MAPK级联途径在植物信号转导中的研究进展

促分裂原活化蛋白激酶(mitogen-activated protein kinase,MAPK)在植物的胁迫反应应答方面占有重要地位.本文就MAPK的基本组成、分类、激发子和两种可能的机理的最新进展作了综述.并介绍了近年来此领域中的研究方法,包括MAPK活性测定的方法、免疫沉淀法、酵母双杂交、基因突变、RNA干涉和网络模式法.     

α1, 2-岩藻糖转移酶基因转导对人卵巢癌细胞RMG-I p38MAPK信号通路介导的凋亡的影响

以α1,2-岩藻糖转移酶基因转染前后卵巢癌细胞RMG-I、RMG-I-H为细胞模型,用细胞免疫荧光方法检测转染前后细胞p38MAPK和p-p38MAPK的细胞内定位,RT-PCR和Western blot方法从mRNA和蛋白质两个水平检测转染前后细胞p38MAPK表达的变化;以兔抗人IgG抗体处理组为对照,分别利用RT-PCR和Western blot方法检测Lewisy单克隆抗体处理前后RMG-I-H细胞p38MAPK mRNA和蛋白质表达水平的变化;以0.1%DMSO为对照,用流式细胞仪(FCM)检测p38MAPK特异性抑制剂SB203580处理后RMG-I-H凋亡比率的变化,并利用RT-PCR和Western blot方法检测caspase-3的mRNA和蛋白质水平的变化;用RT-PCR方法检测卡铂和SB203580处理后p38MAPK及caspase-3表达的变化.结果表明,RMG-I与RMG-I-H的p38MAPK蛋白主要定位在细胞质,p-p38MAPK蛋白定位在细胞核,转染后p38MAPK的mRNA水平明显高于转染前(P<0.05);Lewisy单克隆抗体处理后RMG-I-H细胞p38MAPK m...     

植物MAPK C族基因的研究进展

促分裂原活化蛋白激酶(MAPK)是一类丝氨酸/苏氨酸蛋白激酶,它包括MAPKKK、MAPKK和MAPK等3组,它们共同构成MAPK级联系统.MAPK级联系统通过参与蛋白质磷酸化作用传递和放大信号,调控下游基因的表达,最终引起植物的一系列生理反应.MAPK的基因包括A族、B族、C族和D族4类.就C族MAPK基因的种类和功能,以及近几年来对C族MAPK基因的研究方法作综述.     

阿托伐他汀对人肾小球系膜细胞增殖、TGF-β1mRNA和p38MAPK表达的影响

目的观察阿托伐他汀(atorv)对氧化低密度脂蛋白(ox-LDL)诱导的人肾小球系膜细胞(HGMCs)增殖和转化生长因子β1(TGF-β1)mRNA及丝裂原活化蛋白激酶(p38MAPK)蛋白表达的影响。方法在体外培养HG-MCs,用MTT法检测细胞增殖,用半定量RT-PCR法检测细胞TGF-β1 mRNA表达,用Western blot法检测细胞p38MAPK蛋白合成。结果1.Ox-LDL(80μg/ml)刺激系膜细胞增殖;2.Ox-LDL(10μg/ml-80μg/ml)以浓度依赖的方式增加HGMCs TGF-β1 mRNA和p38MAPK蛋白表达,3.Atovastatin(6μg-12μg/ml)抑制系膜细胞增殖,降低ox-LDL引起的TGF-β1 mRNA表达上调,抑制p38MAPK信号途径激活。结论阿托伐他汀可能通过对抗p38MAPK信号通路,减少TGFβ1分泌,抑制ox-LDL引起的肾小球系膜细胞增殖,预防和治疗伴有血脂异常的糖尿病肾脏病变。     

