Allatotropin‐Induced formation of inositol phosphates in the corpora allata of the moth, Manduca sexta

Abstract

Allatotropin (AT) is a 13 amino acid neuropeptide isolated from the tobacco hornworm, Manduca sexta, which stimulates the biosynthesis of juvenile hormone (JH) in adult females of this insect. In this paper we report that AT stimulates inositol phosphate formation in both female and male corpora allata (CA) of adult Manduca sexta. Furthermore, thapsigargin, a potent Ca2+-ATPase inhibitor, staurosporine, a potent inhibitor of protein kinases A and C, and 2,5-di-(tert-butyl)-7,4-hydroquinone (DBHQ), a potent inhibitor of liver microsoma1 ATP-dependent Ca" sequestration, all stimulate JH biosynthesis without changing the basal level of inositol phosphates. These data suggest that AT activates an inositol 1,4,5-trisphosphate (IP3) pathway. Furthermore, increases in the free intracellular Ca" concentration in the CA stimulate JH biosynthesis. 61992wiley-Liss, Inc.Key words: thapsigargin, 2,5-di-(tert-butyl)-1,4-hydroquinone, staurosporin, allatotropin, inositol trisphosphate INTRODUCTIONThe JHs' are involved in many aspects of the insect life cycle including control of metamorphosis, adult sexual maturation, and reproduction [1,2]. These hormones are synthesized in and secreted by the CA, a pair of endocrine glands located posterior to the brain of the insect. There have been reports of factors Acknowledgments: We thank Dr. Jorge Li and L. Sumrnerfelt for supplying allatotropin, Dr. Fred C. Baker for helpful discussions, and Anne Toschi for demonstrating the dissection of corpora cardiacdcorpora allata complexes from Manduca sexta.

Molecular Characterization and Expression Analysis ofManduca sextaAllatotropin

“…The intracellular mechanisms involved in JH synthesis in the M. sexta CA are stimulated by cyclic AMP (Granger et al, 1994) and are influenced by the levels of cytosolic free calcium (Allen et al, 1992). Mas AT has been shown to induce the formation of inositol 1,4,5-trisphosphate in M. sexta CA resulting in an increase in intracellular calcium levels which in turn, causes an increase in JH synthesis (Reagan et al, 1992). The C-terminal region of the 3' exon common to all Mas AT mRNAs predicts a motif similar to the EFhand family of calcium-binding motifs.…”

Isolation and functional characterization of an allatotropin receptor from Manduca sexta

“…In adult M. sexta, stimulation of JH biosynthesis is accompanied by increased levels of inositol phosphates (Reagan et al, 1992). In another lepidopteran insect, Heliothis virescens, a calcium ionophore mimics the effect of Manse-AT and a Ca 2þ chelator antagonized the stimulatory effects of Manse-AT, suggesting that the peptide affects JH biosynthesis by increasing intracellular Ca 2þ concentrations (Rachinsky et al, 2003).…”

Allatotropic activity in the suboesophageal ganglia and corpora cardiaca of the adult male loreyi leafworm, Mythimna loreyi

“…In M. sexta, the allatotropin stimulates JH biosynthesis by way of an increase in IP 3 , which in turn leads to an increase in free intracellular Ca 2+ (Reagan et al, 1992). In M. sexta, the allatotropin stimulates JH biosynthesis by way of an increase in IP 3 , which in turn leads to an increase in free intracellular Ca 2+ (Reagan et al, 1992).…”