Ceramide metabolism in mitochondria for the induction of cancer cell death by mitophagy
My preliminary data suggest that one of the ceramide-dependent tumor suppression mechanisms in HNSCC includes lethal mitophagy. Mitochondrial ceramide plays a key role in the process by acting as a receptor for LC3-II, a protein component of autophagosomes. This binding results in a specific targeting of autophagosomes to mitochondria and leads to a cell death. This mitochondria ceramide accumulation is not the result of ER-Mitochondrial ceramide transport but rather a product of CerS1 translocated to mitochondria. This translocation depends on the interaction with the small cytosolic protein p17, which function never was described before. Therefore, we hypothesized that translocation of CerS1 from ER to mitochondria is regulated by dynamic interaction of CerS1 with the p17 and this interaction results in C18-ceramide synthesis on the outer membrane of mitochondria for induction of mitophagy and cell death. These novel hypotheses will be tested in two Specific Aims: Aim 1. To define the molecular and biochemical details of mitochondrial translocation of CerS1 from ER to induce mitophagy. Aim 2. To establish role of P17 protein in regulating CerS1 mitochondrial translocation for the induction of C18-ceramide-dependent mitophagy and cell death. This application is focused on a novel mechanism of how ceramide induces cancer cell death, specifically on the newly discovered regulator of ceramide-dependent mitophagy, protein PERMIT/p 17. Since our data suggest, that pP17 can function as a tumor suppressor, detailed understanding of the mechanism will provide important knowledge to develop strategies to improve cancer therapeutics by inducing ceramide-dependent mitophagy. Moreover, PERMIT/p17 might have broader significance as a regulator of mitochondrial lipid metabolism and mitophagy signaling, where maintenance of impaired ceramide-dependent mitophagy might also be involved in various other diseases such as neurodegenerative disorders (Parkinson's decease), cardiomyopathy and/or, diabetes. Results obtained from these studies will help design a new R01 for my independent research. I will utilize Lipidomics and Protein Cores in my studies with collaborations of Drs. Ogretmen, Cowart, Bielawska.