关键词： IQGAP1   同质粘附   基因干扰   食管癌  

摘要： 目的:研究IQGAP1基因干扰对人食管癌细胞同质粘附能力的影响。方法:体外培养人食管癌KYSE150和EC9706细胞,利用Western blot方法检测两株细胞。IQGAP1蛋白的表达,利用缓慢聚集和细胞分离实验比较两株细胞同质粘附能力的差异;进一步在KYSE150和EC9706细胞中构建IQGAP1基因干扰的稳定细胞系,观察IQGAP1基因干扰后细胞同质粘附能力的改变。结果:KYSE150细胞IQGAP1蛋白表达量低于EC9706细胞,而同质粘附能力高于EC9706细胞;IQGAP1基因干扰后,其蛋白表达量明显降低,而细胞同质粘附能力明显增强。结论:IQGAP1基因干扰能够显著增强食管癌细胞的同质粘附能力,从而降低肿瘤细胞的恶性表型。

关键词： DAB density shift   endothelial cell   fractionation   IQGAP1   LBRC   PECAM  

摘要： The migration of leukocytes across the endothelium and into tissue is critical to mounting an inflammatory response. The lateral border recycling compartment (LBRC), a complex vesicular-tubule invagination of the plasma membrane found at endothelial cell borders, plays an important role in this process. Although a few proteins have been shown to be present in the LBRC, no unique marker is known. Here, we detail methods that can be used to characterize a subcellular compartment that lacks an identifying marker. Initial characterization of the LBRC was performed using standard subcellular fractionation with sucrose gradients and took advantage of the observation that the compartment migrated at a lower density than other membrane compartments. To isolate larger quantities of the compartment, we modified a classic technique known as a diaminobenzidine (DAB)-induced density shift. The DAB-induced density shift allowed for specific isolation of membranes labeled with horseradish peroxidase-conjugated antibody. Because the LBRC could be differentially labeled at 4 degrees C and 37 degrees C, we were able to identify proteins that are enriched in the compartment, despite lacking a unique marker. These methods serve as a model to others studying poorly characterized compartments and organelles and are applicable to a wide variety of biological systems.

摘要： Cross talk between the actin cytoskeleton and microtubules (MT) has been implicated in the amplification of agonist-induced Rho signaling, leading to increased vascular endothelial permeability. This study tested the involvement of actin-MT cross talk in the mechanisms of barrier enhancement induced by hepatocyte growth factor (HGF) and evaluated the role of the adaptor protein IQGAP1 in integrating the MT- and actin-dependent pathways of barrier enhancement. IQGAP1 knockdown by small interfering RNA attenuated the HGF-induced increase in endothelial barrier properties and abolished HGF-activated cortical actin dynamics. IQGAP1 reduction abolished HGF-induced peripheral accumulation of Rac cytoskeletal effector cortactin and cortical actin remodeling. In addition, HGF stimulated peripheral MT growth in an IQGAP1-dependent fashion. HGF also induced Rac1-dependent IQGAP1 association with the MT fraction and the formation of a protein complex containing end-binding protein 1 (EB1), IQGAP1, and cortactin. Decreasing endogenous IQGAP1 abolished HGF-induced EB1-cortactin colocalization at the cell periphery. In turn, expression of IQGAP1 Delta C (IQGAP1 lacking the C-terminal domain) attenuated the cortactin association with EB1 and suppressed HGF-induced endothelial cell peripheral actin cytoskeleton enhancement. These results demonstrate for the first time the MT-actin cross talk mechanism of HGF-induced endothelial barrier enhancement and suggest that IQGAP1 functions as a hub linking HGF-induced signaling to MT and actin remodeling via EB1-IQGAP1-cortactin interactions.

