Studies of the spatiotemporal dynamics and mechanisms behind the role of class V myosins on the mitochondria

Abstract

Mitochondrial morphology and quality control are dependent on the mitochondrial fission and fusion dynamics, which requires dynamin-like GTPases, coordinated activity of mitochondria- ER contact sites and the actin cytoskeleton, along with actin regulatory proteins and molecular motors. Impairment of the balance between fission and fusion results in aging, neurodegenerative diseases and tumorigenesis, highlighting the importance of mitochondrial dynamics for cellular homeostasis and overall health. In ongoing work, we showed that knockdown of myosin-Va in melanoma cells results in increased respiratory rates, consistent with reversal of the Warburg effect, and reduced mitochondrial fission with correspondingly elongated mitochondria. Interestingly, myosin-Va interacts with the mitochondrial outer membrane protein Spire1C, an actin-nucleating protein implicated in mitochondrial fission, and is recruited to the mitochondrial outer membrane through this interaction. Finally, induction of mitochondrial fission correlates with an increase of myosin-Va recruitment to mitochondria, and myosin-Va localizes to mitochondrial fission sites immediately adjacent to Drp1 punctae. Consistently, Drp1, as well as Spire1C, is specifically pulled-down from cell lysates by myosin-Va tail protein. Therefore, our data indicate that myosin-Va facilitates mitochondrial fission, although we have not yet elucidated the molecular mechanisms. In this BEPE project, we propose to use advanced molecular and cellular techniques, such as high resolution live microscopy, CRISPR knockout cells and co-expression of fluorescently tagged-proteins to accurately determine the underlying mechanisms of myosin-Va function in mitochondrial fission, which will be supported by the extensive and specialized experience in mitochondrial dynamics of Dr. Uri Manor, in the Salk Institute, at La Jolla, California. (AU)