Cancerous inhibitor of protein phosphatase 2A enhances chemoresistance of gastric cancer cells to oxaliplatin

BACKGROUND Cancerous inhibitor of protein phosphatase 2A(CIP2A)is a newly discovered oncogene.It is an active cell proliferation regulatory factor that inhibits tumor apoptosis in gastric cancer(GC)cells.CIP2A is functionally related to chemoresistance in various types of tumors according to recent studies.The underlying mechanism,however,is unknown.Further,the primary treatment regimen for GC is oxaliplatin-based chemotherapy.Nonetheless,it often fails due to chemoresistance of GC cells to oxaliplatin.AIM The goal of this study was to examine CIP2A expression and its association with oxaliplatin resistance in human GC cells.METHODS Immunohistochemistry was used to examine CIP2A expression in GC tissues and adjacent normal tissues.CIP2A expression in GC cell lines was reduced using small interfering RNA.After confirming the silencing efficiency,3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide tetrazolium and flow cytometry assays were used to evaluate cell proliferation and apoptosis caused by oxaliplatin treatment.Further,the key genes and protein changes were verified using realtime quantitative reverse transcription PCR and Western blotting,respectively,before and after intervention.For bioinformatics analysis,we used the R software and Bioconductor project.For statistical analysis,we used GraphPad Prism 6.0 and the Statistical Package for the Social Sciences software version 20.0(IBM,Armonk,United States).RESULTS A high level of CIP2A expression was associated with tumor size,T stage,lymph node metastasis,Tumor Node Metastasis stage,and a poor prognosis.Further,CIP2A expression was higher in GC cells than in normal human gastric epithelial cells.Using small interfering RNA against CIP2A,we discovered that CIP2A knockdown inhibited cell proliferation and significantly increased GC cell sensitivity to oxaliplatin.Moreover,CIP2A knockdown enhanced oxaliplatin-induced apoptosis in GC cells.Hence,high CIP2A levels in GC may be a factor in chemoresistance to oxaliplatin.In human GC cells,CIP2A regulated protein kinase B phosphorylation,and chemical inhibition of the protein kinase B signaling pathway was significantly associated with increased sensitivity to oxaliplatin.Therefore,the protein kinase B signaling pathway was correlated with CIP2Aenhanced chemoresistance of human GC cells to oxaliplatin.CONCLUSION CIP2A expression could be a novel therapeutic strategy for chemoresistance in GC.

I2PP2A蛋白调控PP2A/Akt信号通路对神经母细胞瘤细胞增殖和凋亡的影响

目的探讨蛋白磷酸酶2A抑制剂-2(protein phosphatase 2A inhibitor-2,I2PP2A)调控PP2A/Akt信号通路对人神经母细胞瘤细胞增殖和凋亡的影响。方法体外培养人神经母细胞瘤SH-SY5Y细胞转染I2PP2A-shRNA干扰质粒及对照质粒后分为siI2PP2A组及siC组。CCK-8、细胞克隆形成实验、细胞周期实验用于检测细胞增殖活性;流式细胞术检测细胞凋亡;Western blot法检测细胞内相关蛋白相对表达量;磷酸酶检测系统试剂盒测定PP2A活性;给予PP2A抑制剂冈田酸(okadaic acid,OA)处理细胞并检测增殖活性及PP2A/Akt信号通路变化。结果与siC组比较,siI2PP2A组48h及72h的吸光度(A)值下降(P<0.01),细胞克隆形成数目显著降低(P<0.01);siC组G_(0)/G_(1)期、S期、G_(2)/M期、细胞凋亡比例分别为43.29%±3.68%、31.76%±2.42%、24.96%±2.34%、1.89%±1.09%,siI2PP2A组为57.00%±3.90%、25.88%±2.06%、17.13%±2.07%、15.18%±5.60%,与siC组比较,siI2PP2A组G_(0)/G_(1)期细胞比例和凋亡细胞比例升高,S期和G_(2)/M期细胞比例下降(P<0.05)。同时,siI2PP2A组较siC组PP2A活性显著增加(P<0.05),CyclinD1、Bcl-2、p-Akt蛋白相对表达量降低(P<0.05),Bax、cleaved-PARP蛋白相对表达水平升高(P<0.01)。进一步给予PP2A抑制剂OA后,可部分恢复siI2PP2A组CyclinD1、Bcl-2、p-Akt、Bax、cleaved-PARP蛋白水平(P<0.05)并逆转下调I2PP2A导致的增殖抑制(P<0.05)。结论下调I2PP2A介导的神经母细胞瘤细胞增殖抑制和凋亡增加可能与PP2A/Akt信号通路密切相关。

