FoxO转录因子的活性调节及对哺乳动物细胞进程的调控

FoxO转录因子在哺乳动物的细胞分化、增殖和细胞存活中发挥着重要调控作用,其转录活性受PI3K通路、非PI3K依赖通路、乙酰化和泛素化作用等多种途径调控.FoxO受到上游信号分子PI3K/Akt、SGK等的激活,调节靶基因的转录,从而调节哺乳动物细胞周期的进程和凋亡事件.FoxO已成为肿瘤、癌症科学研究的热点之一.     

Mammalian target of rapamycin complex 2 (mTORC2) negatively regulates Toll-like receptor 4-mediated inflammatory response via FoxO1

Activation of the PI3K pathway plays a pivotal role in regulating the inflammatory response. The loss of mTORC2 has been shown to abrogate the activation of Akt, a critical downstream component of PI3K signaling. However, the biological importance of mTORC2 in innate immunity is currently unknown. Here we demonstrate that rictor, a key component of mTORC2, plays a critical role in controlling the innate inflammatory response via its ability to regulate FoxO1. Upon LPS stimulation, both rictor-deficient mouse embryonic fibroblasts (MEFs) and rictor knockdown dendritic cells exhibited a hyperinflammatory phenotype. The hyperinflammatory phenotype was due to a defective Akt signaling axis, because both rictor-deficient MEFs and rictor knockdown dendritic cells exhibited attenuated Akt phosphorylation and kinase activity. Analysis of downstream Akt targets revealed that phosphorylation of FoxO1 was impaired in rictor-deficient cells, resulting in elevated nuclear FoxO1 levels and diminished nuclear export of FoxO1 upon LPS stimulation. Knockdown of FoxO1 attenuated the hyperinflammatory phenotype exhibited by rictor-deficient MEFs. Moreover, FoxO1 deletion in dendritic cells attenuated the capacity of LPS to induce inflammatory cytokine expression. These findings identify a novel signaling pathway by which mTORC2 regulates the TLR-mediated inflammatory response through its ability to regulate FoxO1.     

基于疾病与活性化合物靶点网络构建的异鼠李素抗缺血性神经损伤作用评价与验证研究

基于网络药理学与分子对接探讨异鼠李素对缺血性神经损伤的治疗作用。采用ChEMBL、SwissTargetPrediction、DrugBank、STITCH及BindingDB数据库检索异鼠李素药理学靶点,应用DisGeNET、GenCLiP及CTD数据库检索缺血性神经损伤的疾病靶点,取交集作为异鼠李素对缺血性神经损伤的治疗靶点,并进行表型分析。将交集靶点导入STRING构建蛋白互作网络,使用Network analyser进行拓扑分析,同时应用MODE构建功能模块,并基于ClueGo对功能模块进行分析。之后应用DAVID数据库对治疗靶点进行GO及KEGG富集分析。利用Discovery Studio评价异鼠李素与核心靶点的结合活性,最后建立OGD/R损伤PC12细胞模型,采用MTT和LDH法检测细胞活力,Western blot法对AKT1、IL6和MMP2的表达进行检测。异鼠李素通过50个缺血性神经损伤相关靶点,调控细胞凋亡、转录、蛋白质磷酸化、炎症反应等生物学过程,干预PI3K-AKT信号通路、HIF-1信号通路、雌激素信号通路、肿瘤坏死因子信号通路、FoxO信号通路等多条途径发挥抗缺血性神经损伤的作用。初步阐释异鼠李素治疗缺血性神经损伤的作用,涉及多靶点、多通路,为进一步探究其药理学活性奠定理论基础。     

Interleukin-6 up-regulates the expression of interleukin-15 is associated with MAPKs and PI3-K signaling pathways in the human keratinocyte cell line,HaCaT

Interleukin (IL)-15 is an important inflammatory cytokine and plays a key role in autoimmune disease. At present, IL-15 gene expression and regulation related to many innate immunity trigger signals have been clarified in some specific cell types, but the relationship of IL-6 and IL-15 in the human keratinocyte cell line (HaCaT) is unknown. In this study, we investigated the effect of IL-6 on the expression of IL-15 and selected signaling pathways in HaCaT cells. Results demonstrated that IL-6 up-regulated the expression of IL-15 both at the mRNA and protein levels. Meanwhile, IL-6 was able to activate MAPKs-ERK1/2 and PI3K-AKT signaling pathways. Furthermore, the high expression of IL-15 induced by IL-6 was down-regulated while MAPKs-ERK1/2 and PI3K-AKT signaling pathways were, respectively, blocked by PD98059 and LY294002. These findings indicate that the expression of IL-15 up-regulated by IL-6 is associated with MAPKs-ERK1/2 and PI3K-AKT signaling pathways in HaCaT cells.     

Trim32 reduces PI3K–Akt–FoxO signaling in muscle atrophy by promoting plakoglobin–PI3K dissociation

Activation of the PI3K–Akt–FoxO pathway induces cell growth, whereas its inhibition reduces cell survival and, in muscle, causes atrophy. Here, we report a novel mechanism that suppresses PI3K–Akt–FoxO signaling. Although skeletal muscle lacks desmosomes, it contains multiple desmosomal components, including plakoglobin. In normal muscle plakoglobin binds the insulin receptor and PI3K subunit p85 and promotes PI3K–Akt–FoxO signaling. During atrophy, however, its interaction with PI3K–p85 is reduced by the ubiquitin ligase Trim32 (tripartite motif containing protein 32). Inhibition of Trim32 enhanced plakoglobin binding to PI3K–p85 and promoted PI3K–Akt–FoxO signaling. Surprisingly, plakoglobin overexpression alone enhanced PI3K–Akt–FoxO signaling. Furthermore, Trim32 inhibition in normal muscle increased PI3K–Akt–FoxO signaling, enhanced glucose uptake, and induced fiber growth, whereas plakoglobin down-regulation reduced PI3K–Akt–FoxO signaling, decreased glucose uptake, and caused atrophy. Thus, by promoting plakoglobin–PI3K dissociation, Trim32 reduces PI3K–Akt–FoxO signaling in normal and atrophying muscle. This mechanism probably contributes to insulin resistance during fasting and catabolic diseases and perhaps to the myopathies and cardiomyopathies seen with Trim32 and plakoglobin mutations.