Alteration of selenoprotein expression during stress and in aging

International audienceSelenium (Se) is an essential trace element implicated in many facets of human health and disease. Most of its beneficial effects are attributed to its presence as selenocysteine in a small, but vital group of proteins, namely the selenoproteins. They are implicated in antioxidant defense, redox homeostasis, redox signaling and possibly other cellular processes. The selenoproteome is primarily controlled by Se bioavailability that induces prioritization of protein biosynthesis, when this trace element is deficient. The hierarchical regulation of the selenoproteome by other exogenous stimuli, cellular stressors or pathophysiological conditions is poorly understood. Understanding biological causes of aging also remains challenging, although several theories and concepts have emerged in the past decades. Characterization of biomarkers of aging is controversial even with the impressive amount of ‘omic’ analyses performed in many living organisms. Accumulation of age-related damage, including oxidative-induced cellular damage, and the decreasing efficiency in elimination and repair systems have been extensively reported, being either a cause or consequence of the aging phenomenon. In this regard, and given the role of Se in redox biology of organisms, studying regulation of the selenoproteome in response to oxidative stress and aging is essential. This chapter reviews the current knowledge in this area

Speciation analysis for trace levels of selenoproteins in cultured human cells

International audienceA semi-quantitative method was developed for the non-targeted detection of trace levels of human selenoproteins in cytoplasmic cell extracts without the use of radioactive isotopes. The method was based on the direct detection of selenoproteins in iso-electrofocusing (IEF) electrophoretic strips by laser ablation-inductively coupled plasma mass spectrometry (LA-ICP MS). The proteins were identified in the non-ablated parts of the gel corresponding to the LA-ICP MS peak apexes by electrospray Orbitrap MS/MS. The method allowed a high resolution of the selenoproteins (peak width 0.06pH unit) using 3-10 pI strips. The protein detection limits were down to 1ngmL-1 (as Se). The method was applied to the selenoprotein speciation in different human cell lines: Hek293 (kidney), HepG2 (liver), HaCaT (skin) and LNCaP (prostate). The principal proteins found included Selenoprotein 15 (Sep15), Glutathione peroxidase 1 (GPx1) and Glutathione peroxidase 4 (GPx4) and Thioredoxin reductase 1 (TRxR1) and Thioredoxin reductase 2 (TRxR2). Biological significance: Our paper presents the development of a semi-quantitative method for the non-targeted detection of trace levels of human selenoproteins in cytoplasmic cell extracts; it offers a first comprehensive screening of the entire biological selenoproteomes expressed in cell lines without the use of radioactive 75Se. The method was based on the direct detection of selenoproteins in iso-electrofocusing (IEF) electrophoretic strips by laser ablation-inductively coupled plasma mass spectrometry (LA-ICP MS). The proteins were identified in the non-ablated parts of the gel corresponding to the LA-ICP MS peak apexes by electrospray Orbitrap MS/MS. The method allowed a high resolution of the selenoproteins (peak width 0.06pH unit) using 3-10 pI strips. The protein detection limits were down to 1ngmL-1 (as Se); by far the lowest ever reported. The method was applied to the selenoprotein speciation in different human cell lines: Hek293 (kidney), HepG2 (liver), HaCaT (skin) and LNCaP (prostate). The principal proteins found included Selenoprotein 15 (Sep15), Glutathione peroxidase 1 (GPx1) and Glutathione peroxidase 4 (GPx4) and Thioredoxin reductase 1 (TRxR1) and Thioredoxin reductase 2 (TRxR2). The IEF-LA-ICPMS indicates the presence of multiple forms of some selenoproteins which are for the moment impossible to distinguish because of the similarity of the bottom-up, proteomics data sets

DPAGT1 deficiency with encephalopathy (DPAGT1-CDG) : Clinical and genetic description of 11 new patients

Pathogenic mutations in DPAGT1 cause a rare type of a congenital disorder of glycosylation termed DPAGT1-CDG or, alternatively, a milder version with only myasthenia known as DPAGT1-CMS. Fourteen disease-causing mutations in 28 patients from 10 families have previously been reported to cause the systemic form, DPAGT1-CDG. We here report on another 11 patients from 8 families and add 10 new mutations. Most patients have a very severe disease course, where common findings are pronounced muscular hypotonia, intractable epilepsy, global developmental delay/intellectual disability, and early death. We also present data on three affected females that are young adults and have a somewhat milder, stable disease. Our findings expand both the molecular and clinical knowledge of previously published data but also widen the phenotypic spectrum of DPAGT1-CDG

Oxidative stress due to Mycobacterium avium subspecies paratuberculosis (MAP) infection upregulates selenium-dependent GPx activity

OBJECTIVE: This study was designed to determine the relationship between Mycobacterium avium subspecies paratuberculosis (MAP) infection and selenium-dependent glutathione peroxidase (GPx) activity, in the blood of humans and cattle infected with MAP. DESIGN: MAP infection status and GPx activity were determined in sera from 42 cattle, a group of 27 patients with Crohn’s disease and 27 of their healthy biological relatives, and a group of 66 subjects with various diseases other than Crohn’s disease and 34 non-related healthy subjects. RESULTS: GPx activity was significantly higher overall in the case of MAP infection in both humans and cattle. The mean value for GPx activity was 1.59 ± 0.65 units/ml in MAP positive cattle compared to 0.46907 ± 0.28 units/ml in healthy cattle sera, where a unit was defined as one mmol/minute (P < 0.01). The mean value of the GPx activity in MAP negative humans clinical sera was 0.42367 ± 0.229 units/ml compared to 0.80941 ± 0.521 in MAP positive sera in a study comparing Crohn’s disease patients to their healthy relatives. The mean activity in MAP negative humans was 0.4702 ± 0.1299 compared to 0.6510 ± 00.1665 units/ml in positive samples in a randomized field study of 100 subjects. CONCLUSION: This study demonstrated a strong correlation between MAP and the elevation of GPx activity. This was especially evident in Crohn’s patients, which further supports the association of MAP and Crohn’s disease. GPx activity may also be used to predict MAP infection status and to show that Crohn’s disease patients who are infected with MAP have higher tendency to develop oxidative stress than Crohn’s disease patients who are negative for the bacteria