Coexisting despite limited resources: cell architecture renewal reduces competition and fosters diversity
Competition for resources exists at all levels of nature, even within cells. A new study by French and American researchers provides a better understanding of how, in cells, different cellular architectures competing for the same resources – actin proteins – manage to coexist. They have shown that the constant renewal of these cell architectures is the mechanism that reduces competition between them and fosters their diversity. These results shed new light on the use of actin in cells and could help researchers seeking to develop functional synthetic systems with limited resources.
Actin proteins, present in all eukaryotic cells, are involved in a large number of cellular structures essential to the cell. They are, for example, the building blocks of lamellipodia, structures on the leading edge of the cell that help it move; stress fibres that play a role in the cell’s adhesion to the substrate and in its motility; and the cortex, an actin layer under the membrane that gives the cell its shape.
The amount of actin available for these structures is limited in cells. But despite strong competition for resources, they manage to coexist. In a recent study published in Current Biology, the CytoMorpho Lab, in collaboration with Alex Mogilner, sought to understand what ensures the coexistence of multiple actin architectures in cells and how they share resources. They demonstrated that actin turnover is what, to a certain extent, makes this coexistence possible.
“Actin turnover is the constant assembly and disassembly of actin structures in cell,” explained Alexandra Colin, one of the publication’s authors. “It allows them to adapt to changes that the cell senses.” The constant renewal of structures is an essential feature of living systems, and according to the new study, it helps maintain the diversity of competing structures.
Protein turnover allows strong and weak actin structures to coexist
For this study, the team used moving beads introduced into cell-sized closed microwells, which, in the presence of actin, are able to grow actin architecture on their tails. They then tested their system by varying a number of parameters: the number of actin components available, the number of actin architectures in the system, the strength of these structures (having weak and strong networks by varying the density of protein on the beads) and observed how the architectures developed without or without protein turnover.
Source: Christophe Guérin, Anne-Betty N’Diaye, Laurène Gressin, Alex Mogilner, Manuel Théry, Laurent Blanchoin, Alexandra Colin,
Balancing limited resources in actin network competition,
Current Biology, Volume 35, Issue 3,
2025
Without renewal, the strongest take all
In the absence of turnover, the size of the actin structures was defined by the limited actin pool. When the beads had the same density, the structures needed the same amount of actin and shared resources equally. When the protein density on the beads was different, the high-density beads – at the origin of the strong actin networks – took up all the resources and the weak networks were unable to develop.
With renewal, coexistence is possible
With turnover, the structures disassembled and released actin monomers that could be used again by other networks. The pool of available components was, therefore, larger, allowing weaker networks to coexist with stronger ones. However, when competition was too intense or the rate of turnover too slow, the pool once again became limiting and the system favoured the strongest networks.
“This experiment shows that turnover is essential to maintain the coexistence of actin structures and that the pool of actin components has a limiting role on the size of the networks. In cells, there is probably a compromise between the number of competing structures and the size of the pool,” added Alexandra.
The next steps: pushing the system to its limits, observing what happens in the cells and developing a competition model
The team have several leads they would like to pursue: firstly, to observe what happens in cells when their actin reserve is reduced. Secondly, they also plan to test their biomimetic system further by pushing it to its limits. What happens when the competition is too strong? Does the system oscillate or does it favour the same networks? How does the system adapt to perturbations, such as the addition of actin networks or a change in actin concentration?
The researchers are also working on a mathematical model to explain this competition. Competition for resources exists at all levels in nature, between species, between organs of a body or cells of a tissue. This study echoes the competition we observe on a larger scale, highlighting the importance of the renewal and redistribution of resources to maintain coexistence.
“We’ve been working for a long time with our collaborator Alex Mogilner. Together, we’re building a competition model and I’d love us to come up with a model that works on all scales of life,” concluded Alexandra.