IQGAP1, a novel vascular endothelial growth factor receptor binding protein, is involved in reactive oxygen species--dependent endothelial migration and proliferation

The Potential Role of Kallistatin in the Development of Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA) is a vascular condition that causes permanent dilation of the abdominal aorta, which can lead to death due to aortic rupture. The only treatment for AAA is surgical repair, and there is no current drug treatment for AAA. Aortic inflammation, vascular smooth muscle cell apoptosis, angiogenesis, oxidative stress and vascular remodeling are implicated in AAA pathogenesis. Kallistatin is a serine proteinase inhibitor, which has been shown to have a variety of functions, potentially relevant in AAA pathogenesis. Kallistatin has been reported to have inhibitory effects on tumor necrosis factor alpha (TNF-α) signaling induced oxidative stress and apoptosis. Kallistatin also inhibits vascular endothelial growth factor (VEGF) and Wnt canonical signaling, which promote inflammation, angiogenesis, and vascular remodeling in various pre-clinical experimental models. This review explores the potential protective role of kallistatin in AAA pathogenesis.

IQGAP1 gene silencing induces apoptosis and decreases the invasive capacity of human hepatocellular carcinoma cells

IQ motif-containing GTPase-activating proteins (IQGAPs) belong to a conserved family, and they are involved in various intracellular processes. IQGAP1 is expressed in all cells, while IQGAP2 and IQGAP3 are mainly expressed in hepatic cells. IQGAP1 has been suggested to be an oncogene, while IQGAP2 is considered a tumor-suppressor gene. However, the relationship between RAS family genes and IQGAP genes remains unclear. We recently demonstrated this interaction in a chemically induced mouse liver cancer. In this study, IQGAP1 expression was partially silenced in human hepatocellular carcinoma (HepG2) cells. We investigated the impact of IQGAP1 silencing on the interactions of IQGAP and RAS with several apoptotic proteins, including caspase-3 (CASP3), BCL2-associated X protein (BAX), and B-cell leukemia/lymphoma 2 (BCL2). Additionally, we investigated the effects of the interactions of these genes on cell viability, proliferation, apoptosis, and invasive capacity. IQGAP1 siRNA-treated HepG2 cells showed lower invasive capacity than the control cells, and this reduction was time- and vector concentration-dependent. In addition, IQGAP1 silencing resulted in significantly lower IQGAP1 level and subsequently higher IQGAP2 and IQGAP3 expression in HepG2 cells than in the control. Flow cytometry analyses indicated that the silencing of IQGAP1 can induce early and late apoptosis in HepG2 cells. Additionally, IQGAP2, IQGAP3, CASP3, and BAX were upregulated whereas IQGAP1 and BCL2 were downregulated in the siRNA-treated cells. Furthermore, we observed that the mRNA levels of HRAS, KRAS, NRAS, and MRAS decreased upon IQGAP1 silencing. These findings indicate that IQGAP1 potentially regulates the expression of IQGAP and RAS gene families and demonstrate its regulatory role in the apoptotic network. Taken together, our findings suggest that IQGAP1 silencing plays crucial roles in the apoptosis of HepG2 cells and lowers their proliferative and invasive capacities.

Scaffolding protein IQGAP1: an insulin-dependent link between caveolae and the cytoskeleton in primary human adipocytes?

The ubiquitously expressed IQ motif-containing GTPase activating protein-1 (IQGAP1) is a scaffolding protein implicated in an array of cellular functions, in particular by binding to cytoskeletal elements and signaling proteins. A role of IQGAP1 in adipocytes has not been reported. We therefore investigated the cellular IQGAP1 interactome in primary human adipocytes. Immunoprecipitation and quantitative mass spectrometry identified caveolae and caveolae-associated proteins as the major IQGAP1 interactors alongside cytoskeletal proteins. We confirmed co-localization of IQGAP1 with the defining caveolar marker protein caveolin-1 by confocal microscopy and proximity ligation assay. Most interestingly, insulin enhanced the number of IQGAP1 interactions with caveolin-1 by five-fold. Moreover, we found a significantly reduced abundance of IQGAP1 in adipocytes from patients with type 2 diabetes compared with cells from nondiabetic control subjects. Both the abundance of IQGAP1 protein and mRNA were reduced, indicating a transcriptional defect in diabetes. Our findings suggest a novel role of IQGAP1 in insulin-regulated interaction between caveolae and cytoskeletal elements of the adipocyte, and that this is quelled in the diabetic state.

Epigenetic regulation of IQGAP2 promotes ovarian cancer progression via activating Wnt/β-catenin signaling

Ovarian cancer is the most lethal gynecologic malignancy and most cases are diagnosed at an advanced stage with metastases; however, the molecular events supporting ovarian cancer development and progression remain poorly understood. In this study, by analysis of the genome-scale DNA methylation profiles of 8 healthy ovaries, 89 ovarian cancers and the corresponding 4 normal ovaries from The Cancer Genome Atlas, we unveiled the abnormalities in gene methylation of ovarian cancers, and found that IQGAP2 one of the most frequently altered genes, was significantly hypermethylated in ovarian cancer. There was an inverse correlation between IQGAP2 DNA methylation and mRNA expression, and IQGAP2 expression was downregulated in ovarian cancer. Further survival analysis indicated that decreased IQGAP2 was associated with a worse progression-free survival of patient with ovarian cancer, and biological function studies demonstrated that IQGAP2 inhibited ovarian cancer cell epithelial-mesenchymal transition, migration and invasion via suppression of Wnt-induced β-catenin nuclear translocation and transcriptional activity. Thus, these data identified IQGAP2 as a novel tumor suppressor for ovarian cancer to inhibit cell invasion through regulating Wnt/β-catenin signaling, and provided a new biomarker and potential therapeutic strategy for this disease.

Behind the Link between Copper and Angiogenesis: Established Mechanisms and an Overview on the Role of Vascular Copper Transport Systems

Angiogenesis critically sustains the progression of both physiological and pathological processes. Copper behaves as an obligatory co-factor throughout the angiogenic signalling cascades, so much so that a deficiency causes neovascularization to abate. Moreover, the progress of several angiogenic pathologies (e.g. diabetes, cardiac hypertrophy and ischaemia) can be tracked by measuring serum copper levels, which are being increasingly investigated as a useful prognostic marker. Accordingly, the therapeutic modulation of body copper has been proven effective in rescuing the pathological angiogenic dysfunctions underlying several disease states. Vascular copper transport systems profoundly influence the activation and execution of angiogenesis, acting as multi-functional regulators of apparently discrete pro-angiogenic pathways. This review concerns the complex relationship among copper-dependent angiogenic factors, copper transporters and common pathological conditions, with an unusual accent on the multi-faceted involvement of the proteins handling vascular copper. Functions regulated by the major copper transport proteins (CTR1 importer, ATP7A efflux pump and metallo-chaperones) include the modulation of endothelial migration and vascular superoxide, known to activate angiogenesis within a narrow concentration range. The potential contribution of prion protein, a controversial regulator of copper homeostasis, is discussed, even though its angiogenic involvement seems to be mainly associated with the modulation of endothelial motility and permeability.

