June 22, 2009

Protein neuroligin helps make synapses

U.S. scientists have determined a protein called neuroligin, implicated in some forms of autism, is critical to the construction of a working synapse.

University of California-Davis researchers said they not only discovered neuroligin locks neurons together like molecular Velcro, but they obtained images that are the first to show two neurons coming together, using neuroligin to construct a new synapse.

Previous research has suggested that neuroligin is critical for the formation and stabilization of synapses, said Associate Professor Kimberley McAllister. Our work suggests that neuroligin is one of the first molecules to be recruited to new synapses and that it also acts as Velcro to strengthen those new connections.

Postdoctoral fellow Stephanie Barrow, the lead author of the study, said researchers had hypothesized neuroligin could facilitate the recruitment of other proteins important in building synapses, but no one had been able to directly visualize the process. That, she said, is because synapses are less than 1 micron wide. To view the process, the researchers cultured neurons taken from newly born rats and fluorescently labeled the proteins -- neuroligin, PSD-95 and NMDA -- that are critical to synapse formation.

We are the first to observe that neuroligin zips around dendrites (the branched projections of neurons) before synapses form and can accumulate very soon after contact between cells, Barrow said.

The study appears in the online edition of the journal Neural Development.