Proteins regulating Ras and its relatives

Tiam-1, a GEF for Rac1, plays a critical role in metformin-mediated glucose uptake in C2C12 cells

Metformin is known to stimulate glucose uptake, but the mechanism for this action is not fully understood. In this study, AMPK activators (AICAR and metformin) increased the expression of T-lymphoma invasion and metastasis-inducing protein-1 (Tiam-1), a Rac1 specific guanine nucleotide exchange factor (GEF), mRNA and protein in skeletal muscle C2C12 cells. Metformin increases the serine-phosphorylation of Tiam-1 by AMPK and induces interaction between Tiam-1 and 14-3-3. Pharmacologic inhibition of AMPK blocks this interaction, indicating that 14-3-3 may be required for induction of Tiam-1 by AMPK. Metformin also increases the phosphorylation of p21-activated kinase 1 (PAK1), a direct downstream target of Rac1, dependent on AMPK. Tiam-1 is down-regulated at high glucose concentrations in cultured cells and in the db/db mouse model of hyperglycemia. Furthermore, Tiam-1 knock-down blocked metformin-induced increase in glucose uptake. These findings suggest that metformin promotes cellular glucose uptake in part through Tiam-1 induction.

The effect of simvastatin on lipid droplets accumulation in human embryonic kidney cells and pancreatic cancer cells

Background

Statins (HMG-CoA reductase inhibitors) represent a major class of compounds for the treatment of hypercholesterolemia due to their ability to inhibit de novo cholesterol synthesis. In addition to their hypolipidemic effects, chemoprotective properties have been attributed to statins as well. These effects involve multiple mechanisms, which, however, are not known in detail. The aim of our study was to assess in non-malignant as well as cancer cells the impact of simvastatin on the amount of cytosolic lipid droplets (LDs) implicated in many biological processes including proliferation, inflammation, carcinogenesis, apoptosis, necrosis or growth arrest.

Methods

Human embryonic kidney cells HEK-293T and human pancreatic cancer cells MiaPaCa-2 were treated with simvastatin (6 and 12 μM) for 24 and 48 hours respectively. Neutral lipid probe Nile Red was used for detection of LDs by fluorescence microscopy. Cellular cholesterol content was determined by HPLC. Changes in expression of genes related to lipid metabolism in simvastatin-treated MiaPaCa-2 cells were examined by DNA microarray analysis. Validation of gene expression changes was performed using quantitative RT-PCR.

Results

The treatment of the cells with simvastatin increased their intracellular content of LDs in both non-malignant as well as cancer cells, partially due to the uptake of cholesterol and triacylglyceroles from medium; but in particular, due to enhanced synthesis of triacylglyceroles as proved by significant overexpression of genes related to de novo synthesis of triacylglyceroles and phospholipids. In addition, simvastatin also markedly influenced expression of genes directly affecting cell proliferation and signaling.

Conclusions

Simvastatin treatment led to accumulation of cytosolic LDs within the examined cells, a phenomenon which might contribute to the antiproliferative effects of statins.

Expression of neuroepithelial transforming gene 1 is enhanced in oesophageal cancer and mediates an invasive tumour cell phenotype

INTRODUCTION

Neuroepithelial Transforming Gene 1 (NET1) is a well characterised oncoprotein and a proven marker of an aggressive phenotype in a number of cancers, including gastric adenocarcinoma. We aimed to investigate whether NET1 plays a functional role in oesophageal cancer (OAC) and its pre-malignant phenotype Barrett's oesophagus.

METHODS

Baseline NET1 mRNA levels were determined by qPCR across a panel of six cell lines, including normal oesophageal, Barrett's and OAC derived cells. Quantification of NET1 protein in OAC cells was performed using Western blot and immunofluorescence. NET1 expression was modulated by treating with lysophosphatidic acid (LPA) and NET1-specific siRNA. The functional effects of NET1 knockdown were assessed in vitro using proliferation, migration and invasion assays.

RESULTS

NET1 expression was increased in Barrett's and in OAC-derived cells in comparison to normal oesophageal cells. The highest expression was observed in OE33 a Barrett's-related OAC cell line. NET1 protein and mRNA expression was enhanced by LPA treatment in OAC and furthermore LPA treatment caused increased proliferation, migration and invasion in a NET1-dependent manner. NET1 knockdown resulted in reduced OAC cell proliferation and invasion.

CONCLUSIONS

As found in other malignancies, NET1 expression is elevated in OAC and its pre-malignant phenotype, Barrett's oesophagus. NET1 promotes OAC cell invasion and proliferation and it mediates LPA-induced OAC cell migration.

Rap-afadin axis in control of Rho signaling and endothelial barrier recovery

This study describes the novel role of Rap1 as a molecular switch for down-regulation of the Rho-dependent pathway of agonist-induced endothelial hyperpermeability. The Rho-Rap-Rac autoregulation loop may represent a fundamental mechanism of homeostasis and be critical for reestablishment of cell monolayer integrity in pathological conditions.

Activation of the Rho GTPase pathway determines endothelial cell (EC) hyperpermeability after injurious stimuli. To date, feedback mechanisms of Rho down-regulation critical for barrier restoration remain poorly understood. We tested a hypothesis that Rho down-regulation and barrier recovery of agonist-stimulated ECs is mediated by the Ras family GTPase Rap1. Thrombin-induced EC permeability driven by rapid activation of the Rho GTPase pathway was followed by Src kinase–dependent phosphorylation of the Rap1-specific guanine nucleotide exchange factor (GEF) C3G, activation of Rap1, and initiation of EC barrier recovery. Knockdown experiments showed that Rap1 activation was essential for down-regulation of Rho signaling and actin stress fiber dissolution. Rap1 activation also enhanced interaction between adherens junction (AJ) proteins VE-cadherin and p120-catenin and stimulated AJ reannealing mediated by the Rap1 effector afadin. This mechanism also included Rap1-dependent membrane translocation of the Rac1-specific GEF Tiam1 and activation of Rac1-dependent peripheral cytoskeletal dynamics, leading to resealing of intercellular gaps. These data demonstrate that activation of the Rap1-afadin axis is a physiological mechanism driving restoration of barrier integrity in agonist-stimulated EC monolayers via negative-feedback regulation of Rho signaling, stimulation of actin peripheral dynamics, and reestablishment of cell–cell adhesive complexes.

3,4-dihydroxyphenyl acetic acid and (+)-epoxydon isolated from marine algae-derived microorganisms induce down regulation of epidermal growth factor activated mitogenic signaling cascade in Hela cells

Background

Epidermal growth factor receptor (EGFR) is a member of the receptor tyrosine kinase (RTK) family. Epidermal growth factor induces its dimerization and stimulates phosphorylation of intracellular tyrosine residues. Phosphorylation of EGFR is studied for cancer therapy because EGFR regulates many cellular processes including cell proliferation, differentiation, and survival. Hence, down-regulation of EGFR kinase activity results in inhibition of signaling cascades amenable for proliferation and progression of cell cycle.

