Fig. 4.

Overview of the myostatin (Mstn) pathway. The schematic shows that Mstn upregulates genes coding for components of the ubiquitin-proteasome pathway via FOXO and Smad3 signaling pathways. Additionally, the increased level of FOXO transcription factors decreases protein synthesis (see Fig. 3B). ActRIIB, activin receptor type IIB. See text for description. [Reproduced, with permission, from Ref. 33.]