EAPSI: Study of Mitochondrial Interactions at Presynaptic Terminals

Madamba Stephen, New York NY

Investigators

Abstract

Mitochondria are important machines inside cells which play a number of key roles, from being the energy factories of the cell to regulating the process of programmed cell death. A byproduct of energy production is reactive oxygen species (ROS), molecules capable of damaging organelles and leading to further release of ROS. Therefore, cells must maintain a population of healthy, functioning mitochondria. The maintenance mechanisms that have been identified include the recycling of mitochondria and the ongoing division and joining together of mitochondria. While these mechanisms have been well studied in numerous types of cells, they remain poorly understood in neurons, a type of cell of the nervous system. Neurons transmit signals to and from the central nervous system, requiring high amounts of energy, especially at synapses, sites distant from the cell body where there would also be a greater need to remove damaged mitochondria. In collaboration with Professor Michael Ryan at Monash University, an expert in mitochondrial fission and fusion, this project will investigate functional interactions of mitochondria with cellular components in locations of the cell with high metabolic activity. The study of mitochondrial quality control mechanisms in neurons has focused on their occurrence in the cell body, while little is known about how damaged mitochondria are removed from axons and presynaptic terminals. In addition to fission/fusion events and mitophagy, the selective autophagy of mitochondria, trafficking of mitochondria along microtubules may act to replace damaged organelles with healthy ones from the cell body. To study which of these mechanisms are activated in response to oxidative stress, a photoactivatable ROS-producing peptide targeted to mitochondria will be introduced into live cells in which our proteins of interest have been labeled with fluorescent dyes. Using confocal live imaging and super-resolution microscopy, snapshots of presynaptic mitochondria exposed to or unexposed to green light will be generated and compared to assess which factors are involved in the removal of damaged mitochondria. This award, under the East Asia and Pacific Summer Institutes program, supports summer research by a U.S. graduate student and is jointly funded by NSF and the Australian Academy of Science.