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目的研究锂对慢性铝暴露大鼠脑内周期蛋白依赖性激酶5（CDK5）和蛋白磷酸酯酶2A（PP2A）表达的影响,进一步探讨锂抑制tau蛋白磷酸化的作用机制。方法慢性铝暴露大鼠12只,随机分为锂治疗组和非治疗组。锂治疗组给予氯化锂[200mg/（kg·d）]溶液连续灌胃6周;非治疗组以等量生理盐水灌胃。另取6只同月龄非铝暴露大鼠为正常对照组。Morris水迷宫测试3组大鼠学习记忆功能;Western blotting检测大鼠大脑皮层及海马磷酸化tau蛋白、CDK5、PP2A的表达。结果慢性铝暴露非治疗组大鼠脑内磷酸化tau蛋白含量、CDK5表达明显高于正常对照组大鼠（P〈0.05）,且慢性铝暴露非治疗组大鼠脑内磷酸化tau蛋白含量与CDK5表达呈正相关（r=0.702,P=0.036）。锂治疗组大鼠脑内磷酸化tau蛋白含量、CDK5表达明显低于非治疗组（P〈0.05）,且锂治疗组大鼠脑内CDK5表达与磷酸化tau蛋白含量呈正相关（r=0.871,P=0.024）,而正常组、锂治疗组和非治疗组大鼠皮层及海马PP2A含量无明显差异（P〉0.05）。结论抑制脑内CDK5表达可能是锂降低tau蛋白过度磷酸化,减少大鼠脑内神经原纤维缠结的又一途径。

Increased crop yields are required to support rapid population growth worldwide. Grain weight is a key compo- nent of rice yield, but the underlying molecular mechanisms that control it remain elusive. Here, we report the clon- ing and characterization of a new quantitative trait locus （QTL） for the control of rice grain length, weight and yield. This locus, GL3.1, encodes a protein phosphatase kelch （PPKL） family -- Ser/Thr phosphatase. GL3.1 is a member of the large grain WY3 variety, which is associated with weaker dephosphorylation activity than the small grain FAZ1 variety. GL3.I-WY3 influences protein phosphorylation in the spikelet to accelerate cell division, thereby re- suiting in longer grains and higher yields. Further studies have shown that GL3.1 directly dephosphorylates its sub- strate, Cyclin-TI;3, which has only been rarely studied in plants. The downregulation of Cyclin-T1;3 in rice resulted in a shorter grain, which indicates a novel function for Cyclin-T in cell cycle regulation. Our findings suggest a new mechanism for the regulation of grain size and yield that is driven through a novel phosphatase-mediated process that affects the phosphorylation of Cyclin-T1;3 during cell cycle progression, and thus provide new insight into the mechanisms underlying crop seed development. We bred a new variety containing the natural GL3.1 allele that demonstrated increased grain yield, which indicates that GL3.1 is a powerful tool for breeding high-yield crops.

Proline-directed phosphorylation is a posttranslational modification that is instrumental in regulating signaling from the plasma membrane to the nucleus, and its dysregulation contributes to cancer development. Protein interacting with never in mitosis A1 （Pinl）, which is overexpressed in many types of cancer, isomerizes specific phosphorylat- ed Ser/Thr-Pro bonds in many substrate proteins, including glycolytic enzyme, protein kinases, protein phosphatases, methyltransferase, lipid kinase, ubiquitin E3 ligase, DNA endonuclease, RNA polymerase, and transcription activa- tors and regulators. This Pinl-mediated isomerization alters the structures and activities of these proteins, thereby regulating cell metabolism, cell mobility, cell cycle progression, cell proliferation, cell survival, apoptosis and tumor development.

Proper activation of protein phosphatase 2A （PP2A） catalytic subunit is central for the complex PP2A regulation and is crucial for broad aspects of cellular function. The crystal structure of PP2A bound to PP2A phosphatase activator （PTPA） and ATPyS reveals that PTPA makes broad contacts with the structural elements surrounding the PP2A active site and the adenine moiety of ATP. PTPA-binding stabilizes the protein fold of apo-PP2A required for activation, and orients ATP phosphoryl groups to bind directly to the PP2A active site. This allows ATP to modulate the metal-binding preferences of the PP2A active site and utilize the PP2A active site for ATP hydrolysis. In vitro, ATP selectively and drastically enhances binding of endogenous catalytic metal ions, which requires ATP hydrolysis and is crucial for acquisition of pSer/Thr-specific phosphatase activity. Furthermore, both PP2A- and ATP-binding are required for PTPA function in cell proliferation and survival. Our results suggest novel mechanisms of PTPA in PP2A activation with structural economy and a unique ATP-binding pocket that could potentially serve as a specific therapeutic target.

