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Minipodia and rosette contacts are adhesive organelles present in free-living amoebae
A Grebecki1, L Grebecka, A Wasik
1Department of Cell Biology, Nencki Institute of Experimental Biology, Warszawa, Poland. grebecki@nencki.gov.pl
Abstract:
Using scanning electron microscopy, Amoeba proteus cells migrating on the glass have been shown to develop dense coats of minipodia, which are discrete microprotrusions up to 8 microm long and approximately 0.5 microm across. They cover the middle-anterior area of the ventral cell surface, i.e. the region previously determined as the zone of most efficient adhesion of an amoeba to its substratum. Minipodia are sparse underneath the frontal zone and lacking from the tail region. In amoebae that adhere to the glass without moving, have just started moving, or show unstable motor polarity, minipodia are grouped in rosette contacts, cauliflower-like papillae composed of supporting platforms with crowns of minipodia emerging from them. Both structures abound with cytoskeletal F-actin, as shown by staining with fluorescein-conjugated phalloidin. Amoebae experimentally prevented from adhering to the substratum neither develop discrete minipodia nor rosette contacts.
Insights
Amoeba proteus cells form minipodia, actin-rich microprotrusions crucial for cell adhesion and migration. These structures are essential for amoeboid movement and substrate interaction.
Area of Science:
- Cell Biology
- Microbiology
- Biophysics
Background:
- Amoeba proteus exhibits complex cell migration behaviors.
- Cell adhesion is critical for amoeboid movement on surfaces.
- The role of specific cell surface structures in amoeba adhesion was unclear.
Purpose of the Study:
- To investigate the role of minipodia in the adhesion and migration of Amoeba proteus.
- To characterize the structure and distribution of minipodia during cell movement.
- To determine the relationship between minipodia, cell adhesion, and cytoskeletal organization.
Main Methods:
- Scanning electron microscopy (SEM) for visualizing cell surface structures.
- Fluorescent staining with fluorescein-conjugated phalloidin to detect F-actin.
- Experimental manipulation to prevent cell-substratum adhesion.
Main Results:
- Migrating Amoeba proteus cells develop dense coats of minipodia (microprotrusions) on their ventral surface, primarily in the adhesion zone.
- Minipodia are rich in cytoskeletal F-actin.
- Non-migrating or unstably moving amoebae form rosette contacts and papillae composed of minipodia.
- Inhibition of adhesion prevents the formation of minipodia and associated structures.
Conclusions:
- Minipodia are key structures involved in the adhesion of Amoeba proteus to surfaces.
- The formation and organization of minipodia are directly linked to cell motility and substrate interaction.
- Actin cytoskeleton plays a crucial role in the formation of minipodia and adhesion structures.