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。     

蛋白激酶C与免疫系统的关系及其抑制剂的研究进展

目的阐述蛋白激酶C(protein kinase C,PKC)与免疫系统的关系并综述近年来以PKC为靶点按不同结构修饰的免疫抑制剂研究。方法根据已报道的蛋白激酶C参与的免疫系统有关的细胞信号转导通路和PKC免疫抑制剂结构修饰的文献,对PKC与免疫系统的关系进行简单概述,并将具有免疫抑制活性的PKC抑制剂以结构分类综述。结果蛋白激酶C在免疫系统中发挥着重要作用,其与很多免疫疾病的发生密切相关。设计合成小分子化合物来抑制蛋白激酶C活性成为治疗自身免疫疾病及其他免疫性疾病的最佳策略。通过高通量筛选、结构修饰等方法已获得了大量以蛋白激酶C不同亚型尤其是PKCθ为靶点的高效低毒新型免疫抑制剂,如AEB071、PKC412、LY3176正处在临床前和临床研究阶段。结论随着研究的不断深入,会有更多的具有免疫抑制活性的蛋白激酶C抑制剂进入临床研究或上市。     

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H IV复制中的作用与药物发现

蛋白激酶C(PKC)是一类磷脂依赖的丝氨酸/苏氨酸蛋白激酶,PKC在中枢神经系统疾病及心血管紊乱等多种人类疾病中都发挥了重要作用。研究发现,PKC可以通过多种途径刺激H IV病毒的活化,并磷酸化病毒复制周期中的多种蛋白,如P17gag、Nef、Rev和V if等,这些蛋白的磷酸化在病毒复制周期中起到了不可忽视的作用。了解PKC与H IV及细胞间的复杂关系,开发抑制PKC蛋白激酶的药物从而达到抑制H IV复制的目的,或激活PKC从而减少或消除体内潜伏的H IV病毒库是对PKC在抗H IV研究中应用提出的两个主要方向,对于开发新型抗H IV药物有重要意义。     

蛋白激酶C在吴茱萸碱诱导A375-S2细胞死亡中的作用

目的研究蛋白激酶C(protein kinase C，PKC)在吴茱萸碱(evodiamine)诱导的A375-S2细胞死亡过程中的作用。方法TUNEL法检测吴茱萸碱诱导细胞凋亡的比例。MTT法测定药物对A375-S2细胞的细胞毒作用。Western blotting法分析药物作用后对ERK及其磷酸化蛋白和Bcl-2家族蛋白的影响。结果吴茱萸碱诱导A375-S2细胞的死亡在24 h以前以凋亡为主。PKC抑制剂staurosporine和ERK抑制剂PD98059均能促进吴茱萸碱诱导的A375-S2细胞死亡。吴茱萸碱能够抑制PKC的活力，下调ERK及其磷酸化蛋白的表达水平，并使Bax/Bcl-2表达比例上升。而staurosporine对吴茱萸碱抑制PKC活力，降低ERK及其磷酸化蛋白和Bcl-2的表达有进一步增强的作用。结论在吴茱萸碱诱导的A375-S2细胞死亡中，PKC位于ERK和Bcl-2的上游发挥其调节作用。     

冠心病患者血小板PKC、PKCI及红细胞PKC活性变化的研究

目的：研究蛋白激酶C（PKC）在冠心病的发生、发展中的作用。方法：测定87例心绞痛（AP）患者、91例急性心肌梗死（AMI）患者、90例健康对照（HC）者的血小板胞膜、胞浆PKC、胞浆蛋白激酶C抑制剂（PKCI）活性和红细胞膜、胞浆PKC活性。结果：AP组和AMI组血小板胞膜中PKC活性明显高于HC组,而胞浆中PKC活性明显低于HC组;AP组AMI组血小板胞浆中PKCI活性明显低于HC组;AP组和AMI组红细胞胞膜中PKC活性明显高于HC组,而胞浆中PKC活性低于HC组。结论：PKC可能参与冠心病的发病。     

