Neuronal cell surface protein that may be involved in cell recognition and cell adhesion. May mediate intracellular signaling. 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. Additional isoforms produced by alternative splicing seem to exist. Expressed in the blood vessel walls (at protein level). Highly expressed in brain, lung, and pancreas; a lower level of expression is detectable in heart, placenta, liver, and kidney, whereas no expression can be observed in skeletal muscle. Isoform 4a is heart-specific. Produced by alternative splicing. Produced by alternative splicing. Belongs to the neurexin family. Extended N-terminus.