PI3K信号通路调控动脉粥样硬化发生发展的研究进展

磷脂酰肌醇3激酶(PI3K)信号通路参与动脉粥样硬化、肿瘤及免疫系统疾病的发生、发展。调节PI3K可以调控细胞凋亡、自噬、炎性反应等病理生理过程,为疾病的治疗提供了新思路。     

肿瘤中磷脂酰肌醇信号系统的作用

磷脂酰肌醇信号系统是一个由酶、磷脂信使及其结合蛋白组成的复杂的细胞调节系统,对细胞的生长、增殖、存活以及细胞运动起着重要的调节作用。激活磷脂信使的酶若发生突变,将会导致磷脂酰肌醇信号系统高度激活,磷脂酰肌醇过度激活将会导致细胞增殖异常,胞吞胞吐异常以及细胞转移异常甚至肿瘤发生。由于磷脂酰肌醇信号系统在肿瘤增殖生长及其转移中的重要性,磷脂酰肌醇系统的各个组分很有可能成为好的临床治疗靶点,越来越多针对这一通路的药物逐步走向临床,磷脂酰肌醇3激酶（ PI3 K）抑制剂wortmannin、 LY294002等能够快速靶向PI3K,抑制肿瘤中AKT的磷酸化,阻止其对下游生长信号进行活化。 mTOR抑制剂rapamycin能够靶向mTOR,在非小细胞肺癌、乳腺癌、宫颈癌、肉瘤、淋巴瘤和胶质瘤等癌症中的治疗效果非常明显。除靶向药物外更有膜上的磷脂酰肌醇分布动态监测系统问世,为肿瘤的临床治疗提供新思路。     

INPP5E基因与胚胎神经发育相关研究

肌醇多聚磷酸5-磷酸酶基因(inositol polyphosphate-5-phosphatase,INPP5E)所编码的肌醇多聚磷酸5-磷酸酶(INPP5E)调节磷酸肌醇信号通路的活性,INPP5E参与催化PI(3,4,5)P3与PI(4,5)P2分别生成PI(3,4)P2与PI4P,INPP5E正常表达调控神经管发育过程,从而影响哺乳动物正常神经发育过程。该基因突变可导致神经管畸形(neural tube defects,NTDs)、茹贝尔综合征(Joubert syndrome)、MORM综合征等神经系统疾病。本文对INPP5E基因与胚胎神经发育相关研究进展进行综述,期望进一步了解INPP5E基因在胚胎神经发育中的作用及机制,以寻求其突变相关疾病的发病机制及其防治方法。     

抑癌基因PTEN与肿瘤的研究进展

PTEN基因是目前发现的第一个具磷酸酶活性的抑癌基因,与数种具肿瘤倾向的遗传性疾病及多种散发性肿瘤有关。PTEN能特异性地使磷脂酰肌醇-3,4,5三磷酸[PIP3]去磷酸化,而拮抗PI3K/AKT信号通路发挥作用。PTEN具有调节细胞生长、增殖、迁移等多种效应。     

PIPP与PTEN对黑色素瘤的抑制作用

黑色素瘤(melanoma)细胞周期的主要负调控物P21和P27的表达能被AKT信号通路抑制。黑色素瘤中BRAF基因产生了变异,且脯氨酸丰富的肌醇多磷酸5磷酸酶(PIPP)减少,使得PI3K/AKT途径活性增高。PIPP与PTEN有协同抑癌作用,PTEN通过催化磷脂酰肌醇3磷酸(PIP3)转化为PIP2来抑制PI3K/AKT途径。PIPP和PTEN的表达活性呈一定程度的正相关。     

与癫痫有关的细胞信号通路的研究现状

细胞信号通路调控着生物的生长、发育并参与疾病的发生。研究表明,与癫痫有关的信号通路主要有磷脂酰肌醇3-激酶／丝苏氨酸蛋白激酶、哺乳动物雷帕霉素靶蛋白、Wnt等,它们通过调控蛋白质的合成代谢、细胞的增殖和凋亡影响癫痫的病理变化。本文就与癫痫的细胞信号通路的研究进展作一综述。     

糖基化磷脂酰肌醇特异性磷脂酶D基因表达与临床相关疾病

羧基端结合有糖基化磷脂酰肌醇 (GPI)结构的膜蛋白称为GPI锚定蛋白 ,具有广泛功能。糖基化磷脂酰肌醇特异性磷脂酶D(GPI PLD)是人体内唯一能特异性水解GPI并能释放出锚定蛋白的磷脂酶 ,可调节锚定蛋白的表达和生理功能。GPI PLD可能成为评估预后的标记物。在某些肝脏疾病、恶性肿瘤、糖尿病等疾病中有GPI PLD基因异常表达     