Protein phosphatase 2A （PP2A） accounts for the majority of total Ser/Thr phosphatase activities in most cell types and regulates many biological processes. PP2A holoenzymes contain a scaffold A subunit, a cat- alytic C subunit, and one of the regulatory/targeting B subunits. How the B subunit controls PP2A localization and substrate specificity, which is a crucial aspect of PP2A regulation, remains poorly understood. The kine- tochore is a critical site for PP2A functioning, where PP2A orchestrates chromosome segregation through its interactions with BubR1. The PP2A-BubR1 interac- tion plays important roles in both spindle checkpoint silencing and stable microtubule-kinetochore attach- ment. Here we present the crystal structure of a PP2A B56-BubRI complex, which demonstrates that a con- served BubRl LxxlxE motif binds to the concave side of the B56 pseudo-HEAT repeats. The BubR1 motif binds to a groove formed between B56 HEAT repeats 3 and 4, which is quite distant from the B56 binding surface for PP2A catalytic C subunit and thus is unlikely to affect PP2A activity. In addition, the BubR1 binding site on B56 is far from the B56 binding site of shugoshin, another kinetochore PP2A-binding protein, and thus BubR1 and shugoshin can potentially interact with PP2A-B56 simultaneously. Our structural and biochemical analysis indicates that other proteins with the LxxlxE motif may also bind to the same PP2A B56 surface. Thus, our structure of the PP2A B56-BubR1 complex provides important insights into how the B56 subunit directs the recruitment of PP2A to specific targets.

The protein phosphatases PP2A and PP1 are major regulators of a variety of cellular processes in yeast and other eukaryotes. Here, we reveal that both enzymes are direct targets of glucose sensing. Addition of glucose to glucose- deprived yeast cells triggered rapid posttranslational activation of both PP2A and PP1. Glucose activation of PP2A is controlled by regulatory subunits Rtsl, Cdc55, Rrdl and Rrd2. It is associated with rapid carboxymethylation of the catalytic subunits, which is necessary but not sufficient for activation. Glucose activation of PP1 was fully dependent on regulatory subunits Regl and Shpl. Absence of Gacl, Glc8, Reg2 or Redl partially reduced activation while Pigl and Pig2 inhibited activation.

Background： Ovarian serous adenocarcinoma can be divided into low- and high-grade tumors, which exhibit substantial differences in pathogenesis, clinicopathology, and prognosis. This study aimed to investigate the difl＇erences in the PH domain leucine-rich repeat protein phosphatase （PHLPP）, tbrkhead llomeobox type O3a （FoxO3a）, and RAD51 protein expressions, and their associations with prognosis in patients with low- and high-grade ovarian serous adenocarcinomas. Methods： The PH LPP, FoxO3a, and RA D51 protein expressions were examined in 94 high- and 26 low-grade ovarian serous adenocarcinomas by immunohistochemistry. The differences in expression and their relationships with pathological features and prognosis were analyzed. Results： In high-grade serous adenocarcinomas, the positive rates of PHLPP and goxO3a were 24.5% and 26.6%, while in low-grade tumors, they were 23.1% and 26.9%, respectively （P 〈 0.05 vs. the control specimens; low- vs. high-grade： P 〉 0.（15）. The positive rates of RAD51 were 70.2% and 65.4% in high- and low-grade serous adenocarcinomas, respectively （P 〈 0.（15 vs. the control specimens; low- vs. high-grade： P 〉 0.05）. Meanwhile, in high-grade tumors, Stage Ⅲ/Ⅳ tumors and lymph node and omental metastases were significantly associated with lower PHLPP and FoxO3a and higher RAD51 expression. The 5-year survival rates of patients with PHLPP- and FoxO3a-positive high-grade tumors （43.5% and 36.0%） were significantly higher than in patients with PHLPP-negative tumors （5.6% and 7.2%, respectively; P 〈 0.05）. Similarly, the 5-year survival rate of RAD5 l-positive patients （3.0%） was significantly lower than in negative patients （42.9%： P〈 0.05）. In low-grade tumors, the PHLPP, FoxO3a, and RAD51 expressions were not significantly correlated with lymph node metastasis, omental metastasis, Federation of Gynecology and Obstetrics stage, or prognosis. Conclusions： Abnormal PHLPP, FoxO3a, and RAD51 protein expressions may be involved in the development of high- and low-grade ovarian serous adenocarcinomas, suggesting conlmon molecular pathways. Decreased PH LPP and FoxO3a and increased RAD51 protein expression may be important molecular markers for poor prognosis, and RAD51 may be an independent prognosis factor, of high-grade, but not low-grade, ovarian serous adenocarcinomas.

