从天然产物中寻找蛋白激酶C抑制剂的研究进展

蛋白激酶C(PKC)抑制剂对抗肿瘤、抗病毒、治疗心血管疾病等多种药物的合理设计有着非常重要的意义。该文对文献报道的天然产物中的PKC抑制剂依据化学结构进行分类,并对其生物来源、生物活性和作用位点进行综述。     

蛋白激酶C在肿瘤中的作用及其抑制剂研究进展

蛋白激酶C(protein kinase C,PKC)在肿瘤的发生、发展和转移中均发挥着重要作用,因此,PKC是开发治疗肿瘤疾病药物的潜在分子靶点。目前,几种PKC抑制剂已经进入临床研究阶段,但是同时也为靶向PKC抗肿瘤药物的研究开发带来了新的挑战。该文拟对近年来蛋白激酶C在肿瘤中的作用及其抑制剂研究进展作一综述。     

Screening methods for AMP-activated protein kinase modulators: a patent review

Introduction: AMP-activated protein kinase (AMPK) functions as a cellular energy gauge that maintains cellular homeostasis and has been suggested to play important roles in tumorigenesis, lifespan and autophagy. Accordingly, AMPK is a potential target of drugs for controlling a growing number of human diseases ranging from metabolic disorders to cancer, highlighting the need for rational and robust screening systems for identifying compounds that modulate AMPK.

Areas covered: The relevant screening methods in the patent and scientific literature were analyzed, and key features of direct AMPK modulators are discussed in the context of their physiological relevance and the three-dimensional structure of the AMPK complex.

Expert opinion: The mechanism of action of modulators is important in designing drugs with enhanced efficacy, specificity and stability. Most patented assay formats for identifying AMPK modulators are based on classical enzyme assays that monitor AMPK activity or changes in AMPK-dependent cellular physiology. However, these systems do not provide information about underlying mechanisms. Two patented assay systems use a specific domain or the three-dimensional structure of AMPK to identify AMPK modulators. The recent identification of two AMPK modulators, A-769662 and C-2 (or its prodrug, C-13), suggests the promise of structure-based assays in discovering more potent and specific modulators of AMPK.     

蛋白激酶C 抑制剂的研究新进展

摘要： 蛋白激酶 C （PKC） 是一组磷脂依赖性的丝氨酸/苏氨酸蛋白激酶, 与蛋白激酶 A （PKA） 和蛋白激酶 G （PKG） 共同构成丝氨酸/苏氨酸蛋白激酶 AGC 超家族。PKC 包括传统型 PKC、 新型 PKC、 非典型 PKC 和与 PKC 相关的一些激酶 （PRK） 成员。PKC 广泛分布于哺乳动物的组织和细胞中, 对细胞的生长代谢、 增殖分化等起着重要的生物学作用。研究表明, 多种细胞的变异和疾病的发生发展都与 PKC 的异常表达有关。因此, 设计和寻找高效的 PKC 抑制剂对于多种有效药物的合成和临床上包括肿瘤、 心血管疾病、 高血压等多种疾病的治疗都具有非常重要的意义。近年来, 关于 PKC 抑制剂的研究已经成为国内外研究的焦点。大量文献报道了多种有效的 PKC 抑制剂, 并对其作用位点、 作用机制以及临床试验数据等进行了分析。这些 PKC 抑制剂的发现对于 PKC 的结构分析和疾病的治疗具有重要的意义。因此, 本文对这些高效的PKC 抑制剂进行综述。     

糖尿病合并症与蛋白激酶C

糖尿病 (DM )可引起体内各系统的合并症。实验研究表明 ,二酰基甘油 (DAG) 蛋白激酶C(PKC)通路的活动增加与DM合并症的产生密切相关 ,可能是DM时多种生化指标引起合并症产生的最后的细胞内共同通路。在已知的 11中PKC亚型中 ,PKC β和 ε与DM合并症的产生最为密切     

