A role for Jsn1p in recruiting the Arp2/3 complex to mitochondria in budding yeast.

Although the Arp2/3 complex localizes to the leading edge of motile cells, endocytic structures, and mitochondria in budding yeast, the mechanism for targeting the Arp2/3 complex to different regions in the cell is not well understood. We find that Jsn1p, a member of the PUF family of proteins, facilitates association of Arp2/3 complex to yeast mitochondria. Jsn1p localizes to punctate structures that align along mitochondria, cofractionates with a mitochondrial marker protein during subcellular fractionation, and is both protease sensitive and carbonate extractable in isolated mitochondria.

Mitochondrial movement and inheritance in budding yeast.

Mitochondria are essential organelles that perform fundamental cellular functions including aerobic energy mobilization, fatty acid oxidation, amino acid metabolism, heme biosynthesis and apoptosis. Mitochondria cannot be synthesized de novo. Therefore, the inheritance of this organelle is an essential part of the cell cycle; that is, daughter cells that do not inherit mitochondria will not survive.

Live cell imaging of mitochondrial movement along actin cables in budding yeast.

Background: Mitochondrial inheritance is essential for cell division. In budding yeast, mitochondrial movement from mother to daughter requires (1) actin cables, F-actin bundles that undergo retrograde movement during elongation from buds into mother cells; (2) the mitochore, a mitochondrial protein complex implicated in linking mitochondria to actin cables; and (3) Arp2/3 complex-mediated force generation on mitochondria.

Results: We observed three new classes of mitochondrial motility: anterograde movement at velocities of 0.

Taking the A-train: actin-based force generators and organelle targeting.

The actin-driven process of cytoplasmic streaming in plant cells is widely believed to be the earliest documented example of cytoskeleton-driven organelle movement. In the decades since these seminal findings, two mechanisms of actin-based intracellular movement have been identified in multiple cell types: one is myosin dependent and the other is dependent upon the Arp2/3 complex for actin nucleation and polymerization. Here, we describe mechanisms of force generation and directed movement that use the actin cytoskeleton, as well as those that target actin-dependent force generators to different subcellular compartments.

Actin comet tails, endosomes and endosymbionts.

The Arp2/3 complex consists of seven highly conserved and tightly associated subunits, two of which are the actin-related proteins Arp2 and Arp3. One of the best-studied functions of the Arp2/3 complex is to stimulate actin nucleation and force production at the leading edge of motile cells. What is now clear is that Arp2/3-complex-mediated force production drives many intracellular movements, including movement of bacterial pathogens in infected host cells, internalization of extracellular materials via phagocytosis and endocytosis, and movement of mitochondria during cell division in budding yeast.