Histological examination of thoracic flight muscle in these flies revealed evidence of pronounced myopathy in flies expressing mutant dVCP, including CDK inhibitor atrophy of individual muscles and loss of normal sarcomere architecture ( Figure 1F). Ultrastructural examination of muscle tissue by transmission electron microscopy (TEM) revealed

marked morphological abnormalities in mitochondria with extensive megaconia and pleioconia ( Figure 1F). Interestingly, prior phenotypic analysis of flies expressing mutant VCP reported that degeneration was accompanied by reduced cellular ATP levels ( Chang et al., 2011). The mechanism of altered ATP levels was not explored in Chang et al. Nevertheless, the relevance of the altered ATP levels was

nicely demonstrated Bcl 2 inhibitor since artificial manipulation of ATP levels modified the degenerative phenotype ( Chang et al., 2011). The myopathy and specific mitochondrial abnormalities observed in dVCP mutant flies are reminiscent of the phenotypes reported in flies null for PINK1 and Parkin (Greene et al., 2003; Poole et al., 2008). Our interest in a possible connection to these genes was heightened by the fact that a subset of patients with VCP mutations present with parkinsonism or Parkinson’s disease (Kimonis et al., 2008; Spina et al., 2013), a clinical phenotype also associated with mutations in PINK1 and Parkin. PINK1 and Parkin participate in a common pathway that regulates mitochondrial dynamics and serve to maintain mitochondrial quality control (Clark et al., 2006; Narendra et al., 2008, 2010; Park et al., 2006). These observations led us to hypothesize that VCP might be a component of the PINK1/Parkin pathway and contribute to mitochondrial quality control. To test this hypothesis, we performed epistasis studies Niclosamide between VCP, PINK1, and Parkin. We determined that overexpression of VCP rescued the degenerative phenotype associated with PINK1 deficiency, as evidenced by suppression of thoracic indentations ( Figures 2A and 2B) and restoration

of normal locomotor function ( Figure 2C) in PINK1 null (PINK1B9). Furthermore, histological analysis demonstrated that VCP overexpression rescued the mitochondrial phenotype in PINK1 null flies ( Figure 2D). This rescue by VCP is similar to that observed by overexpressing Parkin in PINK1 null flies ( Clark et al., 2006; Park et al., 2006). These results indicate that, like Parkin, VCP functions downstream of PINK1 in the mitochondrial quality-control pathway. In contrast, VCP did not suppress the degenerative phenotype associated with Parkin deficiency ( Figures 2A–2C). These data indicate that VCP functions upstream or in concert with Parkin or, alternatively, independently of Parkin in supporting mitochondrial quality control by PINK1.