关键词： S1P   cortical actin   proteomics  

摘要： Bhattacharya M, Su G, Su X, Oses-Prieto JA, Li JT, Huang X, Hernandez H, Atakilit A, Burlingame AL, Matthay MA, Sheppard D. IQGAP1 is necessary for pulmonary vascular barrier protection in murine acute lung injury and pneumonia. Am J Physiol Lung Cell Mol Physiol 303: L12-L19, 2012. First published May 4, 2012;doi:10.1152/ajplung.00375.2011.-We recently reported that integrin alpha v beta(3) is necessary for vascular barrier protection in mouse models of acute lung injury and peritonitis. Here, we used mass spectrometric sequencing of integrin complexes to isolate the novel beta(3)-integrin binding partner IQGAP1. Like integrin beta(3), IQGAP1 localized to the endothelial cell-cell junction after sphingosine-1-phosphate (S1P) treatment, and IQGAP1 knockdown prevented cortical actin formation and barrier enhancement in response to S1P. Furthermore, knockdown of IQGAP1 prevented localization of integrin alpha v beta(3) to the cell-cell junction. Similar to beta(3)-null animals, IQGAP1-null mice had increased pulmonary vascular leak compared with wild-type controls 3 days after intratracheal LPS. In an Escherichia coli pneumonia model, IQGAP1 knockout mice had increased lung weights, lung water, and lung extravascular plasma equivalents of I-125-labeled albumin compared with wild-type controls. Taken together, these experiments indicate that IQGAP1 is necessary for S1P-mediated vascular barrier protection during acute lung injury and is required for junctional localization of the barrier-protective integrin alpha v beta(3).

关键词： CYTOSKELETAL proteins   ADAPTOR proteins   TOLL-like receptors   ACTIN   DYNAMICS   GUANOSINE triphosphatase   FIBROBLASTS   EPITHELIAL cells  

摘要： The Ras GTPase-activating-like protein IQGAP1 is a multimodular scaffold that controls signaling and cytoskeletal regulation in fibroblasts and epithelial cells. However, the functional role of IQGAP1 in T cell development, activation, and cytoskeletal regulation has not been investigated. In this study, we show that IQGAP1 is dispensable for thymocyte development as well as microtubule organizing center polarization and cytolytic function in CD8(+) T cells. However, IQGAP1-deficient CD8(+) T cells as well as Jurkat T cells suppressed for IQGAP1 were hyperresponsive, displaying increased IL-2 and IFN-gamma production, heightened LCK activation, and augmented global phosphorylation kinetics after TCR ligation. In addition, IQGAP1-deficient T cells exhibited increased TCR-mediated F-actin assembly and amplified F-actin velocities during spreading. Moreover, we found that discrete regions of IQGAP1 regulated cellular activation and F-actin accumulation. Taken together, our data suggest that IQGAP1 acts as a dual negative regulator in T cells, limiting both TCR-mediated activation kinetics and F-actin dynamics via distinct mechanisms. The Journal of Immunology, 2012, 188: 6135-6144.

关键词： Actinin/metabolism   Adaptor Proteins, Signal Transducing/metabolism   beta Catenin/metabolism   Cell Adhesion Molecules, Neuronal/metabolism   Cell Line   Cell Movement/physiology   Cytoskeletal Proteins/metabolism   Humans   Intracellular Signaling Peptides and Proteins/metabolism   Kidney Glomerulus/cytology   Kidney Glomerulus/metabolism   Membrane Proteins/metabolism   Oncogene Proteins/metabolism   Permeability   Podocytes/metabolism   Podocytes/metabolism   Protein Binding   Protein Transport   ras GTPase-Activating Proteins/metabolism   Sialoglycoproteins/metabolism  

摘要： IQGAP1 is a scaffold protein that interacts with proteins of the cytoskeleton and the intercellular adhesion complex. In podocytes, IQGAP1 is associated with nephrin in the glomerular slit diaphragm (SD) complex, but its role remains ill-defined. In this work, we investigated the interaction of IQGAP1 with the cytoskeleton and SD proteins in podocytes in culture, and its role in podocyte migration and permeability. Expression, localization, and interactions between IQGAP1 and SD or cytoskeletal proteins were determined in cultured human podocytes by Western blot (WB), immunocytolocalization (IC), immunoprecipitation (IP), and In situ Proximity Ligation assay (IsPL). Involvement of IQGAP1 in migration and permeability was also assessed. IQGAP1 expression in normal kidney biopsies was studied by immunohistochemistry. IQGAP1 expression by podocytes increased during their in vitro differentiation. IC, IP, and IsPL experiments showed colocalizations and/or interactions between IQGAP1 and SD proteins (nephrin, MAGI-1, CD2AP, NCK 1/2, podocin), podocalyxin, and cytoskeletal proteins (alpha-actinin-4). IQGAP1 silencing decreased podocyte migration and increased the permeability of a podocyte layer. Immunohistochemistry on normal human kidney confirmed IQGAP1 expression in podocytes and distal tubular epithelial cells and also showed an expression in glomerular parietal epithelial cells. In summary, our results suggest that IQGAP1, through its interaction with components of SD and cytoskeletal proteins, is involved in podocyte barrier properties.

