Arsenic sulfide inhibits the progression of gastric cancer through regulating the circRNA_ASAP2/Wnt/β-catenin pathway

In our paper, the effects of As4S4 treatments on the growth and migration of gastric cancer (GC) cells were explored, and the potential underlying molecular mechanisms were also identified. Cell viability was evaluated by cell counting kit 8 assay. The expression of Ki-67 was examined using immunofluorescence staining. Cell apoptosis was assessed by flow cytometry. The migratory and invasion abilities of cells were determined using Transwell assay. The mRNA and protein levels of related gene were examined by RT-qPCR and western blotting, respectively. CircRNAs chip was performed to identify the differentiated expression of circRNAs in GC cells following the treatment with As4S4. Our results revealed that the proliferation, migration and invasion of GC cells were remarkably suppressed by the treatment with As4S4, while cell apoptosis was promoted. Furthermore, circRNA_ASAP2 was a novel target of As4S4 in GC, and it is involved in As4S4-modulated biological behavior alterations in GC cells. In addition, the activities of the Wnt/β-catenin signaling in GC cells were affected by the overexpression circRNA_ASAP2 and the treatment with As4S4. Moreover, the behavior changes in GC cells caused by the knockdown of circRNA_ASAP2 were reversed by the treatment with Wnt agonist SKL2001. In summary, As4S4 could function as an antitumor agent in GC through regulating the circRNA_ASAP2/Wnt/β-catenin pathway, which in turn influences the growth and metastasis of GC cells.

Recombinant Slit2 attenuates neuronal apoptosis via the Robo1-srGAP1 pathway in a rat model of neonatal HIE

Apoptosis following hypoxic-ischemic injury to the brain plays a major role in neuronal cell death. The neonatal brain is more susceptible to injury as the cortical neurons are immature and there are lower levels of antioxidants. Slit2, an extracellular matrix protein, has been shown to be neuroprotective in various models of neurological diseases. However, there is no information about the role of Slit2 in neonatal hypoxia-ischemia. In this study, we evaluated the effect of Slit2 and its receptor Robo1 in a rat model with neonatal HIE. 10-day old rat pups were used to create the neonatal HIE model. The right common carotid artery was ligated followed by 2.5 h of hypoxia. Recombinant Slit2 was administered intranasally 1 h post HI, recombinant Robo1 was used as a decoy receptor and administered intranasally 1h before HI and srGAP1-siRNA was administered intracerebroventricularly 24 h before HI. Brain infarct area measurement, short-term and long-term neurological function tests, Western blot, immunofluorescence staining, Fluoro-Jade C staining, Nissl staining and TUNEL staining were the assessments done following drug administration. Recombinant Slit2 administration reduced neuronal apoptosis and neurological deficits after neonatal HIE which were reversed by co-administration of recombinant Robo1 and srGAP1-siRNA administration. Recombinant Slit2 showed improved outcomes possibly via the robo1-srGAP1 pathway which mediated the inhibition of RhoA. In this study, the results suggest that Slit2 may help in attenuation of apoptosis and could be a therapeutic agent for treatment of neonatal hypoxic ischemic encephalopathy.

RPEL-family rhoGAPs link Rac/Cdc42 GTP loading to G-actin availability

RPEL proteins, which contain the G-actin-binding RPEL motif, coordinate cytoskeletal processes with actin dynamics. We show that the ArhGAP12- and ArhGAP32-family GTPase-activating proteins (GAPs) are RPEL proteins. We determine the structure of the ArhGAP12/G-actin complex, and show that G-actin contacts the RPEL motif and GAP domain sequences. G-actin inhibits ArhGAP12 GAP activity, and this requires the G-actin contacts identified in the structure. In B16 melanoma cells, ArhGAP12 suppresses basal Rac and Cdc42 activity, F-actin assembly, invadopodia formation and experimental metastasis. In this setting, ArhGAP12 mutants defective for G-actin binding exhibit more effective downregulation of Rac GTP loading following HGF stimulation and enhanced inhibition of Rac-dependent processes, including invadopodia formation. Potentiation or disruption of the G-actin/ArhGAP12 interaction, by treatment with the actin-binding drugs latrunculin B or cytochalasin D, has corresponding effects on Rac GTP loading. The interaction of G-actin with RPEL-family rhoGAPs thus provides a negative feedback loop that couples Rac activity to actin dynamics.

