Actin stress fibers are at a tipping point between conventional shortening and rapid disassembly at physiological levels of MgATP

Matsui, Tsubasa S.; Ito, Kazushi; Kaunas, Roland; Sato, Masaaki; Deguchi, Shinji

doi:10.1016/j.bbrc.2010.03.150

Cited by 21 publications

(26 citation statements)

References 35 publications

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“…In addition, there is no obvious mechanism by which quick cell shortening is able to cause selective disassembly of only the SFs oriented in the direction of shortening [19][20][21] if this disassembly is caused only by diffusively transported biochemical signals [18]. Our results provide additional lines of evidence for the putative mechanism underlying selective disassembly of SFs (figure 10), which we previously discussed [23] and here delve more deeply into the underlying mechanism. In addition to MLC-regulating intracellular signals, SF remodelling is controlled by mechanical cues from their environment.…”

Section: Discussionsupporting

confidence: 68%

“…Using this SF preparation with actin filaments labelled with Alexa-phalloidin, we performed time-lapse fluorescence microscopy to confirm that the SFs maintained MgATP-induced contractile function in the presence of phalloidin. Our previous time-lapse imaging by phasecontrast microscopy showed that unlabelled extracted SFs promptly disassembled at [MgATP] above 4 mM, whereas the SFs shortened in axial length at [MgATP] below this critical value [23]. In the present study, we used an [MgATP] of 2.7 mM (m ¼ 157 mM, pMg ¼ 2), which caused phalloidin-bound SFs to shorten at a constant rate of approximately 0.8 mm s 21 before collapsing into a tight mass without inducing disassembly (figure 4).…”

Section: Contraction Of Extracted Stress Fibresmentioning

confidence: 99%

“…The transition of SF condition from shortening (figure 4) to disassembly (figure 6) was induced only by increasing [MgATP] with a fixed m-value of the solutions. Thus, actin-myosin crossbridges with a limited number of NMIIs in a sarcomeric unit may be close to the limit for complete dissociation around the physiological [MgATP] [23].…”

Section: Myosin-driven Stress Fibre Disassembly T S Matsui Et Al 761mentioning

confidence: 99%

“…This rate is smaller than but comparable to the rates we previously measured for unlabelled extracted SFs (approx. 1.8 mm s 21 at 3 mM [MgATP]; [23]). …”

Section: Contraction Of Extracted Stress Fibresmentioning

confidence: 99%

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Non-muscle myosin II induces disassembly of actin stress fibres independently of myosin light chain dephosphorylation

et al. 2011

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Dynamic remodelling of actin stress fibres (SFs) allows non-muscle cells to adapt to applied forces such as uniaxial cell shortening. However, the mechanism underlying rapid and selective disassembly of SFs oriented in the direction of shortening remains to be elucidated. Here, we investigated how myosin crossbridge cycling induced by MgATP is associated with SF disassembly. Moderate concentrations of MgATP, or [MgATP], induced SF contraction. Meanwhile, at [MgATP] slightly higher than the physiological level, periodic actin patterns emerged along the length of SFs and dispersed within seconds. The actin fragments were diverse in length, but comparable to those in characteristic sarcomeric units of SFs. These results suggest that MgATP-bound non-muscle myosin II dissociates from the individual actin filaments that constitute the sarcomeric units, resulting in unbundling-induced disassembly rather than end-to-end actin depolymerization. This rapid SF disassembly occurred independent of dephosphorylation of myosin light chain. In terms of effects on actin-myosin interactions, a rise in [MgATP] is functionally equivalent to a temporal decrease in the total number of actin-myosin crossbridges. Actin-myosin crossbridges are known to be reduced by an assisting load on myosin. Thus, the present study suggests that reducing the number of actin-myosin crossbridges promotes rapid and orientation-dependent disassembly of SFs after cell shortening.

