Investigation of multiple-dynein transport of melanosomes by non-invasive force measurement using fluctuation unit $\chi$

TL;DR

This study uses a non-invasive fluctuation-based method to reveal that multiple dynein motors cooperatively transport melanosomes in zebrafish melanophores, suggesting a universal organelle transport mechanism.

Contribution

It introduces a novel force measurement approach using fluctuation theorem to study dynein-driven transport in living cells.

Findings

Multiple dyneins cooperate to move a single melanosome.

Force estimation aligns with multiple-motor transport models.

Supports universality of cooperative organelle transport mechanisms.

Abstract

Pigment organelles known as melanosomes disperse or aggregate in a melanophore in response to hormones. These movements are mediated by the microtubule motors kinesin-2 and cytoplasmic dynein. However, the force generation mechanism of dynein, unlike that of kinesin, is not well understood. In this study, to address this issue, we investigated the dynein-mediated aggregation of melanosomes in zebrafish melanophores. We applied the fluctuation theorem of non-equilibrium statistical mechanics to estimate forces acting on melanosomes during transport by dynein, given that the energy of a system is related to its fluctuation. Our results demonstrate that multiple force-producing units cooperatively transport a single melanosome. Since the force is generated by dynein, this suggests that multiple dyneins carry a single melanosome. Cooperative transport has been reported for other organelles; thus, multiple-motor transport may be a universal mechanism for moving organelles within the cell.