Purity ~90% (SDSPAGE). Neuronal Pentraxin (NPTX2), also called NP2 or NARP (neuronal activityregulated pentraxin) is a 46-60kD secreted glycoprotein within the Pentraxin family (1-4). Neuronal pentraxins include NPTX1 and NPTX2, both secreted proteins, and NPTXR (Neuronal Pentraxin Receptor), which is found in type II transmembrane or cleaved, soluble forms (1-5). Circulating NPTX2 forms disulfide-linked 250kD homopentamers, while at excitatory synapses it can form heteropentamers and larger clusters with NPTX1 and NPTXR (1-5). The clusters promote synaptogenesis by recruiting subunits of AMPA-type glutamate receptors (AMPAR) (4-6). Of the three neuronal pentraxins, only NPTX2 shows immediate-early expression induced by synaptic activity (5, 6). Human NPTX2 is synthesized as a 431 amino acid (aa) protein with a 15 aa signal sequence and a 416 aa secreted mature protein that contains a calcium binding Pentraxin domain. Mature human NPTX2 shares 96% aa sequence identity with mouse, rat