A team of international cell biologists led by the University of Liverpool has solved a scientific mystery that has puzzled researchers for 40 years, revealing an unexpected mechanism that cells use to sense and respond to physical forces.
Published in Proceedings of the National Academy of Sciences (PNAS), the study led by Professor Ben Goult uncovers a previously unknown way in which a key cellular protein, called talin, helps regulate how cells attach to and interact with their surroundings.
Every cell in the body relies on specialised attachment structures to anchor itself to neighbouring tissues and to detect mechanical forces from its environment. These structures are essential for processes ranging from tissue development and wound healing to immune responses.
At the centre of this machinery is talin, a protein that acts as a molecular force sensor. As cells pull against their surroundings, talin unfolds, exposing hidden regions that alter how cellular attachments behave.
The researchers discovered that stretching talin can reveal a previously hidden region that allows talin molecules to bind directly to one another. This force-triggered interaction represents an entirely new mechanism through which cells can respond to mechanical cues.
The finding also resolves a longstanding question in cell biology. In 1986, scientists identified two regions within talin thought to bind integrins, the proteins that anchor cells to their surroundings. One became established as the critical connection between integrins and the cell's force-generating machinery. However, while the second was widely accepted as an integrin-binding site, its precise function remained a mystery.
The new study reveals that rather than functioning primarily as an integrin-binding site, this region allows talin molecules to bind directly to one another. It is, in fact, a talin-binding site.
Importantly, the team found that the region responsible for these interactions shares properties with protein sequences associated with amyloid formation, a process more commonly linked to neurodegenerative diseases such as Alzheimer's.
However, instead of driving harmful protein deposits, the researchers demonstrated that cells harness these molecular properties for a beneficial purpose, using them to regulate how cellular attachments form and respond to force.
The team also found that another protein, vinculin, can break apart these talin assemblies, providing cells with an additional level of control. This allows cells not only to bring talin molecules together in response to force, but also to separate them again when required.
Together, the findings reveal an unexpected mechanism through which cells convert physical forces into changes in behaviour and demonstrate that molecular processes often associated with disease can also play important roles in healthy biological systems.
Professor Ben Goult, who led the research, said: "What we have uncovered is a completely different way in which cells can respond to mechanical forces. Instead of simply exposing a binding site for another protein, stretching talin reveals a region that allows talin molecules to interact directly with each other.
"What is particularly fascinating is that this mechanism uses molecular properties similar to those associated with amyloid formation, but here they appear to be harnessed for a useful biological purpose.
"We usually think about proteins sticking together in this way as something that goes wrong in diseases such as Alzheimer's. What our work shows is that similar molecular behaviour can actually be useful, and that cells have evolved ways to control it. It is a reminder that the same underlying chemistry can have very different consequences depending on how it is used."
The study was an international collaboration involving researchers from the University of Liverpool, the University of Cambridge, the University of Kent, the Mechanobiology Institute at the National University of Singapore, and Tampere University in Finland.
The paper, 'An aggregation-prone region in talin controls talin self-interactions and regulates integrin adhesion complex dynamics', is published in Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.2602326123).
