Myo2p is the major motor involved in actomyosin ring contraction in fission yeast

Zambon, Paola; Palani, Saravanan; Kamnev, Anton; Balasubramanian, Mohan K.

doi:10.1016/j.cub.2016.12.024

Cited by 13 publications

(14 citation statements)

References 10 publications

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“…Myo2 is reported to be the main contributor to AMR tension (Zambon et al , 2017). Thus, contrary to the original hypothesis leading up to the experiments in Figure 4, our observations suggest that two factors contribute to peeling: First, the region of highest tension exerts a pulling force on its neighboring regions, which is transmitted around the AMR, so that the region directly opposite is subsequently pulled apart in both directions.…”

Section: Resultsmentioning

confidence: 99%

Actin turnover ensures uniform tension distribution during cytokinetic actomyosin ring contraction

Cheffings

Burroughs

Balasubramanian

2019

MBoC

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In many eukaryotes, cytokinesis is facilitated by the contraction of an actomyosin ring (AMR). The exact mechanisms that lead to this contractility are unknown, although some models posit that actin turnover in the AMR is essential. The effect of reduced actin dynamics during AMR formation has been well studied in Schizosaccharomyces pombe; however, the corresponding effects on AMR contraction are not well understood. By using mutants of the fission yeast actin severing protein Adf1, we observed that contracting AMRs display a “peeling” phenotype, where bundles of actin and myosin peel off from one side of the AMR, and are pulled across to the opposite side. This occurs multiple times during cytokinesis and is dependent on the activity of myosins Myo2, Myp2, and Myo51. We found that the distribution of Myo2 in the AMR anticorrelates with the location of peeling events, suggesting that peeling is caused by a nonuniform tension distribution around the AMR, and that one of the roles of actin turnover is to maintain a uniform tension distribution around the AMR.

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Section: Resultsmentioning

confidence: 99%

Actin turnover ensures uniform tension distribution during cytokinetic actomyosin ring contraction

Cheffings

Burroughs

Balasubramanian

2019

MBoC

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“…Super‐resolution fluorescence microscopy of nodes in live cells shows that Mid1p and Rng2p anchor the C‐terminal tails of about ten Myo2 molecules to the plasma membrane with the heads oriented towards the cytoplasm (Laplante et al, ). Myo2 contributes to both the assembly and constriction of the contractile ring (Laplante et al, ; Laplante & Pollard, ; Zambon et al, ). Phosphorylation of S1444 near the C‐terminus of Myo2 heavy chain (Motegi et al, ) is not required for contractile ring assembly, but promotes its constriction (Sladewski et al, ).…”

Section: Introductionmentioning

confidence: 99%

Fission yeast Myo2: Molecular organization and diffusion in the cytoplasm

et al. 2017

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Myosin-II is required for the assembly and constriction of cytokinetic contractile rings in fungi and animals. We used electron microscopy, fluorescence recovery after photobleaching (FRAP), and fluorescence correlation spectroscopy (FCS) to characterize the physical properties of Myo2 from fission yeast Schizosaccharomyces pombe. By electron microscopy, Myo2 has two heads and a coiled-coiled tail like myosin-II from other species. The first 65 nm of the tail is a stiff rod, followed by a flexible, less-ordered region up to 30 nm long. Myo2 sediments as a 7 S molecule in high salt, but aggregates rather than forming minifilaments at lower salt concentrations; this is unaffected by heavy chain phosphorylation. We used FRAP and FCS to observe the dynamics of Myo2 in live S. pombe cells and in cell extracts at different salt concentrations; both show that Myo2 with an N-terminal mEGFP tag has a diffusion coefficient of ∼ 3 µm s in the cytoplasm of live cells during interphase and mitosis. Photon counting histogram analysis of the FCS data confirmed that Myo2 diffuses as doubled-headed molecules in the cytoplasm. FCS measurements on diluted cell extracts showed that mEGFP-Myo2 has a diffusion coefficient of ∼ 30 µm s in 50 to 400 mM KCl concentrations.

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“…Of these, myosin II has gained considerable attention owing to its function as a motor that generates tension ( Bezanilla et al, 1997 ; De Lozanne and Spudich, 1987 ; Herman and Pollard, 1979 ; Kitayama et al, 1997 ; Mabuchi and Okuno, 1977 ; Motegi et al, 1997 , 2000 ; Naqvi et al, 2000 ). Consistently, mutants affected in myosin II heavy and light chains affect cytokinesis ( Balasubramanian et al, 1998 ; Bezanilla et al, 1997 ; Bi et al, 1998 ; Karess et al, 1991 ; Kitayama et al, 1997 ; Knecht and Loomis, 1987 ; Lippincott and Li, 1998 ; McCollum et al, 1995 ; Motegi et al, 1997 ; Naqvi et al, 2000 ; Palani et al, 2017 ; Zambon et al, 2017 ). Myosin II function in cytokinesis has parallels with its function in cardiac smooth muscle, and defects in myosin II can cause hypertrophic cardiomyopathy and dilated cardiomyopathy ( Huang and Szczesna-Cordary, 2015 ; Kim et al, 2005 ; Ma et al, 2012 ; Tang et al, 2016 ).…”

Section: Introductionmentioning

confidence: 88%

Steric hindrance in the upper 50 kDa domain of the motor Myo2p leads to cytokinesis defects in fission yeast

Palani

Srinivasan

Zambon

et al. 2018

Journal of Cell Science

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Cytokinesis in many eukaryotes requires a contractile actomyosin ring that is placed at the division site. In fission yeast, which is an attractive organism for the study of cytokinesis, actomyosin ring assembly and contraction requires the myosin II heavy chain Myo2p. Although myo2-E1, a temperature-sensitive mutant defective in the upper 50 kDa domain of Myo2p, has been studied extensively, the molecular basis of the cytokinesis defect is not understood. Here, we isolate myo2-E1-Sup2, an intragenic suppressor that contains the original mutation in myo2-E1 (G345R) and a second mutation in the upper 50 kDa domain (Y297C). Unlike myo2-E1-Sup1, a previously characterized myo2-E1 suppressor, myo2-E1-Sup2 reverses actomyosin ring contraction defects in vitro and in vivo. Structural analysis of available myosin motor domain conformations suggests that a steric clash in myo2-E1, which is caused by the replacement of a glycine with a bulky arginine, is relieved in myo2-E1-Sup2 by mutation of a tyrosine to a smaller cysteine. Our work provides insight into the function of the upper 50 kDa domain of Myo2p, informs a molecular basis for the cytokinesis defect in myo2-E1, and may be relevant to the understanding of certain cardiomyopathies.

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Myo2p is the major motor involved in actomyosin ring contraction in fission yeast

Cited by 13 publications

References 10 publications

Actin turnover ensures uniform tension distribution during cytokinetic actomyosin ring contraction

Actin turnover ensures uniform tension distribution during cytokinetic actomyosin ring contraction

Fission yeast Myo2: Molecular organization and diffusion in the cytoplasm

Steric hindrance in the upper 50 kDa domain of the motor Myo2p leads to cytokinesis defects in fission yeast

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