关键词： 乳腺肿瘤   基底细胞样型   细胞分裂周期蛋白42(Cdc42)   支架蛋白1(IQGAP1)  

摘要： [目的]分析细胞分裂周期蛋白42(Cdc42)和支架蛋白1(IQGAP1)与基底细胞样型乳腺癌(basal-like breast cancer,BLBC)临床病理特征之间的关系及二者之间的相关性,探讨Cdc42和IQGAP1在BLBC发生、发展及侵袭转移中的作用。[方法 ]采用免疫组化方法检测60例BLBC、45例非基底细胞样型乳腺癌(non-basal-like breast carcinoma,Non-BLBC)和35例癌旁正常乳腺组织中Cdc42和IQGAP1的表达。[结果]Cdc42在BLBC中的表达明显高于Non-BLBC和癌旁正常乳腺组织(P<0.0125),IQGAP1在BLBC和Non-BLBC中的表达明显高于癌旁正常乳腺组织(P<0.0125);BLBC中Cdc42的表达与淋巴结转移和TNM分期密切相关(P<0.05),IQGAP1的表达与肿瘤大小和淋巴结转移密切相关(P<0.05),并且两者在BLBC中的表达呈正相关关系(r=0.638,P<0.05)。[结论]Cdc42和IQGAP1可能是促进肿瘤的局部侵袭和远处转移的重要因素,在BLBC的发生发展中起着重要的作用。

关键词： IQGAP1   Ovarian cancer   Cancer stem cell-like cells   Differentiation   Invasion  

摘要： Background Wide metastasis is one of characteristics of ovarian cancer. Cancer stem cells, as a source in cancer invasion and metastasis, possess powerful potential of differentiation. Scaffolding IQ domain GTPase-activating protein 1 (IQGAP1) plays a key role in the invasion and metastasis of cancer cells, but IQGAP1's role in cancer stem cells including ovarian cancer was unclear. Methods Spheroid culture with serum-free medium was used for enriching ovarian cancer stem cell-like cells (CSC-LCs) from 3AO cell line, and a medium with 10% fetal bovine serum was used to induce the differentiation of CSC-LCs. Immunofluorescence was for detecting the stem markers OCT4 and SOX2. The quantitative real-time-polymerase chain reaction and Western blotting were performed to determine the messenger RNA and protein expression of IQGAP1, respectively. The capacity of cell invasion was evaluated by transwell chamber assay. Results Ovarian CSC-LCs obtained through spheroid culture showed irregularly elongated appearance, CD24 negative, and OCT4 and SOX2 positive. IQGAP1 expression was decreased in ovarian CSC-LCs compared with parental 3AO cells, but increased de novo during the differentiation of CSC-LCs. Knockdown of IQGAP1 by specific small interfering RNA remarkably weakened invasion capacity of 2-day differentiated ovarian CSC-LCs. Conclusions Increased IQGAP1 expression during the differentiation of CSC-LCs is involved in an aggressive cell behavior, which may contribute to metastasis of ovarian cancer.

关键词： biology   IQGAP1   IQGAP2   IQGAP3   therapeutics  

摘要： IQGAP scaffold proteins are evolutionarily conserved in eukaryotes and facilitate the formation of complexes that regulate cytoskeletal dynamics, intracellular signaling, and intercellular interactions. Fungal and mammalian IQGAPs are implicated in cytokinesis. IQGAP1, IQGAP2, and IQGAP3 have diverse roles in vertebrate physiology, operating in the kidney, nervous system, cardiovascular system, pancreas, and lung. The functions of IQGAPs can be corrupted during oncogenesis and are usurped by microbial pathogens. Therefore, IQGAPs represent intriguing candidates for novel therapeutic agents. While modulation of the cytoskeletal architecture was initially thought to be the primary function of IQGAPs, it is now clear that they have roles beyond the cytoskeleton. This review describes contributions of IQGAPs to physiology at the organism level.

