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 0.2-0.33 microm/s, retrograde movement at velocities of 0.26-0.51 microm/s, and no net anterograde or retrograde movement. In all cases, motile mitochondria were associated with actin cables undergoing retrograde flow at velocities of 0.18-0.62 microm/s. Destabilization of actin cables or mutations of the mitochore blocked all mitochondrial movements. In contrast, mutations in the Arp2/3 complex affected anterograde but not retrograde mitochondrial movements.


CONCLUSIONS
Actin cables are required for movement of mitochondria, secretory vesicles, mRNA, and spindle alignment elements in yeast. We provide the first direct evidence that one of the proposed cargos use actin cables as tracks. In the case of mitochondrial inheritance, anterograde movement drives transfer of the organelle from mothers to buds, while retrograde movement contributes to retention of the organelle in mother cells. Interaction of mitochondria with actin cables is required for anterograde and retrograde movement. In contrast, force generation on mitochondria is required only for anterograde movement. Finally, we propose a novel mechanism in which actin cables serve as "conveyor belts" that drive retrograde organelle movement.
Fehrenbacher
Kammy L
KL
Department of Anatomy and Cell Biology, Columbia University, College of Physicians and Surgeons, New York, New York 10032, USA.
Yang
Hyeong-Cheol
HC
Gay
Anna Card
AC
Huckaba
Thomas M
TM
Pon
Liza A
LA
D000199:Actins / Q000378:metabolism*; D001692:Biological Transport; D015153:Blotting, Western; D002453:Cell Cycle / Q000502:physiology*; D017931:DNA Primers; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008164:Luminescent Proteins; D008840:Microfilament Proteins / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000378:metabolism / Q000502:physiology*; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D000097573:Red Fluorescent Protein
D000199:Actins; D017931:DNA Primers; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins; D008840:Microfilament Proteins; D029701:Saccharomyces cerevisiae Proteins; D000097573:Red Fluorescent Protein; C110542:ABP140 protein, S cerevisiae