Regulation of the chondroitin/dermatan fine structure by transforming growth factor-β1 through effects on polymer-modifying enzymes

Abstract

The chondroitin/dermatan sulfate proteoglycans (CS/DSPGs), biglycan, decorin, and versican play several important roles in extracellular matrix influencing matrix organization, cell proliferation, and recruitment. Moreover, they bind and regulate growth factors in the extracellular matrix. We have previously shown that cultured human lung fibroblasts treated with transforming growth factor-beta (TGF-beta) alone or in combination with epidermal growth factor and platelet-derived growth factor, increase the production of these PGs. In this report, we describe that the structure of their galactosaminoglycan side chains is altered, albeit there is no alteration of polysaccharide length. The findings showed that iduronic acid content is reduced by 50% in decorin and biglycan, whereas 4-O-sulfation is increased 2-fold in versican. To unravel the mechanism behind these changes, the activities of chondroitin C-5 epimerase and of O-sulfotransferases in cellular fractions prepared from fibroblasts were quantitated, and transcript levels of the relevant sulfotransferases were measured by real time polymerase chain reaction (RT-PCR). The C-5 epimerase activity was reduced by 25% in TGF-beta1 treated cells and 50% in fibroblasts treated with the growth factor combination. No change in activity in dermatan 4-O sulfotransferase was observed, and only a minor decrease in dermatan 4-O-sulfotransferase-1 (D4ST-1) mRNA was observed. On the other hand, chondroitin 4-O sulfotransferase activity increased 2-fold upon TGF-beta1 treatment and 3-fold upon treatment with the growth factor combination. This is in agreement with a 2-fold up-regulation of chondroitin-4-O-sulfotransferase 1 (C4ST-1) mRNA, and no changes in chondroitin-4-O-sulfotransferase 2 (C4ST-2) mRNA. Thus, cellular activity and transcript level correlated well with the changes in the structure of the dermatan/chondroitin sulfate chains.

Chondroitin synthases I, II, III and chondroitin sulfate glucuronyltransferase expression in colorectal cancer

“…A notable finding is that the expression of 4-sulfotransferase isoforms is affected in fibroblasts after treatment by such growth factors (22). However, it remains unclear whether these growth factors affect the expression of chondroitin polymerizing enzymes.…”

Biosynthesis of Dermatan Sulfate

“…The extent of these modifications varies between tissues and seems to be influenced by the core protein structure (16). In addition, both epimerization and sulfation can be affected by growth factors (17).…”

Neuron-specific TGF-β signaling deficiency results in retinal detachment and cataracts in mice

“…The reported synthesis of proteoglycans by embryonic neural retinal cells and photoreceptors [20,21] provides support for the synthesis of chondroitin sulfate by retinal cells in our transgenic mouse model. TGF-β is well known to enhance the synthesis of extracellular matrix components like proteoglycans, collagen, and fibronectin [6,8,12]. Moreover, chondroitin sulfate has been shown to regulate neural patterning in the retina [22], suggesting its role both in retinal adhesion and retinal development.…”

“…Subsequent phosphorylation of Smad proteins and translocation to the nucleus results in the transcriptional activation of specific target genes [11]. One of the major roles of TGF-β is induction of synthesis of extracellular matrix components such as collagens, fibronectin, and chondroitin sulfate proteoglycans [6,8,12].…”