Differential increase in AMPK and HSP70 mRNA expression with temperature in the rock crab, Cancer irroratus

Abstract

5′ AMP activated protein kinase (AMPK) has been described in mammals as a “metabolic master switch” that regulates cellular [ATP]. Little is known about AMPK in invertebrates and the effect of temperature on AMPK expression. We tested the hypothesis that temperature stress increases AMPK mRNA levels in a decapod crustacean, and compared this increase to the temperature effect on HSP70 expression. Rock crabs, Cancer irroratus, were incubated for two days at 11, 24 or 27°C before sampling tissue from heart, hepatopancreas and claw muscle. RNA was extracted and reverse transcribed into cDNA. Quantitative PCR measured relative mRNA expression levels for AMPK and HSP70. Temperature had no effect on AMPK mRNA expression in hepatopancreas and heart but expression was 7.2 fold higher in the heart at all temperatures. AMPK expression in the claw muscle at 11°C was similar to the heart, but increased significantly 3.1 fold at 24°C. An insignificant 1.7 fold increase was observed at 27°C. HSP70 expression remained low in all three tissues at 11 and 24°C but increased significantly at 27°C (4.6, 6.6 and 14.5 fold, heart, hepatopancreas, claw muscle, respectively). Previous studies showed that high temperature leads to cellular ATP depletion. In the claw muscle increased AMPK expression at 24°C might prevent earlier ATP depletion even before the heat shock response starts in the form of HSP70 expression. Further experiments will elucidate the time course of these events in more detail. Supported by a New Investigator Award from MDIBL and a Research Career Enhancement Award from APS to M.F. and an INBRE fellowship to M.O.