IQGAP3 is essential for cell proliferation and motility during zebrafish embryonic development

IQGAPs are scaffolding proteins that regulate actin assembly, exocyst function, cell motility, morphogenesis, adhesion and division. Vertebrates express 3 family members: IQGAP1, IQGAP2, and IQGAP3. IQGAP1 is known to stimulate nucleation of branched actin filaments through N-WASP and the Arp2/3 complex following direct binding to cytoplasmic tails of ligand-activated growth factor receptors, including EGFR, VEGFR2 and FGFR1. By contrast, little is known about functions of IQGAP2 or IQGAP3. Using in situ hybridization on whole mount zebrafish (Danio rerio) embryos, we show that IQGAP1 and IQGAP2 are associated with discrete tissues and organs, while IQGAP3 is mainly expressed in proliferative cells throughout embryonic and larval development. Morpholino knockdowns of IQGAP1 and IQGAP2 have little effect on embryo morphology while loss of function of IQGAP3 affects both cell proliferation and cell motility. IQGAP3 morphant phenotypes are similar to those resulting from overexpression of dominant negative forms of Ras or of Fibroblast Growth Factor Receptor 1 (FGFR1), suggesting that IQGAP3 plays a role in FGFR1-Ras-ERK signaling. In support of this hypothesis, dominant negative forms of FGFR1 or Ras could be rescued by co-injection of zebrafish IQGAP3 mRNA, strongly suggesting that IQGAP3 acts as a downstream regulator of the FGFR1-Ras signaling pathway.

IQGAPs as Key Regulators of Actin-cytoskeleton Dynamics

The actin-cytoskeleton plays a critical role in various biological processes, including cell migration, development, tissue remodeling, and memory formation. Both extracellular and intracellular signals regulate reorganization of the actin-cytoskeleton to modulate tissue architecture and cellular morphology in a spatiotemporal manner. Since the discovery that activation of Rho family GTPases induces actin-cytoskeleton reorganization, the mode of action of Rho family GTPases has been extensively studied and individual effectors have been characterized. The actin-binding protein IQGAP1 was identified as an effector of Rac and Cdc42 and is the founding member of the IQGAP family with two additional isoforms. The IQGAP family shows conserved domain organization, and each member displays a specific expression pattern in mammalian tissues. IQGAPs regulate the actin-cytoskeleton alone and with their binding partners, thereby controlling diverse cellular processes, such as cell migration and adhesion. Here, we introduce IQGAPs as an actin-cytoskeleton regulator.

IQGAP1 modulates the proliferation and invasion of thyroid cancer cells in response to estrogen

Thyroid cancer is an endocrine malignancy with a high incidence rate, which is affected by female hormones, particularly estrogens, in its growth and progression. IQ-domain GTPase-activating protein 1 (IQGAP1) is overexpressed in a range of types of cancer and is reported to interact with estrogen receptor α (ERα) in breast cancer cells. However, the association between IQGAP1 and ERα in thyroid cancer cells remains to be elucidated. In this study, the role of IQGAP1 in thyroid cancer cells was examined. The expression of IQGAP1 (190 kDa) was analyzed using western blot analysis, which indicated that IQGAP1 was overexpressed in thyroid cancer tissues and FTC133 cells. However, IQGAP1 knockdown in the FTC133 cells led to a significant downregulation in ERα transcriptional activity, cell proliferation, cell adhesion and cell invasion under 17β-estradiol (E2) conditions. Furthermore, ERα knockdown inhibited the enhanced protein expression levels of phosphorylated ERK1/2 and cyclin D1, which were induced by the overexpression of IQGAP1. Co-immunoprecipitation was also performed in thyroid cancer cells and the results suggested that IQGAP1 directly interacted with ERα in the FTC133 cells and the co-transfected COS-7 cells. Taken together, these findings revealed that IQGAP1 may directly interact with ERα and serve as a signal integrator, mediating ERα transcriptional activity, cell proliferation and cell invasion during the progression of thyroid cancer.

bFGF Promotes the Migration of Human Dermal Fibroblasts under Diabetic Conditions through Reactive Oxygen Species Production via the PI3K/Akt-Rac1- JNK Pathways

Fibroblasts play a pivotal role in the process of cutaneous wound repair, whereas their migratory ability under diabetic conditions is markedly reduced. In this study, we investigated the effect of basic fibroblast growth factor (bFGF) on human dermal fibroblast migration in a high-glucose environment. bFGF significantly increased dermal fibroblast migration by increasing the percentage of fibroblasts with a high polarity index and reorganizing F-actin. A significant increase in intracellular reactive oxygen species (ROS) was observed in dermal fibroblasts under diabetic conditions following bFGF treatment. The blockage of bFGF-induced ROS production by either the ROS scavenger N-acetyl-L-cysteine (NAC) or the NADPH oxidase inhibitor diphenylene iodonium chloride (DPI) almost completely neutralized the increased migration rate of dermal fibroblasts promoted by bFGF. Akt, Rac1 and JNK were rapidly activated by bFGF in dermal fibroblasts, and bFGF-induced ROS production and promoted dermal fibroblast migration were significantly attenuated when suppressed respectively. In addition, bFGF-induced increase in ROS production was indispensable for the activation of focal adhesion kinase (FAK) and paxillin. Therefore, our data suggested that bFGF promotes the migration of human dermal fibroblasts under diabetic conditions through increased ROS production via the PI3K/Akt-Rac1-JNK pathways.

Reactive oxygen species in endothelial function - from disease to adaptation -

Endothelial function is largely dictated by its ability to rapidly sense environmental cues and adapt to these stimuli through changes in vascular tone, inflammation/immune recruitment, and angiogenesis. When any one of these abilities is compromised, the endothelium becomes dysfunctional, which ultimately leads to disease. Reactive oxygen species (ROS) have been established at the forefront of endothelial dysfunction; however, more careful examination has demonstrated that ROS are fundamental to each of the sensing/signaling roles of the endothelium. The purpose of this review is to document endothelial ROS production in both disease and physiological adaptation. Through understanding new endothelial signaling paradigms, we will gain insight into more targeted therapeutic strategies for vascular diseases.