关键词： RhoC   IQGAP1   肿瘤  

摘要： 肿瘤的发生和发展是一个长期的、分阶段的、多种基因突变积累的复杂过程，是由多个激活的原癌基因、失活的抑癌基因、变化的有关融合基因，以及一系列信号转导通路参与完成的。其中任何一个因素的改变都可以引起细胞增殖和凋亡失去控制从而导致肿瘤的发生。癌细胞的无限增殖和转移是最重要的肿瘤恶性生物学行为，且血管、淋巴管形成是癌细胞增殖和转移的基础，大多数癌症患者死于肿瘤的复发和转移，导致死亡的原因主要是肿瘤转移直接侵犯器官，副肿瘤综合征，和或治疗引起的并发症，因此明确肿瘤的复发，尤其是转移机制，可以为肿瘤的预防和治疗提供一些新的思考方向和治疗策略。

关键词： PAK6   IQGAP   Cell junctions   Cell motility   HGF  

摘要： p-21 activated 6 (PAK6), first identified as interacting with the androgen receptor (AR), is over-expressed in multiple cancer tissues and has been linked to the progression of prostate cancer, however little is known about PAK6 function in the absence of AR signaling. We report here that PAK6 is specifically required for carcinoma cell-cell dissociation downstream of hepatocyte growth factor (HGF) for both DU145 prostate cancer and HT29 colon cancer cells. Moreover, PAK6 overexpression can drive cells to escape from adhesive colonies in the absence of stimulation. We have localized PAK6 to cell-cell junctions and have detected a direct interaction between the kinase domain of PAK6 and the junctional protein IQGAP1. Co-expression of IQGAP1 and PAK6 increases cell colony escape and leads to elevated PAK6 activation. Further studies have identified a PAK6/E-cadherin/IQGAP1 complex downstream of HGF. Moreover, we find that beta-catenin is also localized with PAK6 in cell-cell junctions and is a novel PAK6 substrate. We propose a unique role for PAK6, independent of AR signaling, where PAK6 drives junction disassembly during HGF-driven cell-cell dissociation via an IQGAP1/E-cadherin complex that leads to the phosphorylation of beta-catenin and the disruption of cell-cell adhesions.

关键词： cytometry   activating   incubation   assessed   exposed   underlying   phospho   cytoplasm   accompanied   cultured  

摘要： Objective To investigate the role of IQ domain GT Pase-activating protein 1(IQGAP1)in angiotensinⅡ(AngⅡ)-induced podocyte apoptosis and the underlying *** Differentiated mouse podocytes were exposed to AngⅡat different concentrations for 6 h or at 10-8mol/L for variable incubation *** apoptosis was assessed by flow ***

关键词： IQGAP1   Extracellular signal-regulated kinase 1/2   Podocyte   Diabetic nephropathy  

摘要： Podocyte injury may contribute to the pathogenesis of diabetic nephropathy (DN), but the underlying mechanism of hyperglycemia induced podocyte damage is not fully understood. The Ras GTPase-activating-like protein IQGAP1 is associated to the slit diaphragm proteins and the actin cytoskeleton in podocyte. Here, we studied IQGAP1 expression alterations in human DN biopsies and extracellular signal-regulated kinase (ERK)-dependent pathways of IQGAP1 expression in podocyte under high glucose (HG) media. In vivo, analysis of renal biopsies from patients with DN revealed a significant reduction in IQGAP1 expression compared to controls. In vitro, IQGAP1 mRNA and protein expression were observed to decline under HG media at 48 h. But phosphorylation of ERK1/2 was activated under HG media at 24 h and 48 h. However, HG-induced downregulation of IQGAP1 protein was attenuated by specific ERK1/2 activation inhibitor PD98059. Taken together, these results highlight the importance of IQGAP1 in DN, and suggest that IQGAP1 expression in podocyte under HG media is modulated by the ERK1/2 pathway, which may lead to the future development of therapies targeting IQGAP1 dysfunction in podocytes in DN.

