Related Experiment Videos
Smooth muscle actin determines mechanical force-induced p38 activation
Jiaxu Wang1, Jennie Fan, Carol Laschinger
1Canadian Institutes of Health, Group in Matrix Dynamics, Faculty of Dentistry, University of Toronto, Ontario, Canada.
The Journal of Biological Chemistry
|December 14, 2004
Summary
Mechanical force activates p38, a key signaling protein, through alpha-smooth muscle actin (SMA) filaments. This study reveals a novel SMA-dependent pathway that amplifies both SMA expression and p38 activation under force.
Area of Science:
- Cell Biology
- Mechanobiology
- Signal Transduction
Background:
- Mitogen-activated protein kinase p38 (MAPK p38) activation by mechanical force is known, but the specific cellular components involved remain unclear.
- Alpha-smooth muscle actin (SMA) is implicated in force generation within fibroblasts, suggesting a potential role in mechanotransduction.
Purpose of the Study:
- To investigate the role of alpha-smooth muscle actin (SMA) in the force-induced activation of p38.
- To elucidate the molecular mechanisms linking mechanical force, SMA, and p38 signaling.
Main Methods:
- Application of tensile forces to Rat-2 cells using magnetic beads.
- Immunoblotting to detect p38 isoforms and protein enrichment.
- RNA interference for SMA knockdown.
- Pharmacological inhibition of Rho kinase and p38.
- Analysis of SMA promoter activity.
Main Results:
- Force-induced p38 activation was dependent on SMA filaments, with SMA enrichment of collagen receptor complexes requiring alpha2beta1 integrin.
- Swinholide treatment depolymerized SMA filaments, blocking force-induced p38 phosphorylation and SMA increases.
- SMA knockdown (70%) inhibited force-induced p38 phosphorylation by 50%.
- Rho kinase inhibition blocked SMA filament assembly and force-induced p38 activation.
- Force application increased SMA content and enhanced p38 association with SMA filaments.
- p38 inhibition abrogated force-induced SMA increases, and SMA promoter activity was increased by active p38 signaling.
Conclusions:
- Force-induced p38 phosphorylation relies on an SMA filament-dependent pathway.
- A feed-forward loop synergizes force-induced SMA expression with p38 activation.
- SMA is a critical mediator in the cellular response to mechanical force, linking physical stimuli to intracellular signaling.