The growth hormone/prolactin receptor gene family.

The identification of cDNAs encoding receptors for growth hormone and prolactin have allowed the identification of the primary structure of these receptors. The expression of these receptors can be measured in various tissues by estimation of mRNA levels using cDNA probes and measurements of protein levels by radioimmunoassay or immunoblot analysis using monoclonal or polyclonal antibodies to the receptors. Site-directed mutagenesis of ligand-binding domains will lead to an understanding of the residues important for hormone binding. In addition, mutagenesis of the cytoplasmic domains of the receptors performed together with functional tests should help identify regions of the receptor involved in the process of signal transduction. Finally, the identification of the enlarged receptor family, including receptors for cytokines, should shed some light on additional functions of growth hormone prolactin, especially in regulating immune functions.