Maurizio Morri – Science Blog

In the last two weeks researchers at the CSIR Centre for Cellular and Molecular Biology in Hyderabad revealed a striking new insight into how our cells change shape and move in response to stress or infection. Cell movement has always been known to depend on actin filaments, the thin protein strands that push out the cell membrane and allow it to crawl forward. What was less clear was how these filaments start forming so quickly and in such a precise pattern.

The team discovered that a protein called SPIN90 is the missing link. Working together with the Arp2/3 complex, SPIN90 initiates the very first actin filaments at a distinctive angle of about 150 degrees. That geometry is not random. It sets up a scaffold that branches rapidly, giving the cell the structure it needs to surge toward wounds, invading microbes, or other signals that demand a fast response.

Using cryogenic electron microscopy the researchers were able to see this process unfold at near atomic detail. They captured SPIN90 guiding the first steps of filament growth and creating the conditions for an entire actin network to bloom almost instantly. The discovery helps explain how immune cells can chase pathogens so quickly, how tissues repair themselves after injury, and even how cancer cells sometimes manage to invade new environments.

The implications are broad. If scientists can learn how to influence SPIN90’s activity they may eventually be able to control cell movement in therapeutic ways, slowing down invasive tumors or boosting the ability of immune cells to reach infection sites. At the same time the finding highlights just how much remains unknown in the everyday workings of our own cells. What turns SPIN90 on or off, how the angle of filament growth is controlled, and whether this mechanism changes across different cell types are questions that remain wide open.

This discovery is a reminder that even the most fundamental processes in biology still hold surprises, and that with new imaging technologies we can see details of life that were invisible until now.

Francis J, Pathri AK, Shyam KT, Sripada S, Mitra R, Narvaez-Ortiz HY, Eliyan KV, Nolen BJ, Chowdhury S. Activation of Arp2/3 complex by a SPIN90 dimer in linear actin-filament nucleation. Nature Structural & Molecular Biology. 2025 Sept 15. DOI: 10.1038/s41594-025-01673-8 Nature+1

“CCMB scientists uncover how cells reshape to fight disease.” Times of India, reported Sep 16, 2025. The Times of India

Liu T, Cao L, Mladenov M, Way M, Moores CA. Arp2/3-mediated bidirectional actin assembly by SPIN90 dimers in metazoans [preprint]. bioRxiv. 2025 Jan 31. DOI: 10.1101/2025.01.31.635869 BioRxiv+1