关键词： IQGAP1   Aurora-A   Protein degradation   Tumorigenesis  

摘要： IQGAP1, a ubiquitously expressed scaffold protein, has been identified in a wide range of organisms. It participates in multiple aspects of cellular events by binding to and regulating numerous interacting proteins. In our present study, we identified a new IQGAP1 binding protein named Aurora-A which is an oncogenic protein and overexpressed in various types of human tumors. In vitro analysis with GST-Aurora-A fusion proteins showed a physical interaction between Aurora-A and IQGAP1. Moreover, the binding also occurred in HeLa cells as endogenous Aurora-A co-immunoprecipitated with IQGAP1 from the cell lysates. Overexpression of IQGAP1 resulted in an elevation of both expression and activity of Aurora-A kinase. Endogenous IQGAP1 knockdown by siRNA promoted Aurora-A degradation whereas IQGAP1 overexpression enhanced the stability of Aurora-A. Additionally, we documented that the IQGAP1-induced cell proliferation was suppressed by knocking down Aurora-A expression. Taken together, our results showed an unidentified relationship between Aurora-A and IQGAP1, and provided a new insight into the molecular mechanism by which IQGAP1 played a regulatory role in cancer. (C) 2012 Elsevier Inc. All rights reserved.

关键词： IQGAP1   Proliferation   Secretion   mTOR  

摘要： Defining the mechanisms that control cell growth and division is crucial to understanding cell homeostasis, which impacts human diseases such as cancer and diabetes. IQGAP1, a widely conserved effector and/or regulator of the GTPase CDC42, is a putative oncoprotein that controls cell proliferation;however, its mechanism in tumorigenesis is unknown. The mechanistic target of rapamycin (mTOR) pathway, the center of cell growth control, is commonly activated in human cancers, but has proved to be an ineffective clinical target because of an incomplete understanding of its mechanisms in cell growth inhibition. Using complementary studies in yeast and mammalian cells, we examined a potential role for IQGAP1 in regulating the negative feedback loop (NFL) of mTOR complex 1 (mTORC1) that controls cell growth. Two-hybrid screens identified the yeast TORC1-specific subunit Tco89p as an Iqg1p-binding partner, sharing roles in rapamycin-sensitive growth, axial-bud-site selection and cytokinesis, thus coupling cell growth and division. Mammalian IQGAP1 binds mTORC1 and Akt1 and in response to epidermal growth factor (EGF), cells expressing the mTORC1-Akt1-binding region (IQGAP1(IR-WW)) contained attenuated phosphorylated ERK1/2 (ERK1/2-P) activity and inactive glycogen synthase kinase 3 alpha/beta (GSK3 alpha/beta), which control apoptosis. Interestingly, these cells displayed a high level of Akt1 S473-P, but an attenuated level of the mTORC1-dependent kinase S6K1 T389-P and induced mTORC1-Akt1- and EGF-dependent transformed phenotypes. Moreover, IQGAP1 appears to influence cell abscission and its activity is elevated in carcinoma cell lines. These findings support the hypothesis that IQGAP1 acts upstream on the mTORC1-S6K1 -> Akt1 NFL and downstream of it, to couple cell growth and division, and thus like a rheostat, regulates cell homeostasis, dysregulation of which leads to tumorigenesis or other diseases. These results could have implications for the development of the next

关键词： Diacylglycerol kinase   IQGAP   Rac1   Macrophage   Phagocytosis  

摘要： Diacylglycerol kinase (DGK) plays an important role in phosphoinositide signaling cascade by regulating the intracellular level of diacylglycerol and phosphatidic acid. The DGK family is involved in various pathophysiological responses that are mediated through unique binding partners in different tissues and cells. In this study, we identified a small GTPase effector protein, IQGAP1, as a novel DGK zeta-associated complex protein. A bacterial endotoxin, lipopolysaccharide (LPS), facilitated the complex formation in macrophages. Both proteins co-localized at the edge and phagocytic cup of the cell. Furthermore, RNA interference-mediated knockdown of DGK zeta or IQGAP1 impaired LPS-induced Rac1 activation. Primary macrophages derived from DGK zeta(-/-) mice attenuated LPS-induced phagocytosis of bacteria. These results suggest that DGK zeta is involved in IQGAP1/Rac1-mediated phagocytosis upon LPS stimulation in macrophages. (C) 2012 Elsevier Inc. All rights reserved.