Fiber type-selective exercise effects on AS160 phosphorylation

Earlier research using muscle tissue demonstrated that postexercise elevation in insulin-stimulated glucose uptake (ISGU) occurs concomitant with greater insulin-stimulated Akt substrate of 160 kDa (AS160) phosphorylation (pAS160) on sites that regulate ISGU. Because skeletal muscle is a heterogeneous tissue, we previously isolated myofibers from rat epitrochlearis to assess fiber type-selective ISGU. Exercise induced greater ISGU in type I, IIA, IIB, and IIBX but not IIX fibers. This study tested if exercise effects on pAS160 correspond with previously published fiber type-selective exercise effects on ISGU. Rats were studied immediately postexercise (IPEX) or 3.5 h postexercise (3.5hPEX) with time-matched sedentary controls. Myofibers dissected from the IPEX experiment were analyzed for fiber type (myosin heavy chain isoform expression) and key phosphoproteins. Isolated muscles from the 3.5hPEX experiment were incubated with or without insulin. Myofibers (3.5hPEX) were analyzed for fiber type, key phosphoproteins, and GLUT4 protein abundance. We hypothesized that insulin-stimulated pAS160 at 3.5hPEX would exceed sedentary controls only in fiber types characterized by greater ISGU postexercise. Values for phosphorylation of AMP-activated kinase substrates (acetyl CoA carboxylase^Ser79 and AS160^Ser704) from IPEX muscles exceeded sedentary values in each fiber type, suggesting exercise recruitment of all fiber types. Values for pAS160^Thr642 and pAS160^Ser704 from insulin-stimulated muscles 3.5hPEX exceeded sedentary values for type I, IIA, IIB, and IIBX but not IIX fibers. GLUT4 abundance was unaltered 3.5hPEX in any fiber type. These results advanced understanding of exercise-induced insulin sensitization by providing compelling support for the hypothesis that enhanced insulin-stimulated phosphorylation of AS160 is linked to elevated ISGU postexercise at a fiber type-specific level independent of altered GLUT4 expression.

Heat shock protein 90 inhibitor regulates necroptotic cell death via down-regulation of receptor interacting proteins

17-(Dimethylaminoethylamino)-17-demethoxygeldanamycin (DMAG) acts as an inhibitor of heat shock protein 90 (HSP 90), which serves as a nodal protein of diverse signaling networks leading to a variety of biological implications. HSP90 plays the role of a chaperone for a variety of client proteins including receptor interacting protein 1 (RIP1). Since RIP1 and RIP3 are, respectively, required for zVAD- and tumor necrosis factor alpha (TNFα)-mediated necrotic cell death, we pursued to address the effects of DMAG on receptor-and nonreceptor-mediated necroptotic cell death. DMAG facilitated the degradation of receptor interacting protein 3 (RIP3) as well as RIP1, a known client protein of HSP90, in L929 cells. Consequently, DMAG rendered cells more sensitive to TNFα stimulation while it rescued cells from necrotic cell death caused by zVAD. From this study, we propose that DMAG-downregulated RIP1 can shift cell death typing from necroptosis to apoptosis. In contrast, the protective effect of DMAG on zVAD-induced cytotoxicity could be partly explained by the fact that zVAD mediates cytotoxicity via a RIP1 -dependent route. In summary, functional disruption of HSP90 by DMAG destabilized necroptosis proteins RIP1 and RIP3, which in turn regulated zVAD- and TNFα-induced necroptosis. Therefore, pharmacological modulation of necroptotic cell death through HSP90 could be a promising strategy for overcoming cancer drug resistance or protecting ischemic cell death.

Inhibition of contraction-stimulated AMP-activated protein kinase inhibits contraction-stimulated increases in PAS-TBC1D1 and glucose transport without altering PAS-AS160 in rat skeletal muscle

OBJECTIVE

Phosphorylation of two members of the TBC1 domain family of proteins, Akt substrate of 160 kDa (AS160, also known as TBC1D4) and TBC1D1, has been implicated in the regulation of glucose transport in skeletal muscle. Insulin-stimulated phosphorylation (measured using the phospho-Akt substrate [PAS] antibody) of AS160 and TBC1D1 appears to occur in an Akt-dependent manner, but the kinases responsible for contraction-stimulated PAS-AS160 and PAS-TBC1D1 remain unclear. AMP-activated protein kinase (AMPK) and Akt, both activated by contraction, can each phosphorylate AS160 and TBC1D1 in cell-free assays.

