关键词： Thymosin beta(4) (T beta(4))   ILK   IQGAP1   Rac1   Migration  

摘要： Thymosin beta(4) (T beta(4)) overexpression increases cell migration and tumor metastasis. Hence, understanding the mechanism of cancer cell migration induced by T beta(4) may provide means to inhibit their metastasis. We demonstrated higher Rac1 activities and expression levels of IQGAP1 and ILK in highly migrated T beta(4)-overexpressing SW480 cells. In addition, IQGAP1 formed a complex with ILK and knockdown of T beta(4) simultaneously reduced ILK and IQGAP1 protein levels as well as their migration ability. These findings suggest that T beta(4) increases migration of colon cancer cells via activating Rac1 by elevating IQGAP1/ILK complexes and IHC results illustrated a similar mechanism occurring in vivo. (C) 2011 Elsevier Ireland Ltd. All rights reserved.

关键词： Immune synapse   IQGAP1   MTOC   NK cells   shRNA  

摘要： Natural killer (NK) cells form a region of tight contact called the NK immunological synapse (NKIS) with their target cells. This is a dynamic region serving as a platform for targeted signaling and exocytotic events. We previously identified IQGAP1 as a cytoskeletal component of the NK-like cell line YTS. The present study was undertaken to determine the role of IQGAP1 in the function of NK cells. Silencing of IQGAP1 expression resulted in almost complete loss of the cytotoxic activity of YTS cells. Loss of IQGAP1 did not prevent conjugate formation with target cells but it did result in a failure to reorient the microtubule organizing centre to the immune synapse. Significantly, IQGAP1 expression was required for the perigranular accumulation of an F-actin network. IQGAP1 was shown to undergo marked rearrangements during synapse maturation in effector target conjugates of YTS or primary NK cells. These results suggest previously undescribed role(s) for IQGAP1 in regulating multiple aspects of cytoskeletal organization and granule polarization in NK cells.

关键词： HER-2 protein   BREAST cancer   PROTEIN binding   TRASTUZUMAB   CELL proliferation  

摘要： Human epidermal growth factor receptor 2 (HER2) is overexpressed in 20-25% of breast cancers. Increased HER2 expression is an adverse prognostic factor and correlates with decreased patient survival. HER2-positive (HER2(+)) breast cancer is treated with trastuzumab. Unfortunately, some patients are intrinsically refractory to therapy, and many who do respond initially become resistant within 1 year. Understanding the molecular mechanisms underlying HER2 signaling and trastuzumab resistance is essential to reduce breast cancer mortality. IQGAP1 is a ubiquitously expressed scaffold protein that contains multiple protein interaction domains. By regulating its binding partners IQGAP1 integrates signaling pathways, several of which contribute to breast tumorigenesis. We show here that IQGAP1 is overexpressed in HER2(+) breast cancer tissue and binds directly to HER2. Knockdown of IQGAP1 decreases HER2 expression, phosphorylation, signaling, and HER2-stimulated cell proliferation, effects that are all reversed by reconstituting cells with IQGAP1. Reducing IQGAP1 up-regulates p27, and blocking this increase attenuates the growth inhibitory effects of IQGAP1 knockdown. Importantly, IQGAP1 is overexpressed in trastuzumab-resistant breast epithelial cells, and reducing IQGAP1 both augments the inhibitory effects of trastuzumab and restores trastuzumab sensitivity to trastuzumab-resistant SkBR3 cells. These data suggest that inhibiting IQGAP1 function may represent a rational strategy for treating HER2(+) breast carcinoma.

关键词： cdc42 GTP-Binding Protein/metabolism   Chemotaxis/drug effects   Chemotaxis/physiology   Chromatography, Liquid   HEK293 Cells   HL-60 Cells   Humans   Intercellular Junctions/drug effects   Intercellular Junctions/metabolism   Interleukin-8/pharmacology   Mass Spectrometry   Protein Binding/drug effects   Proteomics   ras GTPase-Activating Proteins/chemistry   ras GTPase-Activating Proteins/metabolism   Receptors, Interleukin-8B/metabolism  

摘要： Background: Chemotaxis is essential for a number of physiological processes including leukocyte recruitment. Chemokines initiate intracellular signaling pathways necessary for chemotaxis through binding seven transmembrane G protein-couple receptors. Little is known about the proteins that interact with the intracellular domains of chemokine receptors to initiate cellular signaling upon ligand binding. CXCR2 is a major chemokine receptor expressed on several cell types, including endothelial cells and neutrophils. We hypothesize that multiple proteins interact with the intracellular domains of CXCR2 upon ligand stimulation and these interactions comprise a "chemosynapse", and play important roles in transducing CXCR2 mediated signaling processes. Methodology/Principal Findings: In an effort to define the complex of proteins that assemble upon CXCR2 activation to relay signals from activated chemokine receptors, a proteomics approach was employed to identify proteins that co-associate with CXCR2 with or without ligand stimulation. The components of the CXCR2 "chemosynapse" are involved in processes ranging from intracellular trafficking to cytoskeletal modification. IQ motif containing GTPase activating protein 1 (IQGAP1) was among the novel proteins identified to interact directly with CXCR2. Herein, we demonstrate that CXCR2 co-localizes with IQGAP1 at the leading edge of polarized human neutrophils and CXCR2 expressing differentiated HL-60 cells. Moreover, amino acids 1-160 of IQGAP1 directly interact with the carboxyl-terminal domain of CXCR2 and stimulation with CXCL8 enhances IQGAP1 association with Cdc42. Conclusions: Our studies indicate that IQGAP1 is a novel essential component of the CXCR2 "chemosynapse".

