In vivo dynamics of myosin II inDictyostelium by fluorescent analogue cytochemistry

Chu, Qian; Fukui, Yoshio

doi:10.1002/(sici)1097-0169(1996)35:3<254::aid-cm7>3.0.co;2-8

Cited by 10 publications

(3 citation statements)

References 57 publications

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“…6), presumably where the contractile force is generated during retraction. These results agree with studies on the in vivo dynamics of myosin II, which also revealed discrete actinrich and myosin II-rich structures at the posterior ends of Dictyostelium cells (Yumura et al, 1984;Chu and Fukui, 1996;Moores et al, 1996).…”

Section: Reformation Of a New Cortex Precedes Retractionsupporting

confidence: 90%

A Micromechanic Study of Cell Polarity and Plasma Membrane Cell Body Coupling in Dictyostelium

Merkel

Simson

et al. 2000

Biophysical Journal

109

108

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We used micropipettes to aspirate leading and trailing edges of wild-type and mutant cells of Dictyostelium discoideum. Mutants were lacking either myosin II or talin, or both proteins simultaneously. Talin is a plasma membrane-associated protein important for the coupling between membrane and actin cortex, whereas myosin II is a cytoplasmic motor protein essential for the locomotion of Dictyostelium cells. Aspiration into the pipette occurred above a threshold pressure only. For all cells containing talin this threshold was significantly lower at the leading edge of an advancing cell as compared to its rear end, whereas we found no such difference in cells lacking talin. Wild-type and talin-deficient cells were able to retract from the pipette against an applied suction pressure. In these cells, retraction was preceded by an accumulation of myosin II in the tip of the aspirated cell lobe. Mutants lacking myosin II could not retract, even if the suction pressures were removed after aspiration. We interpreted the initial instability and the subsequent plastic deformation of the cell surface during aspiration in terms of a fracture between the cell plasma membrane and the cell body, which may involve destruction of part of the cortex. Models are presented that characterize the coupling strength between membrane and cell body by a surface energy sigma. We find sigma approximately 0.6(1.6) mJ/m(2) at the leading (trailing) edge of wild-type cells.

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Section: Reformation Of a New Cortex Precedes Retractionsupporting

confidence: 90%

A Micromechanic Study of Cell Polarity and Plasma Membrane Cell Body Coupling in Dictyostelium

Merkel

Simson

et al. 2000

Biophysical Journal

109

108

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“…Latrunculin (0.1-1 M) depolymerizes actin filaments and inhibits cell movement (38-40); 1-100 M cytochalasin A similarly inhibits motility (40)(41)(42), and 0.5-10 M cytochalasin D also disrupts actin and inhibits motility (43,44). Transferring filters with developing cells at 4 h after starvation (when streams had begun to form) onto pads soaked with 0.1 M or higher latrunculin, 100 M cytochalasin A, or 0.3 M or higher cytochalasin D caused an increase in group size 4 h later, when streams had broken up (Fig.…”

Section: Resultsmentioning

confidence: 99%

A cell number-counting factor regulates the cytoskeleton and cell motility in Dictyostelium

Tang

Gao

McCollum

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

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Little is known about how a morphogenetic rearrangement of a tissue is affected by individual cells. Starving Dictyostelium discoideum cells aggregate to form dendritic streams, which then break up into groups of Ϸ2 ؋ 10 4 cells. Cell number is sensed at this developmental stage by using counting factor (CF), a secreted complex of polypeptides. A high extracellular concentration of CF indicates that there is a large number of cells, which then causes the aggregation stream to break up. Computer simulations indicated that stream breakup could be caused by CF decreasing cell-cell adhesion and͞or increasing cell motility, and we observed that CF does indeed decrease cell-cell adhesion. We find here that CF increases cell motility. In Dictyostelium, motility is mediated by actin and myosin. CF increases the amounts of polymerized actin and the ABP-120 actin-crosslinking protein. Partially inhibiting motility by using drugs that interfere with actin polymerization reduces stream dissipation, resulting in fewer stream breaks and thus larger groups. CF also potentiates the phosphorylation and redistribution of myosin while repressing its basal level of assembly. The computer simulations indicated that a narrower distribution of group sizes results when a secreted factor modulates both adhesion and motility. CF thus seems to induce the morphogenesis of streams into evenly sized groups by increasing actin polymerization, ABP-120 levels, and myosin phosphorylation and decreasing adhesion and myosin polymerization.

