Neurexin

A neurexin (NRXN) is a presynaptic protein that helps to glue together neurons at the synapse. Neurexins are type I membrane proteins that can be classified into two types, α-NRXNs and β-NRXNs. The α-NRXNs are larger and have different amino-terminal extracellular sequences. Neurexins mediate signaling across the synapse, and affect the properties of neural networks by specifying synaptic functions. In humans, alterations in genes encoding neurexins are implicated in autism and other cognitive diseases.

Neurexins were discovered as receptors for α-latrotoxin, a toxin in black widow spider venom. Their functional roles in insects are likely similar to those in vertebrates.

β-Neurexins (located presynaptically) act as receptors for neuroligin (located postsynaptically). Neurexin and neuroligin "shake hands," resulting in the connection between the two neurons and the production of a synapse. Additionally, β-Neurexin has also been found to play a role in angiogenesis.

The neurexin genes are NRXN1, NRXN2, and NRXN3.