HIV-1 gp120 induces the activation of both c-fos and c-jun immediate-early genes in HEL megakaryocytic cells

We have previously demonstrated that the addition in culture of recombinant HIV-1 IIIB envelope gp120 affects the survival/growth of pluripotent haemopoietic progenitors, and, in particular, of those committed towards the megakaryocytic lineage. To characterize some of the molecular mechanisms involved in this phenomenon, we investigated the expression of members of the activating protein-1 (AP-1) complex in the HEL megakaryoblastic cell line. Following the treatment of HEL cells with recombinant IIIB envelope gp120, we noticed: (i) increased levels of endogenous c-fos and c-jun mRNA and proteins, (ii) activation of both c-fos and c-jun promoters, and (iii) a very rapid stimulation of a MAPK/ERK pathway.     

Follicle-stimulating hormone increases c-fos mRNA levels in rat granulosa cells via a protein kinase C-dependent mechanism

Recent evidence has been presented that follicle-stimulating hormone (FSH) stimulates the induction of granulosa cell c-fos protooncogene mRNA in vivo (Pennybacker and Herman (1989) J. Cell Biol. 109, 151A; Delidow et al. (1990) Endocrinology 126, 2302–2306), yet the mechanisms by which FSH induces c-fos mRNA expression have not been delineated. To elucidate the mechanisms of FSH-dependent c-fos mRNA expression, we measured the time and dose dependence of c-fos mRNA levels using Northern blot analysis in intact ovaries and cultured granulosa cells in response to FSH. In intact ovaries, FSH-induced c-fos mRNA expression was time dependent with maximal expression at 90 min post FSH injection, while in cultures of granulosa cells obtained from estrogen-primed immature female rats, c-fos mRNA levels were highest after 30 min exposure to FSH and at a concentration of 100 ng/ml. Neither 8-bromo adenosine 3′,5′-cyclic monophosphate (8-br-cAMP), at doses ranging from 0.1 to 10 mM, nor 100 μM forskolin (in the presence or absence of 200 μM isobutyl-methylxanthine) or luteinizing hormone (LH, 100 ng/ml) were able to mimic FSH-induced c-fos mRNA expression in granulosa cell cultures. However, tetradecanoyl-13-phorbol acetate (TPA, 200 nM) was able to induce c-fos mRNA expression. The protein kinase C (PKC) inhibitors H-7 (0.3–30 μM) and staurosporine (0.75 μg/ml) blocked FSH-induced c-fos mRNA expression in cultured granulosa cells while HA 1004, an inhibitor of cGMP- and cAMP-dependent protein kinases at 30 μM had no effect on TPA-induced c-fos expression, and only minimally inhibited FSH-induced c-fos expression. Both FSH (100 ng/ml) and forskolin (3 μM) increased progesterone production in cultured granulosa cells. These data support the hypothesis that FSH specifically induces c-fos mRNA expression by a PKC-dependent mechanism and that the cAMP arm of the FSH response pathway is operant in these cells.     

人肝脏星形细胞培养激活及其c-fos,c-jun的表达

目的观察体外培养过程中人肝脏星形细胞(HSCs)表型及其c-fos和c-jun表达的改变.方法将分离的正常人HSCs进行原代及传代培养,倒置显微镜下动态观察培养细胞形态改变,对原代及传代培养细胞铺展片进行PCNA、Ⅰ型前胶原、α-SMA,c-fos及c-jun免疫细胞化学染色.结果正常人HSCs在含100 mL/L小牛血清中培养时,其表型由原代培养初期的静息型转变为原代培养后期及传代后的激活型.激活的人HSCs呈现典型的成纤维细胞形态特征,其表达PCNA、Ⅰ型前胶原及α-SMA明显阳性.刚分离的正常人HSCs在不含血清的培养液中培养24 h后,其c-fos及c-jun表达均为阴性,而在含100 mL/L小牛血清的培养液中继续培养24 h后,c-fos及c-jun表达为阳性.原代培养d10及传代培养d 3的HSCs其c-fos及c-jun表达持续阳性.结论在含小牛血清的DMEM培养液中培养时,人HSCs自发地激活,这种激活可能与c-fos及c-jun表达增加有关.     