蛋白激酶C的研究进展

阐述蛋白激酶C的生化性质,在肿瘤多药耐药中的作用及近年来研究发现的蛋白激酶C抑制剂。     

蛋白激酶C激活剂和抑制剂对小鼠腹腔巨噬细胞释出肿瘤坏死因子的影响

本文研究蛋白激酶C（PKC）激活剂TPA和抑制剂H－7，槲皮素对痤疮丙酸杆菌（Propionibacterium acnes,PA)启动的小鼠腹腔巨噬细胞（macrophage,MΦ）释出肿瘤坏死因子（TNF）的影响，表明TPA可诱导PA启动的M分泌TNF，其作用可被H－7和槲皮素抑制，LPS体外和体内诱生TNF的作用亦可被两者抑制，提示PKC和PA启动的M分泌TNF过程中具有关键性作用。     

ATP敏感性钾电流与蛋白激酶关系的研究

目的观察蛋白激酶A(PKA)及蛋白激酶C(PKC)抑制剂和蛋白脱磷酸化物质对大鼠心室肌细胞ATP敏感性钾电流 (IKATP)的影响 ,探讨克罗卡林 (cromakalim)开放ATP敏感性钾通道的作用机制。方法采用全细胞膜片钳技术记录心室肌细胞IKATP。结果在37℃时克罗卡林 (1μmol·L-1)可阻断ATP的抑制作用 ,诱导出IKATP。PKA抑制剂PKI(6～22)amide (1μmol·L -1),可模拟克罗卡林的作用 ,激活IKATP;而PKC抑制剂calphosticC无此作用。同时还观察到蛋白脱磷酸化物质butanedioemonoxime(BDM,5mmol·L -1)也可诱发出IKATP。结论克罗卡林开放IKATP 机制与抑制PKA的活性有关 ,而与PKC无关。     

冬凌草甲素增强U937细胞吞噬凋亡小体过程中ERK途径的调节作用

目的研究冬凌草甲素促进U937人淋巴瘤细胞分化的巨噬细胞吞噬凋亡小体的机制。方法光学显微镜下计数检测吞噬率,PKC活力检测盒测定PKC活力,吖啶橙染色,Hoechst 33258染色及W estern b lot法。结果酪氨酸蛋白激酶(PTK)抑制剂gen iste in和蛋白激酶C(PKC)广泛的抑制剂stauroporine均不同程度地抑制了冬凌草甲素诱导U937分化的巨噬细胞对凋亡小体的吞噬增强效果。2.7μmol.L-1的冬凌草甲素处理U937细胞后,时间依赖性地增加了PKC活力。ERK磷酸化抑制剂PD98059阻断了冬凌草甲素的吞噬增强作用。免疫印迹结果显示冬凌草甲素作用U937细胞后,ERK磷酸化程度增加,而PD98059逆转了ERK磷酸化。结论冬凌草甲素增强U937细胞对凋亡小体的吞噬作用,其吞噬机制是通过激活PTK和PKC激酶,导致下游ERK途径活化,从而增强吞噬过程。     

Fine tuning of protein kinase C (PKC) isoforms in cancer: shortening the distance from the laboratory to the bedside

The serine/threonine protein kinase C (PKC) family was first identified as intracellular receptor(s) for the tumor promoting agents phorbol esters. Thirty years after the discovery of PKC, the role of specific PKC isoforms has been described in relationship with an altered pattern of expression in different types of cancer and a good number of small molecule inhibitors (inhibitory peptides, antisense oligonucleotides or natural compounds) targeting PKC are now available. Despite all these achievements and a huge amount of basic research studies on the biochemical regulation of PKC, there has been a delay in clinical trials with drugs targeting PKC function. This delay is easily explained taking into account the extreme biological complexity of the PKC family of isoforms and the incomplete understanding of the specific role of each PKC isozyme in different types of cancers. Some of the difficulties in developing pharmacological compounds selectively tuning the different PKCs have started to be overcome. In this review, the growing evidences of the role of the PKC isoforms α, βII, δ, ε, ζ and ι is in promoting or counteracting tumor progression will be discussed in relationship with promising therapeutic perspectives.     

