The fastest hands in the world. Scientists have deciphered the most lightning-fast cell movements
Researchers have discovered genes and proteins responsible for rapidly withdrawing heliozoan “arms” in response to changes in the environment. This is one of the fastest known examples of cell motility.
Raphidocystis Contractilis is a type of animal from the Heliozoa group that lives in fresh, brackish and sea water. These organisms are known as “sunworms” because of their diverging finger-like arms or axopodia, which give them the appearance of the sun.
The axopodia of sunworms are made up of a specific protein, tubulin, which forms microtubules. Despite its ability to rapidly retract its arms in response to stimuli, the mechanism behind such rapid shortening of the arms remained a mystery, writes SciTechDaily .
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To this end, a research team including Prof. Motonori Ando, Dr. Risu Ikeda from the Laboratory of Cellular Physiology and Associate Professor Mayuko Hamada from the Ushimado Marine Institute studied the mechanism involved in one of the fastest cell movements in the living world.
So how did it all start? Sharing the motives of his research, Professor Ando says: “Recently, a large number of heliozoic organisms were discovered in various hydrospheres of Okayama Prefecture, from which it became clear that several species of sunworms live in the same environment. We are trying to unravel their secrets and are gradually expanding our horizons. our knowledge.”
The authors began their study by labeling the tubulin protein and observing its movement before and after contraction. They found that prior to shortening, tubulins were systematically located along the entire length of the axopodia, but after shortening of these specific “arms” they rapidly accumulated on the cell surface. This led scientists to believe that when axopodia are quickly withdrawn, microtubules instantly disintegrate into tubulin. However, the degradation of microtubules is usually not a rapid phenomenon, it progresses rather slowly.
How could the sunworm achieve this change so quickly? The researchers hypothesized that this might be possible if the microtubules are simultaneously cleaved in several places. To confirm their hypothesis, the authors set out to find proteins and genes involved in the instantaneous cleavage of microtubules in sunworms.
The researchers performed an analysis of the genes that work at certain times in the cell and identified about 32,000 genes in sunworms. This set of genes was most similar to that found in protozoans (single-celled organisms), followed by multicellular organisms (multicellular organisms with well-differentiated cells, including humans and other animals).
Homological and phylogenetic analysis of the resulting set of genes revealed several genes (and their corresponding proteins) involved in the destruction of microtubules. Among them, the most important were katanin p60, kinesin, and calcium signaling proteins. Catanine p60 is involved in the control of the length of the axopodium.
Among the identified kinesins, kinesin-13, a major microtubule destabilizing protein, has been found to play an important role in the rapid contraction of axopodia. Calcium signaling genes regulate the entry of calcium ions into the cell from its environment and trigger the withdrawal of axopodia.
The researchers also noticed the absence of genes associated with the formation and motility of flagella, indicating that sunworm axopodia did not evolve from flagella. Although many genes remain unclassified, the newly identified set of genes will serve as a guide for future research aimed at understanding their axopodial mobility.