RESEARCH DESIGN AND METHODS

To evaluate the roles of AMPK and Akt on insulin- or contraction-stimulated PAS-AS160, PAS-TBC1D1, and glucose transport, rat epitrochlearis was incubated with and without compound C (inhibitor of AMPK) or Wortmannin (inhibitor of phosphatidylinositol [PI] 3-kinase, which is upstream of Akt) before and during insulin stimulation or contraction.

RESULTS

Insulin-stimulated glucose transport and phosphorylation of both AS160 and TBC1D1 were completely inhibited by Wortmannin. Wortmannin eliminated contraction stimulation of phospho-Ser(21/9)glycogen synthase kinase 3alpha/beta (pGSK3; Akt substrate) and PAS-AS160 but did not significantly alter pAMPK, phospho-Ser79acetyl CoA carboxylase (pACC; AMPK substrate), PAS-TBC1D1, or glucose transport in contraction-stimulated muscle. Compound C completely inhibited contraction-stimulated pACC and PAS-TBC1D1 and partially blocked glucose transport, but it did not significantly alter pAkt, pGSK3, or PAS-AS160.

CONCLUSIONS

These data suggest that 1) insulin stimulates glucose transport and phosphorylation of AS160 and TBC1D1 in a PI 3-kinase/Akt-dependent manner, 2) contraction stimulates PAS-AS160 (but not PAS-TBC1D1 or glucose transport) in a PI 3-kinase/Akt-dependent manner, and 3) contraction stimulates PAS-TBC1D1 and glucose transport (but not PAS-AS160) in an AMPK-dependent manner.

p190RhoGAP negatively regulates Rho activity at the cleavage furrow of mitotic cells

Previous studies demonstrated that p190RhoGAP (p190) negatively affects cytokinesis in a RhoGAP-dependent manner, suggesting that regulation of Rho may be a critical mechanism of p190 action during cytokinesis. P190 localizes to the cleavage furrow (CF) of dividing cells, and its levels decrease during late mitosis by an ubiquitin-mediated mechanism, consistent with the hypothesis that high RhoGTP levels are required for completion of cytokinesis. To determine whether RhoGTP levels in the CF are affected by p190 and to define the phase(s) of cytokinesis in which p190 is involved, we used FRET analysis alone or in combination with time-lapse microscopy. In normal cell division activated Rho accumulated at the cell equator in early anaphase and in the contractile ring, where it co-localized with p190. Real-time movies revealed that cells expressing elevated levels of p190 exhibited multiple cycles of abnormal CF site selection and ingression/regression, which resulted in failed or prolonged cytokinesis. This was accompanied by mislocalization of active Rho at the aberrant CF sites. Quantified data revealed that in contrast to ECT2 and dominate negative p190 (Y1283Ap190), which resulted in hyper-activated Rho, Rho activity in the CF was reduced by wild type p190 in a dose-dependent manner. These results suggest that p190 regulates cytokinesis through modulation of RhoGTP levels, thereby affecting CF specification site selection and subsequent ring contraction.

Impaired insulin-stimulated phosphorylation of Akt and AS160 in skeletal muscle of women with polycystic ovary syndrome is reversed by pioglitazone treatment

OBJECTIVE

Insulin resistance in skeletal muscle is a major risk factor for type 2 diabetes in women with polycystic ovary syndrome (PCOS). However, the molecular mechanisms underlying skeletal muscle insulin resistance and the insulin-sensitizing effect of thiazolidinediones in PCOS in vivo are less well characterized.

RESEARCH DESIGN AND METHODS

We determined molecular mediators of insulin signaling to glucose transport in skeletal muscle biopsies of 24 PCOS patients and 14 matched control subjects metabolically characterized by euglycemic-hyperinsulinemic clamps and indirect calorimetry, and we examined the effect of 16 weeks of treatment with pioglitazone in PCOS patients.