微RNA-132-3p靶向第10号染色体缺失的磷酸酶和张力蛋白同源物调控葡萄膜黑色素瘤细胞增殖与凋亡

目的 研究微RNA(miR)-132-3p在葡萄膜黑色素瘤细胞增殖、凋亡中的作用及其作用机制。方法 该研究起止时间为2018年2月至2019年7月。定量聚合酶链反应(qPCR)检测正常葡萄膜上皮细胞ARPE-19和葡萄膜黑色素瘤细胞SP6.5、M23中miR-132-3p表达。SP6.5细胞中转染miR-132-3p干扰质粒(anti-miR-132-3p)、第10号染色体上缺失的磷酸酶和张力蛋白同源物(PTEN)过表达质粒(pcDNA3.1-PTEN)或共转染anti-miR-132-3p和PTEN干扰质粒(si-PTEN),MTT法和流式细胞术分别检测细胞增殖与凋亡,蛋白质印迹法检测PTEN、细胞周期蛋白D1(cyclin D1)、周期素依赖激酶抑制剂p21(P21)、B细胞淋巴瘤-2(Bcl-2)和Bcl-2相关X蛋白(Bax)蛋白表达,生物信息学预测结合双萤光素酶报告实验分析miR-132-3p与PTEN的靶向关系。结果 与ARPE-19细胞相比,SP6.5、M23细胞中miR-132-3p表达量(0.26±0.02比0.94±0.09、0.81±0.08)明显升高(P<0.05)。与anti-miR-132-3p阴性对照(anti-miR-NC)组相比,anti-miR-132-3p组24 h、48 h、72 h的细胞活性(0.51±0.05比0.30±0.03、0.97±0.09比0.45±0.05、1.40±0.14比0.76±0.07)、cyclin D1、Bcl-2蛋白表达量显著降低(P<0.05),细胞凋亡率[(8.03±0.68)%比(21.51±2.06)%]、P21、Bax水平明显提高(P<0.05),与过表达PTEN相同。miR-132-3p与PTEN之间有靶向调控关系。抑制PTEN能逆转抑制miR-132-3p对SP6.5细胞增殖的抑制作用及对细胞凋亡的促进作用。结论 miR-132-3p通过直接靶向PTEN调控葡萄膜黑色素瘤细胞增殖与凋亡。

2型糖尿病新靶点口服药专利分析

目的 分析2型糖尿病新靶点口服药专利概况,为国内新型糖尿病治疗药物的研发方向和专利布局等提供参考。方法以HimmPat数据库中全球专利数据为基础,从专利申请量及授权量、发展趋势、地域分布、主要申请人等多个角度,对葡萄糖激酶激活剂(GKA)、蛋白酪氨酸磷酸酶1B抑制剂(PTP-1B-IN)、11β-羟基类固醇脱氢酶1抑制剂(11β-HSD1-IN)3类2型糖尿病新靶点口服药相关专利进行统计分析。结果与结论 共检索得到GKA类专利1 649件,PTP-1B-IN类专利709件,11β-HSD1-IN类专利592件。全球主要申请主体为各大药企,其掌握了药物化合物的核心专利;其中GKA类药物的研究更成熟,专利申请量更大,企业布局更全面。国内企业、高校和科研院所在PTP-1B-IN领域具有一定的研究优势。国内企业和研究机构可以发挥传统中药资源优势,提升研究实力,可考虑从核心技术挖掘、工艺路线探索、专利布局、产学研合作、构建专利池等方面提高技术竞争力。