AECHL-1, a novel triterpenoid, targets tumor neo-vasculature and impairs the endothelial cell cytoskeleton

Tumor angiogenesis is characterized by abnormal vessel morphology leading to erratic and insufficient delivery of chemotherapeutics and oxygen, making the tumor core not only highly hypoxic but also unresponsive toward treatment. Such hypoxic conditions promote tumor aggressiveness, leading to the establishment of metastatic disease. Most anti-angiogenic treatments aim toward the destruction of tumor vasculature, which proves countereffective by further increasing its aggressive nature. Hence, developing drugs which target or regulate these processes might lead to a better delivery of chemotherapeutics resulting in tumor shrinkage. Plant-derived natural compounds having a bioactive ingredient, especially triterpenoids, have been known to possess anticancer properties. AECHL-1, a recently isolated novel triterpenoid with proven anticancer potential, is seemingly noncytotoxic toward HEK 293 and HUVECs. Also, cytotoxicity was absent during in vivo studies involving intraperitoneal injections with 5 µg/kg body weight AECHL-1 on SCID mice. When used at subtoxic doses, it was found to be effective in suppression of neo-vessel formation as demonstrated in the chick chorioallantoic membrane, rat aortic rings, Matrigel plugs and xenograft tumors implanted in SCID mice. Tumor vasculature from AECHL-1-treated mice showed greater mural cell coverage and relatively normalized architecture. Investigations into the molecular mechanisms responsible for these observations revealed an effect on the actin cytoskeleton of stimulated HUVECs as well as the VEGFR2-mediated MAPK pathway. AECHL-1 could effectively distinguish between stimulated and nonstimulated endothelial cells. AECHL-1 could also downregulate HIF-1α expression and VEGF secretion under hypoxic conditions, thus reducing the fears of unnecessarily aggravating tumor metastasis as a result of anti-angiogenic therapy. Results obtained from the aforementioned studies make it clear that though AECHL-1 shows promise in discouraging and pruning neo-vasculature, it may not affect existing vasculature as the doses used for the assays are significantly lower than the ones causing endothelial cell death and has potential to be considered as a candidate for therapeutic drug development.

IQGAP1: insights into the function of a molecular puppeteer

The intracellular spatiotemporal organization of signaling events is critical for normal cellular function. In response to environmental stimuli, cells utilize highly organized signaling pathways that are subject to multiple layers of regulation. However, the molecular mechanisms that coordinate these complex processes remain an enigma. Scaffolding proteins (scaffolins) have emerged as critical regulators of signaling pathways, many of which have well-described functions in immune cells. IQGAP1, a highly conserved cytoplasmic scaffold protein, is able to curb, compartmentalize, and coordinate multiple signaling pathways in a variety of cell types. IQGAP1 plays a central role in cell-cell interaction, cell adherence, and movement via actin/tubulin-based cytoskeletal reorganization. Evidence also implicates IQGAP1 as an essential regulator of the MAPK and Wnt/β-catenin signaling pathways. Here, we summarize the recent advances on the cellular and molecular biology of IQGAP1. We also describe how this pleiotropic scaffolin acts as a true molecular puppeteer, and highlight the significance of future research regarding the role of IQGAP1 in immune cells.

The biology of IQGAP proteins: beyond the cytoskeleton

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, cardio-vascular 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.

Tyrosine phosphorylation of WW proteins

A number of key regulatory proteins contain one or two copies of the WW domain known to mediate protein-protein interaction via proline-rich motifs, such as PPxY. The Hippo pathway components take advantage of this module to transduce tumor suppressor signaling. It is becoming evident that tyrosine phosphorylation is a critical regulator of the WW proteins. Here, we review the current knowledge on the involved tyrosine kinases and their roles in regulating the WW proteins.

IQGAPs choreograph cellular signaling from the membrane to the nucleus

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.

Antioxidant and antiangiogenic properties of phenolic extract from Pleurotus tuber-regium

Pleurotus tuber-regium (Fries) Singer (PTR), both an edible and a medicinal mushroom also known as tiger milk mushroom, has experienced growing popularity and economic importance due to its flavor, nutritive value, and medicinal effects. In this study, the antioxidant and antiangiogenic activities of a 60% ethanol extract (EE) obtained from the sclerotium of PTR were investigated. Typical phenolic compounds including protocatechuic, chlorogenic, syringic, ferulic, and folic acid were identified and quantified in EE by the HPLC-UV-ESI/MS analyses. EE possessed strong antioxidant activity and could dose-dependently inhibit vascular endothelial growth factor (VEGF)-induced human umbilical vein endothelial cells (HUVEC) migration and tube formation. qPCR results showed that VEGF-induced FGF, ANG-Tie, and MMP gene expression as well as VEGFR were down-regulated at the mRNA level after treated with EE, suggesting that multiple molecular targets related to angiogenesis was involved. Furthermore, EE also inhibited the formation of subintestinal vessel plexus (SIVs) in zebrafish embryos in vivo. All of these suggested that EE of PTR could be the source of potential inhibitors to target angiogenesis.

Epidermal growth factor stimulates nuclear factor-κB activation and heme oxygenase-1 expression via c-Src, NADPH oxidase, PI3K, and Akt in human colon cancer cells

Previous report showed that epidermal growth factor (EGF) promotes tumor progression. Several studies demonstrated that growth factors can induce heme oxygenase (HO)-1 expression, protect against cellular injury and cancer cell proliferation. In this study, we investigated the involvement of the c-Src, NADPH oxidase, reactive oxygen species (ROS), PI3K/Akt, and NF-κB signaling pathways in EGF-induced HO-1 expression in human HT-29 colon cancer cells. Treatment of HT-29 cells with EGF caused HO-1 to be expressed in concentration- and time-dependent manners. Treatment of HT-29 cells with AG1478 (an EGF receptor (EGFR) inhibitor), small interfering RNA of EGFR (EGFR siRNA), a dominant negative mutant of c-Src (c-Src DN), DPI (an NADPH oxidase inhibitor), glutathione (an ROS inhibitor), LY294002 (a PI3K inhibitor), and an Akt DN inhibited EGF-induced HO-1 expression. Stimulation of cells with EGF caused an increase in c-Src phosphorylation at Tyr406 in a time-dependent manner. Treatment of HT-29 cells with EGF induced an increase in p47(phox) translocation from the cytosol to membranes. The EGF-induced ROS production was inhibited by DPI. Stimulation of cells with EGF resulted in an increase in Akt phosphorylation at Ser473, which was inhibited by c-Src DN, DPI, and LY 294002. Moreover, treatment of HT-29 cells with a dominant negative mutant of IκB (IκBαM) inhibited EGF-induced HO-1 expression. Stimulation of cells with EGF induced p65 translocation from the cytosol to nuclei. Treatment of HT-29 cells with EGF induced an increase in κB-luciferase activity, which was inhibited by a c-Src DN, LY 294002, and an Akt DN. Furthermore, EGF-induced colon cancer cell proliferation was inhibited by Sn(IV)protoporphyrin-IX (snPP, an HO-1 inhibitor). Taken together, these results suggest that the c-Src, NADPH oxidase, PI3K, and Akt signaling pathways play important roles in EGF-induced NF-κB activation and HO-1 expression in HT-29 cells. Moreover, overexpression of HO-1 mediates EGF-induced colon cancer cell proliferation.