蛋白激酶C及转化生长因子β1信号通路对肝星状细胞激活的影响

目的探讨蛋白激酶C（PKC）活性改变对HSC表达TGF β1的影响及在HSC激活中的作用。方法将肝星状细胞系rHSC-99分为3组：对照组（A组），PKC激动剂佛波酯0．5μmol／L组（B组），PKC抑制剂Calphostin C 100nmol／L组（C组）。加药后0、3、6、12h和24h分别检测各组细胞PKC活性的变化；作用24h后，采用Western blot和RT—PCR方法检测各组细胞TGF β1，Smad 4，Ⅰ、Ⅲ型胶原和α-平滑肌肌动蛋白的表达；采用MTT法检测细胞的增殖情况。结果 佛波酯作用后PKC的活性显著增强，而Calphostin C则抑制PKC的活性。PKC活性增强后，与对照组相比TGF β1及其下游信号分子Smad 4的表达分别升高了4．8倍和13．1倍（P〈0．01）；HSC的Ⅰ、Ⅲ型胶原和α-平滑肌肌动蛋白的表达分别升高了2．4倍、1．8倍和1．3倍（P〈0．01），并促进HSC的增殖；PKC活性被抑制后则能抑制以上作用。结论PKC活性的改变能调控HSC中TGF β1的表达，在HSC的激活中发挥调节作用。     

表皮生长因子介导的核转录因子-κB活化促进胰腺癌细胞尿激酶型纤溶酶原激活物表达及侵袭和转移

目的:观察表皮生长因子(EGF)对胰腺癌细胞KP4增殖、黏附及侵袭力和核转录因子(NF-κB)、尿激酶型纤溶酶原激活物(uPA)表达的影响.方法:通过细胞侵袭、增殖及黏附实验观察在EGF影响下肿瘤细胞侵袭、增殖及黏附能力变化.Western blot,RT-PCR及EMSA实验检测胰腺癌细胞的NF-κB活性和uPA表达并观察在NF-κB抑制物PDTC抑制下EGF诱导的NF-κB活性和uPA表达及肿瘤细胞侵袭力变化.结果:EGF能够明显促进胰腺癌细胞的侵袭能力,具有明显的剂量依赖性(50,25,5μg/L vs 0 μg/L:116±13,97±10,83±7 vs 72±5;t=3.552,3.018,2.373;P=0.006,0.015,0.042),然而对增殖及黏附力无明显影响.随着EGF浓度的增加,NF-κB活性明显增强.EGF上调uPA蛋白及mRNA表达,具有浓度依赖性.PDTC显著抑制EGF诱导的NF-κB活性、uPA表达及胰腺癌细胞的侵袭力.结论:EGF通过激活NF-κB而诱导uPA表达,促进胰腺癌细胞的侵袭和转移.     

Prostaglandin F2alpha-activated protein kinase Calpha phosphorylates myristoylated alanine-rich C kinase substrate protein in bovine luteal cells

Prostaglandin F_2α (PGF_2α)-induced secretion of oxytocin by the bovine corpus luteum involves the phosphorylation of a unique protein kinase C (PKC) substrate, myristoylated alanine-rich C kinase substrate (MARCKS) protein. This study was conducted to determine the specific PKC isoform engaged in phosphorylation of MARCKS protein in bovine luteal cells. In experiment 1, dispersed luteal cells recovered from the corpus luteum on d 8 of the estrous cycle were preincubated with [³²P] orthophosphate and then exposed to PGF_2α alone or in combination with PKC inhibitors. Autoradiography and densitometry of Western blots revealed that MARCKS protein was phosphorylated by a conventional PKC (cPKC) isoform. Experiment 2 was conducted to identify the specific cPKC isoform that phosphorylates MARCKS protein in luteal cells. Corpora lutea were removed from control and PGF_2α-treated heifers on d 8 of the cycle, and PKC isoforms associated with membrane and cytosolic fractions were determined. Treatment with PGF_2α increased membrane concentrations of PKCα within 5 min after treatment (p<0.005). Collectively, these data suggest that phosphorylation of MARCKS protein coinciding with oxytocin secretion is mediated by PKCα.     

