Characterization of the molecular mechanism involved in the activation of hyaluronan synthetase by platelet-derived growth factor in human mesothelial cells

Abstract

The molecular mechanism involved in the stimulation of hyaluronan synthetase in normal human mesothelial cells was investigated. Exposure of mesothelial cells to platelet-derived growth factor (PDGF)-BB stimulated hyaluronan synthetase activity, measured in isolated membrane preparations, as well as hyaluronan secretion into the medium. The effect on hyaluronan synthetase was maximal after 6 h of treatment. In contrast, the stimulatory effect of transforming growth factor-beta 1 reached a maximum after 24 h. The stimulatory effect of PDGF-BB was inhibited by cycloheximide. The phosphotyrosine phosphatase inhibitor vanadate was found to stimulate hyaluronan synthetase activity, and to potentiate the effect of PDGF-BB. The protein kinase C (PKC) stimulator phorbol 12-myristate 13-acetate (PMA) also stimulated hyaluronan synthetase; furthermore, depletion of PKC by preincubation of the cells with PMA led to an inhibition of the PDGF-BB-induced stimulation of hyaluronan synthetase activity. Thus the PDGF-BB-induced stimulation of hyaluronan synthetase activity is dependent on protein synthesis and involves tyrosine phosphorylation and activation of PKC.