Deacetylation Of Metabolic Enzymes Regulates Pupal Diapause In The Cotton Bollworm,Helicoverpa Armigera

Most insect species have evolved a special stage of developmental arrest(diapause)in response to adverse environmental conditions.Diapause,a specific entomological term,is used to describe the slow development as dauer in Caenorhabditis elegans and lifespan extension in Drosophila melanogaster with low metabolic activity.It has been well demonstrated that neuropeptides and hormone are key factors to regulate diapause.Helicoverpa armigera pupal diapause is induced by reduction of prothoracicotropic hormone(PTTH)and steroid hormone ecdysone.Changes of physiology and biochemistry on diapause have been well studied,and metabolic depression is a universal aspect of diapause among many species.However,molecular mechanisms for low metabolic activity are unclear.Pyruvate is a key intermediate in glycolysis and can be made from glucose.Pyruvate is then converted into acetyl-coenzyme A,which is the main input for a series of reactions,known as the tricarboxylic acid(TCA)cycle,to provide energy.Pyruvate production is primarily regulated by pyruvate kinase(PK),and two other enzymes phosphoenolpyruvate carboxykinase(PEPCK),and phosphoglycerate mutase(PGAM)are closely correlated with pyruvate production.In this study,low levels of pyruvate at natural physiological state profoundly extend lifespan by reducing TCA cycle activity in H.armigera.We revealed a novel connection between enzyme acetylation and lifespan extension in a Sirt2-dependent manner that protein acetylation has positive effect on lifespan extension by inhibiting glucose metabolism.In diapause pupae,the lifespan is extended by down-regulation of Sirt2 and leading to metabolic enzyme acetylation,which inhibits pyruvate generation and TCA cycle activity.This is the first report showing that both physiological levels of pyruvate and down-regulation of Sirt2 contribute to lifespan extension in insects.Insulin signaling pathway controls development timing through regulation of energy metabolism.Although insulin titers in blood of diapause-destined pupae were higher than in that of diapause pupae,high levels of p-Akt were presented in pupal brain.PP2 A is a ubiquitous phosphor-serine/threonine phosphatase that regulates a variety of enssential cellular events.Here we find that PP2A-B',a regulatory subunit of PP2 A,is lowly expressed in diapause-destined pupal brain.We showed that PP2A-B' and Akt physically bind to each other.Overexpression of PP2A-B' significantly decreased p-Akt levels and inhibition of PP2 A remarkably increased p-Akt levels,suggesting that high levels of PP2A-B' in nondiapause pupae dephosphorylate Akt,while low levels of PP2A-B' result in increased p-Akt levels.Finally,we investigated the role of p-Akt in pupal brain and speculated that p-Akt may regulate Glut expression to control glucose absorption.To test this hypothesis,AI4 treatment was applied and reduction in p-Akt and Glut levels were observed.Furthermore,DOG treatment and injection increased p-Akt and Glut levels.In conclusion,high levels of p-Akt in diapause-destined pupal brain may enhance Glut expression to absorb glucose as energy storage.