Figure 1.

Signal Transduction pathways of TGFBs. TGFB dimerization triggers the assembly of a heterodimeric complex between Type I and Type II receptors (TGFBRI and TGFBRII). This permits TGFBRII to trans-phosphorylate TGFBRI that, in turn, activates the receptor-regulated SMADs (SMAD2/3) by phosphorylation. Activated R-SMAD forms a complex with the common SMAD (SMAD4) and together translocate into the nucleus through nucleoporins; the complex interacts with specific SMAD binding elements (SBEs), regulating gene transcriptional responses.