Light can be a powerful tool for manipulating molecular events. It is noninvasive, relatively straightforward to use, and can provide excellent spatial and temporal control. A light activation tool has been developed at the University of Geneva that can control both the activity and localization of various types of molecules in vivo. The tool could enable researchers to control a molecule at a specific location in a living organism without affecting the surrounding cells. It could be used for both research and medical treatments such as those for skin cancer. The researchers initially set out to modify a well-characterized inhibitor of Polo-like kinase 1 (Plk1). Their aim was to develop a way to control the activation and inactivation of a protein at a specific location within the organism, to better understand its functions. A simple pulse of light can control the activity of a molecule at a specific location without affecting surrounding cells, thereby limiting unwanted side effects. Courtesy of Gotta Lab/UNIGE. “Everything started from this methodological question,” professor Monica Gotta said. “We were looking for a way to inhibit a protein involved in cell division, the Plk1 protein, when and where we wanted, to better understand its function in the development of an organism.” The researchers attached the same coumarin photolabile protecting group (PPG) at two different positions of the PLk1 inhibitor. One photocage was attached at a position important for the binding to and inhibition of Plk1, enabling temporal control of the protein. The other coumarin photocage masked an added carboxylic acid, which, once unmasked, would lead to cellular retention. “After a complex process, we were able to block the active site of our inhibitor with a coumarin derivative, a compound naturally present in certain plants. This coumarin could then be removed with a simple light pulse,” researcher Victoria von Glasenapp said. The team developed a way to anchor the inhibitor at the exact point in the organism where activation was desired. Exposure to light resulted in the removal of both PPGs, leading to the activation of the inhibitor and its trapping inside cells. Professor Monica Gotta, Department of Cell Physiology and Metabolism, Faculty of Medicine, UNIGE. Courtesy of UNIGE. “We thus modified the inhibitor so that it becomes trapped in the targeted cell by adding a molecular anchor that is released only by light,” professor Nicolas Winssinger said. “This enabled us to activate and anchor the inhibitor with the same light pulse, thereby inactivating Plk1 and stopping cell division at the precise desired location.” The researchers demonstrated the efficacy of the caged inhibitor in 3D spheroid cultures. By uncaging it with a single light pulse, they were able to inhibit Plk1 and arrest cell division, a highly dynamic process, with a high degree of spatiotemporal control. The approach could be extended to other small molecules where spatial and temporal regulation of molecular activity is required, opening new routes for controlled drug targeting in more complex systems and improving the precision of drug delivery. In the future, a laser could be used to activate a treatment exactly where it was needed, while sparing the surrounding healthy tissue, thereby limiting undesirable side effects. “We hope that our tool will be widely used, leading to a better understanding of how living organisms function and, in the long term, to the development of location-specific treatments,” Gotta said. The research was published in Nature Communications (www.doi.org/10.1038/s41467-025-56746-5).