Mitochondrial uncoupling proteins UCP4 and UCP5 from the Pacific white shrimp Litopenaeus vannamei.

Mitochondrial uncoupling proteins (UCP) transport protons from the intermembrane space to the mitochondrial matrix uncoupling oxidative phosphorylation. In mammals, these proteins have been implicated in several cellular functions ranging from thermoregulation to antioxidant defense. In contrast, their invertebrate homologs have been much less studied despite the great diversity of species. In this study, two transcripts encoding mitochondrial uncoupling proteins were, for the first time, characterized in crustaceans. The white shrimp Litopenaeus vannamei transcript LvUCP4 is expressed in all tested shrimp tissues/organs, and its cDNA includes a coding region of 954 bp long which encodes a deduced protein 318 residues long and a predicted molecular weight of 35.3 kDa. The coding region of LvUCP5 transcript is 906 bp long, encodes a protein of 302 residues with a calculated molecular weight of 33.17 kDa. Both proteins share homology with insect UCPs, their predicted structures show the conserved motifs of the mitochondrial carrier proteins and were confirmed to be located in the mitochondria through a Western blot analysis. The genic expression of LvUCP4 and LvUCP5 was evaluated in shrimp at oxidative stress conditions and results were compared to some antioxidant enzymes to infer about their antioxidant role. LvUCP4 and LvUCP5 genes expression did not change during hypoxia/re-oxygenation, and no coordinated responses were detected with antioxidant enzymes at the transcriptional level. Results confirmed UCPs as the first uncoupling mechanism reported in this species, but their role in the oxidative stress response remains to be confirmed.

Parkinson's disease-related DJ-1 modulates the expression of uncoupling protein 4 against oxidative stress.

Loss of function mutations of DJ-1 (PARK7) have been linked to the pathogenesis of Parkinson's disease. Antioxidative stress is one of the multi-protective functions of DJ-1, and oxidation of cysteine 106 has been proposed to regulate the protective activity of DJ-1. Uncoupling protein 4 (UCP4) is located in the inner membrane of mitochondria and functions to protect against oxidative stress. In this study, we used neuronal (SH-SY5Y) cells and DJ-1 knockout mice to elucidate whether DJ-1 regulated oxidative stress via modulating the expression of UCP4, and the underlying mechanism. The downstream products of oxidative stress, mitochondrial membrane potential (ΔΨm) and cell viability were also investigated. We found that UCP4 was up-regulated upon 1-methyl-4-phenylpyridinium (MPP+ ) stimulation in SH-SY5Y cells, which was enhanced by wild type DJ-1 and alleviated by DJ-1 knockdown. Expression of UCP4 in DJ-1 knockout mice was lower compared with wild-type mice. In addition, up-regulation of UCP4 was alleviated by inhibition of oxidized DJ-1, and enhanced by increase in oxidized DJ-1 under conditions of oxidative stress using western blot analysis. Moreover, over-expression of UCP4 in DJ-1 knockdown cells partially reversed the decrease in cell viability, ΔΨm, as well as the increase in products of oxidative stress upon MPP+ stimulation. Furthermore analysis showed that DJ-1 regulated transcriptional activity of UCP4 partially via Nuclear factor-kappa B (NF-κB) pathway in the presence of MPP+ . Together, our results suggested DJ-1 might regulate the expression of UCP4 by oxidation of DJ-1 and partially via NF-κB pathway in its protective response to oxidative stress.