mt-Keima detects PINK1/Parkin-mitophagy in vivo; mito-QC does not Yi-Ting Liu1†, Danielle A. Sliter2†, Mario K. Shammas1, Xiaoping Huang1, Hannah Calvelli1, Chunxin Wang2, Derek P. Narendra1 PINK1 and Parkin, which cause Parkinson’s disease when mutated, form a quality control mitophagy pathway that is well-characterized in cultured cells (1). The extent to which PINK1/Parkin contributes to mitophagy in vivo, however, is controversial. This is due in large part to conflicting results from studies using one of two mitophagy reporters: mt-Keima or mito-QC (2–6). Studies using mt-Keima have generally detected PINK1/Parkin mitophagy in vivo, whereas those using mito-QC generally have not. Here, we directly compared the performance of mito-QC and mt-Keima in cell culture and in mice subjected to a PINK1/Parkin activating stress. We found that mito-QC was less sensitive than mt-Keima for mitophagy, and that this difference was more pronounced for PINK1/Parkin-dependent mitophagy. These findings suggest that mito-QC’s poor sensitivity may account for conflicting reports of PINK1/Parkin mitophagy in vivo and caution against using mito-QC as a reporter for PINK1/Parkin mitophagy. References 1. Youle RJ, Narendra DP. Mechanisms of mitophagy. Nat Rev Mol Cell Biol 2011; 12:9–14. 2. Katayama H, Kogure T, Mizushima N, Yoshimori T, Miyawaki A. A sensitive and quantitative technique for detecting autophagic events based on lysosomal delivery. Chem Biol 2011; 18:1042–52. 3. Sun N, Yun J, Liu J, Malide D, Liu C, Rovira II, Holmström KM, Fergusson MM, Yoo YH, Combs CA, et al. Measuring In Vivo Mitophagy. Mol Cell 2015; 60:685–96. 4. Allen GFG, Toth R, James J, Ganley IG. Loss of iron triggers PINK1/Parkin-independent mitophagy. EMBO Rep 2013; 14:1127–35. 5. McWilliams TG, Prescott AR, Allen GFG, Tamjar J, Munson MJ, Thomson C, Muqit MMK, Ganley IG. mito-QC illuminates mitophagy and mitochondrial architecture in vivo. J Cell Biol 2016; 214:333–45. 6. McWilliams TG, Prescott AR, Montava-Garriga L, Ball G, Singh F, Barini E, Muqit MMK, Brooks SP, Ganley IG. Basal Mitophagy Occurs Independently of PINK1 in Mouse Tissues of High Metabolic Demand. Cell Metab 2018; 27:439-449.e5. Funding source This work was supported by the Intramural Research Program of the NINDS, National Institutes of Health.