Knockdown of phosphotyrosyl phosphatase activator induces apoptosis via mitochondrial pathway and the attenuation by simultaneous tau hyperphosphorylation

Phosphotyrosyl phosphatase activator (PTPA) is decreased in the brains of Alzheimer's disease (AD) and the AD transgenic mouse models. Here, we investigated whether down‐regulation of PTPA affects cell viability and the underlying mechanisms. We found that PTPA was located in the integral membrane of mitochondria, and knockdown of PTPA induced cell apoptosis in HEK293 and N2a cell lines. PTPA knockdown decreased mitochondrial membrane potential and induced Bax translocation into the mitochondria with a simultaneous release of Cyt C, activation of caspase‐3, cleavage of poly (DNA ribose) polymerase (PARP), and decrease in Bcl‐xl and Bcl‐2 protein levels. Over‐expression of Protein phosphatase 2A (PP2A) catalytic subunit (PP2A_C) did not rescue the apoptosis induced by PTPA knockdown, and PTPA knockdown did not affect the level of and their phosphorylation of mitogen‐activated protein kinases (MAPKs), indicating that PP2A and MAPKs were not involved in the apoptosis induced by PTPA knockdown. In the cells with over‐expression of tau, PTPA knockdown induced PP2A inhibition and tau hyperphosphorylation but did not cause significant cell death. These data suggest that PTPA deficit causes apoptotic cell death through mitochondrial pathway and simultaneous tau hyperphosphorylation attenuates the PTPA‐induced cell death.

     

Molecular mechanism of ERK dephosphorylation by striatal‐enriched protein tyrosine phosphatase

Striatal‐enriched tyrosine phosphatase (STEP) is an important regulator of neuronal synaptic plasticity, and its abnormal level or activity contributes to cognitive disorders. One crucial downstream effector and direct substrate of STEP is extracellular signal‐regulated protein kinase (ERK), which has important functions in spine stabilisation and action potential transmission. The inhibition of STEP activity toward phospho‐ERK has the potential to treat neuronal diseases, but the detailed mechanism underlying the dephosphorylation of phospho‐ERK by STEP is not known. Therefore, we examined STEP activity toward para‐nitrophenyl phosphate, phospho‐tyrosine‐containing peptides, and the full‐length phospho‐ERK protein using STEP mutants with different structural features. STEP was found to be a highly efficient ERK tyrosine phosphatase that required both its N‐terminal regulatory region and key residues in its active site. Specifically, both kinase interaction motif (KIM) and kinase‐specific sequence of STEP were required for ERK interaction. In addition to the N‐terminal kinase‐specific sequence region, S245, hydrophobic residues L249/L251, and basic residues R242/R243 located in the KIM region were important in controlling STEP activity toward phospho‐ERK. Further kinetic experiments revealed subtle structural differences between STEP and HePTP that affected the interactions of their KIMs with ERK. Moreover, STEP recognised specific positions of a phospho‐ERK peptide sequence through its active site, and the contact of STEP F311 with phospho‐ERK V205 and T207 were crucial interactions. Taken together, our results not only provide the information for interactions between ERK and STEP, but will also help in the development of specific strategies to target STEP‐ERK recognition, which could serve as a potential therapy for neurological disorders.

     

Tumor extracellular acidity-activated nanoparticles as drug delivery systems for enhanced cancer therapy

pH-responsive nanoparticles (NPs) are currently under intense development as drug delivery systems for cancer therapy. Among various pH-responsiveness, NPs that are designed to target slightly acidic extracellular pH environment (pH_e) of solid tumors provide a new paradigm of tumor targeted drug delivery. Compared to conventional specific surface targeting approaches, the pH_e-targeting strategy is considered to be more general due to the common occurrence of acidic microenvironment in solid tumors. This review mainly focuses on the design and applications of pH_e-activated NPs, with special emphasis on pH_e-activated surface charge reversal NPs, for drug and siRNA delivery to tumors. The novel development of NPs described here offers great potential for achieving better therapeutic effects in cancer treatment.     

Alfalfa (Medicago sativa L.)/Maize (Zea mays L.) Intercropping Provides a Feasible Way to Improve Yield and Economic Incomes in Farming and Pastoral Areas of Northeast China

Given the growing challenges to food and eco-environmental security as well as sustainable development of animal husbandry in the farming and pastoral areas of northeast China, it is crucial to identify advantageous intercropping modes and some constraints limiting its popularization. In order to assess the performance of various intercropping modes of maize and alfalfa, a field experiment was conducted in a completely randomized block design with five treatments: maize monoculture in even rows, maize monoculture in alternating wide and narrow rows, alfalfa monoculture, maize intercropped with one row of alfalfa in wide rows and maize intercropped with two rows of alfalfa in wide rows. Results demonstrate that maize monoculture in alternating wide and narrow rows performed best for light transmission, grain yield and output value, compared to in even rows. When intercropped, maize intercropped with one row of alfalfa in wide rows was identified as the optimal strategy and the largely complementary ecological niches of alfalfa and maize were shown to account for the intercropping advantages, optimizing resource utilization and improving yield and economic incomes. These findings suggest that alfalfa/maize intercropping has obvious advantages over monoculture and is applicable to the farming and pastoral areas of northeast China.     

