关键词： IQGAP1   Endothelial Adherens Junction   VE-cadherin   N-cadherin  

摘要： Adhesion molecules are known to play an important role in endothelial activation and angiogenesis. Here we determined the functional role of IQGAP1 in the regulation of endothelial adherens junctions. VE-cadherin is found to be associated with actin filaments and thus stable, but IQGAP1 at intercellular junctions is not bound to actin filaments and thus labile. Expression of GFP labeled VE-alpha-catenin is shown to increase the electrical resistance across HUVEC monolayers and diminishes endogenous labile IQGAP1 at the intercellular junctions. Knockdown of endogenous IQGAP1 enhances intercellular adhesion in HUVECs by increasing the association of VE-cadherin with P120 and beta-catenin. IQGAP1 knockdown also decreases the interaction of N-cadherin with P120 and beta-catenin. Together, these results suggest that a labile pool of IQGAP1 at intercellular junctions disassembles adherens junctions and thus impairs endothelial cell-cell adhesion.

关键词： glomerular   Angiotensin   activating   GTPase   saline   caspase   mesangial   infusion   assigned   capillary  

摘要： Objective To evaluate the effects of AngⅡon the expression of IQ domain GTPase-activating protein1(IQ-GAP1) and apoptosis of glomerular cells,and to explorethe role of IQGAP1in AngⅡ-induced apoptosis

关键词： SASH1   Mutation   Melanocyte migration   G alpha s   IQGAP1  

摘要： One important function of melanocytes (MCs) is to produce and transfer melanin to neighbouring keratinocytes (KCs) to protect epithelial cells from UV radiation. The mechanisms regulating the specific migration and localisation of the MC lineage remain unknown. We have found three heterozygous mutations that cause amino add substitutions in the SASH1 gene in individuals with a kind of dyschromatosis. In epidermal tissues from an affected individual, we observed the increased transepithelial migration of melanocytes. Functional analyses indicate that these SASH1 mutations not only cause the increased migration of A375 cells and but also induce intensive bindings with two novel cell adhesion partners IQGAP1 and G alpha s. Further, SASH1 mutations induce uniform loss of E-Cadherin in human A375 cells. Our findings suggest a new scaffold protein SASH1 to regulate IQGAP1-E-Cadherin signalling and demonstrate a novel crosstalking between GPCR signalling, calmodulin signalling for the modulation of MCs invasion. (C) 2013 Elsevier Inc. All rights reserved.

关键词： Squamous cell carcinoma  

摘要： Upregulation of the ERK1 and ERK2 (ERK1/2) MAP kinase (MAPK) cascade occurs in >30% of cancers(1), often through mutational activation of receptor tyrosine kinases or other upstream genes, including KRAS and BRAF(2). Efforts to target endogenous MAPKs are challenged by the fact that these kinases are required for viability in mammals(3) (,4). Additionally, the effectiveness of new inhibitors of mutant BRAF has been diminished by acquired tumor resistance through selection for BRAF-independent mechanisms of ERK1/2 induction(2,5,6). Furthermore, recently identified ERK1/2-inducing mutations in MEK1 and MEK2 (MEK1/2) MAPK genes in melanoma confer resistance to emerging therapeutic MEK inhibitors, underscoring the challenges facing direct kinase inhibition in cancer(7,8). MAPK scaffolds, such as IQ motif-containing GTPase activating protein 1 (IQGAP1)(9,10), assemble pathway kinases to affect signal transmission(11-13), and disrupting scaffold function therefore offers an orthogonal approach to MAPK cascade inhibition. Consistent with this, we found a requirement for IQGAP1 in RAS-driven tumorigenesis in mouse and human tissue. In addition, the ERK1/2-binding(14) IQGAP1 WW domain peptide disrupted IQGAP1-ERK1/2 interactions, inhibited RAS- and RAF-driven tumorigenesis, bypassed acquired resistance to the BRAF inhibitor vemurafenib (PLX-4032) and acted as a systemically deliverable therapeutic to significantly increase the lifespan of tumor-bearing mice. Scaffold-kinase interaction blockade acts by a mechanism distinct from direct kinase inhibition and may be a strategy to target overactive oncogenic kinase cascades in cancer.

