AMP-activated protein kinase (AMPK) in the rock crab,Cancer irroratus: an early indicator of temperature stress

Abstract

SUMMARYExposure of marine invertebrates to high temperatures leads to a switch from aerobic to anaerobic metabolism, a drop in the cellular ATP concentration ([ATP]), and subsequent death. In mammals, AMP-activated protein kinase (AMPK) is a major regulator of cellular [ATP] and activates ATP-producing pathways, while inhibiting ATP-consuming pathways. We hypothesized that temperature stress in marine invertebrates activates AMPK to provide adequate concentrations of ATP at increased but sublethal temperatures and that AMPK consequently can serve as a stress indicator (similar to heat shock proteins, HSPs). We tested these hypotheses through two experiments with the rock crab, Cancer irroratus. First, crabs were exposed to a progressive temperature increase (6°C h -1 ) from 12 to 30°C. AMPK activity, total AMPK protein and HSP70 levels, reaction time, heart rate and lactate accumulation were measured in hearts at 2°C increments. AMPK activity remained constant between 12 and 18°C, but increased up to 9.1(±1.5)-fold between 18 and 30°C. The crabsʼ reaction time also decreased above 18°C. By contrast, HSP70 (total and inducible) and total AMPK protein expression levels did not vary significantly over this temperature range. Second, crabs were exposed for up to 6 h to the sublethal temperature of 26°C. This prolonged exposure led to a constant elevation of AMPK activity and levels of HSP70 mRNA. AMPK mRNA continuously increased, indicating an additional response in gene expression. We conclude that AMPK is an earlier indicator of temperature stress in rock crabs than HSP70, especially during the initial response to high temperatures. We discuss the temperature-dependent increase in AMPK activity in the context of Shelfordʼs law of tolerance. Specifically, we describe AMPK activity as a cellular marker that indicates a thermal threshold, called the pejus temperature, T p . At T p the animals leave their optimum range and enter a temperature range with a limited aerobic scope for exercise. This T p is reached periodically during annual temperature fluctuations and has higher biological significance than earlier described critical temperatures, at which the animals switch to anaerobic metabolism and HSP expression is induced.

Effects of heat stress on serum insulin, adipokines, AMP-activated protein kinase, and heat shock signal molecules in dairy cows

“…The first treatments shown to activate AMPK were pathologic stresses such as heat stress (Corton et al, 1994). Heat stress has been shown to affect AMPK activity in the rock crab, AMPK activity increased by up to 9.1-fold from 18 to 30 °C (Frederich et al, 2009). Liu and Brooks (2012) found that 1 h mild heat stress in C2C12 myotubes upregulated AMPK activity.…”

“…AMP-activated protein kinase (AMPK) functions as a "fuel gauge" to monitor cellular energy status (Hardie et al, 2003). A variety of stresses are known to activate AMPK in mammals (Frederich et al, 2009). However, the relationship between heat stress and serum AMPK activity of dairy cows is still unclear.…”

Energy metabolism and metabolic depression during exercise inCallinectes sapidus, the Atlantic blue crab: effects of the bacterial pathogenVibrio campbellii

“…AMPK has recently been identified as a central mediator of the translational control of protein synthesis during hypoxic stress in rat hepatocytes (Horman et al, 2002;Kemp et al, 2002). It has now been confirmed that AMPK is present in crustaceans and is activated in response to both temperature and hypoxic stress (Pinz et al, 2005;Frederich et al, 2009). Therefore, AMPK, if present in the blue crab, may be playing a role in regulating energy metabolism during bacterial stress.…”

Metabolic energy sensors (AMPK and SIRT1), protein carbonylation, and cardiac failure as biomarkers of thermal stress in an intertidal limpet: linking energetic allocation with environmental temperature during aerial emersion

“…AMP-activated protein kinase (AMPK), a metabolic sensor of the AMP/ATP ratio (Hardie and Sakamoto, 2006), has proven to be a good cellular indicator of the transition into the pejus temperature range during heat stress in intertidal crabs (Frederich et al, 2009). The histone/protein deacetylase SIRT1 is a fuel-sensing molecule that has coexisted with AMPK in cells throughout evolution (Ruderman et al, 2010).…”