Isolation of the lateral border recycling compartment using a diaminobenzidine-induced density shift

The migration of leukocytes across the endothelium and into tissue is critical to mounting an inflammatory response. The lateral border recycling compartment (LBRC), a complex vesicular-tubule invagination of the plasma membrane found at endothelial cell borders, plays an important role in this process. Although a few proteins have been shown to be present in the LBRC, no unique marker is known. Here, we detail methods that can be used to characterize a subcellular compartment that lacks an identifying marker. Initial characterization of the LBRC was performed using standard subcellular fractionation with sucrose gradients and took advantage of the observation that the compartment migrated at a lower density than other membrane compartments. To isolate larger quantities of the compartment, we modified a classic technique known as a diaminobenzidine (DAB)-induced density shift. The DAB-induced density shift allowed for specific isolation of membranes labeled with horseradish peroxidase-conjugated antibody. Because the LBRC could be differentially labeled at 4 °C and 37 °C, we were able to identify proteins that are enriched in the compartment, despite lacking a unique marker. These methods serve as a model to others studying poorly characterized compartments and organelles and are applicable to a wide variety of biological systems.

Role of small GTPase protein Rac1 in cardiovascular diseases: development of new selective pharmacological inhibitors

A pathway-based genome-wide association analysis has recently identified Rac1 as one of the biologically important gene in coronary heart diseases. The role of the small GTPase Rac1 in cardiac hypertrophy and atherosclerosis has also been documented in clinical studies with the HMG-CoA reductase inhibitors and in in vitro and in vivo settings using transgenic and knockout mice. Thus, Rac1 has emerged as a new pharmacological target for the treatment of cardiovascular diseases. The activation state of Rac1 depends on the release of guanosine diphosphate and the binding of guanosine triphosphate. This cycling is regulated by the guanine nucleotide exchange factors, as activators, and by the GTPase-activating proteins. Three categories of selective Rac1 inhibitors have been developed affecting different steps of this pathway: antagonists of Rac1-guanine nucleotide exchange factor interaction, allosteric inhibitors of nucleotide binding to Rac1, and antagonists of Rac1-mediated NADPH oxidase activity. These chemical compounds have shown to selectively inhibit Rac1 activation in cultured cell lines without affecting the homologous proteins RhoA and Cdc42. Moreover, pioneer studies have been conducted with Rac1 inhibitors in in vivo experimental models of cardiovascular diseases with encouraging results. The present review summarizes the current knowledge of the role of Rac1 in cardiovascular diseases and the pharmacological approaches that have been developed to selectively inhibit its function.

Factor Xa in mouse fibroblasts may induce fibrosis more than thrombin

Coagulation factors are known to play a role in wound healing by stimulating fibroblasts and might be associated with tissue fibrosis, however, only limited data exist. Protease-activated receptor 1 (PAR1), activated by thrombin or factor (F) Xa, and PAR2, activated by FXa, have recently been reported to play roles not only in the coagulation system, but also in cardiac fibrosis. Furthermore, a previous report found that FX deficiency in mice led to the development of cardiac fibrosis. Therefore, in the present study, we evaluated cellular biological function under conditions of overexpressed thrombin and FXa in fibroblasts.Cell migration and proliferation with FXa (1U/mL) and thrombin (1U/mL) stimulation were evaluated. Cells incubated without FXa or thrombin were used as control. H2O2 and TGF-β1 production were measured using ELISA. Signal pathways were evaluated using a signal pathway reporter assay.Cell migration and proliferation were increased in FXa-stimulated cells (4.1-fold increase for migration, 1.3-fold for proliferation compared with control, respectively) and thrombin (4.1-fold increase for migration, 1.3-fold for proliferation as compared to control, respectively). H2O2 production was higher in FXa-stimulated cells compared to thrombin (1.3-fold increase) and control cells (1.4-fold increased). TGF-β1 production was up-regulated after FXa addition (12.6-fold increase compared with thrombin, 1.8-fold increase compared with control, respectively). In FXa-stimulated cells, AP-1 and NF-kB were increased compared to control (P < 0.05).These data suggest that FXa and thrombin play important roles in the fibrotic process that could also lead to cardiac fibrosis, and that at least some of these signalings are more accelerated with FXa compared to thrombin.

A novel role for IQGAP1 protein in cell motility through cell retraction

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.

IQGAP1 binds to estrogen receptor-α and modulates its function

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 ERα and IQGAP1 contribute to breast cancer. In this study, we report that IQGAP1 binds ERα and ERβ. In vitro analysis with pure proteins revealed a direct interaction between IQGAP1 and ERα. Investigation with multiple short fragments of each protein showed that ERα binds to the IQ domain of IQGAP1, whereas the hinge region of ERα is responsible for binding IQGAP1. In addition, IQGAP1 and ERα 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 ERα and modulates its transcriptional function, suggesting that IQGAP1 might be a target for therapy in patients with breast carcinoma.

Increases in reactive oxygen species enhance vascular endothelial cell migration through a mechanism dependent on the transient receptor potential melastatin 4 ion channel

A hallmark of severe inflammation is reactive oxygen species (ROS) overproduction induced by increased inflammatory mediators secretion. During systemic inflammation, inflammation mediators circulating in the bloodstream interact with endothelial cells (ECs) raising intracellular oxidative stress at the endothelial monolayer. Oxidative stress mediates several pathological functions, including an exacerbated EC migration. Because cell migration critically depends on calcium channel-mediated Ca(2+) influx, the molecular identification of the calcium channel involved in oxidative stress-modulated EC migration has been the subject of intense investigation. The transient receptor potential melastatin 4 (TRPM4) protein is a ROS-modulated non-selective cationic channel that performs several cell functions, including regulating intracellular Ca(2+) overload and Ca(2+) oscillation. This channel is expressed in multiple tissues, including ECs, and contributes to the migration of certain immune cells. However, whether the TRPM4 ion channel participates in oxidative stress-mediated EC migration is not known. Herein, we investigate whether oxidative stress initiates or enhances EC migration and study the role played by the ROS-modulated TRPM4 ion channel in oxidative stress-mediated EC migration. We demonstrate that oxidative stress enhances, but does not initiate, EC migration in a dose-dependent manner. Notably, we demonstrate that the TRPM4 ion channel is critical in promoting H2O2-enhanced EC migration. These results show that TRPM4 is a novel pharmacological target for the possible treatment of severe inflammation and other oxidative stress-mediated inflammatory diseases.

The Ras GTPase-activating-like protein IQGAP1 is downregulated in human diabetic nephropathy and associated with ERK1/2 pathway activation

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.

Wnt signaling proteins associate with the nuclear pore complex: implications for cancer

Several components of the Wnt signaling pathway have in recent years been linked to the nuclear pore complex. β-catenin, the primary transducer of Wnt signals from the plasma membrane to the nucleus, has been shown to transiently associate with different FG-repeat containing nucleoporins (Nups) and to translocate bidirectionally through pores of the nuclear envelope in a manner independent of classical transport receptors and the Ran GTPase. Two key regulators of β-catenin, IQGAP1 and APC, have also been reported to bind specific Nups or to locate at the nuclear pore complex. The interaction between these Wnt signaling proteins and different Nups may have functional implications beyond nuclear transport in cellular processes that include mitotic regulation, centrosome positioning and cell migration, nuclear envelope assembly/disassembly, and the DNA replication checkpoint. The broad implications of interactions between Wnt signaling proteins and Nups will be discussed in the context of cancer.

