Non-Smad TGF-β signals

During the past 10 years, it has been firmly established that Smad pathways are central mediators of signals from the receptors for transforming growth factor beta (TGF-beta) superfamily members to the nucleus. However, growing biochemical and developmental evidence supports the notion that alternative, non-Smad pathways also participate in TGF-beta signalling. Non-Smad signalling proteins have three general mechanisms by which they contribute to physiological responses to TGF-beta: (1) non-Smad signalling pathways directly modify (e.g. phosphorylate) the Smads and thus modulate the activity of the central effectors; (2) Smads directly interact and modulate the activity of other signalling proteins (e.g.…