关键词： IQGAP1   IQGAP2   Calmodulin   Actin   Cell adhesion   Cell retraction  

摘要： IQGAP1 has emerged as a key component in the regulation of cytoskeleton dynamics during cell migration, maintenance of adherens junctions, microbial pathogenesis and intracellular trafficking. IQGAP1 is known to localize to the protruding edge of lamellipodia in a variety of cell types and interact with regulators of actin dynamics. Here, we provide evidence suggesting a novel role of IQGAP1 in cell motility through cell edge retraction. In some of the cell lines examined, IQGAP1 was markedly separated from WAVE localization suggesting IQGAP1 may localize to retracting edges. B16F10 mouse melanoma cells exhibited the most restricted separation in which the appearance of GFP-IQGAP1 correlated with cell edge retraction velocity and the disappearance of mCherry-Arp3. These results demonstrate that in some cell types IQGAP1 may function to promote cell retraction not lamellipodium edge protrusion. In addition, we examined, co-localization of IQGAP1 with adhesion site markers, myosin IIA, calmodulin and IQGAP2. In areas rich in IQGAP1 there was decreased immunofluorescence staining of vinculin, paxillin and phosphorylated-tyrosine indicating adhesion site disassembly. Interestingly, calmodulin, but not myosin IIA or IQGAP2, co-localized with IQGAP1 in areas of cell retraction. Overall these results suggest a new role of IQGAP1, distinct form IQGAP2, in cell migration through up regulation of contractility and downregulation of adhesion sites potentially through calmodulin interaction. (C) 2014 Elsevier Inc. All rights reserved.

关键词： E—cadherin   IQGAP1   卵巢癌   浆液性囊腺瘤   浆液性囊腺癌  

摘要： 目的探讨上皮性钙黏素(E-cadherin)与具有IQ结构域的人Ras GTP激活蛋白相关蛋白1(IQGAP1)在卵巢浆液性肿瘤中的表达及其临床意义。方法分别用免疫组织化学SP法和Western blot法检测20例卵巢浆液性囊腺癌、10例卵巢交界性浆液性囊腺瘤、10例卵巢浆液性囊腺瘤以及10例正常卵巢组织中E-cadherin和IQGAP1的蛋白表达。结果 E-cadherin蛋白在浆液性囊腺瘤中表达最高,明显高于正常卵巢组织和浆液性囊腺癌组织(P<0.05),其均值高于交界性囊腺癌,无统计学意义。IQGAP1在卵巢浆液性囊腺癌中表达较正常卵巢组织、良性及交界性肿瘤组织均增高(P<0.05);免疫组织化学染色证实IQGAP1在浆液性囊腺癌中以胞膜表达为主,而在良性肿瘤中以胞质表达为主。结论 E-cadherin和IQGAP1在卵巢浆液性瘤高表达,可联合用于卵巢浆液性肿瘤的免疫组化诊断。

关键词： cell signaling   receptor activation   adhesion   migration  

摘要： R-spondins (RSPOs) and their receptor leucine-rich repeat-containing G-protein coupled receptor 4 (LGR4) play pleiotropic roles in normal and cancer development as well as the survival of adult stem cells through potentiation of Wnt signaling. Current evidence indicates that RSPO-LGR4 functions to elevate levels of Wnt receptors through direct inhibition of two membrane-bound E3 ligases (RNF43 and ZNRF3), which otherwise ubiquitinate Wnt receptors for degradation. Whether RSPO-LGR4 is coupled to intracellular signaling proteins to regulate Wnt pathways remains unknown. We identified the intracellular scaffold protein IQ motif containing GTPase-activating protein 1 (IQGAP1) as an LGR4-interacting protein that mediates RSPO-LGR4's interaction with the Wnt signalosome. IQGAP1 binds to and modulates the activities of a plethora of signaling molecules, including MAP kinases, Rho GTPases, and components of the Wnt signaling pathways. Interaction of LGR4 with IQGAP1 brings RSPO-LGR4 to the Wnt signaling complex through enhanced IQGAP1-DVL interaction following RSPO stimulation. In this configuration, RSPO-LGR4-IQGAP1 potentiates beta-catenin-dependent signaling by promoting MEK1/2-medidated phosphorylation of LRP5/6 as well as beta-catenin-independent signaling through regulation of actin dynamics. Overall, these findings reveal that RSPO-LGR4 not only induces the clearance of RNF43/ZNRF3 to increase Wnt receptor levels but also recruits IQGAP1 into the Wnt signaling complex, leading to potent and robust potentiation of both the canonical and noncanonical pathways of Wnt signaling.