Neurexin 2, also known as NRXN2, is a neuronal type I transmembrane molecule that is encoded by one of three Neurexin genes (1, 2). Mature human Neurexin 2a is an ~200kD N- and O-glycosylated protein with a 1608aa extracellular domain (ECD) and a 55 aa cytoplasmic domain. The ECD contains six LNS domains interspersed with three EGF-like domains and a juxtamembrane O-glycosylation region (1-3). The ECD of human Neurexin 2a shares 98% and 99% aa sequence identity with mouse and rat Neurexin 2a, respectively. Transcription of the Neurexin 2 gene from an internal promoter gives rise to Neurexin 2B which lacks the first five LNS domains and all of the EGF-like domains (3, 4). Human Neurexin 2a is combinatorially spliced at five canonical sites in the ECD, giving rise to nearly 200 potential isoforms (4). This recombinant protein (isoform 2 according to SwissProt Q9P2S2) does not contain inserts at splice sites 1, 2, 3,or 4. Neurexin 2a is primarily expressed in the brain where it is localized to presynaptic terminals (3, 5, 6). It binds Neurexophilin 1 and 3, Neuroligin 2, and Dystroglycan (7-9). Only Neurexin 2 isoforms that lack the insert at splice site 4 additionally bind LRRTM2 (10). The interaction between Neurexins and Neuroligins is complex and is restricted to particular combinations of splice forms of each binding partner (11). These interactions promote the differentiation and maintenance of postsynaptic GABA and NMDA but not AMPA terminals (8, 12). At presynaptic terminals as well as in pituitary melanotrophs, alpha Neurexins are required for coupling voltage- dependent calcium channel signaling to neurotransmitter or hormone release (13-15). Recombinant corresponding to human Neurexin 2 alpha Isoform 2 Fc Chimera at (Met1 - Thr1566) N-terminus and Human IgG1 (Pro100-Lys330) at C-terminus, expressed in CHO cells. Molecular Weight: ~193kD Biological Activity: Measured by its binding ability in a functional ELISA. When recombinant human NRXN2a Fc Chimera is coated at 2ug/ml, biotinylated recombinant rat NXPH-1 binds with an apparent KD <10nM. Storage and Stability: Lyophilized and reconstituted products are stable for 6 months after receipt at -20C. Reconstitute with sterile PBS. Aliquot to avoid repeated freezing and thawing. Store at -20C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer.
