Akira Tawada

DOMAIN STRUCTURE OF HEPARAN SULFATES FROM BOVINE ORGANS

Samples of heparan sulfate, isolated from bovine aorta, lung, intestine, and kidney, were degraded by digestion with a mixture of heparitinases or by treatment with nitrous acid, with or without previous N-deacetylation. Analysis of the resulting oligosaccharides showed that the various heparan sulfate samples all contained regions of up to 8 or 9 consecutive N-acetylated glucosamine residues, as well as contiguous N-sulfated sequences. L-Iduronic acid accounted for a remarkably constant proportion, 50-60%, of the total hexuronic acid units within the latter structures. Of the total iduronic acid units, 36-55% were located outside the contiguous N-sulfated regions, presumably in sequences composed of alternating N-acetylated and N-sulfated disaccharide residues. While most of the iduronic acid units within the N-sulfated blocks were 2-O-sulfated, those located outside were almost exclusively nonsulfated. The heparan sulfate preparations differed markedly with regard to the content of 6-O-sulfated glucosamine units, more than half of which were located outside the N-sulfated block regions. These findings suggest that the formation of iduronic acid residues and their subsequent 2-O-sulfation are coupled within but not outside the contiguous N-sulfated regions of the heparan sulfate chains and, furthermore, that the 2-O- and 6-O-sulfotransferase reactions are differentially regulated during heparan sulfate biosynthesis.

Analysis of unsaturated disaccharides from glycosaminoglycuronan by high-performance liquid chromatography☆

A rapid and simple analytical method for unsaturated disaccharide isomers formed by enzymatic digestion from hyaluronic acid, chondroitin sulfate, dermatan sulfate, heparan sulfate, and heparin by high-performance liquid chromatography using an amine-bound silica column with a linear gradient of sodium dihydrogen phosphate was developed. The analyses were performed on isomers of two groups belonging to the chondroitin sulfate family and the heparin sulfate family. In both families, disaccharide isomers eluted in the order non-, mono-, di-, and trisulfated disaccharides by elevating salt concentrations. The method was applied to the analysis of constituent disaccharides of representative sulfated glycosaminoglycans, which proved that most constituents could be quantified separately. This method is advantageous in that enzymatic digests can be applied directly on a column without any pretreatment and good resolution of several disaccharides can be obtained by one chromatography.

EFFECT OF HYALURONAN OLIGOSACCHARIDES ON THE EXPRESSION OF HEAT SHOCK PROTEIN 72

We have previously shown that intraarticular treatment with a hyaluronan (HA) preparation (840 kDa), HA84, up-regulates heat shock protein 72 (Hsp72) expression and suppresses degeneration of synovial cells in an arthritis model. In that study, the HA84 administered was degraded into HA oligosaccharides in the synovial tissue, suggesting that HA84 or degradation products of HA may up-regulate Hsp72 expression. Thus, in the present study, we examined the effects of HA of various molecular sizes on Hsp72 expression and cell death in stressed cells. Western blotting analysis showed that treatment of K562 cells with HA tetrasaccharides up-regulated Hsp72 expression after exposure to hyperthermia. On the other hand, treatment of the cells with HA of other sizes (di-, hexa-, deca-, dodecasaccharides), HA84, or tetrasaccharides of keratan sulfate did not elicit any change in expression of the Hsp72 protein. Treatment of the cells with tetrasaccharides of HA up-regulated not only expression of the Hsp72 protein but also Hsp72 mRNA expression and enhanced activation of HSF1, a transcription factor controlling Hsp72 expression, after exposure to hyperthermia. Because the level of Hsp72 protein was not affected by tetrasaccharides of HA when the K562 cells were kept at 37 °C without any stress, it is evident that tetrasaccharides of HA did not act as a stress factor. In addition, tetrasaccharides of HA suppressed cell death in the case of K562 cells exposed to hyperthermia and of PC12 cells under serum deprivation. These results suggest that a certain size of oligosaccharides,i.e. the tetrasaccharides of HA, up-regulates Hsp72 expression by enhancing the activation of HSF1 under stress conditions and suppresses cell death.

Characterization of oligosaccharides of the lactosamine series derived from keratan sulfates by tandem mass spectrometry

Positive- and negative-ion fast-atom bombardment tandem mass spectrometry with collision-induced dissociation (FAB-CID-MS/MS) has been used in the characterization of di-and tetra-saccharides of the lactosamine series from keratan sulfates. FAB-CID-MS/MS of Galβ1-4GlcNAc (L1) exhibited strong fragment ions originating from ring cleavage at the reducing-terminal sugar moiety together with glycosidic bond-cleavage ions, whereas GlcNAcβ1-3Gal (K1) showed strong glycosidic bond-cleavage ions but no ring-cleavage ions. A series of ring-cleavage fragment ions was observed with members of the L-series which have free hydroxyl groups at the C1 and C3 positions. CID-MS/MS spectra of the [M + Na – SO3]+ ion (m/z 406) from L2 and the [M + Na − 2SO3]+ ion (m/z 406) from L4 were almost identical with the CID-MS/MS spectrum of the [M + Na]+ ion (m/z 406) from L1, which indicated that the sugar skeletons of L2 and L4 are the same as that of L1. On the other hand, the CID-MS/MS spectrum of the [M + Na – SO3]+ ion (m/z 508) from L4 did not resemble that of the [M + Na]+ ion (m/z 508) from L2. The former showed peaks that were additional to the peaks in the latter. Since these extra peaks were accounted for on the basis of the structure of L3 [Galβ1(6S)-4GlcNAc, S = sulfate], the in-source loss of sulfate groups by ester exchange upon FAB ionization takes place in a dual manner; one reaction at the non-reducing terminal sugar to give L2 and the other at the reducing-terminal sugar to give L3. The CID-MS/MS spectra were characteristic for the tetrasaccharides L1-L1, L2-L2 and L4-L4 while in-source fragmentation confirms the component disaccharides of each tetrasaccharide. The structure of a tetrasaccharide trisulfate was confirmed as L2–L4 and not L4–L2 by CID-MS/MS. Negative-ion FAB-CID-MS/MS spectra of the sulfated di-and tetra-saccharides showed a pattern similar to that of the positive-ion spectra. Subtraction of the CID-MS/MS spectrum of the [M – H]− ion of L2 [Galβ1-4GlcNAc(6S)] from that of the [M – H – SO3]− ion of L4 [Gal(6S)β1-4GlcNAc(6S)] gave several specific ions whose origins were nicely explained on the basis of the structure of L3. The structure of a pentasaccharide consisting of N-acetylneuraminic acid and a tetrasaccharide trisulfate was confirmed, on the basis of FAB-CID-MS/MS, as NeuNAcα2-6L2-L4.