关键词： Age-related macular degeneration   choroidal neovascularization   IQGAP1   Vascular endothelial growth factor   Vascular endothelial growth factor receptor 2   Rac1  

摘要： Loss of visual acuity in neovascular age-related macular degeneration (nAMD) occurs when factors activate choroidal endothelial cells (CECs) to transmigrate the retinal pigment epithelium into the sensory retina and develop into choroidal neovascularization (CNV). Active Rac1 (Rac1GTP) is required for CEC migration and is induced by different AMD-related stresses, including vascular endothelial growth factor (VEGF). Besides its role in pathologic events, Rac1 also plays a role in physiologic functions. Therefore, we were interested in a method to inhibit pathologic activation of Rac1. We addressed the hypothesis that IQGAP1, a scaffold protein with a Rac1 binding domain, regulates pathologic Rac1GTP in CEC migration and CNV. Compared to littermateIqgap1(+/+),Iqgap1(-/-)mice had reduced volumes of laser-induced CNV and decreased Rac1GTP and phosphorylated VEGFR2 (p-VEGFR2) within lectin-stained CNV. Knockdown of IQGAP1 in CECs significantly reduced VEGF-induced Rac1GTP, mediated through p-VEGFR2, which was necessary for CEC migration. Moreover, sustained activation of Rac1GTP induced by VEGF was eliminated when CECs were transfected with an IQGAP1 construct that is unable to bind Rac1. IQGAP1-mediated Src activation was involved in initiating Rac1 activation, CEC migration, and tube formation. Our findings indicate that CEC IQGAP1 interacts with VEGFR2 to mediate Src activation and subsequent Rac1 activation and CEC migration. In addition, IQGAP1 binding to Rac1GTP results in sustained activation of Rac1, leading to CEC migration toward VEGF. Our study supports a role of IQGAP1 and the interaction between IQGAP1 and Rac1GTP to restore CECs quiescence and, therefore, prevent vision-threatening CNV in nAMD.

关键词： Transgelin   IQGAP1   17-AAG   Scaffold proteins   Heat shock proteins  

摘要： Several studies have been conducted on the transgelin (TAGLN) protein and its critical role in cancer biology. However, the regulation of this protein and the way in which this regulation is correlated with the functions of IQ motif-containing GTPase-activating protein 1 (IQGAP1) in MDA-MB231 cells, remain unclear. We generated stable TAGLN-knockdown and TAGLN-overexpressing cells. These cells, along with their control counterparts, were cultured in the presence or absence of 17-AAG. The different cell groups were then subjected to functional assays to assess proliferation, chemotaxis, and invasion. TAGLN regulation was found to affect the efficacy of 17-AAG. The ability of TAGLN to influence the levels of IQGAP1 and its binding partners altered the critical functions of breast cancer cells. Therefore, the altered functionality of MDA-MB-231 cells, as a consequence of TAGLN regulation, is correlated with IQGAP1 signaling.

摘要： Background Hepatitis B virus (HBV) has a crucial role in the progression of hepatocellular carcinoma (HCC). Tumour cells must develop anoikis resistance in order to survive before metastasis. This study aimed to investigate the mechanism of IQGAP1 in HBV-mediated anoikis evasion and metastasis in HCC cells. Methods IQGAP1 expression was detected by immunohistochemistry, real-time PCR and immunoblot analysis. Lentiviral-mediated stable upregulation or knockdown of IGAQP1, immunoprecipitation, etc. were used in function and mechanism study. Results IQGAP1 was markedly upregulated in HBV-positive compared with HBV-negative HCC cells and tissues. IQGAP1 was positively correlated to poor prognosis of HBV-associated HCC patients. IQGAP1 overexpression significantly enhanced the anchorage-independent growth and metastasis, whereas IQGAP1-deficient HCC cells are more sensitive to anoikis. Mechanistically, we found that HBV-induced ROS enhanced the association of IQGAP1 and Rac1 that activated Rac1, leading to phosphorylation of Src/FAK pathway. Antioxidants efficiently inhibited IQGAP1-mediated anoikis resistance and metastasis. Conclusions Our study indicated an important mechanism by which upregulated IQGAP1 by HBV promoted anoikis resistance, migration and invasion of HCC cells through Rac1-dependent ROS accumulation and activation of Src/FAK signalling, suggesting IQGAP1 as a prognostic indicator and a novel therapeutic target in HCC patients with HBV infection.

