磷脂酰肌醇-3-激酶/蛋白激酶B/雷帕霉素靶蛋白信号转导研究进展及与自身免疫病的关系

磷脂酰肌醇-3-激酶/蛋白激酶B/雷帕霉素靶蛋白(PI3K/Akt/mTOR)信号通路介导许多在肿瘤和自身免疫病发生中至关重要的细胞生物学过程,对于细胞增殖、细胞活化、血管生成起到重要作用.PI3 K/Akt/mTOR信号通路作为药物治疗靶点进行抗细胞增殖活化的研究近年来发展迅速.本文从PI3K/Akt/mTOR信号通路的上下游、信号通路抑制剂以及与信号通路相关的自身免疫病等方面作一综述.     

mTOR信号通路与动脉粥样硬化

mTOR是一种丝氨酸/苏氨酸激酶,主要参与到两种信号通路的调节中。mTOR信号通路具有调控细胞生长、自噬、增殖和凋亡等生物学功能。mTOR可以调控动脉粥样硬化发生发展过程中内皮细胞的增殖与迁移、巨噬细胞的自噬和平滑肌细胞的增殖与迁移。通过不同时期抑制或激活mTOR可以稳定动脉粥样硬化易损斑块,防止动脉粥样硬化的发生发展。mTOR信号通路在动脉粥样硬化进展中发挥了多方面效应,本文主要针对mTOR信号通路与动脉粥样硬化做一综述,为临床治疗提供新的研究方向。     

mTOR信号通路与衰老

哺乳动物雷帕霉素靶蛋白(mammalian target of rapamycin,mTOR)是一种进化上十分保守的丝氨酸/苏氨酸蛋白激酶,能对氨基酸、应激、氧、能量和生长因子等信号作出应答,并将信号传导到下游,最终调节细胞的生长和增殖.近几年研究发现,降低无脊椎模式生物中TOR通路的活性可增加寿命,雷帕霉素可延长实验鼠的寿命,表明mTOR通路与机体衰老过程的调控具有密切关系研究mTOR通路与衰老的关系及其调节衰老的机制对延迟多种病理发展并最终延长人类寿命具有重要意义     

STING信号通路参与NAFLD的研究进展

非酒精性脂肪肝疾病(non-alcoholic fatty liver disease,NAFLD)是全球范围内的主要慢性肝病之一,严重威胁人类健康,已成为一个重大的公共卫生问题.免疫机制在NAFLD的发生发展中起着关键作用.干扰素基因刺激因子(interferon gene stimulating factor, STING)是机体免疫系统的一个关键性接头蛋白,其相关信号通路作为新近的一个研究热点,可能通过介导肝脏炎症、脂质代谢以及细胞凋亡等过程影响肝脏的代谢稳态从而参与NAFLD的发生发展.本文结合相关报道和最新文献,从NAFLD与免疫、STING信号通路的组成以及STING信号通路与NAFLD之间的关系三方面做了一综述,以期为进一步深入的研究STING信号通路与NAFLD之间的复杂关系以及开发相关靶向药物提供帮助和思路.     

mTOR信号传导通路及其相关药物与非小细胞肺癌

哺乳动物雷帕霉素靶蛋白(mTOR)处于细胞生长繁殖、细胞周期调控、生物合成、细胞迁移等信号通路调控的中心位置,因此在肿瘤以及肺癌的发生、发展,特别是在治疗和预后中具有重要的作用.mTOR磷酸化激活后,通过调控4EBP和P70S6K两条不同的下游通路,分别控制特定亚组mRNA的翻译,进而影响生物合成.对非小细胞肺癌来讲,mTOR能够加快细胞周期G1-S期的转换,促进细胞增殖.雷帕霉素、西罗莫司、依维莫司等mTOR信号通路的阻断药物在肺癌的治疗中显示出了希望.     

mTOR信号通路与肝星状细胞功能的关系

肝星状细胞(hepatic stellate cells,HSCs)的活化被普遍认为是形成肝纤维化的中心环节.各种因素可通过多种信号通路来调节HSCs的功能,其中哺乳动物雷帕霉素靶蛋白(mammalian target of rapamycin,mTOR)信号通路是重要的一条通路.因此,深入研究mTOR信号通路与HSCs增殖、凋亡、自噬、衰老的关系,可为临床上肝纤维化的治疗提供新的靶点及方法.本文就mTOR信号通路与HSCs功能关系的研究进展作一综述.     

