Arp2/3 complex and actin dynamics are required for actin-based mitochondrial motility in yeast

The Arp2/3 complex is implicated in actin polymerization-driven movement of Listeria monocytogenes. Here, we find that Arp2p and Arc15p, two subunits of this complex, show tight, actin-independent association with isolated ye ast mitochondria. Arp2p colocalizes with mitochondria, Consistent with this result, we detect Arp2p-dependent formation of actin clouds around mitocho ndria in intact yeast. Cells bearing mutations in ARP2 or ARC15 genes show decreased velocities of mitochondrial movement, loss of all directed moveme nt and defects in mitochondrial morphology. Finally, we observe a decrease in the velocity and extent of mitochondrial movement in yeast in which acti n dynamics are reduced but actin cytoskeletal structure is intact. These re sults support the idea that the movement of mitochondria in yeast is actin polymerization driven and that this movement requires Arp2/3 complex.