Understanding the Differences of Danusertib's Residence Time in Aurora Kinases A/B: Dissociation Paths and Key Residues Identified using Conventional and Enhanced Molecular Dynamics Simulations.

The accurate experimental estimation of protein-ligand systems' residence time (τ) has become very relevant in drug design projects due to its importance in the last stages of refinement of the drug's pharmacodynamics and pharmacokinetics. It is now well-known that it is not sufficient to estimate the affinity of a protein-drug complex in the thermodynamic equilibrium process in in vitro experiments (closed systems), where the concentrations of the drug and protein remain constant. On the contrary, it is mandatory to consider the conformational dynamics of the system in terms of the binding and unbinding processes between protein and drugs in in vivo experiments (open systems), where their concentrations are in constant flux. This last model has been proven to dictate much of several drugs' pharmacological activities in vivo. At the atomistic level, molecular dynamics simulations can explain why some drugs are more effective than others or unveil the molecular aspects that make some drugs work better in one molecular target. Here, the protein kinases Aurora A/B, complexed with its inhibitor Danusertib, were studied using conventional and enhanced molecular dynamics (MD) simulations to estimate the dissociation paths and, therefore, the computational τ values and their comparison with experimental ones. Using classical molecular dynamics (cMD), three differential residues within the Aurora A/B active site, which seems to play an essential role in the observed experimental Danusertib's residence time against these kinases, were characterized. Then, using WT-MetaD, the relative Danusertib's residence times against Aurora A/B kinases were measured in a nanosecond time scale and were compared to those τ values observed experimentally. In addition, the potential dissociation paths of Danusertib in Aurora A and B were characterized, and differences that might be explained by the differential residues in the enzyme's active sites were found. In perspective, it is expected that this computational protocol can be applied to other protein-ligand complexes to understand, at the molecular level, the differences in residence times and amino acids that may contribute to it.

Oligogalacturonides Enhance Resistance against Aphids through Pattern-Triggered Immunity and Activation of Salicylic Acid Signaling.

The remarkable capacity of the generalist aphid Myzus persicae to resist most classes of pesticides, along with the environmental and human health risks associated with these agrochemicals, has necessitated the development of safer and greener solutions to control this agricultural pest. Oligogalacturonides (OGs) are pectin-derived molecules that can be isolated from fruit industry waste. OGs have been shown to efficiently stimulate plant defenses against pathogens such as Pseudomonas syringae and Botrytis cinerea. However, whether OGs confer resistance against phytophagous insects such as aphids remains unknown. Here, we treated Arabidopsis plants with OGs and recorded their effects on the feeding performance and population of M. persicae aphids. We also identified the defense mechanism triggered by OGs in plants through the analysis of gene expression and histological approaches. We found that OG treatments increased their resistance to M. persicae infestation by reducing the offspring number and feeding performance. Furthermore, this enhanced resistance was related to a substantial accumulation of callose and reactive oxygen species and activation of the salicylic acid signaling pathway.

Leaf and Canopy Traits Associated with Stay-Green Expression Are Closely Related to Yield Components of Wheat Genotypes with Contrasting Tolerance to Water Stress.

The onset and rate of senescence influence key agronomical traits, including grain yield (GY). Our objective was to assess the relationships between stay-green and GY in a set of fourteen spring bread wheat (Triticum aestivum L.) genotypes with contrasting tolerance to water stress. Based on leaf chlorophyll content index (Chl) and normalized vegetation index (NDVI) measurements, the senescence dynamics at leaf and canopy levels, respectively, were quantified. Parameters describing the dynamics of senescence were examined in glasshouse and field experiments under well-watered (WW) and water-limited (WL) regimes, and they included the following stay-green traits: maximum NDVI or Chl near to anthesis (NDVImax, Chlmax), the senescence rate (SR, rate), the area under curve (AreaNDVI, AreaChl), and the time from anthesis to 10 (tonset), 50 (t50, X50) and 90% (t90) senescence. Our results revealed that specific stay-green traits were significantly different among genotypes and water regimes in both glasshouse and field experiments. GY was positively correlated with ttotal (0.42), tonset (0.62) and NDVIdif (0.63). Under WL, NDVIdif and NDVImax correlated with GY (0.66-0.58), but only t50 correlated with GY under WW (0.62), indicating that phenotyping of stay-green trait is a useful tool for tracking the dynamics of senescence in WW and WL environments.

