BackgroundIncreased levels of the pathogenic amyloid β-peptide (Aβ), released from its precursor by the transmembrane protease γ-secretase, are found in Alzheimer disease (AD) brains. Interestingly, monoamine oxidase B (MAO-B) activity is also increased in AD brain, but its role in AD pathogenesis is not known. Recent neuroimaging studies have shown that the increased MAO-B expression in AD brain starts several years before the onset of the disease. Here, we show a potential connection between MAO-B, γ-secretase and Aβ in neurons.MethodsMAO-B immunohistochemistry was performed on postmortem human brain. Affinity purification of γ-secretase followed by mass spectrometry was used for unbiased identification of γ-secretase-associated proteins. The association of MAO-B with γ-secretase was studied by coimmunoprecipitation from brain homogenate, and by in-situ proximity ligation assay (PLA) in neurons as well as mouse and human brain sections. The effect of MAO-B on Aβ production and Notch processing in cell cultures was analyzed by siRNA silencing or overexpression experiments followed by ELISA, western blot or FRET analysis. Methodology for measuring relative intraneuronal MAO-B and Aβ42 levels in single cells was developed by combining immunocytochemistry and confocal microscopy with quantitative image analysis.ResultsImmunohistochemistry revealed MAO-B staining in neurons in the frontal cortex, hippocampus CA1 and entorhinal cortex in postmortem human brain. Interestingly, the neuronal staining intensity was higher in AD brain than in control brain in these regions. Mass spectrometric data from affinity purified γ-secretase suggested that MAO-B is a γ-secretase-associated protein, which was confirmed by immunoprecipitation and PLA, and a neuronal location of the interaction was shown. Strikingly, intraneuronal Aβ42 levels correlated with MAO-B levels, and siRNA silencing of MAO-B resulted in significantly reduced levels of intraneuronal Aβ42. Furthermore, overexpression of MAO-B enhanced Aβ production.ConclusionsThis study shows that MAO-B levels are increased not only in astrocytes but also in pyramidal neurons in AD brain. The study also suggests that MAO-B regulates Aβ production in neurons via γ-secretase and thereby provides a key to understanding the relationship between MAO-B and AD pathogenesis. Potentially, the γ-secretase/MAO-B association may be a target for reducing Aβ levels using protein–protein interaction breakers.Electronic supplementary materialThe online version of this article (doi:10.1186/s13195-017-0279-1) contains supplementary material, which is available to authorized users.

Rapid replication in vitro implicates distinct populations of misfolded hippocampal 4R TAU protein in accelerated progression of Alzheimer’s disease.

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Although drug compliance is a crucial component of treatment effectiveness in chronic diseases, it has never been evaluated in patients with systemic scleroderma. Therefore, the aim of this descriptive study was to determine the drug compliance rate in systemic scleroderma patients and to identify risk factors for noncompliance in these patients. A cross-sectional observational study was conducted. All patients with systemic scleroderma (n = 41) who visited a rheumatic center and signed an informed consent form were included. Data were obtained during structured interviews with patients and from medical records. The Compliance Questionnaire Rheumatology (CQR) was used to determine patient compliance. The relationships between compliance rate and demographic and clinical characteristics were examined. The mean CQR score was 75 %. Based on a dichotomous rating, only 42 % of the patients achieved a satisfactory compliance rate (≥80 %). No relationships between various demographic and clinical characteristics and CQR score expressed as continuous or dichotomous variables were found. This study represents the first evaluation of drug compliance in patients with systemic scleroderma. Many noncompliant patients were identified, but no common risk factors for noncompliance were discovered. The reasons for noncompliance seem to depend on the personal features of the patients.

Doctors caring for rheumatic patients should focus their efforts on strengthening drug compliance in patients with higher QoL where it seems that lower compliance is more likely.

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Post-translational modifications, including phosphorylation, greatly impact the physiological function of proteins, especially those that are natively unfolded and implicated in many neurodegenerative diseases. However, structural and functional studies of such proteins require fully defined phosphorylation, including those that are not physiological. Thus, the kinases ERK2 and GSK-3β were immobilized to various superparamagnetic beads with carboxylic, aldehyde, Ni, or Co functional groups, with a view to efficiently phosphorylate peptides and proteins in vitro. Full phosphorylation of specific synthetic peptides confirmed that beads were successfully loaded with kinases. Remarkably, enzymes covalently immobilized on carboxylated SeraMag beads remained active upon reuse, with residual activity after 10 uses 99.5 ± 0.34% for GSK-3β and 36.2 ± 2.01% for ERK2. The beads were also used to sequentially phosphorylate recombinant tau, which in vivo is a biomarker of Alzheimer's disease. Thus, a system consisting of two fully active kinases immobilized to magnetic beads is demonstrated for the first time. In comparison to soluble enzymes, the beads are easier to handle, reusable, and thus low-cost. Importantly, these beads are also convenient to remove from reactions to minimize contamination of phosphorylated products or to exchange with other kinases.