PTEN/PI3K信号通路在大鼠心肌肥厚中的表达

目的:观察PTEN/PI3K信号通路在大鼠心肌组织中的表达,探讨该通路在心肌肥厚发生、发展中的作用.方法:皮下注射异丙肾上腺素(ISO)建立大鼠心肌肥厚模型,测定大鼠体质量、心质量、心肌细胞横径和横截面积;采用免疫组织化学方法检测大鼠心肌组织中肥大标志因子β-肌球蛋白(β-MHC)及PTEN/PI3K信号通路上PTEN、磷脂酰肌醇3激酶(PI3K)、蛋白激酶B(PKB)、死亡相关因子(BAD)蛋白表达;利用计算机图像处理系统对各种蛋白进行定量分析.结果:模型组大鼠全心质量/体质量、左室质量/体质量、心肌细胞横径、心肌细胞截面积较对照组明显增加.模型组大鼠的心肌组织与对照组相比,β-MHC、PI3K与PKB表达水平均升高,PTEN和BAD表达水平明显降低.结论:PTEN在心肌肥厚中表达明显降低,起负性调节作用;PI3K/PKB信号通路激活,可能是导致心肌肥厚的机制之一,BAD可望成为生物学治疗靶点.     

磷脂酰肌醇3激酶/蛋白激酶B/雷帕霉素靶蛋白信号通路在肺部疾病中的研究进展

磷脂酰肌醇3激酶/蛋白激酶B/雷帕霉素靶蛋白(phosphatidylinositol-3-kinase/protein kinase B/mammalian target of rapamycin,PI3K/Akt/mTOR)是细胞内重要信号通路,在细胞生长、增殖、分化和蛋白合成等过程中起重要作用.肺癌、哮喘、肺动脉高压、肺纤维化、慢性阻塞性肺疾病(chronic pulmonary obstructive disease,CORD)等疾病是呼吸系统常见疾病,其病理机制涉及细胞增殖及凋亡等,与PI3K/Akt/mTOR信号通路关系密切.     

磷脂酰肌醇-3激酶/蛋白激酶B信号系统

质膜成分磷脂酰肌醇被其3位激酶(PI3K)活化后,可以使蛋白激酶B(PKB)由细胞浆定位于胞膜,继而被磷酸化激活。PKB是原癌基因akt的产物,具有丝/苏氨酸蛋白激酶活性,介导细胞代谢、生长、增殖等效应。PI3K/PKB系统是近年来发现的一个生长因子信号转导通路。     

PTEN as a Unique Promising Therapeutic Target for Occupational Asthma

The tumor suppressor phosphatase and tensin homologue deleted on chromosome ten (PTEN) dephophorylates phosphatidylinositol 3,4,5-triphosphate (PIP3) and is a key negative regulator of phosphoinositide kinase-3 (PI3K) signaling pathway. PTEN also suppresses cellular motility through mechanisms that may be partially independent of phosphatase activity. PTEN is one of the most commonly lost tumor suppressors in human cancers, and its down-regulation is also implicated in several other diseases including airway inflammatory diseases. There is increasing evidence regarding the protective effects of PTEN on the bronchial asthma which is induced by complex signaling networks. Very recently, as for the occupational asthma (OA) with considerable controversy for its pathobiologic mechanisms, PTEN has been considered as a key molecule which is capable of protecting toluene diisocyanate (TDI)-induced asthma, suggesting that PTEN is located at switching point of various molecular signals in OA. Knowledge of the mechanisms of PTEN regulation/function could direct to the pharmacological manipulation of PTEN. This article reviews the latest knowledge and studies on the roles and mechanisms of PTEN in OA.     

PTEN as a unique promising therapeutic target for occupational asthma

The tumor suppressor phosphatase and tensin homologue deleted on chromosome ten (PTEN) dephophorylates phosphatidylinositol 3,4,5-triphosphate (PIP3) and is a key negative regulator of phosphoinositide kinase-3 (PI3K) signaling pathway. PTEN also suppresses cellular motility through mechanisms that may be partially independent of phosphatase activity. PTEN is one of the most commonly lost tumor suppressors in human cancers, and its down-regulation is also implicated in several other diseases including airway inflammatory diseases. There is increasing evidence regarding the protective effects of PTEN on the bronchial asthma which is induced by complex signaling networks. Very recently, as for the occupational asthma (OA) with considerable controversy for its pathobiologic mechanisms, PTEN has been considered as a key molecule which is capable of protecting toluene diisocyanate (TDI)-induced asthma, suggesting that PTEN is located at switching point of various molecular signals in OA. Knowledge of the mechanisms of PTEN regulation/function could direct to the pharmacological manipulation of PTEN. This article reviews the latest knowledge and studies on the roles and mechanisms of PTEN in OA.     

