Human mitochondrial 5'-deoxyribonucleotidase. Overproduction in cultured cells and functional aspects.

Deoxynucleoside triphosphates (dNTPs) used for mitochondrial DNA replication are mainly formed by phosphorylation of deoxynucleosides imported into mitochondria from the cytosol. We earlier obtained evidence for a mitochondrial 5′-nucleotidase (dNT2) with a pronounced specificity for dUMP and dTMP and suggested that the enzyme protects mitochondrial DNA replication from excess dTTP. In humans, accumulation of dTTP causes a mitochondrial genetic disease. We now establish that dNT2 in vivo indeed is located in mitochondria. The native enzyme shows the same substrate specificity and affinity for inhibitors as the recombinant dNT2. We constructed ponasterone-inducible cell lines overproducing dNT2 with and without the green fluorescent protein (GFP) linked to its C terminus. The fusion protein occurred in mitochondria mostly in an inactive truncated form, with only a short C-terminal fragment of dNT2 linked to GFP. No truncation occurred when dNT2 and GFP were not linked. The cell mitochondria then contained a large excess of active dNT2 with or without the mitochondrial presequence. After removal of ponasterone overproduced dNT2 disappeared only slowly from the cells, whereas dNT2-mRNA was lost rapidly. Overproduction of dNT2 did not lead to an increased excretion of pyrimidine deoxyribonucleosides, in contrast to overproduction of the corresponding cytosolic deoxynucleotidase, suggesting that the mitochondrial enzyme does not affect overall cellular deoxynucleotide turnover

Proteasome system dysregulation and treatment resistance mechanisms in major depressive disorder

Several studies have demonstrated that allelic variants related to inflammation and the immune system may increase the risk for major depressive disorder (MDD) and reduce patient responsiveness to antidepressant treatment. Proteasomes are fundamental complexes that contribute to the regulation of T-cell function. Only one study has shown a putative role of proteasomal PSMA7, PSMD9 and PSMD13 genes in the susceptibility to an antidepressant response, and sparse data are available regarding the potential alterations in proteasome expression in psychiatric disorders such as MDD. The aim of this study was to clarify the role of these genes in the mechanisms underlying the response/resistance to MDD treatment. We performed a case-control association study on 621 MDD patients, of whom 390 were classified as treatment-resistant depression (TRD), and we collected peripheral blood cells and fibroblasts for mRNA expression analyses. The analyses showed that subjects carrying the homozygous GG genotype of PSMD13 rs3817629 had a twofold greater risk of developing TRD and exhibited a lower PSMD13 mRNA level in fibroblasts than subjects carrying the A allele. In addition, we found a positive association between PSMD9 rs1043307 and the presence of anxiety disorders in comorbidity with MDD, although this result was not significant following correction for multiple comparisons. In conclusion, by confirming the involvement of PSMD13 in the MDD treatment response, our data corroborate the hypothesis that the dysregulation of the complex responsible for the degradation of intracellular proteins and potentially controlling autoimmunity- and immune tolerance–related processes may be involved in several phenotypes, including the TRD

Indoxyl Sulfate Induces Renal Fibroblast Activation through a Targetable Heat Shock Protein 90-Dependent Pathway

Indoxyl sulfate (IS) accumulation occurs early during chronic kidney disease (CKD) progression and contributes to renal dysfunction by inducing fibrosis, inflammation, oxidative stress, and tissue remodeling. Renal toxicity of high IS concentrations (250\u2009\u3bcM) has been widely explored, particularly in resident tubular and glomerular cells, while the effect of a moderate IS increase on kidneys is still mostly unknown. To define the effects of IS accumulation on renal fibroblasts, we first analyzed kidneys of C57BL/6 mice receiving IS (0.1%) in drinking water for 12 weeks. As a next step, we treated renal fibroblasts (NRK-49F) with IS (20\u2009\u3bcM) with or without the HSP90 inhibitor 17-AAG (1\u2009\u3bcM). In mouse kidneys, IS increased the collagen deposition and HSP90 and \u3b1-SMA expression (immunohistochemistry) in interstitial fibroblasts and caused tubular necrosis (histological H&E and picrosirius red staining). In NRK-49F cells, IS induced MCP1, TGF-\u3b2, collagen I, \u3b1-SMA, and HSP90 gene/protein expression and Smad2/3 pathway activation. IS had no effects on fibroblast proliferation and ROS production. 17-AAG counteracted IS-induced MCP1, TGF-\u3b2, collagen I, and \u3b1-SMA expression and Smad2/3 phosphorylation. Our study demonstrates that the IS increase promotes renal fibroblast activation by a HSP90-dependent pathway and indicates HSP90 inhibition as a potential strategy to restrain IS-induced kidney inflammation and fibrosis in CKD

