Quantifying Changes in Heat Shock Protein Expression in a Drosophila Model of Neuronal Tauopathy
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Aggregation of misfolded, hyperphosphorylated tau protein is a hallmark of several etiologically diverse age-related neurodegenerative diseases called tauopathies, which include Picks’ disease, Alzheimer’s disease, and chronic traumatic encephalopathy. Tau aggregation is linked to the progressive loss of neurons and associated disturbances in cognition, memory, movement, and behavior. Proper protein folding is regulated by heat shock proteins (HSPs), and their role in tau aggregation has been extensively investigated. It has not been determined, however, whether tau in turn can change the expression of HSPs. We measured changes in HSP transcription in Drosophila expressing or lacking human tau in their neurons, after exposure to heat for up to 6 hours. The mRNA levels of heat inducible Hsp70-A and Hsp83 were elevated after 30 minutes to an hour of heat exposure, and this effect was significantly suppressed in the presence of tau. The mRNA levels of constitutively transcribed Hsc70-4 and Hsp60 were comparable across genotypes and heat exposure times. These results indicate that tau in neurons can selectively inhibit the upregulation of inducible HSPs in response to thermal stress. Further development of this line of research should provide insight into the mechanisms underlying tau aggregation in disease and contribute to the development of improved therapies.