HBV Infection Promotes the Occurrence and Development of Hepatocellular Carcinoma through Impairing the Inhibitory Effect of PPP2R5A on MAPK/AKT/WNT Signaling Pathway

Reversible phosphorylation and dephosphorylation play important roles in cell function and cell signal transduction. PPP2R5A (protein phosphatase 2 regulatory subunit B’ alpha) is responsible for specifically regulating the catalytic function, substrate specificity and intracellular localization of the tumor suppressor phosphatase PP2A (serine/threonine protein phosphatase 2A). Therefore, the abnormal expression and function of PPP2R5A may be related to canceration. The aim of this study was to reveal its role in the occurrence and development of hepatocellular carcinoma (HCC). It is hoped that the results of this study can provide guidance for the prevention and treatment of HCC. The results showed that PPP2R5A inhibited the proliferation and metastasis of HCC cells, and acted as a tumor suppressor in HCC cells, but it had no significant effect on cell cycle. Further research found that PPP2R5A exerted tumor suppressor efficacy by inhibiting the MAPK/AKT/WNT signaling pathway. Combined with analysis of clinical tissue samples and TCGA database, it was found that the expression of PPP2R5A in tumor tissues of Chinese HCC patients was down-regulated and significantly correlated with the progression-free survival (PFS) of HCC patients. On the contrary, PPP2R5A showed an up-regulation trend in HCC cases in TCGA database although its effect on PFS was the same with that in Chinese HCC patients. Hepatitis B virus (HBV) infection is the main pathogenic factor of HCC in China. It was found that HBV infection reduced the content of PPP2R5A in cells. It was concluded that HBV inhibited the initiation of the protective mechanism mediated by PPP2R5A, making the occurrence and progress of HCC more “unimpeded”. This conclusion will further reveal the role of PPP2R5A in HBV-induced and HBV-unrelated HCC, therefore, providing clues for the prevention and treatment of the two types of HCC, respectively.

慢病毒介导的shRNA靶向干扰I2PP2A胃癌稳定细胞株的建立

背景与目的:蛋白磷酸酶2A抑制剂-2(inhibitor 2 of protein phosphatase 2A,I2PP2A)在包括胃癌的多种肿瘤中过度表达,提示其可能在胃癌的发生中发挥重要作用。为进一步探讨I2PP2A的功能及其在胃癌发生中的作用,建立稳定抑制I2PP2A基因表达的人胃癌BGC823细胞株。方法:筛选出I2PP2A基因的RNA干扰(RNA interference,RNAi)有效靶序列,合成靶序列的Oligo DNA并构建p GLV2_sh RNA_I2PP2A慢病毒载体,酶切和测序鉴定正确后,经病毒包装,感染BGC823细胞,经嘌呤霉素筛选稳定表达细胞株,通过实时定量PCR(real-time PCR,RT-PCR)和蛋白[质]印迹法(Western blot)鉴定I2PP2A的表达。结果:重组慢病毒质粒经测序鉴定正确;RT-PCR和Western blot证实干扰I2PP2A后,BGC823细胞株中I2PP2A表达水平明显降低,抑制率约为90%。结论:成功构建了I2PP2A sh RNA慢病毒表达载体,建立了稳定抑制I2PP2A基因表达的人胃癌BGC823细胞株,为进一步研究I2PP2A在胃癌发生中的作用提供了可靠的细胞模型。