摘要： Cell culture and mouse studies identified a peptide-based inhibitor of IQGAP1 that could help treat cancer.

关键词： Animal models   Beta-catenin signaling   Biochemistry   Biology   Developmental biology   Developmental signaling   Embryology   Mechanisms of signal transduction   Model organisms   Molecular cell biology   Molecular development   Protein interactions   Proteins   Research Article   Signal transduction   Signaling   Signaling cascades   Signaling in cellular processes   Signaling in selected disciplines   Signaling pathways   Xenopus laevis  

摘要： Dishevelled (DVL) is a central factor in the Wnt signaling pathway, which is highly conserved among various organisms. DVL plays important roles in transcriptional activation in the nucleus, but the molecular mechanisms underlying their nuclear localization remain unclear. In the present study, we identified IQGAP1 as a regulator of DVL function. In Xenopus embryos, depletion of IQGAP1 reduced Wnt-induced nuclear accumulation of DVL, and expression of Wnt target genes during early embryogenesis. The domains in DVL and IQGAP1 that mediated their interaction are also required for their nuclear localization. Endogenous expression of Wnt target genes was reduced by depletion of IQGAP1 during early embryogenesis, but notably not by depletion of other IQGAP family genes. Moreover, expression of Wnt target genes caused by depletion of endogenous IQGAP1 could be rescued by expression of wild-type IQGAP1, but not IQGAP1 deleting DVL binding region. These results provide the first evidence that IQGAP1 functions as a modulator in the canonical Wnt signaling pathway.

关键词： 乳腺肿瘤   支架蛋白   IQGAP1   Transwell   Westenblot  

摘要： 目的:通过免疫组化方法探讨支架蛋白IQGAP1在乳腺癌中的表达及意义。方法:(1)选取乳腺癌、癌旁组织及良性病变组织的存档蜡块,制成组织芯片;(2)通过免疫组织化学EnVision二步法检测IQGAP1蛋白的表达情况,运用SPSS 13.0进行统计学分析。结果:(1)82例导管癌组织标本中69例为阳性表达,81例癌旁组织标本中63例为阳性表达,两者差异无统计学意义(P>0.05);28例良性病变中9例为胞浆阳性表达,与癌组织比较差异有显著统计学意义(P<0.001)。(2)导管癌82例阳性表达标本中组织学分级为3级者膜阳性表达为12例(12/14),差异有统计学意义(P<0.05),2级为29例(29/47),差异无统计学意义(P>0.05),1级为0例(0/8),差异有显著统计学意义(P<0.001)。(3)肿瘤组织呈条索样生长的标本阳性表达有27例,其中膜表达23例;非条索样生长的标本阳性表达42例,膜表达18例,两者差异有显著统计学意义(P<0.001)。结论:(1)IQGAP1蛋白表达部位与肿瘤分化程度有关,并可能参与肿瘤局部浸润的微环境变化;(2)IQGAP1蛋白与肿瘤细胞的迁徙运动密切相关。

关键词： MYOFIBROBLASTS   METASTASIS   UBIQUITIN   CELLULAR signal transduction   CELL membranes   PERICYTES  