间歇性低压低氧预处理对脑缺血大鼠海马p-p38 MAPK表达的影响

目的:本文旨在观察间歇性低压低氧(IH)预处理诱导脑缺血耐受过程中,大鼠海马CA1区磷酸化p38MAPK(p-p38 MAPK)的表达以及表达p-p38 MAPK的星形胶质细胞数量。方法:将30只健康雄性Wistar大鼠随机分为6组(n=5):假手术(sham)0 min组、IH+sham 0 min组、sham 7 d组、IH+sham 7 d组、损伤性缺血(Is)7 d组、IH+Is 7 d组。通过硫堇染色对各组大鼠海马CA1区锥体神经元进行神经病理学评价;免疫组织化学染色观察pp38 MAPK的表达;免疫荧光双标法观察表达p-p38 MAPK的星形胶质细胞数量。结果:IH预处理可以诱导脑缺血耐受,同时引起大鼠海马CA1区p-p38 MAPK的表达明显增加,且上调星形胶质细胞中p-p38 MAPK的表达。结论:低压低氧预处理促大鼠海马CA1区锥体神经元和星形胶质细胞中p-p38MAPK上调可能是IH预处理保护脑的一个途经。     

球孢白僵菌FUS3/KSS1类MAPK同源基因(BbMPK1)的克隆及特征分析

根据几种丝状真菌FUS3/KSS1类MAPK的保守序列设计简并引物,从昆虫病原真菌球孢白僵菌中扩增出MAPK基因的部分片段,进而利用YADE法延伸该片段的上、下游邻接序列,获得MAPK基因的全长序列,命名为BbMPK1。用3′RACE扩增出BbMPK1的全长cDNA序列,该序列含有一个1071bp的ORF,编码356个氨基酸的多肽,推测分子量为41.2kDa,等电点为6.61。BbMPK1含有11个MAPK共有的蛋白激酶区域和1个MAPK激酶作用的磷酸化位点区域(TEY),其氨基酸序列与丝状真菌的TMKA、PMK1、CMK1、FMK1和BMP1等MAPK高度同源。系统聚类结果表明,BbMPK1属于酵母FUS3/KSS1类MAPK。Southern杂交表明,BbMPK1在球孢白僵菌基因组中以单拷贝形式存在。RT-PCR分析表明BbMPK1在分生孢子休眠阶段、萌发阶段和菌丝生长时期均表达。研究结果为阐明酵母FUS3/KSS1类MAPK同源基因在球孢白僵菌中的作用奠定了基础。     

慢性间歇低氧对幼鼠脑区p38MAPK的影响

目的：研究慢性间歇低氧对幼鼠部分脑区p38MAPK的影响。方法：SPF级健康雄性SD幼鼠（3-4周龄）50只,随机分为5组（n=10）：间歇低氧2周组（2IH组）、间歇低氧4周组（4IH组）、间歇低氧4周后恢复组（4F组）、对照2周组（2C组）和对照4周组（4C组）。建立慢性间歇低氧幼鼠模型,以RT-PCR法和Westemblot法分别测幼鼠海马及前额叶皮层p38MAPKmRNA和磷酸化p38MAPK（p-p38）蛋白的表达。结果：21H、4IH和4F组幼鼠海马、前额叶皮层的p38MAPK mRNA及p-p38蛋白均明显高于相应对照组（P均〈0．05）。结论：慢性间歇低氧可激活幼鼠部分脑区D38MAPK。     

丝裂原活化蛋白激酶15纳米抗体的制备及其在B16-F10黑素瘤细胞生长过程中的抑制作用

丝裂原活化蛋白激酶15 (mitogen-activated protein kinase 15,MAPK15),又称ERK7或ERK8,是MAPK家族的非典型新成员。MAPK15不同程度地促进不同肿瘤细胞的增殖、迁移、自噬等细胞活动。本研究以MAPK15为靶点,筛选特异性的MAPK15纳米抗体,评估其是否能够作为免疫组织化学和Western印迹中的一抗用于其抗原表达的检测,并探究该纳米抗体在B16-F10黑色素瘤细胞中的作用。通过噬菌体展示技术从B16-F10黑色素瘤细胞纳米抗体文库中进行筛选,得到1株MAPK15特异性纳米抗体,命名为MAPK15-VHH;将该菌株构建原核表达载体,进行优化诱导表达条件时发现,0.6 nmol/L IPTG,15℃,100 r/min条件下该纳米抗体的上清表达量最高。通过竞争ELISA法检测MAPK15-VHH的亲和力,结果显示,该抗体K_D值为0.9829。通过Western印迹和免疫组织化学检测脑组织中MAPK15在蛋白质水平的表达量及分布情况,结果表明,MAPK15-VHH可与组织中的MAPK15结合,用于检测MAPK15蛋...     