基于SHP2的抗结直肠癌治疗策略

结直肠癌(CRC)作为威胁人类生命最常见的恶性肿瘤之一,其严重影响了患者的生活质量。含Src同源2结构域的蛋白酪氨酸磷酸酶2 (SHP2)是一种由PTPN11基因编码的非受体酪氨酸磷酸酶,广泛表达于多种组织和细胞中。近年来,SHP2是癌症领域中备受关注的焦点,已经被证实为结直肠癌的促进因子。目前已有的研究表明,肿瘤微环境中,SHP2在调节免疫细胞功能和炎症性结直肠癌中发挥着重要作用;随着SHP2变构抑制剂的出现,SHP2成为了结直肠癌患者潜在的用药靶点,并且SHP2变构抑制剂的临床试验效果已经展现出了显著的抗结直肠癌治疗的优势。本文针对SHP2在结直肠癌中的角色,对SHP2在结构与功能、抗肿瘤微环境中的作用以及SHP2变构抑制剂在结直肠癌中的治疗策略进行综述。

Targeting PP2A for cancer therapeutic modulation

Protein phosphatases play essential roles as negative regulators of kinases and signaling cascades involved in cytoskeletal organization.Protein phosphatase 2A(PP2A)is highly conserved and is the predominant serine/threonine phosphatase in the nervous system,constituting more than 70%of all neuronal phosphatases.PP2A is involved in diverse regulatory functions,including cell cycle progression,apoptosis,and DNA repair.Although PP2A has historically been identified as a tumor suppressor,inhibition of PP2A has paradoxically demonstrated potential as a therapeutic target for various cancers.LB100,a water-soluble,small-molecule competitive inhibitor of PP2A,has shown particular promise as a chemo-and radio-sensitizing agent.Preclinical success has led to a profusion of clinical trials on LB100 adjuvant therapies,including a phase I trial in extensive-stage small-cell lung cancer,a phase I/II trial in myelodysplastic syndrome,a phase II trial in recurrent glioblastoma,and a completed phase I trial assessing the safety of LB100 and docetaxel in various relapsed solid tumors.Herein,we review the development of LB100,the role of PP2A in cancer biology,and recent advances in targeting PP2A inhibition in immunotherapy.

SHP-2对Apo E基因敲除小鼠动脉粥样硬化斑块及其内部巨噬细胞表型的影响

目的观察磷酸酶SHP-2对Apo E基因敲除(Apo E^(-/-))小鼠动脉粥样硬化斑块及其内部巨噬细胞(M_φ)表型的影响。方法将Apo E^(-/-)小鼠(动脉粥样硬化模型小鼠)随机分为实验组和模型组各16只,均给予高脂饲料喂养,同时实验组腹腔注射溶于0.5%DMSO的SHP-2抑制剂PHPS1 3 mg/(kg·d),模型组腹腔注射等量0.5%DMSO,每天注射1次,共16周。用油红O和Movat染色分别评估主动脉整体和主动脉根部斑块面积,天狼星红、免疫组化染色分别检测主动脉根部斑块内胶原、M_φ(galectin-3/MAC-2阳性区域)和平滑肌细胞(β-actin阳性区域),应用实时荧光定量PCR法检测降主动脉中的M1型(i NOS、TNF-α和IL-6)和M2型(IL-10、Arg-1和FIZZ-1)M_φ标志性因子基因。结果实验组主动脉整体和主动脉根部斑块面积小于模型组,但差异无统计学意义。与模型组比较,实验组主动脉根部斑块内M_φ阳性区域减小(P<0.05),平滑肌细胞、胶原成分阳性区域增大(P均<0.05);降主动脉斑块内M1型M_φ标志性因子基因表达降低(P均<0.05),M2型M_φ标志性因子基因表达升高(P均<0.05)。结论磷酸酶SHP-2可抑制Apo E^(-/-)小鼠动脉粥样硬化斑块内M_φ向M2型分化,从而导致斑块不稳定性增加。

Novel and emerging diabetes mellitus drug therapies for the type 2 diabetes patient

