On the Oligomeric State of DJ-1 Protein and Its Mutants Associated with Parkinson Disease

Abstract

Mutations in the DJ-1 protein are present in patients suffering from familial Parkinson disease. Here we use computational methods and biological assays to investigate the relationship between DJ-1 missense mutations and the protein oligomeric state. Molecular dynamics calculations suggest that: (i) the structure of DJ-1 wild type (WT) in aqueous solution, in both oxidized and reduced forms, is similar to the crystal structure of the reduced form; (ii) the Parkinson disease-causing M26I variant is structurally similar to the WT, consistent with the experimental evidence showing the protein is a dimer as WT; (iii) R98Q is structurally similar to the WT, consistent with the fact that this is a physiological variant; and (iv) the L166P monomer rapidly evolves toward a conformation significantly different from WT, suggesting a change in its ability to oligomerize. Our combined computational and experimental approach is next used to identify a mutant (R28A) that, in contrast to L166P, destabilizes the dimer subunit-subunit interface without significantly changing secondary structure elements. Parkinson disease (PD)5 is the second most common progressive neurodegenerative disorder, affecting 1-2% of all individuals above the age of 65 (1-12). PD is characterized by muscle rigidity, resting tremor, bradykinesia, and gait disturbance with dysequilibrium. The neuropathological hallmark in post mortem brains is the selective degeneration of specific subsets of mesencephalic dopaminergic cells and the formation of cytoplasmic aggregates called Lewy bodies.

Structural Impact of Three Parkinsonism-Associated Missense Mutations on Human DJ-1,

“…Analysis of the crystal structure suggests that the modest thermal destabilization of M26I DJ-1 observed in DSC is due to minor core packing defects created by the branched side chain of I26 and the loss of favorable packing contacts with the C and Sδ atoms of M26. These results are in broad agreement with previous molecular dynamics simulations that showed no major structural changes in response to the M26I missense mutation (61).…”

Parkinson Disease-associated DJ-1 Is Required for the Expression of the Glial Cell Line-derived Neurotrophic Factor Receptor RET in Human Neuroblastoma Cells

“…To this purpose we transfected the PD-associated L166P mutant into siDJ-1#1 cells. L166P protein levels were lower than wt DJ-1, as expected (32). Interestingly, L166P mutant was not able to rescue RET expression as assayed by Western blot (Fig.…”

Aggresome-forming TTRAP mediates pro-apoptotic properties of Parkinson's disease-associated DJ-1 missense mutations

“…Furthermore, recent computational and biochemical studies have shown that M26I dimerizes. 18 Therefore, a common pathological mechanism shared by all mutants is still lacking. Most importantly, as most of the experiments have been performed on the highly unstable L166P protein, more studies are needed on dimer-forming, more stable DJ-1 mutants such as M26I.…”

“…Expression vectors encoding for WT, M26I and L166P DJ-1 were described earlier. 18 Two different oligonucleotide sequences were selected for the knockdown TTRAP expression using siRNA Target Finder software (Invitrogen). The hairpin-encoding oligonucleotides were cloned into the pSuperior vector (Invitrogen).…”

“…On the contrary, L166P is very unstable and its expression level lower than WT. [18][19][20][21] Together with a loss of function, DJ-1 missense mutations may be involved in pathological protein-protein interactions that may lead to a 'gain-of-function' behavior. The search for common protein partners that distinguish mutant DJ-1s from WT has been so far limited, with the important exception of an increased binding to parkin shared by M26I and L166P.…”