Myosin 18A Coassembles with Nonmuscle Myosin 2 to Form Mixed Bipolar Filaments

Abstract

Nonmusclemyosin 2 (NM-2) powers cell motility and tissue morphogenesis by assembling into bipolar filaments that interact with actin. Although the enzymatic properties of purified NM-2 motor fragments have been determined, the emergent properties of filament ensembles are unknown. Using single myosin filament in vitro motility assays, we report fundamental differences in filaments formed of different NM-2 motors. Filaments consisting of NM2-B moved processively along actin, while under identical conditions, NM2-A filaments did not. By more closely mimicking the physiological milieu, either by increasing solution viscosity or by co-polymerization with NM2-B, NM2-A containing filaments moved processively. Our data demonstrate that both the kinetic and mechanical properties of these two myosins, in addition to the stochiometry of NM-2 subunits, can tune filament mechanical output. We propose altering NM-2 filament composition is a general cellular strategy for tailoring force production of filaments to specific functions, such as maintaining tension or remodeling actin.

Re‐evaluating the roles of myosin 18Aα and F‐actin in determining Golgi morphology

“…1, Panel C and D). As expected from previous work (Billington et al 2015, Hsu et al 2010, Mori et al 2005, Tan et al 2008, both antibodies robustly label sub-nuclear actin stress fibers (Fig. 2, Panels A1-A3 and B1-B3; see inside dashed area) 8 and actin-rich lamella (Fig.…”

“…Z-stacks of cells collected with Zeiss Airyscan technology showed strong localization of EGFP-M18Aα at the base of the cell (Fig. 3, Panels A1 and A2), where it is known to co-localize with NM2 in ventral and sub-nuclear stress fibers (Billington et al 2015, Hsu et al 2010, Tan et al 2008. As expected, these ventral sections contained little or no signal for the cis-Golgi (Fig.…”

Cytoskeletal control of B cell responses to antigens

“…Therefore, myosin not only contracts, but also remodels the cortex 27,28 . In addition, myosin can induce flows of free actin filaments into aster-like formations 29,30 , and potentially transport proteins via co-assembly with the cargo-binding protein MYO18A 31 .…”

How myosin organization of the actin cytoskeleton contributes to the cancer phenotype

“…From their sequence similarity, it is likely that MYO18B does not have an active motor domain either. MYO18A contains a long region of coiled coil, but has been shown to be unable to form filaments [63]. However, it can co-polymerise with filamentous NM2A through its coiled-coil domain, and this interaction reduces the number of NM2A molecules in, and thus the length of, the NM2A filaments [63].…”

“…MYO18A contains a long region of coiled coil, but has been shown to be unable to form filaments [63]. However, it can co-polymerise with filamentous NM2A through its coiled-coil domain, and this interaction reduces the number of NM2A molecules in, and thus the length of, the NM2A filaments [63]. The N-terminal PDZ domain of MYO18A binds to membrane proteins that can localize NM2A filaments to the plasma membrane [63] (Fig.…”