HTRA2 and mitochondrial disease: Proteins that regulate mitochondrial fusion and fission (DRP1 and MFN1), mitophagy (PINK1, Parkin and phosphorylated ubiquitinSer65 (pUbSer65)); mitochondrial chaperones (HSP60 and PHB1), mitochondrial proteases (HTRA2 and LonP1), alongside transcription factors (GPS2 and TFAM) showed a high protein level in 10/11 controls, with a trend for decreased levels among most PD and mitochondrial disease cases (Fig. 3a).