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C-reactive protein (CRP) plays a crucial role in the diagnosis and monitoring of the non-specific acute phase response in humans. In contrast, rat CRP (rCRP) is an atypical acute-phase protein that possesses unique features, such as a possible incapacity to trigger the complement system and markedly elevated baseline plasma concentrations. To facilitate in vitro studies on these unique characteristics, obtaining high-quality pure rCRP is essential. Here we explored various strategies for rCRP purification, including direct isolation from rat plasma and recombinant expression in both prokaryotic and eukaryotic systems. Our study optimized the recombinant expression system to enhance the secretion and purification efficiency of rCRP. Compared to traditional purification methods, we present a streamlined and effective approach for the expression and purification of rCRP in the Pichia pastoris system. This refined methodology offers significant improvements in the efficiency and effectiveness of rCRP purification, thereby facilitating further structural and functional studies on rCRP., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Cheng, Tang, Gou, Li, Xu and Zhu.)

C-reactive protein (CRP) is a plasma protein that is evolutionarily conserved, found in both vertebrates and many invertebrates. It is a member of the pentraxin superfamily, characterized by its pentameric structure and calcium-dependent binding to ligands like phosphocholine (PC). In humans and various other species, the plasma concentration of this protein is markedly elevated during inflammatory conditions, establishing it as a prototypical acute phase protein that plays a role in innate immune responses. This feature can also be used clinically to evaluate the severity of inflammation in the organism. Human CRP (huCRP) can exhibit contrasting biological functions due to conformational transitions, while CRP in various species retains conserved protective functions in vivo . The focus of this review will be on the structural traits of CRP, the regulation of its expression, activate complement, and its function in related diseases in vivo ., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Zhou, Tang, Xu and Cheng.)

Pancreatic ductal adenocarcinoma (PDAC) is an uncommon but highly fatal malignancy. Identifying causal metabolite biomarkers offers an opportunity to facilitate effective risk assessment strategies for PDAC. In this study, we performed a two-sample Mendelian randomization (MR) study to characterize the potential causal effects of metabolites in plasma on PDAC risk. Genetic instruments were determined for a total of 506 metabolites from one set of comprehensive genome-wide association studies (GWAS) involving 913 individuals of European ancestry from the INTERVAL/EPIC-Norfolk cohorts. Another set of genetic instruments was developed for 483 metabolites from an independent GWAS conducted with 8299 individuals of European ancestry from the Canadian Longitudinal Study on Aging (CLSA) cohort. We analyzed GWAS data of the Pancreatic Cancer Cohort Consortium (PanScan) and the Pancreatic Cancer Case-Control Consortium (PanC4), comprising 8275 PDAC cases and 6723 controls of European ancestry. The association of metabolites with PDAC risk was assessed using the inverse-variance weighted (IVW) method, and complemented with sensitivity analyses of MR-Egger and MR-PRESSO tests. Potential side effects of targeting the identified metabolites for PDAC intervention were further evaluated by a phenome-wide MR (Phe-MR) analysis. Forty-four unique metabolites were identified to be significantly associated with PDAC risk, of which four top-ranking metabolites (X: 12798, X: 11787, X: 11308 and X: 19141) showed replication evidence when using instruments developed from both two cohorts. Our results highlight novel blood metabolites related to PDAC risk, which may help prioritize metabolic features for PDAC mechanistic research and further evaluation of their potential role in PDAC risk assessment., (© 2023 UICC.)

Effective de-implementation models often include replacement of an ineffective practice with an alternative. We co-developed patient education materials as a replacement strategy for inappropriate post-procedural antibiotics in cardiac device procedures. Lessons learned and developed materials may be used to promote infection prevention in other periprocedural settings., Competing Interests: All authors report no conflicts of interest relevant to this article., (© The Author(s) 2023.)

CpG methylation generally occurs on both DNA strands and is essential for mammalian development and differentiation. Until recently, hemimethylation, in which only one strand is methylated, was considered to be simply a transitory state generated during DNA synthesis. The discovery that a subset of CCCTC-binding factor (CTCF) binding sites is heritably hemimethylated suggests that hemimethylation might have an unknown biological function. Here we show that the binding of CTCF is profoundly altered by which DNA strand is methylated and by the specific CTCF binding motif. CpG methylation on the motif strand can inhibit CTCF binding by up to 7-fold, whereas methylation on the opposite strand can stimulate binding by up to 4-fold. Thus, hemimethylation can alter binding by up to 28-fold in a strand-specific manner. The mechanism for sensing methylation on the opposite strand requires two critical residues, V454 and S364, within CTCF zinc fingers 7 and 4. Similar to methylation, CpG hydroxymethylation on the motif strand can inhibit CTCF binding by up to 4-fold. However, hydroxymethylation on the opposite strand removes the stimulatory effect. Strand-specific methylation states may therefore provide a mechanism to explain the transient and dynamic nature of CTCF-mediated chromatin interactions., (© The Author(s) 2023. Published by Oxford University Press on behalf of Nucleic Acids Research.)

A total of 36 patients with suspected peritoneal dialysis (PD) catheter dysfunction in the First Hospital of China Medical University from June 2020 to August 2022 were included, and five patients with normal PD catheter were also included as the control group. There were 22 males and 19 females, and aged (45±21) years. The volume of rapid-phase drainage in the control and dysfunction groups was (2 086±65) and (1 181±637) ml, and the total drainage time was (15.2±1.3) and (38.3±14.9) min, respectively. The volume of rapid-phase drainage in the dysfunction group was reduced and the total drainage time was longer than that in the control group (both P <0.05). Compared with group with PD catheter migration, the duration of new bag instillation was prolonged, the drainage volume in the rapid-phase was reduced, the total drainage duration was prolonged, and the ultrafiltration volume was decreased in the group with PD catheter obstruction (all P <0.05). The rapid exchange test can provide an early preliminary diagnosis of PD catheter dysfunction and identify the type of catheter dysfunction.

