Mitochondrial Dynamics: Fusion and Division

Mitochondria are highly dynamic organelles that continuously fuse and divide in highly regulated manners. These activities control number, distribution, and morphology of mitochondria in the cell, and therefore play important roles for diverse mitochondrial functions such as energy production, metabolism, intracellular signaling, and apoptosis. Several neurodegenerative diseases are found to be defective in mitochondrial dynamics, illustrating the importance of these processes for human health. Recent studies have identified key components required for mitochondrial fusion and division, including three dynamin related GTPases, mitofusin (Fzo1p in yeast) and OPA1 (Mgm1p in yeast) for fusion, and Drp1 (Dnm1p in yeast) for division. This chapter describes the phenomena of mitochondrial fusion and mitochondrial division, both of which involve GTPases in a significant role. Finally, it suggests that mitochondria exhibit antagonistic activities of membrane fusion and division, and a balance between these two activities is a key mechanism in the regulation of mitochondrial structure and function. Several components involved in these dynamic processes have been identified. A complete understanding of mechanisms underlying mitochondrial dynamics as well as their physiological roles in different tissues where unique mitochondrial morphologies are taken awaits further studies.