Nedd4 and Nedd4-2: Ubiquitin ligases at work in the neuron

Ubiquitination of proteins by the Nedd4 family of ubiquitin ligases is a significant mechanism in protein trafficking and degradation and provides for tight spatiotemporal regulation. Ubiquitination is gaining increasing recognition as a central mechanism underpinning the regulation of neuronal development and homeostasis in the brain. This review will focus on the Nedd4 and Nedd4-2 E3 ubiquitin ligases that are implicated in an increasing number of neuronal protein–protein interactions. Understanding of the contribution of Nedd4 and Nedd4-2 in regulating key functions in the brain is shedding new light on the ubiquitination signal not only in orchestrating degradation events but also in protein trafficking. Furthermore, the description of several novel Nedd4/4-2 targets in neurons is changing the way we conceptualize how neurons maintain normal function and how this is altered in disease.