Methods

In the study, we purified 3,4-dihydroxyphenyl acetic acid and (+)-epoxydon from Aspergillus sp. isolated from marine brown alga Ishige okamurae and Phoma herbarum isolated from marine red alga Hypnea saidana respectively and determined its anti-tumor activities against HeLa human cervical cancer cells.

Results

Two compounds suppressed EGFR activity in vitro with IC₅₀ values for 3,4-dihydroxyphenyl acetic acid and (+)-epoxydon were 2.8 and 0.6 μg/mL respectively and reduced the viable numbers of HeLa cells. Immunoblotting analysis exhibited that the compounds induced inhibition of cell growth by causing downregulation of the mitogenic signaling cascade, inactivation of p90RSK, and release of cytochrome c from mitochondria.

Conclusions

Results suggest that decreased expression of active EGFR and EGFR-related downstream molecules by treatment with the compounds may results in the inhibition of cell growth and inducement of apoptosis.

Colorectal cancer: molecular mutations and polymorphisms

Colorectal cancer (CRC) is one of the major causes of mortality and morbidity, and is the third most common cancer in men and the second most common cancer in women worldwide. The incidence of CRC shows considerable variation among racially or ethnically defined populations in multiracial/ethnic countries. The tumorigenesis of CRC is either because of the chromosomal instability (CIN) or microsatellite instability (MIN) or involving various proto-oncogenes, tumor-suppressor genes, and also epigenetic changes in the DNA. In this review I have focused on the mutations and polymorphisms of various important genes of the CIN and MIN pathways which have been implicated in the development of CRC.

Roles of rho GTPases in intracellular transport and cellular transformation

Rho family GTPases belong to the Ras GTPase superfamily and transduce intracellular signals known to regulate a variety of cellular processes, including cell polarity, morphogenesis, migration, apoptosis, vesicle trafficking, viral transport and cellular transformation. The three best-characterized Rho family members are Cdc42, RhoA and Rac1. Cdc42 regulates endocytosis, the transport between the endoplasmic reticulum and Golgi apparatus, post-Golgi transport and exocytosis. Cdc42 influences trafficking through interaction with Wiskott-Aldrich syndrome protein (N-WASP) and the Arp2/3 complex, leading to changes in actin dynamics. Rac1 mediates endocytic and exocytic vesicle trafficking by interaction with its effectors, PI3kinase, synaptojanin 2, IQGAP1 and phospholipase D1. RhoA participates in the regulation of endocytosis through controlling its downstream target, Rho kinase. Interestingly, these GTPases play important roles at different stages of viral protein and genome transport in infected host cells. Importantly, dysregulation of Cdc42, Rac1 and RhoA leads to numerous disorders, including malignant transformation. In some cases, hyperactivation of Rho GTPases is required for cellular transformation. In this article, we review a number of findings related to Rho GTPase function in intracellular transport and cellular transformation.

MEK inhibitors as a chemotherapeutic intervention in multiple myeloma

The Ras/Raf/MEK/extracellular signal regulated kinase (ERK) (Ras/mitogen-activated protein kinases (MAPK)) signal transduction pathway is a crucial mediator of many fundamental biological processes, including cellular proliferation, survival, angiogenesis and migration. Aberrant signalling through the Ras/MAPK cascade is common in a wide array of malignancies, including multiple myeloma (MM), making it an appealing candidate for the development of novel targeted therapies. In this review, we explore our current understanding of the Ras/MAPK pathway and its role in MM. Additionally, we summarise the current status of small molecule inhibitors of MEK under clinical evaluation, and discuss future approaches required to optimise their use.

In silico tissue-distribution of human Rho family GTPase activating proteins

Rho family small GTPases are involved in the spatio-temporal regulation of several physiological processes. They operate as molecular switches based on their GTP- or GDP-bound state. Their GTPase activator proteins (Rho/Rac GAPs) are able to increase the GTP hydrolysis of small GTPases, which turns them to an inactive state. This regulatory step is a key element of signal termination. According to the human genome project the potential number of Rho family GAPs is approximately 70. Despite their significant role in cellular signaling our knowledge on their expression pattern is quite incomplete. In this study we tried to reveal the tissue-distribution of Rho/Rac GAPs based on expressed sequence tag (EST) database from healthy and tumor tissues and microarray experiments. Our accumulated data sets can provide important starting information for future research. However, the nomenclature of Rho family GAPs is quite heterogeneous. Therefore we collected the available names, abbreviations and aliases of human Rho/Rac GAPs in a useful nomenclature table. A phylogenetic tree and domain structure of 65 human RhoGAPs are also presented.

Sensitivity of malignant peripheral nerve sheath tumor cells to TRAIL is augmented by loss of NF1 through modulation of MYC/MAD and is potentiated by curcumin through induction of ROS

Malignant peripheral nerve sheath tumor (MPNST) is a rare aggressive form of sarcoma often associated with the tumor syndrome neurofibromatosis type 1 (NF1). We investigated the effects of tumor necrosis factor-related apoptosis inducing ligand (TRAIL) on NF1 associated MPNST and determinants of TRAIL sensitivity. MPNST cell lines with complete neurofibromin deficiency were sensitive to apoptotic cell death induced by TRAIL whereas MPNST cells with retained neurofibromin expression or normal human Schwann cells were resistant. Increased sensitivity to TRAIL was associated with overexpression of death receptors, especially DR5. Re-expression of the GAP related domain of neurofibromin (NF1-GRD) suppressed DR5 expression and decreased sensitivity to TRAIL. We show that death receptor expression and TRAIL sensitivity critically depend on c-MYC and that c-MYC amounts are increased by MEK/ERK and PI3K/AKT signalling pathways which are suppressed by neurofibromin. Furthermore PI3K/AKT signalling strongly suppresses the MYC-antagonist MAD1 which significantly contributes to TRAIL sensitivity. Re-expression of the NF1-GRD decreased c-MYC and increased MAD1 amounts suggesting that neurofibromin influences TRAIL sensitivity at least in part by modulating the MYC/MAX/MAD network. The phytochemical curcumin further increased the sensitivity of neurofibromin deficient MPNST cells to TRAIL. This was presumably mediated by ROS, as it correlated with increased ROS production, was blocked by N-acetylcysteine and mimicked by exogenous ROS.

