A RAT PITUITARY-TUMOR CELL-LINE (GH(3)) EXPRESSES TYPE-I AND TYPE-II RECEPTORS AND OTHER CELL-SURFACE BINDING PROTEIN(S) FOR TRANSFORMING GROWTH-FACTOR-BETA

A rat pituitary tumor cell line (GH(3)) has been reported to express transforming grow-th factor-beta (TGF-beta) binding components of 70-74 kDa (ligand included), denoted TGF-beta 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-beta superfamily. TGF-beta type I receptor (T beta R-I) complexes of 69-72 kDa formed a heteromeric complex with T beta R-II in GH(3) cells, as detected by immunoprecipitation. In addition, TGF-beta formed complexes of 72-74 kDa, which were different from T beta R-I and the other known type I receptors, and were not dependent on T beta R-II for binding, The GH(3) cells were resistant to the growth inhibitory activity of TGF-beta, but a transcriptional response was activated by TGF-beta in this cell line, presumably through the T beta R-II and T beta R-I complex. These results indicate that GH(3) cells have T beta R-I and T beta R-II and, in addition, other binding protein(s) which form 72-74-kDa complexes with TGF-beta; the function of the latter component(s) remains to be elucidated.