“We have put our finger on something enormous”says enthusiastically Manuel Théry, researcher at the Atomic Energy and Alternative Energies Commission of the Higher School of Physics and Industrial Chemistry of the city of Paris, meeting in a cafe. He wears a T-shirt that reveals the central object of his discovery: a microtubule. These tubular protein filaments, 25 nanometers in diameter, are essential parts of cells. On these “rails,” other molecules transport proteins from one place to another in the cell.
Its network organization also forms the skeleton of cells, to allow them to change shape, move forward and also divide in two. In short, a link as fundamental as other compounds, such as the nucleus that contains DNA, mitochondria or other ribosomes… but which remains largely misunderstood. How does this network grow, capable of repairing itself, growing or contracting, in an orderly manner?
Manuel Théry, although he is far from having the answer, believes that he is on a serious path. With his Parisian team, that of the Interdisciplinary Research Institute of Grenoble and the Collège de France, he demonstrated how microtubules can self-organize in the cell. About the movies, attached to the article published in the magazine PNAS From November 25, detailing their experiments, small yellowish tubes 10 micrometers long move like cars at about 100 nanometers per second in all directions, without order. Suddenly, like ice petrifying a puddle, the circulation freezes.
Elongated sugar bag
The microtubules are stacked on top of each other and their long stacks close on themselves. The space is divided into violet and cyan-blue regions, separated by walls of microtubules. The mosaic, in certain places, evokes Christmas garlands, bristling with microtubules.
The spectacle is all the more beautiful for a biologist because he recognizes the structures adopted by microtubules in cells. But the study is not about real cells, but about model systems with a minimum of ingredients that make up four families. Microtubules obviously. Then there are two types of “motors,” kinesins (a protein), that rotate on these tubes in one direction (“plus” motor) or the other (“minus” motor). And, last ingredient, a lipid membrane on which the motors wander randomly when they are not on a microtubule.
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