Role of SEP15 Gene Polymorphisms in the Time of Progression to AIDS

Current Understanding of Human Polymorphism in Selenoprotein Genes: A Review of Its Significance as a Risk Biomarker

Selenium has been proven to influence several biological functions, showing to be an essential micronutrient. The functional studies demonstrated the benefits of a balanced selenium diet and how its deficiency is associated with diverse diseases, especially cancer and viral diseases. Selenium is an antioxidant, protecting the cells from damage, enhancing the immune system response, preventing cardiovascular diseases, and decreasing inflammation. Selenium can be found in its inorganic and organic forms, and its main form in the cells is the selenocysteine incorporated into selenoproteins. Twenty-five selenoproteins are currently known in the human genome: glutathione peroxidases, iodothyronine deiodinases, thioredoxin reductases, selenophosphate synthetase, and other selenoproteins. These proteins lead to the transport of selenium in the tissues, protect against oxidative damage, contribute to the stress of the endoplasmic reticulum, and control inflammation. Due to these functions, there has been growing interest in the influence of polymorphisms in selenoproteins in the last two decades. Selenoproteins' gene polymorphisms may influence protein structure and selenium concentration in plasma and its absorption and even impact the development and progression of certain diseases. This review aims to elucidate the role of selenoproteins and understand how their gene polymorphisms can influence the balance of physiological conditions. In this polymorphism review, we focused on the PubMed database, with only articles published in English between 2003 and 2023. The keywords used were "selenoprotein" and "polymorphism". Articles that did not approach the theme subject were excluded. Selenium and selenoproteins still have a long way to go in molecular studies, and several works demonstrated the importance of their polymorphisms as a risk biomarker for some diseases, especially cardiovascular and thyroid diseases, diabetes, and cancer.

Selenium, Selenoproteins and Viral Infection

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.

Role of Selenoprotein F in Protein Folding and Secretion: Potential Involvement in Human Disease

Selenoproteins form a group of proteins of which its members contain at least one selenocysteine, and most of them serve oxidoreductase functions. Selenoprotein F (SELENOF), one of the 25 currently identified selenoproteins, is located in the endoplasmic reticulum (ER) organelle and is abundantly expressed in many tissues. It is regulated according to its selenium status, as well as by cell stress conditions. SELENOF may be functionally linked to protein folding and the secretion process in the ER. Several studies have reported positive associations between SELENOF genetic variations and several types of cancer. Also, altered expression levels of SELENOF have been found in cancer cases and neurodegenerative diseases. In this review, we summarize the current understanding of the structure, expression, and potential function of SELENOF and discuss its possible relation with various pathological processes.

Analysis of the Interactions Between Thioredoxin and 20 Selenoproteins in Chicken

Thioredoxin (Trx) is a small molecular protein with complicated functions in a number of processes, including inflammation, apoptosis, embryogenesis, cardiovascular disease, and redox regulation. Some selenoproteins, such as glutathione peroxidase (Gpx), iodothyronine deiodinase (Dio), and thioredoxin reductase (TR), are involved in redox regulation. However, whether there are interactions between Trx and selenoproteins is still not known. In the present paper, we used a Modeller, Hex 8.0.0, and the KFC2 Server to predict the interactions between Trx and selenoproteins. We used the Modeller to predict the target protein in objective format and assess the accuracy of the results. Molecular interaction studies with Trx and selenoproteins were performed using the molecular docking tools in Hex 8.0.0. Next, we used the KFC2 Server to further test the protein binding sites. In addition to the selenoprotein physiological functions, we also explored potential relationships between Trx and selenoproteins beyond all the results we got. The results demonstrate that Trx has the potential to interact with 19 selenoproteins, including iodothyronine deiodinase 1 (Dio1), iodothyronine deiodinase 3 (Dio3), glutathione peroxidase 1 (Gpx1), glutathione peroxidase 2 (Gpx2), glutathione peroxidase 3 (Gpx3), glutathione peroxidase 4 (Gpx4), selenoprotein H (SelH), selenoprotein I (SelI), selenoprotein M (SelM), selenoprotein N (SelN), selenoprotein T (SelT), selenoprotein U (SelU), selenoprotein W (SelW), selenoprotein 15 (Sep15), methionine sulfoxide reductase B (Sepx1), selenophosphate synthetase 1 (SPS1), TR1, TR2, and TR3, among which TR1, TR2, TR3, SPS1, Sep15, SelN, SelM, SelI, Gpx2, Gpx3, Gpx4, and Dio3 exhibited intense correlations with Trx. However, additional experiments are needed to verify them.