Landscape of somatic single-nucleotide and copy-number mutations in uterine serous carcinoma

Uterine serous carcinoma (USC) is a biologically aggressive subtype of endometrial cancer. We analyzed the mutational landscape of USC by whole-exome sequencing of 57 cancers, most of which were matched to normal DNA from the same patients. The distribution of the number of protein-altering somatic mutations revealed that 52 USC tumors had fewer than 100 (median 36), whereas 5 had more than 3,000 somatic mutations. The mutations in these latter tumors showed hallmarks of defects in DNA mismatch repair. Among the remainder, we found a significantly increased burden of mutation in 14 genes. In addition to well-known cancer genes (i.e., TP53, PIK3CA, PPP2R1A, KRAS, FBXW7), there were frequent mutations in CHD4/Mi2b, a member of the NuRD-chromatin-remodeling complex, and TAF1, an element of the core TFIID transcriptional machinery. Additionally, somatic copy-number variation was found to play an important role in USC, with 13 copy-number gains and 12 copy-number losses that occurred more often than expected by chance. In addition to loss of TP53, we found frequent deletion of a small segment of chromosome 19 containing MBD3, also a member of the NuRD-chromatin-modification complex, and frequent amplification of chromosome segments containing PIK3CA, ERBB2 (an upstream activator of PIK3CA), and CCNE1 (a target of FBXW7-mediated ubiquitination). These findings identify frequent mutation of DNA damage, chromatin remodeling, cell cycle, and cell proliferation pathways in USC and suggest potential targets for treatment of this lethal variant of endometrial cancer.

Effect of coenzyme Q10 on proteomic profile of blood plasma and cytosolic and microsomal fractions of rat hepatocytes during ontogeny

The proteomic features of blood plasma and subcellular fractions of rat hepatocytes were studied during long-term dietary consumption of coenzyme Q10 as the endogenous mediator of antioxidant and energy homeostasis in the cell. Long-term coenzyme Q10 consumption was followed by the formation of specific nutriproteomes of the microsomal and cytosolic fractions of rat hepatocytes.

A genome-scale RNA interference screen implicates NF1 loss in resistance to RAF inhibition

RAF inhibitors such as vemurafenib and dabrafenib block BRAF-mediated cell proliferation and achieve meaningful clinical benefit in the vast majority of patients with BRAF(V600E)-mutant melanoma. However, some patients do not respond to this regimen, and nearly all progress to therapeutic resistance. We used a pooled RNA interference screen targeting more than 16,500 genes to discover loss-of-function events that could drive resistance to RAF inhibition. The highest ranking gene was NF1, which encodes neurofibromin, a tumor suppressor that inhibits RAS activity. NF1 loss mediates resistance to RAF and mitogen-activated protein kinase (MAPK) kinase kinase (MEK) inhibitors through sustained MAPK pathway activation. However, cells lacking NF1 retained sensitivity to the irreversible RAF inhibitor AZ628 and an ERK inhibitor. NF1 mutations were observed in BRAF-mutant tumor cells that are intrinsically resistant to RAF inhibition and in melanoma tumors obtained from patients exhibiting resistance to vemurafenib, thus showing the clinical potential for NF1-driven resistance to RAF/MEK-targeted therapies.

Characterization of in vivo functions of Nicotiana benthamiana RabE1

We characterized the gene expression, subcellular localization, and in vivo functions of a Nicotiana benthamiana small GTPase belonging to the RabE family, designated NbRabE1. The NbRabE1 promoter drove strong β-glucuronidase reporter expression in young tissues containing actively dividing cells and in stomata guard cells. GFP fusion proteins of NbRabE1 and its dominant-negative and constitutively active mutants were all localized to the Golgi apparatus and the plasma membrane but showed different affinities for membrane attachment. Virus-induced gene silencing of NbRabE1 resulted in pleiotropic phenotypes, including growth arrest, premature senescence, and abnormal leaf development. At the cellular level, the leaves in which NbRabE1 was silenced contained abnormal stomata that lacked pores or contained incomplete ventral walls, suggesting that NbRabE1 deficiency leads to defective guard cell cytokinesis. Ectopic expression of the dominant-negative mutant of NbRabE1 in Arabidopsis thaliana resulted in retardation of shoot and root growth accompanied by defective root hair formation. These developmental defects are discussed in conjunction with proposed functions of RabE GTPases in polarized secretory vesicle trafficking.

Discovery of Novel DENN Proteins: Implications for the Evolution of Eukaryotic Intracellular Membrane Structures and Human Disease

The tripartite DENN module, comprised of a N-terminal longin domain, followed by DENN, and d-DENN domains, is a GDP-GTP exchange factor (GEFs) for Rab GTPases, which are regulators of practically all membrane trafficking events in eukaryotes. Using sequence and structure analysis we identify multiple novel homologs of the DENN module, many of which can be traced back to the ancestral eukaryote. These findings provide unexpected leads regarding key cellular processes such as autophagy, vesicle-vacuole interactions, chromosome segregation, and human disease. Of these, SMCR8, the folliculin interacting protein-1 and 2 (FNIP1 and FNIP2), nitrogen permease regulator 2 (NPR2), and NPR3 are proposed to function in recruiting Rab GTPases during different steps of autophagy, fusion of autophagosomes with the vacuole and regulation of cellular metabolism. Another novel DENN protein identified in this study is C9ORF72; expansions of the hexanucleotide GGGGCC in its first intron have been recently implicated in amyotrophic lateral sclerosis (ALS) and fronto-temporal dementia (FTD). While this mutation is proposed to cause a RNA-level defect, the identification of C9ORF72 as a potential DENN-type GEF raises the possibility that at least part of the pathology might relate to a specific Rab-dependent vesicular trafficking process, as has been observed in the case of some other neurological conditions with similar phenotypes. We present evidence that the longin domain, such as those found in the DENN module, are likely to have been ultimately derived from the related domains found in prokaryotic GTPase-activating proteins of MglA-like GTPases. Thus, the origin of the longin domains from this ancient GTPase-interacting domain, concomitant with the radiation of GTPases, especially of the Rab clade, played an important role in the dynamics of eukaryotic intracellular membrane systems.

IgM-mediated autoimmune responses directed against anchorage epitopes are greater in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) than in major depression

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) and depression are considered to be neuro-immune disorders (Maes and Twisk, BMC Medicine 8:35, 2010). There is also evidence that depression and ME/CFS are accompanied by oxidative and nitrosative stress (O&NS) and by increased autoantibodies to a number of self-epitopes some of which have become immunogenic due to damage by O&NS. The aim of this study is to examine IgM-mediated autoimmune responses to different self-epitopes in ME/CFS versus depression. We examined serum IgM antibodies to three anchorage molecules (palmitic and myristic acid and S-farnesyl-L-cysteine); acetylcholine; and conjugated NO-modified adducts in 26 patients with major depression; 16 patients with ME/CFS, 15 with chronic fatigue; and 17 normal controls. Severity of fatigue and physio-somatic (F&S) symptoms was measured with the Fibromyalgia and Chronic Fatigue Syndrome Rating Scale. Serum IgM antibodies to the three anchorage molecules and NO-phenylalanine were significantly higher in ME/CFS than in depression. The autoimmune responses to oxidatively, but not nitrosatively, modified self-epitopes were significantly higher in ME/CFS than in depression and were associated with F&S symptoms. The autoimmune activity directed against conjugated acetylcholine did not differ significantly between ME/CFS and depression, but was greater in the patients than controls. Partially overlapping pathways, i.e. increased IgM antibodies to a multitude of neo-epitopes, underpin both ME/CFS and depression, while greater autoimmune responses directed against anchorage molecules and oxidatively modified neo-epitopes discriminate patients with ME/CFS from those with depression. These autoimmune responses directed against neoantigenic determinants may play a role in the dysregulation of key cellular functions in both disorders, e.g. intracellular signal transduction, cellular differentiation and apoptosis, but their impact may be more important in ME/CFS than in depression.

