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Sirtuins are NAD+-dependent protein lysine deacylases implicated in metabolic regulation and aging-related dysfunctions. The nuclear isoform Sirt1 deacetylates histones and transcription factors and contributes, e.g., to brain and immune cell functions. Upon infection by human immunodeficiency virus 1 (HIV1), Sirt1 deacetylates the viral transactivator of transcription (Tat) protein to promote the expression of the viral genome. Tat, in turn, inhibits Sirt1, leading to the T cell hyperactivation associated with HIV infection. Here, we describe the molecular mechanism of Tat-dependent sirtuin inhibition. Using Tat-derived peptides and recombinant Tat protein, we mapped the inhibitory activity to Tat residues 34–59, comprising Tat core and basic regions and including the Sirt1 deacetylation site Lys50. Tat binds to the sirtuin catalytic core and inhibits Sirt1, Sirt2, and Sirt3 with comparable potencies. Biochemical data and crystal structures of sirtuin complexes with Tat peptides reveal that Tat exploits its intrinsically extended basic region for binding to the sirtuin substrate binding cleft through substrate-like β-strand interactions, supported by charge complementarity. Tat Lys50 is positioned in the sirtuin substrate lysine pocket, although binding and inhibition do not require prior acetylation and rely on subtle differences to the binding of regular substrates. Our results provide mechanistic insights into sirtuin regulation by Tat, improving our understanding of physiological sirtuin regulation and the role of this interaction during HIV1 infection.

Nucleolar stress is a cellular response to inhibition of ribosome biogenesis or nucleolar disruption leading to cell cycle arrest and/or apoptosis. Emerging evidence points to a tight connection between nucleolar stress and autophagy as a mechanism underlying various diseases such as neurodegeneration and treatment of cancer. Peter Pan (PPAN) functions as a key regulator of ribosome biogenesis. We previously showed that human PPAN localizes to nucleoli and mitochondria and that PPAN knockdown triggers a p53-independent nucleolar stress response culminating in mitochondrial apoptosis. Here, we demonstrate a novel role of PPAN in the regulation of mitochondrial homeostasis and autophagy. Our present study characterizes PPAN as a factor required for maintaining mitochondrial integrity and respiration-coupled ATP production. PPAN interacts with cardiolipin, a lipid of the inner mitochondrial membrane. Down-regulation of PPAN enhances autophagic flux in cancer cells. PPAN knockdown promotes recruitment of the E3-ubiquitin ligase Parkin to damaged mitochondria. Moreover, we provide evidence that PPAN knockdown decreases mitochondrial mass in Parkin-expressing cells. In summary, our study uncovers that PPAN knockdown is linked to mitochondrial damage and stimulates autophagy.

Setup and management of smart home systems is a complex task, and thus challenging for technically inexperienced users. We conducted a qualitative user study to evaluate whether an assistance system could empower users to make better and informed decisions regarding the selection of devices, their interoperability, the resulting set of features and their price. A group of 20 participants used our assistance app on a smartphone to configure a smart home while optimizing for features, interoperability, and the price-performance ratio. The results of our user study show that our assistance app can ease the problem of selecting useful devices and at the same time users become aware of new features resulting from the interoperation of selected devices. Furthermore, the assistance app can counteract the inherent interoperability problem between devices of different vendors or platforms. Finally, users are not only interested in individual device prices. They want to learn the cost of a certain feature set, including the cost of all devices necessary to realize this feature. Interestingly, none of the current smart home systems on the market offer a comparable assistance mechanism. Third-party solutions are not available either, because an assistance app requires meta data about features, interoperability, and usage of devices. This meta data is currently not available via APIs in state-of-the-art smart home systems and marketplaces. Therefore, we present a smart home architecture resulting from our research that can, among other benefits, provide the necessary meta data. Our research indicates that commercial smart home systems should invest more effort in user assistance to gain widespread adoption among technically inexperienced users. This in turn requires substantial changes to the meta data management in smart homes, because otherwise these assistance systems cannot be realized.

La mayoría de los profesores chilenos están sometidos a altas demandas y condiciones laborales deficientes que afectan su bienestar. El objetivo de este estudio es evaluar la factibilidad de elevar el bienestar docente a través de una intervención cognitivoexperiencial basada en evidencias de la Psicología Positiva y las Neurociencias. Se diseñó e implementó un taller con 7 sesiones (19 horas). Participaron 31 educadores de un colegio de alta vulnerabilidad de Santiago de Chile. Se evaluó su bienestar utilizando una batería de 7 test de autorreporte validados al inicio, al finalizar y a los dos meses de la intervención. Se llevó a cabo un análisis cuantitativo no probabilístico de las variables y se comparó con el análisis cualitativo de testimonios de los participantes. Los resultados indicaron avances significativos en cinco de los siete test: Bienestar Psicológico (Ryff), Felicidad (PEM), Afectividad Positiva y Negativa (PANAS), Esperanza y Burnout (Maslach). A los dos meses la mayoría de los cambios retornaron a niveles basales, pero las variables Autoaceptación (Ryff) y Vida Placentera (Felicidad) se mantuvieron elevadas. En conclusión, la intervención se asocia con un impacto positivo sobre el bienestar docente. Se estima que con reforzamiento periódico estos cambios podrían mantenerse, constituyendo tema para una nueva investigación.