Type 2 diabetes mellitus is a metabolic disorder of deranged fat, protein and carbohydrate metabolism resulting in hyperglycemia as a result of insulin resistance and inadequate insulin secretion. Although a wide variety of diabetes therapies is available, yet limited efficacy, adverse effects, cost, contraindications, renal dosage adjustments, inflexible dosing schedules and weight gain significantly limit their use. In addition, many patients in the United States fail to meet the therapeutic HbA1c goal of 【 7% set by the American Diabetes Association. As such new and emerging diabetes therapies with different mechanisms of action hope to address some of these drawbacks to improve the patient with type 2 diabetes. This article reviews new and emerging classes, including the sodium-glucosecotransporter-2 inhibitors, 11β-Hydroxysteroid dehydrogenase type 1 inhibitors, glycogen phosphorylase inhibitors; protein tyrosine phosphatase 1B inhibitors, G Protein-Coupled receptor agonists and glucokinase activators. These emerging diabetes agents hold the promise of providing benefit of glucose lowering, weight reduction, low hypoglycemia risk, improve insulin sensitivity, pancreatic β cell preservation, and oral formulation availability. However, further studies are needed to evaluate their safety profile, cardiovascular effects, and efficacy durability in order to determine their role in type 2 diabetes management.

Structural Insight into the Design on Oleanolic Acid Derivatives as Potent Protein Tyrosine Phosphatase 1B Inhibitors

Oleanolic acid derivatives act as newer protein tyrosine phosphatase 1B （PTP-1B） inhibitors for type 2 diabetes mellitus （T2DM）. In order to understand the structural requirement of PTP-1B inhibitors, 52 oleanolic acid derivatives were divided into a training set （34 compounds） and a test set （18 compounds）. The highly reliable and predictive 3D-QSAR models were constructed by CoMFA, CoMSIA and topomer CoMFA methods, respectively. The results showed that the cross validated coefficient （q2） and non-cross-validated coefficient （R2） were 0.554 and 0.999 in the CoMFA model, 0.675 and 0.971 in the CoMSIA model, and 0.628 and 0.939 in the topomer CoMFA model, which suggests that three models are robust and have good exterior predictive capabilities. Furthermore, ten novel inhibitors with much higher inhibitory potency were designed. Our design strategy was that （i） the electronegative substituents （Cl, -CH2OH, OH and -CH2Cl） were introduced into the double bond of ring C, （ii） the hydrogen bond acceptor groups （C≡N and N atom）, electronegative groups （C≡N, N atom, -COOH and -COOCH3） and bulky substituents （C6H5N） were connected to the C-3 position, which would result in generating potent and selective PTP-1B inhibitors. We expect that the results in this paper have the potential to facilitate the process of design and to develop new potent PTP-1B inhibitors.

DIW1 encoding a cladeⅠPP2C phosphatase negatively regulates drought tolerance by de-phosphorylating TaSnRK1.1 in wheat

Drought seriously impacts wheat production(Triticum aestivum L.),while the exploitation and utilization of genes for drought tolerance are insufficient.Leaf wilting is a direct reflection of drought tolerance in plants.Clade A PP2Cs are abscisic acid(ABA)co-receptors playing vital roles in the ABA signaling pathway,regulating drought response.However,the roles of other clade PP2Cs in drought tolerance,especially in wheat,remain largely unknown.Here,we identified a gain-of-function drought-induced wilting 1(DIW1)gene from the wheat Aikang 58 mutant library by map-based cloning,which encodes a cladeⅠprotein phosphatase 2C(TaPP2C158)with enhanced protein phosphatase activity.Phenotypic analysis of overexpression and CRISPR/Cas9 mutant lines demonstrated that DIW1/TaPP2C158 is a negative regulator responsible for drought resistance.We found that TaPP2C158 directly interacts with TaSnRK1.1 and de-phosphorylates it,thus inactivating the TaSnRK1.1–Ta AREB3 pathway.TaPP2C158 protein phosphatase activity is negatively correlated with ABA signaling.Association analysis suggested that C-terminal variation of TaPP2C158 changing protein phosphatase activity is highly correlated with the canopy temperature,and seedling survival rate under drought stress.Our data suggest that the favorable allele with lower phosphatase activity of TaPP2C158 has been positively selected in Chinese breeding history.This work benefits us in understanding the molecular mechanism of wheat drought tolerance,and provides elite genetic resources and molecular markers for improving wheat drought tolerance.

