RAPGEF4 and muscle atrophy: 2005). Also, PDE4D expression was reported to serve as a major modulator of intracellular cAMP levels in skeletal muscle (Lania et al. 1998; McCahill et al. 2008; Joshi et al. 2014). More importantly, PDE inhibition with torbafylline, a nonselective PDE inhibitor, attenuates burn‐induced skeletal muscle atrophy through the PDE4/cAMP/Epac/phosphoinositol 3‐kinase (PI3K)/Akt/mTOR pathway in vivo (Joshi et al. 2014).