Retrograde Signaling by the Neurotrophins Follows a Well-worn Trk

The mechanism that allows a neuron to send cues received at its terminal to its cell body and nucleus has proved elusive. However, a recent study by Howe and colleagues indicates that neurotrophin signaling via the trkA receptor requires formation of a signaling endosome containing NGF and trkA. Thus, endocytosis of the neurotrophin-receptor complex is a crucial step in the generation of intracellular signaling platforms required for activation and compartmentalization of signaling events.