LEUKEMIA INHIBITORY FACTOR (LIF) AND ONCOSTATIN-M (OSM) HIGH-AFFINITYBINDING REQUIRE ADDITIONAL RECEPTOR SUBUNITS BESIDES GP130 AND GP190

The structure of Leukaemia Inhibitory Factor (LIF) and Oncostatin M (O SM) receptors is not completely resolved. Heterodimerization of gp190 and gp130 has been proposed to form a high affinity receptor (type I) shared by LIF and OSM, while heterodimerization of gp130 with an as ye t unidentified subunit is proposed to form a high affinity OSM recepto r (type II) not shared by LIE We have analysed the binding stoichiomet ries, cross-competition properties and cross-linking pattems of LIF an d OSM to the choriocarcinoma JAR cell line. The data obtained are not fully accounted for by the model proposed above. They indicate rather that third chains of 140-150 kDa molecular mass, in addition to the gp 130 and gp190 subunits, enter in the structure of LIF and OSM high aff inity receptors. These results were strongly supported by transfection experiments in CHO cells. CHO cells co-transfected with the human gp1 90 and gp130 cDNAs expressed high affinity LIF receptors but no high-a ffinity OSM receptors, indicating that an additional component is requ ired for high affinity OSM binding. High-affinity LIF cross-linking on these cells also showed the association of LIF with a 150 kDa compone nt in addition to the gp130 and gp190 subunits. (C) 1996 Academic Pres s Limited