Evidence for negative control in protein kinase C substrate specificity

The peptide Leu-Asp-Asp-Ser-Lys-Arg-Val-Ala-Lys-Arg-Lys-Leu-Ile-Glu, which corresponds to sequence 124 to 137 of c-erb-A protein, was synthesized and tested as substrate for protein kinase C (PKC). Although a typical recognition sequence for PKC, consisting of a cluster of basic residues, is found on the C-terminus side of serine, its phosphorylation was totally prevented by the presence of the two acidic residues on the amino-terminus side. Three analogs in which aspartyl residues were successively replaced with alanine were studied and the influence of the acidic side chain in modulating phosphorylation by PKC was thus possible to determine. The results show that the presence of a single aspartyl residue located in positions i-1 or i-2 with respect to the phosphorylable residue can almost totally abolish the positive effect of a highly favorable cluster of basic residues. These observations highlight the role of negative substrate specificity determinants in settling the protein substrate profile of protein kinase C.     

Wortmannin抑制PI3-K途径对K562及NB4细胞增殖的影响

目的 :为探讨Wortmannin抑制磷酰肌醇 - 3激酶 (PI- 3K)途径对K5 62 ,NB4细胞增殖的影响 ,探寻慢性髓细胞性白血病 (CML)的治疗新途径 .方法 :用磷酰肌醇 - 3激酶 (PI - 3K)特异抑制剂Wort mannin抑制PI - 3K活性 ,观察慢性髓细胞性白血病细胞系K5 62细胞和急性早幼粒细胞性白血病细胞系NB4细胞在 2 4,48,72h增殖能力的变化 .t检验统计分析 .结果 :K5 62和NB4细胞在 2 4,48,72h的增殖抑制率分别为 3 4 67% ,5 7 46% ,65 85 %和 2 6 2 9% ,5 5 1% ,2 10 % .集落形成实验以GM -CSF为主要生长刺激物的培养体系在 3 7℃ ,5 %CO2 孵箱培养 14d后细胞系的集落数和集落形成率分别为K5 62 :80 75±10 2 4和 16 15 % ,K5 62 +WT :3 8 0 0± 12 75和 7 60 % ,NB4:2 9 5 0± 5 97和 5 90 % ,NB4+WT :3 0 5 0± 5 74和 6 10 % .集落形成抑制率为 :5 2 94%和 3 3 9% .结论 :Wortmannin可显著抑制K5 62细胞的增殖和集落形成 ,而对NB4细胞无明显影响 (P均 <0 0 5 ) .Wortmannin可以通过抑制PI - 3K通路抑制K5 62细胞的增殖 ,而对NB4细胞增殖无明显影响     

Histamine differentially interacts with tumor necrosis factor-α and thrombin in endothelial tissue factor induction: the role of c-Jun NH2-terminal kinase

BACKGROUND: Histamine plays an important role in vascular disease. Tissue factor (TF) expression is induced in vascular inflammation and acute coronary syndromes. OBJECTIVES: This study examined the effect of histamine on tumor necrosis factor-alpha- (TNF-alpha-) vs. thrombin-induced endothelial TF expression. METHODS AND RESULTS: Histamine (10(-8)-10(-5) mol L-1), TNF-alpha (5 ng mL-1), and thrombin (1 U mL-1) induced TF expression in human endothelial cells. Although TF expression by TNF-alpha and thrombin was identical, histamine augmented TNF-alpha-induced expression 7.0-fold, but thrombin-induced expression only 2.6-fold. Similar responses occurred with TF activity. The H1-receptor antagonist mepyramine abrogated these effects. Differential augmentation by histamine was also observed at the mRNA level. Histamine-induced p38 activation preceded a weak second activation to both TNF-alpha and thrombin. Histamine-induced c-Jun NH2-terminal kinase (JNK) activation was followed by a strong second activation to TNF-alpha, and less to thrombin. Selective inhibition of this second JNK activation by SP600125 reduced TF induction to histamine plus TNF-alpha by 67%, but to histamine plus thrombin by only 32%. Histamine augmented TNF-alpha- and thrombin-induced vascular cell adhesion molecule 1 (VCAM-1) expression to a similar extent. Consistent with this observation, VCAM-1 induction to TNF-alpha and thrombin was mediated by p38, but not by JNK. CONCLUSIONS: Histamine differentially augments TNF-alpha- vs. thrombin-induced TF expression and activity, which is mediated by the H1-receptor, occurs at the mRNA level, and is related to differential JNK activation.     

