RHEB and Parkinson disease: These data suggested that AEG-1, which is significantly reduced in the SN of patients with PD, is an important endogenous factor that protects nigral DA neurons from neurotoxicity and that this protection by the anti-apoptotic effects of neuronal AEG-1 enhances the restoration of the disrupted nigrostriatal DA system (Fig. 6), as shown by the effects of Rheb(S16H) administration in the neurotoxin model of PD (Fig. 5).