Date of Award

January 2016

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Medicinal Chemistry and Molecular Pharmacology

First Advisor

Tony R Hazbun

Committee Member 1

Jean-Christophe Rochet

Committee Member 2

Douglas J LaCount

Committee Member 3

Ruben C Aguilar

Abstract

Among different type of protein aggregation, amyloids are biochemically well characterized state of protein aggregation that is commonly associated with a large number of neurodegenerative diseases in mammals and cause heritable traits in Saccharomyces cerevisiae. Among many other neurodegenerative diseases linked with amyloids, Parkinson’s disease is the second most common disorder that is caused by progressive deterioration of dopaminergic neurons in substantia nigra. Cellular stresses such as accumulation of high level of reactive oxygen species, mitochondrial dysfunction and α-syn aggregation lead to toxicity and neuronal cell death in Parkinson’s disease patients. Mutations in certain genes are also involved in the development of a familial form of PD including PARK7 that encodes DJ-1. DJ-1 is a member of ThiJ/DJ-1/PfpI protein superfamily that are the quintessential multitasking or moonlighting protein family as evidenced by their involvement in multiple cellular functions including oxidative stress sensing, protein folding, proteasome degradation, mitochondrial complex stabilization, methylglyoxalase and deglycation enzyme activities. The members of the ThiJ/DJ-1/Pfp1 superfamily appear to have evolved to numerous mechanisms to manage cellular stress. The protein superfamily members are present across the evolutionary spectrum including prokaryotes and the budding yeast, S. cerevisiae, that has four paralogs Hsp31, Hsp32, Hsp33, and Hsp34. Hsp31 consists of 237 amino acids with a MW of 25.5 kDa and forms a homodimer in solution. It possesses the Cys-His-Glu catalytic triad common to ThiJ/DJ-1/PfpI superfamily proteins. Previously, we have shown that Hsp31 possesses chaperone properties with protective effects against α-syn toxicity in yeast. Recently, it is shown that Hsp31 has a methylglyoxalase activity that converts the toxic metabolite methylglyoxal into lactate. Here, we confirmed that Hsp31 is a robust methylglyoxalse that is more potent in activity than its human homolog DJ-1. We demonstrated that Hsp31 chaperone activity to protect the cells from α-syn toxicity is not under the influence of its enzymatic activity or autophagy pathway. Moreover, we confirmed that Hsp31 expression is induced by H2O2 mediated oxidative stress and further showed an increased expression of Hsp31 under α-syn mediated proteotoxic stress. These results establish that Hsp31 molecular chaperone activity is self-sufficient to protect the cells from stress conditions without requiring its enzymatic activities.

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