ER stress-induced apoptosis is implicated in various pathological conditions, but the mechanisms of H. erinaceus mycelium on the suppression of oxidative stress and JNK/p38 MAPK as well as Fas, Bax and CHOP protein expression, which confer neuroprotection in PD involving ER stress–mediated signaling to neuron apoptotic pathways, remain unclear. The gene discussed is DDIT3; the disease is Parkinson disease.