蛋白激酶C激活剂和抑制剂对肿瘤坏死因子杀瘤活性的影响

以小鼠成纤维细胞瘤L929细胞为靶细胞,研究蛋白激酶C(PKC)的激活剂和抑制剂对人重组肿瘤坏死因子(rHuTNF)杀瘤活性的影响.各种药物与rHuTNF 10 ng·ml~(-1)和放线菌素D 1 μg·ml~(-1)温育18 h,结果表明PKC的激活剂佛波醇-12-肉豆蔻酸盐-13-乙酸盐(PMA)2.5～160ng·ml~(-1)可浓度依赖性地抑制rHuTNF的杀瘤活性.Sc-10(1～16μg·ml~(-1))单独作用很弱,但可浓度依赖地增强PMA 10 ng·ml~(-1)或A23187 0.5μg·ml~(-1)的抑制作用,PKC抑制剂1-(5-异喹啉磺酰基)-2-甲基哌嗪(H-7)单独作用对rHuTNF杀瘤活性无影响,但可减弱PMA 50ng·ml~(-1)的抑制作用.槲皮囊2～16μg·ml~(-1)则可直接抑制rHuTNF的杀瘤活性,钙调蛋白抑制剂N-(6-氨己基)-5-氯-1-萘磺酰胺(W-7)及其同系物也有微弱的抑制作用.结果提示PKC在rHuTNF杀瘤作用中起着重要作用.     

溶血性磷脂酰胆碱诱导血小板活化及蛋白质酪氨酸激酶和蛋白激酶C的作用

应用双道血小板聚集仪和荧光分光光度计分别测定溶血性磷脂酰胆碱(LysoPC)诱导的兔洗涤血小板聚集,细胞内钙离子浓度(［Ca²⁺］_i),细胞内pH值(pH_i)的变化及5-羟色胺(5-HT)的释放,并观察蛋白质酪氨酸激酶(PTK)抑制剂金雀异黄素(Gen)和蛋白激酶C(PKC)抑制剂星形孢菌素(Sta)对其作用的影响. 结果表明：LysoPC(30-300 μmol·L^-1)诱导血小板聚集,5- HT释放和［Ca²⁺］_i 升高,均呈现良好的浓度依赖性,100 μmol·L^-1以上时伴有pH_i的增加;Gen使LysoPC 诱导的聚集浓度效应曲线右移,半效聚集浓度值从(100±23) μmol·L^-1增加到(200±42) μmol·L^-1,明显抑制 ［Ca²⁺］_i 升高和胞浆碱化,对5-HT释放无明显影响;Sta对较低浓度LysoPC 诱导的血小板聚集,5-HT释放, ［Ca²⁺］_i 和pH_i的增加均有明显抑制作用,但对高浓度LysoPC 诱导的血小板活化无明显影响. 提示：LysoPC通过内Ca²⁺调节和Na^＋/H^＋交换介导血小板聚集和致密颗粒释放;PTK的激活参与了LysoPC诱导的血小板聚集,内Ca²⁺调节和Na^＋/H^＋交换,而在5-HT释放的机理中意义不大;PKC的激活在较低浓度LysoPC 诱导的血小板活化中起重要作用,高浓度LysoPC通过不依赖于PKC的途径激活血小板.     

蛋白激酶C在心肌预适应中的作用机制

心肌预适应后 ,内源性物质释放 ,分别作用于心肌中与G蛋白耦联的相应受体 ,蛋白激酶C激活并转位至细胞膜及细胞骨架 ,并可通过线粒体KATP通道、MAPK等通路引发心肌保护作用。在不同的动物中 ,分别发现不同的蛋白激酶C亚型激活转位。目前公认 :在参与心肌预适应过程的多种因素中 ,PKC起到了关键性作用 ,是多种因素作用的一条共同通路     

Effect of barbiturates on polyphosphoinositide biosynthesis and protein kinase C activity in synaptosomes

