Cloning of a calcitonin gene-related peptide receptor and a novel calcitonin receptor-like receptor from the gill of flounder, Paralichthys olivaceus

For the first time in non-mammalian vertebrates, cDNA encoding CGRPR was isolated from the gill cDNA library of flounder. The nucleotide sequence consists of a 237bp 5'-UTR, a 1398bp coding sequence for a 465-amino-acid protein, and a 981bp 3'-UTR. The predicted amino-acid sequence has a high degree of identity to hCGRPR (72.3%) and rCGRPR (71.6%) and, to a lesser degree, to hCTR (55.6%) and rCTR (59.3%). In addition, a different type of receptor cDNA was also obtained from the gill cDNA. The nucleotide sequence contains an open-reading frame of 1380bp to produce a 459-amino-acid protein. The open-reading frame of this receptor shows the same degree of identity to mammalian CTR (60.2% to hCTR; 62.3% to rCTR) and CGRPR (64.6% to hCGRPR; 64.4% to rCGRPR). However, the predicted amino-acid sequence was more homologous to hCGRPR (60.2%) and rCGRPR (61.3%) than to hCTR (48.8%) and rCTR (49.5%). The identity of this receptor to fCGRPR is 66.6% at the nucleotide level and 64.2% at the amino-acid level, indicating that the receptor is not likely to be an isoform of CGRPR. The receptor, but not fCGRPR, is expressed in bones, suggesting the possibility that this receptor corresponds to the flounder CTR.