A Myosin II-Based Nanomachine Devised for the Study of Ca2+-Dependent Mechanisms of Muscle Regulation

Pertici, Irene; Bianchi, Giulio; Bongini, Lorenzo; Lombardi, Vincenzo; Bianco, Pasquale

doi:10.3390/ijms21197372

Cited by 12 publications

(14 citation statements)

References 44 publications

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“…In accordance with experimental data [ 44 , 45 , 64 , 65 , 66 , 67 , 68 ], the simulated FV relationship for moderately small ensembles ( N , 33–39; Figure 7 ) exhibits the typical Hill shape [ 69 ]: an overall hyperbolic shape. However, the model predicts a less curved relationship for the low-ensemble case, consistent with one [ 44 ] but not other sets [ 66 , 70 ] of small-ensemble near-physiological (mM) [MgATP] experimental data.…”

Section: Resultssupporting

confidence: 81%

Insights into Muscle Contraction Derived from the Effects of Small-Molecular Actomyosin-Modulating Compounds

Månsson

Rassier²

2022

IJMS

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Bottom-up mechanokinetic models predict ensemble function of actin and myosin based on parameter values derived from studies using isolated proteins. To be generally useful, e.g., to analyze disease effects, such models must also be able to predict ensemble function when actomyosin interaction kinetics are modified differently from normal. Here, we test this capability for a model recently shown to predict several physiological phenomena along with the effects of the small molecular compound blebbistatin. We demonstrate that this model also qualitatively predicts effects of other well-characterized drugs as well as varied concentrations of MgATP. However, the effects of one compound, amrinone, are not well accounted for quantitatively. We therefore systematically varied key model parameters to address this issue, leading to the increased amplitude of the second sub-stroke of the power stroke from 1 nm to 2.2 nm, an unchanged first sub-stroke (5.3–5.5 nm), and an effective cross-bridge attachment rate that more than doubled. In addition to better accounting for the effects of amrinone, the modified model also accounts well for normal physiological ensemble function. Moreover, a Monte Carlo simulation-based version of the model was used to evaluate force–velocity data from small myosin ensembles. We discuss our findings in relation to key aspects of actin–myosin operation mechanisms causing a non-hyperbolic shape of the force–velocity relationship at high loads. We also discuss remaining limitations of the model, including uncertainty of whether the cross-bridge elasticity is linear or not, the capability to account for contractile properties of very small actomyosin ensembles (<20 myosin heads), and the mechanism for requirements of a higher cross-bridge attachment rate during shortening compared to during isometric contraction.

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Section: Resultssupporting

confidence: 81%

Insights into Muscle Contraction Derived from the Effects of Small-Molecular Actomyosin-Modulating Compounds

Månsson

Rassier²

2022

IJMS

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“…Biotinylated beads were then incubated with 0.1 M glycine, 0.5 mg/ml neutravidin and 0.02 mg/ml streptavidin-alexa532 or, alternatively, with 0.02 mg/ml streptavidin-alexa647 (Thermo Fisher Scientific) in the experiments with oriented dumbbells 30 . In the latter experiments, the correct orientation of the biotinylated actin filament was achieved by using the Bead Tailed Actin (BTA) method established by Pertici et al 31 . The method takes advantage of the property of Gelsolin TL40 to cap the barbed (+end) of the actin filament.…”

Section: Methodsmentioning

confidence: 99%

α-catenin switches between a slip and an asymmetric catch bond with F-actin to cooperatively regulate cell junction fluidity

et al. 2022

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Abstractα-catenin is a crucial protein at cell junctions that provides connection between the actin cytoskeleton and the cell membrane. At adherens junctions (AJs), α-catenin forms heterodimers with β-catenin that are believed to resist force on F-actin. Outside AJs, α-catenin forms homodimers that regulates F-actin organization and directly connect the cell membrane to the actin cytoskeleton, but their mechanosensitive properties are inherently unknown. By using ultra-fast laser tweezers we found that a single α-β-catenin heterodimer does not resist force but instead slips along F-actin in the direction of force. Conversely, the action of 5 to 10 α-β-catenin heterodimers together with force applied toward F-actin pointed end engaged a molecular switch in α-catenin, which unfolded and strongly bound F-actin as a cooperative catch bond. Similarly, an α-catenin homodimer formed an asymmetric catch bond with F-actin triggered by protein unfolding under force. Our data suggest that α-catenin clustering together with intracellular tension engage a fluid-to-solid phase transition at the membrane-cytoskeleton interface.