Previously, it has been found that phenobarbital inhibited protein kinase C (PKC) and the enzymes of the metabolism of polyphosphoinositide, especially phosphatidylinositol 4-phosphate (PIP) kinase (PIP-kinase). As a continuation of these studies, a number of barbiturates (barbituric acid, barbital, butabarbital, pentobarbital, amobarbital, phenobarbital, secobarbital and hexobarbital) were tested for inhibition of these enzymes and also of phosphatidylinositol (PI) kinase (PI-kinase), in a synaptosomal preparation at pH 7.8 from the brain of rat. All compounds, except barbituric acid (and Na-barbital for PI-kinase) inhibited the three kinases. However, PKC was approximately 3–5 fold more sensitive to inhibition by the drugs (measured by Ki values) than PIP-kinase, which was 2- to 4-fold more sensitive than PI-kinase. The inhibitory potency of the drugs increased with their lipophilicity, although to a lesser degree than expected from the differences in partition coefficients; the largest deviation from a positive correlation (i.e. hexobarbital) may be the result of the blockade of an imide (-NH) group at one position of the barbituric ring. Concentrations of drugs (after correction for the greater than normal ionization (pH 7.8) of the drugs in the assays) necessary for half-maximal inhibition were well within, or smaller than, those reported necessary for in vitro blocking of nerves. The possibility, therefore, exists that the physiological effects of the barbiturates are, in part, the result of an inhibition of protein kinase C and PIP-kinase.     

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.     

Stepwise high-throughput virtual screening of Rho kinase inhibitors from natural product library and potential therapeutics for pulmonary hypertension

Abstract

Context: Pulmonary hypertension (PH) is a devastating disease characterized by progressive elevation of pulmonary arterial pressure and vascular resistance due to pulmonary vasoconstriction and vessel remodeling. The activation of RhoA/Rho-kinase (ROCK) pathway plays a central role in the pathologic progression of PH and thus the Rho kinase, an essential effector of the ROCK pathway, is considered as a potential therapeutic target to attenuate PH.

Objective: In the current study, a synthetic pipeline is used to discover new potent Rho inhibitors from various natural products.

Materials and methods: In the pipeline, the stepwise high-throughput virtual screening, quantitative structure–activity relationship (QSAR)-based rescoring, and kinase assay were integrated. The screening was performed against a structurally diverse, drug-like natural product library, from which six identified compounds were tested to determine their inhibitory potencies agonist Rho by using a standard kinase assay protocol.

Results: With this scheme, we successfully identified two potent Rho inhibitors, namely phloretin and baicalein, with activity values of IC₅₀?=?0.22 and 0.95?μM, respectively.

Discussion and conclusion: Structural examination suggested that complicated networks of non-bonded interactions such as hydrogen bonding, hydrophobic forces, and van der Waals contacts across the complex interfaces of Rho kinase are formed with the screened compounds.     

Role of mitochondrial KATP channels and protein kinase C in ischaemic preconditioning

1. Activation of mitochondrial KATP (mitoKATP) channels and protein kinase C (PKC) has been implicated in cardioprotective mechanisms of ischaemic preconditioning (IPC). However, the exact role of these events in early IPC remains unclear. 2. Isolated and perfused rat hearts underwent IPC with three cycles of 5 min ischaemia and 5 min reperfusion. The heart was subjected to 30 min global ischaemia followed by 120 min reperfusion. Flavoprotein oxidation was monitored to assess mitoKATP channel activity. Cardioprotection was evaluated by recovery of isovolumic left ventricular (LV) function and infarct size. 3. Diazoxide (50 mgr;mol/L) increased flavoprotein oxidation and conferred cardioprotection in a manner sensitive to the selective mitoKATP channel blocker 5-hydroxydecanoate (5-HD; 0.5 mmol/L). 4. Pretreatment with 0.5 mmol/L 5-HD abrogated IPC-induced flavoprotein oxidation and cardioprotection, whereas late treatment with 5-HD after IPC required a higher dose (2 mmol/L) to abolish flavoprotein oxidation and cardioprotection afforded by IPC. 5. Pretreatment with the PKC inhibitors Ro318425 (1 micro mol/L) and chelerythrine (5 micro mol/L) abolished IPC-induced flavoprotein oxidation and cardioprotection, whereas late treatment with Ro318425 required a higher dose (4 micro mol/L) to abolish flavoprotein oxidation and cardioprotection. 6. In conclusion, these results suggest that activation of mitoKATP channels is the trigger and the mediator of IPC and that PKC plays a crucial role in both phases of mitoKATP channel activation, although mitoKATP channels and PKC may be more activated during the mediator phase.     

