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Structural and biochemical aspects of cell motility in amebas of Dictyostelium discoideum
Abstract:
Amebas of Dictyostelium discoideum contain both microfilaments and microtubules. Microfilaments, found primarily in a cortical filament network, aggregate into bundles when glycerinated cells contract in response to Mg-ATP. These cortical filaments bind heavy meromyosin. Microtubules are sparse in amebas before aggregation. Colchicine, griseofulvin, or cold treatments do not affect cell motility or cell shape. Saltatory movement of cytoplasmic particles is inhibited by these treatments and the particles subsequently accumulate in the posterior of the cell. Cell motility rate changes as Dicytostelium amebas go through different stages of the life cycle. Quantitation of cellular actin by sodium dodecyl sulfate-polyacrylamide gel electrophoresis shows that the quantity of cellular actin changes during the life cycle. These changes in actin are directly correlated with changes in motility rate. Addition of cyclic AMP to Dictyostelium cultures at the end of the feeding stage prevents a decline in motility rate during the preaggregation stage. Cyclic AMP also modifies the change in actin content of the cells during preaggregation.
Insights
Dictyostelium discoideum ameba motility is linked to actin content, which changes during the cell cycle. Cyclic AMP influences actin levels and motility, impacting cell behavior.
Area of Science:
- Cell Biology
- Biochemistry
- Developmental Biology
Background:
- Dictyostelium discoideum amebas possess both microfilaments and microtubules.
- Microfilaments form a cortical network and aggregate upon Mg-ATP stimulation.
- Microtubules are less abundant and their disruption does not affect cell shape or motility.
Purpose of the Study:
- To investigate the relationship between cellular actin content and motility in Dictyostelium discoideum.
- To understand the role of cyclic AMP in regulating actin dynamics and motility during the cell cycle.
Main Methods:
- Glycerination and Mg-ATP treatment to observe microfilament aggregation.
- Treatment with colchicine, griseofulvin, or cold to assess microtubule involvement.
- Quantitation of cellular actin using sodium dodecyl sulfate-polyacrylamide gel electrophoresis.
- Monitoring changes in cell motility rate throughout the life cycle.
Main Results:
- Microfilaments bind heavy meromyosin.
- Disruption of microtubules inhibits saltatory movement and causes particle accumulation.
- Cell motility rate varies with life cycle stages.
- Cellular actin quantity changes correlate with motility rate.
- Cyclic AMP addition prevents motility decline and modifies actin content changes during preaggregation.
Conclusions:
- Actin dynamics are crucial for Dictyostelium discoideum ameba motility.
- Cyclic AMP plays a regulatory role in actin content and motility, particularly during the preaggregation stage.