Oxidative stress is preferentially treated as a risk factor for the development and progression of osteoporosis. Corynoline as a component of Corydalis bungeana Turcz presents antioxidative and anti-inflammatory properties. In the present study, the effects of Corynoline on osteoblasts following hydrogen peroxide (H 2 O 2 )-induced injury were evaluated accompanied by the investigation of the molecular mechanisms involved. It was found that Corynoline downregulated the intracellular reactive oxygen species (ROS) generation and restored the osteogenic potential of the disrupted osteoblasts by H 2 O 2 exposure. Furthermore, Corynoline was revealed to activate the Nrf2/HO-1 signaling pathway, while ML385 (an Nrf2 inhibitor) would prevent the Corynoline-mediated positive effects on the disrupted osteoblasts. In terms of the animal experiments, Corynoline treatment contributed to a significantly alleviated bone loss. These findings indicate that Corynoline may significantly attenuate the H 2 O 2 -induced oxidative damage of osteoblasts via the Nrf2/HO-1 signaling pathway, providing novel insights to the development of treatments for osteoporosis induced by oxidative injury., Competing Interests: There were no financial or other conflicts of interest in designing, performing, or drafting this work., (© 2023 The Authors. Food Science & Nutrition published by Wiley Periodicals LLC.)

Background: With rapid economic development, the world's average life expectancy is increasing, leading to the increasing prevalence of osteoporosis worldwide. However, due to the complexity and high cost of dual-energy x-ray absorptiometry (DXA) examination, DXA has not been widely used to diagnose osteoporosis. In addition, studies have shown that the psoas index measured at the third lumbar spine (L3) level is closely related to bone mineral density (BMD) and has an excellent predictive effect on osteoporosis. Therefore, this study developed a variety of machine learning (ML) models based on psoas muscle tissue at the L3 level of unenhanced abdominal computed tomography (CT) to predict osteoporosis., Methods: Medical professionals collected the CT images and the clinical characteristics data of patients over 40 years old who underwent DXA and abdominal CT examination in the Second Affiliated Hospital of Wenzhou Medical University database from January 2017 to January 2021. Using 3D Slicer software based on horizontal CT images of the L3, the specialist delineated three layers of the region of interest (ROI) along the bilateral psoas muscle edges. The PyRadiomics package in Python was used to extract the features of ROI. Then Mann-Whitney U test and the least absolute shrinkage and selection operator (LASSO) algorithm were used to reduce the dimension of the extracted features. Finally, six machine learning models, Gaussian naïve Bayes (GNB), random forest (RF), logistic regression (LR), support vector machines (SVM), Gradient boosting machine (GBM), and Extreme gradient boosting (XGBoost), were applied to train and validate these features to predict osteoporosis., Results: A total of 172 participants met the inclusion and exclusion criteria for the study. 82 participants were enrolled in the osteoporosis group, and 90 were in the non-osteoporosis group. Moreover, the two groups had no significant differences in age, BMI, sex, smoking, drinking, hypertension, and diabetes. Besides, 826 radiomic features were obtained from unenhanced abdominal CT images of osteoporotic and non-osteoporotic patients. Five hundred fifty radiomic features were screened out of 826 by the Mann-Whitney U test. Finally, 16 significant radiomic features were obtained by the LASSO algorithm. These 16 radiomic features were incorporated into six traditional machine learning models (GBM, GNB, LR, RF, SVM, and XGB). All six machine learning models could predict osteoporosis well in the validation set, with the area under the receiver operating characteristic (AUROC) values greater than or equal to 0.8. GBM is more effective in predicting osteoporosis, whose AUROC was 0.86, sensitivity 0.70, specificity 0.92, and accuracy 0.81 in validation sets., Conclusion: We developed six machine learning models to predict osteoporosis based on psoas muscle images of abdominal CT, and the GBM model had the best predictive performance. GBM model can better help clinicians to diagnose osteoporosis and provide timely anti-osteoporosis treatment for patients. In the future, the research team will strive to include participants from multiple institutions to conduct external validation of the ML model of this study., (© 2022. The Author(s).)

Bone metabolism occurs in the entire life of an individual and is required for maintaining skeletal homeostasis. The imbalance between osteogenesis and osteoclastogenesis eventually leads to osteoporosis. Oxidative stress is considered a major cause of bone homeostasis disorder, and relieving excessive oxidative stress in bone mesenchymal stem cells (BMSCs) is a potential treatment strategy for osteoporosis. Carbon monoxide releasing molecule-3 (CORM-3), the classical donor of carbon monoxide (CO), possesses antioxidation, antiapoptosis, and anti-inflammatory properties. In our study, we found that CORM-3 could reduce reactive oxygen species (ROS) accumulation and prevent mitochondrial dysfunction thereby restoring the osteogenic potential of the BMSCs disrupted by hydrogen peroxide (H 2 O 2 ) exposure. The action of CORM-3 was preliminarily considered the consequence of Nrf2/HO-1 axis activation. In addition, CORM-3 inhibited osteoclast formation in mouse primary bone marrow monocytes (BMMs) by inhibiting H 2 O 2 -induced polarization of M1 macrophages and endowing macrophages with M2 polarizating ability. Rat models further demonstrated that CORM-3 treatment could restore bone mass and enhance the expression of Nrf2 and osteogenic markers in the distal femurs. In summary, CORM-3 is a potential therapeutic agent for the treatment of osteoporosis., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2022 Chen Jin et al.)

Background: Membranous nephropathy (MN) is a common pathological phenotype for adult nephrotic syndrome (NS). The occurrence of MN is increasing across China, but diagnostic methods for MN still rely on kidney biopsy and PLA2R and THSD7A detection in plasma and kidney tissue, and there has been no new biomarker for MN discovered since 2014. Immune infiltration status in MN patients suffers from the dearth of associated studies. In the present study, we aimed to find new bio-markers for MN and evaluate the role of immune cells infiltration in MN pathology., Methods: We downloaded MN expression profile from the Gene Expression Omnibus database and used R-project to screen differentially expressed genes (DEGs) and performed functional correlation analysis. Least absolute shrinkage and selection operator (LASSO) logistic regression and Radom Forest algorithms were used to screen and verify the bio-markers of MN. Finally, CIBERSORT was used to evaluate the infiltration of immune cells in MN tissues., Results: A total of 463 DEGs were screened from the MN tissue in this study. ETS2 was identified as bio-marker for MN. The CIBERSORT results showed that there were statistical differences in monocytes, plasma cells, regulatory T cells, and memory B cells. In addition, ETS2 was positively related to monocytes, M1 phase macrophages, and neutrophils and negatively correlated to plasma cells, CD4+ T memory cells, M2 macrophages, CD8+ T cells, memory B cells, and resting mast cells., Conclusion: (1) Machine learning algorithms reveals Ets2 as a novel target for membranous nephropathy patients. (2) Immune infiltration plays an important part in membranous nephropathy. (3) Ets2 expression is related to immune cells infiltration., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Wan, Xu, Tian, Guo, Li and Yao.)