Intercropping Enhances Productivity and Maintains the Most Soil Fertility Properties Relative to Sole Cropping

Yield and nutrient acquisition advantages are frequently found in intercropping systems. However, there are few published reports on soil fertility in intercropping relative to monocultures. A field experiment was therefore established in 2009 in Gansu province, northwest China. The treatments comprised maize/faba bean, maize/soybean, maize/chickpea and maize/turnip intercropping, and their correspoding monocropping. In 2011 (the 3^rd year) and 2012 (the 4^th year) the yields and some soil chemical properties and enzyme activities were examined after all crop species were harvested or at later growth stages. Both grain yields and nutrient acquisition were significantly greater in all four intercropping systems than corresponding monocropping over two years. Generally, soil organic matter (OM) did not differ significantly from monocropping but did increase in maize/chickpea in 2012 and maize/turnip in both years. Soil total N (TN) did not differ between intercropping and monocropping in either year with the sole exception of maize/faba bean intercropping receiving 80 kg P ha⁻¹ in 2011. Intercropping significantly reduced soil Olsen-P only in 2012, soil exchangeable K in both years, soil cation exchangeable capacity (CEC) in 2012, and soil pH in 2012. In the majority of cases soil enzyme activities did not differ across all the cropping systems at different P application rates compared to monocrops, with the exception of soil acid phosphatase activity which was higher in maize/legume intercropping than in the corresponding monocrops at 40 kg ha⁻¹ P in 2011. P fertilization can alleviate the decline in soil Olsen-P and in soil CEC to some extent. In summary, intercropping enhanced productivity and maintained the majority of soil fertility properties for at least three to four years, especially at suitable P application rates. The results indicate that maize-based intercropping may be an efficient cropping system for sustainable agriculture with carefully managed fertilizer inputs.     

Tonsil-derived mesenchymal stem cells alleviate concanavalin A-induced acute liver injury

Acute liver failure, the fatal deterioration of liver function, is the most common indication for emergency liver transplantation, and drug-induced liver injury and viral hepatitis are frequent in young adults. Stem cell therapy has come into the limelight as a potential therapeutic approach for various diseases, including liver failure and cirrhosis. In this study, we investigated therapeutic effects of tonsil-derived mesenchymal stem cells (T-MSCs) in concanavalin A (ConA)- and acetaminophen-induced acute liver injury. ConA-induced hepatitis resembles viral and immune-mediated hepatic injury, and acetaminophen overdose is the most frequent cause of acute liver failure in the United States and Europe. Intravenous administration of T-MSCs significantly reduced ConA-induced hepatic toxicity, but not acetaminophen-induced liver injury, affirming the immunoregulatory capacity of T-MSCs. T-MSCs were successfully recruited to damaged liver and suppressed inflammatory cytokine secretion. T-MSCs expressed high levels of galectin-1 and -3, and galectin-1 knockdown which partially diminished interleukin-2 and tumor necrosis factor α secretion from cultured T-cells. Galectin-1 knockdown in T-MSCs also reversed the protective effect of T-MSCs on ConA-induced hepatitis. These results suggest that galectin-1 plays an important role in immunoregulation of T-MSCs, which contributes to their protective effect in immune-mediated hepatitis. Further, suppression of T-cell activation by frozen and thawed T-MSCs implies great potential of T-MSC banking for clinical utilization in immune-mediated disease.     

他克莫司和卡泊三醇软膏治疗四肢斑块状银屑病的疗效和安全性分析

目的:探讨他克莫司和卡泊三醇软膏治疗四肢斑块状银屑病的疗效和安全性。方法:选取2011年4月至2013年8月于我院诊治的84例四肢斑块状银屑病患者,将患者随机分为A组和B组,每组各42例,分别采用他克莫司和卡泊三醇软膏治疗。评定PASI以及疗效指数,并对用药过程中患者的不良事件进行观察记录。结果:A、B两组患者治疗后各时间点PASI评分与治疗前相比较均显著降低,差异有统计学意义(P0.05);但同一时间组间对比,差异并无统计学意义(P0.05)。A组银屑病患者的总有效率为64.29%,与B组的69.05%相比,差异无统计学意义(P0.05)。结论:他克莫司与卡泊三醇软膏治疗四肢斑块状银屑病均安全有效,且二药相比,疗效相当。     

Affinity purification of Csk protein tyrosine kinase based on its catalytic requirement for divalent metal cations

Protein tyrosine kinase Csk requires two Mg2+ ions for activity: one magnesium is part of the ATP-Mg complex, and the second free Mg2+ ion is required as an essential activator. Zn2+ can bind to this site to replace Mg2+, which inhibits Csk kinase activity. The binding is reversible and removal of Zn2+ results in an active Csk apoenzyme. In this communication, we report that this tight binding can be used as a mechanism for affinity purification of Csk. When bacterial cell lysate containing overexpressed GST-Csk was applied to a column of Zn2+-iminodiacetic acid immobilized to agarose, Csk was specifically retained by the column. Since the binding of Csk to Zn2+ is not affected by up to 200 mM NaCl, high ionic strength conditions were used in the purification procedure, minimizing nonspecific binding due to ionic interactions. Washing the column with 200 mM NaCl and 50 mM imidazole removed virtually all other proteins from the column while Csk remained bound. The retained Csk enzyme was eluted with 1 M imidazole. The 1 M imidazole-eluted fraction contained pure Csk that had a specific activity similar to the enzyme purified by a glutathione-agarose affinity column.     

重组人干扰素—β的中试研究

从大肠杆菌中大规模纯化新型干扰素β(IFN-βser17).首先建立IFN-βser17发酵和纯化工艺,连续大量纯化三批,并对纯化终产品进行全面鉴定.建立了稳定的发酵和纯化工艺流程,中试三批菌产量平均为4.33g/L,IFNβser17的表达量平均为20%,经破碎、粗提、精制后IFN-βser17的比活达2×107IU/mg以上,纯度超过96%,其他检定项目也均符合规程要求.