Phosphatidylethanol in high density lipoproteins increases the vascular endothelial growth factor in smooth muscle cells

To study whether qualitative changes in high density lipoprotein (HDL) phospholipids mediate part of the advantageous effects of ethanol on atherosclerosis, we investigated whether HDL associated phosphatidylethanol (PEth) affects the secretion of vascular endothelial growth factor (VEGF) from cultured human smooth muscle cells. Serum-starved human umbilical vein HUVS-112D smooth muscle cells were incubated in the presence of PEth–HDL, HDL, or buffer. The phosphorylation of protein kinase C (PKC) and mitogen activated protein kinase (p44/42 MAPK) was determined by specific antibodies against phosphorylated and total proteins. VEGF concentrations were measured from cell culture medium of the cells. PEth increased the secretion of VEGF into the culture medium of HUVS cells. PEth–HDL increased the PKC phosphorylation by 2.1-fold and p44/42 MAPK phosphorylation by 3.3-fold compared with HDL, indicating that PEth-containing HDL particles influence vascular smooth muscle cells by PKC and p44/42 MAPK signalling. This may mediate the effects of ethanol on vascular wall by increasing the VEGF secretion from smooth muscle cells. The secreted VEGF may inhibit the formation of neointima and in doing so helps prevent atherosclerosis.     

Epidermal growth factor receptor-targeted therapy potentiates lovastatin-induced apoptosis in head and neck squamous cell carcinoma cells

Purpose Mevalonate metabolites are vital for a variety of key cellular functions with the biosynthetic products including cholesterol and farnesyl and geranylgeranyl isoprenoids. Inhibition of this pathway using lovastatin induces a potent apoptotic response in a specific subset of human tumor-derived cell lines, including head and neck squamous cell carcinomas (HNSCC). In this study, we evaluated the potential of a number of chemotherapeutics that demonstrate activity in HNSCC, including an inhibitor of epidermal growth factor receptor (EGFR) to potentiate the cytotoxic effects of lovastatin.Methods We evaluated the cytotoxic effects of combining a variety of chemotherapeutics with lovastatin using the MTT assay and flow cytometry. The MCF-7 lovastatin-resistant breast adenocarcinoma cell line and the lovastatin-sensitive HNSCC cell lines SCC9 and SCC25 were tested. Expression levels of EGFR and ligand activated EGFR following lovastatin treatment were analyzed by Western blotting.Results Pretreatment or concomitant treatment of 10 M lovastatin did not significantly augment the effects of a variety of chemotherapeutic agents tested in these cell lines. Co-administration with actinomycin D or cycloheximide, drugs that inhibit RNA and protein synthesis, respectively, inhibited lovastatin-induced apoptosis in these cell lines. This suggests a requirement for the cellular functions disrupted by these chemotherapeutic agents in lovastatin-induced apoptosis of HNSCC cells. In contrast to the chemotherapeutics analyzed, the AG1478 tyrosine kinase inhibitor of the EGFR demonstrated additive cytotoxic effects in combination with lovastatin in HNSCC cells. Mevalonate metabolites may regulate EGFR function, suggesting that lovastatin may inhibit the activity of this receptor. Indeed, lovastatin treatment inhibited EGF-induced autophosphorylation of the EGFR in the SCC9 and SCC25 cell lines. Pretreatment of SCC9 and SCC25 cell lines for 24 h with 10 M lovastatin, conditions that demonstrated significant inhibition of EGF-induced EGFR autophosphorylation, induced significant additive effects in combination with AG1478.Conclusion These results demonstrated the ability of EGFR pathway inhibitors to potentiate lovastatin-induced apoptosis and suggested that lovastatin may target the EGFR pathway in HNSCC cells.Abbreviations HNSCC head and neck squamous cell carcinoma - EGFR epidermal growth factor receptor - 5-FU 5-fluorouracil - HMG-CoA 3-hydroxy-3-methylglutaryl coenzyme A - ActD actinomycin D - CHX cycloheximide     

HB-EGF enhances restitution after intestinal ischemia/reperfusion via PI3K/Akt and MEK/ERK1/2 activation

