Objective/Rationale:
The goal of our project is to develop an approach to treat PD by stabilizing wild-type dimeric DJ-1 with a small molecule. We hypothesize that this approach will lead to an elevated level of DJ-1 in vivo under PD disease conditions. Small molecule binding could directly interfere with DJ-1 superfluous oxidation by preventing over-oxidation of Cys106 of DJ-1, as proposed by Ariga and co-workers (J Neurochem 2008, 10, 1471). Alternatively, a small molecule could also mitigate the harmful effects of superfluous oxidation via thermodynamic stabilization of the DJ-1 homodimer when several of its Cys and Met amino acid are already over-oxidized (Rochet and co-workers; Biochemistry 2007, 46, 5776). Our approach enables the discovery of small molecules with either or both mechanisms of action and therefore offers a novel way forward to develop a disease modifying therapeutic for PD.
Project Description:
Recently, we carried out a unique biophysics-based, high-throughput screen to identify novel scaffolds of small-molecule binders to native DJ-1. This grant will enable us to (1) determine the affinity of hit compounds to DJ-1, (2) asses their ability to stabilize native and/or oxidized DJ-1 dimer, and (3) to prevent DJ-1 dimer oxidation and de-stabilization via binding to the protein. Furthermore, selected small-molecule DJ-1 stabilizers will be test for their ability to rescue dopaminergic neurons from rotenone- (oxidative) and alpha-synuclein-mediated toxicity.
Relevance to Diagnosis/Treatment of Parkinson’s Disease:
Homozygous mutations in the DJ-1 gene have been linked to early-onset of PD. Under oxidizing conditions, DJ-1 can undergo superfluous oxidation of several Cys and Met residues, which may lead to DJ-1 inactivity as a result of structural destabilization. The downregulation of endogenous DJ-1 sensitizes neurons to cell death induced by oxidative insults, whereas elevated levels of wild-type, but not mutant, DJ-1 protect neurons from oxidative stress and other PD related insults. DJ-1 knockout pre-clinical models show nigrostriatal dopaminergic deficits and are hypersensitive to the toxic effects of MPTP. Our drug discovery approach to DJ-1 is designed for to the discovery of small molecules, which could result an elevated level of DJ-1 in vivo under PD conditions.
Anticipated Outcome:
Our proposed studies can (1) result in the discovery of functional small molecule ligands of DJ-1; (2) enable us to select different chemical scaffolds targeting DJ-1 with elucidated mechanism of action for hit/lead optimization; and (3) provide small-molecule probes to explore DJ-1 function and loss of function as related to PD in different in vivo models.