Crystal structure and molecular dynamics simulations of a promiscuous ancestor reveal residues and an epistatic interaction involved in substrate binding and catalysis in the ATP-dependent vitamin kinase family members.

Enzymes with hydroxymethylpyrimidine/phosphomethylpyrimidine kinase activity (HMPPK) are essential in the vitamin B1 (thiamine pyrophosphate) biosynthesis and recycling pathways. In contrast, enzymes with pyridoxal kinase activity (PLK) produce pyridoxal phosphate (vitamin B6), an essential cofactor for various biochemical reactions. In the ATP-dependent vitamin kinases family, the members of PLK/HMPPK-like subfamily have both enzymatic activities. It has been proposed that the promiscuous PLK activity of ancestral HMPPK enzymes could have been the starting point for this activity. In earlier work, we reconstructed the ancestral sequences of this family and characterized the substrate specificity of the common ancestor between PLK/HMPPK-like and HMPPK enzymes (AncC). From these studies, the Gln45Met mutation was proposed as a critical event for the PLK activity emergence. Here, we crystallize and determine the AncC structure by X-ray crystallography and assess the role of the Gln45Met mutation by site-directed mutagenesis. Kinetic characterization of this mutant shows a significant increase in the PL affinity. Through molecular dynamics simulation and MM/PBSA calculations some residues, important for substrate interactions and catalysis, were identified in the wild type and in the mutated ancestor. Interestingly, a strong epistatic interaction responsible for the evolutionary pathway of the PLK activity in PLK/HMPPK-like enzymes was revealed. Also, other putative mutations relevant to PLK activity in modern PLK/HMPPK-like enzymes were identified.

UFR2709, a Nicotinic Acetylcholine Receptor Antagonist, Decreases Ethanol Intake in Alcohol-Preferring Rats.

Brain nicotinic acetylcholine receptors (nAChRs), a heterogeneous family of pentameric acetylcholine-gated cation channels, have been suggested as molecular targets for the treatment of alcohol abuse and dependence. Here, we examined the effect of the competitive nAChR antagonist UFR2709 on the alcohol consumption of high-alcohol-drinking UChB rats. UChB rats were given free access to ethanol for 24-h periods in a two-bottle free choice paradigm and their ethanol and water intake were measured. The animals were i.p. injected daily for 17 days with a 10, 5, 2.5, or 1 mg/kg dose of UFR2709. Potential confounding motor effects of UFR2709 were assessed by examining the locomotor activity of animals administered the highest dose of UR2709 tested (10 mg/kg i.p.). UFR2709 reduced ethanol consumption and ethanol preference and increased water consumption in a dose-dependent manner. The most effective dose of UFR2709 was 2.5 mg/kg, which induced a 56% reduction in alcohol consumption. Administration of UFR2709 did not affect the weight or locomotor activity of the rats, suggesting that its effects on alcohol consumption and preference were mediated by specific nAChRs.

The molecular nature of the 17ß-Estradiol binding site in the voltage- and Ca2+-activated K+ (BK) channel ß1 subunit.

The accessory ß1 subunit modulates the Ca2+- and voltage-activated K+ (BK) channel gating properties mainly by increasing its apparent Ca2+ sensitivity. ß1 plays an important role in the modulation of arterial tone and blood pressure by vascular smooth muscle cells (SMCs). 17ß-estradiol (E2) increases the BK channel open probability (Po) in SMCs, through a ß1 subunit-dependent modulatory effect. Here, using molecular modeling, bioinformatics, mutagenesis, and electrophysiology, we identify a cluster of hydrophobic residues in the second transmembrane domain of the ß1 subunit, including the residues W163 and F166, as the binding site for E2. We further show that the increase in Po induced by E2 is associated with a stabilization of the voltage sensor in its active configuration and an increase in the coupling between the voltage sensor activation and pore opening. Since ß1 is a key molecular player in vasoregulation, the findings reported here are of importance in the design of novel drugs able to modulate BK channels.

Trasplante hepático por insuficiencia cardíaca secundaria a telangiectasia hemorrágica hereditaria o enfermedad de Rendu Osler Weber: caso clínico / Liver transplant as treatment for cardiac failure secondary to hereditary hemorrhagic telangiectasia: report of one case

Liver involvement by multiple arterio-venous shunts in hereditary hemorrhagic telangiectasia can lead to severe heart failure. Total hepatectomy with liver transplantation has emerged as a therapeutic option for severe cases where other therapies have failed. We report a 51-year-old male who underwent a liver transplant for this condition, with full cardiac recovery within the first year after receiving the allograft. Nine years after transplantation, he remains with normal functional capacity and normal liver function tests.