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“…In the latter experiments, the correct orientation of the biotinylated actin filament was achieved by using the Bead Tailed Actin (BTA) method established by Pertici et al 29 . The method takes advantage of the property of Gelsolin TL40 to cap the barbed (+end) of the actin filament.…”

Section: Optical Trapping Experimentsmentioning

confidence: 99%

α-catenin switches between a slip and an asymmetric catch bond with F-actin to cooperatively regulate cell junction fluidity

Arbore

Σεργίδης

Gardini

et al. 2020

Preprint

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Cell adhesions dynamically tune their mechanical properties during tissue development and homeostasis. Fluid connections required for cell mobility can switch to solid links to maintain the mechanical rigidity of epithelial layers 1,2 . Changes in the composition and clustering of adhesion molecules have been proposed to modulate cell junction fluidity, but the underlying mechanisms are unclear 3,4 . acatenin has been shown to play a fundamental role in different adhesion sites. At adherens cell-cell junctions (AJ), a-catenin localizes in cadherin-catenin complexes, where it provides a mechanical link between b-catenin and the actin cytoskeleton 5 . However, its function is controversial owing to the low affinity between actin and the a-b-catenin heterodimer 6 . Outside AJ, a-catenin binds itself to form homodimers that connect the cell membrane to the actin cytoskeleton to promote adhesion and migration, but its mechanosensitive properties are inherently unknown 7,8 . Here, using ultra-fast laser tweezers 9 we show that a single mammalian a-catenin molecule displays very different force-bearing properties depending on whether it is associated to b-catenin or not. We found that a single a-b-catenin heterodimer slips along an actin filament in the direction of force, while a single a-catenin homodimer forms a strong asymmetric catch-bond with actin, in which the bond lifetime increases, and the protein unfolds with force. Importantly, assemblies of multiple ab-catenin heterodimers show force-bearing and unfolding properties similar to the acatenin homodimer. Our results indicate that, outside AJ, single a-catenin homodimers act as a mechanical link with the actin cytoskeleton that resists force efficiently. Nonetheless, inside AJ, a-catenin's capability to hold cell-cell connections under physiological loads critically depends on the recruitment of multiple (5-10) complexes. Our data support a molecular model in which a-catenin clustering and intercellular tension engage a fluid-to-solid phase transition at the membranecytoskeleton interface.In any living cell, an array of mechanotransductor proteins responds to mechanical cues to trigger complex molecular signaling, driving cell morphology and gene expression profiles 10 . Among these proteins, a-catenin has been reported to act as a mechanosensor that regulates adherens junctions (AJ) in response to mechanical cues from neighboring cells in a tissue 5 . It is widely accepted that a-catenin in AJ binds b-catenin, which, in turn, connects to the cytoplasmatic portion of E-cadherin to constitute the cadherin-catenin complex (CCC). Since a-catenin also binds actin, a-catenin has been indicated as a major candidate for providing a link between the CCC and the actin cytoskeleton. This molecular link is required

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A Myosin II-Based Nanomachine Devised for the Study of Ca2+-Dependent Mechanisms of Muscle Regulation

Cited by 12 publications

References 44 publications

Insights into Muscle Contraction Derived from the Effects of Small-Molecular Actomyosin-Modulating Compounds

Insights into Muscle Contraction Derived from the Effects of Small-Molecular Actomyosin-Modulating Compounds

α-catenin switches between a slip and an asymmetric catch bond with F-actin to cooperatively regulate cell junction fluidity

α-catenin switches between a slip and an asymmetric catch bond with F-actin to cooperatively regulate cell junction fluidity

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