Podcast Episode
It is as if every time the cell needs to deliver a heavy package, a team of 7 strong couriers work together to do so. Because the package is so heavy, they cannot just drop it all at once and have to lower it in 3 steps. After fusion, a protein called Sec18 mediates the disassembly of the ExHOS structure, ensuring that delivery of molecular packages continues at the required speed.
Though rare, mutations in ExHOS components cause neurodevelopmental disorders in humans, while the nanomachine also participates in cell invasion during cancer metastasis. The function of this nanocourier is so important that it is very rare to find it mutated in patients as its alteration would normally impair the viability of the embryo.
Scientists Discover Cellular Nanomachine That Delivers Molecular Packages Billions of Times Daily
January 17, 2026
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An international research team led by scientists at Pompeu Fabra University in Barcelona has discovered a cellular nanomachine that controls the uninterrupted delivery of molecular packages to cell membranes, a process that occurs billions of times daily in our bodies and is critical for virtually all living organisms. The discovery, published January 16, 2026 in the journal Cell, reveals how 7 protein assemblies form a flexible ring structure dubbed ExHOS that tethers cargo-loaded vesicles to the plasma membrane.
The Nanocourier Unveiled
Despite being one of the largest nanomachines in the cell, its short lifespan and dynamism made it very challenging to capture. Using advanced light and electron microscopes combined with artificial intelligence image analysis, the team resolved the 3D organisation of this nanomachine and filmed how it rapidly changes structure during delivery. Each day, every cell in the human body transports between 10,000 and 100,000 of these spherical packages to the cell surface to secrete enzymes, hormones, repair cellular wounds, and enable growth and division.How ExHOS Works
Collaborators from Universitat de Vic, Instituto Biofisika, and Max Perutz Labs contributed to the discovery. Researchers found that 7 exocysts form a flexible ring that initially measures 19 nanometers in radius, rapidly expands while pulling vesicles toward the membrane, then stabilises to secure vesicles just 4 nanometers from the membrane surface. The process occurs in 3 distinct steps at 27, 18, and 5 nanometers from the plasma membrane.It is as if every time the cell needs to deliver a heavy package, a team of 7 strong couriers work together to do so. Because the package is so heavy, they cannot just drop it all at once and have to lower it in 3 steps. After fusion, a protein called Sec18 mediates the disassembly of the ExHOS structure, ensuring that delivery of molecular packages continues at the required speed.
Medical and Agricultural Implications
The discovery has far-reaching implications for infectious diseases and agriculture. Viruses including SARS-CoV-2 and HIV, along with bacteria like Salmonella, hijack this delivery process during infection. The rice blast fungus Magnaporthe oryzae attacks the ExHOS in plants, causing the loss of up to one third of global rice production annually.Though rare, mutations in ExHOS components cause neurodevelopmental disorders in humans, while the nanomachine also participates in cell invasion during cancer metastasis. The function of this nanocourier is so important that it is very rare to find it mutated in patients as its alteration would normally impair the viability of the embryo.
A New Frontier in Bioimaging
The breakthrough demonstrates the power of integrating imaging technologies with computational tools. The future lies in integrating various imaging technologies with the power of new computational tools like AI to make the invisible visible. Researchers compared the significance of the finding to understanding how oxygen exchange occurs during breathing. It might not have an immediate application, but the discovery of this nanomachine will facilitate future research to find solutions to severe biomedical and biotechnological problems.Research Team
The research was led by Oriol Gallego, leader of the Biophysics in Cell Biology Group at Pompeu Fabra University's Department of Medicine and Life Sciences. Key collaborators included Carlo Manzo of Universitat de Vic, Daniel Castaño at Instituto Biofisika, Jonas Ries at Max Perutz Labs, and co-author Sasha Meek. The study, titled Continuum architecture dynamics of vesicle tethering in exocytosis, was published online January 16, 2026 in Cell.Published January 17, 2026 at 10:34am