Discovery of TK-642 as a highly potent,selective,orally bioavailable pyrazolopyrazine-based allosteric SHP2 inhibitor

Src homology-2-containing protein tyrosine phosphatase 2(SHP2)is a promising therapeutic target for cancer therapy.In this work,we presented the structure-guided design of 5,6-fused bicyclic allosteric SHP2 inhibitors,leading to the identification of pyrazolopyrazine-based TK-642 as a highly potent,selective,orally bioavailable allosteric SHP2 inhibitor(SHP2WT IC_(50)=2.7 nmol/L)with favorable pharmacokinetic profiles(F=42.5%;t_(1/2)=2.47 h).Both dual inhibition biochemical assay and docking analysis indicated that TK-642 likely bound to the“tunnel”allosteric site of SHP2.TK-642 could effectively suppress cell proliferation(KYSE-520 cells IC_(50)=5.73μmol/L)and induce apoptosis in esophageal cancer cells by targeting the SHP2-mediated AKT and ERK signaling pathways.Additionally,oral administration of TK-642 also demonstrated effective anti-tumor effects in the KYSE-520 xenograft mouse model,with a T/C value of 83.69%.Collectively,TK-642 may warrant further investigation as a promising lead compound for the treatment of esophageal cancer.

Protein phosphatases and chromatin modifying complexes in the inflammatory cascade in acute pancreatitis

Acute pancreatitis is an inflammation of the pancreas that may lead to systemic inflammatory response syndrome and death due to multiple organ failure. Acinar cells, together with leukocytes, trigger the inflammatory cascade in response to local damage of the pancreas. Amplification of the inflammatory cascade requires up-regulation of proinflammatory cytokines and this process is mediated not only by nuclear factor κB but also by chromatinmodifying complexes and chromatin remodeling. Among the different families of histone acetyltransferases, the p300/CBP family seems to be particularly associated with the inflammatory process. cAMP activates gene expression via the cAMP-responsive element (CRE) and the transcription factor CRE-binding protein (CREB). CREB can be phosphorylated and activated by different kinases, such as protein kinase A and MAPK, and then it recruits the histone acetyltransferase co-activator CREB-binding protein (CBP) and its homologue p300. The recruitment of CBP/p300 and changes in the level of histone acetylation are required for transcription activation. Transcriptional repression is also a dynamic and essential mechanism of down-regulation of genes for resolution of inflammation, which seems to be mediated mainly by protein phosphatases (PP1, PP2A and MKP1) and histone deacetylases(HDACs) .Class HDACs are key transcriptional regulators whose activities are controlled via phosphorylationdependent nucleo/cytoplasmic shuttling. PP2A is responsible for dephosphorylation of class HDACs, triggeringnuclear localization and repression of target genes, whereas phosphorylation triggers cytoplasmic localization leading to activation of target genes. The potential benefit from treatment with phosphodiesterase inhibitors and histone deacetylase inhibitors is discussed.

含Src同源2结构域蛋白酪氨酸磷酸酶2抑制剂在肿瘤靶向和免疫治疗中的应用进展

由PTPN11基因编码的含Src同源2结构域蛋白酪氨酸磷酸酶2(Src homology 2 domain-containing protein tyrosine phosphatase, SHP2)是细胞关键调节因子蛋白酪氨酸磷酸酶(protein tyrosine phosphatase, PTP)家族的一员,在多种恶性肿瘤中高表达。一方面,SHP2通过介导RAS-MAPK,PI3K-AKT和JAK-STAT等信号通路调节肿瘤细胞的生理功能。另一方面,在肿瘤微环境中,SHP2与免疫抑制受体[如程序性死亡受体1(programmed death-1,PD-1)、细胞毒性T淋巴细胞相关抗原4(cytotoxic T lymphocyte-associated antigen-4,CTLA-4)等]结合,调节免疫细胞的功能,造成免疫微环境的抑制性。因此,SHP2在肿瘤中具有调节肿瘤细胞和免疫微环境的双重功能,提示其为极具价值的肿瘤治疗靶点。近年来,大量具有成药潜力的SHP2抑制剂进入临床试验,为肿瘤靶向治疗提供新的可能。目前SHP2抑制剂的研究已经取得一定成果,但仍存在较多耐药性、非特异性和毒性等问题。因此,需进一步研究SHP2抑制剂的成药性和靶向策略。本文对SHP2参与信号通路的调控机制和其在肿瘤和免疫微环境中的作用进行总结,并对SHP2抑制剂及其临床研究进展进行综述。