Advances in the genetics of high-risk childhood B-progenitor acute lymphoblastic leukemia and juvenile myelomonocytic leukemia: implications for therapy

Hematologic malignancies of childhood comprise the most common childhood cancers. These neoplasms derive from the pathologic clonal expansion of an abnormal cancer-initiating cell and span a diverse spectrum of phenotypes, including acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML), myeloproliferative neoplasms (MPN), and myelodysplastic syndromes (MDS). Expansion of immature lymphoid or myeloid blasts with suppression of normal hematopoiesis is the hallmark of ALL and AML, whereas MPN is associated with proliferation of 1 or more lineages that retain the ability to differentiate, and MDS is characterized by abnormal hematopoiesis and cytopenias. The outcomes for children with the most common childhood cancer, B-progenitor ALL (B-ALL), in general, is quite favorable, in contrast to children affected by myeloid malignancies. The advent of highly sensitive genomic technologies reveals the remarkable genetic complexity of multiple subsets of high-risk B-progenitor ALL, in contrast to a somewhat simpler model of myeloid neoplasms, although a number of recently discovered alterations displayed by both types of malignancies may lead to common therapeutic approaches. This review outlines recent advances in our understanding of the genetic underpinnings of high-risk B-ALL and juvenile myelomonocytic leukemia, an overlap MPN/MDS found exclusively in children, and we also discuss novel therapeutic approaches that are currently being tested in clinical trials. Recent insights into the clonal heterogeneity of leukemic samples and the implications for diagnostic and therapeutic approaches are also discussed.

Potential for statins in the chemoprevention and management of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a common, treatment-resistant malignancy with a complex molecular pathogenesis. Statins are a widely used class of cholesterol-lowering drugs with potential anticancer activity. We reviewed the evidence for a role of statins in primary and secondary chemoprevention of HCC and slowing the course of otherwise incurable primary or recurrent disease. A literature search (key words: Statins, hepatocellular carcinoma) conducted to this end, retrieved 119 references. Here we summarize the history, mechanism of action and cardiovascular use of statins and highlight that statins can affect several pathways implicated in the development of HCC. In vitro and animal studies provide strong evidence for a favorable effect of statins on HCC. However, evidence in humans is conflicting. We discuss in full detail the methodological strengths and pitfalls of published data including three cohort studies suggesting that the use of statins may protect from the development of HCC and of a single trial reporting increased survival in those with advanced HCC randomized to receive statins. A remarkably hepato-safe class of drugs acting on both hepatocyte and endothelial cells, statins also have potentially beneficial effects in lowering portal hypertension. In conclusion, there is strong experimental evidence that statins are beneficial in chemopreventing and slowing the growth of HCC. However, randomized controlled trials are necessary in order to investigate the role of statins in the chemoprevention of HCC and in slowing the course of otherwise incurable disease in humans.

K-Ras gene mutation status as a prognostic and predictive factor in patients with colorectal cancer undergoing irinotecan- or oxaliplatin-based chemotherapy

BACKGROUND

CRC caused more than 600,000 estimated deaths in 2008. Dysregulated signaling through the RAS/RAF/mitogen-activated protein kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling pathway due to mutations in K-Ras and B-Raf are common events in CRC.

METHODS

Incidence of mutations in codons 12 and 13 of K-Ras and exons 11 and 15 of B-Raf were analyzed in amplified PCR products from primary tumors of 273 patients with CRC, and their prognostic and predictive significance was assessed. The prognostic role of clinical and pathological factors was also examined.

RESULTS

K-Ras mutations were present in 89 patients (32.6%), of whom 76 (85.4%) had mutations in codon 12 and 10 (11.2%) had mutations in codon 13. B-Raf gene mutations were present in 17 patients (6.9%), of whom 6 (35.3%) had mutations in exon 15. Multivariate analysis revealed a predictive significance for K-Ras mutations with respect to time to progression in patients treated with irinotecan and oxaliplatin as first-line chemotherapy. There was no predictive significance for B-Raf gene mutation status in these patients. The following risk factors were found to affect overall survival (OS) rates: primary tumor location, lymph node involvement grade, carcinoembryonic antigen (CEA) level before treatment, and performance status according to WHO criteria.

CONCLUSIONS

Based on the results of this study, K-Ras mutation status may be a suitable indicator of patient eligibility and a prognostic indicator for responsiveness to anti-EGFR therapy alone, or in combination with chemotherapy. Also, K-Ras mutation status may predict time to progression in patients treated with irinotecan and oxaliplatin.

Expression, Purification, and Characterization of Ras Protein (BmRas1) from Bombyx mori

The Ras subfamily is the member of small G proteins superfamily involved in cellular signal transduction. Activation of Ras signaling causes cell growth, differentiation, and survival. Bombyx mori Ras-like protein (BmRas1) may belong to the Ras subfamily. It contained an H-N-K-Ras-like domain. The BmRas1 mRNA consisted of 1459 bp. The open reading frame contained 579 bp, encoding 192 amino acids. The protein had such secondary structures as α-helices, extended strand, and random coil. BmRas1 was expressed successfully in E. coli BL21. The recombinant protein was purified with metal-chelating affinity chromatography. The GTPase activity of purified protein was determined by FeSO(4)-(NH(4))(2)MoO(4) assay. The results showed that purified recombinant protein had intrinsic activity of GTPase. High titer polyclonal antibodies were generated by New Zealand rabbit immunized with purified protein. The gene expression features of BmRas1 at different stages and in different organs of the fifth instar larvae were analyzed by Western blot. The results showed that BmRas1 was expressed highly in three development stages including egg, pupae, and adult, but low expression in larva. BmRas1 was expressed in these tissues including head, malpighian tubule, genital gland, and silk gland. The purified recombinant protein would be utilized to further function studies of BmRas1.

