HTRA2 and Parkinson disease: Figure 2 also depicts the various PD-associated proteins and their homologous counterparts in yeast, i.e. DJ-1 and its homologue Hsp31 as well as HtrA2 and its orthologue Nma111. Although Winderickx et al., [164] reported the involvement of HtrA2 and DJ-1 in PD through yeast studies, the results were unable to confirm the role of Nma111 in α-synuclein-mediated apoptotic cell death and a protective function of Hsp31 have not yet been demonstrated.