Tricuspid regurgitant velocity elevation in a three-year old child with sickle cell anemia and recurrent acute chest syndromes reversed not by hydroxyurea but by bone marrow transplantation

Elevated Tricuspid Regurgitant Velocity (TRV) has been related to higher mortality in adults and to hemolysis, lower oxygen saturation during 6-minute walk test and acute chest syndrome (ACS) in children with sickle cell disease (SCD). Hydroxyurea (HU) has reduced TRV value in children and adults. We describe a three year old HbSS child with recurrent ACS, hypoperfusion of the left lung, mild hemolysis and persistent TRV elevation. TRV did not normalize after HU, despite improvement in clinical conditions and in baseline laboratory parameters related to hemolysis and blood viscosity, but normalized after bone marrow transplantation (BMT). Our experience suggests that in young patients, TRV reduction can be a positive concomitant effect of BMT

The Organ Handling of Soluble Klotho in Humans

Chronic kidney disease (CKD) reduces both Klotho expression and its shedding into circulation, an effect that accelerates progression and cardiovascular complications. However, the mechanisms that regulate Klotho release by the human kidney are still unknown. Methods: We measured plasma Klotho across the kidney, splanchnic organs and lung in 22 patients (71 \ub1 2 years, estimated glomerular filtration rate [eGFR] 60 \ub1 5.4 mL/min 1.73 m2) during elective diagnostic cardiac catheterizations. Results: Although the Klotho average renal vein concentrations were remarkably higher (by ~9%) than arterial values, the kidney removed Klotho (or was at zero balance) in 7 subjects, indicating that the kidney contribution to systemic Klotho is not constant. Klotho fractional enrichment across the kidney was inversely related to plasma sodium (r = 0.43, p = 0.045) and acid uric acid levels (r = 0.38, p = 0.084) and directly, to renal oxygen extraction (r = 0.56, p = 0.006). In multivariate analysis, renal oxygen extraction was the only predictor of the enrichment of Klotho across the kidney, suggesting the dependence of renal Klotho release on tubular hypoxia or oxidative metabolism. Klotho balance was neutral across the lung. In patients with eGFR <60 mL/min, Klotho was also removed by splanchnic organs (single pass fractional extraction ~11%). Conclusions: The present study identifies kidney oxygen uptake as a predictor of Klotho release, and splanchnic organs as a site for Klotho removal. This study provides new understanding of kidney Klotho release and suggests that modulating kidney oxygen metabolism could increase Klotho delivery, as an option to slow disease progression and blunt organ damage

Serum BPIFB4 levels classify health status in long-living individuals

People that reach extreme ages (Long-Living Individuals, LLIs) are object of intense investigation for increase/decrease of genetic variant frequencies, genetic methylation levels, protein abundance in serum and tissues. The aim of these studies is the discovery of the mechanisms behind LLIs extreme longevity and the identification of markers of well-being. We have recently associated a BPIFB4 haplotype (LAV) with exceptional longevity under a homozygous genetic model, and identified that CD34(+) of LLIs subjects express higher BPIFB4 transcript as compared to CD34(+) of control population. It would be of interest to correlate serum BPIFB4 protein levels with exceptional longevity and health status of LLIs

Erratum to: Radiosurgery reirradiation for high-grade glioma recurrence: a retrospective analysis

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An innovative strategy to investigate microbial protein modifications in a reliable fast and sensitive way: A therapy oriented proof of concept based on UV-C irradiation of SARS-CoV-2 spike protein

: The characterization of modifications of microbial proteins is of primary importance to dissect pathogen lifecycle mechanisms and could be useful in identifying therapeutic targets. Attempts to solve this issue yielded only partial and non-exhaustive results. We developed a multidisciplinary approach by coupling in vitro infection assay, mass spectrometry (MS), protein 3D modelling, and surface plasma resonance (SPR). As a proof of concept, the effect of low UV-C (273 nm) irradiation on SARS-CoV-2 spike (S) protein was investigated. Following UV-C exposure, MS analysis identified, among other modifications, the disruption of a disulphide bond within the conserved S2 subunit of S protein. Computational analyses revealed that this bond breakage associates with an allosteric effect resulting in the generation of a closed conformation with a reduced ability to bind the ACE2 receptor. The UV-C-induced reduced affinity of S protein for ACE2 was further confirmed by SPR analyses and in vitro infection assays. This comprehensive approach pinpoints the S2 domain of S protein as a potential therapeutic target to prevent SARS-CoV-2 infection. Notably, this workflow could be used to screen a wide variety of microbial protein domains, resulting in a precise molecular fingerprint and providing new insights to adequately address future epidemics