A rat pituitary tumor cell line (GH3) expresses type I and type II receptors and other cell surface binding protein(s) for transforming growth factor-β

Abstract

A rat pituitary tumor cell line (GH3) has been reported to express transforming growth factor-β (TGF-β) binding components of 70-74 kDa (ligand included), denoted TGF-β type IV receptor. We investigated whether the type IV receptor corresponds to any of the recently cloned type I receptors for proteins in the TGF-β superfamily. TGF-β type I receptor (TβR-I) complexes of 69-72 kDa formed a heteromeric complex with TβR-II in GH3 cells, as detected by immunoprecipitation. In addition, TGF-β formed complexes of 72-74 kDa, which were different from TβR-I and the other known type I receptors, and were not dependent on TβR-II for binding. The GH3 cells were resistant to the growth inhibitory activity of TGF-β, but a transcriptional response was activated by TGF-β in this cell line, presumably through the TβR-II and TβR-I complex. These results indicate that GH3 cells have TβR-I and TβR-II and, in addition, other binding protein(s) which form 72-74-kDa complexes with TGF-β; the function of the latter component(s) remains to be elucidated.