FTS and 2-DG induce pancreatic cancer cell death and tumor shrinkage in mice

The Ras inhibitor S-trans-trans farnesylthiosalicylic acid (FTS) inhibits active Ras, which controls cell proliferation, differentiation, survival, and metabolism. FTS also inhibits HIF1α expression in cancer cells, leading to an energy crisis. The synthetic glucose analog 2-deoxy-D-glucose (2-DG), which inhibits glycolysis, is selectively directed to tumor cells that exhibit increased glucose consumption. The 2-DG enters tumor cells, where it competes with glucose for glycolytic enzymes. In cancer models, as well as in human phase 1 trials, 2-DG inhibits tumor growth without toxicity. We postulated that under normoxic conditions, tumor cells treated with FTS would be more sensitive than normal cells to 2-DG. We show here that combined treatment with FTS and 2-DG inhibited cancer cell proliferation additively, yet induced apoptotic cell death synergistically both in vitro and in vivo. The induced apoptosis was inferred from QVD-OPH inhibition, an increase in cleaved caspase 3, and loss of survivin. FTS and 2-DG when combined, but not separately, also induced an increase in fibrosis of the tumor tissue, chronic inflammation, and tumor shrinkage. Overall, these results suggest a possible new treatment of pancreatic tumors by the combined administration of FTS and 2-DG, which together induce pancreatic tumor cell death and tumor shrinkage under non-toxic conditions.

Inhibition and Termination of Physiological Responses by GTPase Activating Proteins

Physiological processes are strictly organized in space and time. However, in cell physiology research, more attention is given to the question of space rather than to time. To function as a signal, environmental changes must be restricted in time; they need not only be initiated but also terminated. In this review, we concentrate on the role of one specific protein family involved in biological signal termination. GTPase activating proteins (GAPs) accelerate the endogenously low GTP hydrolysis rate of monomeric guanine nucleotide-binding proteins (GNBPs), limiting thereby their prevalence in the active, GTP-bound form. We discuss cases where defective or excessive GAP activity of specific proteins causes significant alteration in the function of the nervous, endocrine, and hemopoietic systems, or contributes to development of infections and tumors. Biochemical and genetic data as well as observations from human pathology support the notion that GAPs represent vital elements in the spatiotemporal fine tuning of physiological processes.

The phospholipase C isozymes and their regulation

The physiological effects of many extracellular neurotransmitters, hormones, growth factors, and other stimuli are mediated by receptor-promoted activation of phospholipase C (PLC) and consequential activation of inositol lipid signaling pathways. These signaling responses include the classically described conversion of phosphatidylinositol(4,5)P(2) to the Ca(2+)-mobilizing second messenger inositol(1,4,5)P(3) and the protein kinase C-activating second messenger diacylglycerol as well as alterations in membrane association or activity of many proteins that harbor phosphoinositide binding domains. The 13 mammalian PLCs elaborate a minimal catalytic core typified by PLC-d to confer multiple modes of regulation of lipase activity. PLC-b isozymes are activated by Gaq- and Gbg-subunits of heterotrimeric G proteins, and activation of PLC-g isozymes occurs through phosphorylation promoted by receptor and non-receptor tyrosine kinases. PLC-e and certain members of the PLC-b and PLC-g subclasses of isozymes are activated by direct binding of small G proteins of the Ras, Rho, and Rac subfamilies of GTPases. Recent high resolution three dimensional structures together with biochemical studies have illustrated that the X/Y linker region of the catalytic core mediates autoinhibition of most if not all PLC isozymes. Activation occurs as a consequence of removal of this autoinhibition.

KRAS mutant colorectal tumors: past and present

The treatment of metastatic colorectal cancer (mCRC) remains one of the largest hurdles in cancer therapeutics to date. The most advanced treatment option for mCRC patients are anti-epidermal growth factor receptor (EGFR) monoclonal antibodies (mAbs) that bind to and inhibit the activity of EGFR. While the use of anti-EGFR mABs has had great impact in the treatment of mCRC, it has now been widely accepted that mCRC tumors with a mutation in the small GTPase KRAS do not respond to these therapies. KRAS mutations allow for EGFR independent activation of various oncogenic signaling cascades. In attempts to inhibit KRAS mutant tumor growth, BRAF, MEK and farsenyltransferase inhibitors have been used, however, their clinical efficacy is still accruing in the setting of CRC. Recent data suggests that various other inhibitors, including inhibitors of Src family kinases (SFK) and hepatocyte growth factor receptor (MET), may have potential preclinical and clinical success in KRAS mutant tumors. Additionally, it is becoming increasingly clear that different KRAS missense mutations may have varied biological responses to cetuximab, suggesting that cetuximab may still be a potential therapeutic option in some KRAS mutant tumors. In this review, we highlight the importance for both improved multimodality approaches for treating KRAS mutant mCRC tumors and stratification of KRAS mutations in response to different treatment regimes in order to optimize the best possible care for mCRC patients.

Deoxyribozymes and bioinformatics: complementary tools to investigate axon regeneration

For over 100 years, scientists have tried to understand the mechanisms that lead to the axonal growth seen during development or the lack thereof during regeneration failure after spinal cord injury (SCI). Deoxyribozyme technology as a potential therapeutic to treat SCIs or other insults to the brain, combined with a bioinformatics approach to comprehend the complex protein-protein interactions that occur after such trauma, is the focus of this review. The reader will be provided with information on the selection process of deoxyribozymes and their catalytic sequences, on the mechanism of target digestion, on modifications, on cellular uptake and on therapeutic applications and deoxyribozymes are compared with ribozymes, siRNAs and antisense technology. This gives the reader the necessary knowledge to decide which technology is adequate for the problem at hand and to design a relevant agent. Bioinformatics helps to identify not only key players in the complex processes that occur after SCI but also novel or less-well investigated molecules against which new knockdown agents can be generated. These two tools used synergistically should facilitate the pursuit of a treatment for insults to the central nervous system.

Mice Lacking Ras-GRF1 Show Contextual Fear Conditioning but not Spatial Memory Impairments: Convergent Evidence from Two Independently Generated Mouse Mutant Lines

Ras-GRF1 is a neuronal specific guanine exchange factor that, once activated by both ionotropic and metabotropic neurotransmitter receptors, can stimulate Ras proteins, leading to long-term phosphorylation of downstream signaling. The two available reports on the behavior of two independently generated Ras-GRF1 deficient mouse lines provide contrasting evidence on the role of Ras-GRF1 in spatial memory and contextual fear conditioning. These discrepancies may be due to the distinct alterations introduced in the mouse genome by gene targeting in the two lines that could differentially affect expression of nearby genes located in the imprinted region containing the Ras-grf1 locus. In order to determine the real contribution of Ras-GRF1 to spatial memory we compared in Morris Water Maze learning Brambilla’s mice with a third mouse line (GENA53) in which a non-sense mutation was introduced in the Ras-GRF1 coding region without additional changes in the genome and we found that memory in this task is normal. Also, we measured both contextual and cued fear conditioning, which were previously reported to be affected in Brambilla’s mice, and we confirmed that contextual learning but not cued conditioning is impaired in both mouse lines. In addition, we also tested both lines for the first time in conditioned place aversion in the Intellicage, an ecological and remotely controlled behavioral test, and we observed normal learning. Finally, based on previous reports of other mutant lines suggesting that Ras-GRF1 may control body weight, we also measured this non-cognitive phenotype and we confirmed that both Ras-GRF1 deficient mutants are smaller than their control littermates. In conclusion, we demonstrate that Ras-GRF1 has no unique role in spatial memory while its function in contextual fear conditioning is likely to be due not only to its involvement in amygdala functions but possibly to some distinct hippocampal connections specific to contextual learning.