非受体型蛋白酪氨酸磷酸酶2在肿瘤免疫中的研究进展

非受体型蛋白酪氨酸磷酸酶2 (protein tyrosine phosphatase non-receptor type 2, PTPN2)作为蛋白酪氨酸磷酸酶家族成员,通过催化去磷酸化反应,在细胞信号传递中起着重要作用。PTPN2过表达与多种癌症患者预后不良密切相关,而其缺失能有效抑制肿瘤的增长、迁移,并促进细胞凋亡。在免疫系统中,PTPN2在T细胞功能以及肿瘤微环境的调节中起着关键作用。因此,PTPN2在肿瘤发展过程和肿瘤免疫中扮演了重要角色,是一个潜在抗肿瘤新靶点。目前,有多个PTPN2抑制剂或降解剂被发现,其中两个抑制剂已进入临床I期试验阶段。该文综述了PTPN2的结构特性、在抗肿瘤免疫中的功能与应用,以及当前对其抑制剂和降解剂在肿瘤治疗中的研究进展。

Reciprocal regulation between the negative regulator PP2CG1 phosphatase and the positive regulator OST1 kinase confers cold response in Arabidopsis

Protein phosphorylation and dephosphorylation have been reported to play important roles in plant cold responses.In addition,phospho-regulatory feedback is a conserved mechanism for biological processes and stress responses in animals and plants.However,it is less well known that a regulatory feedback loop is formed by the protein kinase and the protein phosphatase in plant responses to cold stress.Here,we report that OPEN STOMATA 1(OST1)and PROTEIN PHOSPHATASE 2C G GROUP 1(PP2CG1)reciprocally regulate the activity during the cold stress response.The interaction of PP2CG1 and OST1 is inhibited by cold stress,which results in the release of OST1 at the cytoplasm and nucleus from suppression by PP2CG1.Interestingly,cold-activated OST1 phosphorylates PP2CG1 to suppress its phosphatase activity,thereby amplifying cold signaling in plants.Mutations of PP2CG1 and its homolog PP2CG2 enhance freezing tolerance,whereas overexpression of PP2CG1 decreases freezing tolerance.Moreover,PP2CG1 negatively regulates protein levels of C-REPEAT BINDING FACTORs(CBFs)under cold stress.Our results uncover a phosphor/dephosphor-regulatory feedback loop mediated by PP2CG1 phosphatase and OST1 protein kinase in plant cold responses.

Axonal growth inhibitors and their receptors in spinal cord injury:from biology to clinical translation

