Biological activities of the allatostatin family of peptides in the cockroach, Diploptera punctata, and potential interactions with receptors

Allatostatins are a family of peptides that inhibit the production of:juven ile hormone in the cockroach, Diploptera punctata. It is likely that the al latostatin prohormone precursor is processed to give rise to all 13 members of the family simultaneously. All members of the family show potency and e fficacy, in terms of their ability to inhibit juvenile hormone production, albeit with dramatically different IC50 and ED50 values, ranging from a max imum of 0.014 nM for Dippu-AST 2 to 107 nM for Dippu-AST 1 (ED50). The like ly occurrence of all 13 peptides in tissues and in haemolymph suggests that they may act in concert to produce physiological effect We have employed c ombinations of the allatostatins, including a cocktail of all 13, 12 (minus Dippu-AST 2) and 11 (minus Dippu-AST 2 and 5) as well as mixtures of high and low activity allatostatins (Dippu-AST 5 plus either Dippu-AST 1 or 13) in dose-response studies to examine the possibility of synergistic or addit ive effects of the peptides on biological activity. None of the peptide com binations yielded evidence of synergistic interactions between allatostatin s. However, the data do provide insight into receptor-ligand interactions i n cockroaches and suggest the allatostatins regulate JH biosynthesis throug h a complex mix of differing affinity interactions with receptors in the co rpora allata. (C) 2000 Elsevier Science Ltd. All rights reserved.