hexosamine residues in heparin and heparan sulfate

Heparins from various sources and heparan sulfate from umbilical cords have been subjected to Smith-degradation and reaction with nitrites. These procedures were effective for providing data relating to the distribution of sulfated iduronic acid residues in the molecule. Results indicated that heparins may have, as a prominent structural feature of the molecule, non-sulfated uronic acid distributed in single sequences, much as had been shown previously for N-acetylglucosamine residues. Sulfated uronic acid, however, may occur in multiple sequences of up to 5 or 6 residues. Heparan sulfate was found to have a major proportion of its ester sulfate on iduronic acid rather than hexosamine units, thereby having sections similar to those in heparins, though in considerably lower proportion.