Myosin 18A coassembles with nonmuscle myosin 2 to form mixed bipolar filaments

Neil Billington, Jordan R. Beach, Sarah M. Heissler, Kirsten Remmert, Stephanie Guzik-Lendrum, Attila Nagy, Yasuharu Takagi, Lin Shao, Dong Li, Yi Yang, Yingfan Zhang, Melanie Barzik, Eric Betzig, John A. Hammer, James R. Sellers

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34 Citations (Scopus)

Abstract

Class-18 myosins are most closely related to conventional class-2 nonmuscle myosins (NM2). Surprisingly, the purified head domains of Drosophila, mouse, and human myosin 18A (M18A) lack actin-activated ATPase activity and the ability to translocate actin filaments, suggesting that the functions of M18A in vivo do not depend on intrinsic motor activity. M18A has the longest coiled coil of any myosin outside of the class-2 myosins, suggesting that it might form bipolar filaments similar to conventional myosins. To address this possibility, we expressed and purified full-length mouse M18A using the baculovirus/Sf9 system. M18A did not form large bipolar filaments under any of the conditions tested. Instead, M18A formed an ∼65-nm-long bipolar structure with two heads at each end. Importantly, when NM2 was polymerized in the presence of M18A, the two myosins formed mixed bipolar filaments, as evidenced by cosedimentation, electron microscopy, and single-molecule imaging. Moreover, super-resolution imaging of NM2 and M18A using fluorescently tagged proteins and immunostaining of endogenous proteins showed that NM2 and M18A are present together within individual filaments inside living cells. Together, our in vitro and live-cell imaging data argue strongly that M18A coassembles with NM2 into mixed bipolar filaments. M18A could regulate the biophysical properties of these filaments and, by virtue of its extra N- and C-terminal domains, determine the localization and/or molecular interactions of the filaments. Given the numerous, fundamental cellular and developmental roles attributed to NM2, our results have far-reaching biological implications.

Original languageEnglish
Pages (from-to)942-948
Number of pages7
JournalCurrent Biology
Volume25
Issue number7
DOIs
Publication statusPublished - Jan 1 2015

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)

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    Billington, N., Beach, J. R., Heissler, S. M., Remmert, K., Guzik-Lendrum, S., Nagy, A., Takagi, Y., Shao, L., Li, D., Yang, Y., Zhang, Y., Barzik, M., Betzig, E., Hammer, J. A., & Sellers, J. R. (2015). Myosin 18A coassembles with nonmuscle myosin 2 to form mixed bipolar filaments. Current Biology, 25(7), 942-948. https://doi.org/10.1016/j.cub.2015.02.012