Differential expression of exosomal microRNAs in prefrontal cortices of schizophrenia and bipolar disorder patients

Exosomes are cellular secretory vesicles containing microRNAs (miRNAs). Once secreted, exosomes are able to attach to recipient cells and release miRNAs potentially modulating the function of the recipient cell. We hypothesized that exosomal miRNA expression in brains of patients diagnosed with schizophrenia (SZ) and bipolar disorder (BD) might differ from controls, reflecting either disease-specific or common aberrations in SZ and BD patients. The sources of the analyzed samples included McLean 66 Cohort Collection (Harvard Brain Tissue Resource Center), BrainNet Europe II (BNE, a consortium of 18 brain banks across Europe) and Boston Medical Center (BMC). Exosomal miRNAs from frozen postmortem prefrontal cortices with well-preserved RNA were isolated and submitted to profiling by Luminex FLEXMAP 3D microfluidic device. Multiple statistical analyses of microarray data suggested that certain exosomal miRNAs were differentially expressed in SZ and BD subjects in comparison to controls. RT-PCR validation confirmed that two miRNAs, miR-497 in SZ samples and miR-29c in BD samples, have significantly increased expression when compared to control samples. These results warrant future studies to evaluate the potential of exosome-derived miRNAs to serve as biomarkers of SZ and BD

A structured loop modulates coupling between the substrate-binding and dimerization domains in the multidrug resistance transporter EmrE.

Secondary active transporters undergo large conformational changes to facilitate the efflux of substrates across the lipid bilayer. Among the smallest known transport proteins are members of the small multidrug resistance (SMR) family that are composed of four transmembrane (TM) domains and assemble into dimers. An unanswered question in the SMR field is how the dimerization domain (TM4) is coupled with the substrate-binding chamber (TM1-3). To provide insight for this essential aspect of ion-coupled transport, we carried out a structure-function study on the SMR protein EmrE using solid-state NMR spectroscopy in lipid bilayers and resistance assays in Escherichia coli. The chemical shifts for EmrE were consistent with β-strand secondary structure for the loop connecting TM3 and TM4. Based on these structural results, EmrE mutants were created to ascertain whether a specific loop length and composition were necessary for function. A linker encompassing six extra Gly residues relative to wild-type EmrE failed to give resistance; however, the number of residues in the loop was not the only criterion for a functional efflux pump. Replacement of the central hydrophobic residue with Gly (L83G) also conferred no ethidium resistance phenotype, which supported the conclusion that the structure and length of the loop were both essential for ion-coupled transport. Taken together with a bioinformatics analysis, a structured linker is likely conserved across the SMR family to play an active role in mediating the conformational switch between inward-open and outward-open states necessary for drug efflux. These findings underscore the important role loops can play in mediating efflux

Assessing Interactions Between a Polytopic Membrane Protein and Lipid Bilayers Using Differential Scanning Calorimetry and Solid-State NMR

It is known that the lipid composition within a cellular membrane can influence membrane protein structure and function. In this Article, we investigated how structural changes to a membrane protein upon substrate binding can impact the lipid bilayer. To carry out this study, we reconstituted the secondary active drug transporter EmrE into a variety of phospholipid bilayers varying in headgroup and chain length and carried out differential scanning calorimetry (DSC) and solid-state NMR experiments. The DSC results revealed a difference in cooperativity of the lipid phase transition for drug-free EmrE protonated at glutamic acid 14 (i.e., proton-loaded form) and the tetraphenylphosphonium (TPP⁺) bound form of the protein (i.e., drug-loaded form). To complement these findings, we acquired magic-angle-spinning (MAS) spectra in the presence and absence of TPP⁺ by directly probing the phospholipid headgroup using ³¹P NMR. These spectra showed a reduction in lipid line widths around the main phase transition for samples where EmrE was bound to TPP⁺ compared to the drug free form. Finally, we collected oriented solid-state NMR spectra on isotopically enriched EmrE that displayed chemical shift perturbations to both transmembrane and loop residues upon TPP⁺ binding. All of these results prompt us to propose a mechanism whereby substrate-induced changes to the structural dynamics of EmrE alters the surrounding lipids within the bilayer

Intrinsic Conformational Plasticity of Native EmrE Provides a Pathway for Multidrug Resistance

EmrE is a multidrug resistance efflux pump with specificity to a wide range of antibiotics and antiseptics. To obtain atomic-scale insight into the attributes of the native state that encodes the broad specificity, we used a hybrid of solution and solid-state NMR methods in lipid bilayers and bicelles. Our results indicate that the native EmrE dimer oscillates between inward and outward facing structural conformations at an exchange rate (<i>k</i>_ex) of ∼300 s^–1 at 37 °C (millisecond motions), which is ∼50-fold faster relative to the tetra­phenyl­phospho­nium (TPP⁺) substrate-bound form of the protein. These observables provide quantitative evidence that the rate-limiting step in the TPP⁺ transport cycle is not the outward–inward conformational change in the absence of drug. In addition, using differential scanning calorimetry, we found that the width of the gel-to-liquid crystalline phase transition was 2 °C broader in the absence of the TPP⁺ substrate versus its presence, which suggested that changes in transporter dynamics can impact the phase properties of the membrane. Interestingly, experiments with cross-linked EmrE showed that the millisecond inward-open to outward-open dynamics was not the culprit of the broadening. Instead, the calorimetry and NMR data supported the conclusion that faster time scale structural dynamics (nanosecond–microsecond) were the source and therefore impart the conformationally plastic character of native EmrE capable of binding structurally diverse substrates. These findings provide a clear example how differences in membrane protein transporter structural dynamics between drug-free and bound states can have a direct impact on the physical properties of the lipid bilayer in an allosteric fashion