关键词： IQGAP1   MAPKs   AKT   Heart hypertrophy   Pressure overload  

摘要： Aims The Raf-MEK1/2-ERK1/2 (ERK1/2-extracellular signal-regulated kinases 1/2) signalling cascade is crucial in triggering cardiac responses to different stress stimuli. Scaffold proteins are key elements in coordinating signalling molecules for their appropriate spatiotemporal activation. Here, we investigated the role of IQ motif-containing GTPase-activating protein 1 (IQGAP1), a scaffold for the ERK1/2 cascade, in heart function and remodelling in response to pressure overload. Methods and results IQGAP1-null mice have unaltered basal heart function. When subjected to pressure overload, IQGAP1-null mice initially develop a compensatory hypertrophy indistinguishable from that of wild-type (WT) mice. However, upon a prolonged stimulus, the hypertrophic response develops towards a thinning of left ventricular walls, chamber dilation, and a decrease in contractility, in an accelerated fashion compared with WT mice. This unfavourable cardiac remodelling is characterized by blunted reactivation of the foetal gene programme, impaired cardiomyocyte hypertrophy, and increased cardiomyocyte apoptosis. Analysis of signalling pathways revealed two temporally distinct waves of both ERK1/2 and AKT phosphorylation peaking, respectively, at 10 min and 4 days after aortic banding in WT hearts. IQGAP1-null mice show strongly impaired phosphorylation of MEK1/2-ERK1/2 and AKT following 4 days of pressure overload, but normal activation of these kinases after 10 min. Pull-down experiments indicated that IQGAP1 is able to bind the three components of the ERK cascade, namely c-Raf, MEK1/2, and ERK1/2, as well as AKT in the heart. Conclusion These data demonstrate, for the first time, a key role for the scaffold protein IQGAP1 in integrating hypertrophy and survival signals in the heart and regulating long-term left ventricle remodelling upon pressure overload.

摘要： Studies in patient samples and in cell culture suggest inhibiting IQGAP1 could help treat Herceptin trastuzumab–resistant, HER2-positive breast cancer.

关键词： Ventral body wall defects   IQGAP1   Rac1   Cdc42   Chick embryo  

摘要： Cadmium (Cd) induces ventral body wall defects (VBWD) in the chick embryo, with adherens junctions (AJs) breakdown at 4h post treatment (4H). Signalling by which Cd disrupts AJs in this model remains unclear. IQGAP1 regulates AJs via binding to Cdc42 and Rac1, Rho-family GTPases. Activation of IQGAP1-Cdc42 interaction regulates AJs positively, whereas Rac1 activation inhibits AJs. We hypothesised that IQGAP1 and Cdc42 are downregulated and Rac1 is upregulated during embryogenesis in the Cd chick model. Chick embryos were explanted and treated with saline or Cd after 60 h incubation. Chicks were harvested at 1H, 4H and 8H post treatment and RT-PCR and immunohistochemistry were performed. Gene expression levels of IQGAP1 and Cdc42 were significantly downregulated and Rac1 was upregulated in Cd group compared to controls only at 4H. Immunoreactivity of IQGAP1 and Cdc42 was also markedly decreased, whereas Rac1 was increased in Cd group compared to controls at 4H. Alteration of IQGAP and Rho-family GTPases may cause VBWD in Cd chick model by inducing the dissociation of cadherin-mediated AJs. (C) 2011 Elsevier Inc. All rights reserved.

关键词： NEUROBEHAVIORAL disorders   BRAIN diseases   DEMENTIA   NERVOUS system   PSYCHOSES  

摘要： General or brain-region-specific decreases in spine number or morphology accompany major neuropsychiatric disorders. It is unclear, however, whether changes in spine density are specific for an individual mental process or disorder and, if so, which molecules confer such specificity. Here we identify the scaffolding protein IQGAP1 as a key regulator of dendritic spine number with a specific role in cognitive but not emotional or motivational processes. We show that IQGAP1 is an important component of NMDAR multiprotein complexes and functionally interacts with the NR2A subunits and the extracellular signal-regulated kinase 1 (ERK1) and ERK2 signaling pathway. Mice lacking the IQGAP1 gene exhibited significantly lower levels of surface NR2A and impaired ERK activity compared to their wild-type littermates. Accordingly, primary hippocampal cultures of IQGAP1(-/-) neurons exhibited reduced surface expression of NR2A and disrupted ERK signaling in response to NR2A-dependent NMDAR stimulation. These molecular changes were accompanied by region-specific reductions of dendritic spine density in key brain areas involved in cognition, emotion, and motivation. IQGAP1 knockouts exhibited marked long-term memory deficits accompanied by impaired hippocampal long-term potentiation (LTP) in a weak cellular learning model;in contrast, LTP was unaffected when induced with stronger stimulation paradigms. Anxiety-and depression-like behavior remained intact. On the basis of these findings, we propose that a dysfunctional IQGAP1 gene contributes to the cognitive deficits in brain disorders characterized by fewer dendritic spines.

关键词： Aurora-A   骨架蛋白   稳定性   酶蛋白   GTPase  

摘要： 目的：IQGAP1是IQGAPs（IQ motif containing GTPase activating proteins）家族中的一员，

关键词： IQGAP1蛋白   肿瘤  

摘要： IQGAP1是一种能结合多种信号分子及结构分子的骨架蛋白。通过与目的蛋白相互作用，参与信号通路的整合和细胞功能的调节。越来越多的研究发现，IQGAP1可通过促进细胞增殖和转化，降低细胞黏附性以及刺激细胞活动性和侵袭性而在肿瘤的发生发展中扮演重要角色。