Hsp70 expression patterns in two populations of Geukensia demissa

Waterways in industrial areas are often repositories for sewage water and environmental toxins.  Effects of these contaminants on aquatic life can be measured through various biomarkers, such as heat shock protein 70 (Hsp70), a cellular protein that accumulates under stressful conditions in order to prevent or reverse protein denaturation.  Hsp70 serves as a bio-indicator for the existence and degree of stress an organism endures at any given moment.   We collected G. demissa mussels from two sites: the urbanly impacted Bronx River, New York and the relatively less industrially impacted Greenwich Cove, Connecticut, and compared constitutive and heat-induced expression of Hsp70 in these two populations.  Hsp70 expression was determined by Western Blot analysis.  Bronx River and Greenwich Cove mussels demonstrate a significant rise in Hsp70 expression after undergoing heat-shock, suggesting a heat-shock response.  In addition, our results, corroborated with data over three years, show that constitutive expression of Hsp70 in Bronx River mussels is higher than that of Greenwich Cove mussels.  We also conducted a time-course experiment in order to observe inducible Hsp70 expression over time in both populations.  At 2.5 hours following heat-shock, Hsp70 expression increase by 13.505%,Greenwich Cove mussels had their while the Bronx River mussels had their HSP70 expression increase by 18.91%.  27 hours after equilibration, heat-shock increased Greenwich Cove mussel’s Hsp70 expression by 22.31%, and 5.33% for the Bronx River mussels.  These results suggest that Bronx River mussels respond more quickly to heat stress. This implies that mussels under constant exposure to stress are able to launch a more rapid stress response.  Oppositely, because Greenwich Cove mussels live in a relatively clean and environmentally undisturbed site, these mussels may be slower to launch an Hsp70 response to the heat-shock.  In addition, it would take longer for these mussels to re-adjust their Hsp70 levels back to their "natural" levels.  Results from these comparative analyses offer important insights into the cellular basis of stress response and provide valuable information regarding environmentally impacted organisms and their response to increased environmental demands.