Cellular heparan sulfate negatively modulates transforming growth factor-beta1 (TGF-beta1) responsiveness in epithelial cells.
Cell-surface proteoglycans have been shown to modulate transforming growth factor (TGF)-beta responsiveness in epithelial cells and other cell types. However, the proteoglycan (heparan sulfate or chondroitin sulfate) involved in modulation of TGF-beta responsiveness and the mechanism by which it modulates TGF-beta responsiveness remain unknown. Here we demonstrate that TGF-beta1 induces transcriptional activation of plasminogen activator inhibitor-1 (PAI-1) and growth inhibition more potently in CHO cell mutants deficient in heparan sulfate (CHO-677 cells) than in wild-type CHO-K1 cells. 125I-TGF-beta1 affinity labeling analysis of cell-surface TGF-beta receptors reveals that CHO-K1 and CHO-677 cells exhibit low (<1) and high (>1) ratios of 125I-TGF-beta1 binding to TbetaR-II and TbetaR-I, respectively. Receptor-bound 125I-TGF-beta1 undergoes nystatin-inhibitable rapid degradation in CHO-K1 cells but not in CHO-677 cells. In Mv1Lu cells (which, like CHO-K1 cells, exhibit nystatin-inhibitable rapid degradation of receptor-bound 125I-TGF-beta1), treatment with heparitinase or a heparan sulfate biosynthesis inhibitor results in a change from a low (<1) to a high (>1) ratio of 125I-TGF-beta1 binding to TbetaR-II and TbetaR-I and enhanced TGF-beta1-induced transcriptional activation of PAI-1. Sucrose density gradient analysis indicates that a significant fraction of TbetaR-I and TbetaR-II is localized in caveolae/lipid-raft fractions in CHO-K1 and Mv1Lu cells whereas the majority of the TGF-beta receptors are localized in non-lipid-raft fractions in CHO-677 cells. These results suggest that heparan sulfate negatively modulates TGF-beta1 responsiveness by decreasing the ratio of TGF-beta1 binding to TbetaR-II and TbetaR-I, facilitating caveolae/lipid-raft-mediated endocytosis and rapid degradation of TGF-beta1, thus diminishing non-lipid-raft-mediated endocytosis and signaling of TGF-beta1 in these epithelial cells.
Chen
Chun-Lin
CL
Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, Missouri 63104, USA.
Huang
Shuan Shian
SS
Huang
Jung San
JS
D030201:Activin Receptors, Type I / Q000378:metabolism; D000818:Animals; D016466:CHO Cells / Q000187:drug effects / Q000378:metabolism; D021941:Caveolae / Q000378:metabolism; D049109:Cell Proliferation; D006224:Cricetinae; D004705:Endocytosis; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism*; D006497:Heparan Sulfate / Q000378:metabolism*; D008168:Lung / Q000166:cytology; D009761:Nystatin / Q000494:pharmacology; D017395:Plasminogen Activator Inhibitor 1 / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D000077293:Receptor, Transforming Growth Factor-beta Type I; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism; D013936:Thymidine / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism*; D053773:Transforming Growth Factor beta1
D030201:Activin Receptors, Type I; D006497:Heparan Sulfate; D009761:Nystatin; D017395:Plasminogen Activator Inhibitor 1; D017346:Protein Serine-Threonine Kinases; D000077293:Receptor, Transforming Growth Factor-beta Type I; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta; D013936:Thymidine; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1