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08:05
Visualizing Membrane Ruffle Formation using Scanning Electron Microscopy
Published on: May 27, 2021
Ruffles limit diffusion in the plasma membrane during macropinosome formation.
Timothy P Welliver1, S Laura Chang, Jennifer J Linderman
1Program in Immunology, University of Michigan Medical School, Ann Arbor, MI 48109-5620, USA.
Journal of Cell Science
|December 24, 2011
Summary
Circular ruffles in macrophages concentrate signaling molecules, enhancing cell communication. This actin-driven process is crucial for forming macropinosomes and amplifying cellular signals.
Area of Science:
- Cell Biology
- Molecular Biology
- Biophysics
Background:
- Macropinosome formation is vital for cellular processes like nutrient uptake and immune surveillance.
- Macrophage-colony-stimulating factor (M-CSF) triggers signaling pathways essential for macropinosome formation.
- Circular ruffles are actin-rich plasma membrane structures involved in cellular signaling.
Purpose of the Study:
- To investigate the role of circular ruffles in restricting the lateral diffusion of membrane proteins.
- To understand how circular ruffles contribute to signal amplification during macropinosome formation.
- To test the hypothesis that actin-mediated confinement within circular ruffles is essential for Rac1 activation.
Main Methods:
- Utilized murine macrophages stimulated with M-CSF.
- Disrupted actin polymerization using latrunculin B to assess its effect on ruffling and Rac1 activity.
- Monitored the diffusion of photoactivatable green fluorescent protein targeted to the membrane (PAGFP-MEM) in live cells.
Main Results:
- M-CSF stimulation induced the formation of circular ruffles, concentrating signaling molecules.
- Latrunculin B inhibited ruffling and localized Rac1 activation, indicating actin's role in signaling.
- Circular ruffles retained PAGFP-MEM within their domains, suggesting confinement of membrane proteins.
- Diffusion within macropinocytic cups was not inhibited, but ruffles acted as barriers.
Conclusions:
- Circular ruffles act as signaling microdomains by confining essential membrane proteins.
- Actin-mediated confinement within circular ruffles amplifies Rac1 signaling through positive feedback.
- This organized signaling within ruffles facilitates the contractile events required for macropinosome closure.
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