PARK7

DJ1, also known as Parkinson disease protein 7, is a protein which in humans is encoded by the ''PARK7'' gene. Its weak glyoxalase activity has been verified by many labs, however the reported protein deglycase activity is likely to be an artifact stemming from DJ-1's ability to destroy free methylglyoxal.

Structure

Gene

The gene ''PARK7'', also known as ''DJ-1'', encodes a protein of the peptidase C56 family. The human gene ''PARK7'' has 8 exons and locates at chromosome band 1p36.23.

Protein

The human protein DJ-1 is 20 kDa in size and composed of 189 amino acids with seven β-strands and nine α-helices in total and is present as a dimer. It belongs to the peptidase C56 family of proteins.

The protein structures of human protein DJ-1, ''Escherichia coli'' chaperone Hsp31, YhbO, and YajL and an Archaea protease are evolutionarily conserved.

Function

DJ-1 was shown to prevent metabolite and protein damage caused by a glycolytic metabolite. This metabolite has been suggested and confirmed to be cyclic 3-phosphoglycerate (or cyclic 3-phosphoglyceric anhydride). Catalytic efficiency of DJ-1 as a hydrolase of cyclic 3-phosphoglyceric anhydride is 10,000 times higher than other reported enzymatic activities of DJ-1.

Under an oxidative condition, DJ-1 inhibits the aggregation of α-synuclein via its chaperone activity, thus functioning as a redox-sensitive chaperone and as a sensor for oxidative stress. Accordingly, DJ-1 apparently protects neurons against oxidative stress and cell death. In parallel, protein DJ-1 acts as a positive regulator of androgen receptor-dependent transcription. DJ-1 is expressed in both the neural retina and retinal pigment epithelium of mammals, where it exerts a neuroprotective role against oxidative stress under both physiological and pathological conditions.

Pyrroloquinoline quinone (PQQ) has been shown to reduce the self-oxidation of the DJ-1 protein, an early step in the onset of some forms of Parkinson's disease.

Functional DJ-1 protein has been shown to bind metals and protect against metal-induced cytotoxicity from copper and mercury.

DJ-1/''PARK7'' and its bacterial homologs: Hsp31, YhbO, and YajL can repair methylglyoxal and glyoxal glycated nucleotides. Guanine, either in the form of a free nucleotide or as a nucleotide incorporated into nucleic acid ( DNA or RNA), if glycated, can be repaired by DJ-1/''PARK7''. Deglycase-deficient bacterial mutants with reduced ability to repair glycated bases in DNA show strong mutator phenotypes. A follow up study confirmed that DJ-1 reduces levels of reversible adducts of methylglyoxal with guanine and cysteine in vitro. However, since the steady-state kinetics of DJ-1 acting on reversible hemithioacetal substrates are fitted adequately with a computational kinetic model that requires only a DJ-1 glyoxalase activity, it was concluded that deglycation is an apparent rather than a true activity of DJ-1.

DNA repair

DJ-1 is a DNA damage response protein that is recruited to sites of DNA damage where it participates in the repair of DNA double-strand breaks through the processes of non-homologous end joining and homologous recombination. Evidence for a linkage between DNA damage and Parkinson's disease has been reported for decades. Recently evidence has been presented that defective DNA repair is linked specifically to DJ-1 mutation, and thus DJ-1 mutation likely contributes to Parkinson's disease pathogenesis.

Clinical significance

Defects in this gene are the cause of autosomal recessive early-onset Parkinson's disease 7.

Interactions

''PARK7'' has been shown to interact with:
* CASK,
* EFCAB6, and
* PIAS2.

See also

* Animal models of Parkinson's disease
* Mitochondria associated membranes
* Stress granule

References

Further reading

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External links

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