PIK3CA and Parkinson disease: Overall, an impaired PTEN/PI3K/Akt signaling in PD leading to neuronal cell death can be due to mutations in PD-associated genes regulating Akt signaling [e.g., DJ-1 (84), (Figure 2A)], excessive Akt dephosphorylation, inhibition of Akt activation or oxidative stress (85).