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“…Furthermore, a chimeric gene that consists of mhcA fused to the green fluorescent protein (GFP) gene was expressed in mhcA Ϫ Dictyostelium cells and was found to be functional in vivo (Moores et al, 1996). This new technique, as well as the more classic method of introducing fluorescently labeled myosin into live cells (Chu and Fukui, 1996;Yumura, 1996), enabled real time tracing of myosin localization in vivo. Thus, a wide spectrum of tools is now available to test a particular hypothesis concerning myosin's role or its regulation during cytokinesis in Dictyostelium.…”

Section: Introductionmentioning

confidence: 99%

Transport of Myosin II to the Equatorial Region without Its Own Motor Activity in MitoticDictyosteliumCells

Yumura

Uyeda

1997

MBoC

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Fluorescently labeled myosin moved and accumulated circumferentially in the equatorial region of dividing Dictyostelium cells within a time course of 4 min, followed by contraction of the contractile ring. To investigate the mechanism of this transport process, we have expressed three mutant myosins that cannot hydrolyze ATP in myosin null cells. Immunofluorescence staining showed that these mutant myosins were also correctly transported to the equatorial region, although no contraction followed. The rates of transport, measured using green fluorescent protein-fused myosins, were indistinguishable between wild-type and mutant myosins. These observations demonstrate that myosin is passively transported toward the equatorial region and incorporated into the forming contractile ring without its own motor activity. INTRODUCTIONCytokinesis of animal and lower eukaryotic amoeba cells is driven by constriction of the contractile ring. The contractile ring contains circumferential filaments of conventional myosin, or simply myosin hereafter, and actin filaments (reviewed by Mabuchi, 1986). There is cytological (Mabuchi and Okuno, 1977) and molecular genetic (De Lozanne and Spudich, 1987;Knecht and Loomis, 1987) evidence that myosin provides force for constriction of the contractile ring.The contractile ring is a highly transient structure and its assembly and disassembly are precisely regulated both spatially and temporally. Classic cytological studies using dividing eggs have established that the mitotic spindle ultimately determines the position of the contractile ring (reviewed by Mabuchi, 1986;Rappaport, 1991;Strome, 1993). Despite extensive research, the nature of the signal from the spindle to the cortex is still elusive. The molecular mechanism of accumulating myosin and other components of the contractile ring to the equatorial region is also still unknown.Recently, the cellular slime mold Dictyostelium discoideum has emerged as an excellent model experimental system to study cytokinesis with molecular and cell biological approaches. For instance, Dictyostelium provided the opportunity to prove genetically the critical roles myosin plays in cytokinesis, by inactivating the single-copy myosin heavy chain gene (mhcA) either by homologous recombination (De Lozanne and Spudich, 1987) or by antisense silencing (Knecht and Loomis, 1987). These studies also showed that the cells unable to carry out cytokinesis become large and multinucleated and eventually lyse in suspension culture but on a solid substratum can tear themselves into smaller pieces by amoeboid movement and grow. The latter behavior, named "traction-mediated cytofission," makes it possible to express mutated forms of myosin in mhcA Ϫ cells. Furthermore, a chimeric gene that consists of mhcA fused to the green fluorescent protein (GFP) gene was expressed in mhcA Ϫ Dictyostelium cells and was found to be functional in vivo (Moores et al., 1996). This new technique, as well as the more classic method of introducing fluorescently labeled myosin into live cel...

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In vivo dynamics of myosin II inDictyostelium by fluorescent analogue cytochemistry

Cited by 10 publications

References 57 publications

A Micromechanic Study of Cell Polarity and Plasma Membrane Cell Body Coupling in Dictyostelium

A Micromechanic Study of Cell Polarity and Plasma Membrane Cell Body Coupling in Dictyostelium

A cell number-counting factor regulates the cytoskeleton and cell motility in Dictyostelium

Transport of Myosin II to the Equatorial Region without Its Own Motor Activity in MitoticDictyosteliumCells

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