IgM-mediated autoimmune responses directed against multiple neoepitopes in depression: new pathways that underpin the inflammatory and neuroprogressive pathophysiology

BACKGROUND

There is evidence that depression is accompanied by oxidative and nitrosative stress (O&NS), as indicated by increased free radical levels, lipid peroxidation, and lowered antioxidant levels. The aims of the present study are to examine whether depression is accompanied by autoimmune responses directed against a) neoepitopes that are formed following O&NS damage; and b) the major anchorage molecules, i.e. palmitic and myristic acids and S-farnesyl-L-cysteine.

METHODS

We examined serum IgM antibodies to the conjugated fatty acids, palmitic and myristic acids; acetylcholine; S-farnesyl-L-cysteine; and NO-modified adducts in 26 depressed patients and 17 normal controls. Severity of depression was measured with the Hamilton Depression Rating Scale and severity of fatigue and somatic (F&S) symptoms with the Fibromyalgia and Chronic Fatigue Syndrome (FF) Rating Scale.

RESULTS

The prevalences and mean values for the serum IgM levels directed against conjugated palmitic and myristic acids, acetylcholine, S-farnesyl-L-cysteine; and the conjugated NO adducts, NO-tyrosine, NO-phenylalanine, NO-aspartate, NO-histidine, and NO-creatine were significantly higher in depressed patients than in normal controls. The autoimmune responses were significantly related to FF symptoms, such as fatigue and a flu-like malaise, whereas the indicants of nitrosative stress were related to gastro-intestinal and autonomic symptoms.

DISCUSSION

Depression is characterized by IgM-related autoimmune responses directed against a) neoepitopes that are normally not detected by the immune system but that due to damage by O&NS have become immunogenic; and b) anchorage epitopes, i.e. palmitic and myristic acids, and S-farnesyl-L-cysteine. These autoimmune responses play a role in the inflammatory and O&NS pathophysiology of depression and may mediate the cellular dysfunctions that contribute to neuroprogression, e.g. aberrations in signal transduction, cellular differentiation and apoptosis.

ARHGAP25, a novel Rac GTPase-activating protein, regulates phagocytosis in human neutrophilic granulocytes

Members of the Rac/Rho family of small GTPases play an essential role in phagocytic cells in organization of the actin cytoskeleton and production of toxic oxygen compounds. GTPase-activating proteins (GAPs) decrease the amount of the GTP-bound active form of small GTPases, and contribute to the control of biologic signals. The number of potential Rac/RhoGAPs largely exceeds the number of Rac/Rho GTPases and the expression profile, and their specific role in different cell types is largely unknown. In this study, we report for the first time the properties of full-length ARHGAP25 protein, and show that it is specifically expressed in hematopoietic cells, and acts as a RacGAP both in vitro and in vivo. By silencing and overexpressing the protein in neutrophil model cell lines (PLB-985 and CosPhoxFcγR, respectively) and in primary macrophages, we demonstrate that ARHGAP25 is a negative regulator of phagocytosis acting probably via modulation of the actin cytoskeleton.

Mammalian son of sevenless Guanine nucleotide exchange factors: old concepts and new perspectives

The Son of Sevenless (Sos) factors were originally discovered 2 decades ago as specialized Ras activators in signaling pathways controlling the process of R7 cell development in the eye of Drosophila melanogaster. The 2 known members of the mammalian Sos family (Sos1 and Sos2) code for ubiquitously expressed, highly homologous (69% overall) proteins involved in coupling signals originated by cell surface receptor tyrosine kinases (RTKs) to downstream, Ras-dependent mitogenic signaling pathways. Mechanistically, the Sos proteins function as enzymatic factors interacting with Ras proteins in response to upstream stimuli to promote guanine nucleotide exchange (GDP/GTP) and subsequent formation of the active Ras-GTP complex. In this review, we summarize current knowledge on structural, regulatory, and functional aspects of the Sos family, focusing on specific aspects of Sos biology such as structure-function relationship, crosstalk with different signaling pathways, and in vivo functional significance as deduced from phenotypic characterization of Sos knockout mice and human genetic syndromes caused by germline hSos1 mutations.

PDZ domains: the building blocks regulating tumorigenesis

Over 250 PDZ (PSD95/Dlg/ZO-1) domain-containing proteins have been described in the human proteome. As many of these possess multiple PDZ domains, the potential combinations of associations with proteins that possess PBMs (PDZ-binding motifs) are vast. However, PDZ domain recognition is a highly specific process, and much less promiscuous than originally thought. Furthermore, a large number of PDZ domain-containing proteins have been linked directly to the control of processes whose loss, or inappropriate activation, contribute to the development of human malignancies. These regulate processes as diverse as cytoskeletal organization, cell polarity, cell proliferation and many signal transduction pathways. In the present review, we discuss how PBM–PDZ recognition and imbalances therein can perturb cellular homoeostasis and ultimately contribute to malignant progression.

The heme oxygenase-1 protein is overexpressed in human renal cancer cells following activation of the Ras-Raf-ERK pathway and mediates anti-apoptotic signal

The stress-inducible cytoprotective enzyme heme oxygenase-1 (HO-1) may play a critical role in the growth and metastasis of tumors. We demonstrated that overexpressed HO-1 promotes the survival of renal cancer cells by inhibiting cellular apoptosis; we also showed that the proto-oncogene H-Ras becomes activated in these cells under stress following treatment with immunosuppressive agents. However, it is not known if there is an association between Ras activation and HO-1 overexpression. Here, we examined if the activation of H-Ras pathway could induce HO-1, and promote the survival of renal cancer cells (786-0 and Caki-1). In co-transfection assays, using HO-1 promoter-luciferase construct, we found that the activated H-Ras, H-Ras(12V), promoted HO-1 transcriptional activation. The inhibition of endogenous H-Ras by specific dominant-negative mutant/siRNA markedly ablated the HO-1 promoter activity. Active H-Ras increased HO-1 mRNA and protein expression. Moreover, transfection with effector domain mutant constructs of active H-Ras showed that H-Ras-induced HO-1 overexpression was primarily mediated through the Raf signaling pathway. Using pharmacological inhibitor, we observed that ERK is a critical intermediary molecule for Ras-Raf-induced HO-1 expression. Activation of H-Ras and ERK promoted nuclear translocation of the transcription factor Nrf2 for its binding to the specific sequence of HO-1 promoter. The knockdown of Nrf2 significantly inhibited H-Ras-induced HO-1 transcription. Finally, by FACS analysis using Annexin-V staining, we demonstrated that the H-Ras-ERK-induced and HO-1-mediated pathway could protect renal cancer cells from apoptosis. Thus, targeting the Ras-Raf-ERK pathway for HO-1 overexpression may serve as novel therapeutics for the treatment of renal cancer.

