Department of Pharmacology, Faculty of Pharmaceutical Sciences, Niigata University of Pharmacy and Applied Life Sciences, 265-1 Higashijima, Akihaku, Niigata 956-8603, Japan.
Based on radio-ligand binding and molecular modeling studies, sarpogrelate shows a moderate selectivity for 5-HT(2B) versus 5-HT(2A) receptors. To confirm the modeling data of sarpogrelate to 5-HT(2B) receptors predicting interaction of sarpogrelate towards Asp135 in helix 3 of 5-HT(2B) receptors, we constructed and characterized the mutation of this residue by site-directed mutagenesis. The Asp135Ala mutant did not exhibit any affinity for [(3)H]rauwolscine. Therefore, it was not possible to find sarpogrelate affinity to the mutant using [(3)H]rauwolscine. The mutation also abolished agonist-stimulated inositol phosphates formation. These results provide evidence that Asp135 is important for the interaction between 5-HT(2B) receptors and sarpogrelate.