IDENTIFICATION AND CELLULAR-DISTRIBUTION OF DISTINCT PROTEINS FORMING HUMAN GM-CSF RECEPTOR

Two proteins forming the receptor for human granulocyte-macrophage colony-stimulating factor (GM-CSF)1 were identified and characterized. One with apparent Mr of about 80 000 was defined as α-chain and has Kd of 0.7-2.8 nM. The other binding molecule with apparent Mr of about 135 000 was defined as β-chain and is related to the high-affinity binding with Kd of 10-40 pM. The binding kinetic studies confirmed that the 125I-GM-CSF associated slower to and dissociated more rapidly from the α-chain than the β-chain. The α-chain is expressed not only on hemopoietic cells but also on full-term placental tissues, choriocarcinoma cells, and other solid tumor cells. In contrast, the distribution of the β-chain is restricted on hemopoietic cells. The α-chain probably corresponds to the low-affinity GM-CSF receptor whose cDNA has been cloned and sequenced. © 1990 by The American Society for Cell Biology.