Protein kinase C isozymes as potential therapeutic targets in immune disorders

Background: Members of the protein kinase C (PKC) family are key signalling mediators in immune responses, and pharmacological inhibition of PKCs may be useful for treating immune-mediated diseases. Objective: To review and discuss the insights gained so far into various PKC isozymes and the therapeutic potential and challenges of developing PKC inhibitors for immune disorder therapy. Methods: A literature review of the role of PKCs in immune cell signalling and recent studies describing immune functions associated with PKC isozyme deficiency in relevant mouse disease models, followed by specific case studies of current and potential therapeutic strategies targeting PKCs. Results/conclusion: There is vast amount of data supporting PKC isozymes as attractive drug targets for certain immune disorders. Although the development of specific PKC isozyme inhibitors has been challenging, some progress has been made. It remains to be seen if broad-scale or isozyme-selective inhibition of PKC will have clinical efficacy.     

New small-molecule inhibitors of mitogen-activated protein kinase kinase

Background: Overexpression of the Ras/Raf/MEK/ERK (extracellular-signal-regulated kinase) pathway is associated with the formation, progression and survival of tumours and has also been implicated in a diverse range of therapeutic areas such as arthritis, organ transplant rejection, asthma and developmental disorders. One approach to down regulation of this pathway is through the inhibition of mitogen-activated protein kinase kinase 1/2 (MEK1/2). Objective: The importance of the mitogen-activated protein kinase (MAPK) pathway, MEK1/2 as a therapeutic target and early MEK1/2 inhibitors is discussed, followed by an overview of recent patent activity in the area. Methods: The patent literature was searched for inhibitors of MEK1/2 published within the last three years; these results are described. Other relevant publications that provide further insight into the discovery and development of these compounds are also discussed. Conclusion: The determination of a crystal structure with inhibitor bound has allowed the design of exquisitely selective and potent inhibitors of MEK1/2. Several allosteric inhibitors have advanced to clinical trial and shown some efficacy in cancer as single agents, but the future application of MEK1/2 inhibitors is likely to be either in combination with other therapies or in disorders which are genetically defined as being dependent on the MAPK pathway.     

Synthesis of a substrate of protein kinase C and its corresponding phosphopeptide

The syntheses of a protein kinase C (PKC) peptide substrate, H-Lys-Arg-Thr-Leu-Arg-OH, and a phosphopeptide analog of the synthetic substrate, H-Lys-Arg-Thr(P)-Leu-Arg-OH, are reported. PKC phosphorylates the peptide with an apparent K_M of 0.30 ± 0.04 mM and an apparent V_max equal to one-tenth that of histone III-S. The synthesis of the phosphopeptide features a recently developed convenient phosphorylation procedure for serine and threonine using N,N-diethylamino-dibenzylphosphoramidite. A complete characterization of the PKC substrate and its corresponding phosphopeptide by C-H COSY 2D n.m.r. is included.     