BACKGROUND & AIMS: Early recovery of intestinal function after injury occurs by restitution, a complex process with a poorly understood molecular basis. Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is a potent chemotactic factor that is induced during ischemia/reperfusion in vivo and intestinal wounding in vitro. The role of HB-EGF in intestinal restitution and the underlying intracellular signaling pathways involved were investigated. METHODS: Adult rats were subjected to intestinal ischemia, with histologic and biochemical damage assessed during the first 3 hours of reperfusion. The effect of recombinant HB-EGF (rHB-EGF) on structural and functional recovery of the intestine by restitution was evaluated in vivo. Scrape wounding of intestinal epithelial cell monolayers was used to elucidate the mechanisms of intrinsic and rHB-EGF-induced restitution. RESULTS: Early structural recovery occurred within 3 hours of reperfusion and was attributed to restitution rather than proliferation. HB-EGF treatment significantly improved structural recovery and accelerated functional recovery of the gut barrier. In vivo restitution was preceded by activation of Akt and extracellular signal-regulated kinase (ERK) 1/2, which were accelerated and enhanced by HB-EGF treatment. Blocking of ErbB-1, phosphatidylinositol 3-kinase (PI3K)/Akt, or mitogen-activated protein kinase/ERK kinase (MEK)/ERK activity resulted in significant reduction in intrinsic and HB-EGF-induced restitution in vitro. Endogenous HB-EGF was shown to play an essential role in wound-induced ErbB-1 and ERK1/2 activation and in intrinsic restitution. CONCLUSIONS: Endogenous HB-EGF, ErbB-1, PI3K/Akt, and MEK/ERK are involved in intrinsic restitution. rHB-EGF enhances restitution in vivo and in vitro in a PI3K/Akt- and MEK/ERK1/2-dependent fashion.     

神经生长因子通过c-fos促进支气管上皮细胞NK-1R表达

目的探讨神经生长因子(NGF)通过c-fos影响支气管上皮细胞NK-1R的表达。方法以人支气管上皮细胞(NHBEC)为研究对象,通过阳离子脂质体将c-fos siRNA转染至细胞内,然后用NGF干预。实验设五组:对照组、NGF干预组、NGF+c-fos siRNA组、NGF+空白脂质体组、NGF+非特异性dsRNA组。转染12 h后,用NGF干预60 min,采用Western blot法测定c-fos蛋白表达,采用免疫细胞化学法和RT-PCR从蛋白和mRNA水平观察细胞中NK-1R的表达。结果与对照组比,NGF组c-fos蛋白、NK-1R蛋白和NK-1RmRNA表达均明显增加(P0.01);与NGF组比,NGF+c-fos siRNA组中c-fos蛋白、NK-1R蛋白和NK-1RmRNA表达均明显减少(P0.01),而NGF组、NGF+空白脂质体组、NGF+非特异性dsRNA组之间的c-fos蛋白、NK-1R蛋白和NK-1RmRNA表达无显著差异。结论 NGF可通过c-fos促进支气管上皮细胞中NK-1R的表达,介导哮喘神经源性炎症,RNAi技术可以减少NGF诱导的人支气管上皮细胞c-fos蛋白及NK-1R的表达。     

机械应力对MG63成骨样细胞结缔组织生长因子表达的影响

目的 观察力学刺激对MG63成骨样细胞的结缔组织生长因子(CTGF)表达的影响以及丝裂原活化蛋白激酶(MAPK)信号途径在这一过程中的作用.方法 应用Western印迹法检测MG63细胞CTGF蛋白表达及细胞外信号调节激酶(ERK)、c-Jun氨基末端激酶(JNK)、p38磷酸化水平,应用RT-PCR检测CTGF mRNA表达.结果 环状应力刺激可显著上调CFGF蛋白及mRNA表达,3～6 h达高峰,升高2～3倍;并且激活ERK及JNK信号途径,刺激10 min开始活化,ERK在60 min达高峰,而JNK在15～30min达高峰,对p38信号途径没有明显活化作用.JNK信号通路阻断剂SP600125能够阻断应力刺激对CTGF的上调作用,而ERK信号阻断剂PD98059及p38信号阻断剂SB203580却无此作用.结论 环状机械应力通过JNK依赖的途径上调了MG63细胞的CTGF表达.     

