Expression of multiple forms of the prolactin receptor in mouse liver

We have characterized the PRL receptor (PRL-R) present in mouse liver by purification, cross-linking, and immunological analysis of the protein, and by the isolation of PRL-R cDNA clones. Analysis of the cDNA clones indicates that the liver receptor is actually a family of proteins. Two of these proteins are predicted to be synthesized as precursors of 303 and 292 amino acids, with common signal sequences, extracellular domains, and transmembrane domains; a portion of their cytoplasmic domains are also identical, but these proteins differ markedly in the terminal region of this domain. A third PRL-R protein is predicted to be a truncated form and may be secreted. These multiple PRL-R mRNAs appear to be encoded by at least two genes, with the sequence variation for the two full-length proteins likely due to alternative RNA splicing. These results suggest that the varied actions of PRL may involve multiple receptors that are part of distinct signal transduction pathways.