A unique heparan sulfate in the nuclei of hepatocytes: structural changes with the growth state of the cells.

Abstract

Abstract. Growing and confluent cultures of a rat hepatocyte cell line were labeled with 35SO42-and the heparan sulfate in the culture medium, the pericellular matrix, the nucleus, the nuclear outer membrane, and the remaining cytoplasmic pool was purified by DEAE-cellulose chromatography. The heparan sulfate in all pools from the confluent cells was bound more strongly on the DEAE-cellulose column than the corresponding pools from the growing cells. Gel filtration of each pool before and after ~-elimination showed that the heparan sulfate from the nuclear and nuclear membrane pools was composed of primarily free chains, whereas the heparan sulfate in all of the other pools was a mixture of proteoglycans and free chains. The heparan sulfate in each pool was cleaved with nitrous acid to obtain mixtures of di-and tetrasaccharides. Analysis of these mixtures showed that the structural features of the heparan sulfates in each pool were different and were altered significantly when the growing cells became confluent. The nuclear-plus-nuclear membrane pools represented 6.5% and 5.4% of the total cell-associated heparan sulfate in the growing cells and the confluent cells, respectively. The structural features of the heparan sulfate in the two nuclear pools were very similar to each other, but were markedly different from those of the heparan sulfate from the other pools or from any previously described heparan sulfate or heparin. The most unusual aspect of these structures was the high content of ~-D-glucuronosyl(2-SO4)--~D-glucosamine-N,o-(SO4)2 disaccharide units in these sequences. The mode of biosynthesis and delivery of these unusual sequences to the nucleus and the potential significance of these observations are discussed.H EPARAN sulfate proteoglycan (HSPG) ~ is a structurally variable polymer which is turned over rapidly in animal cells (2, 64,68,77). Heparan sulfate (HS) is structurally related to heparin, even though the core proteins on which the two polymers are synthesized are different (61, 67). The biosynthesis of heparin and HS appear to follow similar pathways (66,69). Heparin is synthesized as a polymer of repeating o-glucuronic acid (GlcUA)-~N-acetyl-o-glucosamine (GlcNAc) disaccharide units which then undergoes a series of maturation reactions initiated by N-deacetylation, which occurs randomly at some of the GlcNAc residues along the polymer chain, followed by N-sulfation of the resulting Dglucosamine (GlcN) residues. Further maturation, which occurs in the regions around the N-sulfo-D-glucosamine (Glc-NSO3) residues, involves additional N-deacetylation/N-sulfation at GIcNAc residues adjacent to the GlcNSO3 residues, C5 epimerization of some of the GlcUA residues to form Liduronic acid (IdoUA) residues, and o-suifation of some of the GlcNAc and GIcNSO3 residues at C6 and some of the uronic acid residues at C2 (69). The resulting polymer contains blocks of unsulfated disaccharides interspersed with blocks of disaccharides which are sulfated to varying degrees (13,48, 73). HS chains are less highly...

Heparanase-mediated Loss of Nuclear Syndecan-1 Enhances Histone Acetyltransferase (HAT) Activity to Promote Expression of Genes That Drive an Aggressive Tumor Phenotype

“…We then examined whether SST0001 was having a direct effect on HAT activity. This is an important question because SST0001 is composed of a chemically modified heparin (26), and studies have shown that when heparin is added to cells, it can be transported to the nucleus (17,27). Because heparin can inhibit HAT activity (15), it is possible that when SST0001 is added to cells it is transported to the nucleus where it directly inhibits HAT activ-FIGURE 1.…”

Characterization of a Heparan Sulfate Octasaccharide That Binds to Herpes Simplex Virus Type 1 Glycoprotein D

“…The 2-Osulfated glucuronic acid residue is a rare constituent of HS, and was found in HS isolated from the adult human cerebral cortex, a nuclear fraction from hepatocytes, HS from bovine kidney, and heparin from porcine intestines (41)(42)(43). This residue is synthesized by HS 2-O-sulfotransferase, although the enzyme preferably generates 2-O-sulfated iduronic acid (IdoUA2S) (44).…”

Human heparanase nuclear localization and enzymatic activity

“…Several groups have reported the presence of HS chains in the nucleus of various cell types [5][6][7][39][40][41] and demonstrated that HSPGs may regulate the internalization and nuclear uptake of FGF-1 and FGF-2. [7][8][9] It was also suggested that a correlation exists between nuclear localization of HS and the growth rate of hepatoma cells, and that both glypican and biglycan participate in the regulation of C6 glioma cell proliferation and survival through a direct involvement of HSPGs in nuclear processes.…”

“…1,2 HSPGs thus influence a variety of normal and pathological processes involving cell adhesion, migration and invasion. [1][2][3][4] Although presence of HSPGs in the cell nucleus has long been reported, [5][6][7] their biological significance was not clearly elucidated. Several studies have demonstrated the involvement of HS in internalization and nuclear uptake of FGF-1 and FGF-2.…”