Project 462041

The cell is surrounded by a lipid membrane and contains multiple, distinct organelles, also surrounded by membranes. Different organelles contact each other, forming nanometer (nm)-scale membrane contact sites observed by electron microscopy. Below the ~250 nm limit of visible light to distinguish between two adjacent objects (diffraction barrier), these contacts are therefore difficult to visualize by conventional fluorescence microscopy. Applying machine learning to super-resolution fluorescent microscopy, that breaks the diffraction barrier, we developed approaches to study contacts between two organelles: the endoplasmic reticulum, responsible for the synthesis of cellular proteins, and mitochondria, which generates the energy required for cellular function. Our focus is a protein called Gp78, which induces the formation of a distinct type of mitochondria-endoplasmic reticulum contact (MERC) and also induces the endoplasmic reticulum to engulf damaged mitochondria, resulting in the destruction of the engulfed mitochondria. This latter process, called mitophagy, is important as it destroys damaged mitochondria which produce oxygen radicals harmful to the cell. We will study how Gp78 regulation of MERCs and mitophagy may prevent progression of a cancer to malignancy. We will use our novel super-resolution imaging analysis approach to identify the contacts where Gp78, and other proteins, mediate physical interaction between endoplasmic reticulum and mitochondria. We will also test how loss of these proteins and contacts impacts mitochondrial health and behavior and extend these studies to cells in tumors to determine how these mechanisms affect tumor cell production of harmful oxygen radicals. We will define the mechanisms by which Gp78 induces MERCs and mitophagy and test whether targeting these mechanisms impacts tumor cell production of oxygen radicals.