The intense heat, the emptiness of space, the drought… no environment seems to be a problem for tardigrades. These arthropod cousins measuring less than two millimeters are called “extremophiles”: they are adapted to conditions in which most other organisms cannot survive. So when tardigrades are under stress, such as dehydration, they enter a state in which their metabolism shuts down. Then they are able to survive for years. In some species, it is a sugar, trehalose, which allows them to resist. Trehalose replaces water molecules and protects membrane tissues in particular. However, in Ramazzottius varieornatusOne of the most resistant, and other proteins, is the one that gets to work: CAHS. Takekazu Kunieda’s team from the University of Tokyo identified the mechanism involved.
CAHS history begins with cotton. In 1981, scientists discovered proteins, LEAs, expressed around cottonseed embryos. These particles protect the seeds from drying out. This is what prompted Takekazu Kunieda to search for equivalent proteins in tardigrades,” says Simon Gallas, of the University of Montpellier and the CNRS-IBMM laboratory. The Japanese biologist then identified CAHS, a group of tardigrade-specific proteins, that are unlike any known protein and which Their biochemical properties are similar to those of LEAs.In particular, like LEAs, they remain soluble in water even at very high temperatures, indicating that they are highly hydrophilic.Furthermore, when the expression of CAHS proteins is blocked, they are sluggish The gait is less resistant to desiccation.So the CAHS had all the characteristics to protect these animals from dehydration.It remains to be determined by which mechanism…
This is the mechanism Takekazu Kunieda’s team has just highlighted: The researchers showed that CAHS proteins change their structure in the face of stress. From a flat shape, a beta leaf, they change into a snail shape, an alpha helix. Then these spirals come together from head to tail and form fibres. “When the tardigrade is put back into a moistened medium, the fibers disappear,” explains Simon Gallas. By showing that it is possible to make a gel with these proteins, Takekazu Kunieda’s team proposes that these fibers allow the tardigrade to keep its cellular structure intact, and to retain a little water. »
This discovery helps to better understand how tardigrades function Ramazzottius varieornatus Survive in harsh environments. But it could also have consequences in the medical field: “Patents have already been filed in the US for the use of CAHS to preserve therapeutic proteins: antibodies, hormones, etc,” Simon Gallas specifies. Currently, these therapeutic proteins require ultra-cold freezers, at -80 °C, to be well preserved. So the use of CAHS characteristics will save a lot of energy.
And this probably won’t be the last time tardigrades provide science. There are over 1,400 species of tardigrades, and only 4 have their genomes fully decoded. With so many genes yet to be sequenced, expect new surprises.