Background: Despite a strong evidence base and clinical guidelines specifically recommending against prolonged post-procedural antimicrobial use, studies indicate that the practice is common following cardiac device procedures. Formative evaluations conducted by the study team suggest that inappropriate antimicrobial use may be driven by information silos that drive provider belief that antimicrobials are not harmful, in part due to lack of complete feedback about all types of clinical outcomes. De-implementation is recognized as an important area of research that can lead to reductions in unnecessary, wasteful, or harmful practices, such as excess antimicrobial use following cardiac device procedures; however, investigations into strategies that lead to successful de-implementation are limited. The overarching hypothesis to be tested in this trial is that a bundle of implementation strategies that includes audit and feedback about direct patient harms caused by inappropriate prescribing can lead to successful de-implementation of guideline-discordant care., Methods: We propose a hybrid type III effectiveness-implementation stepped-wedge intervention trial at three high-volume, high-complexity VA medical centers. The main study intervention (an informatics-based, real-time audit-and-feedback tool) was developed based on learning/unlearning theory and formative evaluations and guided by the integrated-Promoting Action on Research Implementation in Health Services (i-PARIHS) Framework. Elements of the bundled and multifaceted implementation strategy to promote appropriate prescribing will include audit-and-feedback reports that include information about antibiotic harms, stakeholder engagement, patient and provider education, identification of local champions, and blended facilitation. The primary study outcome is adoption of evidence-based practice (de-implementation of inappropriate antimicrobial use). Clinical outcomes (cardiac device infections, acute kidney injuries and Clostridioides difficile infections) are secondary. Qualitative interviews will assess relevant implementation outcomes (acceptability, adoption, fidelity, feasibility)., Discussion: De-implementation theory suggests that factors that may have a particularly strong influence on de-implementation include strength of the underlying evidence, the complexity of the intervention, and patient and provider anxiety and fear about changing an established practice. This study will assess whether a multifaceted intervention mapped to identified de-implementation barriers leads to measurable improvements in provision of guideline-concordant antimicrobial use. Findings will improve understanding about factors that impact successful or unsuccessful de-implementation of harmful or wasteful healthcare practices., Trial Registration: ClinicalTrials.gov NCT05020418., (© 2022. The Author(s).)

Pulmonary embolism (PE) is a common and potentially lethal form of venous thromboembolic disease in ICU patients. A limited number of risk factors have been associated with PE in ICU patients. In this study, we aimed to screen the independent risk factors of PE in ICU patients that can be used to evaluate the patient's condition and provide targeted treatment. We performed a retrospective cohort study using a freely accessible critical care database Medical Information Mart for Intensive Care (MIMIC)-III. The ICU patients were divided into two groups based on the incidence of PE. Finally, 9871 ICU patients were included, among which 204 patients (2.1%) had pulmonary embolism. During the multivariate logistic regression analysis, sepsis, hospital&#95;LOS (the length of stay in hospital), type of admission, tumor, APTT (activated partial thromboplastin time) and platelet were independent risk factors for patients for PE in ICU, with OR values of 1.471 (95%CI 1.001-2.162), 1.001 (95%CI 1.001-1.001), 3.745 (95%CI 2.187-6.414), 1.709 (95%CI 1.247-2.341), 1.014 (95%CI 1.010-1.017) and 1.002 (95%CI 1.001-1.003) ( P s  < 0.05). ROC curve analysis showed that the composite indicator had a higher predictive value for ICU patients with PE, with a ROC area under the curve (AUC) of 0.743 (95%CI 0.710 -0.776, p  < 0.001). Finally, sepsis, tumor, platelet count, length of stay in the hospital, emergency admission and APTT were independent predictors of PE in ICU patients.

Glucocorticoid-induced osteonecrosis of the femoral head (GIONFH) is a serious complication after long-term or excess administration of clinical glucocorticoids intervention, and the pathogenic mechanisms underlying have not been clarified yet. Oxidative stress is considered as a major cause of bone homeostasis disorder. This study is aimed to explore the potential relevance between SIRT3 and GIONFH, as well as the effect of resveratrol, which has been reported for its role in SIRT3 activation, on dexamethasone-induced oxidative stress and mitochondrial compromise in bone marrow stem cells (BMSCs). In this study, our data showed that SIRT3 level was declined in GIONFH rat femoral head, corresponding to a resultant decrease of SIRT3 expression in dexamethasone-treated BMSCs in vitro. We also found that dexamethasone could result in oxidative injury in BMSCs, and resveratrol treatment reduced this deleterious effect via a SIRT3-dependent manner. Moreover, our results demonstrated that rewarding effect of resveratrol on BMSCs osteogenic differentiation was via activation of AMPK/PGC-1α/SIRT3 axis. Meanwhile, resveratrol administration prevented the occurrence of GIONFH, enhanced SIRT3 expression and reduced oxidative level in GIONFH model rats. Therefore, our study provides basic evidence that SIRT3 may be a promising therapeutic target for GIONFH treatment and resveratrol could be an ideal agent for clinical uses., (Copyright © 2021 Elsevier Inc. All rights reserved.)

This study is to determine the role of the fractional CO2 laser in topical drug delivery and the impact of local immune responses. Experimental rabbit nails were treated with fractionated CO2 laser at varied fluencies of 20 mJ, 25 mJ, and 30 mJ and half of which were coated with rhodamine B (RhB). Histological examination was performed by hematoxylin and eosin staining; the penetration of RhB was assessed by the use of confocal laser scanning microscopy; and the expressions of IFN-γ and IL-4 mRNA in situ were detected by means of qPCR at 12 h, 24 h, 3 days, and 7 days post-laser irritation. The fractional CO2 laser could generate microscopic treatment zones in nail plates, and the depths of these micropores as well as the permeation of RhB in nails increased significantly in an energy-dependent manner. Importantly, the laser irritation led an upregulation of local IFN-γ mRNA expression accompanied by a downregulation of IL-4 mRNA expression. The ultrapulsed ablative fractionated CO2 laser may assist topical drug delivery, and may drive stronger local Th1 responses due to an imbalance of IFN-γ/IL-4 expressions, suggesting that the combination of ablative fractionated CO2 laser with topical agents would be an effective option for the treatment of onychomycosis., (© 2021. The Author(s), under exclusive licence to Springer-Verlag London Ltd. part of Springer Nature.)

