Small Molecule Probes of Mitochondrial Translocases Elucidate PINK1 Trafficking in PINK1/Parkin Regulated Mitophagy

Dysfunctional mitochondria result in many human diseases including some cancers and many metabolic diseases. More recently, momentum has been building to implicate defective mitochondria as a leading cause of neurodegenerative diseases. Because preventions and therapies to treat such diseases are extremely limited and non-efficacious, there remains a very large burden on human health. But before effective therapies can be developed, additional research is needed to understand the underlying mechanisms of disease progression on a molecular level. Approaches to investigate these diseases pathways, such as genetic manipulations and RNAi, are useful but limited in what they can achieve. To alleviate this, we have performed a small molecule screen designed to discover inhibitors of protein import into mitochondria and have applied one of these inhibitors, named MitoBloCK-10, to further clarify a protein pathway involved in autosomal recessive Parkinson’s disease.\tIn this pathway, proteins PINK1 and Parkin work in concert to selectively remove dysfunctional mitochondria from the total cellular population. When either PINK1, which is partially imported into mitochondria, or Parkin, which is recruited to mitochondria by PINK1, is not functioning properly, damaged mitochondria accumulate and this leads to neuronal degradation and Parkinson’s disease. In this study, we use MitoBlock-10, one of the molecules discovered in the screen, to reveal an important role for the mitochondrial import protein TIMM44 in PINK1 trafficking at mitochondria.\tTwo other molecules discovered in the screen are also of interest. DECA, an FDA-approved compound, shows an interesting interaction with PINK1 and offers promise as a therapy for Parkinson’s disease. MitoBloCK-11, a novel molecule, has a protein binding target, Seo1, that was previously believed to exist exclusively at the plasma membrane. This collection of molecules not only increases the tools available for research, it has revealed important insights into PINK1 trafficking and Seo1 localization.