FIGURE 1.

The TGF beta SMAD-dependent signaling pathway. The diagram shows some of the major components of the TGFβ signaling pathway. SMAD-dependents signal transduction is initiated with the binding of the ligands (e.g., TGFβ, BMP, activins etc.) to the serine/threonine type II receptor that phosphorylates and activates the type I receptor which causes dimerization of the type II and type I receptors in a heterotetrameric complex. The signal is then propagated to the nucleus through phosphorylation of SMAD transcription factors. The image represents only few of the ligands/receptors/SMADs possible signal transduction combinations.