Background: There are no studies on the use of roxadustat in patients on regular peritoneal dialysis in China., Aim: To observe the efficacy and safety of roxadustat in treating renal anaemia in peritoneal dialysis patients., Methods: Patients with renal anaemia who were regularly followed at the Peritoneal Dialysis Center of the First Affiliated Hospital of China Medical University from November 1, 2019 to June 30, 2020 were selected. A before-and-after self-control design was performed to retrospectively analyse the treatment effects on anaemia in patients treated with recombinant human erythropoietin (EPO) and roxadustat., Results: A total of 31 patients with renal anaemia on long-term peritoneal dialysis treated with roxadustat were included. Haemoglobin (Hb) levels were maintained or increased in all patients (100%), and no patients had a decrease in Hb compared with the previous phase. Patients had a mean Hb of 86.2 ± 14.8 g/L with Hb compliance (Hb ≥ 110 g/L) of 16.1% during the EPO phase and a mean Hb of 112.4 ± 18.5 g/L with Hb compliance of 67.7% during the roxadustat phase. No major adverse cardiovascular events occurred in any patient., Conclusion: The application of roxadustat in peritoneal dialysis patients with renal anaemia can effectively improve the Hb compliance rate., Competing Interests: Conflict-of-interest statement: All authors have no conflicts of interest related to the manuscript., (©The Author(s) 2021. Published by Baishideng Publishing Group Inc. All rights reserved.)

Objective: To evaluate the efficacy and safety profile of ixazomib/lenalidomide/dexamethasone (IRd) in Chinese patients with relapsed/refractory multiple myeloma (MM) . Methods: This study comprising 14 medical centers in China included patients with relapsed/refractory MM who received at least. Ixazomib at an initial oral dose of 4 mg was administered. Seven patients had dose adjustment to 3 mg at the time of first dose. The lenalidomide doses were adjusted according to creatinine clearance rate. The efficacy and safety were evaluated every cycle. Results: In the study cohort of 74 patients, the median age was 65 years and 11 (14.9% ) patients received over three lines of therapy. Overall response rate (ORR) was 54.1% (40/74) , and 7 (9.5% ) , 14 (18.9% ) , and 19 (25.7% ) patients achieved stringent complete response or complete response, very good partial response, and partial response, respectively. The median progression-free survival and overall survival were 9.9 and 20 months, respectively. The median time to response was 1 month. The efficacy and survival outcome were similar to those reported in the Tourmaline-MM1 China Continuous Study. The ORR of patients refractory to bortezomib, lenalidomide, and bortezomib plus lenalidomide were 52.0% (13/25) , 57.1% (4/7) , and 33.3% (6/18) , respectively. The rate of grade 3-4 adverse events was 36.5% (27/74) . Common hematological toxicities were anemia, thrombocytopenia, lymphopenia, and neutropenia. Common non-hematological toxicities were fatigue, gastrointestinal symptoms, and infections. Two cases of grade 3 peripheral neuropathy were reported. The patients eligible for the Tourmaline-MM1 China Continuous Study had a higher ORR than the ineligible patients [77.8% (14/18) vs 46.4% (26/56) , P =0.020]. There was no difference in the rate of grade 3-4 adverse events [33.3% (6/18) vs 37.5% (21/56) , P =0.749]. Conclusion: The IRd regimen had good efficacy and acceptable toxicity in Chinese patients with relapsed/refractory MM.

Adenosine monophosphate (AMP)-activated protein kinase (AMPK) regulates metabolism in response to the cellular energy states. Under energy stress, AMP stabilizes the active AMPK conformation, in which the kinase activation loop (AL) is protected from protein phosphatases, thus keeping the AL in its active, phosphorylated state. At low AMP:ATP (adenosine triphosphate) ratios, ATP inhibits AMPK by increasing AL dynamics and accessibility. We developed conformation-specific antibodies to trap ATP-bound AMPK in a fully inactive, dynamic state and determined its structure at 3.5-angstrom resolution using cryo-electron microscopy. A 180° rotation and 100-angstrom displacement of the kinase domain fully exposes the AL. On the basis of the structure and supporting biophysical data, we propose a multistep mechanism explaining how adenine nucleotides and pharmacological agonists modulate AMPK activity by altering AL phosphorylation and accessibility., (Copyright © 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Parasites can cause respiratory symptoms through focal or diffuse lung involvement, depending on the location of the parasite and the host's immune response. Pulmonary involvement can be a major feature of some parasitic infections or a complication during transpulmonary larval migration. Parasites should be included in the differential diagnosis of common lung diseases, especially in the presence of peripheral eosinophilia or extrapulmonary symptoms (abdominal pain, diarrhea, jaundice, skin lesions)., Competing Interests: Disclosure The authors have nothing to disclose., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Two new compounds, including a diterpenoid glycoside ( 1 ) and a triterpenoid glycoside ( 6 ), along with six known compounds were isolated from Clinopodium chinense . The structures of the new compounds were determined on basis of extensive spectral analysis and chemical method. Compounds 1 - 8 were evaluated for their insulin resistance effect and cytotoxic activity against the A549 and HepG2 cancer cell lines. None of the compounds were cytotoxic (IC 50  > 100 μM), while compounds 1 - 3 and 5 showed the activity of ameliorating insulin resistance in HepG2.

Aims: Pathological vascular calcification (VC), a major risk factor for cardiovascular mortality, is a highly prevalent finding in patients with chronic kidney disease (CKD). We previously analyzed several pathways protecting against high phosphate-induced VC through induction of autophagy. Here, we explored how O-GlcNAc transferase (OGT) affected high phosphate-induced VC of CKD though mediation of autophagy., Main Methods: In the rats with CKD induced by 5/6 nephrectomy, the VC process was accelerated by a high phosphate diet. The calcification of vascular smooth muscle cells (VSMCs) was induced by high phosphate treatment. We then experimentally tested the effect of OGT on high phosphate-induced VC by conducting loss-of-function experiments. Co-immunoprecipitation and GST pull-down assays were performed to evaluate interaction between OGT and Yes-associated protein (YAP). In mechanistic studies of this pathway, we measured autophagy protein expression and autophagosome formation, as well as calcium deposition and calcium content in VSMCs and in vivo in response to altered expression of OGT and/or YAP., Key Findings: OGT was up-regulated in high phosphate-induced VC models in vitro and in vivo. High phosphate-induced calcification in the rat aorta and VSMCs were suppressed by OGT silencing. OGT promoted the glycosylation of YAP to enhance its stability. Importantly, over-expressing YAP reduced autophagy and OGT expedited high phosphate-induced VC by inhibiting autophagy through upregulation of YAP., Significance: OGT silencing downregulated YAP to induce autophagy activation, thus suppressing high phosphate-induced VC, which highlighted a promising preventive target against high phosphate-induced VC in CKD., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Unraveling the complex regulatory pathways that mediate the effects of phosphate on vascular smooth muscle cells (VSMCs) may provide novel targets and therapies to limit the destructive effects of vascular calcification (VC) in patients with chronic kidney disease (CKD). Our previous studies have highlighted several signaling networks associated with VSMC autophagy, but the underlying mechanisms remain poorly understood. Thereafter, the current study was performed to characterize the functional relevance of O-linked N-acetylglucosamine (GlcNAc) transferase (OGT) in high phosphate-induced VC in CKD settings. We generated VC models in 5/6 nephrectomized rats in vivo and VSMC calcification models in vitro . Artificial modulation of OGT (knockdown and overexpression) was performed to explore the role of OGT in VSMC autophagy and VC in thoracic aorta, and in vivo experiments were used to substantiate in vitro findings. Mechanistically, co-immunoprecipitation (Co-IP) assay was performed to examine interaction between OGT and kelch like ECH associated protein 1 (KEAP1), and in vivo ubiquitination assay was performed to examine ubiquitination extent of nuclear factor erythroid 2-related factor 2 (NRF2). OGT was highly expressed in high phosphate-induced 5/6 nephrectomized rats and VSMCs. OGT silencing was shown to suppress high phosphate-induced calcification of VSMCs. OGT enhances KEAP1 glycosylation and thereby results in degradation and ubiquitination of NRF2, concurrently inhibiting VSMC autophagy to promote VSMC calcification in 5/6 nephrectomized rats. OGT inhibits VSMC autophagy through the KEAP1/NRF2 axis and thus accelerates high phosphate-induced VC in CKD., (Copyright © 2020 Xu, Du, Sheng, Li, Qiu, Tian and Yao.)

