关键词： radial glia   outer radial glia   basal radial glia   human neocortex   gyrification   neurogenesis   neural progenitor   intermediate progenitor   TMEM14B   IQGAP1  

摘要： Human brain evolution is associated with expansion and folding of the neocortex. Increased diversity in neural progenitor (NP) populations (such as basally located radial glia [RG], which reside in an enlarged outer subventricular zone [OSVZ]) likely contributes to this evolutionary expansion, although their characteristics and relative contributions are only partially understood. Through single-cell transcriptional profiling of sorted human NP subpopulations, we identified the primate-specific TMEM14B gene as a marker of basal RG. Expression of TMEM14B in embryonic NPs induces cortical thickening and gyrification in postnatal mice. This is accompanied by SVZ expansion, the appearance of outer RG-like cells, and the proliferation of multiple NP subsets, with proportional increases in all cortical layers and normal lamination. TMEM14B drives NP proliferation by increasing the phosphorylation and nuclear translocation of IQGAP1, which in turn promotes G1/S cell cycle transitions. These data show that a single primate-specific gene can drive neurodevelopmental changes that contribute to brain evolution.

摘要： Sensing of cytosolic nucleotides is a critical initial step in the elaboration of type I IFN. One of several upstream receptors, cyclic GMP-AMP synthase, binds to cytosolic DNA and generates dicyclic nucleotides that act as secondary messengers. These secondary messengers bind directly to stimulator of IFN genes (STING). STING recruits TNFR-associated NF-kB kinase-binding kinase 1 which acts as a critical node that allows for efficient activation of IFN regulatory factors to drive the antiviral transcriptome. NLRC3 is a recently characterized nucleotide-binding domain, leucine-rich repeat containing protein (NLR) that negatively regulates the type I IFN pathway by inhibiting subcellular redistribution and effective signaling of STING, thus blunting the transcription of type I IFNs. NLRC3 is predominantly expressed in lymphoid and myeloid cells. IQGAP1 was identified as a putative interacting partner of NLRC3 through yeast two-hybrid screening. In this article, we show that IQGAP1 associates with NLRC3 and can disrupt the NLRC3-STING interaction in the cytosol of human epithelial cells. Furthermore, knockdown of IQGAP1 in THP1 and HeLa cells causes significantly more IFN-beta production in response to cytosolic nucleic acids. This result phenocopies NLRC3-deficient macrophages and fibroblasts and short hairpin RNA knockdown of NLRC3 in THP1 cells. Our findings suggest that IQGAP1 is a novel regulator of type I IFN production, possibly via interacting with NLRC3 in human monocytic and epithelial cells.

关键词： 7-helix receptor   G protein-coupled receptor (GPCR)   adhesion   cancer stem cells   intestine  

摘要： Leucine-rich repeat-containing G protein-coupled receptor 5 (LGR5) is a bona fide marker of adult stem cells in several epithelial tissues, most notably in the intestinal crypts, and is highly up-regulated in many colorectal, hepatocellular, and ovarian cancers. LGR5 activation by R-spondin (RSPO) ligands potentiates Wnt/beta-catenin signaling in vitro;however, deletion of LGR5 in stem cells has little or no effect on Wnt/beta-catenin signaling or cell proliferation in vivo. Remarkably, modulation of LGR5 expression has a major impact on the actin cytoskeletal structure and cell adhesion in the absence of RSPO stimulation, but the molecular mechanism is unclear. Here, we show that LGR5 interacts with IQ motif-containing GTPase-activating protein 1 (IQGAP1), an effector of Rac1/CDC42 GTPases, in the regulation of actin cytoskeleton dynamics and cell-cell adhesion. Specifically, LGR5 decreased levels of IQGAP1 phosphorylation at Ser-1441/1443, leading to increased binding of Rac1 to IQGAP1 and thus higher levels of cortical F-actin and enhanced cell-cell adhesion. LGR5 ablation in colon cancer cells and crypt stem cells resulted in loss of cortical F-actin, reduced cell-cell adhesion, and disrupted localization of adhesion-associated proteins. No evidence of LGR5 coupling to any of the four major subtypes of heterotrimeric G proteins was found. These findings suggest that LGR5 primarily functions via the IQGAP1-Rac1 pathway to strengthen cell-cell adhesion in normal adult crypt stem cells and colon cancer cells.