RESULTS

Impaired insulin-mediated total (R(d)) oxidative and nonoxidative glucose disposal (NOGD) was paralleled by reduced insulin-stimulated Akt phosphorylation at Ser473 and Thr308 and AS160 phosphorylation in muscle of PCOS patients. Akt phosphorylation at Ser473 and Thr308 correlated positively with R(d) and NOGD in the insulin-stimulated state. Serum free testosterone was inversely related to insulin-stimulated R(d) and NOGD in PCOS. Importantly, the pioglitazone-mediated improvement in insulin-stimulated glucose metabolism, which did not fully reach normal levels, was accompanied by normalization of insulin-mediated Akt phosphorylation at Ser473 and Thr308 and AS160 phosphorylation. AMPK activity and phosphorylation were similar in the two groups and did not respond to pioglitazone in PCOS patients.

CONCLUSIONS

Impaired insulin signaling through Akt and AS160 in part explains insulin resistance at the molecular level in skeletal muscle in PCOS, and the ability of pioglitazone to enhance insulin sensitivity involves improved signaling through Akt and AS160. Moreover, our data provide correlative evidence that hyperandrogenism in PCOS may contribute to insulin resistance.

Geldanamycin Anisimycins Activate Rho and Stimulate Rho- and ROCK-Dependent Actin Stress Fiber Formation

Heat shock protein 90 (Hsp90) is a member of the heat shock family of molecular chaperones that regulate protein conformation and activity. Hsp90 regulates multiple cell signaling pathways by controlling the abundance and activity of several important protein kinases and cell cycle-related proteins. In this report, we show that inhibition of Hsp90 by geldanamycin or its derivative, 17-allylamino-17-desmethoxygeldamycin, leads to activation of the Rho GTPase and a dramatic increase in actin stress fiber formation in human tumor cell lines. Inactivation of Rho prevents geldanamycin-induced actin reorganization. Hsp90 inactivation does not alter the appearance of filopodia or lamellipodia and tubulin architecture is not visibly perturbed. Our observations suggest that Hsp90 has an important and specific role in regulating Rho activity and Rho-dependent actin cytoskeleton remodeling.

Rac1 links integrin-mediated adhesion to the control of lactational differentiation in mammary epithelia

The expression of tissue-specific genes during mammary gland differentiation relies on the coincidence of two distinct signaling events: the continued engagement of β1 integrins with the extracellular matrix (ECM) and a hormonal stimulus from prolactin (Prl). How the integrin and Prl receptor (PrlR) systems integrate to regulate milk protein gene synthesis is unknown. In this study, we identify Rac1 as a key link. Dominant-negative Rac1 prevents Prl-induced synthesis of the milk protein β-casein in primary mammary epithelial cells cultured as three-dimensional acini on basement membrane. Conversely, activated Rac1 rescues the defective β-casein synthesis that occurs under conditions not normally permissive for mammary differentiation, either in β1 integrin–null cells or in wild-type cells cultured on collagen. Rac1 is required downstream of integrins for activation of the PrlR/Stat5 signaling cascade. Cdc42 is also necessary for milk protein synthesis but functions via a distinct mechanism to Rac1. This study identifies the integration of signals provided by ECM and hormones as a novel role for Rho family guanosine triphosphatases.

Distinct signals regulate AS160 phosphorylation in response to insulin, AICAR, and contraction in mouse skeletal muscle

Insulin and contraction increase GLUT4 translocation in skeletal muscle via distinct signaling mechanisms. Akt substrate of 160 kDa (AS160) mediates insulin-stimulated GLUT4 translocation in L6 myotubes, presumably through activation of Akt. Using in vivo, in vitro, and in situ methods, insulin, contraction, and the AMP-activated protein kinase (AMPK) activator AICAR all increased AS160 phosphorylation in mouse skeletal muscle. Insulin-stimulated AS160 phosphorylation was fully blunted by wortmannin in vitro and in Akt2 knockout (KO) mice in vivo. In contrast, contraction-stimulated AS160 phosphorylation was only partially decreased by wortmannin and unaffected in Akt2 KO mice, suggesting additional regulatory mechanisms. To determine if AMPK mediates AS160 signaling, we used AMPK alpha2-inactive (alpha2i) transgenic mice. AICAR-stimulated AS160 phosphorylation was fully inhibited, whereas contraction-stimulated AS160 phosphorylation was partially reduced in the AMPK alpha2i transgenic mice. Combined AMPK alpha2 and Akt inhibition by wortmannin treatment of AMPK alpha2 transgenic mice did not fully ablate contraction-stimulated AS160 phosphorylation. Maximal insulin, together with either AICAR or contraction, increased AS160 phosphorylation in an additive manner. In conclusion, AS160 may be a point of convergence linking insulin, contraction, and AICAR signaling. While Akt and AMPK alpha2 activities are essential for AS160 phosphorylation by insulin and AICAR, respectively, neither kinase is indispensable for the entire effects of contraction on AS160 phosphorylation.

