Molecular identification of a G protein-coupled receptor family which is expressed in planarians

We identified four guanine nucleotide binding protein (G protein)-coupled receptors from planarians by polymerase chain reaction (PCR) with degenerate primers. They all showed a significant homology to human 5HT1A serotonin receptor and therefore were designated as serotonin receptor-like planarian receptor 1 similar to 4 (5HTLpla1 similar to 4). cDNA clones of 5HTLpla4 and 5HTLpla1 were isolated from the planarian cDNA library and their complete nucleotide sequences were determined. The deduced amino acid sequences of these planarian receptors, which are highly homologous to one another, show significant similarity to that of Drosophila 5HTdrol serotonin receptor. Northern blot analysis revealed that expression of 5HTLpla4 mRNA increased during planarian regeneration, suggesting that 5HTLpla4 might be involved in the regeneration mechanism.