LOX-1在D-葡萄糖诱导人肾小球系膜细胞表达TGF-β1中的作用

目的探讨血凝素样氧化低密度脂蛋白受体1（LOX-1）在D-葡萄糖诱导人肾小球系膜细胞表达转化生长因子β1（TGF-β1）中的作用。方法在体外培养人肾小球系膜细胞,在不同时间加入不同浓度的D-葡萄及LOX-1特异性阻滞剂JTX92,用半定量RT-PCR法检测LOX-1和TGF-β1基因表达的相对含量,用Western blot法检测p38 MAPK蛋白质的相对含量,用酶联免疫吸附法（ELISA）检测细胞培养液中TGF-β1浓度。结果D-葡萄糖以时间和浓度依赖的方式增加细胞内LOX-1和TGF-β1 mRNA表达和培养液中TGF-β1浓度,同时也以时间和浓度依赖的方式增加p38 MAPK的表达,JTX92可以明显抑制LOX-1、TGF-β1和p38 MAPK的表达。结论高浓度D-葡萄糖可能通过上调LOX-1的表达,激活细胞内的p38 MAPK信号传递途径,促使人肾小球系膜细胞合成并分泌大量TGF-β1,参与糖尿病肾病的发生发展。     

球孢白僵菌FUS3／KSS1类MAPK同源基（BbMPK1）的克隆及特征分析

根据几种丝状真菌FUS3／KSS1类MAPK的保守序列设计简并引物,从昆虫病原真菌球孢白僵菌中扩增出MAPK基因的部分片段,进而利用YADE法延伸该片段的上、下游邻接序列,获得MAPK基因的全长序列,命名为BbMPK1。用3’RACE扩增出BbMPK1的全长cDNA序列,该序列含有一个1071bp的ORF,编码356个氨基酸的多肽,推测分子量为41．2kDa,等电点为6．61。BbMPK1含有11个MAPK共有的蛋白激酶区域和1个MAPK激酶作用的磷酸化位点区域(TEY),其氨基酸序列与丝状真菌的TMKA、PMK1、CMK1、FMK1和BMP1等MAPK高度同源。系统聚类结果表明,BbMPK1属于酵母FUS3／KSS1类MAPK。Southern杂交表明,BbMPK1在球孢白僵菌基因组中以单拷贝形式存在。RT-PCR分析表明BbMPK1在分生孢子休眠阶段、萌发阶段和菌丝生长时期均表达。研究结果为阐明酵母FUS3／KSS1类MAPK同源基因在球孢白僵菌中的作用奠定了基础。     

Phosphorylation of caldesmon

The phosphorylation of caldesmon was studied to determine if kinase activity reflected either an endogenous kinase or caldesmon itself. Titration of kinase activity with calmodulin yielded maximum activity at substoichiometric ratios of calmodulin/caldesmon. The sites of phosphorylation on caldesmon for calcium/calmodulin-dependent protein kinase II and endogenous kinase were the same, but distinct from protein kinase C sites. Phosphorylation in the presence of Ca2+ and calmodulin resulted in a subsequent increase of endogenous kinase activity in the absence of Ca2+. These results suggest that caldesmon is not a protein kinase and that kinase activity in caldesmon preparations is due to calcium/calmodulin-dependent protein kinase II.     