CpG methylation by de novo DNA methyltransferases (DNMTs) 3A and 3B is essential for mammalian development and differentiation and is frequently dysregulated in cancer 1 . These two DNMTs preferentially bind to nucleosomes, yet cannot methylate the DNA wrapped around the nucleosome core 2 , and they favour the methylation of linker DNA at positioned nucleosomes 3,4 . Here we present the cryo-electron microscopy structure of a ternary complex of catalytically competent DNMT3A2, the catalytically inactive accessory subunit DNMT3B3 and a nucleosome core particle flanked by linker DNA. The catalytic-like domain of the accessory DNMT3B3 binds to the acidic patch of the nucleosome core, which orients the binding of DNMT3A2 to the linker DNA. The steric constraints of this arrangement suggest that nucleosomal DNA must be moved relative to the nucleosome core for de novo methylation to occur.

Strongyloidiasis affects an estimated hundreds of millions of people worldwide, with infection possibly persisting for life without appropriate therapy because of the helminth's unique autoinfection cycle. Like other soil-transmitted helminths, because of the environmental conditions required for the life cycle of Strongyloides stercoralis , this parasite is endemic to tropical, subtropical, and temperate countries and areas with inadequate sanitation infrastructure. Given continued poverty and that nearly one in five American homes are lacking proper sanitation systems, many U.S. regions are at risk for intestinal parasites. A central Texas community was chosen as the study site, given previous reports of widespread sanitation failure, degree of poverty, and community willingness to participate. A total of 92 households were surveyed and residents tested for nine intestinal parasites using a multi-parallel quantitative real-time polymerase chain reaction and ELISA serology. From 43 stool samples, 27 (62.8%) tested positive for Blastocystis spp. and one (2.3%) for Giardia lamblia . From 97 serum samples, Strongyloides serology detected 16 (16.5%) positive individuals. These high rates of heterokont and helminthic laboratory findings in a peri-urban central Texas community suggest several key policy implications, including that strongyloidiasis should be added to the Texas notifiable conditions list, that clinical suspicion for this infection should be heightened in the region, and that residents without access to functioning and sustainable sanitation infrastructure should be provided that access as a basic human right and to promote public health.

Drugs selectively targeting CB2 hold promise for treating neurodegenerative disorders, inflammation, and pain while avoiding psychotropic side effects mediated by CB1. The mechanisms underlying CB2 activation and signaling are poorly understood but critical for drug design. Here we report the cryo-EM structure of the human CB2-G i signaling complex bound to the agonist WIN 55,212-2. The 3D structure reveals the binding mode of WIN 55,212-2 and structural determinants for distinguishing CB2 agonists from antagonists, which are supported by a pair of rationally designed agonist and antagonist. Further structural analyses with computational docking results uncover the differences between CB2 and CB1 in receptor activation, ligand recognition, and G i coupling. These findings are expected to facilitate rational structure-based discovery of drugs targeting the cannabinoid system., Competing Interests: Declaration of Interests The authors declare no competing interests., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Formylpeptide receptors (FPRs) as G protein-coupled receptors (GPCRs) can recognize formylpeptides derived from pathogens or host cells to function in host defense and cell clearance. In addition, FPRs, especially FPR2, can also recognize other ligands with a large chemical diversity generated at different stages of inflammation to either promote or resolve inflammation in order to maintain a balanced inflammatory response. The mechanism underlying promiscuous ligand recognition and activation of FPRs is not clear. Here we report a cryo-EM structure of FPR2-G i signaling complex with a peptide agonist. The structure reveals a widely open extracellular region with an amphiphilic environment for ligand binding. Together with computational docking and simulation, the structure suggests a molecular basis for the recognition of formylpeptides and a potential mechanism of receptor activation, and reveals conserved and divergent features in G i coupling. Our results provide a basis for understanding the molecular mechanism of the functional promiscuity of FPRs.

Introduction: Postoperative nausea and vomiting (PONV) is among the most common adverse reactions following anaesthesia and surgery. Recent clinical studies have reported that the average incidence is about 30%, while in patients specifically undergoing neurosurgery, the incidence can be as great as 73%. Studies also suggest that its occurrence increases the risk of intracranial haematoma and haemorrhage. The objective of this study is to evaluate the effectiveness of intradermal thumbtack needle buried Neiguan (pericardium 6 (P6)) point therapy in the prevention of PONV in patients undergoing craniotomy under general anaesthesia., Methods and Analysis: This is a single-centre, three-arm, randomised controlled trial. 180 participants are randomly assigned to either an acupuncture, intradermal thumbtack needle or control group in a 1:1:1 ratio. The P6 of the acupuncture group is punctured at both sides perpendicularly to a depth of 20 mm. Needles are retained for 30 min and stimulated every 10 min to maintain the de qi. The therapy includes two treatments; the acupuncture is administered immediately after and 24 hours after surgery. For the intradermal thumbtack needle group, the intradermal thumbtack needle is quickly inserted into the skin and embedded at P6 acupoints bilaterally. Patients and their families are asked to press the needlepoint with the onset of nausea, vomiting, bloating, pain and other reported discomforts. The needle is replaced after 24 hours. The therapy is administered immediately after and 24 hours after surgery. For the control group, no intervention is carried out. The incidence of PONV within 48 hours after craniotomy across the three groups is observed. Other observations include: (1) assessment of nausea score (severity of nausea) and pain score (visual analogue scale) 0-2, 2-6, 6-24 and 24-48 hours after craniotomy under general anaesthesia; (2) assessment of total rescue antiemetic dosage 0-48 hours after craniotomy under general anaesthesia; (3) length of hospital stay and (4) patient satisfaction score with PONV management. We will perform all statistical analysis following the intention-to-treat principle., Ethics and Dissemination: Ethics approval has been granted by the Bioethics Subcommittee of the West China Hospital, Sichuan University: the approval number is 2018 (number 231). Results will be expected to be published in peer-reviewed journals., Trial Registration Number: ChiCTR1800017173., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2019. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