Cellular polarity in aging: role of redox regulation and nutrition

Cellular polarity concerns the spatial asymmetric organization of cellular components and structures. Such organization is important not only for biological behavior at the individual cell level, but also for the 3D organization of tissues and organs in living organisms. Processes like cell migration and motility, asymmetric inheritance, and spatial organization of daughter cells in tissues are all dependent of cell polarity. Many of these processes are compromised during aging and cellular senescence. For example, permeability epithelium barriers are leakier during aging; elderly people have impaired vascular function and increased frequency of cancer, and asymmetrical inheritance is compromised in senescent cells, including stem cells. Here, we review the cellular regulation of polarity, as well as the signaling mechanisms and respective redox regulation of the pathways involved in defining cellular polarity. Emphasis will be put on the role of cytoskeleton and the AMP-activated protein kinase pathway. We also discuss how nutrients can affect polarity-dependent processes, both by direct exposure of the gastrointestinal epithelium to nutrients and by indirect effects elicited by the metabolism of nutrients, such as activation of antioxidant response and phase-II detoxification enzymes through the transcription factor nuclear factor (erythroid-derived 2)-like 2 (Nrf2). In summary, cellular polarity emerges as a key process whose redox deregulation is hypothesized to have a central role in aging and cellular senescence.

Oxidative stress in angiogenesis and vascular disease

Despite the damaging effect on tissues at a high concentration, it has been gradually established that oxidative stress plays a positive role during angiogenesis. In adults, physiological or pathological angiogenesis is initiated by tissue demands for oxygen and nutrients, resulting in a hypoxia/reoxygenation cycle, which, in turn promotes the formation of reactive oxygen species (ROS). The ROS can be generated either endogenously, through mitochondrial electron transport chain reactions and nicotinamide adenine dinucleotide phosphate oxidase, or exogenously, resulting from exposure to environmental agents, such as ultraviolet or ionizing radiation. In many conditions, ROS promotes angiogenesis, either directly or via the generation of active oxidation products, including peroxidized lipids. The latter lipid metabolites are generated in excess during atherosclerosis, thereby linking atherogenic processes and pathological angiogenesis. Although the main mechanism of oxidative stress-induced angiogenesis involves hypoxia-inducible factor/vascular endothelial growth factor (VEGF) signaling, recent studies have identified several pathways that are VEGF-independent. This review aims to provide a summary of the past and present views on the role of oxidative stress as a mediator and modulator of angiogenesis, and to highlight newly identified mechanisms.

Structure and function of IQ-domain GTPase-activating protein 1 and its association with tumor progression (Review)

IQ-domain GTPase-activating proteins (IQGAPs) are evolutionary conserved multidomain proteins that are found in numerous organisms, from yeast to mammals. To date, three IQGAP proteins have been identified in humans, of which IQGAP1 is the best characterized. As a scaffold protein, IQGAP1 contains multiple protein-interacting domains, which modulate binding to target proteins. Recent mounting studies demonstrated a role for IQGAP1 in tumor progression, supported by the altered expression and subcellular distribution of IQGAP1 in tumors. The contribution of IQGAP1 to tumor progression appears to involve a complex interplay of cell functions by integrating diverse signal transduction pathways and coordinating activities, such as cell adhesion, migration, invasion, proliferation and angiogenesis.

IQGAP1 interactome analysis by in vitro reconstitution and live cell 3-color FRET microscopy

IQGAP1 stimulates branched actin filament nucleation by activating N-WASP, which then activates the Arp2/3 complex. N-WASP can be activated by other factors, including GTP-bound Cdc42 or Rac1, which also bind IQGAP1. Here we report the use of purified proteins for in vitro binding and actin polymerization assays, and Förster (or fluorescence) resonance energy transfer (FRET) microscopy of cultured cells to illuminate functional interactions among IQGAP1, N-WASP, actin, and either Cdc42 or Rac1. In pyrene-actin assembly assays containing N-WASP and Arp2/3 complex, IQGAP1 plus either small G protein cooperatively stimulated actin filament nucleation by reducing the lag time before 50% maximum actin polymerization was reached. Similarly, Cdc42 and Rac1 modulated the binding of IQGAP1 to N-WASP in a dose-dependent manner, with Cdc42 enhancing the interaction and Rac1 reducing the interaction. These in vitro reconstitution results suggested that IQGAP1 interacts by similar, yet distinct mechanisms with Cdc42 versus Rac1 to regulate actin filament assembly through N-WASP in vivo. The physiological relevance of these multi-protein interactions was substantiated by 3-color FRET microscopy of live MDCK cells expressing various combinations of fluorescent N-WASP, IQGAP1, Cdc42, Rac1, and actin. This study also establishes 3-color FRET microscopy as a powerful tool for studying dynamic intermolecular interactions in live cells.

A genome-wide association study of chronic otitis media with effusion and recurrent otitis media identifies a novel susceptibility locus on chromosome 2

Chronic otitis media with effusion (COME) and recurrent otitis media (ROM) have been shown to be heritable, but candidate gene and linkage studies to date have been equivocal. Our aim was to identify genetic susceptibility factors using a genome-wide association study (GWAS). We genotyped 602 subjects from 143 families with 373 COME/ROM subjects using the Illumina Human CNV370-Duo DNA Bead Chip (324,748 SNPs). We carried out the GWAS scan and imputed SNPs at the regions with the most significant associations. Replication genotyping in an independent family-based sample was conducted for 53 SNPs: the 41 most significant SNPs with P < 10(-4) and 12 imputed SNPs with P < 10(-4) on chromosome 15 (near the strongest signal). We replicated the association of rs10497394 (GWAS discovery P = 1.30 × 10(-5)) on chromosome 2 in the independent otitis media population (P = 4.7 × 10(-5); meta-analysis P = 1.52 × 10(-8)). Three additional SNPs had replication P values < 0.10. Two were on chromosome 15q26.1 including rs1110060, the strongest association with COME/ROM in the primary GWAS (P = 3.4 ×10(-7)) in KIF7 intron 7 (P = 0.072), and rs10775247, a non-synonymous SNP in TICRR exon 2 (P = 0.075). The third SNP rs386057 was on chromosome 5 in TPPP intron 1 (P = 0.045). We have performed the first GWAS of COME/ROM and have identified a SNP rs10497394 on chromosome 2 is significantly associated with COME/ROM susceptibility. This SNP is within a 537 kb intergenic region, bordered by CDCA7 and SP3. The genomic and functional significance of this newly identified locus in COME/ROM pathogenesis requires additional investigation.