灯盏花素对慢性低氧大鼠PKC的影响

目的　探讨灯盏花素对慢性低氧大鼠PKC信号途径的影响。方法　将SD大鼠分为 :对照组 (A) ,低氧组 (B) ,低氧 +灯盏花素组 (C) ,低氧时间为 4wk。采用透射电镜、放射活性测定法、免疫组化等方法研究灯盏花素对慢性低氧大鼠肺动脉平均压 (mPAP)、左右心室重量比 (RV/LV +S)、肺细小动脉管壁面积 /管总面积 (WA/TA)、中膜平滑肌细胞核密度 (SMC)、肺细小动脉超微结构、肺组织PKC活性、肺细小动脉管壁PKC的影响。结果　 (1)B组mPAP、RV/LV +S明显高于A组 (P <0 0 1) ,C组mPAP、RV/LV +S明显低于B组 (P <0 0 1) ;(2 )光镜下B组WA/TA、SMC明显高于A组 (P <0 0 1) ,C组WA/TA、SMC明显低于B组 (P <0 0 1) ;电镜显示B组肺动脉中膜平滑肌细胞增生 ,胶原纤维丰富 ;C组肺动脉中膜平滑肌细胞、胶原纤维较B组明显减少 ;(3)B组肺组织PKC总活性 (PKCt)、胞膜PKC活性(PKCm)、胞质PKC活性 (PKCc)及胞膜PKC活性 (PKCm)占PKC总活性 (PKCt)的百分比明显高于A组 (P <0 0 1) ,C组PKCt、PKCm、PKCc及PKCm占PKCt的百分比明显低于B组 (P <0 0 1) ;(4 )免疫组化显示B组肺细小动脉 (直径约10 0～ 2 0 0 μm)PKC含量明显高于A组 (P <0 0 1) ,C组较B组明显为低 (P <0 0 1)。结论　灯盏花素抑制PKC信号途径可能是其抑制慢性低氧     

Therapeutic potential of natural compounds that regulate the activity of protein kinase C

Protein kinase C (PKC) is a family of serine/threonine kinases that regulates a variety of cell functions including proliferation, gene expression, cell cycle, differentiation, cytoskeletal organization, cell migration, and apoptosis. The PKC signal transduction cascade coordinates complex physiological events including normal tissue function and repair. Disruption of the cellular environment through genetic mutation, disease, injury, or exposure to pro-oxidants, alcohol, or other insults can induce pathological PKC activation. Aberrant PKC activation can lead to diseases of cellular dysregulation such as cancer and diabetes. Can aberrant activation of PKC be reversed? Even 25 years after the identification of PKC, therapeutic regulation of PKC activity remains an emerging field. Because the function of each isoform remains to be elucidated, isoform specific control of gene expression is a current challenge. Natural compounds are important regulators of PKC activity, with both preventive and therapeutic efficacy. Antioxidants including vitamin A (retinoids), vitamin C (ascorbic acid) and vitamin E (tocopherols) show promise for reversal of PKC activation. beta-carotene and retinoids function as anticarcinogenic agents and antagonize the biological effects of pro-oxidants on PKC. Vitamin E reverses the deleterious effects of hyperglycemia and diabetes by down-regulating PKC activity. Antioxidants in red wine provide cardioprotective effects. However, alcohol consumption also induces oxidative stress and disrupts PKC and retinoid function in the fetus and the adult. This review examines modulation of PKC activity by natural compounds and pharmacologic analogues which can be used effectively to prevent or treat common diseases associated with aberrant activation of PKC.     

蛋白酪氨酸激酶抑制剂的研究进展

目的综述蛋白酪氨酸激酶(protein tyrosine kinase,PTK)抑制剂类抗肿瘤药物的研究进展。方法根据已报道的PTK抑制剂的相关文献,将其分为国外已经上市、国外处于临床研究和我国自主研发的PTK抑制剂进行具体介绍。结果 PTK在细胞内的信号转导中起着重要的作用,与肿瘤细胞的生长、增殖、分化和凋亡密切相关,目前已经有多种结构的PTK抑制剂类抗肿瘤药物上市或进入临床研究。结论随着PTK的作用机制及构效关系研究的不断深入,该类药物终将成为治疗肿瘤的有效药物。