Laparoscopy or open surgery for the treatment of hydatid cyst?

The laparoscopic approach has taken a prominent role in the last decades for various surgical conditions, including liver hydatid cyst. However there is controversy about whether it can replace open surgery. Using Epistemonikos database, which is maintained by screening 30 databases, we identified three systematic reviews which together include four relevant studies, all nonrandomized. We combined the evidence using meta-analysis and generated a summary of findings table following the GRADE approach. We concluded it is unclear whether laparoscopy for hepatic hydatid cyst reduces mortality, morbidity or recurrence compared with open surgery because the certainty of the evidence is very low.

En las últimas décadas se ha posicionado el abordaje laparoscópico para diversas patologías quirúrgicas, entre ellas el quiste hidatídico hepático. Sin embargo existe controversia sobre si realmente este puede reemplazar a la cirugía abierta. Utilizando la base de datos Epistemonikos, la cual es mantenida mediante búsquedas en 30 bases de datos, identificamos tres revisiones sistemáticas que en conjunto incluyen cuatro estudios pertinentes, todos no aleatorizados. Realizamos un metanálisis y tablas de resumen de los resultados utilizando el método GRADE. Concluimos que no está claro si el manejo del quiste hidatídico hepático por laparoscopía disminuye la mortalidad, morbilidad o recurrencia en comparación con la cirugía abierta porque la certeza de evidencia es muy baja.

Composition of the SAGA complex in plants and its role in controlling gene expression in response to abiotic stresses.

Protein complexes involved in epigenetic regulation of transcription have evolved as molecular strategies to face environmental stress in plants. SAGA (Spt-Ada-Gcn5 Acetyltransferase) is a transcriptional co-activator complex that regulates numerous cellular processes through the coordination of multiple post-translational histone modifications, including acetylation, deubiquitination, and chromatin recognition. The diverse functions of the SAGA complex involve distinct modules that are highly conserved between yeast, flies, and mammals. In this review, the composition of the SAGA complex in plants is described and its role in gene expression regulation under stress conditions summarized. Some of these proteins are likely involved in the regulation of the inducible expression of genes under light, cold, drought, salt, and iron stress, although the functions of several of its components remain unknown.

A transient receptor potential ion channel in Chlamydomonas shares key features with sensory transduction-associated TRP channels in mammals.

Sensory modalities are essential for navigating through an ever-changing environment. From insects to mammals, transient receptor potential (TRP) channels are known mediators for cellular sensing. Chlamydomonas reinhardtii is a motile single-celled freshwater green alga that is guided by photosensory, mechanosensory, and chemosensory cues. In this type of alga, sensory input is first detected by membrane receptors located in the cell body and then transduced to the beating cilia by membrane depolarization. Although TRP channels seem to be absent in plants, C. reinhardtii possesses genomic sequences encoding TRP proteins. Here, we describe the cloning and characterization of a C. reinhardtii version of a TRP channel sharing key features present in mammalian TRP channels associated with sensory transduction. In silico sequence-structure analysis unveiled the modular design of TRP channels, and electrophysiological experiments conducted on Human Embryonic Kidney-293T cells expressing the Cr-TRP1 clone showed that many of the core functional features of metazoan TRP channels are present in Cr-TRP1, suggesting that basic TRP channel gating characteristics evolved early in the history of eukaryotes.

Emergence of pyridoxal phosphorylation through a promiscuous ancestor during the evolution of hydroxymethyl pyrimidine kinases.

In the family of ATP-dependent vitamin kinases, several bifunctional enzymes that phosphorylate hydroxymethyl pyrimidine (HMP) and pyridoxal (PL) have been described besides enzymes specific towards HMP. To determine how bifunctionality emerged, we reconstructed the sequence of three ancestors of HMP kinases, experimentally resurrected, and assayed the enzymatic activity of their last common ancestor. The latter has ∼ 8-fold higher specificity for HMP due to a glutamine residue (Gln44) that is a key determinant of the specificity towards HMP, although it is capable of phosphorylating both substrates. These results show how a specific enzyme with catalytic promiscuity gave rise to current bifunctional enzymes.