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Section: Discussionsupporting

confidence: 68%

Section: Contraction Of Extracted Stress Fibresmentioning

confidence: 99%

Section: Myosin-driven Stress Fibre Disassembly T S Matsui Et Al 761mentioning

confidence: 99%

“…This rate is smaller than but comparable to the rates we previously measured for unlabelled extracted SFs (approx. 1.8 mm s 21 at 3 mM [MgATP]; [23]). …”

Section: Contraction Of Extracted Stress Fibresmentioning

confidence: 99%

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Non-muscle myosin II induces disassembly of actin stress fibres independently of myosin light chain dephosphorylation

et al. 2011

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“…Then, Lee et al 43 further demonstrated in more details that the stretch-induced SFs reorganization is a complex process involving multiple phenomena including SF disassembly, reassembly, and fusion that depend on the rate of the stretching, Rhokinase and MLCK. Later, to understand the mechanisms of the rapid disassembly of SFs, Matsui et al 47 experimentally investigated the effects of MgATP concentration on SFs' shortening and stability.…”

Section: Introductionmentioning

confidence: 99%

Frequency-Dependent Focal Adhesion Instability and Cell Reorientation Under Cyclic Substrate Stretching

et al. 2011

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Associate Editors Mian Long and Fan Yuan oversaw the review of this article.Abstract-The adhesion-based cell mechanosensitivity plays central roles in many physiological and pathological processes. Recently, quantitative understanding of cell responses to external force has been intensively pursued. However, the frequency dependent cell responses to the substrate stretching have not yet been fully understood. Here we developed a multiscale modeling framework for studying cell reorientation behaviors under substrate stretching, in which the mechano-chemical coupling at molecular, subcellular, and cellular scales was considered. The effect of matrix stiffness was also considered in a FEM based mechano-chemical coupling simulation. We showed that the collapsing time of focal adhesion decreases with the increasing of the loading frequency, however, the cell reorientation time exhibits a biphasic frequency-dependent behavior. Our results suggested that this biphasic behavior might be caused by the competition between the frequency-dependent collapsing of focal adhesions and the less frequency-dependent formation of stress fibers aligning away from the loading direction. At the low loading frequency, the collapsing of focal adhesion dominates the reorientation process, however, at the high loading frequency the polymerization of stress fiber dominates the reorientation. Moreover, we showed that the compliance of matrix may help accelerate the cell reorientation because focal adhesion is prone to be instable on soft matrix.

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The position and size of individual focal adhesions are determined by intracellular stress‐dependent positive regulation

Deguchi¹,

Matsui²,

Iio³

2011

Cytoskeleton

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It remains unclear how the subcellular positions and sizes of individual focal adhesions (FAs) are determined in stationary cells. The elucidation of spatial regulation mechanisms is important for accurate understanding of the cellular response to mechanical stress. Through a theoretical analysis on previously reported cell behavior, the present study demonstrates a close correlation between the appearances of mechanosensitive elements and intracellular stress reflecting traction stress that the cell exerts on the substrate. The magnitude and distribution of stress were predicted in this analysis by mimicking intrinsic actomyosin contraction independent of extracellular stimuli. Positions of FAs and actin stress fibers corresponded to the local maximum and minimum stress points, respectively, and thus were determined by the global configuration of cell adhesions. Furthermore, their subcellular sizes were in agreement with the predicted stress magnitudes that were dependent on the local mechanical environment. These results suggest that a positive regulation (i.e., force and cell adhesion enhance each other) functions in the organization of individual FAs in nonmigrating cells.

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Actin stress fibers are at a tipping point between conventional shortening and rapid disassembly at physiological levels of MgATP

Cited by 21 publications

References 35 publications

Non-muscle myosin II induces disassembly of actin stress fibres independently of myosin light chain dephosphorylation

Non-muscle myosin II induces disassembly of actin stress fibres independently of myosin light chain dephosphorylation

Frequency-Dependent Focal Adhesion Instability and Cell Reorientation Under Cyclic Substrate Stretching

The position and size of individual focal adhesions are determined by intracellular stress‐dependent positive regulation

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