MAPK3 and Parkinson disease: Similar to JNK, ERK1/2 activity on the mitochondria has been reported in the hippocampus,60 implicated in PD,61 and is associated with the post‐translational modification of Bcl‐2 family members 62 and organelle physiology.63, 64 Although ERK1/2 activity generally is thought to be pro‐survival, prolonged ERK1/2 signaling can be linked to cell death as well.62 ERK1/2 signaling outcomes are stimulus‐ and cell‐type‐dependent, as is the case with most MAPKs.