The ceramide activated protein phosphatase Sit4 impairs sphingolipid dynamics, mitochondrial function and lifespan in a yeast model of Niemann-Pick type C1.

The Niemann-Pick type C is a rare neurodegenerative disease that results from loss-of-function point mutations in NPC1 or NPC2, which affect the homeostasis of sphingolipids and sterols in human cells. We have previously shown that yeast lacking Ncr1, the orthologue of human NPC1 protein, display a premature ageing phenotype and higher sensitivity to oxidative stress associated with mitochondrial dysfunctions and accumulation of long chain bases. In this study, a lipidomic analysis revealed specific changes in the levels of ceramide species in ncr1Δ cells, including decreases in dihydroceramides and increases in phytoceramides. Moreover, the activation of Sit4, a ceramide-activated protein phosphatase, increased in ncr1Δ cells. Deletion of SIT4 or CDC55, its regulatory subunit, increased the chronological lifespan and hydrogen peroxide resistance of ncr1Δ cells and suppressed its mitochondrial defects. Notably, Sch9 and Pkh1-mediated phosphorylation of Sch9 decreased significantly in ncr1Δsit4Δ cells. These results suggest that phytoceramide accumulation and Sit4-dependent signaling mediate the mitochondrial dysfunction and shortened lifespan in the yeast model of Niemann-Pick type C1, in part through modulation of the Pkh1-Sch9 pathway.

Structure of Escherichia coli Flavodiiron Nitric Oxide Reductase.

Flavodiiron proteins (FDPs) are present in organisms from all domains of life and have been described so far to be involved in the detoxification of oxygen or nitric oxide (NO), acting as O2 and/or NO reductases. The Escherichia coli FDP, named flavorubredoxin (FlRd), is the most extensively studied FDP. Biochemical and in vivo studies revealed that FlRd is involved in NO detoxification as part of the bacterial defense mechanisms against reactive nitrogen species. E. coli FlRd has a clear preference for NO as a substrate in vitro, exhibiting a very low reactivity toward O2. To contribute to the understanding of the structural features defining this substrate selectivity, we determined the crystallographic structure of E. coli FlRd, both in the isolated and reduced states. The overall tetrameric structure revealed a highly conserved flavodiiron core domain, with a metallo-ß-lactamase-like domain containing a diiron center, and a flavodoxin domain with a flavin mononucleotide cofactor. The metal center in the oxidized state has a µ-hydroxo bridge coordinating the two irons, while in the reduced state, this moiety is not detected. Since only the flavodiiron domain was observed in these crystal structures, the structure of the rubredoxin domain was determined by NMR. Tunnels for the substrates were identified, and through molecular dynamics simulations, no differences for O2 or NO permeation were found. The present data represent the first structure for a NO-selective FDP.

Sphingolipid signalling mediates mitochondrial dysfunctions and reduced chronological lifespan in the yeast model of Niemann-Pick type C1.

The Niemann-Pick type C is a rare metabolic disease with a severe neurodegenerative phenotype characterized by an accumulation of high amounts of lipids (cholesterol and sphingolipids) in the late endosomal/lysosomal network. It is caused by loss-of-function point mutations in either NPC1 or NPC2, which seem to mediate proper intracellular lipid transport through endocytic pathway. In this study, we show that yeast cells lacking Ncr1p, an orthologue of mammalian NPC1, exhibited a higher sensitivity to hydrogen peroxide and a shortened chronological lifespan. These phenotypes were associated with increased levels of oxidative stress markers, decreased levels of antioxidant defences and mitochondrial dysfunctions. Moreover, we report that Ncr1p-deficient cells displayed high levels of long chain bases (LCB), and that Sch9p-phospho-T570 and Sch9p levels increased in ncr1Δ cells through a mechanism regulated by Pkh1p, a LCB-activated protein kinase. Notably, deletion of PKH1 or SCH9 suppressed ncr1Δ phenotypes but downregulation of de novo sphingolipid biosynthesis had no protective effect, suggesting that LCBs accumulation may result from an increased turnover of complex sphingolipids. These results suggest that sphingolipid signalling through Pkh1p-Sch9p mediate mitochondrial dysfunction, oxidative stress sensitivity and shortened chronological lifespan in the yeast model of Niemann-Pick type C disease.

Laminados cerâmicos na finalização dos tratamentos clínicos integrados / Laminate veneers and multidisciplinary management

de solucionar. Nestes casos, uma abordagem multidisciplinar éfundamental. Má posição dentária e margem gengival sem umcontorno adequado, normalmente, apresentam problema estético efuncional. Assim, um tratamento ortodôntico e periodontal paraadequação prévia é fundamental para o sucesso do tratamentoreabilitador. Além disso, cuidados e paciência durante todo otratamento são essenciais tanto por parte do profissional como porparte do paciente. Recentemente, os laminados cerâmicos têm sidoamplamente utilizados em dentes anteriores. Adicionalmente, essetratamento tem sido mais conservador quando comparado às coroastotais. Portanto, o presente trabalho demonstra por meio de um casoclínico, a associação da ortodontia, periodontia e dentística norestabelecimento do sorriso com laminados cerâmicos, de formaeficiente, conservadora e com resultados estéticos satisfatórios.

Some clinical cases are more complex. In these situations, amultidisciplinary approach is essential. Malposition dental and gingivalmargin without an adequate contour usually have functional andaesthetic problem. Thus, an integrated orthodontic-periodonticrestorativeapproach may enhance the aesthetic results whenprosthetic therapy itself is not feasible. Additionally, care and patiencethroughout treatment are essential for both the professional and thepatient's part. Recently, ceramic laminate veneers have been widelyused in anterior teeth. Additionally, this treatment has been moreconservative. Therefore, this article presents integrated orthodontics,periodontics and restorative smile solution.