The Superfamily of Receptors for Growth Hormone,Prolactin,Erythropoietin,and Cytokines

Concurrent studies conducted in several laboratories in the late 1980s led to cloning, expression, and characterization of the receptors to growth hormone (GH), prolactin (PRL), erythropoietin (EPO), interleukin (IL)-4, IL-7, and granulocyte-macrophage colony-stimulating factor (GM-CSF). In 1989-90 these were recognized as a novel family of growth factor receptors, followed by an explosion of publication in the field and extension of the family to include several other growth factors, mostly cytokines. These receptors were found to have a high degree of homology in sequence motifs of their N-terminal extracellular domains. These extracellular domains were the subject of another important pursuit by investigators: recognizing soluble binding proteins for several of the ligands to the superfamily, with sequence identity to the extracellular domains of the receptors.