Evaluation of Communication and Safety Behaviors During Hospital-Wide Code Response Simulation

INTRODUCTION: To understand the baseline quality of team communication behaviors at our organization, we implemented institution-wide simulation training and measured the performance of safety behaviors of ad hoc teams in emergent situations. METHODS: Clinicians participated in 2 interprofessional video-recorded simulation scenarios, each followed by debriefing. Using a standardized evaluation instrument, 2 reviewers independently evaluated the presence or absence of desired team safety behaviors, including escalating care, sharing a mental model, establishing leadership, thinking out loud, and identifying roles and responsibilities. We also scored the quality of sharing the mental model, closed-loop communication, and overall team performance on a 7-point scale. Discordant reviews were resolved with scoring by an additional reviewer. RESULTS: A total of 1404 clinicians participated in 398 simulation scenarios, resulting in 257 usable videos. Overall, teams exhibited desired behaviors at the following frequencies: escalating care, 85%; sharing mental models, 66%; verbally establishing leadership, 6%; thinking out loud, 87%; and identifying roles and responsibilities, 27%. Across all reviews, the quality of the graded behaviors (of 7 points) was 2.8 for shared mental models, 3.3 for closed-loop communication, and 3.2 for overall team performance. CONCLUSIONS: In a simulation setting with ad hoc teams, there was variable performance on completing safety behaviors and only a fair quality of graded communication behaviors. These results establish a baseline assessment of communication and teamwork behaviors and will guide future quality improvement interventions

Evaluation of Communication and Safety Behaviors During Hospital-Wide Code Response Simulation

INTRODUCTION: To understand the baseline quality of team communication behaviors at our organization, we implemented institution-wide simulation training and measured the performance of safety behaviors of ad hoc teams in emergent situations. METHODS: Clinicians participated in 2 interprofessional video-recorded simulation scenarios, each followed by debriefing. Using a standardized evaluation instrument, 2 reviewers independently evaluated the presence or absence of desired team safety behaviors, including escalating care, sharing a mental model, establishing leadership, thinking out loud, and identifying roles and responsibilities. We also scored the quality of sharing the mental model, closed-loop communication, and overall team performance on a 7-point scale. Discordant reviews were resolved with scoring by an additional reviewer. RESULTS: A total of 1404 clinicians participated in 398 simulation scenarios, resulting in 257 usable videos. Overall, teams exhibited desired behaviors at the following frequencies: escalating care, 85%; sharing mental models, 66%; verbally establishing leadership, 6%; thinking out loud, 87%; and identifying roles and responsibilities, 27%. Across all reviews, the quality of the graded behaviors (of 7 points) was 2.8 for shared mental models, 3.3 for closed-loop communication, and 3.2 for overall team performance. CONCLUSIONS: In a simulation setting with ad hoc teams, there was variable performance on completing safety behaviors and only a fair quality of graded communication behaviors. These results establish a baseline assessment of communication and teamwork behaviors and will guide future quality improvement interventions

Characterization of exosome-containing pellets from human brain tissue.

<p>Electron microscopy of exosomal extractions from BA9 cortices demonstrates the presence of microvesicles (∼70–100 nm in diameter). Upon immuno-gold labeling procedure with antibodies against CD63 (A; additional negative staining highlights membrane of the vesicle) and GAPDH (B), the microvesicles reveal the presence of exosome-associated antigens. Bars indicate 100 nm. Comparison of exosomal extraction procedure products from BA9 cortices and H4 cell-culture reveals similar outcomes in Western blot. Supernatant of BA9 exosome-containing pellets (lane 1), supernatant of H4 exosome-containing pellets (lane 2), BA9 exosome-containing pellets reconstituted in PBS (lane 3), and of H4 exosome-containing pellets reconstituted in PBS (lane 4), show robust presence of exosomal marker flotillin-2 in the pellets, but not in the supernatants (C).</p

Hierarchical clustering analysis of top 21 ranked miRNAs from FDR analysis.

<p>Correlation coefficient (cc) was generated to assess the relationship between the expression values of each sample and the rest of the samples (see Methods). The coefficient is 1 if their expression profiles are highly similar and 0 if their expression profiles are highly divergent. The clustering graph is built so that the samples with similar expression patterns are clustered at the bottom while more differential patterns are at the top of the graph.</p