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 (By similarity). Very weak binding, if any, with CBLN4 (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). 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. Produced by alternative splicing. Produced by alternative splicing. Produced by alternative splicing. Belongs to the neurexin family.