Neuronal cell surface protein that may be involved in cell recognition and cell adhesion. May mediate intracellular signaling (By similarity). The laminin G-like domain 2 binds to NXPH1. Specific isoforms bind to alpha-dystroglycan. The cytoplasmic C-terminal region binds to CASK (By similarity). A number of isoforms, alpha-type and beta-type are produced by alternative promoter usage. Beta-type isoforms differ from alpha-type isoforms in their N-terminus. Brain and arteries (at protein level). Produced by alternative splicing. Belongs to the neurexin family. Contains an insert which is not supported by any other transcript and which does not match with the genome.