Neuronal cell surface protein that may be involved in cell recognition and cell adhesion. May mediate intracellular signaling (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 promoter usage. Belongs to the neurexin family.