Eukaryotic cells have adopted several tactics to cope with a battery of stresses for their survival. One way is topause the translation of most mRNAs to conserve their energy and to reduce the accumulation of damagedproteins. Such changes are mediated by the phosphorylation of eukaryotic translation initiation factor-2α (eIF-2α) on serine 51, and subsequent gathering of non-translating mRNAs and RNA binding proteins into discretecytoplasmic foci, called stress granules (SGs). SGs are stalled translational complexes that function to protectcells under stress. Dysregulation of eIF-2α phosphorylation and SG formation plays an important role in thepathogenesis of several neurodegenerative disorders. DJ-1 is a small and multi-functional oxidative stressresponse protein. As loss-of-function mutations in DJ-1 are linked to recessively inherited Parkinson's disease(PD), investigation of DJ-1’s function and the pathways in which DJ-1 is involved has been an active field ofresearch. Diverse functions including chaperone, cysteine protease, transcriptional coactivator andtransnitrosylase are suggested, but its role(s) in contributing to the pathogenesis of PD remains to be fullyelucidated. Here, we propose to investigate a hitherto unexplored function of DJ-1, and elucidate the link of thisfunction to neuronal survival. Our preliminary data show that silencing DJ-1 expression in neuronal cells leadsto decreased phosphorylation of eIF-2α, subsequently impairs SG formation and fails to inhibit global proteinsynthesis in response to sodium arsenite. Among reactive oxygen species produced by arsenite challenge, weshowed that intracellular nitric oxide (NO) is responsible for stimulating eIF-2α phosphorylation. NO is ofparticular interest as it is involved in the pathogenic processes resulting in dopaminergic neuronal death in PD.Therefore, we hypothesize that DJ-1 represses protein translation in response to NO by activating the eIF-2αpathway and subsequent SG formation. Loss-of-function mutations in the DJ-1 gene impair the eIF-2αpathway and compromise this cell survival response, and thereby contributes to PD pathogenesis. Further,characterizing this pathway in its molecular and cellular detail will lead to important insights into the pathogenicmechanism of sporadic PD as well. To test our hypothesis, we propose two specific aims. First, we willinvestigate the functional consequences and mechanism of DJ-1 on the activation of eIF-α pathway inresponse to NO. Second, we will investigate the molecular pathway of eIF-2α in a mouse model of PD.Successful completion of the proposed studies will further advance the knowledge about DJ-1’s biology anddefine the molecular mechanism by which DJ-1 regulates eIF-2α pathway and SG formation. Identifiedpathway and a molecular target of DJ-1 might be exploited as novel therapeutic targets for the treatment of PD.
|Effective start/end date||8/1/16 → 7/31/18|
- National Institutes of Health (NIH)
Eukaryotic Initiation Factor-2
Eukaryotic Initiation Factors