17β-estradiol enhances signalling mediated by VEGF-A-delta-like ligand 4-notch1 axis in human endothelial cells

Estrogens play a protective role in coronary artery disease. The mechanisms of action are still poorly understood, although a role for estrogens in stimulation of angiogenesis has been suggested. In several cell types, estrogens modulate the Notch pathway, which is involved in controlling angiogenesis downstream of vascular endothelial growth factor A (VEGF-A). The goal of our study was to establish whether estrogens modulate Notch activity in endothelial cells and the possible consequences on angiogenesis. Human umbilical vein endothelial cells (HUVECs) were treated with 17β-estradiol (E2) and the effects on Notch signalling were evaluated. E2 increased Notch1 processing as indicated by i) decreased levels of Notch1 transmembrane subunit ii) increased amount of Notch1 in nuclei iii) unaffected level of mRNA. Similarly, E2 increased the levels of the active form of Notch4 without altering Notch4 mRNA. Conversely, protein and mRNA levels of Notch2 were both reduced suggesting transcriptional repression of Notch2 by E2. Under conditions where Notch was activated by upregulation of Delta-like ligand 4 (Dll4) following VEGF-A treatment, E2 caused a further increase of the active form of Notch1, of the number of cells with nuclear Notch1 and of Hey2 mRNA. Estrogen receptor antagonist ICI 182.780 antagonized these effects suggesting that E2 modulation of Notch1 is mediated by estrogen receptors. E2 treatment abolished the increase in endothelial cells sprouting caused by Notch inhibition in a tube formation assay on 3D Matrigel and in mouse aortic ring explants. In conclusion, E2 affects several Notch pathway components in HUVECs, leading to an activation of the VEGF-A-Dll4-Notch1 axis and to a modulation of vascular branching when Notch signalling is inhibited. These results contribute to our understanding of the molecular mechanisms of cardiovascular protection exerted by estrogens by uncovering a novel role of E2 in the Notch signalling-mediated modulation of angiogenesis.

Current status of NADPH oxidase research in cardiovascular pharmacology

The implications of reactive oxygen species in cardiovascular disease have been known for some decades. Rationally, therapeutic antioxidant strategies combating oxidative stress have been developed, but the results of clinical trials have not been as good as expected. Therefore, to move forward in the design of new therapeutic strategies for cardiovascular disease based on prevention of production of reactive oxygen species, steps must be taken on two fronts, ie, comprehension of reduction-oxidation signaling pathways and the pathophysiologic roles of reactive oxygen species, and development of new, less toxic, and more selective nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitors, to clarify both the role of each NADPH oxidase isoform and their utility in clinical practice. In this review, we analyze the value of NADPH oxidase as a therapeutic target for cardiovascular disease and the old and new pharmacologic agents or strategies to prevent NADPH oxidase activity. Some inhibitors and different direct or indirect approaches are available. Regarding direct NADPH oxidase inhibition, the specificity of NADPH oxidase is the focus of current investigations, whereas the chemical structure-activity relationship studies of known inhibitors have provided pharmacophore models with which to search for new molecules. From a general point of view, small-molecule inhibitors are preferred because of their hydrosolubility and oral bioavailability. However, other possibilities are not closed, with peptide inhibitors or monoclonal antibodies against NADPH oxidase isoforms continuing to be under investigation as well as the ongoing search for naturally occurring compounds. Likewise, some different approaches include inhibition of assembly of the NADPH oxidase complex, subcellular translocation, post-transductional modifications, calcium entry/release, electron transfer, and genetic expression. High-throughput screens for any of these activities could provide new inhibitors. All this knowledge and the research presently underway will likely result in development of new drugs for inhibition of NADPH oxidase and application of therapeutic approaches based on their action, for the treatment of cardiovascular disease in the next few years.

A labile pool of IQGAP1 disassembles endothelial adherens junctions

Adhesion molecules are known to play an important role in endothelial activation and angiogenesis. Here we determined the functional role of IQGAP1 in the regulation of endothelial adherens junctions. VE-cadherin is found to be associated with actin filaments and thus stable, but IQGAP1 at intercellular junctions is not bound to actin filaments and thus labile. Expression of GFP labeled VE-α-catenin is shown to increase the electrical resistance across HUVEC monolayers and diminishes endogenous labile IQGAP1 at the intercellular junctions. Knockdown of endogenous IQGAP1 enhances intercellular adhesion in HUVECs by increasing the association of VE-cadherin with P120 and β-catenin. IQGAP1 knockdown also decreases the interaction of N-cadherin with P120 and β-catenin. Together, these results suggest that a labile pool of IQGAP1 at intercellular junctions disassembles adherens junctions and thus impairs endothelial cell-cell adhesion.

The Ras GTPase-activating-like protein IQGAP1 mediates Nrf2 protein activation via the mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) kinase (MEK)-ERK pathway

Nrf2 plays a critical role in the regulation of cellular oxidative stress. MEK-ERK activation has been shown to be one of the major pathways resulting in the activation of Nrf2 and induction of Nrf2 downstream targets, including phase II detoxifying/antioxidant genes in response to oxidative stress and xenobiotics. In this study, IQGAP1 (IQ motif-containing GTPase-activating protein 1), a new Nrf2 interaction partner that we have published previously, was found to modulate MEK-ERK-mediated Nrf2 activation and induction of phase II detoxifying/antioxidant genes. Nrf2 binds directly to the IQ domain (amino acids 699-905) of IQGAP1. Knockdown of IQGAP1 significantly attenuated phenethyl isothiocyanate- or MEK-mediated activation of the MEK-ERK-Nrf2 pathway. Knockdown of IQGAP1 also attenuated MEK-mediated increased stability of Nrf2, which in turn was associated with a decrease in the nuclear translocation of Nrf2 and a decrease in the expression of phase II detoxifying/antioxidant genes. In the aggregate, these results suggest that IQGAP1 may play an important role in the MEK-ERK-Nrf2 signaling pathway.

Targeting the therapeutic effects of exercise on redox-sensitive mechanisms in the vascular endothelium during tumor progression

The American Cancer Society estimated 1.5 million new cancer cases in the United States in 2012. Although the exact number is not known, it is estimated that brain metastases occur in 20-40% of cancer patients (39). Owing to the complexity of development and the variation in tumor etiology, therapy options have been limited for a number of cancers, whereas progressive treatments have been successful for some malignancies. Combining treatment strategies has shown potential to increase positive outcomes; however, cancer remains a formidable diagnosis with no true cure. Many researchers have focused on alternative forms of cancer prevention or treatment to slow cancer progression. Studies have shown that with moderate, regular exercise signaling pathways associated with increased antioxidant activity and cellular repair are upregulated in vascular tissue; however, the physiological mechanisms are poorly understood. The purpose of this review is to examine the current literature to better understand the impact of exercise on cancer progression and tumor metastasis and discuss potential redox-related signaling in the vasculature that may be involved.