Regulation of RhoGAP Specificity by Phospholipids and Prenylation

Among the key protein regulators of the various and numerous small GTPases are the GTPase activating proteins (GAPs). Experimental studies of some of the approximately 170 GAPs predicted by the human genome indicate that their catalytic GAP activity is regulated by a variety of mechanisms, including phosphorylation, protein-protein interactions, proteolysis, and interactions with lipids. Most reported biochemical studies to address the specificity of GAPs for particular GTPases have been conducted in vitro with bacterially produced GTPases. Thus, the potential influence of these various regulatory mechanisms in the context of GAP-GTPase specificity may be overlooked in such assays. Here, we present experimental studies that highlight the role of lipids in modulating the GTPase specificity for some of the Rho GAPs. We find that particular phospholipids can substantially alter the substrate "preference" for the p190 GAPs. We find that C-terminal prenylation of GTPases can influence the specificity of GAP interactions as well. These observations emphasize the limitations of standard in vitro GAP assays in definitively establishing the physiologically relevant GTPase targets for particular GAPs.

AlFx affects the formation of focal complexes by stabilizing the Arf-GAP ASAP1 in a complex with Arf1

Aluminum fluoride (AlFx) is known to activate directly the alpha subunit of G-proteins but not the homologous small GTP-binding proteins. However, AlFx can stabilize complexes formed between Ras, RhoA or Cdc42 and their corresponding GTPase-activating proteins (GAPs). Here, we demonstrate that Arf1GDP can be converted into an active conformation by AlFx to form a complex with the Arf-GAP ASAP1 in vitro and in vivo. Within this complex ASAP1, which GAP activity is inoperative, can still alter the recruitment of paxillin to the focal complexes, thus indicating that ASAP1 interferes with focal complexes independently of its GAP activity.

A genetic screen identifies PITX1 as a suppressor of RAS activity and tumorigenicity

Activating mutations of RAS frequently occur in subsets of human cancers, indicating that RAS activation is important for tumorigenesis. However, a large proportion of these cancers still retain wild-type RAS alleles, suggesting that either the RAS pathway is activated in a distinct manner or another pathway is deregulated. To uncover novel tumor-suppressor genes, we screened an RNA-interference library for knockdown constructs that transform human primary cells in the absence of ectopically introduced oncogenic RAS. Here we report the identification of PITX1, whose inhibition induces the RAS pathway and tumorigenicity. Interestingly, we observed low expression of PITX1 in prostate and bladder tumors and in colon cancer cell lines containing wild-type RAS. Restoration of PITX1 in the colon cancer cells inhibited tumorigenicity in a wild-type RAS-dependent manner. Finally, we identified RASAL1, a RAS-GTPase-activating protein, as a transcription target through which PITX1 affects RAS function. Thus, PITX1 suppresses tumorigenicity by downregulating the RAS pathway through RASAL1.

Estrogen treatment increases the levels of regulator of G protein signaling-Z1 in the hypothalamic paraventricular nucleus: possible role in desensitization of 5-hydroxytryptamine1A receptors

Desensitization of post-synaptic serotonin1A (5-HT1A) receptors may underlie the clinical improvement of neuropsychiatric disorders. In the hypothalamic paraventricular nucleus, Galphaz proteins mediate the 5-HT1A receptor-stimulated increases in hormone release. Regulator of G protein signaling-Z1 (RGSZ1) is a GTPase-activating protein selective for Galphaz proteins. RGSZ1 regulates the duration of interaction between Galphaz proteins and effector systems. The present investigation determined the levels of RGSZ1 in the hypothalamic paraventricular nucleus of rats subjected to four different treatment protocols that produce desensitization of 5-HT1A receptors. These protocols include: daily administration of beta estradiol 3-benzoate (estradiol) for 2 days; daily administration of fluoxetine for 3 and 14 days; daily administration of cocaine for 7 or 14 days; and acute administration of (+/-)-1-(2,5 dimethoxy-4-iodophenyl)-2-amino-propane HCl (DOI; a 5-HT2A/2C receptor agonist). Estradiol treatment was the only protocol that increased the levels of RGSZ1 protein in the hypothalamic paraventricular nucleus in a dose-dependent manner (46%-132% over control). Interestingly, previous experiments indicate that only estradiol produces a decreased Emax of 5-HT1A receptor-stimulation of hormone release, whereas fluoxetine, cocaine and DOI produce a shift to the right (increased ED50). Thus, the desensitization of 5-HT1A receptors by estradiol might be attributable to increased levels of RGSZ1 protein. These findings may provide insight into the adaptation of 5-HT1A receptor signaling during pharmacotherapies of mood disorders in women and the well-established gender differences in the vulnerability to depression.