The potential benefits of corticosteroids for septic shock may depend on initial mortality risk.We determined associations between corticosteroids and outcomes in children with septic shock who were stratified by initial mortality risk.We conducted a retrospective analysis of an ongoing, multi-center pediatric septic shock clinical and biological database. Using a validated biomarker-based stratification tool (PERSEVERE), 496 subjects were stratified into three initial mortality risk strata (low, intermediate, and high). Subjects receiving corticosteroids during the initial 7 days of admission (n = 252) were compared to subjects who did not receive corticosteroids (n = 244). Logistic regression was used to model the effects of corticosteroids on 28-day mortality and complicated course, defined as death within 28 days or persistence of two or more organ failures at 7 days.Subjects who received corticosteroids had greater organ failure burden, higher illness severity, higher mortality, and a greater requirement for vasoactive medications, compared to subjects who did not receive corticosteroids. PERSEVERE-based mortality risk did not differ between the two groups. For the entire cohort, corticosteroids were associated with increased risk of mortality (OR 2.3, 95% CI 1.3-4.0, p = 0.004) and a complicated course (OR 1.7, 95% CI 1.1-2.5, p = 0.012). Within each PERSEVERE-based stratum, corticosteroid administration was not associated with improved outcomes. Similarly, corticosteroid administration was not associated with improved outcomes among patients with no comorbidities, nor in groups of patients stratified by PRISM.Risk stratified analysis failed to demonstrate any benefit from corticosteroids in this pediatric septic shock cohort.

We previously derived and validated a risk model to estimate mortality probability in children with septic shock (PERSEVERE; PEdiatRic SEpsis biomarkEr Risk modEl). PERSEVERE uses five biomarkers and age to estimate mortality probability. After the initial derivation and validation of PERSEVERE, we combined the derivation and validation cohorts (n = 355) and updated PERSEVERE. An important step in the development of updated risk models is to test their accuracy using an independent test cohort.To test the prognostic accuracy of the updated version PERSEVERE in an independent test cohort.Study subjects were recruited from multiple pediatric intensive care units in the United States. Biomarkers were measured in 182 pediatric subjects with septic shock using serum samples obtained during the first 24 hours of presentation. The accuracy of PERSEVERE 28-day mortality risk estimate was tested using diagnostic test statistics, and the net reclassification improvement (NRI) was used to test whether PERSEVERE adds information to a physiology-based scoring system.Mortality in the test cohort was 13.2%. Using a risk cut-off of 2.5%, the sensitivity of PERSEVERE for mortality was 83% (95% CI 62-95), specificity was 75% (68-82), positive predictive value was 34% (22-47), and negative predictive value was 97% (91-99). The area under the receiver operating characteristic curve was 0.81 (0.70-0.92). The false positive subjects had a greater degree of organ failure burden and longer intensive care unit length of stay, compared to the true negative subjects. When adding PERSEVERE to a physiology-based scoring system, the net reclassification improvement was 0.91 (0.47-1.35; p

PERSEVERE is a risk model for estimating mortality probability in pediatric septic shock, using five biomarkers measured within 24 hours of clinical presentation.Here, we derive and test a temporal version of PERSEVERE (tPERSEVERE) that considers biomarker values at the first and third day following presentation to estimate the probability of a "complicated course", defined as persistence of ≥2 organ failures at seven days after meeting criteria for septic shock, or death within 28 days.Biomarkers were measured in the derivation cohort (n = 225) using serum samples obtained during days 1 and 3 of septic shock. Classification and Regression Tree (CART) analysis was used to derive a model to estimate the risk of a complicated course. The derived model was validated in the test cohort (n = 74), and subsequently updated using the combined derivation and test cohorts.A complicated course occurred in 23% of the derivation cohort subjects. The derived model had a sensitivity for a complicated course of 90% (95% CI 78-96), specificity was 70% (62-77), positive predictive value was 47% (37-58), and negative predictive value was 96% (91-99). The area under the receiver operating characteristic curve was 0.85 (0.79-0.90). Similar test characteristics were observed in the test cohort. The updated model had a sensitivity of 91% (81-96), a specificity of 70% (64-76), a positive predictive value of 47% (39-56), and a negative predictive value of 96% (92-99).tPERSEVERE reasonably estimates the probability of a complicated course in children with septic shock. tPERSEVERE could potentially serve as an adjunct to physiological assessments for monitoring how risk for poor outcomes changes during early interventions in pediatric septic shock.