Phosphorylation and regulation of choline kinase from Saccharomyces cerevisiae by protein kinase A

The CKI1-encoded choline kinase (ATP:choline phosphotransferase, EC 2.7.1.32) from Saccharomyces cerevisiae was phosphorylated in vivo on multiple serine residues. Activation of protein kinase A activity in vivo resulted in a transient increase in the phosphorylation of choline kinase. This phosphorylation was accompanied by a stimulation in choline kinase activity. In vitro, protein kinase A phosphorylated choline kinase on a serine residue with a stoichiometry (0.44 mol of phosphate/mol of choline kinase) consistent with one phosphorylation site/choline kinase subunit. The major phosphopeptide derived from the enzyme phosphorylated in vitro by protein kinase A was common to one of the major phosphopeptides derived from the enzyme phosphorylated in vivo. Protein kinase A activity was dose- and time-dependent and dependent on the concentrations of ATP (Km 2.1 microM) and choline kinase (Km 0.12 microM). Phosphorylation of choline kinase with protein kinase A resulted in a stimulation (1.9-fold) in choline kinase activity whereas alkaline phosphatase treatment of choline kinase resulted in a 60% decrease in choline kinase activity. The mechanism of the protein kinase A-mediated stimulation in choline kinase activity involved an increase in the apparent Vmax values with respect to ATP (2.6-fold) and choline (2.7-fold). Overall, the results reported here were consistent with the conclusion that choline kinase was regulated by protein kinase A phosphorylation.     

Phosphorylation of the yeast choline kinase by protein kinase C. Identification of Ser25 and Ser30 as major sites of phosphorylation

The Saccharomyces cerevisiae CKI1-encoded choline kinase catalyzes the committed step in phosphatidylcholine synthesis via the Kennedy pathway. The enzyme is phosphorylated on multiple serine residues, and some of this phosphorylation is mediated by protein kinase A. In this work we examined the hypothesis that choline kinase is also phosphorylated by protein kinase C. Using choline kinase as a substrate, protein kinase C activity was dose- and time-dependent and dependent on the concentrations of choline kinase (K(m) = 27 microg/ml) and ATP (K(m) = 15 microM). This phosphorylation, which occurred on a serine residue, was accompanied by a 1.6-fold stimulation of choline kinase activity. The synthetic peptide SRSSSQRRHS (V5max/K(m) = 17.5 mm(-1) micromol min(-1) mg(-1)) that contains the protein kinase C motif for Ser25 was a substrate for protein kinase C. A Ser25 to Ala (S25A) mutation in choline kinase resulted in a 60% decrease in protein kinase C phosphorylation of the enzyme. Phosphopeptide mapping analysis of the S25A mutant enzyme confirmed that Ser25 was a protein kinase C target site. In vivo the S25A mutation correlated with a decrease (55%) in phosphatidylcholine synthesis via the Kennedy pathway, whereas an S25D phosphorylation site mimic correlated with an increase (44%) in phosphatidylcholine synthesis. Although the S25A (protein kinase C site) mutation did not affect the phosphorylation of choline kinase by protein kinase A, the S30A (protein kinase A site) mutation caused a 46% reduction in enzyme phosphorylation by protein kinase C. A choline kinase synthetic peptide (SQRRHSLTRQ) containing Ser30 was a substrate (V(max)/K(m) = 3.0 mm(-1) micromol min(-1) mg(-1)) for protein kinase C. Comparison of phosphopeptide maps of the wild type and S30A mutant choline kinase enzymes phosphorylated by protein kinase C confirmed that Ser30 was also a target site for protein kinase C.     

Influence of choline and ethanolamine administration on choline and ethanolamine phosphorylating activities of mouse liver and kidney.

The administration of ethanolamine to adult male mice resulted in a significant increase in ethanolamine kinase activity in liver and kidney. Similarly, choline administration resulted in a significant increase in choline kinase activity in liver and kidney. The administration of ethanolamine resulted in enhancement of choline kinase activity concomitantly with ethanolamine kinase activity in liver and kidney. The administration of choline, however, did not result in any significant increase in ethanolamine kinase activity in liver or kidney. Cycloheximide administration along with choline-ethanolamine prevented the increase in kinase activity in liver and kidney. The results obtained have been discussed in relation to the regulatory role of choline kinase and ethanolamine kinase by de novo synthesis in response to enhanced substrate concentration, the secondary nature of choline kinase induction on ethanolamine administration, and possible distinction between choline kinase and ethanolamine kinase.     

