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The highly conserved Hsp90 chaperones control stability and activity of many essential signaling and regulatory proteins including many protein kinases, E3 ligases and transcription factors. Thereby, Hsp90s couple cellular homeostasis of the proteome to cell fate decisions. High-throughput mass spectrometry revealed 178 and 169 posttranslational modifications (PTMs) for human cytosolic Hsp90α and Hsp90β, but for only a few of the modifications the physiological consequences are investigated in some detail. In this study, we explored the suitability of the yeast model system for the identification of key regulatory residues in human Hsp90α. Replacement of three tyrosine residues known to be phosphorylated by phosphomimetic glutamate and by non-phosphorylatable phenylalanine individually and in combination influenced yeast growth and the maturation of 7 different Hsp90 clients in distinct ways. Furthermore, wild-type and mutant Hsp90 differed in their ability to stabilize known clients when expressed in HepG2 HSP90AA1 -/- cells. The purified mutant proteins differed in their interaction with the cochaperones Aha1, Cdc37, Hop and p23 and in their support of the maturation of glucocorticoid receptor ligand binding domain in vitro. In vivo and in vitro data correspond well to each other confirming that the yeast system is suitable for the identification of key regulatory sites in human Hsp90s. Our findings indicate that even closely related clients are affected differently by the amino acid replacements in the investigated positions, suggesting that PTMs could bias Hsp90s client specificity., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

α-Synuclein is an intrinsically disordered protein that adopts an α-helical structure upon binding to the negatively charged lipid membrane. Binding-induced conformational change of α-synuclein plays a crucial role in the regulation of synaptic plasticity. In this work, we utilized the fluorescence depolarization kinetics methodology to gain the site-specific dynamical insights into the membrane-bound α-synuclein. We took advantage of the nonoccurrence of Cys in α-synuclein and created single-Cys variants at different sites for us to be able to label it with a thiol-active fluorophore. Our fluorescence depolarization results reveal the presence of three dynamically distinct types of motions of α-synuclein on POPG (1-palmitoyl-2-oleoyl- sn -glycero-3-phospho-(1'- rac -glycerol)) small unilamellar vesicles (SUVs): (i) the (local) wobbling-in-cone motion of the fluorophore on the subnanosecond timescale, (ii) the backbone segmental mobility on the nanosecond timescale, and (iii) a slow depolarization component with a characteristic long rotational correlation time (∼60 ns) that is independent of the residue position. This characteristic timescale could potentially arise due to global tumbling of the protein-membrane complex, the global reorientation of only the protein within the membrane, and/or the translation diffusion of the protein on the curved membrane surface that could result in fluorescence depolarization due to the angular displacement of the transition dipole. In order to discern the molecular origin of the characteristic long rotational correlation time, we then carried our depolarization experiments varying the curvature of the membrane and varying the binding affinity by changing the lipid headgroup. These experiments revealed that the long rotational correlation time primarily arises due to the translational diffusion of α-synuclein on the curved membrane surface with a diffusion coefficient of ∼8.7 × 10 -10 m 2 /s. The site-specific fluorescence depolarization methodology will find broad application in quantifying diffusion of a wide range of membrane-associated proteins involved in functions and diseases.

Context: Laryngoscopy and endotracheal intubation lead to strong sympathetic response which may precipitate arrhythmias, myocardial ischemia and cerebrovascular accidents in patients with preexisting cardiovascular disease., Aims: This study was aimed to compare the effect of dexmedetomidine and esmolol on hemodynamic response to laryngoscopy and endotracheal intubation in patients undergoing elective surgery under general anesthesia., Settings and Design: This was a prospective, randomized controlled double-blinded study., Materials and Methods: A total of ninety patients were selected and randomized into three groups of thirty patients each: Group C received infusion of 20 mL 0.9% normal saline (NS) over 10 min, Group D received infusion of dexmedetomidine 1 μg/kg diluted in 20 mL NS over 10 min, and Group E received infusion of esmolol 1.5 mg/kg diluted in 20 mL NS over 10 min. Three minutes after the completion of infusion, patients were induced with general anesthesia. Baseline parameters such as heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial blood pressure (MAP), and rate pressure product (RPP) were recorded before administration of study drugs and at 1, 3, 5, 7, and 10 min after intubation., Statistical Analysis Used: One-way ANOVA was used for comparison among the groups and unpaired t -test was used for comparison within the groups along with Tukey's test for post test analysis., Results: Mean HR, SBP, DBP, MAP, and RPP values remained significantly lower in Group D than that of Group C and Group E at all time intervals up to 10 min after intubation., Conclusions: Both dexmedetomidine and esmolol suppressed the hemodynamic response to intubation when compared to control group, but dexmedetomidine is more effective than esmolol in maintaining hemodynamic stability following laryngoscopy and intubation., Competing Interests: There are no conflicts of interest.

Perturbations in molecular signaling pathways are a result of genetic or epigenetic alterations, which may lead to malignant transformation of cells. Despite cellular robustness, specific genetic or epigenetic changes of any gene can trigger a cascade of failures, which result in the malfunctioning of cell signaling pathways and lead to cancer phenotypes. The extent of cellular robustness has a link with the architecture of the network such as feedback and feedforward loops. Perturbation in components within feedback loops causes a transition from a regulated to a persistently activated state and results in uncontrolled cell growth. This work represents the mathematical and quantitative modeling of ERK, PI3K/Akt, and Wnt/β-catenin signaling crosstalk to show the dynamics of signaling responses during genetic and epigenetic changes in cancer. ERK, PI3K/Akt, and Wnt/β-catenin signaling crosstalk networks include both intra and inter-pathway feedback loops which function in a controlled fashion in a healthy cell. Our results show that cancerous perturbations of components such as EGFR, Ras, B-Raf, PTEN, and components of the destruction complex cause extreme fragility in the network and constitutively activate inter-pathway positive feedback loops. We observed that the aberrant signaling response due to the failure of specific network components is transmitted throughout the network via crosstalk, generating an additive effect on cancer growth and proliferation.

Background and Aims: Dexamethasone has a powerful anti-inflammatory action with significant analgesic benefits. The aim of this study was to compare the efficacy of dexamethasone administered through intravenous (IV) and caudal route on post-operative analgesia in paediatric inguinal herniotomy patients., Methods: One hundred and five paediatric patients undergoing inguinal herniotomy were included and divided into three groups. Each patient received a single caudal dose of ropivacaine 0.15%, 1.5 mL/kg combined with either corresponding volume of normal saline (Group 1) or caudal dexamethasone 0.1 mg/kg (Group 2) or IV dexamethasone 0.5 mg/kg (Group 3). Baseline, intra- and post-operative haemodynamic parameters, pain scores, time to rescue analgesia, total analgesic consumption and adverse effects were evaluated for 24 h after surgery. Unpaired Student's t -test and analysis of variance were applied for quantitative data and Chi-square test for qualitative data. Time to first analgesic administration was analysed by Kaplan-Meier survival analysis and log-rank test., Results: Duration of analgesia was significantly longer ( P < 0.001), and total consumption of analgesics was significantly lower ( P < 0.001) in Group II and III compared to Group I. The incidence of nausea and vomiting was higher in Group I (31.4%) compared to Group II and III (8.6%)., Conclusions: Addition of dexamethasone both caudally or intravenously as an adjuvant to caudal 0.15% ropivacaine significantly reduced the intensity of post-operative pain and prolonged the duration of post-operative analgesia with the significant advantage of caudal over IV route., Competing Interests: There are no conflicts of interest.