Principles of unconventional myosin function and targeting.
ABSTRACT Unconventional myosins are a superfamily of actin-based motors implicated in diverse cellular processes. In recent years, much progress has been made in describing their biophysical properties, and headway has been made into analyzing their cellular functions. Here, we focus on the principles that guide in vivo motor function and targeting to specific cellular locations. Rather than describe each motor comprehensively, we outline the major themes that emerge from research across the superfamily and use specific examples to illustrate each. In presenting the data in this format, we seek to identify open questions in each field as well as to point out commonalities between them. To advance our understanding of myosins' roles in vivo, clearly we must identify their cellular cargoes and the protein complexes that regulate motor attachment to fully appreciate their functions on the cellular and developmental levels.
SourceAvailable from: Zhitian Zheng[Show abstract] [Hide abstract]
ABSTRACT: To determine the mechanism of resistance to the fungicide phenamacril (JS399-19) in Fusarium graminearum, the causal agent of Fusarium head blight, we sequenced and annotated the genome of the resistant strain YP-1 (generated by treating the F. graminearum reference strain PH-1 with phenamacril). Of 1.4 million total reads from an Illumina-based paired-end sequencing assay, 92.80% were aligned to the F. graminearum reference genome. Compared with strain PH-1, strain YP-1 contained 1,989 single-nucleotide polymorphisms that led to amino acid mutations in 132 genes. We sequenced 22 functional annotated genes of another F. graminearum sensitive strain (strain 2021) and corresponding resistant strains. The only mutation common to all of the resistant mutants occurred in the gene encoding myosin-5 (point mutations at codon 216, 217, 418, 420, or 786). To confirm whether the mutations in myosin-5 confer resistance to phenamacril, we exchanged the myosin-5 locus between the sensitive strain 2021 and the resistant strain Y2021A by homologous double exchange. The transformed mutants with a copy of the resistant fragment exhibited resistance to phenamacril, and the transformed mutant with a copy of the sensitive fragment exhibited sensitivity to phenamacril. These results indicate that mutations in myosin-5 confers resistance to phenamacril in F. graminearum.Scientific Reports 02/2015; 5:8248. DOI:10.1038/srep08248 · 5.08 Impact Factor
[Show abstract] [Hide abstract]
ABSTRACT: During animal cell division, an actin-based ring cleaves the cell into two. Problems with this process can cause chromosome missegregation and defects in cytoplasmic inheritance and the partitioning of organelles, which in turn are associated with human diseases [1-3]. Although much is known about how chromosome segregation is coupled to cell division, the way organelles coordinate their inheritance during partitioning to daughter cells is less well understood. Here, using a high-content live-imaging small interfering RNA screen, we identify Myosin-XIX (Myo19) as a novel regulator of cell division. Previously, this actin-based motor was shown to control the interphase movement of mitochondria . Our analysis shows that Myo19 is indeed localized to mitochondria and that its silencing leads to defects in the distribution of mitochondria within cells and in mitochondrial partitioning at division. Furthermore, many Myo19 RNAi cells undergo stochastic division failure-a phenotype that can be mimicked using a treatment that blocks mitochondrial fission and rescued by decreasing mitochondrial fusion, implying that mitochondria can physically interfere with cytokinesis. Strikingly, using live imaging we also observe the inappropriate movement of mitochondria to the poles of spindles in cells depleted for Myo19 as they enter anaphase. Since this phenocopies the results of an acute loss of actin filaments in anaphase, these data support a model whereby the Myo19 actin-based motor helps to control mitochondrial movement to ensure their faithful segregation during division. The presence of DNA within mitochondria makes their inheritance an especially important aspect of symmetrical cell division. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.Current Biology 10/2014; 24(21):2598-2605. DOI:10.1016/j.cub.2014.09.045 · 9.92 Impact Factor
[Show abstract] [Hide abstract]
ABSTRACT: We determined the crystal structure of the motor domain of human non-muscle myosin 2B (NM-2B) in a nucleotide-free state and at a resolution of 2.8Å. The structure shows the motor domain with an open active site and the large cleft that divides the 50kDa domain in a closed state. Compared to other rigor-like myosin motor domain structures, our structure shows subtle but significant conformational changes in regions important for actin binding and mechanochemical coupling. Moreover, our crystal structure helps to rationalize the impact of myosin, heavy chain 9 (MYH9)-related disease mutations Arg709Cys and Arg709His on the kinetic and functional properties of NM-2B and of the closely related non-muscle myosin 2A (NM-2A). Copyright © 2014 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.FEBS Letters 11/2014; DOI:10.1016/j.febslet.2014.11.007 · 3.34 Impact Factor