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. Isoforms alpha 4B bind to alpha-dystroglycan. The cytoplasmic C-terminal region binds to CASK. Some isoforms seems to be secreted. There are five major alternatively spliced sites, each of which may be spliced in up to twelve different ways. Combinatorial splicing at each of these five sites may lead to the generation of at least 288 isoforms but for simplicity only individual splice events are explicitly described below. Isoforms Alpha 5A to isoform Alpha 5H lack the transmembrane domain. Experimental confirmation may be lacking for some isoforms. Brain. Belongs to the neurexin family.