Roles of Ras1 membrane localization during Candida albicans hyphal growth and farnesol response

Many Ras GTPases localize to membranes via C-terminal farnesylation and palmitoylation, and localization regulates function. In Candida albicans, a fungal pathogen of humans, Ras1 links environmental cues to morphogenesis. Here, we report the localization and membrane dynamics of Ras1, and we characterize the roles of conserved C-terminal cysteine residues, C287 and C288, which are predicted sites of palmitoylation and farnesylation, respectively. GFP-Ras1 is localized uniformly to plasma membranes in both yeast and hyphae, yet Ras1 plasma membrane mobility was reduced in hyphae compared to that in yeast. Ras1-C288S was mislocalized to the cytoplasm and could not support hyphal development. Ras1-C287S was present primarily on endomembranes, and strains expressing ras1-C287S were delayed or defective in hyphal induction depending on the medium used. Cells bearing constitutively activated Ras1-C287S or Ras1-C288S, due to a G13V substitution, showed increased filamentation, suggesting that lipid modifications are differentially important for Ras1 activation and effector interactions. The C. albicans autoregulatory molecule, farnesol, inhibits Ras1 signaling through adenylate cyclase and bears structural similarities to the farnesyl molecule that modifies Ras1. At lower concentrations of farnesol, hyphal growth was inhibited but Ras1 plasma membrane association was not altered; higher concentrations of farnesol led to mislocalization of Ras1 and another G protein, Rac1. Furthermore, farnesol inhibited hyphal growth mediated by cytosolic Ras1-C288SG13V, suggesting that farnesol does not act through mechanisms that depend on Ras1 farnesylation. Our findings imply that Ras1 is farnesylated and palmitoylated, and that the Ras1 stimulation of adenylate cyclase-dependent phenotypes can occur in the absence of these lipid modifications.

A possible role for long non-coding RNA in modulating signaling pathways

Signaling proteins often engage in multiple protein-protein interactions that are dependent upon cellular context. Little is known about how signaling proteins select their interacting targets. The Ras GTPase is an example of a protein that can activate a large number of distinct and interconnected downstream signaling pathways. Hyperactive forms of Ras are commonly found in a variety of different cancers, often due to somatic mutations within the RAS gene. Despite extensive studies to identify Ras-regulated pathways, it is still not known exactly which pathways might be activated by hyperactive Ras in a given cellular and disease context. Long non-coding RNAs (lncRNAs) are RNA transcripts longer than 200 bp exhibiting spatially and temporally-regulated expression patterns. LncRNAs have been shown to harbor biological activities but the functions of the great majority of lncRNAs are not known. We hypothesize that long non-coding RNAs serve as signaling modulators linking Ras and potentially other signaling proteins to their specific downstream targets and may therefore play a key role in how signals are propagated in a specific cellular environment. In support of our hypothesis we argue that lncRNAs have been shown to bind and regulate protein complexes targeting their enzymatic activity towards specific substrates. It has also been demonstrated that specific lncRNAs are expressed in particular types of cancers where they may influence tumor progression. Studies suggest that lncRNAs have evolved to help regulate complex biological processes that require the ability to stringently discriminate between a large number of potential effectors. If our hypothesis is correct, we envision that it will be possible to predict the target pathway of a mutant protein based on the lncRNA profile in a specific cancer. More generally, this will expand our understanding of how signal transduction networks are wired within a given biological context.

p63RhoGEF couples Gα(q/11)-mediated signaling to Ca2+ sensitization of vascular smooth muscle contractility

RATIONALE

In normal and diseased vascular smooth muscle (SM), the RhoA pathway, which is activated by multiple agonists through G protein-coupled receptors (GPCRs), plays a central role in regulating basal tone and peripheral resistance. This occurs through inhibition of myosin light chain phosphatase, leading to increased phosphorylation of the myosin regulatory light chain. Although it is thought that specific agonists and GPCRs may couple to distinct RhoA guanine nucleotide exchange factors (GEFs), thus raising the possibility of selective targeting of specific GEFs for therapeutic use, this notion is largely unexplored for SM contraction.

OBJECTIVE

We examine whether p63RhoGEF, known to couple specifically to Gα(q/11) in vitro, is functional in blood vessels as a mediator of RhoA activation and if it is selectively activated by Gα(q/11) coupled agonists.

METHODS AND RESULTS

We find that p63RhoGEF is present across SM tissues and demonstrate that silencing of the endogenous p63RhoGEF in mouse portal vein inhibits contractile force induced by endothelin-1 to a greater extent than the predominantly Gα(12/13)-mediated thromboxane analog U46619. This is because endothelin-1 acts on Gα(q/11) as well as Gα(12/13). Introduction of the exogenous isolated pleckstrin-homology (PH) domain of p63RhoGEF (residues 331-580) into permeabilized rabbit portal vein inhibited Ca2+ sensitized force and activation of RhoA, when phenylephrine was used as an agonist. This reinforces the results based on endothelin-1, because phenylephrine is thought to act exclusively through Gα(q/11).

CONCLUSION

We demonstrate that p63RhoGEF selectively couples Gα(q/11) but not Gα(12/13), to RhoA activation in blood vessels and cultured cells and thus mediates the physiologically important Ca2+ sensitization of force induced with Gα(q/11)-coupled agonists. Our results suggest that signaling through p63RhoGEF provides a novel mechanism for selective regulation of blood pressure.