mTOR通路与Peutz-Jeghers综合征

哺乳动物雷帕霉素靶蛋白(mammalian target of rapamycin,mTOR)所介导的细胞信号通路参与基因转录、蛋白翻译、核糖体合成、细胞凋亡等生物活动,是细胞内重要信号通路之一.其异常活化对某些遗传性疾病、肿瘤和糖尿病的发生关系密切.如何通过各种生物学手段影响该信号传导通路,从而对相关疾病的发生、治疗、转归、预后进行干预也成为现在研究的热点.本文结合近年来学者对mTOR信号通路的组成结构、功能及其在常染色体显性遗传病-Peutz-Jeghers综合征(Peutz-Jeghers syndrome,PJS)中作用的研究进展进行综述,以期能为以mTOR信号通路为靶点的分子靶向治疗应用于PJS的预防性治疗提供理论参考.     

mTORC2信号通路调节上皮细胞钠通道的研究进展

哺乳动物雷帕霉素靶蛋白(mammalian target of rapamycin,mTOR)是一种丝氨酸/苏氨酸蛋白激酶,属于磷脂酰肌醇激酶相关激酶蛋白质家族成员。mTOR进化上高度保守,可整合营养、能量及生长因子等多种细胞外信号,在细胞生长、增殖、凋亡及自噬等过程中发挥极为重要的作用。在生物体内,mTOR有2种多蛋白复合物:mTORC1和mTORC2,目前mTORC1信号通路与肿瘤的关系研究较多,而对mTORC2的研究相对较少,近年来有研究发现mTORC2信号通路参与了上皮细胞钠通道的调节作用。     

mTOR信号通路与非小细胞肺癌研究进展

哺乳动物雷帕霉素靶蛋白(mammalian target of rapamycin,mTOR)在细胞生长、增殖、分化、周期调控等多个方面扮演重要角色.mTOR信号通路的调控异常与非小细胞肺癌(non-small cell lung cancer,NSCLC)的发生、发展,特别是治疗及转归密切相关.在很多NSCLC患者中,存在mTOR信号通路的异常激活.多项令人鼓舞的临床前试验及临床试验数据提示,mTOR抑制剂在NSCLC的靶向治疗中显示出良好的应用前景.     

哺乳动物雷帕霉素靶蛋白C1(mTORC1)在非酒精性脂肪性肝病治疗中的作用机制及潜力

非酒精性脂肪性肝病(NAFLD)已成为全球最常见的慢性肝病，可进展为非酒精性脂肪性肝炎、肝硬化和肝癌。哺乳动物雷帕霉素靶蛋白(mTOR)是一种非典型丝氨酸/苏氨酸蛋白激酶，在细胞生长、凋亡、自噬及代谢等过程中发挥了极为重要的作用。本文阐述mTORC1信号通路在NAFLD发病过程中对细胞代谢和生长分化的作用，进一步提出mTORC1通路对于NAFLD治疗药物的研究价值和潜力。     

雷帕霉素靶分子在糖尿病肾病发病机制中的作用

哺乳动物雷帕霉素靶分子位于胰岛素/胰岛素样生长因子通路的下游,同时接受营养信号和能量信号,参与细胞、器官和生物体肥胖的调控,引起胰岛素抵抗,促进血管内皮细胞生长因子的表达,可能在2型糖尿病及糖尿病肾病的发生发展中起重要的作用.     

The coordinate regulation of the p53 and mTOR pathways in cells

Cell growth and proliferation requires an intricate coordination between the stimulatory signals arising from nutrients and growth factors and the inhibitory signals arising from intracellular and extracellular stresses. Alteration of the coordination often causes cancer. In mammals, the mTOR (mammalian target of rapamycin) protein kinase is the central node in nutrient and growth factor signaling, and p53 plays a critical role in sensing genotoxic and other stresses. The results presented here demonstrate that activation of p53 inhibits mTOR activity and regulates its downstream targets, including autophagy, a tumor suppression process. Moreover, the mechanisms by which p53 regulates mTOR involves AMP kinase activation and requires the tuberous sclerosis (TSC) 1/TSC2 complex, both of which respond to energy deprivation in cells. In addition, glucose starvation not only signals to shut down mTOR, but also results in the transient phosphorylation of the p53 protein. Thus, p53 and mTOR signaling machineries can cross-talk and coordinately regulate cell growth, proliferation, and death.     