A family of 4-cyanophenyl-substituted 10 H -phenothiazinylbenzo[ d ]imidazoles with different side chains at the 10-position are prepared and their physical properties are studied. The detailed structure-property research demonstrates that the cold crystallization temperature of ground samples and the emission wavelengths of pristine samples are in good accordance with the packing density, conformation distortion and intermolecular interactions, but emission wavelengths of ground samples are slightly chain-dependent. For benzimidazoles with alkyl chains, longer and more branched chains can produce looser packings, which cause pristine samples to display red-shifted emission and reduced MFC activity. For benzimidazoles with a phenyl chain, the emission wavelengths of both the pristine and the ground samples are remarkably red-shifted. Moreover, the degree of conformation distortion is larger, and the cold crystallization temperature is higher. Interestingly, the homologue with the n -hexyl chain displays an intense ML effect that is mainly attributed to the heavy discharge quantity on largely enhanced discharge areas under force stimuli due to the great fragility of this crystal., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Pathological calcification represents an event that consequently leads to a distinct elevation in the morbidity and mortality of patients with chronic kidney disease (CKD) in addition to strengthening its correlation with hyperphosphatemia. Epigenomic regulation by specific microRNAs (miRNAs) is reported to be involved in ectopic calcification. However, the finer molecular mechanisms governing this event remain unclear. Hence, this study aimed to identify the potential miRNAs involved in vascular calcification (VC) development and progression. Initially, mitochondrial membrane potential (MMP), autophagy-specific markers (LC3II/LC3I and Beclin1) and phenotype-specific markers of osteoblasts (runt-related transcription factor 2 and Msx2) were measured to evaluate autophagy and VC in β-glycerophosphate-induced vascular smooth muscle cells (VSMCs) with either miR-30b restoration or miR-30b knockdown performed in vitro. The VC in vivo was represented by calcified nodule formation in the aorta of the rats undergoing 5/6 nephrectomy followed by a 1.2% phosphorus diet using Alizarin Red staining. SOX9 was verified as the target of miR-30b according to luciferase activity determination. Restoration of miR-30b was revealed to markedly diminish the expression of SOX9 while acting to inhibit activation of the mTOR signaling pathway. Knockdown of miR-30b reduced MMP and autophagy, elevated VC, and suppressed the presence of rapamycin (an inhibitor of the mTOR signaling pathway). In addition, upregulated expression of miR-30b attenuated VC in vivo. Taken together, the key findings of this study identified the inhibitory role of miR-30b in VC, presenting an enhanced understanding of miRNA as a therapeutic target to curtail progressive VC in hyperphosphatemia of CKD., (© 2019 Wiley Periodicals, Inc.)

Cutaneous dirt-adherent disease (CDAD) is a rare psychogenic dermatosis mainly occurring in young Japanese and Chinese women. It mainly occurs on cheeks, forehead, nipple, mammary areola and around mammary areola. To our knowledge, this is the first case of CDAD with the skin lesion of psoriasis rupioides to be reported. In our case, the patient, a 43-year-old Chinese man presented with thick, yellowish-brown adherent crusts on his face with severe painful 6-days duration. Histopathologic image: Parakeratosis, the epidermis demonstrates regular acanthosis with some thinning of the suprapapillary plates, neutrophils exocytosis are noted. As for the histopathologic diagnosis in his right crus, combined with the clinical manifestation of rupioides-shaped crusts, film phenomenon and Auspitz's sign, we considered Psoriasis rupioide., (© 2019 Wiley Periodicals, Inc.)

In the last 10 years, the prevalence, significance, and regulatory mechanisms of vascular calcification (VC) have gained increasing recognition. The aim of this study is to explore the action of WNT8b in the development of phosphate-induced VC through its effect on vascular smooth muscle cells (VSMCs) in vitro by inactivating the Wnt-β-catenin signaling pathway. To explore the effect of WNT8b on the Wnt-β-catenin signaling pathway and VC in vitro, β-glycerophosphate (GP)-induced T/G HA-VSMCs were treated with small interfering RNA against WNT8b (Si-WNT8b), Wnt-β-catenin signaling pathway activator (LiCl) and both, respectively. Reverse transcription quantitative polymerase chain reaction and western blot analysis were used to determine the messenger RNA and protein levels of WNT8b, α-smooth muscle actin (α-SMA), calcification-associated molecules, and molecules related to the Wnt signaling pathway. The TOP/FOP-Flash reporter assay was performed to detect the transcription activity mediated by β-catenin. Si-WNT8b reduced calcium deposition and the activity of alkaline phosphatase (ALP), increased the α-SMA level, and decreased bone morphogenetic protein 2, Pit1, MSX2, and Runt-related transcription factor 2 levels, whereas stimulation of LiCl worsened β-GP-induced calcium deposition, increased the activity of ALP, and reduced the α-SMA expression level. Si-WNT8b reduced the levels of WNT8b, frizzled-4, β-catenin, phospho-GSK-3β (p-GSK-3β), and cyclin-D, whereas it increased the levels of p-β-catenin and GSK-3β, indicating that si-WNT8b could alter the Wnt-β-catenin signaling pathway and thus hamper the VC in T/G HA-VSMC, which was further demonstrated by the TOP/FOP-Flash assay and detection of the β-catenin expression level in the nucleus. Altogether, we conclude that WNT8b knockdown terminates phosphate-induced VC in VSMCs by inhibiting the Wnt-β-catenin signaling pathway., (© 2018 Wiley Periodicals, Inc.)

