Akt/PKB信号转导通路与脑缺血

Akt被生长因子介导的受体酪氨酸激酶磷酸化激活后可激活一系列底物分子,包括Forkhead转录因子等,对细胞生存和死亡进行调控.随着脑缺血后Akt磷酸化水平(Ser473)的改变,其上游、下游蛋白磷酸化水平也发生变化.预处理可能通过改变Akt蛋白磷酸化水平而产生缺血耐受.Akt/PKB信号转导通路功能障碍可能介导了脑缺血后神经元死亡.     

p-Akt和P27的生物学特性及其与鼻咽癌关系的研究进展

蛋白激酶B（PKB／Akt）磷酸化后激活为p-Akt,可以促进细胞存活、抑制细胞凋亡,并调控与细胞周期相关的蛋白,磷酸肌醇3-激酶（P13K）／AKT信号转导通路促进恶性肿瘤转移。P27蛋白作为细胞周期负性调控因子,能抑制各种细胞周期蛋白和激酶的活性。P27表达下降或者缺失,促进了肿瘤的增殖和侵袭。两者都在鼻咽癌的发病和转移中起作用,并对预后有影响。     

Akt/FoxO传导通路调节细胞凋亡作用的研究进展

Foxo转录因子是PKB／Akt的下游靶点。Akt调节细胞生存和增殖。Akt磷酸化Foxo抑制Fox0的转录功能,促进细胞生存、生长和增殖。在癌症中FoxO在不同的细胞信号通路中发挥重要作用。FoxO通过两个途径抑制凋亡信号,促进细胞生长,其包括线粒体靶点蛋白Bcll2家族的多种前凋亡成员的表达、死亡受体配体如Fas配体和肿瘤坏死因子相关凋亡诱导配体（TRAIL）的表达,或是增加各种细胞周期蛋白依赖性激酶抑制蛋白的水平。本文主要概括了Akt／FoxO调节细胞生长和生存的机制,以期为抗癌治疗提供新的可能。     

新的抗肿瘤靶点Akt与胰腺癌分子靶向治疗

Akt/PKB是一种丝氨酸/苏氨酸蛋白激酶,属于cAMP依赖的蛋白激酶A、蛋白激酶G、蛋白激酶C(AGC)超家族,它是PI3K/Akt通路中的关键分子,通过磷酸化mTOR、Bad、GSK3、mdm2、caspase家族、Forkhead家族等多种作用底物,在促进肿瘤细胞的生长、增殖,抑制细胞凋亡,促使细胞侵袭和转移,促进血管生成,抵抗化疗和放疗中细胞的凋亡等方面起重要作用[1].最近在许多人类肿瘤中发现,PKB/Akt信号通路异常与肿瘤发生、发展关系密切,Akt可能成为抗肿瘤治疗的一个新靶点.胰腺癌的发生与表皮生长因子受体(EGFR)和它的下游信号通路ras-Raf-MEK-ERK,PI3K/Akt和核因子κB(NF-κB)通路有重要关系.其中PI3K/Akt通路除了其潜在的促生长能力外,它的抗凋亡作用和肿瘤细胞对广谱凋亡刺激的抵抗性有密切关系.因此,PI3K/Akt通路可能是胰腺癌分子靶向治疗的一个潜在新靶点.     

核转录因子E2Fs家族研究进展

核转录因子E2Fs家族 (E2F转录因子 )是视网膜母细胞瘤相关基因 (RB/E2F)通路中调控细胞有丝分裂事件的重要因子 ,E2F是否进入核内发挥核转录因子作用取决于RB蛋白的磷酸化状态 ,E2F调控的下游基因分为激活与抑制两种方式 ,涉及细胞周期调控、生长与凋亡、增殖与分化等重要生命活动。E2F在细胞周期中的功能失调将导致细胞上述机能的改变并有可能与肿瘤发生有关 ,深入研究无疑将对完整阐述细胞周期调控及肿瘤发生机制乃至寻求新的肿瘤治疗靶点提供帮助。     

新的抗肿瘤靶点Akt与胰腺癌分子靶向治疗

Akt／PKB是一种丝氨酸／苏氨酸蛋白激酶．属于cAMP依赖的蛋白激酶A、蛋白激酶G、蛋白激酶C（AGC）超家族．它是P13K/Akt通路中的关键分子．通过磷酸化mTOR、Bad、GSK3、mdm2、caspase家族、Forkhead家族等多种作用底物．在促进肿瘤细胞的生长、增殖．抑制细胞凋亡．促使细胞侵袭和转移．促进血管生成．抵抗化疗和放疗中细胞的凋亡等方面起重要作用。最近在许多人类肿瘤中发现．PKB／Akt信号通路异常与肿瘤发生、发展关系密切．     

PI3K-Akt/PKB信号通路与胰岛β细胞功能

磷脂酰肌醇3激酶-蛋白激酶B/Akt(PI3K-Akt/PKB)介导β细胞的生存通路近来较受关注。PI3K-Akt/PKB信号通路是细胞内重要的信号转导通路,与细胞生长、增殖、分化、凋亡等密切相关。PI3K-Akt/PKB信号通路激活通过下游效应分子促进β细胞增殖、生长调节、增强β细胞抗凋亡功能,改善β细胞生存。调节该通路PI3K、Akt/PKB及其上下游靶位点,可能为2型糖尿病的防治提供广阔前景。     

Akt与β细胞生存和功能

Akt是在多种组织和细胞表达的一种丝氨酸/苏氨酸激酶,接受磷脂酰肌醇3激酶-Akt-磷酸肌醇依赖性激酶信号通路调节而发生构象变化,显露其磷酸化位点而被激活.研究发现,胰岛中Akt主要表达于β细胞,一方面通过其下游效应子核糖体S6激酶1和细胞周期素依赖激酶/细胞周期素的调节,以及阻断细胞凋亡信号通路来促进β细胞的生存、增殖和分化;另一方面通过调节胰岛素分泌通路末梢的信号分子和葡萄糖代谢等促进β细胞正常功能的维持.因而可能为糖尿病的治疗提供一个新的靶点.     

