Forkhead box protein O1 and Forkhead box protein O3a-mediated proteolysis pathway (FoxO1/FoxO3a proteolysis pathway)

The FoxO1/FoxO3a-dependent proteolysis pathway is a central regulatory mechanism for protein degradation in skeletal muscle, primarily operating through the induction of the ubiquitin-proteasome and autophagy-lysosome systems [3]. Under conditions of low insulin or growth factor signaling, the transcription factors Forkhead box protein O1 (FoxO1) and Forkhead box protein O3 (FoxO3a) undergo dephosphorylation and translocate into the nucleus [1, 2]. Once in the nucleus, they upregulate the expression of key E3 ubiquitin ligases, specifically MuRF1 (TRIM63) and Atrogin-1 (FBXO32), which facilitate the polyubiquitination and subsequent degradation of myofibrillar proteins [3, 4]. This pathway is highly active during muscle wasting associated with cancer cachexia, chronic obstructive pulmonary disease (COPD), and aging [7]. Pharmacological targeting of this pathway typically involves small molecule inhibitors like AS1842856 or the activation of upstream Akt signaling to promote FoxO exclusion from the nucleus [5]. However, therapeutic development is challenged by the dual role of FoxO proteins as tumor suppressors and essential regulators of metabolic flexibility [8]. Additionally, FoxO3a specifically regulates the autophagy-lysosome pathway, making it a complex target for selective protein degradation control [7]. Successful modulation of this pathway could provide significant benefits for patients suffering from debilitating muscle loss, though tissue-specific delivery remains a major hurdle.

Other names

FoxO-mediated muscle atrophyFoxO-dependent ubiquitin-proteasome pathwayFoxO-autophagy axisAtrogene signalingFoxO1/3a-mediated protein degradation

Inhibition of FoxO-mediated transcription of E3 ubiquitin ligases (MuRF1, Atrogin-1) and autophagy-related genes to prevent protein degradation in skeletal muscle.