The pros and cons of targeting protein kinase C (PKC) in the management of cancer patients

In the last years, PKC has become an attractive target for the treatment of cancer patients given its widely described role in carcinogenesis and tumor promotion. Despite the extensive research conducted on these phorbol ester receptors there is only limited knowledge about the contribution of each individual PKC isozyme in malignant transformation, mainly due to the different roles of each isozyme and their tissue-specificity. This diversity provides the unique opportunity to develop specific pharmacological agents, but the complex nature of the signaling pathways activated by different PKCs challenges selective drug therapies. Currently, several classes of PKC inhibitors including small molecule kinase inhibitors, biologic modulators, and anti-sense oligonucleotides are being evaluated for the treatment of different cancers where PKC isozymes were found to be deregulated as lung, colon, skin, prostate, and breast malignancies. In this article we will review which PKC isoforms are deregulated in different human cancers and summarize the mechanism of action of some of the major PKC modulators, analyzing the strengths and weaknesses of each one in the clinical setting.     

Protein kinase C isozymes, novel phorbol ester receptors and cancer chemotherapy

Recent years have seen extensive growth in the understanding of the role(s) of the various PKC isozymes and novel receptors for the phorbol ester tumor promoters. The PKC family of serine-threonine kinases is an important regulator of signaling cascades that control cell proliferation and death, and therefore represent targets for cancer therapy. While past interests have focused on PKC-selective inhibitors, more recently, intensive research has been underway for selective activators and inhibitors for each individual PKC isozyme. In the past few years a large number of PKC activators and inhibitors with potential as anticancer agents have been developed. A number of these compounds are already in Phase II clinical testing. As a new generation of cancer chemotherapeutic agents are designed, developed and put through a series of rigorous clinical trials, we can anticipate achieving exquisite control over PKC-mediated regulatory pathways, leading ultimately to a greater understanding of different cancers.     

Targeting protein kinase C (PKC) in physiology and cancer of the gastric cell system

Protein kinase C (PKC) family members are multifunctional kinases that have been implicated in many cell biological and physiological tasks including acid, pepsinogen, and mucous production. Through the use of small-molecule PKC modulators, PKC has been found to be involved in gene expression, the control of cytoskeleton, membrane and secretagogue-dependent signal transduction for secretion of acid. Gastric carcinoma and adenocarcinoma cells often show dysregulated PKC-dependent cell signal transduction compared to normal gastric cells. Moreover, PKC was the first known target of tumor promoting phorbol esters. These findings support PKC as a potential chemotherapy target in gastric cancer. Various approaches have been launched in directly targeting PKC for chemotherapy of gastric cancer. The macrocyclic lactone bryostatin-1 is a promising agent that acts as a modulator of PKC activity, and enhances the effect of chemotherapeutic agents such as paclitaxel. This article provides an overview of the findings to date regarding the physiological role of PKC in the gastric cell system by various pharmacological approaches and examines PKC as a target in gastric (adeno-)carcinoma chemotherapy.     

Protein kinase C inhibitors: a patent review (2008 – 2009)

Introduction: The protein kinase C (PKC) is a family of multifunctional isoenzymes involved in apoptosis, migration, adhesion, tumorgenesis, cardiac hypertrophy, angiogenesis, platelet function and inflammation. It also plays a vital role in the regulation of signal transduction, cell proliferation and differentiation through positive and negative regulation of the cell cycle. In this work, we reviewed the existing PKC inhibitors and several patents linked to PKC inhibitors.

Areas covered: Thorough survey on the PKC inhibitors having clinical importance and patents filed for these inhibitors from 2008 – 2009 is reported.

Expert opinion: PKCs are highly potential therapeutic targets for treating diabetic complications, oncological, inflammatory, immunological and dermatological disorders. The clinical trial candidates of PKCs mainly target the catalytic domain, which is highly conserved throughout the PKC family making it difficult to target a particular isoform selectively. Relatively less chemical space and fewer bisubstrate inhibitors targeting both ATP and regulatory domain are explored for PKCs, more research in these areas will be helpful in overcoming existing problems.     