Within a multicellular tissue cells may coordinately form a singular or multiple polar axes, but it is unclear whether a common mechanism governs different types of polar axis formation. The phosphorylation status of PIN proteins, which is directly affected by the PINOID （PID） protein kinase and the PP2A protein phosphatase, is known to regulate the apical-basal polarity of PIN localization in bipolar cells of roots and shoot apices. Here, we provide evidence that the phosphorylation status-mediated PIN polarity switch is widely used to modulate cellular processes in Arabidopsis including multipolar pavement cells （PC） with interdigitated lobes and indentations. The degree of PC interdigitation was greatly reduced either when the FYPP1 gene, which encodes a PP2A called phytochrome- associated serine/threonine protein phosphatase, was knocked out or when the PID gene was overexpressed （35S：：PID）. These genetic modifications caused PIN1 localization to switch from lobe to indentation regions. The PP2A and PID mediated switching of PIN1 localization is strikingly similar to their regulation of the apical-basal polarity switch of PIN proteins in other cells. Our findings suggest a common mechanism for the regulation of PIN1 polarity formation, a fundamental cellular process that is crucial for pattern formation both at the tissue/organ and cellular levels.

背景与目的蛋白质的磷酸化和去磷酸化是肺癌发生的重要机制,而吸烟是导致肺癌发生发展的重要危险因素,本研究旨在探讨蛋白酪氨酸磷酸酶SHP2在非小细胞肺癌（non-small cell lung cancer,NSCLC）和小细胞肺癌（small cell lung cancer,SCLC）肿瘤组织中的表达及其临床意义,并初步探讨不同的吸烟指数与SHP2表达水平的关系及可能机制。方法采用免疫组织化学技术（Invision法）和荧光原位杂交技术（FISH法）检测53例肺癌组织中SHP2的表达和SHP2mRNA的扩增情况。结果 SHP2在15例正常支气管上皮内弱阳性率为80%（亦为总阳性率）;在48例NSCLC中弱阳性率为35.4%,中度阳性率为43.8%,强阳性率为6.2%（总阳性率为85.4%）;在5例SCLC中弱阳性率为0%,中度阳性率为80%,强阳性率为20%（总阳性率为100%）。SHP2在27例非吸烟NSCLC患者肿瘤组织中的弱阳性率为40.7%,中度阳性率为37.4%,强阳性率为3.7%（总阳性率为81.5%）;SHP2在吸烟指数≥400的21例NSCLC患者肿瘤组织中弱阳性率为23.8%,中度阳性率为71.4%,强阳性率为4.7%（总阳性率为100%）。等级计数资料秩和检验结果表明,肺癌组织中SHP2表达的阳性率显著高于正常支气管上皮（P〈0.05）,SCLC中SHP2的阳性率高于NSCLC（P〈0.05）,吸烟指数≥400的NSCLC癌组织中SHP2阳性率高于非吸烟患者（P〈0.05）。结论吸烟NSCLC患者肿瘤组织中SHP2的高表达可能与吸烟相关;SHP2可能在肺癌发生发展中起一定的作用;SHP2可能为肺癌治疗的药物研发提供新思路。

Aim： Increasing evidence shows that mRNAs exert regulatory function along with coding proteins. Recently we report that a hairpin within YAP mRNA 3＇UTR can modulate the Hippo signaling pathway. PTEN is a tumor suppressor, and is mutated in human cancers. In this study we examined whether PTEN mRNA 3＇UTR contained a hairpin structure that could regulate gene regulation at the post- transcriptional level. Methods： The secondary structure of PTEN mRNA 3＇UTR was analyzed using RNAdraw and RNAstructure. Function of hairpin structure derived from the PTEN mRNA 3＇UTR was examined using luciferase reporter assay, RT-PCR and Western blotting. RNA- immunoprecipitation （RIP） assay was used to analyze the interaction between PTEN mRNA and microprocessor Drosha and DGCR8. Endogenous siRNA （esiRNA） derived from PTEN mRNA 3＇UTR was identified by RT-PCR and rt-PCR, and its target genes were predicted using RNAhybrid. Results： A bioinformatics analysis revealed that PTEN mRNA contained a hairpin structure （termed PTEN-sh） within 3＇UTR, which markedly increased the reporter activities of AP-1 and NF-KB in 293T cells. Moreover, treatment with PTEN-sh （1 and 2 μg） dosedependently inhibited the expression of PTEN in human liver L-02 cells. RIP assay demonstrated that the microprocessor Drosha and DGCR8 was bound to PTEN-sh in L-02 cells, leading to the cleavage of PTEN-sh from PTEN mRNA 3＇UTR. In addition, microprocessor Dicer was involved in the processing of PTEN-sh. Interestingly, esiRNA （termed PTEN-sh-3p21） cleaved from PTEN-sh was identified in 293T cells and human liver tissues, which was found to target the mRNA 3＇UTRs of protein phosphatase PPP2CA and PTEN in L-02 cells. Treatment of L-02 or Chang liver cells with PTEN-sh-3p21 （50, 100 nmol/L） promoted the cell proliferation in dose- and time- dependent manners. Conclusion： The endogenous siRNA （PTEN-sh-3p21） cleaved from PTEN-sh within PTEN mRNA 3＇UTR modulates PPP2CA and PTEN at the post-transcriptional level in liver cells.