关键词： Actin cytoskeleton   IQ domain GTPase-activating protein 1   Nephrin   Podocyte  

摘要： Increasing data has shown that the cytoskeletal reorganization of podocytes is involved in the onset of proteinuria and the progression of glomerular disease. Nephrin behaves as a signal sensor of the slit diaphragm to transmit cytoskeletal signals to maintain the unique structure of podocytes. However, the nephrin signaling cascade deserves further study. IQGAP1 is a scaffolding protein with the ability to regulate cytoskeletal organization. It is hypothesized that IQGAP1 contributes to actin reorganization in podocytes through interaction with nephrin. IQGAP1 expression and IQGAP1-nephrin colocalization in glomeruli were progressively decreased and then gradually recovered in line with the development of foot process fusion and proteinuria in puromycin aminonucleoside-injected rats. In cultured human podocytes, puromycin aminonudeoside-induced disruption of F-actin and disorders of migration and spreading were aggravated by IQGAP1 siRNA, and these effects were partially restored by a wild-type IQGAP1 plasmid. Furthermore, the cytoskeletal disorganization stimulated by cytochalasin D in COS7 cells was recovered by cotransfection with wild-type IQGAP1 and nephrin plasmids but was not recovered either by single transfection of the wild-type IQGAP1 plasmid or by cotransfection of mutant IQGAP1 [Delta 1443(S -> A)] and wild-type nephrin plasmids. Co-immunoprecipitation analysis using lysates of COS7 cells overexpressing nephrin and each derivative-domain molecule of IQGAP1 demonstrated that the poly-proline binding domain and RasGAP domain in the carboxyl terminus of IQGAP1 are the target modules that interact with nephrin. Collectively, these findings showed that activated IQGAP1, as an intracellular partner of nephrin, is involved in actin cytoskeleton organization and functional regulation of podocytes. (c) 2015 Elsevier Inc. All rights reserved.

关键词： Insulin   Exocytosis   Endocytosis   Rab27a   IQGAP1   Coronin   3   Glucose   Small   GTPase  

摘要： The small GTPase Rab27 a is a member of the Rab family that is involved in membrane trafficking in various kinds of ***27 a has GTP-and GDP-bound forms,and their interconversion regulates intracellular signaling ***,only a GTP-bound GTPase binds its specific effectors with the resulting downstream signals controlling specific cellular *** previously identified novel Rab27a-interacting ***,some of these proteins interacted with GDP-bound Rab27 *** present study reviews recent progress in our understanding of the roles of Rab27 a and its effectors in the secretory *** pancreatic β-cells,GTP-bound Rab27 a regulates insulin secretion at the preexocytotic stages via its GTP-specific effectors such as Exophilin8/Slac2-c/My RIP and Slp4/*** stimulation causes insulin *** stimulation also converts Rab27 a from its GTP-to its GDP-bound ***-bound Rab27 a interacts with GDP-specific effectors and controls endocytosis of the secretory ***,Rab27 a cycling between GTP-and GDP-bound forms synchronizes with the recycling of secretory membrane to re-use the membrane and keep the β-cell volume constant.

关键词： Claudin   IQGAP1   Paracellular permeability   Polarized epithelium   Tight junction  

摘要： IQGAP1 is a scaffolding protein previously implicated in adherens junction formation. However, its role in the establishment or maintenance of tight junctions (TJs) has not been explored. We hypothesized that IQGAP1 could regulate TJ formation by modulating the expression and/or localization of junctional proteins, and we systematically tested this hypothesis in the model Madin-Darby canine kidney (MDCK) cell line. We find that IQGAP1 silencing enhances a transient increase in transepithelial electrical resistance (TER) observed during the early stages of TJ formation (Cereijido et al., 1978). Quantitative microscopy and biochemical experiments suggest that this effect of IQGAP1 on TJ assembly is accounted for by reduced expression and TJ recruitment of claudin 2, and increased TJ recruitment of claudin 4. Furthermore, we show that IQGAP1 also regulates TJ formation through its interactor CDC42, because IQGAP1 knockdown increases the activity of the CDC42 effector JNK and dominant-negative CDC42 prevents the increase in TER caused by IQGAP1 silencing. Hence, we provide evidence that IQGAP1 modulates TJ formation by a twofold mechanism: (1) controlling the expression and recruitment of claudin 2 and recruitment of claudin 4 to the TJ, and (2) transient inhibition of the CDC42-JNK pathway.

关键词： IQGAP1   IQGAP2   IQGAP3   scaffold   signaling  

摘要： Since its discovery in 1994, recognized cellular functions for the scaffold protein IQGAP1 have expanded immensely. Over 100 unique IQGAP1-interacting proteins have been identified, implicating IQGAP1 as a critical integrator of cellular signaling pathways. Initial research established functions for IQGAP1 in cell-cell adhesion, cell migration, and cell signaling. Recent studies have revealed additional IQGAP1 binding partners, expanding the biological roles of IQGAP1. These include crosstalk between signaling cascades, regulation of nuclear function, and Wnt pathway potentiation. Investigation of the IQGAP2 and IQGAP3 homologs demonstrates unique functions, some of which differ from those of IQGAP1. Summarized here are recent observations that enhance our understanding of IQGAP proteins in the integration of diverse signaling pathways.

