Neuronal cell surface protein that may be involved in cell recognition and cell adhesion. May play a role in angiogenesis (By similarity). Weakly interacts with CBLN1 and CBLN2 (PubMed:21410790, PubMed:22220752, PubMed:29782851). Very weak binding, if any, to CBLN4 (PubMed:22220752, PubMed:29782851). 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. Proccessed by alpha-secretase leading to the formation of an extracellular soluble protein as well as a C-terminal membrane-embedded fragment (CTF). Proteolysis of these CTFs by gamma-secretase releases intracellular domains (ICDs) and extracellular peptides (By similarity). Belongs to the neurexin family.