Epidermal growth factor receptor mutations and susceptibility to targeted therapy in lung cancer

According to 2002 estimates, 1.35 million people were diagnosed with and 1.18 million died of lung cancer worldwide. Recently, a new class of medications targeting signal transduction pathways has come into focus in the treatment of various malignancies. In lung cancer, the molecules gefitinib and erlotinib which target the intracellular kinase domain of the epidermal growth factor receptor (EGFR), cause significant tumour responses and, in the case of erlotinib, a survival benefit in patients with previously treated cancers. Responses were most pronounced in female non-smokers with adenocarcinoma histology. These patients were found more likely to harbour mutations of the receptor kinase domain, including in-frame deletions in exon 19 (such as deletions of codons 746-750) and point deletions in exon 21 (such as L858R). Other EGFR kinase domain mutations have been found to confer resistance (T790M) or differential susceptibility to erlotinib and gefitinib (E884K). Gene amplification of EGFR also may predict sensitivity, although the mechanism by which this occurs is unclear, because level of expression detected by immunohistochemistry has not been correlated with increased sensitivity. Phenotypic and genotypic epithelial to mesenchymal transition may be an indicator of resistance to EGFR kinase inhibitors. In this article, we review efforts that have been undertaken to identify genomic determinants of drug susceptibility to EGFR tyrosine kinase inhibitors, with particular focus on the role of gene mutations.     

Epidermal growth factor receptor and cyclin D1 are independently amplified and overexpressed in esophageal squamous cell carcinoma

Purpose To assess the status of EGFR, HER-2, and CCND1 at the gene and protein levels in esophageal squamous cell carcinoma.Methods Dual-color FISH assays were performed using DNA probes for EGFR/CEP 7, HER-2/CEP 17, and CCND1/CEP 11. The respective proteins, furthermore, was assessed in IHC assays and correlated with patient and tumor characteristics.Results From 55 ESCCs, 8 (15%) tumors showed gene amplification and 20 (36%) had gene overrepresentation (balanced gene and chromosome 7 polysomy) for EGFR. High-level protein expression was frequent (49%), positively correlated with gene copy numbers (kappa=0.4), and associated with well-differentiated histology (p=0.02). For HER-2, gene amplification was detected in a single tumor (2%) and protein overexpression was rare (9%). CCND1 gene was amplified in 23 (42%) tumors; likewise, CCND1 protein overexpression was common (58%) and prevailed in gene overrepresentation or amplification. Only 1 patient showed gene amplification for both EGFR and CCND1. Survival was not associated with EGFR or CCND1 gene/protein status, whereas negative patients for HER-2 protein had a better survival than positive patients (p=0.04).Conclusions Frequent overexpression and gene amplification of EGFR and CCND1 make these molecules and their pathways potential therapeutic targets for ESCC. In addition, EGFR and CCND1 appeared to be independently altered suggesting alternative mechanisms for pathway activation. Therapeutic agents targeting these molecules are urged to be tested in clinical trials and comprehensive biological analyses should be included to properly interpret the outcome.     

Melatonin induces neuritogenesis at early stages in N1E-115 cells through actin rearrangements via activation of protein kinase C and Rho-associated kinase

Melatonin increases neurite formation in N1E-115 cells through microtubule enlargement elicited by calmodulin antagonism and vimentin intermediate filament reorganization caused by protein kinase C (PKC) activation. Microfilament rearrangement is also a necessary process in growth cone formation during neurite outgrowth. In this work, we studied the effect of melatonin on microfilament rearrangements present at early stages of neurite formation and the possible participation of PKC and the Rho-associated kinase (ROCK), which is a downstream kinase in the PKC signaling pathway. The results showed that 1 nm melatonin increased both the number of cells with filopodia and with long neurites. Similar results were obtained with the PKC activator phorbol 12-myristate 13-acetate (PMA). Both melatonin and PMA increased the quantity of filamentous actin. In contrast, the PKC inhibitor bisindolylmaleimide abolished microfilament organization elicited by either melatonin or PMA, while the Rho inhibitor C3, or the ROCK inhibitor Y27632, abolished the bipolar neurite morphology of N1E-115 cells. Instead, these inhibitors prompted neurite ramification. ROCK activity measured in whole cell extracts and in N1E-115 cells was increased in the presence of melatonin and PMA. The results indicate that melatonin increases the number of cells with immature neurites and suggest that these neurites can be susceptible to differentiation by incoming extracellular signals. Data also indicate that PKC and ROCK are involved at initial stages of neurite formation in the mechanism by which melatonin recruits cells for later differentiation.     

