Rapamycin, an inhibitor of the mammalian target of rapamycin (mTOR) pathway, and its derivatives are among the most studied therapeutic agents for the treatment of neurodegenerative diseases, including PD and HD (Sarkar et al., 2008; Johnson et al., 2013; Villa-Cuesta et al., 2014). Here, MTOR is linked to neurodegenerative disease.