Inhibition of the mTORC1 pathway suppresses intestinal polyp formation and reduces mortality in ApcDelta716 mice

The mammalian target of rapamycin (mTOR) is a serine/threonine kinase that regulates cell growth via mTOR complex 1 (mTORC1), whose activation has been implicated in many human cancers. However, mTORC1's status in gastrointestinal tumors has not been characterized thoroughly. We have found that the mTORC1 pathway is activated with increased expression of the mTOR protein in intestinal polyps of the Apc^Δ716 heterozygous mutant mouse, a model for human familial adenomatous polyposis. An 8-week treatment with RAD001 (everolimus) suppressed the mTORC1 activity in these polyps and inhibited proliferation of the adenoma cells as well as tumor angiogenesis, which significantly reduced not only the number of polyps but also their size. β-Catenin knockdown in the colon cancer cell lines reduced the mTOR level and thereby inhibited the mTORC1 signaling. These results suggest that the Wnt signaling contributes to mTORC1 activation through the increased level of mTOR and that the activation plays important roles in the intestinal polyp formation and growth. Indeed, long-term RAD001 treatment significantly reduced mortality of the Apc^Δ716 mice. Thus, we propose that the mTOR inhibitors may be efficacious for therapy and prevention of colonic adenomas and cancers with Wnt signaling activation.     

The NF1 tumor suppressor critically regulates TSC2 and mTOR

Loss-of-function mutations in the NF1 tumor suppressor gene underlie the familial cancer syndrome neurofibromatosis type I (NF1). The NF1-encoded protein, neurofibromin, functions as a Ras-GTPase activating protein (RasGAP). Accordingly, deregulation of Ras is thought to contribute to NF1 development. However, the critical effector pathways involved in disease pathogenesis are still unknown. We show here that the mTOR pathway is tightly regulated by neurofibromin. mTOR is constitutively activated in both NF1-deficient primary cells and human tumors in the absence of growth factors. This aberrant activation depends on Ras and PI3 kinase, and is mediated by the phosphorylation and inactivation of the TSC2-encoded protein tuberin by AKT. Importantly, tumor cell lines derived from NF1 patients, and a genetically engineered cell system that requires Nf1-deficiency for transformation, are highly sensitive to the mTOR inhibitor rapamycin. Furthermore, while we show that the activation of endogenous Ras leads to constitutive mTOR signaling in this disease state, we also demonstrate that in normal cells Ras is differentially required for mTOR signaling in response to various growth factors. Thus, these findings identify the NF1 tumor suppressor as an indispensable regulator of TSC2 and mTOR. Furthermore, our results also demonstrate that Ras plays a critical role in the activation of mTOR in both normal and tumorigenic settings. Finally, these data suggest that rapamycin, or its derivatives, may represent a viable therapy for NF1.     

Cardiovascular disease and mTOR signaling

The cell signaling pathways of the mammalian target of rapamycin (mTOR) are broad in nature but are tightly integrated through the protein complexes of mTORC1 and mTORC2. Although both complexes share some similar subcomponents, mTORC1 is primarily associated with the regulatory protein Raptor, whereas mTORC2 relies on Rictor. Pathways of mTOR that partner with Wnt as well as growth factor signaling are vital for endothelial and cardiomyocyte growth. In mature differentiated endothelial cells and cardiac cells, mTOR activation regulates both apoptotic and autophagic pathways during oxidative stress that can be dependent on the activation of protein kinase B. These protective pathways of mTOR can promote angiogenesis and limit acute cell death to foster cardiac repair and tissue regeneration. However, under some conditions, blockade of mTOR pathways may be necessary to limit vasculopathy and promote microcirculatory flow. Future work that further elucidates the vital regulatory pathways of mTOR can offer new therapeutic insights for the treatment of cardiovascular diseases.     

