Abstract
Purpose: :
DJ-1 was first discovered as a novel oncogene product that transforms mouse NIH3T3 cells in cooperation with activated ras and was later identified as a causative gene of familial Parkinson’s disease. DJ-1 is a multifunctional protein involved in pathways that regulate cell survival, mitochondrial function, modulation of the PTEN/Akt survival pathway, suppression of Ask1-mediated apoptosis, increased synthesis of glutathione, expression of Hsp70, tyrosine hydroxylase and antioxidative stress. DJ-1 is highly expressed in the testis and moderately in other tissues. DJ-1 peptides were detected in rat retinal pigment epithelium (RPE) cell fractions subjected to proteomic analysis. The present study was conducted to further analyze the localization and function of DJ-1 in mouse retinal tissues and RPE cells.
Methods: :
Paraffin sections of mouse retinas were processed for immunofluorescence with the DJ-1 specific antibodies followed by analysis with confocal microscopy. The presence of DJ-1 was analyzed in whole cell lysates from retina, RPE, and several RPE cell lines. To decipher the DJ-1function, RPE cultures were treated with H2O2 (100 to 800µM) and 4-HNE (5 to 100µM) for various times followed by biochemical and immunohistological analysis.
Results: :
DJ-1 immunoreactivity is associated with cells in the ganglion cell layer, cells in the inner nuclear layer, photoreceptors and RPE. Interestingly, DJ-1 was frequently distributed around the three to five outermost rows of photoreceptor nuclei. In RPE cells under baseline conditions, DJ-1 displays a diffuse cytoplasmic and nuclear staining of all the RPE cell lines analyzed. A major band of ~ 25ΚDa was was observed in the extracts of mouse retina and RPE and in all the RPE cell lines as compared to extracts from mouse brain. RPE cells exposed to oxidative stress lead to a significant increase in DJ-1 expression as analyzed by immunocytochemical and biochemical assays. Moreover, upon oxidative injury, a large portion of DJ-1 redistributed to mitochondria. Finally, overexpression of DJ-1 leads to increased viability of cells exposed to oxidative stress.
Conclusions: :
DJ-1 is expressed in retinal tissue using both biochemical and immunohistological studies. Upon exposure to oxidative stress DJ-1 expression increased. In addition, DJ-1 expression is involved in the oxidative stress response in RPE cells in vitro.
Keywords: immunohistochemistry • retina • retinal pigment epithelium