Activation of the MAP kinase pathway by the protein kinase raf.

Both MAP kinases and the protein kinase p74raf-1 are activated by many growth factors in a c-ras-dependent manner and by oncogenic p21ras. We were therefore interested in determining the relationship between MAP kinases and raf. The MAP kinase ERK2 is activated by expression of oncogenically activated raf, independently of cellular ras. Overexpressed p74raf-1 potentiates activation of ERK2 by EGF and TPA. MAP kinase kinase inactivated by phosphatase 2A treatment is phosphorylated and reactivated by incubation with p74raf-1 immunoprecipitated from phorbol ester-treated cells. We conclude that raf protein kinase is upstream of MAP kinases and is either a MAP kinase kinase kinase or a MAP kinase kinase kinase kinase.     

Regulation of ultraviolet B-induced phosphorylation of histone H3 at serine 10 by Fyn kinase

Ultraviolet B (UVB) induces phosphorylation of histone H3 at serine 10, and mitogen-activated protein kinases are involved in this signal transduction pathway. Here we provide evidence that Fyn kinase, a member of the Src kinase family, is involved in the UVB-induced phosphorylation of histone H3 at serine 10. UVB distinctly increased Fyn kinase activity and phosphorylation. Fyn kinase inhibitors 4-amino-5-(4-chlorophenyl)-7(t-butyl)pyrazol(3,4-d)pyramide and leflunomide, an Src kinase inhibitor, suppressed both UVB-induced phosphorylation of histone H3 at serine 10 and Fyn kinase activity and phosphorylation. UVB-induced phosphorylation of histone H3 at serine 10 was blocked by either a dominant-negative mutant of Fyn (DNM-Fyn) kinase or small interfering RNA of Fyn kinase. UVB-induced phosphorylation and activities of ERKs and protein kinase B/Akt were markedly inhibited by DNM-Fyn kinase. However, DNM-Fyn kinase did not inhibit UVB-induced phosphorylation of p38 MAPK or c-Jun N-terminal kinases. Active Fyn kinase phosphorylated histone H3 at serine 10 in vitro, and the phosphorylated Fyn kinase could translocate into the nucleus of HaCaT cells. These results indicate that Fyn kinase plays a key role in the UVB-induced phosphorylation of histone H3 at serine 10.     

Effect of a sunflower oil-supplemented diet on protein kinase activities of rat liver plasma membranes.

1. The effect of a sunflower oil-enriched diet on plasma membrane-bound protein kinase C, protein kinase A, casein and tyrosine kinase activities was studied. 2. The diet induced an increase in the content of linoleic acid and a decrease in the content of palmitic acid. The anisotropy parameter (rs) of the fluorescence probe DPH and SDPH decreased strongly in the experimental group. 3. Protein kinase C was stimulated more than two times. Tyrosine kinase, protein kinase A and casein kinase activities were increased by 65, 57 and 40%, respectively. 4. We suggest that a more fluid lipid environment favours higher plasma membrane-bound protein kinase activities.     

Citron kinase,a Rho-dependent kinase,induces di-phosphorylation of regulatory light chain of myosin II

Citron kinase is a Rho-effector protein kinase that is related to Rho-associated kinases of ROCK/ROK/Rho-kinase family. Both ROCK and citron kinase are suggested to play a role in cytokinesis. However, no substrates are known for citron kinase. We found that citron kinase phosphorylated regulatory light chain (MLC) of myosin II at both Ser-19 and Thr-18 in vitro. Unlike ROCK, however, citron kinase did not phosphorylate the myosin binding subunit of myosin phosphatase, indicating that it does not inhibit myosin phosphatase. We found that the expression of the kinase domain of citron kinase resulted in an increase in MLC di-phosphorylation. Furthermore, the kinase domain was able to increase di-phosphorylation and restore stress fiber assembly even when ROCK was inhibited with a specific inhibitor, Y-27632. The expression of full-length citron kinase also increased di-phosphorylation during cytokinesis. These observations suggest that citron kinase phosphorylates MLC to generate di-phosphorylated MLC in vivo. Although both mono- and di-phosphorylated MLC were found in cleavage furrows, di-phosphorylated MLC showed more constrained localization than did mono-phosphorylated MLC. Because citron kinase is localized in cleavage furrows, citron kinase may be involved in regulating di-phosphorylation of MLC during cytokinesis.     