关键词： colorectal cancer   oxaliplatin   IQGAP1   scaffold protein  

摘要： IQGAP1 is a scaffolding protein that serves a key role in cell dynamics by integrating internal and external stimuli to distinct signal outputs. Previous studies have identified several genes that are significantly up-or downregulated in the peripheral white cells (PWCs) of patients with colorectal adenocarcinoma (CRC), who underwent oxaliplatin-based chemotherapy (CT). In addition, screening studies have reported that IQ-motif containing GTPase activating protein 1 (IQGAP1) transcriptional expression levels varied from 'off' to 'on' following oxaliplatin CT. In order to determine if variations previously described in PWCs are able to be observed at the protein level in tumors and in metastases following CT, the present study performed an immunohistochemical analysis of IQGAP1 in CRC and primary metastases. IQGAP1 expression was observed in the nuclear envelope and in lateral cell membranes and cytoplasm in normal colon tissue. However, in tumor tissue, cells exhibited a diffuse pattern, with variable expression levels of staining in the nuclear membrane and cytoplasm, with the highest expression intensity observed at the invasive front. In healthy and metastasized liver tissue and in the metastases themselves, expression levels varied from cell to cell from no expression to a high level. In the majority of cells, IQGAP1 co-localized with microtubules at the cytoplasmic face of the nuclear envelope. Strong positive expression was observed in areas of the lesion where cells were detaching from the lesion into the lumen. Despite the homogeneous IQGAP1 staining pattern observed in healthy colon tissue sections, CRC demonstrated heterogeneity in staining, which was more marked in metastasized liver tissue resected following CT. However, the most notable findings were the observed effects on the cellular and subcellular distribution and its implications for cancer biology. These results suggest that IQGAP1 may be a putative biomarker, a candidate for clinical diagnostics

摘要： Ceramide, a bioactive lipid and signaling molecule associated with cardiovascular disease, is known to activate extracellular signal regulated kinases 1 and 2 (ERK1/2). Here, we determined that the effect of ceramide on ERK1/2 is mediated by ceramide signaling on an ERK scaffold protein, IQ motif containing GTPase activating protein 1 (IQGAP1). Experiments were performed with aortic smooth muscle cells using inhibitor screening, small interfering RNA (siRNA), immunoprecipitation (IP), immunoblots and bioinformatics. We report here that C6 ceramide increases serum-stimulated ERK1/2 activation in a manner dependent on the ERK1/2 scaffold IQGAP1. C6 ceramide increases IQGAP1 protein levels by preventing its cleavage. Bioinformatic analysis of the IQGAP1 amino acid sequence revealed potential cleavage sites for proteases of the proprotein convertase family that match the cleavage products. These potential cleavage sites overlap with known motifs for lysine acetylation. Deacetylase inhibitor treatment increased IQGAP1 acetylation and reduced IQGAP1 cleavage. These data are consistent with a model in which IQGAP1 cleavage is regulated by acetylation of the cleavage sites. Activation of ERK1/2 by ceramide, known to increase lysine acetylation, appears to be mediated by acetylationdependent stabilization of IQGAP1. This novel mechanism could open new possibilities for therapeutic intervention in cardiovascular diseases.

关键词： IQGAP1   足细胞   细胞骨架重组   嘌呤霉素  

摘要： 目的 :探讨IQ结构域GTP酶活化蛋白1(IQ domain GTPase-activating protein 1,IQGAP1)对足细胞细胞骨架重组的调节作用。方法:嘌呤霉素(PAN)刺激小鼠足细胞后,运用实时定量PCR和Western blot印迹法分别检测细胞内IQGAP1m RNA和蛋白表达水平,激光共聚焦显微镜观察足细胞骨架F-actin的分布,F-actin肌动蛋白评分系统(CFS)对骨架重组进行分析,并进一步观察上调和下调足细胞IQGAP1表达对PAN诱导的足细胞骨架重组的影响。结果:(1)与对照组相比,PAN刺激组足细胞内IQGAP1 mRNA和蛋白表达明显下降(P<0.05),足细胞F-actin排列紊乱,CFS明显升高;(2)IQGAP1 si RNA进一步抑制IQGAP1表达后,PAN引起的上述足细胞F-actin重组更加明显(P<0.05);(3)转染p Cantag-myc-IQGAP1质粒促进IQGAP1表达后,PAN诱导的足细胞F-actin排列紊乱显著减轻,CFS明显下降(P<0.05)。结论:IQGAP1能抑制嘌呤霉素诱导的足细胞骨架重组,对维持足细胞正常骨架结构起着重要作用。

关键词： IQGAP1   脓毒症   呼吸窘迫综合征,急性   IQGAP1  

摘要： 脓毒症是临床危重病患者死亡的重要原因之一.肺脏是脓毒症时最易受损的靶器官,脓毒症患者常并发急性呼吸窘迫综合征（ARDS）,其主要机制是细胞骨架重排、细胞-细胞间连接改变,最终导致血管渗漏.IQ模序的三磷酸鸟苷酶活化蛋白1（IQGAP1）是近年来发现的细胞骨架动力学调节的关键组成部分.目前,IQGAP1与脓毒症相关ARDS的关系尚不完全清楚,本文在分子水平上对IQGAP1与病原微生物的相互作用机制、肺微血管屏障功能及细胞骨架的变化等研究进行综述.

