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Putative graviperception mechanisms of protists.
I Block1, N Freiberger, O Gavrilova
1Institute of Aerospace Medicine, DLR, Cologne, Germany.
Advances in Space Research : the Official Journal of the Committee on Space Research (COSPAR)
|September 7, 2001
Summary
Cells sense gravity using internal structures, with specialized organelles in some and common cell parts in others. Gravity sensing mechanisms in cells are fundamental, even under altered gravity conditions.
Area of Science:
- Cell Biology
- Biophysics
- Gravitational Biology
Background:
- Free-living cells exhibit gravitaxis, orienting spatially using the gravity vector.
- Both ameboid and ciliated cells share fundamental graviperception mechanisms despite different locomotion.
- Gravireception involves common cell structures or specialized organelles (e.g., Loxodidae).
Purpose of the Study:
- Investigate fundamental graviperception mechanisms in cells.
- Explore the role of cytoplasm and organelles (statoliths) in gravity sensing.
- Examine the impact of altered gravity and temperature on cellular gravitaxis.
Main Methods:
- Experiments with varying acceleration (0-5 g) and density-adjusted media.
- Analysis of cellular responses to mechanical stimuli and temperature changes.
- Spaceflight experiment (S/MM-06) assessing response to weightlessness.
Main Results:
- Cytoplasm or dense organelles (nuclei) likely act as statoliths, activating mechanosensitive ion channels.
- Prolonged weightlessness (9 days) did not impair Loxodes' response to acceleration.
- Prolonged cooling (14+ days, 4-10°C) abolished gravitactic orientation in Paramecium.
Conclusions:
- Cellular gravity sensing relies on mechanosensitive ion channels and statoliths (cytoplasm/organelles).
- Gravitaxis mechanisms are robust to short-term weightlessness but sensitive to prolonged cooling.
- Cyclic adenosine monophosphate (cAMP) may be involved in gravity signal transduction.