HSPA4 and Parkinson disease: Such substrates of Hsp70 proteins include mutant huntingtin (mHTT) in HD and other polyQ diseases, α-synuclein in PD, amyloid-β (Aβ) and hyperphosphorylated tau in AD, and mutant SOD1 in ALS (Choo et al., 2004; Dedmon et al., 2005; Liu et al., 2005; Evans et al., 2006; Dompierre et al., 2007; Luk et al., 2008).