Recombinant Human OSMR beta Protein, CF

OSM R beta is a 150 - 180 kDa member of the IL-6 receptor family. It associates with gp130 to form the type II OSM receptor that is responsive to OSM. The gp130 subunit is shared by other IL-6 family cytokine receptors (1, 2, 3, 4), and OSM R beta associates with gp130-like receptor (GPL) to form a receptor complex responsive to IL-31 (5, 6). The human OSM R beta cDNA encodes a 979 amino acid (aa) precursor that includes a 27 aa signal sequence, a 712 aa extracellular domain (ECD), a 22 aa transmembrane segment, and a 218 aa cytoplasmic domain. The ECD contains one partial and one complete hematopoietin domain, an Ig-like domain, and three fibronectin type-III domains. The cytoplasmic domain contains box1, 2, and 3 motifs (7). Within the ECD, human OSM R beta shares 55%, 58%, 61%, and 72% aa sequence identity with mouse, rat, bovine, and canine OSM R beta, respectively. It also shares 31% aa sequence identity with human LIF R, but less than 20% aa sequence identity with human CNTF R alpha, G-CSF R, IL-6 R, IL-11 R alpha, and TCCR. OSM R beta does not bind cytokines directly, but increases the affinity of gp130 for OSM, and GPL for IL-31 (7, 8). OSM R beta, gp130, and GPL each initiate signaling events following ligand stimulation (9, 10). Jak/STAT and MAPK pathways are activated by OSM R beta -containing receptors (9, 11, 12, 13), including STAT5b and SHC which are not activated by other IL-6 family receptors (10, 13). In mice, the loss of OSM R beta expression blocks erythroid progenitor development in bone marrow, and dramatically reduces the number of circulating platelets and erythrocytes (14). The type II OSM receptor is the only IL-6 family receptor that promotes osteoblast differentiation in calvaria cell cultures (15).