Figure 2.

Transforming growth factor β (TGF-β) cross talks to NF-κB and mitogen-activated protein (MAP) kinase pathways. TGF-β receptors activate p38 and c-Jun amino-terminal kinase (JNK) MAPK pathways and NF-κB pathways through receptor-associated factor (TRAF4) or TRAF6 and TGF-β-activated kinase 1 (TAK1), and Ras-Erk MAPK through Grb2 and Shc. The activated Ras-Erk MAPK and p38 pathways can trigger activation of TACE, leading to cleavage of TβRI, and phosphorylation of Smads in the linker region, sequestering it in the cytoplasm and promoting its degradation.