关键词： IQGAP1   胰腺祖细胞   RNA干扰   细胞增殖  

摘要： 为探讨沉默IQ结构域三磷酸鸟苷合酶-激活蛋白1(IQ motif containing GTPase-activating protein 1,IQGAP1)基因的表达对胰腺祖细胞增殖的影响,本研究将靶向IQGAP1基因的小干扰RNA(siRNA)转染胰腺祖细胞,qPCR、Western blotting验证IQGAP1基因表达的下调,通过细胞计数试剂盒8(cell counting kit-8,CCK8)法检测IQGAP1基因沉默对胰腺祖细胞增殖的影响,流式细胞术检测细胞周期进程,qPCR、Western blotting检测细胞周期蛋白D2(cyclin D2,CCND2)的表达水平。结果显示,干扰片段有效沉默IQGAP1基因的表达,IQGAP1蛋白表达水平降低了(71.30±0.08)%;与对照组相比,沉默IQGAP1基因的表达使胰腺祖细胞增殖能力降低了(45.37±0.02)%,细胞周期阻滞在G0/G1期,CCND2基因表达水平明显降低。表明沉默IQGAP1基因可能通过抑制CCND2基因表达,抑制胰腺祖细胞的增殖。

关键词： IQGAP1   Senescence   Intercellular communication   Cellular bridges (CBs)   Tunneling nanotubes (TNTs)   Vascular smooth muscle cells (VSMCs)  

摘要： Cell senescence - an irreversible proliferation arrest - is one of the possible cellular responses to stress. There is a vast variety of stimuli, extrinsic and intrinsic, known to induce senescence, and several molecular pathways involved in the process;yet much still remains to be explained. Senescent cells can communicate with neighboring cells through secreted factors such as cytokines and chemokines. Several years ago it was shown that cells can also communicate in a more direct manner by an exchange of proteins via cellular bridges (CBs). Recent studies show that in senescent cells the intensity of such transfer increases. The research also revealed that Cdc42 and actin polymerization are indispensable for this process to occur. Here, we evaluate the hypothesis that, apart from actin and Cdc42, also IQGAP1 could be involved in direct intercellular communication. Our results showed that direct transfer occurred preferentially between senescent cells and that IQGAP1 was not essential for this process. Interestingly, cells harboring mutated IQGAP1 had altered morphology and were characterized by decreased proliferation, increased time of division and appearance of some senescence markers (increased activity of senescence-associated beta-galactosidase and induction of senescence-associated secretory phenotype). Our findings suggest that IQGAP1 dysfunction can induce senescence.

关键词： colorectal cancer   ERK1   2   IQGAP1   metastasis   PLS1  

摘要： Tumor metastasis is the dominant cause of death in colorectal cancer (CRC) patients, and it often involves dysregulation of various cytoskeletal proteins. Plastin 1 (PLS1) is an actin-bundling protein that has been implicated in the structure of intestinal epithelial microvilli;however, its role in CRC metastasis has not yet been determined. In this study, we demonstrated that PLS1 is highly expressed in 33.3% (45/135) of CRC patients and is correlated with lymph node metastasis and poor survival. In in vitro and in vivo experiments, PLS1 induced the migration and invasion of CRC cells and the metastases to the liver and lung in mice. Moreover, the expressions of key factors for CRC metastases, matrix metalloproteinase (MMP) 9 and 2, were enhanced by PLS1, which was dependent on phosphorylating ERK1/2 activated by IQGAP1/Rac1 signaling. The connection between these signals and PLS1 was further confirmed in CRC tissues of patients and the metastatic nodules from a mouse model. These findings suggest that PLS1 promotes CRC metastasis through the IQGAP1/Rac1/ERK pathway. Targeting PLS1 may provide a potential approach to inhibit the metastasis of CRC cells.

关键词： IQGAP1   pulmonary microvascular endothelium barrier   ARDS   RNA-Seq  

摘要： Pulmonary microvascular endothelium barrier plays a critical role in protecting the pulmonary tissue from inflammatory injury in acute respiratory distress syndrome and acute lung injury (ARDS/ALI). The dysregulation of IQ-GTPase-activating protein 1 (IQGAP1) was an important etiology of endothelium barrier injury. However, significant differentially expressed genes (DEGs) and signaling pathways directly regulated by IQGAP1 are too complicated to fully understand. In this research, we identified a total of 1216 DEGs regulated by knockdown of IQGAP1 in rat pulmonary microvascular endothelial cells on the basis of transcriptomic RNA sequencing (RNA-Seq). Among them, 665 were upregulated DEGs and 551 were downregulated DEGs. Gene ontology analysis has revealed that upregulated DEGs were mainly enriched in DNA replication, cell cycle, and chromosome formation, while downregulated DEGs were mainly involved in the regulation of many cellular bioprocesses including cell proliferation, cell adhesion, and cell migration. Kyoto Encyclopedia of Genes and Genomes pathways analysis toward DEGs showed that upregulated pathways were mainly about DNA replication, while the significantly downregulated pathways were about TNF signaling pathway and some inflammatory- and proliferation-related pathways. Furthermore, we choose 30 DEGs for validation by qRT-PCR, the results were quite consistent with the RNA-Seq. In addition, we also found that knockdown of IQGAP1 caused a significant impact on many cytokines and inflammatory factors, which play a vital role in ARDS/ALI. In summary, in this study on the basis of RNA-Seq, we found IQGAP1 not only exerts a crucial role in microvascular endothelium barrier but also plays an important role in inflammation, which might provide a new insight for future study on IQGAP1 in the related diseases such as ARDS/ALI.

