Taking a Toll on neurons

Battling pathogens and shaping neuronal growth seem to have as much in common as accounting and skydiving. But both tasks involve one of the Toll-like proteins, as Ma et al. report on page 209. The study is the first to discover a function for a member of the Toll-like family within neurons.

Toll-like receptors (TLRs) enable mammalian immune cells to identify interlopers. TLR8, for instance, recognizes RNA on the loose, a sign of viral infection or cell destruction. The Drosophila equivalents of the proteins, the Toll receptors, also supervise synapse formation and axon growth, researchers have discovered. Although previous studies had revealed that mammalian neurons manufacture TLRs, no one had shown that the molecules performed a job in these cells.

Ma et al. found that brain levels of TLR8 shot up in the...