IQGAP1 links PDGF receptor-β signal to focal adhesions involved in vascular smooth muscle cell migration: role in neointimal formation after vascular injury

Platelet-derived growth factor (PDGF) stimulates vascular smooth muscle cell (VSMC) migration and neointimal formation in response to injury. We previously identified IQ-domain GTPase-activating protein 1 (IQGAP1) as a novel VEGF receptor 2 binding scaffold protein involved in endothelial migration. However, its role in VSMC migration and neointimal formation in vivo is unknown. Here we show that PDGF stimulation rapidly promotes IQGAP1 association with PDGF receptor-β (PDGFR) as well as IQGAP1 tyrosine phosphorylation in cultured VSMC. Overexpression or knockdown of IQGAP1 enhances or inhibits PDGFR autophosphorylation (p-PDGFR), respectively. Immunofluorescence and cell fractionation analysis reveals that PDGF-induced p-PDGFR localized in focal adhesions (FAs), but not caveolae/lipid rafts, is inhibited by IQGAP1 knockdown with siRNA. PDGF stimulation promotes IQGAP1 association with PDGFR/FA signaling protein complex. Functionally, IQGAP1 siRNA inhibits PDGF-induced FA formation as well as VSMC migration induced by PDGF. In vivo, IQGAP1 expression is markedly increased at neointimal VSMC in wire-injured femoral arteries. Mice lacking IQGAP1 exhibit impaired neointimal formation in response to vascular injury. In summary, IQGAP1, through interaction with PDGFR and FA signaling proteins, promotes activation of PDGFR in FAs as well as FA formation, which may contribute to VSMC migration and neointimal formation after injury. Our findings provide insight into IQGAP1 as a potential therapeutic target for vascular migration-related diseases.

Redox regulation of protein kinases

Protein kinases represent one of the largest families of genes found in eukaryotes. Kinases mediate distinct cellular processes ranging from proliferation, differentiation, survival, and apoptosis. Ligand-mediated activation of receptor kinases can lead to the production of endogenous hydrogen peroxide (H₂O₂) by membrane-bound NADPH oxidases. In turn, H₂O₂ can be utilized as a secondary messenger in signal transduction pathways. This review presents an overview of the molecular mechanisms involved in redox regulation of protein kinases and its effects on signaling cascades. In the first half, we will focus primarily on receptor tyrosine kinases (RTKs), whereas the latter will concentrate on downstream non-receptor kinases involved in relaying stimulant response. Select examples from the literature are used to highlight the functional role of H₂O₂ regarding kinase activity, as well as the components involved in H₂O₂ production and regulation during cellular signaling. In addition, studies demonstrating direct modulation of protein kinases by H₂O₂ through cysteine oxidation will be emphasized. Identification of these redox-sensitive residues may help uncover signaling mechanisms conserved within kinase subfamilies. In some cases, these residues can even be exploited as targets for the development of new therapeutics. Continued efforts in this field will further basic understanding of kinase redox regulation, and delineate the mechanisms involved in physiological and pathological H₂O₂ responses.

IQGAP1 suppresses TβRII-mediated myofibroblastic activation and metastatic growth in liver

In the tumor microenvironment, TGF-β induces transdifferentiation of quiescent pericytes and related stromal cells into myofibroblasts that promote tumor growth and metastasis. The mechanisms governing myofibroblastic activation remain poorly understood, and its role in the tumor microenvironment has not been explored. Here, we demonstrate that IQ motif containing GTPase activating protein 1 (IQGAP1) binds to TGF-β receptor II (TβRII) and suppresses TβRII-mediated signaling in pericytes to prevent myofibroblastic differentiation in the tumor microenvironment. We found that TGF-β1 recruited IQGAP1 to TβRII in hepatic stellate cells (HSCs), the resident liver pericytes. Iqgap1 knockdown inhibited the targeting of the E3 ubiquitin ligase SMAD ubiquitination regulatory factor 1 (SMURF1) to the plasma membrane and TβRII ubiquitination and degradation. Thus, Iqgap1 knockdown stabilized TβRII and potentiated TGF-β1 transdifferentiation of pericytes into myofibroblasts in vitro. Iqgap1 deficiency in HSCs promoted myofibroblast activation, tumor implantation, and metastatic growth in mice via upregulation of paracrine signaling molecules. Additionally, we found that IQGAP1 expression was downregulated in myofibroblasts associated with human colorectal liver metastases. Taken together, our studies demonstrate that IQGAP1 in the tumor microenvironment suppresses TβRII and TGF-β dependent myofibroblastic differentiation to constrain tumor growth.

Reactive oxygen species and tumor metastasis

The migration and invasion of cancer cells are the first steps in metastasis. Through a series of cellular responses, including cytoskeletal reorganization and degradation of the extracellular matrix, cancer cells are able to separate from the primary tumor and metastasize to distant locations in the body. In cancer cells, reactive oxygen species (ROS) play important roles in the migration and invasion of cells. Stimulation of cell surface receptors with growth factors and integrin assembly generates ROS, which relay signals from the cell surface to important signaling proteins. ROS then act within cells to promote migration and invasion. In this review, we collect recent evidence pointing towards the involvement of ROS in tumor metastasis and discuss the roles of ROS at different stages during the process of cancer cell migration, invasion and epithelial-mesenchymal transition.

Novel role of copper transport protein antioxidant-1 in neointimal formation after vascular injury

OBJECTIVE

Vascular smooth muscle cell (VSMC) migration is critically important for neointimal formation after vascular injury and atherosclerosis lesion formation. Copper (Cu) chelator inhibits neointimal formation, and we previously demonstrated that Cu transport protein antioxidant-1 (Atox1) is involved in Cu-induced cell growth. However, role of Atox1 in VSMC migration and neointimal formation after vascular injury is unknown.

APPROACH AND RESULTS

Here, we show that Atox1 expression is upregulated in injured vessel, and it is colocalized with the Cu transporter ATP7A, one of the downstream targets of Atox1, mainly in neointimal VSMCs at day 14 after wire injury. Atox1(-/-) mice show inhibition of neointimal formation and extracellular matrix expansion, which is associated with a decreased VSMCs accumulation within neointima and lysyl oxidase activity. Mechanistically, in cultured VSMC, Atox1 depletion with siRNA inhibits platelet-derived growth factor-induced Cu-dependent VSMC migration by preventing translocation of ATP7A and small G protein Rac1 to the leading edge, as well as Cu- and Rac1-dependent lamellipodia formation. Furthermore, Atox1(-/-) mice show decreased perivascular macrophage infiltration in wire-injured vessels, as well as thioglycollate-induced peritoneal macrophage recruitment.

CONCLUSIONS

Atox1 is involved in neointimal formation after vascular injury through promoting VSMC migration and inflammatory cell recruitment in injured vessels. Thus, Atox1 is a potential therapeutic target for VSMC migration and inflammation-related vascular diseases.

Reactive oxygen species in vascular formation and development

Reactive oxygen species (ROS) are derived from the metabolism of oxygen and are traditionally viewed as toxic byproducts that cause damage to biomolecules. It is now becoming widely acknowledged that ROS are key modulators in a variety of biological processes and pathological states. ROS mediate key signaling transduction pathways by reversible oxidation of certain signaling components and are involved in the signaling of growth factors, G-protein-coupled receptors, Notch, and Wnt and its downstream cascades including MAPK, JAK-STAT, NF-κB, and PI3K/AKT. Vascular formation and development is one of the most important events during embryogenesis and is vital for postnasal tissue repair. In this paper, we will discuss how ROS regulate different steps in vascular development, including smooth muscle cell differentiation, angiogenesis, endothelial progenitor cells recruitment, and vascular cell migration.

