Selenium (Se) is an essential micronutrient important for many aspects of human health, including optimal immune responses. The biological effects of Se are exerted mainly through its incorporation into selenoproteins as the amino acid, selenocysteine (Sec). Twenty-five selenoproteins have been identified in humans, all but one of which also exists as Sec-containing proteins in mice and rats. One selenoprotein for which no function has been identified is selenoprotein K (Sel K). Our preliminary data indicate Sel K protein expression is highest in immune cells, localizing to the endoplasmic reticulum (ER) membrane in T cells, monocytes, and macrophages. We have identified a novel interaction between Sel K and STIM1, which is a key signaling molecule required for store-operated for calcium (Ca2+) entry during activation of immune cells. Furthermore, reduced expression of Sel K caused defects in Ca2+-dependent activation of T cells and macrophages. These findings have led to our central hypothesis that Sel K plays a key role in Ca2+-dependent activation of immune cells by regulating ER to plasma membrane signaling through its interactions with STIM1 and other signaling molecules. Our proposed research objective is to determine specific mechanisms by which Sel K regulates the functions of T cells and elucidate its overall role in innate and adaptive immunity. The proposed study includes three aims:
Specific Aim 1). Determine the mechanisms by which Sel K regulates signaling from ER to the plasma membrane during the activation of T cells;
Specific Aim 2). Determine the in vivo function of Sel K in immune responses;
and Specific Aim 3). Determine the role of Sel K in protecting against viral infection. Our experimental design involves in vitro experiments using HEK293 and Jurkat T cells for overexpression of full-length, mutated, or truncated versions of Sel K to identify domains of Sel K required for interactions with STIM1, and to determine how these interactions affect STIM1 oligomerization and downstream Ca2+-dependent signaling events during T cell activation. In addition, the extent to which Sel K and STIM1 interact over the course of T cell activation will be determined using co-immunoprecipitation and fluorescence-based assays.
For Specific Aim 2, we have developed novel transgenic mice with Sel K deleted in T cells (Lck-Cre) or myeloid cells including macrophages and neutrophils (Lyzs-Cre). These mice will be analyzed for development of T cells and macrophages in lymphoid tissues, activation and homing of T cell and macrophage in peripheral tissues, immune responses to antigenic challenge, and activation capacity of ex vivo T cells and macrophages.
For Specific Aim 3, three strains of mice will be used that have Sel K deleted in T cells (Lck-Cre), myeloid cells (Lyzs-Cre), or brain neurons (CaMKII21-Cre). An established protocol will be utilized to infect these mice with footpad injections of WNV. We will then evaluate levels of anti-WNV immune responses and severity of infection in a time-course manner by measuring plasma anti-WNV IgM, viral load in peripheral tissues and brain, survival analyses, and other readouts. Overall, elucidating the function of Sel K in immune cells will provide valuable insight into mechanisms by which Se influences immune responses and may provide a more selective therapeutic target for augmenting immune cell function with fewer side-effects compared to Se supplementation.
Selenium is an essential micronutrient that influences immunity and the biological effects of selenium are exerted mainly through its incorporation into selenoproteins. One selenoprotein for which no function has been identified is selenoprotein K, which we have found is most abundant in immune cells. The goal of this project is to determine how selenoprotein K is involved in modulating immune responses and this knowledge will provide valuable insight into mechanisms by which selenium influences immune responses.
|Rose, Aaron H; Bertino, Pietro; Hoffmann, Fukun W et al. (2014) Increasing dietary selenium elevates reducing capacity and ERK activation associated with accelerated progression of select mesothelioma tumors. Am J Pathol 184:1041-9|
|Bertino, Pietro; Urschitz, Johann; Hoffmann, Fukun W et al. (2014) Vaccination with a piggyBac plasmid with transgene integration potential leads to sustained antigen expression and CD8(+) T cell responses. Vaccine 32:1670-7|
|Meiler, Svenja; Baumer, Yvonne; Huang, Zhi et al. (2013) Selenoprotein K is required for palmitoylation of CD36 in macrophages: implications in foam cell formation and atherogenesis. J Leukoc Biol 93:771-80|
|Lee, Byung Cheon; Peterfi, Zalan; Hoffmann, Fukun W et al. (2013) MsrB1 and MICALs regulate actin assembly and macrophage function via reversible stereoselective methionine oxidation. Mol Cell 51:397-404|
|Bertino, Pietro; Panigada, Maddalena; Soprana, Elisa et al. (2013) Fowlpox-based survivin vaccination for malignant mesothelioma therapy. Int J Cancer 133:612-23|
|Huang, Zhi; Rose, Aaron H; Hoffmann, FuKun W et al. (2013) Calpastatin prevents NF-*B-mediated hyperactivation of macrophages and attenuates colitis. J Immunol 191:3778-88|
|Huang, Zhi; Rose, Aaron H; Hoffmann, Peter R (2012) The role of selenium in inflammation and immunity: from molecular mechanisms to therapeutic opportunities. Antioxid Redox Signal 16:705-43|
|Huang, Zhi; Hoffmann, Fukun W; Fay, Jeffrey D et al. (2012) Stimulation of unprimed macrophages with immune complexes triggers a low output of nitric oxide by calcium-dependent neuronal nitric-oxide synthase. J Biol Chem 287:4492-502|
|Huang, Zhi; Hoffmann, Fukun W; Norton, Robert L et al. (2011) Selenoprotein K is a novel target of m-calpain, and cleavage is regulated by Toll-like receptor-induced calpastatin in macrophages. J Biol Chem 286:34830-8|
|Verma, Saguna; Hoffmann, FuKun W; Kumar, Mukesh et al. (2011) Selenoprotein K knockout mice exhibit deficient calcium flux in immune cells and impaired immune responses. J Immunol 186:2127-37|