Organelles are transported on sliding microtubules in Reticulomyxa

Area of Science:

• Cell Biology
• Cytoskeletal Dynamics
• Intracellular Transport

Background:

• Organelles and plasma membrane domains move along Reticulomyxa's microtubule cytoskeleton.
• Previous studies suggested a shared enzymatic basis and cytoplasmic dynein power source for organelle and cell surface transport.
• Microtubule motility complicates analysis due to bidirectional sliding.

Purpose of the Study:

• To resolve the frame-of-reference problem in Reticulomyxa motility.
• To differentiate the contributions of microtubule sliding versus organelle translocation.
• To understand the mechanism of bidirectional organelle translocation.

Main Methods:

• Utilized laser ablation to sever microtubule bundles in lysed Reticulomyxa networks.
• Examined reactivated motility in isolated microtubule fragments.
• Analyzed organelle movement relative to ablated microtubule segments.

Main Results:

• The majority of organelles remained attached to microtubule fragments and moved with them.
• Organelle movement ceased when microtubule sliding stopped (1-2 min).
• Microtubule sliding could not be reactivated after cessation.

Conclusions:

• Reticulomyxa organelle transport is primarily driven by microtubule sliding, not movement along microtubules.
• The sliding microtubules, to which organelles are attached, are the main drivers of translocation.
• Cytoplasmic dynein likely powers the microtubule sliding mechanism.