Notably, we found the novel Rab3b interaction-mediated enrichment of the peptidyl-cysteine methylation pathway among all other PD-ENS interactions, where Rab3b is a common protein interacting with other Rabs and is native to the optic nerve and brain stem, emphasizing the epigenetic potentials of Rab interactions in PD pathology as methylation is one of the deriving reactions for epigenetic changes. Here, RAB3B is linked to Parkinson disease.