The fragile X protein — missing in the most common inherited form of intellectual disability — plays a central role in neurons and how they respond to external signals.Â Cell biologist Gary Bassell and his colleagues have been examining how the fragile X protein (FMRP) acts as a “toggle switch.”
FMRP controls the activity of several genes by holding on to the RNAs those genes encode. When neurons get an electrochemical signal from the outside, FMRP releases the RNAs, allowing the RNAs to be made into protein, and facilitating changes in the neurons linked to learning and memory.
The Bassell lab’s new paper in Journal of Neuroscience reveals the role of another player in this process. The first author is postdoctoral fellow Vijay Nalavadi.
The researchers show that neurons modify FMRP with ubiquitin, the cellular equivalent of a tag for trash pickup, after receiving an external signal. In general, cells attach ubiquitin to proteins so that the proteins get eaten up by the proteasome, the cellular trash disposal bin. Here, neurons are temporarily getting rid of FMRP, prolonging the effects of the external signal.