Functional characterization of caenorhabditis elegans DJR-1.1 and DJR-1.2, homologs of human DJ-1 associated with Parkinson’s disease

Abstract

Alpha-oxoaldehydes such as methylglyoxal (MGO) and glyoxal (GO) are highly reactive as to modify cellular macromolecules, causing cell death. The major system known to detoxify such compounds includes glyoxalase I and II that requires glutathione (GSH) as a co-factor. Here we characterized two homologs of human DJ-1, a protein associated with Parkinson’s disease, in C.elegans as novel glyoxalases. The two homologs, each named DJR-1.1 and DJR-1.2, share high structural similarity with human DJ-1 and have superimposable catalytic residues for its enzymatic activity. Purified DJR-1.1 and DJR-1.2 proteins showed activities against both methylglyoxal and glyoxal, yielding lactic acid and glycolic acid as products, respectively. Activities of worm extracts from wild type and knockout DJR mutant C. elegans also showed that both DJR-1.1 and DJR-1.2 exert glyoxalase activities in tissue extracts. Endogenous glyoxal levels of DJR mutants were significantly higher than that of wild type worms under normal conditions, and aging of these mutants lead to higher levels of glyoxal-induced Nε-carboxymethyl lysine (CML), one of the deleterious advanced glycation end products (AGEs) caused by glyoxal. DJR-1.1 was expressed throughout the intestine of worms, locating in both nucleus and cytoplasm, while DJR-1.2 was expressed in the cytoplasm of various chemosensory neurons and glial cells. The expression of DJR-1.2 was dramatically increased when worms were starved and entered the dauer stage, which was correlated with an increase in its enzymatic activity. The dauer-specific expression of DJR-1.2 depends on DAF-16 transcription regulator, a homologue of mammalian FOXO. The C.elegans mutants of DJR-1.1 and DJR-1.2 exhibited varying degrees of sensitivities to glyoxal and methylglyoxal, which were rescued by corresponding transgenics, although normal life spans of these mutants were essentially unchanged. Mutants of DJR-1.2 also lead to a significant loss of dopaminergic neurons c...