Frizzled receptors (FZDs) are class-F G-protein-coupled receptors (GPCRs) that function in Wnt signalling and are essential for developing and adult organisms 1,2 . As central mediators in this complex signalling pathway, FZDs serve as gatekeeping proteins both for drug intervention and for the development of probes in basic and in therapeutic research. Here we present an atomic-resolution structure of the human Frizzled 4 receptor (FZD4) transmembrane domain in the absence of a bound ligand. The structure reveals an unusual transmembrane architecture in which helix VI is short and tightly packed, and is distinct from all other GPCR structures reported so far. Within this unique transmembrane fold is an extremely narrow and highly hydrophilic pocket that is not amenable to the binding of traditional GPCR ligands. We show that such a pocket is conserved across all FZDs, which may explain the long-standing difficulties in the development of ligands for these receptors. Molecular dynamics simulations on the microsecond timescale and mutational analysis uncovered two coupled, dynamic kinks located at helix VII that are involved in FZD4 activation. The stability of the structure in its ligand-free form, an unfavourable pocket for ligand binding and the two unusual kinks on helix VII suggest that FZDs may have evolved a novel ligand-recognition and activation mechanism that is distinct from that of other GPCRs.

Two previously undescribed steroidal compounds, 16, 23-epoxy-22, 26-epimino-cholest-22(N), 23, 25(26)-trien-3β-ol-3-O-β-D-glucopyranosyl-(1→2)-β-D-glucopyranosyl-(1→4)-β-D-galactopyranoside (1) and 26-O-β-D-glucopyranosyl-(25R)-5α-furost-20(22)-en-3β, 26-diol (2), together with 7 known ones including 26-O-β-D-glucopyranosyl-(25R)-5, 20(22)-dien-furost-3β, 26-diol (3), (25R)-5-en-spirost-3β-ol-O-β-D-glucopyranosyl-(1→4)-[α-L-rhmanopyranosyl-(1→2)]-β-D-galactopyranoside (4), funkioside D (5), aspidistrin (6), tigogenin-3-O-β-D-lucotrioside (7), desglucolanatigonin II (8), and degalactotigonin (9), were isolated from Solanum lyratum Thunb. Their cytotoxic activities were tested in two cancer cell lines by MTT method. One of the steroidal glycosides (6) showed significant cytotoxic activity against gastric cancer SGC7901 and liver cancer BEL-7402 cells., (Copyright © 2018 China Pharmaceutical University. Published by Elsevier B.V. All rights reserved.)

[This corrects the article DOI: 10.1038/lsa.2017.153.].

Imaging cells and microvasculature in the living brain is crucial to understanding an array of neurobiological phenomena. Here, we introduce a skull optical clearing window for imaging cortical structures at synaptic resolution. Combined with two-photon microscopy, this technique allowed us to repeatedly image neurons, microglia and microvasculature of mice. We applied it to study the plasticity of dendritic spines in critical periods and to visualize dendrites and microglia after laser ablation. Given its easy handling and safety, this method holds great promise for application in neuroscience research., Competing Interests: The authors declare no conflict of interest.

Uterine fluid contains a high concentration of [Formula: see text] which plays an essential role in sperm capacitation and fertilization. In addition, the [Formula: see text] concentration in uterine fluid changes periodically during the estrous cycle. It is well-known that the endometrial epithelium contains machineries involving the apical SLC26 family anion exchangers for secreting [Formula: see text] into the uterine fluid. In the present study, we find for the first time that the electroneutral Na + /[Formula: see text] cotransporter NBCn1 is expressed at the apical membrane of the endometrial epithelium. The protein abundance of the apical NBCn1 and that of the apical SLC26A4 and SLC26A6 are reciprocally regulated during the estrous cycle in the uterus. NBCn1 is most abundant at diestrus, whereas SLC26A4/A6 are most abundant at proestrus/estrus. In the ovariectomized mice, the expression of uterine NBCn1 is inhibited by β-estradiol, but stimulated by progesterone, whereas that of uterine SLC26A4/A6 is stimulated by β-estradiol. In vivo perfusion studies show that the endometrial epithelium is capable of both secreting and reabsorbing [Formula: see text]. Moreover, the activity for [Formula: see text] secretion by the endometrial epithelium is significantly higher at estrus than it is at diestrus. The opposite is true for [Formula: see text] reabsorption. We conclude that the endometrial epithelium simultaneously contains the activity for [Formula: see text] secretion involving the apical SLC26A4/A6 and the activity for [Formula: see text] reabsorption involving the apical NBCn1, and that the acid-base homeostasis in the uterine fluid is regulated by the finely-tuned balance of the two activities.

Objective: To investigate the expression of long non-coding RNA DUXAP10 in ovarian cancer and its effect on ovarian cancer cell lines HO8910 and A2780 cells., Materials and Methods: Search the microarray dataset from the Gene Expression Omnibus (GEO) database using the keywords "ovarian cancer" and "GPL570". The differentially expressed genes in ovarian cancer tissues and normal ovarian tissues were analyzed by bioinformatics. Normal ovarian epithelial cells IOSE386, ovarian cancer HEY, HO8910 and A2780 cell lines were cultured. Cell proliferation assay was detected by CCK8 method and cloning formation assay was done. Quantitative Real-time polymerase chain reaction (qRT-PCR) was used to detect the expression of RNA., Results: The results showed that the expression of DUXAP10 in ovarian cancer tissues was significantly higher than that in normal ovarian tissues, which was consistent with those of TCGA. Clinical data analysis showed that the expression level of DUXAP10 was correlated with tumor size and FIGO stage in clinical patients. Compared with the negative control group, the proliferation ability and cell cloning ability of HO8910 cells overexpressing DUXAP10 were significantly increased (p<0.001), while the proliferation and cell cloning ability of A2780 cells interfering with DUXAP10 were significantly decreased (p<0.001), indicating that DUXAP10 played a role in promoting the proliferation of ovarian cancer cells., Conclusions: DUXAP10 was significantly overexpressed in ovarian cancer tissues, and its expression was positively correlated with tumor size and FIGO stage in clinical patients. DUXAP10 promoted the proliferation of ovarian cancer cells and was expected to be a predictor and a potential therapeutic target of ovarian cancer.

