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Actin filament-membrane attachment: are membrane particles involved?
The Journal of Cell Biology
|November 1, 1976
Summary
Membrane particles are not directly involved in attaching actin filaments to cell membranes. Research on sperm and intestinal cells shows actin filaments connect via bridges, not membrane particles.
Area of Science:
- Cell Biology
- Cytoskeleton Dynamics
- Membrane Biology
Background:
- Actin filament-membrane association is crucial for nonmuscle cell motility.
- Identifying specific attachment sites is key to understanding this interaction.
Purpose of the Study:
- To investigate the role of membrane particles in actin filament attachment to membranes.
- To examine specific attachment sites in sperm and intestinal epithelial cells.
Main Methods:
- Utilized freeze-fracture electron microscopy.
- Examined acrosomal filament bundles in Mytilus and Limulus sperm.
- Analyzed microvillar filament bundles in intestinal epithelial cell brush borders.
- Incubated isolated brush borders in high Mg++ concentrations.
Main Results:
- No membrane particles were observed on the P face at actin attachment sites in sperm.
- Few particles were found at microvillar attachment sites.
- Actin filaments in microvilli attach via bridges.
- High Mg++ induced paracrystallization of actin filaments and circumferential bands of membrane particles, but spacing indicated not all bridges attach to particles.
Conclusions:
- Membrane particles are not directly involved in the end-on attachment of actin filaments to membranes.
- Actin filament attachment relies on bridging mechanisms, not direct interaction with membrane particles.