Effect of heat stress on client protein AChE expression in a molluscan model, G. demissa

Cox, Rachel L.

We studied acetylcholinesterase as a client protein of Hsp70 in response to heat. Hsp70 is a chaperone protein that accumulates under stressful conditions in order to prevent or reverse the denaturation of other proteins, like acetylcholinesterase. Because of this, it is often used as a biomarker for stress. Acetylcholinesterase (AChE) is an enzyme that breaks down the neurotransmitter acetylcholine present in neuronal synapses. Quantification of AChE expression and activity is also often used to indicate environmental stress, such as pesticide exposure, in aquatic organisms. Using the Atlantic ribbed mussel (Geukensia demissa) as a model, we studied AChE expression in response to heat shock in two differently impacted salt marsh estuaries: the Bronx River (Bronx, NY), a site that has suffered years of environmental stress, and Greenwich Cove (Greenwich Cove, CT), a comparatively clean site. Previous data from our lab has shown elevated constitutive HSP70 expression in Bronx River mussels, indicating that the mussels are under constant stress in their natural environment.The idea that AChE responds to heat shock is essentially unexplored in any in vivo models and previous work from our lab suggests a relationship between heat stress and AChE activity. The specific goals of this study were two-fold. First, we measured the baseline expression of AChE from both sites to gain insight on the health status of the mussels living in their natural environments. Second, we examined the heat shock response timeline in order to understand how Hsp70 may regulate AChE expression. We did this by comparing AChE and Hsp70 expression levels in response to heat stress allowing different recovery times post heat shock. Analysis of our results suggests a significantly more efficient heat shock response in Bronx River mussels when compared to Greenwich Cove mussels. This research suggests that the Bronx River’s environmental stresses enhance this population of mussels’ stress response and speaks to the changed biological functioning of stressed organisms.