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.

关键词： M3 mAChR   IQGAP1   Rac1   VE-cadherin   beta-catenin  

摘要： The objective was to investigate whether M-3 muscarinic acetylcholine receptor (mAChR) dysfunction disrupts the linkage between the vascular endothelial (VE)-cadherin in the adherens junctional complex and the actin-based cytoskeleton, increasing vascular permeability in atherosclerosis. Western blotting revealed that a selective M-3 receptor antagonist, 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP), and M-3 receptor siRNA decrease VE-cadherin and beta-catenin in Triton X-100-insoluble fractions, indicating that M-3 receptor inhibition weakens the linkage between the VE-cadherin/beta-catenin complex and the actin cytoskeleton. Co-immunoprecipitation assays showed that M-3 receptor inhibition reduces Rac1 activity and the association of IQ motif-containing GTPase-activating protein 1 (IQGAP1) with Ras-related C3 botulinum toxin substrate 1 (Rac1), while increasing the interaction between IQGAP1 and beta-catenin. Using IQGAP1 siRNA, we found that IQGAP1 is required for stable interaction between VE-cadherin/beta-catenin and the actin cytoskeleton in quiescent endothelial cells;IQGAP1 siRNA augments the M-3 receptor inhibitioninduced dissociation between them. Moreover, S-nitroso-N-acetylpenicillamine (SNAP), a nitric oxide (NO) donor, attenuates this disassociation and Rac1 activity inhibition. The M-3 receptor facilitates interaction of the VE-cadherin-based adherens junctional complex and the actin-based cytoskeleton by maintaining Rac1 activity, which regulates the interaction between IQGAP1/Rac1 and IQGAP1/beta-catenin, and may contribute to endothelial barrier function under physiological conditions.

关键词： Cell Signaling   Estrogen   Estrogen Receptor   Nuclear Receptors   Protein-Protein Interactions   Scaffold Proteins   Transcription   IQGAP1  

摘要： Background: IQGAP1 is a scaffold protein that modulates diverse signaling pathways. Results: IQGAP1 binds to estrogen receptor- (ER) and ER, and knockdown of IQGAP1 impairs 17-estradiol (E-2)-stimulated transcriptional activation in human breast epithelial cells. Conclusion: IQGAP1 modulates ER function and is required for maximal E-2 function. Significance: IQGAP1 might be a therapeutic target for patients with breast carcinoma. The estrogen receptor (ER) is a steroid hormone receptor that acts as a transcription factor, modulating genes that regulate a vast range of cellular functions. IQGAP1 interacts with several signaling proteins, cytoskeletal components, and transmembrane receptors, thereby serving as a scaffold to integrate signaling pathways. Both ER and IQGAP1 contribute to breast cancer. In this study, we report that IQGAP1 binds ER and ER. In vitro analysis with pure proteins revealed a direct interaction between IQGAP1 and ER. Investigation with multiple short fragments of each protein showed that ER binds to the IQ domain of IQGAP1, whereas the hinge region of ER is responsible for binding IQGAP1. In addition, IQGAP1 and ER co-immunoprecipitated from cells, and the association was modulated by estradiol. The interaction has functional effects. Knockdown of endogenous IQGAP1 attenuated the ability of estradiol to induce transcription of the estrogen-responsive genes pS2, progesterone receptor, and cyclin D1. These data reveal that IQGAP1 binds to ER and modulates its transcriptional function, suggesting that IQGAP1 might be a target for therapy in patients with breast carcinoma.

关键词： 足细胞   细胞凋亡   血管紧张素Ⅱ   ras   GTP酶激活蛋白质类   细胞外   调节蛋白激酶1   2  

摘要： 目的研究IQ结构域GTP酶活化蛋白1（IQdomainGTPase-activatingprotein1，IQGAPl）在血管紧张素Ⅱ（Angll）诱导足细胞凋亡中的作用以及可能的分子机制。方法体外培养条件永生性小鼠足细胞（MPC），以不同浓度（0、10-12、10-10、10-8、10-6mol／L）AngⅡ处理MPC或10-8mol／LAngII刺激不同时间（0、1、3、6、12、24h），采用流式细胞术检测细胞凋亡率，免疫荧光、Western印迹法检测IQGAPl的表达及分布。IQGAPlsiRNA转染以及丝裂原活化蛋白激酶（MAPK）通路（包含p38、JNK和ERK1／23条主要通路）抑制剂SB202190（10μmol／L）、SP600125（25μmol／L）或U0126（10μmol／L）预处理MPC后，分别检测MAPK信号蛋白磷酸化水平及细胞凋亡率，并采用免疫共沉淀法研究IQGAPl与ERKl／2结合水平的变化。结果（1）AngⅡ可以诱导足细胞凋亡，且凋亡率随着刺激时间和刺激浓度的增加而进一步增加。（2）正常足细胞IQGAPl主要分布于细胞膜和胞质，随AngⅡ刺激浓度和刺激时间的增加，胞膜和胞质IQGAPl表达逐渐增高，且随剂量和时间增高。（3）SB202190、SP600125或U0126分别预处理足细胞，可显著降低Ang11诱导的足细胞凋亡（P〈0．05），但不影响IQGAPl蛋白表达。（4）IQGAPlsiRNA转染足细胞显著下调ERKl／2磷酸化水平（P〈0．05），降低IQGAPl与ERKl／2结合量（P〈0．05），并抑制AnglI诱导的细胞凋亡（P〈0．05），但对于p38以及JNK通路无显著影响。结论IQGAPl通过ERKl／2MAPK信号通路介导AngⅡ诱导的足细胞凋亡。

关键词： IQ motif containing GTPase activating   protein 1   K-Ras   Pancreatic cancer  

摘要： K-Ras is frequently mutated and activated especially in pancreatic cancers. To analyze K-Ras function, we have searched for K-Ras interacting proteins and found IQ motif containing GTPase activating protein 1 (IQGAP1) as a novel K-Ras binding protein. IQGAP1 has been known as a scaffold protein for B-Raf, MEK1/2 and ERK1/2. Here we showed that IQGAP1 selectively formed a complex with K-Ras but not with H-Ras, and recruited B-Raf to K-Ras. We found that IQ motif region of IQGAP1 interacted with K-Ras. Both active and inactive K-Ras interacted with IQGAPI, and effector domain mutants of K-Ras also associated with IQGAP1, indicating that IQGAP1 interacts with K-Ras irrespective of Ras-effectors like B-Raf. We also found that overexpression or knock-down of IQGAPI affected the interaction between K-Ras and B-Raf, and IQGAP1 overexpression increased ERK1/2 phosphorylation in K-Ras dependent manner in PANC1 cells. Our data suggest that IQGAP1 has a novel mechanism to modulate K-Ras pathway. (C) 2014 Elsevier Inc. All rights reserved.