Submitted to: Archives of Insect Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 28, 1998
Publication Date: N/A
Interpretive Summary: We previously isolated a peptide from brains of gypsy moths which could induce the testes of males to synthesize the steroid hormone 20-hydroxyecdysone. The steroid hormone is needed for sexual maturation of the testes and the reproductive tract of adult moths. In order to synthesize molecules in the laboratory which would interfere with the action of this hormone or its synthesis in testes, we needed to know which parts of the natural molecule were important to its function. In this work we were surprised to find that several parts of the natural molecule were as active, or even more active, than the whole molecule in inducing steroid hormone production. The activity may be due to actual hormone stimulation by the first half of the natural peptide, and also to calcium movement induced by other parts of the natural molecule. Therefore, the natural molecule may serve several purposes which can be exploited by synthetic chemists interested in preparing interfering analogs.
A structure-function study was performed on the synthetic 21 residue neuropeptide, Lymantria testis ecdysiotropin (LTE), originally isolated from brains of Lymantria dispar pupae. The peptide induces ecdysteroid synthesis by testis sheaths of various lepidopteran species. LTE, as well as synthetic LTE 1-11, 11-21, and 11-15, stimulated significant synthesis in larval and pupal testes of Lymantria dispar at concentrations of 10(-9) to 10(-15M); LTE 16-21 was weakly active, and an elongated LTE, 1-22, was inhibitory to synthesis through all but extremely low concentrations (10(-15M)). Since the sequence and polarity of residues in LTE 1-11, 11-15, and 11-21 are quite different, several parts of the molecule must activate receptors which initiate the cascade resulting in ecdysiogenesis in Lepidopteran testes.