Myosin-1C associates with microtubules and stabilizes the mitotic spindle during cell division

Abstract

SummaryThe mitotic spindle in eukaryotic cells is composed of a bipolar array of microtubules (MTs) and associated proteins that are required during mitosis for the correct partitioning of the two sets of chromosomes to the daughter cells. In addition to the well-established functions of MT-associated proteins (MAPs) and MT-based motors in cell division, there is increasing evidence that the F-actin-based myosin motors are important mediators of F-actin-MT interactions during mitosis. Here, we report the functional characterization of the long-tailed class-1 myosin myosin-1C from Dictyostelium discoideum during mitosis. Our data reveal that myosin-1C binds to MTs and has a role in maintenance of spindle stability for accurate chromosome separation. Both myosin-1C motor function and taildomain-mediated MT-F-actin interactions are required for the cell-cycle-dependent relocalization of the protein from the cell periphery to the spindle. We show that the association of myosin-1C with MTs is mediated through the tail domain. The myosin-1C tail can inhibit kinesin motor activity, increase the stability of MTs, and form crosslinks between MTs and F-actin. These data illustrate that myosin-1C is involved in the regulation of MT function during mitosis in D. discoideum.

Localized accumulation of tubulin during semi-open mitosis in theCaenorhabditis elegansembryo

“…Another dynein subunit, dynein light chain roadblock type (DYRB-1), and nonmuscle myosin (NMY-2), also accumulated in the nascent spindle region (Figure 1B and Table S1). The role of DYRB-1 and NMY-2 in the spindle assembly remains unclear, but it has been reported that myosin-1C stabilizes the mitotic spindle in Dictyostelium discoideum (Rump et al , 2011). In contrast, neither histone H2B nor 70-kDa dextran accumulated in this region; these results were similar to those seen with GFP alone (Figure 1B and Table S1).…”

Structure of the Single-lobe Myosin Light Chain C in Complex with the Light Chain-binding Domains of Myosin-1C Provides Insights into Divergent IQ Motif Recognition

“…It will be interesting to determine whether the LCBD plays a role in the localization of Dictyostelium myosin-1C. Dictyostelium myosin-1C is the only myosin-1 that has been shown to redistribute from the cell periphery to the spindle apparatus during mitosis (36). When localized to the actin-rich cell cortex, myosin-1C is involved in the generation of cortical tension and the extension and retraction of actin-rich cellular protrusions required for migration, endocytosis, micropinocytosis, and phagocytosis (11,14,15,37).…”

Tau Protein Diffuses along the Microtubule Lattice

“…Single-molecule TIRF Microscopy-A self-made objective type TIRF microscope with single-fluorophore sensitivity (30) was used for the detection of fluorescently labeled MTs and Tau molecules. Prior to immobilization on the surface of the flow chambers (30) the preformed MTs were incubated for 20 min at 35°C with Tau protein dilutions in buffer BRB12 (12 mM PIPES, 1 mM MgCl 2 , 1 mM EGTA, 10 mg/ml glucose, pH 6.8) with 10 M Paclitaxel.…”