Nox4- and Nox2-dependent oxidant production is required for VEGF-induced SERCA cysteine-674 S-glutathiolation and endothelial cell migration

Endothelial cell (EC) migration in response to vascular endothelial growth factor (VEGF) is a critical step in both physiological and pathological angiogenesis. Although VEGF signaling has been extensively studied, the mechanisms by which VEGF-dependent reactive oxygen species (ROS) production affects EC signaling are not well understood. The aim of this study was to elucidate the involvement of Nox2- and Nox4-dependent ROS in VEGF-mediated EC Ca(2+) regulation and migration. VEGF induced migration of human aortic ECs into a scratch wound over 6 h, which was inhibited by overexpression of either catalase or superoxide dismutase (SOD). EC stimulation by micromolar concentrations of H2O2 was inhibited by catalase, but also unexpectedly by SOD. Both VEGF and H2O2 increased S-glutathiolation of SERCA2b and increased Ca(2+) influx into EC, and these events could be blocked by overexpression of catalase or overexpression of SERCA2b in which the reactive cysteine-674 was mutated to a serine. In determining the source of VEGF-mediated ROS production, our studies show that specific knockdown of either Nox2 or Nox4 inhibited VEGF-induced S-glutathiolation of SERCA, Ca(2+) influx, and EC migration. Treatment with H2O2 induced S-glutathiolation of SERCA and EC Ca(2+) influx, overcoming the knockdown of Nox4, but not Nox2, and Amplex red measurements indicated that Nox4 is the source of H2O2. These results demonstrate that VEGF stimulates EC migration through increased S-glutathiolation of SERCA and Ca(2+) influx in a Nox4- and H2O2-dependent manner, requiring Nox2 downstream.

Modification of smoke toxicant yields alters the effects of cigarette smoke extracts on endothelial migration: an in vitro study using a cardiovascular disease model

Endothelial damage plays a key role in atherosclerosis and this is impacted upon by numerous risk factors including cigarette smoking. A potential measure to reduce the cardiovascular burden associated with smoking is to reduce smoke toxicant exposure. In an in vitro endothelial damage repair assay, endothelial cell migration was inhibited by cigarette smoke particulate matter (PM) generated from several cigarette types. This inhibition was reduced when cells were exposed to PM from an experimental cigarette with reduced smoke toxicant levels. As a number of toxicants induce oxidative stress and since oxidative stress may link cigarette smoke and endothelial damage, we hypothesized that PM effects were dependent on elevated cellular oxidants. However, although PM-induced cellular oxidant production could be inhibited by ascorbic acid or n-acetylcysteine, both these antioxidants were without effect on migration responses to PM. Furthermore, reactive oxygen species production, as indicated by dihydroethidium fluorescence, was not different in cells exposed to smoke from cigarettes with different toxicant levels. In summary, our data demonstrate that a cardiovascular disease-related biological response may be modified when cells are exposed to smoke containing different levels of toxicants. This appeared independent of the induction of oxidative stress.

The scaffolding protein IQGAP1 co-localizes with actin at the cytoplasmic face of the nuclear envelope: implications for cytoskeletal regulation

IQGAP1 is an important cytoskeletal regulator, known to act at the plasma membrane to bundle and cap actin filaments, and to tether the cortical actin meshwork to microtubules via plus-end binding proteins. Here we describe the novel subcellular localization of IQGAP1 at the cytoplasmic face of the nuclear envelope, where it co-located with F-actin. The IQGAP1 and F-actin staining overlapped that of microtubules at the nuclear envelope, revealing a pattern strikingly similar to that observed at the plasma membrane. In detergent-extracted cells IQGAP1 was retained at cytoskeletal structures at the nuclear envelope. This finding has new implications for involvement of IQGAP1 in cell polarization and migration events and potentially in cell cycle-associated nuclear envelope assembly/disassembly.

NADPH oxidases as regulators of tumor angiogenesis: current and emerging concepts

SIGNIFICANCE

Reactive oxygen species (ROS) such as superoxide, hydrogen peroxide, and peroxynitrite are generated ubiquitously by all mammalian cells and have been understood for many decades as inflicting cell damage and as causing cancer by oxidation and nitration of macromolecules, including DNA, RNA, proteins, and lipids.

RECENT ADVANCES

A current concept suggests that ROS can also promote cell signaling pathways triggered by growth factors and transcription factors that ultimately regulate cell proliferation, differentiation, and apoptosis, all of which are important hallmarks of tumor cell proliferation and angiogenesis. Moreover, an emerging concept indicates that ROS regulate the functions of immune cells that infiltrate the tumor environment and stimulate angiogenesis, such as macrophages and specific regulatory T cells.

CRITICAL ISSUES

In this article, we highlight that the NADPH oxidase family of ROS-generating enzymes are the key sources of ROS and, thus, play an important role in redox signaling within tumor, endothelial, and immune cells thereby promoting tumor angiogenesis.

FUTURE DIRECTIONS

Knowledge of these intricate ROS signaling pathways and identification of the culprit NADPH oxidases is likely to reveal novel therapeutic opportunities to prevent angiogenesis that occurs during cancer and which is responsible for the revascularization after current antiangiogenic treatment.

IQGAP1 interacts with components of the slit diaphragm complex in podocytes and is involved in podocyte migration and permeability in vitro

IQGAP1 is a scaffold protein that interacts with proteins of the cytoskeleton and the intercellular adhesion complex. In podocytes, IQGAP1 is associated with nephrin in the glomerular slit diaphragm (SD) complex, but its role remains ill-defined. In this work, we investigated the interaction of IQGAP1 with the cytoskeleton and SD proteins in podocytes in culture, and its role in podocyte migration and permeability. Expression, localization, and interactions between IQGAP1 and SD or cytoskeletal proteins were determined in cultured human podocytes by Western blot (WB), immunocytolocalization (IC), immunoprecipitation (IP), and In situ Proximity Ligation assay (IsPL). Involvement of IQGAP1 in migration and permeability was also assessed. IQGAP1 expression in normal kidney biopsies was studied by immunohistochemistry. IQGAP1 expression by podocytes increased during their in vitro differentiation. IC, IP, and IsPL experiments showed colocalizations and/or interactions between IQGAP1 and SD proteins (nephrin, MAGI-1, CD2AP, NCK 1/2, podocin), podocalyxin, and cytoskeletal proteins (α-actinin-4). IQGAP1 silencing decreased podocyte migration and increased the permeability of a podocyte layer. Immunohistochemistry on normal human kidney confirmed IQGAP1 expression in podocytes and distal tubular epithelial cells and also showed an expression in glomerular parietal epithelial cells. In summary, our results suggest that IQGAP1, through its interaction with components of SD and cytoskeletal proteins, is involved in podocyte barrier properties.