The Type II TGF- Receptor Signals Diverse Responses in Cooperation with the Type I Receptor

Transforming growth factor-β (TGF-β) is prototypic of a large family of cytokines conserved from insects through humans. TGF-β is multipotential, being able to control cell proliferation, differentiation, adhesion, migration, extracellular matrix production, and other activities (for review, see Lyons and Moses 1990; Massagué 1990; Roberts and Sporn 1990). Regulation of these functions is important in tissue development and repair processes. The ability of TGF-β to inhibit progression through the cell cycle and to control cell commitment to terminal differentiation provides unique opportunities to elucidate the molecular events that support these important processes. TGF-β and related cytokines initiate their effects by interacting with membrane receptors, some of which have been molecularly defined during the past year (for review, see Massagué 1992) but whose signaling mechanisms remain practically unknown.