The Role of dMiro in the Distribution and Health of Mitochondria

Abstract

In neurons, regions of high energy demand, like synapses, can be far away from the cell body. Therefore, neurons require efficient mitochondrial transport for maintaining synaptic function and preventing degeneration. Miro is a protein that has been found to be necessary for proper distribution of mitochondria into axons and dendrites of neurons. Miro has an N-terminal GTPase domain (G1), a C-terminal GTPase domain (G2), two calcium-binding EF-hand domains, a variable domain of unknown function, and a transmembrane domain that anchors the protein to the outer mitochondrial membrane. This project examines two main questions concerning the role of Drosophila Miro (dMiro) for mitochondrial transport. First, it examines whether the potentially constitutively active mutations A20V in the G1 domain and K455V in the G2 domain of dMiro affect kinetics of mitochondrial transport. Second, it examines the potential role of the variable domain of dMiro for mitochondrial transport, function, and morphology. I found that the A20V mutation in the G1 domain had no significant effects on the kinetics of mitochondrial transport, even though loss-of-function mutations of the domain abolished the distribution of mitochondria into axons and dendrites. Furthermore, the K455V in the G2 domain had no effect on transport, and did not modulate the function of the G1 domain. Finally, I found that the variable domain of dMiro confers different functional characteristics to the three different isoforms of dMiro. Specifically, I found that the medium dMiro isoform interacts differently with the mitochondrial fusion protein Marf.