Abstract
Reactive oxygen species (ROS) are frequently produced during viral infections. Generation of these ROS can be both beneficial and detrimental for many cellular functions. When overwhelming the antioxidant defense system, the excess of ROS induces oxidative stress. Viral infections lead to diseases characterized by a broad spectrum of clinical symptoms, with oxidative stress being one of their hallmarks. In many cases, ROS can, in turn, enhance viral replication leading to an amplification loop. Another important parameter for viral replication and pathogenicity is the nutritional status of the host. Viral infection simultaneously increases the demand for micronutrients and causes their loss, which leads to a deficiency that can be compensated by micronutrient supplementation. Among the nutrients implicated in viral infection, selenium (Se) has an important role in antioxidant defense, redox signaling and redox homeostasis. Most of biological activities of selenium is performed through its incorporation as a rare amino acid selenocysteine in the essential family of selenoproteins. Selenium deficiency, which is the main regulator of selenoprotein expression, has been associated with the pathogenicity of several viruses. In addition, several selenoprotein members, including glutathione peroxidases (GPX), thioredoxin reductases (TXNRD) seemed important in different models of viral replication. Finally, the formal identification of viral selenoproteins in the genome of molluscum contagiosum and fowlpox viruses demonstrated the importance of selenoproteins in viral cycle.
Highlights
Selenium is an essential trace element for mammalian redox biology
Within the well characterized selenoproteins we find the following sub-families: Glutathione peroxidase (GPX1–GPX4 and GPX6) that reduce hydrogen and lipid peroxides [25], thioredoxin reductases (TXNRD1–TXNRD3) which are essentials in the homeostasis of thiol systems [26,27,28,29], methionine sulfoxide reductase (MSRB1) [30] and selenoproteins located in the endoplasmic reticulum (DIO2, SELENOF, SELENOK, SELENOM, SELENON, SELENOS and SELENOT)
Putative Selenoproteins in Other Viral Genomes. These two examples of selenoprotein gene snatching from eukaryotic genomes in the viral genomes of fowlpox and molluscum contagiosum viruses lead to the careful investigation for further examples of selenoprotein genes sequences with viral genomes
Summary
Selenium is an essential trace element for mammalian redox biology. Most of the beneficial effects of selenium is due to its incorporation in the form of selenocysteine into an essential group of proteins that are called selenoproteins. Amongst the twenty-five selenoprotein genes identified to date, several have important cellular functions in antioxidant defense, cell signaling and redox homeostasis [24]. Exhibit important functions in protein folding and in the endoplasmic reticulum stress response [31,32,33]. Selenoproteins are important components of antioxidant defense systems maintaining redox homeostasis, which include catalase (CAT), superoxide dismutase (SOD), glutathione (GSH), vitamin E, carotenoids, and ascorbic acid. The mechanisms of ROS generation by the various viruses are diverse, but in several cases the host antioxidant defense enzymes, and especially members of the selenoproteome, are targeted
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