摘要： In the tumor microenvironment, TGF-beta induces transdifferentiation of quiescent pericytes and related stromal cells into myofibroblasts that promote tumor growth and metastasis. The mechanisms governing myofibroblastic activation remain poorly understood, and its role in the tumor microenvironment has not been explored. Here, we demonstrate that IQ motif containing GTPase activating protein 1 (IQGAP1) binds to TGF-beta receptor II (T beta RII) and suppresses T beta RII-mediated signaling in pericytes to prevent myofibroblastic differentiation in the tumor microenvironment. We found that TGF-beta 1 recruited IQGAP1 to T beta RII in hepatic stellate cells (HSCs), the resident liver pericytes. Iqgap1 knockdown inhibited the targeting of the E3 ubiquitin ligase SMAD ubiquitination regulatory factor 1 (SMURF1) to the plasma membrane and T beta RII ubiquitination and degradation. Thus, Iqgap1 knockdown stabilized T beta RII and potentiated TGF-beta 1 transdifferentiation of pericytes into myofibroblasts in vitro. Iqgap1 deficiency in HSCs promoted myofibroblast activation, tumor implantation, and metastatic growth in mice via upregulation of paracrine signaling molecules. Additionally, we found that IQGAP1 expression was downregulated in myofibroblasts associated with human colorectal liver metastases. Taken together, our studies demonstrate that IQGAP1 in the tumor microenvironment suppresses T beta RII and TGF-beta dependent myofibroblastic differentiation to constrain tumor growth.

关键词： Anatomy and physiology   Biochemistry   Biology   Cell differentiation   Cellular neuroscience   Developmental biology   Developmental neuroscience   Immunochemistry   Medicine   Molecular cell biology   Morphogenesis   Neurochemistry   Neurological system   Neuroscience   Physiology   Research Article   Synaptic plasticity  

摘要： IQGAP1 is a scaffolding protein that regulates spine number. We now show a differential role for IQGAP1 domains in spine morphogenesis, in which a region of the N-terminus that promotes Arp2/3-mediated actin polymerization and branching stimulates spine head formation while a region that binds to Cdc42 and Rac is required for stalk extension. Conversely, IQGAP1 rescues spine deficiency induced by expression of dominant negative Cdc42 by stimulating formation of stubby spines. Together, our observations place IQGAP1 as a crucial regulator of spine number and shape acting through the N-Wasp Arp2/3 complex, as well as upstream and downstream of Cdc42.

关键词： Breast cancer   Cancer cell migration   Invasive tumors   Guanosine triphosphatase   Breast tumors   Co-immunoprecipitation   Immunostaining   Cell motility  

摘要： beta-arrestins play critical roles in chemotaxis and cytoskeletal reorganization downstream of several receptor types, including G protein-coupled receptors (GPCRs), which are targets for greater than 50% of all pharmaceuticals. Among them, receptors for lysophosphatidic acid (LPA), namely LPA(1) are overexpressed in breast cancer and promote metastatic spread. We have recently reported that beta-arrestin2 regulates LPA(1)-mediated breast cancer cell migration and invasion, although the underlying molecular mechanisms are not clearly understood. We show here that LPA induces activity of the small G protein, Rap1 in breast cancer cells in a beta-arrestin2-dependent manner, but fails to activate Rap1 in non-malignant mammary epithelial cells. We found that Rap1A mRNA levels are higher in human breast tumors compared to healthy patient samples and Rap1A is robustly expressed in human ductal carcinoma in situ and invasive tumors, in contrast to the normal mammary ducts. Rap1A protein expression is also higher in aggressive breast cancer cells (MDA-MB-231 and Hs578t) relative to the weakly invasive MCF-7 cells or non-malignant MCF10A mammary cells. Depletion of Rap1A expression significantly impaired LPA-stimulated migration of breast cancer cells and invasiveness in three-dimensional Matrigel cultures. Furthermore, we found that beta-arrestin2 associates with the actin binding protein IQGAP1 in breast cancer cells, and is necessary for the recruitment of IQGAP1 to the leading edge of migratory cells. Depletion of IQGAP1 blocked LPA-stimulated breast cancer cell invasion. Finally, we have identified that LPA enhances the binding of endogenous Rap1A to beta-arrestin2, and also stimulates Rap1A and IQGAP1 to associate with LPA1. Thus our data establish novel roles for Rap1A and IQGAP1 as critical regulators of LPA-induced breast cancer cell migration and invasion.