Cloning and Expression of a cDNA Encoding a Prolactin Receptor of the Japanese Red-Bellied Newt, Cynops pyrrhogaster

Abstract

Primary structure of a newt prolactin receptor (nPRL-R) was deduced from a cDNA clone isolated from a kidney cDNA library as well as from a polymerase chain reaction (PCR) product. The predicted nPRL-R protein was composed of 626 amino acids (aa), and contained a signal sequence and a transmembrane region. The extracellular domain had two pairs of cysteine residues and a WSXWS motif. The cytoplasmic domain comprised 368 residues and contained both box 1 and box 2 sequences which are considered to be required for the signal transduction of the cytokine/growth hormone (GH)/PRL-R family in mammals. The nPRL-R shares 50-52% protein sequence identity with mammalian PRL-Rs. When nPRL-R was expressed in COS-7 cells, specific binding of [125I] rat prolactin (PRL) was observed. Northern blot analysis revealed the existence of a single transcript, more than 10 kb in length, which was expressed in the kidney and brain. Reverse transcription-polymerase chain reaction (RT-PCR) analysis revealed the expression of PRL-R mRNA in the testis, ovary, liver and bladder of the newt. This is, as far as we know, the first report of cloning on amphibian PRL-R.