Turn-ons for axons

When adult neurons are injured, myelin-associated glycoprotein (MAG) triggers signals to block the regrowth of axons, a process that is intensely frustrating to patients and researchers hoping to treat such injuries. On page 565, Yamashita et al. identify a receptor complex responsible for transducing this signal, elucidate part of the associated intracellular signaling pathway, and uncover a novel molecular interaction that may help explain the diverse activities of a neurotrophin receptor.

MAG signaling is known to inhibit axonal regrowth after injury, but the MAG receptor on neurons remained unknown. By analyzing neurons from wild-type and mutant mice, the authors discovered that p75^NTR, a glycoprotein on the surface of many types of neurons, transduces the MAG signal. Since p75^NTR also binds to neurotrophins, which promote axonal outgrowth, the same receptor seems...