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Regulating contractility of the actomyosin cytoskeleton by pH.

ABSTRACT: The local interaction of F-actin with myosin-II motor filaments and crosslinking proteins is crucial for the force generation, dynamics, and reorganization of the intracellular cytoskeleton. By using a bottom-up approach, we are able to show that the contractility of reconstituted active actin systems is tightly controlled by the local pH. The pH-dependent intrinsic crossbridge strength of myosin-II is identified to account for a sharp transition of the actin/myosin-II activity from noncontractile to contractile by a change in pH of only 0.1. This pH-dependent contractility is a generic feature, which is observed in all studied crosslinked actin/myosin-II systems. The specific type and concentration of crosslinking protein allows one to sensitively adjust the range of pH where contraction occurs, which can recover the behavior found in Xenopus laevis oocyte extracts. Small variations in pH provide a mechanism of controlling the contractility of cytoskeletal structures, which can be expected to have broad implications in our understanding of cytoskeletal regulation.

SUBMITTER: Kohler S

PROVIDER: S-EPMC3767110 | biostudies-literature | 2012 Sep

REPOSITORIES: biostudies-literature

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Regulating contractility of the actomyosin cytoskeleton by pH.

Köhler Simone S Schmoller Kurt M KM Crevenna Alvaro H AH Bausch Andreas R AR

Cell reports 20120920 3

The local interaction of F-actin with myosin-II motor filaments and crosslinking proteins is crucial for the force generation, dynamics, and reorganization of the intracellular cytoskeleton. By using a bottom-up approach, we are able to show that the contractility of reconstituted active actin systems is tightly controlled by the local pH. The pH-dependent intrinsic crossbridge strength of myosin-II is identified to account for a sharp transition of the actin/myosin-II activity from noncontracti ...[more]

PMID: 22999933

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Project description:BackgroundNotch-Delta signaling functions across a wide array of animal systems to break symmetry in a sheet of undifferentiated cells and generate cells with different fates, a process known as lateral inhibition. Unlike many other signaling systems, however, since both the ligand and receptor are transmembrane proteins, the activation of Notch by Delta depends strictly on cell-cell contact. Furthermore, the binding of the ligand to the receptor may not be sufficient to induce signaling, since recent work in cell culture suggests that ligand-induced Notch signaling also requires a mechanical pulling force. This tension exposes a cleavage site in Notch that, when cut, activates signaling. Although it is not known if mechanical tension contributes to signaling in vivo, others have suggested that this is how endocytosis of the receptor-ligand complex contributes to the cleavage and activation of Notch. In a similar way, since Notch-mediated lateral inhibition at a distance in the dorsal thorax of the pupal fly is mediated via actin-rich protrusions, it is possible that cytoskeletal forces generated by networks of filamentous actin and non-muscle myosin during cycles of protrusion extension and retraction also contribute to Notch signaling.ResultsTo test this hypothesis, we carried out a detailed analysis of the role of myosin II-dependent tension in Notch signaling in the developing fly and in cell culture. Using dynamic fluorescence-based reporters of Notch, we found that myosin II is important for signaling in signal sending and receiving cells in both systems-as expected if myosin II-dependent tension across the Notch-Delta complex contributes to Notch activation. While myosin II was found to contribute most to signaling at a distance, it was also required for maximal signaling between adjacent cells that share lateral contacts and for signaling between cells in culture.ConclusionsTogether these results reveal a previously unappreciated role for non-muscle myosin II contractility in Notch signaling, providing further support for the idea that force contributes to the cleavage and activation of Notch in the context of ligand-dependent signaling, and a new paradigm for actomyosin-based mechanosensation.

Dataset Information

Regulating contractility of the actomyosin cytoskeleton by pH.

Publications

Regulating contractility of the actomyosin cytoskeleton by pH.

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