Some RNA Molecules Have Unexpected Sugar Coating
Sugars attach to certain RNA molecules on the outside membrane of the cell. The newly discovered “glycoRNAs” may be involved in immune signaling.
In a surprise find, scientists have discovered sugar-coated RNA molecules decorating the surface of cells.
These so-called “glycoRNAs” poke out from mammalian cells’ outer membrane, where they can interact with other molecules. This discovery, reported May 17, 2021, in the journal Cell, upends the current understanding of how the cell handles RNAs and glycans.
“This was probably the biggest scientific shock of my life,” says study author Carolyn Bertozzi, a Howard Hughes Medical Institute Investigator at Stanford University. “Based on the framework by which we understand cell biology, there’s no place where glycan sugars and RNA would physically touch each other.”
Normally, RNA is made in the nucleus and transported to the cytoplasm, where it serves as a template for making proteins. Until now, scientists thought glycans were kept separate. But the new work suggests that the two molecules actually meet up, and the sugar-coated RNAs take a trip to the cell surface.
Bertozzi’s team’s initial findings drew considerable attention when she posted them on the preprint server bioRxiv.org in 2019. Now, the scientists report a new physical position for the glycoRNAs, opening a possible role for the sugar-coated RNAs in immune disease.
A molecule that shouldn’t exist
Researchers have been studying “glycobiology” for decades. Sugars serve a key role in cellular communication, among other functions. Previously, scientists had found glycans attached to proteins and fats. Glycomolecules even stud the cell walls of bacteria and fungi, helping cells communicate and infect their hosts.
Until now, glycobiology and RNA biology did not overlap. Scientists in the two fields use different chemistry and techniques to study their molecules. Study coauthor Ryan Flynn, who spent his graduate school years working on RNA, hadn’t encountered glycobiology until a chance meeting with a student in Bertozzi’s lab. “Glycans are critical in biology, and I somehow didn’t know anything about them,” he says. Flynn was intrigued.