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How macromolecules diffuse in cells?

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Within a cell, the transportation of particles is constrained not by obstacles, but by interactions. That is the result demonstrated in Nature Materials by Mathieu Coppey, of the Imaging and Optical Control of Cellular Organization team led by Maxime Dahan.

The inside of a cell is an extremely crowded place, with millions of macromolecules participating in a range of cell functions.  Despite this, it is important for these macromolecules to be able to move freely in order to transport material or convey information. The primary mode of transportation within a cell is diffusion, which results from the passive agitation of molecules. As a result, scientists have long focused on understanding how particles diffuse within a cell. Some work has shown that this diffusion may be extremely limited, while other research has demonstrated that it may be almost as free-flowing as water. How can we reconcile these observations? Is the interior of a cell so dense with obstacles that the system resembles a giant traffic jam? The Light-based Observation and Control of Cellular Organization research team under Maxime Dahan (Institut Curie/UMR168CNRS/UPMC/IPGG/PSL) recently joined forces with a German team to revisit these questions and demonstrated that particles about 10 nanometers in diameter -such as a protein complex- can move around freely if their surfaces react very little with other particles. However, the more they interact non-specifically with the other internal cellular structures and macromolecules, the more limited their diffusion becomes, until they are immobilized. Contrary to prior belief, therefore, obstacles do not prevent movement within a cell. Non-specific interactions, on the other hand, play a critical role. This discovery will undoubtedly have an impact on biotechnologies, because it provides a quantitative charter on the passivation of nano-objects, including in terms of medication release.

Non-specific interactions govern cytosolic diffusion of nano-sized objects in mammalian cells

Fred Etoc, Elie Balloul, Chiara Vicario, Davide Normanno, Domenik Liße, Assa Sittner, Jacob Piehler, Maxime Dahan, Mathieu Coppey

Nature Materials, July 2018, doi.org/10.1038/s41563-018-0120-7

 

Credits: Christophe Hargoues/Institut Curie