Ras, PI3-kinase and mTOR signaling in cardiac hypertrophy

Cardiac hypertrophy involves increased mass (growth) of the heart and a cardinal feature of this condition is increased rates of protein synthesis. Several signaling pathways have been implicated in cardiac hypertrophy including the phosphatidylinositol 3-kinase (PI3K) and Ras/Raf/MEK/Erk pathways. PI3K lies upstream of the mammalian target of rapamycin (mTOR), an important positive regulator of protein synthesis and cell growth. However, recent data suggest that, in response to certain hypertrophic agents, signaling via Ras and MEK/Erk, as well as mTOR, is required for activation of protein synthesis, indicating new connections between these key signaling pathways.     

Metformin inhibits growth and decreases resistance to anoikis in medullary thyroid cancer cells

Medullary thyroid cancer (MTC) is associated with activation of mammalian target of rapamycin (mTOR) signaling pathways. Recent studies showed that the antidiabetic agent metformin decreases proliferation of cancer cells through 5'-AMP-activated protein kinase (AMPK)-dependent inhibition of mTOR. In the current study, we assessed the effect of metformin on MTC cells. For this purpose, we determined growth, viability, migration, and resistance to anoikis assays using two MTC-derived cell lines (TT and MZ-CRC-1). Expressions of molecular targets of metformin were examined in MTC cell lines and in 14 human MTC tissue samples. We found that metformin inhibited growth and decreased expression of cyclin D1 in MTC cells. Treatment with metformin was associated with inhibition of mTOR/p70S6K/pS6 signaling and downregulation of pERK in both TT and MZ-CRC-1 cells. Metformin had no significant effects on pAKT in the cell lines examined. Metformin-inducible AMPK activation was noted only in TT cells. Treatment with AMPK inhibitor (compound C) or AMPK silencing did not prevent growth inhibitory effects of metformin in TT cells. Metformin had no effect on MTC cell migration but reduced the ability of cells to form multicellular spheroids in nonadherent conditions. Immunostaining of human MTC showed over-expression of cyclin D1 in all tumors compared with corresponding normal tissue. Activation of mTOR/p70S6K was detected in 8/14 (57.1%) examined tumors. Together, these findings indicate that growth inhibitory effects in MTC cells are associated with downregulation of both mTOR/6SK and pERK signaling pathways. Expression of metformin's molecular targets in human MTC cells suggests its potential utility for the treatment of MTC in patients.     

The AMPK agonist AICAR inhibits the growth of EGFRvIII-expressing glioblastomas by inhibiting lipogenesis

The EGFR/PI3K/Akt/mTOR signaling pathway is activated in many cancers including glioblastoma, yet mTOR inhibitors have largely failed to show efficacy in the clinic. Rapamycin promotes feedback activation of Akt in some patients, potentially underlying clinical resistance and raising the need for alternative approaches to block mTOR signaling. AMPK is a metabolic checkpoint that integrates growth factor signaling with cellular metabolism, in part by negatively regulating mTOR. We used pharmacological and genetic approaches to determine whether AMPK activation could block glioblastoma growth and cellular metabolism, and we examined the contribution of EGFR signaling in determining response in vitro and in vivo. The AMPK-agonist AICAR, and activated AMPK adenovirus, inhibited mTOR signaling and blocked the growth of glioblastoma cells expressing the activated EGFR mutant, EGFRvIII. Across a spectrum of EGFR-activated cancer cell lines, AICAR was more effective than rapamycin at blocking tumor cell proliferation, despite less efficient inhibition of mTORC1 signaling. Unexpectedly, addition of the metabolic products of cholesterol and fatty acid synthesis rescued the growth inhibitory effect of AICAR, whereas inhibition of these lipogenic enzymes mimicked AMPK activation, thus demonstrating that AMPK blocked tumor cell proliferation primarily through inhibition of cholesterol and fatty acid synthesis. Most importantly, AICAR treatment in mice significantly inhibited the growth and glycolysis (as measured by ¹⁸fluoro-2-deoxyglucose microPET) of glioblastoma xenografts engineered to express EGFRvIII, but not their parental counterparts. These results suggest a mechanism by which AICAR inhibits the proliferation of EGFRvIII expressing glioblastomas and point toward a potential therapeutic strategy for targeting EGFR-activated cancers.