Oncostatin M (OSM) is a member of the IL-6 family of cytokines that share the gp130 as a common signal transducing receptor subunit. Human OSM signals through two types of human OSM receptor complexes: the type I complex comprising the Leukemia Inhibitory Factor Receptor beta (LIF R beta ) and gp130, the type II complex made up of OSM Receptor beta (OSM R beta ) and gp130. In contrast, mouse OSM signals only through the mouse OSM R beta and gp130 complex. Mouse OSM R beta cDNA encodes a 971 amino acid (aa) residue type I transmembrane protein which contains a 23 aa residue signal peptide, an extracellular domain of 714 aa, a transmembrane domain of 20 aa and a 214 aa cytoplasmic domain. Mouse OSM R beta alone binds mOSM with low-affinity, but forms a high-affinity binding complex in the presence of gp130. Mouse OSM R beta is 55% identical at the amino acid sequence level to human OSM R beta.
