Ethanol induced the formation of β‐sheet and amyloid‐like fibrils by surfactant‐like peptide A6K

Self‐assembly of natural or designed peptides into fibrillar structures based on β‐sheet conformation is a ubiquitous and important phenomenon. Recently, organic solvents have been reported to play inductive roles in the process of conformational change and fibrillization of some proteins and peptides. In this study, we report the change of secondary structure and self‐assembling behavior of the surfactant‐like peptide A6K at different ethanol concentrations in water. Circular dichroism indicated that ethanol could induce a gradual conformational change of A6K from unordered secondary structure to β‐sheet depending upon the ethanol concentration. Dynamic light scattering and atomic force microscopy revealed that with an increase of ethanol concentration the nanostructure formed by A6K was transformed from nanosphere/string‐of‐beads to long and smooth fibrils. Furthermore, Congo red staining/binding and thioflavin‐T binding experiments showed that with increased ethanol concentration, the fibrils formed by A6K exhibited stronger amyloid fibril features. These results reveal the ability of ethanol to promote β‐sheet conformation and fibrillization of the surfactant‐like peptide, a fact that may be useful for both designing self‐assembling peptide nanomaterials and clarifying the molecular mechanism behind the formation of amyloid fibrils. Copyright © 2013 European Peptide Society and John Wiley & Sons, Ltd.     

A Test of Current Models for the Mechanism of Milk‐Lipid Droplet Secretion

Milk lipid is secreted by a unique process, during which triacylglycerol droplets bud from mammary cells coated with an outer bilayer of apical membrane. In all current schemes, the integral protein butyrophilin 1A1 (BTN) is postulated to serve as a transmembrane scaffold, which interacts either with itself or with the peripheral proteins, xanthine oxidoreductase (XOR) and possibly perilipin‐2 (PLIN2), to form an immobile bridging complex between the droplet and apical surface. In one such scheme, BTN on the surface of cytoplasmic lipid droplets interacts directly with BTN in the apical membrane without binding to either XOR or PLIN2. We tested these models using both biochemical and morphological approaches. BTN was concentrated in the apical membrane in all species examined and contained mature N‐linked glycans. We found no evidence for the association of unprocessed BTN with intracellular lipid droplets. BTN‐enhanced green fluorescent protein was highly mobile in areas of mouse milk‐lipid droplets that had not undergone post‐secretion changes, and endogenous mouse BTN comprised only 0.5–0.7% (w/w) of the total protein, i.e. over 50‐fold less than in the milk‐lipid droplets of cow and other species. These data are incompatible with models of milk‐lipid secretion in which BTN is the major component of an immobile global adhesive complex and suggest that interactions between BTN and other proteins at the time of secretion are more transient than previously predicted. The high mobility of BTN in lipid droplets marks it as a potential mobile signaling molecule in milk .     

Novel contribution of cell surface and intracellular M1‐muscarinic acetylcholine receptors to synaptic plasticity in hippocampus

Muscarinic acetylcholine receptors (mAChRs) are well known to transmit extracellular cholinergic signals into the cytoplasm from their position on the cell surface. However, we show here that M1‐mAChRs are also highly expressed on intracellular membranes in neurons of the telencephalon and activate signaling cascades distinct from those of cell surface receptors, contributing uniquely to synaptic plasticity. Radioligand‐binding experiments with cell‐permeable and ‐impermeable ligands and immunohistochemical observations revealed intracellular and surface distributions of M1‐mAChRs in the hippocampus and cortex of rats, mice, and humans, in contrast to the selective occurrence on the cell surface in other tissues. All intracellular muscarinic‐binding sites were abolished in M1‐mAChR‐gene‐knockout mice. Activation of cell surface M1‐mAChRs in rat hippocampal neurons evoked phosphatidylinositol hydrolysis and network oscillations at theta rhythm, and transiently enhanced long‐term potentiation. On the other hand, activation of intracellular M1‐mAChRs phosphorylated extracellular‐regulated kinase 1/2 and gradually enhanced long‐term potentiation. Our data thus demonstrate that M1‐mAChRs function at both surface and intracellular sites in telencephalon neurons including the hippocampus, suggesting a new mode of cholinergic transmission in the central nervous system.     

