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Large and reversible myosin-dependent forces in rigidity sensing
James Lohner1,2, Jean-Francois Rupprecht1,3, Junquiang Hu2
1first authors.
Nature Physics
|April 1, 2021
Summary
Cellular rigidity sensing involves myosin motors contracting actin filaments. Experiments reveal these motors generate unexpectedly large forces, contract in a stepwise manner, and exhibit collective behavior, challenging prior models.
Area of Science:
- Cell Biology
- Biophysics
- Mechanobiology
Background:
- Cells perceive environmental rigidity via actin-myosin contractions.
- Myosin motors generate forces within actin filaments to anchor cells.
- Understanding these contractile units is crucial for cell mechanics.
Purpose of the Study:
- To investigate the force generation and behavior of cellular contractile units at high resolution.
- To challenge and refine current models of molecular motor force generation in a cellular context.
- To explain the observed stepwise contractions and their relation to matrix rigidity sensing.
Main Methods:
- High-resolution experimental observation of cellular contractile units.
- Analysis of myosin filament force generation and contraction dynamics.
- Development of a two-state model for collective molecular motor behavior.
Main Results:
- Bipolar myosin filaments generate significantly higher forces per motor than previously measured.
- Contraction and relaxation occur at consistent rates across various matrix rigidities.
- Step-wise displacements at matrix contacts are observed during both contraction and relaxation phases.
- Collective motor behavior explains stepwise contractions, differentiating cellular from in vitro observations.
Conclusions:
- Cellular contractile units exhibit collective behaviors not predicted by single-molecule studies.
- Myosin motor collections display emergent properties influencing cellular rigidity sensing.
- The findings rationalize the specific contraction mechanisms observed in cells versus in vitro settings.
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