Investigation of Multiple-Dynein Transport of Melanosomes by Non-Invasive Force Measurement using the Fluctuation Theorem

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 [1,2,3] 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 [4]. 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. [1] K. Hayashi, Biophys. Rev. https://doi.org/10.1007/s12551-018-0440-5 (2018). [2] K. Hayashi, S. Hasegawa, T. Sagawa, S. Tasaki and S. Niwa, Chem. Phys. Che. Phys. 20, 3404-3410 (2018). [3] K. Hayashi, S. Tsuchizawa, M. Iwaki and Y. Okada, MBoC, in press (2018). [4] S. Hasegawa, T. Sagawa, K. Ikeda, Y. Okada and K. Hayashi, preprint http://arxiv.org/abs/1808.03469