核转录因子E2Fs家族研究进展

核转录因子E2Fs家族(E2F转录因子)是视网膜母细胞瘤相关基因(RB／E2F)通路中调控细胞有丝分裂事件的重要因子，E2F是否进入核内发挥核转录因子作用取决于RB蛋白的磷酸化状态，E2F调控的下游基因分为激活与抑制两种方式，涉及细胞周期调控、生长与凋亡、增殖与分化等重要生命活动。E2F在细胞周期中的功能失调将导致细胞上述机能的改变并有可能与肿瘤发生有关，深入研究无疑将对完整阐述细胞周期调控及肿瘤发生机制乃至寻求新的肿瘤治疗靶点提供帮助。     

Akt与β细胞生存和功能

Akt是在多种组织和细胞表达的一种丝氨酸/苏氨酸激酶,接受磷脂酰肌醇3激酶-Akt-磷酸肌醇依赖性激酶信号通路调节而发生构象变化,显露其磷酸化位点而被激活。研究发现,胰岛中Akt主要表达于β细胞,一方面通过其下游效应子核糖体S6激酶1和细胞周期素依赖激酶/细胞周期素的调节,以及阻断细胞凋亡信号通路来促进β细胞的生存、增殖和分化;另一方面通过调节胰岛素分泌通路末梢的信号分子和葡萄糖代谢等促进β细胞正常功能的维持。因而可能为糖尿病的治疗提供一个新的靶点。     

A member of Forkhead family transcription factor, FKHRL1, is one of the downstream molecules of phosphatidylinositol 3-kinase-Akt activation pathway in erythropoietin signal transduction

The phosphatidylinositol 3-kinase (PI3K) signaling pathway is important for the regulation of a number of cellular responses. Serine/threonine kinase Akt (protein kinase B; PKB) is downstream of PI3K and activated by growth factors. This study found that erythropoietin (EPO) induced tyrosine phosphorylation of Akt in a time- and dose-dependent manner in EPO-dependent human leukemia cell line UT-7/EPO. In vitro kinase assay using histone H2B and glucose synthase kinase as substrates demonstrated that Akt was actually activated by EPO. EPO-induced phosphorylation of Akt was completely blocked by a PI3K-specific inhibitor, LY294002, at 10 micromol/L, indicating that activation of Akt by EPO is dependent on PI3K activity. In addition, overexpression of the constitutively active form of Akt on UT-7/EPO cells partially blocked apoptosis induced by withdrawal of EPO from the culture medium. This finding suggested that the PI3K-Akt activation pathway plays some role in the antiapoptotic effect of EPO. EPO induced phosphorylation of a member of the trancription factor Forkhead family, FKHRL1, at threonine 32 and serine 253 in a dose- and time-dependent manner in UT-7/EPO cells. Moreover, results showed that Akt kinase activated by EPO directly phosphorylated FKHRL1 protein and that FKHRL1 phosphorylation was completely dependent on PI3K activity as is the case for Akt. In conjunction with the evidence that FKHRL1 is expressed in normal human erythroid progenitor cells and erythroblasts, the results suggest that FKHRL1 plays an important role in erythropoiesis as one of the downstream target molecules of PI3K-Akt.     

Inhibition of integrin-linked kinase (ILK) suppresses activation of protein kinase B/Akt and induces cell cycle arrest and apoptosis of PTEN-mutant prostate cancer cells

PTEN is a tumor suppressor gene located on chromosome 10q23 that encodes a protein and phospholipid phosphatase. Somatic mutations of PTEN are found in a number of human malignancies, and loss of expression, or mutational inactivation of PTEN, leads to the constitutive activation of protein kinase B (PKB)/Akt via enhanced phosphorylation of Thr-308 and Ser-473. We recently have demonstrated that the integrin-linked kinase (ILK) can phosphorylate PKB/Akt on Ser-473 in a phosphoinositide phospholipid-dependent manner. We now demonstrate that the activity of ILK is constitutively elevated in a serum- and anchorage-independent manner in PTEN-mutant cells, and transfection of wild-type (WT) PTEN into these cells inhibits ILK activity. Transfection of a kinase-deficient, dominant-negative form of ILK or exposure to a small molecule ILK inhibitor suppresses the constitutive phosphorylation of PKB/Akt on Ser-473, but not on Thr-308, in the PTEN-mutant prostate carcinoma cell lines PC-3 and LNCaP. Transfection of dominant-negative ILK and WT PTEN into these cells also results in the inhibition of PKB/Akt kinase activity. Furthermore, dominant-negative ILK or WT PTEN induces G(1) phase cycle arrest and enhanced apoptosis. Together, these data demonstrate a critical role for ILK in PTEN-dependent cell cycle regulation and survival and indicate that inhibition of ILK may be of significant value in PTEN-mutant tumor therapy.