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Two lambda gt11 clones containing fragments of cDNA encoding the prolactin receptor from rabbit mammary gland were isolated using a rat liver prolactin receptor cDNA probe. An 1848-base-pair open reading frame encodes a mature prolactin-binding protein of 592 amino acids that contains three domains: (i) the extracellular, amino-terminal, prolactin-binding region of 210 residues; (ii) the transmembrane region of 24 residues; and (iii) the intracellular, carboxyl-terminal domain of 358 residues. This latter domain is much longer than the cytoplasmic domain (57 residues) previously described for the rat liver prolactin receptor...

The binding characteristics of IGF1 on membranes prepared from 5 human breast cancer cell lines were investigated in detail. The presence of one class of high affinity IGF1 binding sites was demonstrated (BT-20: n = 230 fmol/mg protein, Ka = 0.7 nM-1; MCF-7: n = 124 fmol/mg protein, Ka = 1 nM-1; T-47D: n = 61 fmol/mg protein, Ka = 1.1 nM-1; HBL-100: n = 18 fmol/mg protein, Ka = 3.2 nM-1; MDA-MB-231: n = 7 fmol/mg protein, Ka = 2.8 nM-1). Chemical cross-linking of 125I IGF1 to breast cancer cell membranes then sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed one major band of relative molecular weight 130000...

The expression of the prolactin (PRL) receptor gene was studied in rabbit tissues by Northern blot and S1 mapping analysis of mRNA preparations. Rabbit mammary gland contained three major (10.5, 3.4, and 2.7 kb) and one minor (6.2 kb) prolactin receptor poly(A)+ RNA transcripts all of which contain the entire coding sequence of the long form of PRL receptor. Each of these mammary mRNAs hybridized equally well with cDNA sequences encoding either the NH2 terminal, middle, or COOH terminal part of the rabbit mammary PRL receptor...