Isolation of Ciliatine (2-Aminoethylphosphonic Acid) from the Bile of the Bovine

To elucidate the formation mechanism of N,N′-dialkylpyrazine cation radical during browning reaction of sugars with amino compounds, main products in an early stage of the reaction were determined quantitatively by TLC and GLC. It was shown that the Schiff base, two-carbon fragmental product of sugar, the free radical and deoxyosone were successively produced prior to the browning. Polarographical measurements indicated that the radical formation was induced by the production of some reducing substances in the reaction mixture. These results suggest that the free radical was formed by the reduction of N,N′-dialkylpyrazinium; a compound, which demonstrated to have a strong activity to browning, might be formed by condensation of two-carbon enaminol followed by oxidation.     

Depletion of preexisting B-cell lymphoma 2-expressing senescent cells before vaccination impacts antigen-specific antitumor immune responses in old mice

The age-related decline in immunity reduces the effectiveness of vaccines in older adults. Immunosenescence is associated with chronic, low-grade inflammation, and the accumulation of senescent cells. The latter express Bcl-2 family members (providing resistance to cell death) and exhibit a pro-inflammatory, senescence-associated secretory phenotype (SASP). Preexisting senescent cells cause many aging-related disorders and therapeutic means of eliminating these cells have recently gained attention. The potential consequences of senescent cell removal on vaccine efficacy in older individuals are still ignored. We used the Bcl-2 family inhibitor ABT-263 to investigate the effects of pre-vaccination senolysis on immune responses in old mice. Two different ovalbumin (OVA)-containing vaccines (containing a saponin-based or a CpG oligodeoxynucleotide adjuvant) were tested. ABT-263 depleted senescent cells (apoptosis) and ablated the basal and lipopolysaccharide-induced production of SASP-related factors in old mice. Depletion of senescent cells prior to vaccination (prime/boost) had little effect on OVA-specific antibody and T-cell responses (slightly reduced and augmented, respectively). We then used a preclinical melanoma model to test the antitumor potential of senolysis before vaccination (prime with the vaccine and OVA boost by tumor cells). Surprisingly, ABT-263 treatment abrogated the vaccine's ability to protect against B16 melanoma growth in old animals, an effect associated with reduced antigen-specific T-cell responses. Some, but not all, of the effects were age-specific, which suggests that preexisting senescent cells were partly involved. Hence, depletion of senescent cells modifies immune responses to vaccines in some settings and caution should be taken when incorporating senolytics into vaccine-based cancer therapies.     

血清UA、sdLDL、sST2对急性心肌梗死患者PCI术后无复流的预测价值分析

摘要 目的：探讨血清尿酸（UA）、小而密低密度脂蛋白（sdLDL）、可溶性致癌抑制因子2（sST2）对急性心肌梗死（AMI）患者经皮冠状动脉介入治疗（PCI）术后无复流（NRF）的预测价值。方法：选取2021年1月～2023年1月睢宁县人民医院收治的196例AMI患者为AMI组,根据PCI术后是否发生NRF分为NRF组和血流正常组,另选取同期120名体检健康志愿者为对照组。比较AMI组与对照组血清UA、sdLDL、sST2水平。采用多因素Logistic回归分析AMI患者PCI术后NRF的影响因素,采用受试者工作特征（ROC）曲线分析血清UA、sdLDL、sST2水平对AMI患者PCI术后NRF的预测价值。结果：与对照组比较,AMI组血清UA、sdLDL、sST2水平升高（P＜0.05）。196例AMI患者PCI术后NRF发生率为34.69%,NRF组年龄大于血流正常组,糖尿病比例、肌酸激酶同工酶（CK-MB）、肌钙蛋白I（cTnI）、低密度脂蛋白胆固醇（LDL-C）、UA、sdLDL、sST2水平高于血流正常组（P＜0.05）。多因素Logistic回归分析显示,年龄增加和UA、sdLDL、sST2升高为AMI患者PCI术后NRF的独立危险因素（P＜0.05）。ROC曲线分析显示,血清UA、sdLDL、sST2水平单独和联合预测AMI患者PCI术后NRF的曲线下面积AUC(0.95CI)分别为0.707(0.481～0.934)、0.742(0.513～0.955)、0.737(0.480～0.970)、0.863(0.737～0.960),联合预测大于单独预测指标。结论：血清UA、sdLDL、sST2水平升高为AMI患者PCI术后NRF的独立危险因素,血清UA、sdLDL、sST2水平联合预测AMI患者PCI术后NRF的价值较高。     

Small Networks Encode Decision-Making in Primary Auditory Cortex

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FUS Regulates Activity of MicroRNA-Mediated Gene Silencing

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Combinatorial Control of Recruitment of a Variant PRC1.6 Complex in Embryonic Stem Cells

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