TGF-beta signaling from receptors to the nucleus.

In the past three years, a novel signal transduction pathway downstream of the transforming growth factor-beta (TGF-beta) superfamily receptor serine-threonine kinases has been shown to be mediated by a family of latent transcription factors called 'Smads'. These proteins mediate a short-circuited pathway in which a set of receptor-activated Smads are phosphorylated directly by the receptor kinase and then translocate to the nucleus complexed to the common mediator, Smad4, to participate in transcriptional complexes. Smads 2 and 3 mediate signals predominantly from the TGF-beta receptors.