GRM5 and Alzheimer disease: Recently, the roles of the interaction mGluR5 with Aβ and α-synuclein-PrPC complexes in mediating the pathogenesis and progression of AD and PD attract great attention (Overk et al., 2014; Ferreira et al., 2017; Brody and Strittmatter, 2018; Lee et al., 2018).