关键词： Endothelium   Lung Injury   Permeability   Rac GTPases   Signal Transduction   Vascular Biology  

摘要： Hepatocyte growth factor (HGF) attenuates agonist-induced endothelial cell (EC) permeability and increases pulmonary endothelial barrier function via Rac-dependent enhancement of the peripheral actin cytoskeleton. However, the precise mechanisms of HGF effects on the peripheral cytoskeleton are not well understood. This study evaluated a role for Rac/Cdc42-specific guanine nucleotide exchange factor Asef and the multifunctional Rac effector, IQGAP1, in the mechanism of HGF-induced EC barrier enhancement. HGF induced Asef and IQGAP1 co-localization at the cell cortical area and stimulated formation of an Asef-IQGAP1 functional protein complex. siRNA-induced knockdown of Asef or IQGAP1 attenuated HGF-induced EC barrier enhancement. Asef knockdown attenuated HGF-induced Rac activation and Rac association with IQGAP1, and it abolished both IQGAP1 accumulation at the cell cortical layer and IQGAP1 interaction with actin cytoskeletal regulators cortactin and Arp3. Asef activation state was essential for Asef interaction with IQGAP1 and protein complex accumulation at the cell periphery. In addition to the previously reported role of the IQGAP1 RasGAP-related domain in the Rac-dependent IQGAP1 activation and interaction with its targets, we show that the IQGAP1 C-terminal domain is essential for HGF-induced IQGAP1/Asef interaction and Asef-Rac-dependent activation leading to IQGAP1 interaction with Arp3 and cortactin as a positive feedback mechanism of IQGAP1 activation. These results demonstrate a novel feedback mechanism of HGF-induced endothelial barrier enhancement via Asef/IQGAP1 interactions, which regulate the level of HGF-induced Rac activation and promote cortical cytoskeletal remodeling via IQGAP1Arp3/cortactin interactions.

关键词： IQGAP1   嘌呤霉素   足细胞   细胞骨架  

摘要： 目的:研究支架蛋白IQGAP1在足细胞骨架重组中的作用。方法:用嘌呤霉素(PAN)刺激小鼠足细胞,实时定量PCR检测IQGAP1mRNA的表达,免疫印迹法检测足细胞IQGAP1蛋白的表达,激光共聚焦显微镜观察足细胞骨架F-actin分布,F-actin肌动蛋白评分系统(CFS)分析骨架重组;IQGAP1siRNA和IQGAP1质粒转染足细胞,分别观察下调和上调足细胞IQGAP1表达对嘌呤霉素诱导足细胞细胞骨架重组的改变。结果:嘌呤霉素刺激足细胞后IQGAP1mRNA和蛋白表达下调(P<0.05),足细胞F-actin分布发生明显重组;转染IQGAP1siRNA,嘌呤霉素刺激足细胞F-actin重组进一步加重;转染IQGAP1质粒,嘌呤霉素刺激足细胞F-actin重组减轻。结论:IQGAP1可能参与嘌呤霉素诱导的足细胞细胞骨架重组。

关键词： IQGAP1   ERK   Radiochemotherapy   Rectal adenocarcinoma   Immunohistochemistry  

摘要： Treatment of rectal adenocarcinoma includes total mesorectal excision, which is preceded by radiochemotherapy (RCT) in cases of advanced disease. The response to RCT varies from total tumor regression to no effect but this heterogeneous response is unexplained. However, both radiation and treatment with 5-fluorouracil may induce treatment resistance through upregulation of the mitogen-activated protein kinase (MAPK) cascade. IQGAP1 is a scaffold protein that appears to be essential to MAPK signaling in cancers. We have therefore studied IQGAP1 protein expression in rectal adenocarcinomas before and after RCT. We demonstrate that cancer cells show increased apical staining for IQGAP1 following RCT. Interestingly, this increase is significantly higher in patients showing poor RCT responses. Our results also suggest that low levels of apical IQGAP1-staining in biopsies may predict the RCT response. Together, these data suggest that both the level and localization of IQGAP1 may influence the treatment response. (C) 2014 Elsevier Ireland Ltd. All rights reserved.