p53‐dependent neuronal cell death in a DJ‐1‐deficient zebrafish model of Parkinson's disease

Abstract

Mutations in DJ-1 lead to early onset Parkinson's disease (PD). The aim of this study was to elucidate further the underlying mechanisms leading to neuronal cell death in DJ-1 deficiency in vivo and determine whether the observed cell loss could be prevented pharmacologically. Inactivation of DJ-1 in zebrafish, Danio rerio, resulted in loss of dopaminergic neurons after exposure to hydrogen peroxide and the proteasome inhibitor MG132. DJ-1 knockdown by itself already resulted in increased p53 and Bax expression levels prior to toxin exposure without marked neuronal cell death, suggesting subthreshold activation of cell death pathways in DJ-1 deficiency. Proteasome inhibition led to a further increase of p53 and Bax expression with widespread neuronal cell death.Pharmacological p53 inhibition either before or during MG132 exposure in vivo prevented dopaminergic neuronal cell death in both cases. Simultaneous knockdown of DJ-1 and the negative p53 regulator mdm2 led to dopaminergic neuronal cell death even without toxin exposure, further implicating involvement of p53 in DJ-1 deficiency-mediated neuronal cell loss. Our study demonstrates the utility of zebrafish as a new animal model to study PD gene defects and suggests that modulation of downstream mechanisms, such as p53 inhibition, may be of therapeutic benefit.

DJ-1 inhibits TRAIL-induced apoptosis by blocking pro-caspase-8 recruitment to FADD

“…This suggests that DJ-1 does not function downstream of caspase-8 activation or its effector caspases and their substrates. It has been reported that DJ-1 inhibits apoptosis by regulating different transcription factors to modulate gene expression (Clements et al, 2006;Bretaud et al, 2007;Fan et al, 2008a;Vasseur et al, 2009;Foti et al, 2010). However, we observed that DJ-1 did not affect DR mRNA or protein levels in H1299 cells (Figure 3).…”

“…To explore the role of DJ-1 in the TRAIL-induced apoptosis pathway, we performed DJ-1 knockdown experiments. Because DJ-1 is involved in regulating p53 activity (Bretaud et al, 2007;Fan et al, 2008a, b;Giaime et al, 2010), we performed experiments using both p53 þ / þ and p53À/À human colon cancer cells (HCT116) to determine whether p53 is involved in the DJ-1-regulated TRAIL pathway. Smallinterfering RNA against DJ-1 (siDJ-1) caused a reduction of approximately 70% of endogenous DJ-1 compared with transfections using a negative control small-interfering RNA (siNC; Figure 1a).…”

“…The levels of TRAIL receptors, including death receptors and decoy receptors, are closely related to apoptosis induced by TRAIL. Because DJ-1 can function in the nucleus to regulate transcription (Clements et al, 2006;Bretaud et al, 2007;Fan et al, 2008a;Foti et al, 2010), it is possible that DJ-1 regulates the TRAIL signaling pathway by influencing the expression of TRAIL receptors at the transcriptional level. We transfected H1299 cells with siNC or siDJ-1 and examined the mRNA levels of the four TRAIL receptors using reverse transcriptase-PCR.…”

“…It contributes to cell survival by interacting with p54nrb to inhibit the silencing activity of pyrimidine tract-binding protein-associated splicing factor (Xu et al, 2005) or by regulating androgen receptor transcriptional activity (Takahashi et al, 2001;Niki et al, 2003;Tillman et al, 2007). Recently, DJ-1 was found to repress p53 (Bretaud et al, 2007;Fan et al, 2008a, b;Giaime et al, 2010).…”

Proteomic identification of p53-dependent protein phosphorylation

“…In a recent report, knockdown of DJ-1 in zebrafish model of Parkinson's disease resulted in increased expression of p53 and Bax, suggesting that absence of DJ-1 activates the death pathway (Bretaud et al, 2007). Our finding that DJ-1 is phosphorylated upon activation of p53 raises the possibility that p53-dependent phosphorylation of DJ-1 inhibits its function and thus facilitates apoptosis.…”