摘要： Borealin is a key component of chromosomal passenger complex, which is vital in cytokinesis. IQ domain-containing GTPase-activating protein 1 (IQGAP1) also participates in cytokinesis. The correlation between Borealin and IQGAP1 during cytokinesis is not yet clear. Here, we used mass spectrometry and endogenous coimmunoprecipitation experiments to investigate the interaction between IQGAP1 and Borealin. Results of the current study showed that Borealin interacted directly with IQGAP1 bothin vitroandin vivo. Knockdown of IQGAP1 resulted in an abnormal location of Borealin in the midbody. Knocking down Borealin alone, IQGAP1 alone, or Borealin and IQGAP1 at the same time inhibited the completion of cytokinesis and formed multinucleated cells. Our results indicated that IQGAP1 interacts with Borealin during cytokinesis, and the correct localization of Borealin in the midbody during cytokinesis is determined by IQGAP1, and IQGAP1 may play an important role in regulating Borealin function in cytokinesis.

关键词： F-HABP07   HABP1   IQGAP1   senescence  

摘要： Hyaluronan-binding protein 1 (HABP1), a multi-compartmental, multi-functional protein has a wide range of functions, which can be attributed to its ability to associate with a variety of cellular ligands. Earlier we have reported that HABP1 overexpression in rat normal fibroblasts (F-HABP07) shows chronic generation of reactive oxygen species (ROS), induction of autophagy, and apoptosis. However, a significant proportion of cells remained viable after the majority went through apoptosis from 60 to 72 h. In this study, an attempt has been made to delineate the cellular events in the declined population of surviving cells. It has been elucidated here that, these cells at later time points of growth, that is, 72 and 84 h, not only appeared to shrink but also are devoid of autophagic vacuoles and displayed polyploidy. F-HABP07 cells exhibited an altered cytoskeletal structure from their parental cell line F111, assumed to be caused upon inhibition of actin polymerization and decrease in IQ motif-containing GTPase activating protein 1 (IQGAP1), a key protein associated with maintenance of cytoskeletal integrity. Enhanced expression and nuclear localization of AKT observed in F-HABP07 cells appears to be contributing toward the maintenance of high ROS levels in these cells and also potentially modulating the IQGAP1 activity. These observations, in fact have been considered to result in sustained DNA damage, which then leads to increased expression of p53 and activation of p21 and carry out the cellular events responsible for senescence. Subsequent assessment of the presence of positive beta-gal staining and enhanced expression of p16(INK4a) in F-HABP07, confirmed that HABP1 overexpressing fibroblasts undergo senescence.

关键词： Acetylation   ERK1/2   Fear memory   GluN2A   HDAC2   IQGAP1  

摘要： Epigenetic mechanisms of learning and memory are particularly interesting topics in neuroscience that have recently been investigated. As shown in our previous study, IQGAP1, a scaffolding protein of MAPK, is involved in fear memory through interactions with GluN2A-containing NMDA receptors and the ERK1/2 cascade. However, researchers have not determined whether histone posttranslational modifications are regulated by the IQGAP1/ERK signaling pathway. We performed in vivo studies using IQGAP1(-/-) and IQGAP1(+/+) mice to provide insights into the specific functions of IQGAP1 in memory processes and the precise mechanisms underlying its regulatory effects. IQGAP1(-/-) mice exhibited impaired fear memory, decreased levels of phosphorylated ERK1/2 and histone H3S10, decreased acetylation of H3K14, and decreased c-Fos expression in the hippocampus compared to IQGAP1 +/+ mice after fear conditioning. HDAC2 was significantly enriched at the cfos gene promoter in IQGAP1(-/-) mice. Correspondingly, the disruption of the epigenetic regulation induced by ERK1/2 signaling through an intra-hippocampal injection of the MEK antagonist U0126 or G1uN2A-selective pharmacological antagonist NVP-AAM077 blocked context-dependent memory formation, while no changes were observed after treatment with the G1uN2B-selective antagonist Ro25-6981. The administration of SAHA, a non-specific HDAC inhibitor, or knock-down of HDAC2 with shHDAC2-AAV in the dorsal hippocampus significantly rescued the impaired fear memory formation, H3S10 phosphorylation, H3K14 acetylation, and c-Fos expression in IQGAP1(-/-) mice. Thus, we postulated that the IQGAP1/ERK-dependent mechanism regulating histone posttranslational modifications via HDAC2 potentially underlies memory formation.