关键词： 化疗敏感度   具有IQ结构域的GTP激酶活化蛋白1   食管鳞癌   小干扰RNA   转录因子E2相关因子2  

摘要： 目的研究具有IQ结构域的GTP激酶活化蛋白1基因(IQGAP1)对食管癌细胞KYSE150化疗敏感度的影响及其相关作用机制。方法构建针对IQGAP1基因的小干扰RNA(si RNA)并转染至食管鳞癌细胞株KYSE150,采用MTT法观察KYSE150细胞对化疗药物顺铂敏感度的改变;流式细胞技术检测IQGAP1基因沉默前后顺铂对KYSE150细胞周期分布及凋亡的影响;Western blot检测细胞转染前后转录因子E2相关因子2(nuclear factor erythroid-2 related factor 2,Nrf2)和多药耐药相关蛋白1(MRP1)的表达水平变化。结果转染si RNA可显著下调KYSE150细胞中的IQGAP1 m RNA和蛋白表达水平;经(1、5、10、20)μmol/L顺铂处理细胞24 h后,干扰组(IQGAP1-si RNA)的细胞生存率均较对照组发生明显下降(P<0.05);流式细胞仪检测结果显示干扰组在顺铂处理后G_0/G_1期细胞比例和凋亡率均明显高于对照组(P<0.05);Western blot结果显示IQGAP1基因沉默后,Nrf2和MRP1蛋白表达下调。结论沉默IQGAP1基因可有效提高人食管鳞癌细胞株KYSE150对顺铂的化疗敏感度,该作用可能是通过下调Nrf2和MRP-1蛋白表达来实现的。

关键词： 乳腺肿瘤   基因表达调控   钙黏着糖蛋白类   SASH1蛋白   含IQ模序的GTP酶活化蛋白1  

摘要： 目的:探讨SASH1(SAM-and SH3-domain containing 1)基因作为一个新的抑癌基因,在调节乳腺癌转移过程中的分子作用机制。方法:免疫组织化学法检测人乳腺癌组织中SASH1、含IQ模序的GTP酶活化蛋白1(IQ motif-containing GTPase activating protein 1,IQGAP1)和E-钙黏蛋白(E-cadherin)的表达水平,并分析三者之间的相关性,以及SASH1和IQGAP1表达与乳腺癌患者临床指标的相关性。构建重组质粒HA-IQGAP1-pcDNA3.0和pEGFP-C3-SASH1,并将其转染人胚胎肾细胞HEK-293T,然后采用免疫沉淀-蛋白质印迹法分析SASH1与IQGAP1的相互作用。结果:人乳腺癌组织中,SASH1与IQGAP1的表达存在相关性(P<0.05),而且二者分别与E-cadherin的表达明显相关(P值均<0.001);另外,SASH1和IQGAP1蛋白表达分别与乳腺癌的肿瘤直径和肿瘤分级有相关性(P值均<0.05),但与淋巴结转移无相关性(P值均>0.05)。成功构建重组质粒HA-IQGAP1-pcDNA3.0和pEGFP-C3-SASH1;重组质粒转染HEK-293T细胞后,发现SASH1与IQGAP1之间存在蛋白-蛋白相互作用。结论:SASH1与IQGAP1结合后可发生蛋白-蛋白相互作用,并且与E-cadherin的表达密切相关。推测SASH1可能与IQGAP1和E-cadherin形成一条新的调节乳腺癌转移的信号轴。

关键词： Chlamydia pneumoniae   Angiogenesis   Vascular endothelial cell   IQ domain GTPase-activating protein 1   Neural Wiskott-Aldrich syndrome protein  

摘要： Chlamydia pneumoniae (C. pneumoniae) infection plays a potential role in angiogenesis. However, it is still an enigma how C. pneumoniae is involved in this process. Therefore, we investigated the effect of C. pneumoniae infection on angiogenesis, and then explored the roles of IQGAPI-related signaling in C. pneumoniae infection-induced angiogenesis. C. pneumoniae infection significantly enhanced angiogenesis as assessed by the tube formation assay possibly by inducing vascular endothelial cell (VEC) migration in the wound healing and Transwell migration assays. Subsequently, immunoprecipitation, Western blot and tube formation assay results showed that the phosphorylation of both IQGAPI and N-WASP was required for the angiogenesis induced by C. pneumoniae infection. Our co-immunoprecipitation study revealed that IQGAP1 physically associated with N-WASP after C. pneumoniae infection of VECs. Actin polymerization assay further showed that in C pneumoniae-infected VECs, both IQGAPI and N-WASP were recruited to filamentous actin, and shared some common compartments localized at the leading edge of lamellipodia, which was impaired after the depletion of IQGAPI by using the small interference RNA. Moreover, the knockdown of IQGAP1 also significantly decreased N-WASP phosphorylation at Tyr256 induced by C pneumoniae infection. We conclude that C pneumoniae infection promotes VEC migration and angiogenesis presumably through the IQGAP1-related signaling pathway. (C) 2017 Elsevier GmbH. All rights reserved.