The mutation in the N-terminal domain of RGS4 disrupts PA-conferred inhibitory effect on GAP activity

Regulator of G protein signaling (RGS) proteins are GTPase-activating proteins (GAP) for G protein alpha-subunits and are thought to be responsible for rapid deactivation of G protein mediated signaling pathway. In this present study, we demonstrate that PA is the most efficient candidate to inhibit GAP activity of RGS4. The functional significance of N-terminus of RGS4 in respose to PA-granted inhibition on GAP activity has been studied with the site mutation in the N-terminus of RGS4. These site-directed mutations in the N-terminal domain do not severely disrupt its association with liposomes of PA. However, RGS4L23E diminishes the inhibition of GAP activity by PA compared with the wild type RGS4, whereas RGSR22E abrogates the inhibitory effect by PA on GAP activity. The correspondent conformational discrepancy in the RGS domain of these mutants in the presence of PA vesicles was detected from fluorescence experiments. It is suggested that the functional pertinence between the N-terminus and RGS domain may be important to modulate PA-conferred inhibitory effect on its GAP activity.

Areca nut extract treatment elicits the fibroblastoid morphological changes, actin re-organization and signaling activation in oral keratinocytes

BACKGROUND

Areca (named as betel) is an important etiological factor linked with the high prevalence of oral squamous cell carcinoma (OSCC) in South-Asian countries. This in vitro study investigated the cellular changes and signaling activation in oral keratinocytes in response to areca nut extract (ANE) treatment.

METHODS

Normal human oral keratinocyte (NHOK) and oral epidermoid carcinoma cell, Meng-1 (OECM-1) OSCC cell line were treated with variable dosages of ripen ANE. The morphological and cytoskeletal changes, as well as the activation of GTPase proteins and signaling kinases, were analyzed.

RESULTS

Most NHOK cells in culture were polygonal, with only <5% cells exhibiting fibroblastoid morphology. However, 10 microg/ml ANE elicited fibroblastoid morphological change, genesis of lamellipodia, loss of subcortical actin, and stress-fiber formation in approximately 25% cultivated NHOK cells. Similar morphological changes were observed in nearly all OECM-1 cells following the ANE treatment. The activation of Rac and Rho GTPase, together with the prominent phosphorylation of a stress-activated kinases, particularly JNK1, was identified in treated OECM-1 cells.

CONCLUSION

The novel evidences from the study that ANE impairs the actin organization and activates the signals in oral keratinocytes might bestow further insight into the impacts of ANE in oral pathogenesis.

The Ras GDP/GTP cycle is regulated by oxidizing agents at the level of Ras regulators and effectors

Reactive oxygen species (ROS) have been found to play important roles in regulating cellular functions. Their action in vivo has been related to specific effects on signal transduction pathways, such as Ras pathway. In order to characterize which elements of Ras pathway are affected by ROS, we have analyzed the action of different oxidizing agents on the ability of GTPase activating protein GAP and nucleotide exchange factor GEF to enhance the intrinsic activities of Ras. The action of these agents on the binding between H-Ras and its effector c-Raf-1 was also investigated. No effects were observed on the intrinsic activities of H-Ras or Ras2p. On the other hand, reversible inhibitions of GEF and GAP actions on Ras were found, whose extent was dependent on the agent used. As tested with the scintillation proximity assay, these agents also inhibited the binding of c-Raf-1 to H-Ras. Our data reveal new potential targets for the action of ROS on Ras pathway and suggest that they can influence the Ras activation state indirectly via regulators and effectors.