关键词： 哈萨克族   食管肿瘤   IQGAP1  

摘要： 目的:检测IQ结构域三磷酸鸟苷合酶-激活蛋白1(IQ domain GTPase-activating protein 1,IQGAP1)在哈萨克族食管癌组织中的表达,分析其与临床病理参数的相关性。方法:采用逆转录PCR(reverse transcription polymerase chain reaction,RTPCR)检测48例哈萨克族食管癌切除标本中癌组织与远端无癌组织中IQGAP1 mRNA表达水平,并分析其与临床病理指标的关系。结果:癌组织中IQGAP1 mRNA表达阳性率(50%)高于其远端无癌组织(21%),其差异具有统计学意义(P<0.05);但IQGAP1 mRNA的表达与癌组织分化程度、病理分期及有无淋巴结转移均无相关性(P>0.05)。结论:IQGAP1基因的表达可能与哈萨克族食管癌的发生有关。

关键词： IQ模体的Ras   GTP酶活化蛋白1   舌   癌,鳞状细胞   临床病理特征   预后  

摘要： 目的探讨IQ模体的RasGTP酶活化蛋白1(IQGAP1)在舌鳞状细胞癌(以下简称舌鳞癌)中的表达与临床意义及其对影响舌鳞癌患者预后的影响。方法采用免疫组织化学方法对比检测IQGAP1在舌鳞癌组织和癌旁组织中的差异表达,并分析IQGAP1表达模式与临床病理参数的相关性。同时,回顾性分析中山大学附属口腔医院2006年1月至2010年12月收治的舌鳞癌患者的临床资料,进行多因素Cox回归模型分析。结果 IQGAP1在舌鳞癌中呈高表达状态,而在癌旁组织中呈低表达或阴性表达,而且高表达水平的IQGAP1与颈淋巴结转移(P=0.019)、复发(P=0.017)以及临床分期(P=0.031)等有关。此外,高表达的IQGAP1与舌鳞癌患者的预后具有密切联系(P=0.017)。结论 IQGAP1在舌鳞癌中的异常表达说明其在舌鳞癌的发生、发展中起重要作用,高表达的IQGAP1有可能成为预测舌鳞癌患者预后的一种有效标记物。

关键词： Cell signalling   IQGAP   IQGAP1   Scaffold protein  

摘要： IQGAP proteins have been identified in a wide spectrum of organisms, ranging from yeast to humans. The most extensively studied family member is the ubiquitously expressed scaffold protein IQGAP1, which participates in multiple essential aspects of mammalian biology. IQGAP1 mediates these effects by binding to and regulating the function of numerous interacting proteins. Over ninety proteins have been reported to associate with IQGAP1, either directly or as part of a larger complex. In this review, we summarise those IQGAP1 binding partners that have been identified in the last five years. The molecular mechanisms by which these interactions contribute to the functions of receptors and their signalling cascades, small GTPase function, cytoskeletal dynamics, neuronal regulation and intracellular trafficking are evaluated. The evidence that has accumulated recently validates the role of IQGAP1 as a scaffold protein and expands the repertoire of cellular activities in which it participates. Published by Elsevier Inc.

关键词： 乳腺导管癌   具有IQ基序的GTP激酶活化蛋白   Transwell迁移实验  

摘要： 目的探讨支架蛋白IQGAPl在乳腺浸润性导管癌中的表达及沉默IQGAPl表达对肿瘤细胞迁移能力的影响。方法利用免疫组织化学染色和Westernblotting技术检测IQGAPl蛋白在乳腺浸润性导管癌组织、癌旁组织以及良性乳腺病变组织中的表达；分析IQGAPI蛋白在乳腺浸润性导管癌组织中的表达与临床病理参数的关系。构建载有shRNA—IQGAPl的慢病毒表达载体，将其稳定转染高转移乳腺癌MDA—MB-435细胞，获得稳定抑制IQGAPl蛋白表达的细胞株（IQGAPl-shRNA组）及相应的空载细胞株（Vector组）、空白对照细胞株（Blank组）；运用基于Transwell系统的体外迁移实验观察沉默IQGAPl的表达对MDA—MB-435细胞迁移能力的影响。结果IQGAPl蛋白在乳腺浸润性导管癌组织中的阳性表达率为83．44％（136／163），与良性乳腺病变组织（32．14％，9／28）比较，差异具有统计学意义（P〈0．01）；IQGAPl蛋白在癌旁组织中的阳性表达率（77．78％，63／81）与乳腺浸润性导管癌组织比较，差异无统计学意义（P〉0．05）。163例乳腺浸润性导管癌中WHO分级为3级者IQGAPl蛋白表达为阴性、胞质阳性和胞膜阳性的例数分别为1、3和22，2级者分别为21、40和61；1级者分别为5、9和l，差异具有统计学意义（P〈0．01）；IQGAPl蛋白的表达与肿瘤的大小有关（P〈0．01），与淋巴结是否转移无关（P〉0．05）。Blank组、Vector组和IQGAPl一shRNA组中穿过Transwell小室的平均细胞数分别为（294．3±16．3）、（287．7±16．9）和（93．5±7．6）个，IQGAPl-shRNA组显著低于其他两组（P〈0．01）。结论IQGAPl蛋白在乳腺浸润性导管癌组织中的表达明显高于良性乳腺病变组织；IQGAPI蛋白表达部位与肿瘤分化程度有关；IQGAPl蛋白在乳腺癌转移过程中起促进作用。