title: AMP-activated protein kinase and metabolic regulation in cold-hardy insects.
abstract: Winter survival for many insects depends on cold hardiness adaptations as well as entry into a hypometabolic diapause state that minimizes energy expenditure. We investigated whether AMP-activated protein kinase (AMPK) could be involved in this adaptation in larvae of two cold-hardy insects, Eurosta solidaginis that is freeze tolerant and Epiblema scudderiana that uses a freeze avoidance strategy. AMPK activity was almost 2-fold higher in winter larvae (February) compared with animals collected in September. Immunoblotting revealed that phosphorylation of AMPK in the activation loop and phosphorylation of acetyl-CoA carboxylase (ACC), a key target of AMPK, were higher in Epiblema during midwinter whereas no seasonal change was seen in Eurosta. Immunoblotting also revealed a significant increase in ribosomal protein S6 phosphorylation in overwintering Epiblema larvae, and in both Eurosta and Epiblema, phosphorylation of eukaryotic initiation factor 4E-binding protein-1 dramatically increased in the winter. Pyruvate dehydrogenase (PDH) E1α subunit site 1 phosphorylation was 2-fold higher in extracts of Eurosta larvae collected in February versus September while PDH activity decreased by about 50% in Eurosta and 80% in February Eurosta larvae compared with animals collected in September. Glycogen phosphorylase phosphorylation was 3-fold higher in Epiblema larvae collected in February compared with September and also in these animals, triglyceride lipase activity increased by 70% during winter. Overall, our study suggests a re-sculpting of metabolism during insect diapause, which shifted to a more catabolic poise in freeze-avoiding overwintering Epiblema larvae, possibly involving AMPK.
authors.affiliation: Université Catholique de Louvain and de Duve Institute, Avenue Hippocrate 75, B-1200 Brussels, Belgium. mark.rider@uclouvain.be
authors.forename: Mark H
authors.initials: MH
authors.lastname: Rider
authors.forename: Nusrat
authors.initials: N
authors.lastname: Hussain
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Dilworth
authors.forename: Janet M
authors.initials: JM
authors.lastname: Storey
authors.forename: Kenneth B
authors.initials: KB
authors.lastname: Storey
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism*; D000064:Acclimatization; D000103:Acetyl-CoA Carboxylase / Q000378:metabolism; D000818:Animals; D003080:Cold Temperature; D024981:Glycogen Phosphorylase / Q000378:metabolism; D019476:Insect Proteins / Q000378:metabolism; D008049:Lipase / Q000378:metabolism; D009036:Moths / Q000201:enzymology*; D010766:Phosphorylation; D030481:Pyruvate Dehydrogenase (Lipoamide) / Q000378:metabolism; D019893:Ribosomal Protein S6 Kinases / Q000378:metabolism; D033621:Tephritidae / Q000201:enzymology*
chemical_list: D019476:Insect Proteins; D030481:Pyruvate Dehydrogenase (Lipoamide); C065640:pyruvate dehydrogenase E1alpha subunit; D024981:Glycogen Phosphorylase; D019893:Ribosomal Protein S6 Kinases; D055372:AMP-Activated Protein Kinases; D008049:Lipase; D000103:Acetyl-CoA Carboxylase