Membrane trafficking of synaptic adhesion molecules

Synapse formation and stabilization are aided by several families of adhesion molecules, which are generally seen as specialized surface receptors. The function of most surface receptors, including adhesion molecules, is modulated in non-neuronal cells by the processes of endocytosis and recycling, which control the number of active receptors found on the cell surface. These processes have not been investigated extensively at the synapse. This review focuses on the current status of this topic, summarizing general findings on the membrane trafficking of the most prominent synaptic adhesion molecules. Remarkably, evidence for endocytosis processes has been obtained for many synaptic adhesion proteins, including dystroglycans, latrophilins, calsyntenins, netrins, teneurins, neurexins, neuroligins and neuronal pentraxins. Less evidence has been obtained on their recycling, possibly because of the lack of specific assays. We conclude that the trafficking of the synaptic adhesion molecules is an important topic, which should receive more attention in the future.