Axonal growth inhibitors are released during traumatic injuries to the adult mammalian central nervous system, including after spinal cord injury. These molecules accumulate at the injury site and form a highly inhibitory environment for axonal regeneration. Among these inhibitory molecules, myelinassociated inhibitors, including neurite outgrowth inhibitor A, oligodendrocyte myelin glycoprotein, myelin-associated glycoprotein, chondroitin sulfate proteoglycans and repulsive guidance molecule A are of particular importance. Due to their inhibitory nature, they represent exciting molecular targets to study axonal inhibition and regeneration after central injuries. These molecules are mainly produced by neurons, oligodendrocytes, and astrocytes within the scar and in its immediate vicinity. They exert their effects by binding to specific receptors, localized in the membranes of neurons. Receptors for these inhibitory cues include Nogo receptor 1, leucine-rich repeat, and Ig domain containing 1 and p75 neurotrophin receptor/tumor necrosis factor receptor superfamily member 19(that form a receptor complex that binds all myelin-associated inhibitors), and also paired immunoglobulin-like receptor B. Chondroitin sulfate proteoglycans and repulsive guidance molecule A bind to Nogo receptor 1, Nogo receptor 3, receptor protein tyrosine phosphatase σ and leucocyte common antigen related phosphatase, and neogenin, respectively. Once activated, these receptors initiate downstream signaling pathways, the most common amongst them being the Rho A/ROCK signaling pathway. These signaling cascades result in actin depolymerization, neurite outgrowth inhibition, and failure to regenerate after spinal cord injury. Currently, there are no approved pharmacological treatments to overcome spinal cord injuries other than physical rehabilitation and management of the array of symptoms brought on by spinal cord injuries. However, several novel therapies aiming to modulate these inhibitory proteins and/or their receptors are under investigation in ongoing clinical trials. Investigation has also been demonstrating that combinatorial therapies of growth inhibitors with other therapies, such as growth factors or stem-cell therapies, produce stronger results and their potential application in the clinics opens new venues in spinal cord injury treatment.

Inhibitory effects of polyphyllins I and VII on human cisplatin-resistant NSCLC via p53 upregulation and CIP2A/AKT/mTOR signaling axis inhibition

Cancerous inhibitor of protein phosphatase 2A(CIP2A) is a human oncoprotein that is overexpressed in multiple kinds of cancers including non-small cell lung cancer(NSCLC). CIP2A plays an ’oncogenic nexus’ to participate in the tumorigenesis and chemoresistance in several cancer types. AKT and m TORC1 overactivation are detected in NSCLC and many other cancers. Previous studies found that the CIP2A/AKT/m TOR pathway controls cell growth, apoptosis, autophagy process. Polyphyllin I(PPI) and polyphyllin VII(PPVII) are natural components extracted from Paris polyphylla that display anti-cancer properties. In the present study, we investigated whether PPI and PPVII can be used in the cisplatin(DDP)-resistant human NSCLC cell line A549/DDP. Results demonstrated that PPI and PPVII treatment significantly suppressed A549/DDP cell proliferation, migration, invasion and EMT, induced apoptosis and autophagy. Further examination of the mechanism revealed that the PPI and PPVII significantly upregulated the p53, induced caspase-dependent apoptosis and suppressed the CIP2A/AKT/m TOR pathway. The activation of autophagy was mediated through PPI and PPVII induced inhibition of m TOR. We propose that PPI and PPVII might be developed as candidate drugs for DDP-resistant NSCLC.

PP2A interacts with KATANIN to promote microtubule organization and conical cell morphogenesis

The organization of the microtubule cytoskeleton is critical for cell and organ morphogenesis.The evolutionarily conserved microtubule-severing enzyme KATANIN plays critical roles in microtubule organization in the plant and animal kingdoms.We previously used conical cell of Arabidopsis thaliana petals as a model system to investigate cortical microtubule organization and cell morphogenesis and determined that KATANIN promotes the formation of circumferential cortical microtubule arrays in conical cells.Here,we demonstrate that the conserved protein phosphatase PP2A interacts with and dephosphorylates KATANIN to promote the formation of circumferential cortical microtubule arrays in conical cells.KATANIN undergoes cycles of phosphorylation and dephosphorylation.Using co-immunoprecipitation coupled with mass spectrometry,we identified PP2A subunits as KATANIN-interacting proteins.Further biochemical studies showed that PP2 A interacts with and dephosphorylates KATANIN to stabilize its cellular abundance.Similar to the katanin mutant,mutants for genes encoding PP2A subunits showed disordered cortical microtubule arrays and defective conical cell shape.Taken together,these findings identify PP2A as a regulator of conical cell shape and suggest that PP2A mediates KATANIN phospho-regulation during plant cell morphogenesis.