Transforming growth factor beta receptor expression in cultured porcine granulosa cells

By using primary cultures of porcine granulosa cells as a model, TGF beta receptors have been identified and characterized through three different approaches including cross-linking experiments, Western- and Northern-blotting analysis. In cross-linking experiments, labeled TGF beta was shown to bind to four different molecular species of 300, 168, 72 and 58 kDa. The 300-kDa species may correspond to beta-glycan, while the 72- and 58-kDa correspond to TGF beta type II and I receptors, respectively. The presence of these receptors was further demonstrated by Western-blotting analysis using specific polyclonal antibodies. Finally, both the expression of beta-glycan, type II and type I mRNA, was confirmed through Northern-blotting analysis as shown by the presence of 6.4, 4.6 and 5.8 kb mRNA, respectively. Additionally, we detected another TGF beta binding protein of 168 kDa which remains to be identified. Together, our present data indicate that the regulatory action of TGF beta on cultured granulosa cells previously reported in several laboratories may be mediated through the receptors identified here.