Biosynthesis and posttranslational modifications of protein kinase C in human breast cancer cells

Several forms of protein kinase C with molecular masses of 74-, 77-, and 80-kDa were detected in subcellular fractions of human breast cancer MDA-MB-231 cells which express the alpha-type protein kinase C. Several lines of evidence indicated that the 74-kDa is the precursor of the 77- and 80-kDa protein kinase C forms. (i) Pulse-labeling experiments revealed that protein kinase C is synthesized on membranes as a 74-kDa protein that can be chased into the 77- and the 80-kDa protein kinase C forms. (ii) The primary translation product of protein kinase C displayed an apparent molecular size of 74-kDa as determined by in vitro translation of poly(A)+ RNA from MDA-MB-231 cells. (iii) Incubation with serine/threonine-specific protein phosphatases (potato acid phosphatase and phosphatase 1 or 2A) resulted in the complete dephosphorylation of the 77-kDa to the 74-kDa protein kinase C form. Protein kinase C appears to be synthesized in membranes as an unphosphorylated and presumably inactive 74-kDa form that is converted into the active 77- and 80-kDa protein kinase C by post-translational modification involving at least two phosphorylation steps. The first phosphorylation is probably achieved by a specific, yet unidentified, "protein kinase C kinase" since the 74-kDa protein kinase C species did not undergo autophosphorylation and was neither a substrate for the purified protein kinase C, S6 kinase, phosphorylase kinase, casein kinase II, nor for the catalytic subunit of cAMP-dependent protein kinase. Except for phosphorylase kinase and the catalytic subunit of the cAMP-dependent protein kinase, phosphorylation of the 77-kDa protein kinase C form with purified protein kinase C (autophosphorylation), S6 kinase or casein kinase II shifted the molecular mass of the 77-kDa protein kinase C to 80-kDa. Prolonged exposure of MDA-MB-231 cells to phorbol 12-myristate 13-acetate not only leads to a complete down-regulation of protein kinase C activity but also to an accumulation of 74-kDa protein kinase C due to a retarded conversion of the 74-kDa into the 77- and 80-kDa protein kinase C forms in these cells. Our data indicate that tumor promoters additionally interfere with the posttranslational processing that converts the 74-kDa protein kinase C precursor into the 77- and 80-kDa forms of the enzyme.     

The relationship between calmodulin binding and phosphorylation of smooth muscle myosin kinase by the catalytic subunit of 3':5' cAMP-dependent protein kinase

Smooth muscle myosin light chain kinase, a calmodulin-dependent enzyme, binds 1 mol of calmodulin/mol of kinase in the presence of calcium (Adelstein, R. S., and Klee, C. B. (1981) J. Biol. Chem. 256, in press. This enzyme is a substrate for cAMP-dependent protein kinase whether or not calmodulin is bound. When calmodulin is not bound to myosin kinase, protein kinase incorporates phosphate into two sites in myosin kinase. Under these circumstances, phosphorylation markedly lowers the rate of myosin kinase activity. The decrease in myosin kinase activity is due to a 10-20-fold increase in the amount of calmodulin necessary for 50% activation of kinase activity. The effect of phosphorylation on the activity of myosin kinase can be reversed by dephosphorylation using a purified phosphatase (Pato, M. D., and Adelstein, R. S. (1980) J. Biol. Chem. 255, 6535-6538) isolated from smooth muscle. When calmodulin is bound to myosin kinase, phosphate is incorporated into a single site with no effect on myosin kinase activity. The presence of at least two sites that can be phosphorylated in myosin kinase was confirmed by tryptic digestion of denatured myosin kinase.