Figure 7. Schematic model illustrating potential mechanisms through which PAR2 regulates ALK5 expression and TGF-β signalling.

On the left-hand side, the green arrows indicate the various effects of PAR2 on the TGF-β pathway such as an increase in ALK5 protein abundance, R-Smad phosphorylation, Smad-mediated transcription, target gene expression and cell migration/invasion. On the right-hand side, still hypothetical mechanisms are shown that can lead to an increase in ALK5 protein such as deubiquitylation (eventually resulting in less degradation) or inhibition of a microRNA that targets ALK5 for degradation. The green arrows indicate stimulatory interactions and the red lines inhibitory interactions. The black stippled arrow indicates anterograde transport of ALK5 protein to the cell surface. P, phosphate residue; SBE, Smad binding element; USP, ubiquitin-specific protease.