title: α-Actinin and fimbrin cooperate with myosin II to organize actomyosin bundles during contractile-ring assembly.
abstract: The actomyosin contractile ring assembles through the condensation of a broad band of nodes that forms at the cell equator in fission yeast cytokinesis. The condensation process depends on actin filaments that interconnect nodes. By mutating or titrating actin cross-linkers α-actinin Ain1 and fimbrin Fim1 in live cells, we reveal that both proteins are involved in node condensation. Ain1 and Fim1 stabilize the actin cytoskeleton and modulate node movement, which prevents nodes and linear structures from aggregating into clumps and allows normal ring formation. Our computer simulations modeling actin filaments as semiflexible polymers reproduce the experimental observations and provide a model of how actin cross-linkers work with other proteins to regulate actin-filament orientations inside actin bundles and organize the actin network. As predicted by the simulations, doubling myosin II Myo2 level rescues the node condensation defects caused by Ain1 overexpression. Taken together, our work supports a cooperative process of ring self-organization driven by the interaction between actin filaments and myosin II, which is progressively stabilized by the cross-linking proteins.
authors: Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210, USA.
authors: Damien
authors: D
authors: Laporte
authors: Nikola
authors: N
authors: Ojkic
authors: Dimitrios
authors: D
authors: Vavylonis
authors: Jian-Qiu
authors: JQ
authors: Wu
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D000185:Actinin / Q000378:metabolism*; D000205:Actomyosin / Q000378:metabolism*; D002453:Cell Cycle; D003198:Computer Simulation; D048749:Cytokinesis; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008840:Microfilament Proteins / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D024462:Myosin Type II / Q000378:metabolism*; D011485:Protein Binding; D055503:Protein Multimerization; D055550:Protein Stability; D012568:Schizosaccharomyces / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D029702:Schizosaccharomyces pombe Proteins / Q000378:metabolism; D059008:Time-Lapse Imaging
chemical_list: D008562:Membrane Glycoproteins; D008840:Microfilament Proteins; D029702:Schizosaccharomyces pombe Proteins; C430383:ain1 protein, S pombe; C026742:plastin; D000185:Actinin; D000205:Actomyosin; D024462:Myosin Type II