Self-organization of actin networks by a monomeric myosin

Saczko-Brack, Dario; Warchol, Ewa; Rogez, Benoit; Kröss, Markus; Heissler, Sarah M.; Sellers, James R.; Batters, Christopher und Veigel, Claudia (2016): Self-organization of actin networks by a monomeric myosin. In: Proceedings of the National Academy of Sciences of the United States of America, Bd. 113, Nr. 52, E8387-E8395

Abstract

The organization of actomyosin networks lies at the center of many types of cellular motility, including cell polarization and collective cell migration during development and morphogenesis. Myosin-IXa is critically involved in these processes. Using total internal reflection fluorescence microscopy, we resolved actin bundles assembled by myosin-IXa. Electron microscopic data revealed that the bundles consisted of highly ordered lattices with parallel actin polarity. The myosin-IXa motor domains aligned across the network, forming crosslinks at a repeat distance of precisely 36 nm, matching the helical repeat of actin. Single-particle image processing resolved three distinct conformations of myosin-IXa in the absence of nucleotide. Using cross-correlation of a modeled actomyosin crystal structure, we identified sites of additional mass, which can only be accounted for by the large insert in loop 2 exclusively found in the motor domain of class IX myosins. We show that the large insert in loop 2 binds calmodulin and creates two coordinated actin-binding sites that constrain the actomyosin interactions generating the actin lattices. The actin lattices introduce orientated tracks at specific sites in the cell, which might install platforms allowing Rho-GTPase-activating protein (RhoGAP) activity to be focused at a definite locus. In addition, the lattices might introduce amyosin-related, force-sensing mechanism into the cytoskeleton in cell polarization and collective cell migration.

• Dokumententyp: Zeitschriftenartikel
• Fakultät: Medizin
• Themengebiete: 600 Technik, Medizin, angewandte Wissenschaften > 610 Medizin und Gesundheit
• ISSN: 0027-8424
• Sprache: Englisch