N-myristyl-Lys-Arg-Thr-Leu-Arg: a novel protein kinase C inhibitor

In view of the critical role that the Ca2+- and phospholipid-dependent enzyme protein kinase C (PKC) plays in mediating proliferative responses to a number of growth factors, hormones, and tumor promoters, it is thought that selective PKC inhibitors may provide a new class of antiproliferative drugs. Established PKC inhibitors include three major classes of agents: agents that compete with the substrate ATP, agents that compete with the protein substrate, and agents that both compete with ATP and interact with the cofactor phosphatidylserine (PS). In this report, we have characterized the interactions between PKC and N-myristyl-Lys-Arg-Thr-Leu-Arg, a myristylated analogue of a synthetic peptide substrate of PKC. We determined that the myristylated peptide was a novel PKC inhibitor that interacted with PS as well as competed with the protein substrate of PKC. The inhibitory activity of the peptide was conferred by myristylation. We found that the myristylated peptide antagonized Ca2+- and PS-activated PKC with an IC50 of 75 microns, whereas the nonmyristylated peptide lacked this inhibitory activity. A fully active, Ca2+- and PS-independent catalytic fragment of PKC can be generated by limited proteolysis. Although the myristylated peptide was a very poor PKC substrate, this peptide inhibited the catalytic fragment of PKC by apparent competition with the phosphoacceptor substrate histone IIIS with an IC50 of 200 microM, whereas the nonmyristylated peptide showed no inhibitory activity against the catalytic fragment. Thus, the myristylated peptide may serve as a model for the development of selective PKC inhibitors, because its inhibitory mechanism exploits the substrate specificity of PKC, as well as the novel regulation of the enzyme. Furthermore, since endogenous PKC substrates include acylated proteins, the observations that we report here concerning a myristylated synthetic peptide suggest that acylation of proteins may be important in the regulation of PKC activity in vivo.     

Modulating protein kinase C (PKC) to increase the efficacy of chemotherapy: stepping into darkness

The identification of molecules that promote chemotherapeutic resistance would allow rationally designed approaches to abrogate this resistance, thereby possibly improving clinical outcomes for patients with cancer. In this regard, the PKC family is attractive for targeting, because it is comprised of a family of isoforms that play key roles in multiple cellular processes and can contribute to cellular transformation. Encouraging in vitro data originally showed that approaches to modulate PKC activity through small-molecule inhibitors or genetic manipulation could affect tumor cell survival. Recently, some of these approaches have begun clinical testing. Early-stage clinical trials revealed scattered clinical responses to these agents, but the most recent clinical trials have shown that combining modulators of PKC with standard chemotherapy does not improve outcome over chemotherapy alone. In this review, we will trace the development of these approaches, and discuss possible explanations for the recent negative results. Importantly, we will suggest guidelines for the clinical evaluation of PKC modulators.     

Protein kinase C inhibitors as novel anticancer drugs

The role of PKC isoforms in signal transduction pathways involved in regulation of the cell cycle, apoptosis, angiogenesis, differentiation, invasiveness, senescence and drug efflux are reviewed, along with the clinical results on the current crop of PKC inhibitors, including midostaurin (PKC-412, CGP 41251, N-benzoylstaurosporine), UCN-01 (7-hydroxystaurosporine), bryostatin 1, perifosine, ilmofosine, Ro 31-8220, Ro 32-0432, GO 6976, ISIS-3521 (CGP 64128A) and the macrocyclic bis (indolyl) maleimides (LY-333531, LY-379196, LY-317615). An appreciation of the complex, often contradictory roles of PKC isoforms in signal transduction pathways involved in cancer is important for interpreting the clinical results observed with PKC inhibitors of varying selectivity. An antisense oligonucleotide, ISIS-3521 and two orally available small molecule inhibitors, LY 333531 and midostaurin, have now advanced to latter stage development for cancer and/or other indications. These compounds have varying levels of selectivity for the PKC isoforms and for the kinase and initial safety and early clinical efficacy have been encouraging. At this stage, the potential of PKC inhibition for the treatment of cancer has not been fully realised. The concurrent inhibition of multiple PKC isoforms may yet provide an improved clinical outcome in treating cancers in view of the complex interrelated roles of the PKC isoforms.