Structural, functional, and evolutionary characterization of novel membersof the allatostatin receptor family from insects

By using degenerate primers based on known mammalian somatostatin receptors and the recently identified Drosophila allatostatin receptors (AlstR), we have cloned a novel receptor for the neuropeptide, allatostatin, from the c ockroach Periplaneta americana. The receptor exhibits about 60% amino acid identity in the transmembrane regions when compared to the two known AlstRs from Drosophila melanogaster. In addition, two cDNA fragments were obtaine d from the stick insect Carausius morosus, one of which is similar to Droso phila AlstR, whereas the other is more similar to mammalian somatostatin re ceptors. Functional expression in Xenopus oocytes shows that the Periplanet a-AlstR exhibits high affinity to endogenous cockroach allatostatin peptide s. Studies with. synthetic peptides demonstrate that agonistic activity is mediated by the conserved C-terminal pentapeptide YXFGL-amide; in this sequ ence, amidation of the C-terminus is obligatory to maintain affinity. Thus, our studies provide a molecular basis for understanding the widespread bio logical activities of the allatostatin peptides. (C) 2001 Academic Press.