MAPT and Parkinson disease: Interactions of α‐syn and tau proteins have been described in animal models and postmortem brain studies, including colocalization of tau‐positive tangles and α‐syn‐positive Lewy bodies,26, 27 and α‐syn and Aβ1‐42 may have a synergistic relationship.28, 29 A greater understanding of the molecular mechanisms of overlapping proteinopathies and their underlying pathology in PD, along with relevant biomarkers, will contribute to the development and validation of biomarkers used for diagnosis, prognosis, and therapeutic monitoring in PD.