This study investigates the effect of nuclear factor erythroid 2-related factor 2-antioxidant response element (Nrf2-ARE) signaling pathway in vascular calcification (VC) via inducing Autophagy in renal vascular smooth muscle cells (VSMCs). VSMCs were assigned into six experimental groups: the normal control, high phosphorus, si-negative control (si-NC), Nrf2-siRNA, over-expressed Nrf2, and negative control (NC) groups. RT-PCR was applied to detect the mRNA expressions of the desired Nrf2-ARE signaling pathway-related genes (Nrf2, NQO-1, HO-1, γ-GCS). The protein products of these genes: apoptosis-related genes (LC3I and LC3II), osteogenic marker proetins (Runt-related transcription factor 2) Runx2 and BMP2 were all detected by Western blotting. Autophagosomes in VSMCs were observed under a transmission electron microscope. We discovered an increased calcium ion concentration and upregulated Runx2, BMP2, Nrf2, HO-1, γ-GCS, NQO-1, and LC3II/LC3I expressions in the high phosphorous, si-NC and Nrf2-siRNA, and NC groups, compared with the normal control group. Compared to the high phosphorus and si-NC groups, higher levels of Runx2 and BMP2 but decreased Nrf2, HO-1, γ-GCS, NQO-1, and LC3II/LC3I expressions were detected in the Nrf2-siRNA group. The high phosphorus, si-NC and over-expressed Nrf2 experimental groups all had increased Nrf2, NQO-1, HO-1, γ-GCS, and LC3II/LC3I expressions as well as high numbers of autophagosomes compared with the normal control group. Finally, we detected a lower amount of autophagosomes presence and Nrf2, NQO-1, HO-1 γ-GCS, and LC3II/LC3 protein expression of Nrf2-siRNA group than that of the high phosphorus and si-NC groups. Activation of Nrf2-ARE signaling pathway may prevent hyperphosphatemia-induced VC by inducing autophagy in VSMCs. J. Cell. Biochem. 118: 4708-4715, 2017. © 2017 Wiley Periodicals, Inc., (© 2017 Wiley Periodicals, Inc.)

Pulldown assay is a conventional method to determine protein-protein interactions in vitro . Expressing a protein of interest with two different tags allows testing whether both versions can be captured via one of the two tags as homooligomeric complex. This protocol is based on streptavidin bead capture of a biotinylated protein and co-associated Flag-tagged protein using Streptavidin MagBeads., Competing Interests: The authors declare no conflict of interest.

The bioluminescence resonance energy transfer (BRET) assay can be used as an indicator of molecular approximation and/or interaction. A significant resonance energy transfer signal is generated when the acceptor, having the appropriate spectral overlap with the donor emission, is approximated with the donor. In the example provided, proteins tagged with bioluminescent Renilla luciferase (Rlu) as donor and yellow fluorescent protein (YFP) as acceptor were co-expressed in cells. This pair of donor and acceptor have an approximate Förster distance of 4.4 nm, providing the optimal working distance (Dacres et al ., 2010). This technique can be used to explore the time-course of specific molecular interactions that occur in living cells., Competing Interests: Authors have no conflicts of interest or competing interests.

γ-Secretase epsilon-cleavage assay is derived from the cell-based Tango assay (Kang et al ., 2015), and is a fast and sensitive method to determine the initial cleavage of C99 by γ-secretase. In this protocol, we use HTL cells, which are HEK293 cells with a stably integrated luciferase reporter under the control of the bacterial tetO operator element, in which C99 C terminally fused to a reversed tetracyclin-inducible activator (rTA) transcriptional activator is expressed. Endogenous or transfected γ-secretase cleaves a C terminally fused rTA transcriptional activator from C99, allowing rTA to move to the nucleus to activate a luciferase reporter gene as a measurement for γ-secretase cleavage activity., Competing Interests: The authors declare no conflict of interest.

The Tango assay is a protein-protein interaction assay, in which a transcription factor (rTA) is fused to a membrane-bound protein via a linker that contains a cleavage site for TEV protease, whereas a soluble interaction partner is fused to TEV protease (Barnea et al. , 2008). Association between the two interaction partners leads to an efficient cleavage of the transcription factor, allowing it to translocate to the nucleus and activate a luciferase reporter gene as measurement of the interactions. In this modified assay, we fused one copy of the membrane-spanning amyloid precursor protein (APP) C99 region to TEV site-rTA (C99-TEV site-rTA) and a second copy to TEV protease (C99-TEV) to analyze intramembrane C99-C99 interaction in live cells., Competing Interests: The authors declare no conflict of interest.

γ-Secretase is an intramembrane aspartyl protease that cleaves the C99 fragment of amyloid precursor protein to generate extracellular Aβ peptides. These peptides can oligomerize and aggregate to form amyloid plaques, processes that are widely believed to be causal for Alzheimer's disease. In spite of this critical function, it remains unknown how γ-secretase recognizes C99 and its other substrates, including Notch. In this study we determined E22-K55 as the minimal C99 fragment that was sufficient and required for initial cleavage. Within this fragment, we identified four determinants: (i) a transferable extracellular determinant that differed between C99 and Notch, and which included negative charge in the case of C99, (ii) the amino acid sequence of the C-terminal half of the transmembrane helix, (iii) an invariant lysine or arginine at the intracellular membrane border, and (iv) a positive charge cluster that included the invariant lysine/arginine. We demonstrated that the charge clusters of C99 and Notch receptors could directly bind phosphatidylinositol 4,5-bisphosphate (PIP2). The PIP2-binding cluster was required for γ-secretase cleavage, and modulation of membrane PIP2 levels strongly affected γ-secretase cleavage levels and the Aβ 40 /Aβ 42 ratio, providing support for the importance of the PIP2 interaction in cells. Together, these studies provide critically needed insight into substrate recognition by γ-secretase.

One of the hallmarks of Alzheimer's disease is the formation of extracellular amyloid plaques that consist mainly of abnormally aggregated forms of amyloid β (Aβ) peptides. These peptides are generated by γ-secretase-catalyzed cleavage of a dimeric membrane-bound C-terminal fragment (C99) of the amyloid precursor protein. Although C99 homodimerization has been linked to Aβ production and changes in the aggregation-determining Aβ42/Aβ40 ratio, the motif through which C99 dimerizes has remained controversial. Here, we have used two independent assays to gain insight into C99 homodimerization in the context of the membrane of live cells: bioluminescence resonance energy transfer and Tango membrane protein-protein interaction assays, which were further confirmed by traditional pull-down assays. Our results indicate a four-amino acid region within the C99 transmembrane helix ( 43 TVIV 46 ) as well as its local secondary structure as critical determinants for homodimerization. These four amino acids are also a hot spot of familial Alzheimer's disease-linked mutations that both decrease C99 homodimerization and γ-secretase cleavage and alter the initial cleavage site to increase the Aβ42/40 ratio., (© 2017 by The American Society for Biochemistry and Molecular Biology, Inc.)