Evidence that myosin activity opposes microtubule-based axonal transport of mitochondria

Divya Pathak, Purdue University

Abstract

Neurons transport and position the mitochondria using a combination of saltatory, bidirectional movements and stationary docking. Axonal mitochondria move along microtubules (MTs) using kinesin and dynein motors, but actin and myosin also play a poorly-defined role in their traffic. To ascertain this role, I have used RNA interference to deplete specific myosin motors in cultured Drosophila neurons and quantified the effects on mitochondrial motility. To increase the efficacy of RNAi in primary cultures, a fly strain expressing the C. elegans RNA transporter SID-1 in neurons was used. The neurons expressing this transporter exhibited significantly increased RNAi-mediated knockdown of gene expression compared to neurons not expressing SID-1. Using this system, a significant increase in mitochondrial transport upon myosin V depletion was observed. Mitochondrial mean velocity and duty cycle were augmented in both anterograde and retrograde directions, and the fraction of mitochondrial flux contained in long runs almost doubled for anterograde movement. Myosin VI depletion increased the same movement parameters, but was selective for retrograde movement, while myosin II depletion produced no phenotype. An additional effect of myosin V depletion was an increase in mitochondrial length. These data indicate that myosin V and VI play related but distinct roles in regulating MT-based mitochondrial movement: they disrupt, rather than complement protracted MT-based movements and perhaps initiate or facilitate organelle docking.

Degree

Ph.D.

Advisors

Hollenbeck, Purdue University.

Subject Area

Neurosciences|Cellular biology

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