靶向性蛋白激酶B1和环氧合酶-2 shRNA腺病毒载体的构建和在人胃癌细胞的表达

Objective To construct a short hairpin RNA (shRNA) adenovirus vector targeting protein kinase BI (PKB1/Akt1) and cyclooxygenase-2 (COX-2) and observe their expression in human gastric carcinoma cell line SGC-7901. Methods Akt1 and COX-2 shRNA expression frames were sub-cloned to pGSadeno adenovirus vector by homologous recombination technology to construct pGSadeno-Aktl + COX-2 ( pGSadeno-A + C) vector. Furthermore after screening and amplification,recombinant ade-novirus vector was digested with Pacl and transfected into HEK293 cells. The replication adenovirus rAd5-A + C was packed and amplified in the HEK293 cells, and its titer was detected. After human SGC-7901 cells in vitro were transfected by rAd5-A + C,Akt1 and COX-2 mRNA and protein expression levels were detected by real-time PCR and Western blot respectively. Compared with rAdS-A + C,SGC-7901 and gen-eral rAd5-HK were selected as the negative controls. Results The recombinant adenovirus rAd5-A + C was constructed successfully and its titer reached 1.0 ×1010 pfu/ml. Aktl and COX-2 mRNA expression was downregulated significantly, and their ACt values ( 12.26±0.05 and 5.41±0.09 respectively ) were higher than rAd5-HK group (10.63±0.02 and 3.75 +0.08 respectively) and control group (10.57± 0.02 and 3.73±0.08 respectively) (P <0.01 ). There was no significant difference between rAd5-HK and control groups (P >0.05). Aktl and COX-2 protein expression was downregulated by 70.5% and 63.7% respectively ( P < 0.01 ) in rAd5-HK group as compared with control group ( P > 0.05 ). Conclu-sion The shRNA aclenovirus vector targeting Akt1 and COX-2 can specifically inhibit Akt1 and COX-2 expression,and this may be a new strategy in gastric carcinoma gene therapy targeting Akt1 and COX-2.     

卵巢癌中蛋白激酶C的表达及其临床意义

目的　探讨上皮性卵巢癌组织蛋白激酶C (proteinkinaseC ,PKC)的表达和化疗耐药的关系 ,以及与P -糖蛋白 (P -gp)的相关性。方法　用免疫组化S -P法检测 35例卵巢上皮性肿瘤组织、 2 0例卵巢良性肿瘤组织和 2 0例正常卵巢组织中PKC和P -gp的表达 ,并进行相关临床因素分析。结果　①PKC、P -gp在卵巢恶性肿瘤中的表达明显高于在良性及正常组织中的表达 ;并且PKC和P -gp的表达有相关性 (P <0 0 5 ) ;②卵巢癌PKC的表达与临床病理因素无直接关系 ;③恶性肿瘤中 ,初治和复发的PKC表达阳性率分别为 34 8%和 75 % ;④化疗对PKC表达阳性和阴性卵巢癌患者的有效率分别为 2 3 5 %、 6 6 7% (P <0 0 5 ) ;⑤PKC表达阴性患者的预后优于阳性者 (P =0 0 39)。结论　PKC表达与卵巢癌组织化疗耐药明显相关 ,可能在P -gp介导的卵巢癌多药耐药中起重要作用。     

大肠杆菌脂多糖对人红细胞蛋白激酶C活性的影响

正常成人红细胞与大肠杆菌脂多糖温育后,胞膜蛋白激酶C活性显著增加,脂多糖这种作用呈现剂量和时间依赖性。结果提示脂多糖能激活红细胞蛋白激酶C。     

Acute neurite retraction triggered by lysophosphatidic acid: timing of the inhibitory effects of genistein

Acute neurite retraction, elicited by diverse agents in several neuronal cell types, has been reported to be inhibited by genistein, a kinase antagonist that is relatively (though not absolutely) selective for tyrosine kinases. It was hypothesized that genistein acts upon ssome final common pathway that integrates multiple extrinsic and intrinsic signals to regulate whether neurites will execute a retraction response (J. Neurochem., 61 (1993) 340–343). To define this pathway in more detail, a quantitative study of NG108-15 cell rapid-onset neurites was carried out as they retract in response to lysophosphatidic acid (LPA, 10 μM). Following the application of LPA, most neurites exhibited early morphologic changes between 0.5 and 1.5 min, followed by progressive shortening and eventual retraction, with 50% of neurites completely retracted by 5 min and 80% gone by 10 min. Genistein did not inhibit the formation of subcortical F-actin, nor its functional competence in several assays. Genistein protected neurites when added at any time prior to the onset of the earliest morphologic changes, but failed to block progression when added to neurites that were already undergoing retraction. These findings imply that the final common pathway (i.e. the critical target(s) for genistein) must be activated late, after the increase in F-actin levels has peaked and just before retraction is initiated.     

雌激素对内膜癌细胞中FAK基因转录的影响

目的定量观察雌激素刺激后内膜癌细胞的焦点粘连激酶（Focal—adhesion kinase，FAK）转录水平。方法不同浓度的17β-雌二醇体外刺激雌激素敏感的内膜癌细胞株RL95—2。加用三苯氧胺或ICI 182，780雌激素拮抗剂的细胞及未加雌激素的细胞设为阴性对照。经不同作用时间后，采用实时RT—PCR方法测定处理后的细胞内FAK的mRNA水平。结果在给予不同浓度的雌激素共培养1d或5d后，细胞的FAK基因的转录水平对比阴性对照细胞无明显改变。结论雌激素对内膜癌细胞的FAK转录可能无显著影响。FAK基因在内膜癌组织中的过度表达的机理需要进一步深入研究。