title: Mechanical stress and network structure drive protein dynamics during cytokinesis.
abstract: Cell-shape changes associated with processes like cytokinesis and motility proceed on several-second timescales but are derived from molecular events, including protein-protein interactions, filament assembly, and force generation by molecular motors, all of which occur much faster [1-4]. Therefore, defining the dynamics of such molecular machinery is critical for understanding cell-shape regulation. In addition to signaling pathways, mechanical stresses also direct cytoskeletal protein accumulation [5-7]. A myosin-II-based mechanosensory system controls cellular contractility and shape during cytokinesis and under applied stress [6, 8]. In Dictyostelium, this system tunes myosin II accumulation by feedback through the actin network, particularly through the crosslinker cortexillin I. Cortexillin-binding IQGAPs are major regulators of this system. Here, we defined the short timescale dynamics of key cytoskeletal proteins during cytokinesis and under mechanical stress, using fluorescence recovery after photobleaching and fluorescence correlation spectroscopy, to examine the dynamic interplay between these proteins. Equatorially enriched proteins including cortexillin I, IQGAP2, and myosin II recovered much more slowly than actin and polar crosslinkers. The mobility of equatorial proteins was greatly reduced at the furrow compared to the interphase cortex, suggesting their stabilization during cytokinesis. This mobility shift did not arise from a single biochemical event, but rather from a global inhibition of protein dynamics by mechanical-stress-associated changes in the cytoskeletal structure. Mechanical tuning of contractile protein dynamics provides robustness to the cytoskeletal framework responsible for regulating cell shape and contributes to cytokinesis fidelity.
authors.affiliation: Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, MD 21218, USA.
authors.forename: Vasudha
authors.initials: V
authors.lastname: Srivastava
authors.affiliation: Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, MD 21218, USA. Electronic address: dnr@jhmi.edu.
authors.forename: Douglas N
authors.initials: DN
authors.lastname: Robinson
mesh_terms: D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D019086:Bridged Bicyclo Compounds, Heterocyclic; D018797:Cell Cycle Proteins / Q000378:metabolism*; D048430:Cell Shape / Q000502:physiology*; D048749:Cytokinesis / Q000502:physiology*; D003599:Cytoskeleton / Q000502:physiology*; D047630:Depsipeptides; D004023:Dictyostelium; D036681:Fluorescence Recovery After Photobleaching; D008840:Microfilament Proteins / Q000378:metabolism; D024462:Myosin Type II / Q000378:metabolism; D015800:Protozoan Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D013050:Spectrometry, Fluorescence; D013314:Stress, Mechanical; D053778:Thiazolidines; D020703:ras GTPase-Activating Proteins / Q000378:metabolism
chemical_list: D019086:Bridged Bicyclo Compounds, Heterocyclic; D018797:Cell Cycle Proteins; D047630:Depsipeptides; C101002:IQGAP2 protein, human; D008840:Microfilament Proteins; D015800:Protozoan Proteins; D053778:Thiazolidines; C101109:ctxA protein, Dictyostelium discoideum; D020703:ras GTPase-Activating Proteins; C057531:jasplakinolide; D024462:Myosin Type II; C037067:latrunculin A