Insect freeze tolerance: Roles of protein phosphatases and protein kinase A.
Freeze-tolerant larvae of the goldenrod gall fly, Eurosta solidaginis Fitch, show multiple metabolic adaptations for subzero survival including the autumn synthesis of high concentrations of polyols. The induction and regulation of cold hardiness adaptations requires the intermediary action of signal transduction enzymes. The present study evaluates changes in the activities of cAMP-dependent protein kinase (PKA), protein phosphatases 1 (PP1), 2A, 2C, and protein tyrosine phosphatases (PTPs) over the course of the winter season and also in insects exposed to -4, -20 degrees C, or anoxic conditions in the laboratory. The increased PKA and decreased PP1 over the winter season and/or at subzero temperature support a regulatory role for these enzymes in cryoprotectant polyol synthesis. PTP activities were also strongly increased under these conditions and may act to antagonize tyrosine kinase mediated cell growth and proliferation responses and, thereby, contribute to hypometabolism and diapause over the winter.
Pfister
Thomas D
TD
Institute of Biochemistry and Department of Chemistry, Carleton University, Ottawa, Canada K1S 5B6.
Storey
Kenneth B
KB
D000222:Adaptation, Physiological; D000818:Animals; D003080:Cold Temperature / Q000009:adverse effects*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004175:Diptera / Q000201:enzymology* / Q000502:physiology*; D005615:Freezing; D018507:Gene Expression Regulation, Developmental; D015971:Gene Expression Regulation, Enzymologic; D000860:Hypoxia; D007814:Larva / Q000201:enzymology / Q000502:physiology; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D012621:Seasons; D013997:Time Factors
D017868:Cyclic AMP-Dependent Protein Kinases; D010749:Phosphoprotein Phosphatases