C-peptide stimulates ERK1/2 and JNK MAP kinases via activation of protein kinase C in human renal tubular cells

Aims/hypothesis Accumulating evidence indicates that replacement of C-peptide in type 1 diabetes ameliorates nerve and kidney dysfunction, but the molecular mechanisms involved are incompletely understood. C-peptide shows specific binding to a G-protein-coupled membrane binding site, resulting in Ca²⁺ influx, activation of mitogen-activated protein kinase signalling pathways, and stimulation of Na⁺, K⁺-ATPase and endothelial nitric oxide synthase. This study examines the intracellular signalling pathways activated by C-peptide in human renal tubular cells.Methods Human renal tubular cells were cultured from the outer cortex of renal tissue obtained from patients undergoing elective nephrectomy. Extracellular-signal-regulated kinase 1/2 (ERK1/2), c-Jun N-terminal kinase (JNK) and Akt/protein kinase B (PKB) activation was determined using phospho-specific antibodies. Protein kinase C (PKC) and RhoA activation was determined by measuring their translocation to the cell membrane fraction using isoform-specific antibodies.Results Human C-peptide increases phosphorylation of ERK1/2 and Akt/PKB in a concentration- and time-dependent manner in renal tubular cells. The C-terminal pentapeptide of C-peptide is equipotent with the full-length C-peptide, whereas scrambled C-peptide has no effect. C-peptide stimulation also results in phosphorylation of JNK, but not of p38 mitogen-activated protein kinase. MEK1/2 inhibitor PD98059 blocks the C-peptide effect on ERK1/2 phosphorylation. C-peptide causes specific translocation of PKC isoforms and to the membrane fraction in tubular cells. All stimulatory effects of C-peptide were abolished by pertussis toxin. The isoform-specific PKC- inhibitor rottlerin and the broad-spectrum PKC inhibitor GF109203X both abolish the C-peptide effect on ERK1/2 phosphorylation. C-peptide stimulation also causes translocation of the small GTPase RhoA from the cytosol to the cell membrane. Inhibition of phospholipase C abolished the stimulatory effect of C-peptide on phosphorylation of ERK1/2, JNK and PKC-.Conclusions/interpretation C-peptide signal transduction in human renal tubular cells involves the activation of phospholipase C and PKC- and PKC-, as well as RhoA, followed by phosphorylation of ERK1/2 and JNK, and a parallel activation of Akt.     

Raf-1 kinase,epidermal growth factor receptors,and mutant ras proteins in colonic carcinomas

Epidermal growth factor receptors (EGFR) andras mutations are known to play a significant role in controlling cell growth and tumor promotion. Both of them transmit mitogenic signals to the nucleus by activation of Raf-1 kinase. In this study, the expression of EGFR and mutant Ras proteins, and, for the first time, the expression, phosphorylation and kinase activity of Raf-1 kinase have been determined in paired samples of colorectal cancer and mucosa. The tumor and mucosa samples did not differ significantly with regard to Raf-1 kinase content and activity. A major difference between tumors and mucosa was found, however, in the phosphorylation of Raf-1. Most of the mucosa samples (13/20), but only 1/20 of the cancer samples, contained hyperphosphorylated Raf-1. EGFR were significantly (p=0.0025) decreased in the tumors. The decreased phosphorylation of Raf-1 in colonic carcinomas could be the result of activation of Raf-1 phosphatases or inactivation of kinases phosphorylating Raf-1. New forms of treatment based on EGFR overexpression do not seem to be suitable for the majority of colonic cancers.This work was supported by the state of Baden-Württemberg (Verbundforschungsprojekt: Aufklärung von Mechanismen der Tumorentstehung und Tumorabwehr).