Abstract
The cytoskeleton plays a critical role in regulating mitochondria distribution. Similar to axonal mitochondria, the fission yeast mitochondria are distributed by the microtubule cytoskeleton, but this is regulated by a motor-independent mechanism depending on the microtubule associated protein mmb1p as the absence of mmb1p causes mitochondria aggregation. In this study, using a series of chimeric proteins to control the subcellular localization and motility of mitochondria, we show that a chimeric molecule containing a microtubule binding domain and the mitochondria outer membrane protein tom22p can restore the normal interconnected mitochondria network in mmb1-deletion (mmb1∆) cells. In contrast, increasing the motility of mitochondria by using a chimeric molecule containing a kinesin motor domain and tom22p cannot rescue mitochondria aggregation defects in mmb1∆ cells. Intriguingly a chimeric molecule carrying an actin binding domain and tom22p results in mitochondria associated with actin filaments at the actomyosin ring during mitosis, leading to cytokinesis defects. These findings suggest that the passive motor-independent microtubule-based mechanism is the major contributor to mitochondria distribution in wild type fission yeast cells. Hence, we establish that attachment to microtubules, but not kinesin-dependent movement and the actin cytoskeleton, is required and crucial for proper mitochondria distribution in fission yeast.
Highlights
Yeast likely employs a passive motor-independent microtubule-based mechanism to regulate mitochondria positioning and serves as an excellent model organism for dissection of the various regulatory mechanisms underlying mitochondria distribution
Forcing mitochondria to associate with actin filaments does not rescue the mitochondria aggregation phenotype in mmb1∆ cells, and instead, these mitochondria mainly concentrate at the actomyosin ring, causing cytokinesis defects
Using a synthetic biology approach, we demonstrate that a chimeric protein containing mitochondria and microtubule binding domains can replace mmb1p to distribute mitochondria in fission yeast whereas motile mitochondria and targeting mitochondria to actin filaments impairs mitochondria distribution and causes cytokinesis defects, respectively
Summary
Yeast likely employs a passive motor-independent microtubule-based mechanism to regulate mitochondria positioning and serves as an excellent model organism for dissection of the various regulatory mechanisms underlying mitochondria distribution. Whether the motor-independent microtubule-based mechanism is sufficient for mitochondria distribution in fission yeast remains unclear. We have engineered and employed a series of chimeric proteins, capable of targeting mitochondria to microtubules or to actin filaments and transporting mitochondria along microtubules, respectively, to dissect the various mechanisms in regulating mitochondria distribution in fission yeast. Forcing mitochondria to associate with actin filaments does not rescue the mitochondria aggregation phenotype in mmb1∆ cells, and instead, these mitochondria mainly concentrate at the actomyosin ring, causing cytokinesis defects. This study demonstrates that the passive motor-independent microtubule-based mechanism is the major contributor to mitochondria distribution in fission yeast
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