PTEN regulates phospholipase D and phospholipase C

PTEN is an ubiquitously expressed tumor suppressor which plays a prominent role in the pathogenesis of many types of sporadic solid tumors, including breast cancer, as well as hematologic malignancies. Germline PTEN mutations cause 85% of Cowden syndrome (CS), characterized by a high risk of breast and thyroid cancers, and 65% of Bannayan-Riley-Ruvalcaba syndrome (BRRS), characterized by lipomatosis, hemangiomas and speckled penis. Historically, PTEN's role in tumor suppression has been linked to the down-regulation of the PI3K/AKT pathway by PTEN's lipid phosphatase activity. Beyond the AKT pathway, however, there has been minimal examination of PTEN's responsibility in lipid-derived cellular signaling. As phospholipids have been shown to be critical components in signal transduction and cellular proliferation and PTEN controls cellular phospholipid levels, we hypothesized that PTEN functions as a regulator of lipid signaling and homeostasis. Increased PTEN expression in unstimulated MCF-7 breast cancer cells results in a 51% increase in phosphatidic acid, with a decrease in phosphatidylcholine, suggesting that PTEN may regulate phospholipase D (PLD). PTEN overexpression results in a 30% increase in basal PLD activity. As phospholipase C (PLC) is both involved in PLD activation and is regulated by PIP2/3 levels, we investigated the role of PTEN on PLC activation. Our data suggest that PTEN modulates PLC:PLD activation pathways and indicate that the pathogenesis of CS/BRRS has a more complex biochemical basis beyond simply activating the PI3K pathway. This provides alternative routes for PTEN's tumor suppressor action that may be beneficial in the creation of novel targets for cancer therapy and prevention.     

The genome and epigenome of malignant melanoma

Malignant melanoma originates in melanocytes, the pigment-producing cells of the skin and eye, and is one of the most deadly human cancers with no effective cure for metastatic disease. Like many other cancers, melanoma has both environmental and genetic components. For more than 20 years, the melanoma genome has been subject to extensive scrutiny, which has led to the identification of several genes that contribute to melanoma genesis and progression. Three molecular pathways have been found to be nearly invariably dysregulated in melanocytic tumors, including the RAS-RAF-MEK-ERK pathway (through mutation of BRAF, NRAS or KIT), the p16 INK4A-CDK4-RB pathway (through mutation of INK4A or CDK4) and the ARF-p53 pathway (through mutation of ARF or TP53). Less frequently targeted pathways include the PI3K-AKT pathway (through mutation of NRAS, PTEN or PIK3CA) and the canonical Wnt signaling pathway (through mutation of CTNNB1 or APC). Beyond the specific and well-characterized genetic events leading to activation of proto-oncogenes or inactivation of tumor suppressor genes in these pathways, systematic high-resolution genomic analysis of melanoma specimens has revealed recurrent DNA copy number aberrations as well as perturbations of DNA methylation patterns. Melanoma provides one of the best examples of how genomic analysis can lead to a better understanding of tumor biology. We review current knowledge of the genes involved in the development of melanoma and the molecular pathways in which these genes operate.     

Striking the balance between PTEN and PDK1: it all depends on the cell context

The phosphatidyl-inosital-3 kinase (PI3K) signaling pathway is critical for normal brain development and function and is commonly hyperactivated in brain cancer. The PTEN (phosphatase and tensin homolog deleted on chromosome 10) tumor suppressor protein and phosphate-depended kinase 1 (PDK-1) are critical regulators of this pathway. In the July 15, 2009, issue of Genes & Development, Chalhoub and colleagues (pp. 1619–1624) demonstrate PDK1-dependent and PDK1-independent effects of conditional PTEN deletion in the brain, and they identify cell type-specific differences in feedback regulation of the PI3K pathway. These studies provide important insights as to how neurons and glia may differentially regulate PI3K signaling, yielding intriguing clues about targeting PTEN-deficient brain cancers.     

Promoter methylation and silencing of PTEN in gastric carcinoma

The PTEN/MMAC1/TEP1 gene (phosphatase and tensin homolog deleted on chromosome 10/mutated in multiple advanced cancers/TGF-beta regulated and epithelial cell enriched phosphatase 1), which regulates the signaling pathways of Akt, is a novel tumor suppressor gene implicated in multiple cancers. Because a number of tumor suppressor genes are known to be silenced by aberrant promoter methylation, we examined the methylation status of the 5' CpG islands of PTEN using methylation-specific PCR. The altered expression of PTEN in 310 gastric carcinomas was analyzed by immunohistochemical staining using tissue-array and clinicopathologic profiles related to PTEN expression were characterized. Of 310 consecutive gastric carcinomas, 62 cases (20%) showed expression loss of PTEN. Altered PTEN expression was significantly associated with tumor depth and size, lymphatic invasion, advanced stage, pTNM stage, and patient survival (p < 0.001). The promoter methylation frequency of PTEN was found to be present in 26 (39%) of 66 cases examined, and 19 (73%) of 26 gastric cancer tissues showing promoter methylation exhibited the loss of PTEN expression. Abnormalities in the expression of PTEN significantly correlated with promoter methylation (p < 0.001). In conclusion, silencing of the PTEN gene occurs frequently in gastric carcinoma and aberrant promoter methylation is a major mechanism of silencing of the PTEN gene. The abnormalities of the PTEN gene are associated with tumor progression, metastasis, and survival.