Oncostatin M

Oncostatin M, also known as OSM, is a protein that in humans is encoded by the OSM gene.

OSM is a pleiotropic cytokine that belongs to the interleukin 6 group of cytokines. Of these cytokines it most closely resembles leukemia inhibitory factor (LIF) in both structure and function. However, it is as yet poorly defined and is proving important in liver development, haematopoeisis, inflammation and possibly CNS development. It is also associated with bone formation and destruction.

OSM signals through cell surface receptors that contain the protein gp130. The type I receptor is composed of gp130 and LIFR, the type II receptor is composed of gp130 and OSMR.

Discovery, isolation and cloning

The human form of OSM was originally isolated in 1986 from the growth media of PMA treated U-937 histiocytic lymphoma cells by its ability to inhibit the growth of cell lines established from melanomas and other solid tumours. A robust protein, OSM is stable between pH2 and 11 and resistant to heating for one hour at 56 °C. A partial amino acid sequence allowed the isolation of human OSM cDNA and subsequently genomic clones. The full cDNA clone of hOSM encodes a 252 amino acid precursor, the first 25 amino acids of which functions as a secretory signal peptide, which on removal yields the soluble 227 amino acid pro-OSM. Cleavage of the C-terminal most 31 residues at a trypsin like cleavage site yields the fully active 196 residue form. Two potential N-glycosylation sites are present in hOSM both of which are retained in the mature form.