Transforming growth factor Β1 influences glycosylation of α1-protease inhibitor in human hepatoma cell lines

Abstract

We have previously shown that changes in acute-phase protein glycosylation result from alterations occurring within hepatocytes as a result of regulation by cytokines, that the glycosylation patterns of proteins secreted by Hep 3B and Hep G2 cells respond differently to the crude mixtures of cytokines found in conditioned medium from LPS-stimulated monocytes, and that interleukin-6 (IL-6) causes increased concanavalin A (Con A) binding ofαl protease inhibitor in Hep 3B cells and decreased Con A binding of this protein in Hep G2 cells. In the present study we found that transforming growth factorΒl (TGF-Β), like IL-6, led to secretion of forms ofαl-protease inhibitor with increased Con A binding in Hep 3B cells, and that IL-6 and TGF-Β in combination were additive. In contrast, in Hep G2 cells, TGF-Β had an effect opposite to that produced by IL-6, leading to secretion of forms ofαl-protease inhibitor with increased Con A binding. When employed in combination with IL-6, TGF-Β abolished the effect of that cytokine. These studies indicate that TGF-Β influences glycosylation of al-protease inhibitor in two human hepatoma cell lines in a manner that can be differentiated from that of IL-6. The identification of TGF-Β as a second defined cytokine capable of influencing glycoprotein glycosylation and the demonstration that the effect of one cytokine can be modulated by another cytokine support the view that changes in glycosylation of plasma proteins are mediated by combinations of cytokines.