Recent advances in the pathogenesis and treatment of juvenile myelomonocytic leukaemia

Myeloid neoplasms derive from the pathological clonal expansion of an abnormal stem cell and span a diverse spectrum of phenotypes including acute myeloid leukaemia (AML), myeloproliferative neoplasms (MPN) and myelodysplastic syndromes (MDS). Expansion of myeloid blasts with suppression of normal haematopoiesis is the hallmark of AML, whereas MPN is associated with over-proliferation of one or more lineages that retain the capacity to differentiate, and MDS is characterized by cytopenias and aberrant differentiation. MPD and MDS can progress to AML, which is likely due to the acquisition of cooperative mutations. Juvenile myelomonocytic leukaemia (JMML) is an aggressive myeloid neoplasm of childhood that is clinically characterized by overproduction of monocytic cells that can infiltrate organs, including the spleen, liver, gastrointestinal tract, and lung. JMML is categorized as an overlap MPN/MDS by the World Health Organization and also shares some clinical and molecular features with chronic myelomonocytic leukaemia, a similar disease in adults. While the current standard of care for patients with JMML relies on allogeneic haematopoietic stem cell transplant (HSCT), relapse is the most frequent cause of treatment failure. This review outlines our understanding of the genetic underpinnings of JMML with a recent update on the discovery of novel CBL mutations, as well as a brief review on current therapeutic approaches.

Ras inhibition induces insulin sensitivity and glucose uptake

Background

Reduced glucose uptake due to insulin resistance is a pivotal mechanism in the pathogenesis of type 2 diabetes. It is also associated with increased inflammation. Ras inhibition downregulates inflammation in various experimental models. The aim of this study was to examine the effect of Ras inhibition on insulin sensitivity and glucose uptake, as well as its influence on type 2 diabetes development.

Methods and Findings

The effect of Ras inhibition on glucose uptake was examined both in vitro and in vivo. Ras was inhibited in cells transfected with a dominant-negative form of Ras or by 5-fluoro-farnesylthiosalicylic acid (F-FTS), a small-molecule Ras inhibitor. The involvement of IκB and NF-κB in Ras-inhibited glucose uptake was investigated by immunoblotting. High fat (HF)-induced diabetic mice were treated with F-FTS to test the effect of Ras inhibition on induction of hyperglycemia. Each of the Ras-inhibitory modes resulted in increased glucose uptake, whether in insulin-resistant C2C12 myotubes in vitro or in HF-induced diabetic mice in vivo. Ras inhibition also caused increased IκB expression accompanied by decreased expression of NF-κB . In fat-induced diabetic mice treated daily with F-FTS, both the incidence of hyperglycemia and the levels of serum insulin were significantly decreased.

Conclusions

Inhibition of Ras apparently induces a state of heightened insulin sensitization both in vitro and in vivo. Ras inhibition should therefore be considered as an approach worth testing for the treatment of type 2 diabetes.

Identification of H-Ras-specific motif for the activation of invasive signaling program in human breast epithelial cells

Increased expression and/or activation of H-Ras are often associated with tumor aggressiveness in breast cancer. Previously, we showed that H-Ras, but not N-Ras, induces MCF10A human breast epithelial cell invasion and migration, whereas both H-Ras and N-Ras induce cell proliferation and phenotypic transformation. In an attempt to determine the sequence requirement directing the divergent phenotype induced by H-Ras and N-Ras with a focus on the induction of human breast cell invasion, we investigated the structural and functional relationships between H-Ras and N-Ras using domain-swap and site-directed mutagenesis approaches. Here, we report that the hypervariable region (HVR), consisting of amino acids 166 to 189 in H-Ras, determines the invasive/migratory signaling program as shown by the exchange of invasive phenotype by swapping HVR sequences between H-Ras and N-Ras. We also demonstrate that the H-Ras-specific additional palmitoylation site at Cys184 is not responsible for the signaling events that distinguish between H-Ras and N-Ras. Importantly, this work identifies the C-terminal HVR, especially the flexible linker domain with two consecutive proline residues Pro173 and Pro174, as a critical domain that contributes to activation of H-Ras and its invasive potential in human breast epithelial cells. The present study sheds light on the structural basis for the Ras isoform-specific invasive program of breast epithelial cells, providing information for the development of agents that specifically target invasion-related H-Ras pathways in human cancer.

Sodium benzoate, a metabolite of cinnamon and a food additive, upregulates neuroprotective Parkinson disease protein DJ-1 in astrocytes and neurons

DJ-1 (PARK7) is a neuroprotective protein that protects cells from oxidative stress. Accordingly, loss-of-function DJ-1 mutations have been linked with a familial form of early onset Parkinson disease. Mechanisms by which DJ-1 level could be enriched in the CNS are poorly understood. Recently we have discovered anti-inflammatory activity of sodium benzoate (NaB), a metabolite of cinnamon and a widely-used food additive. Here we delineate that NaB is also capable of increasing the level of DJ-1 in primary mouse and human astrocytes and human neurons highlighting another novel neuroprotective effect of this compound. Reversal of DJ-1-inducing effect of NaB by mevalonate, farnesyl phosphate, but not cholesterol and ubiquinone, suggests that depletion of intermediates, but not end products, of the mevalonate pathway is involved in the induction of DJ-1 by NaB. Accordingly, either an inhibitor of p21(ras) farnesyl protein transferase (FPTI) or a dominant-negative mutant of p21(ras) alone was also able to increase the expression of DJ-1 in astrocytes suggesting an involvement of p21(ras) in DJ-1 expression. However, an inhibitor of geranyl geranyl transferase (GGTI) and a dominant-negative mutant of p21(rac) had no effect on the expression of DJ-1, indicating the specificity of the effect. Similarly lipopolysaccharide (LPS), an activator of small G proteins, also inhibited the expression of DJ-1, and NaB and FPTI, but not GGTI, abrogated LPS-mediated inhibition. Together, these results suggest that NaB upregulates DJ-1 via modulation of mevalonate metabolites and that p21(ras), but not p21(rac), is involved in the regulation of DJ-1.

The participation of calponin in the cross talk between 20-hydroxyecdysone and juvenile hormone signaling pathways by phosphorylation variation

20-hydroxyecdysone (20E) and juvenile hormone (JH) signaling pathways interact to mediate insect development, but the mechanism of this interaction is poorly understood. Here, a calponin homologue domain (Chd) containing protein (HaCal) is reported to play a key role in the cross talk between 20E and JH signaling by varying its phosphorylation. Chd is known as an actin binding domain present in many proteins including some signaling proteins. Using an epidermal cell line (HaEpi), HaCal was found to be up-regulated by either 20E or the JH analog methoprene (JHA). 20E induced rapid phosphorylation of HaCal whereas no phosphorylation occurred with JHA. HaCal could be quickly translocated into the nuclei through 20E or JH signaling but interacted with USP1 only under the mediation of JHA. Knockdown of HaCal by RNAi blocked the 20E inducibility of USP1, PKC and HR3, and also blocked the JHA inducibility of USP1, PKC and JHi. After gene silencing of HaCal by ingestion of dsHaCal expressed by Escherichia coli, the larval development was arrested and the gene expression of USP1, PKC, HR3 and JHi were blocked. These composite data suggest that HaCal plays roles in hormonal signaling by quickly transferring into nucleus to function as a phosphorylated form in the 20E pathway and as a non-phosphorylated form interacting with USP1 in the JH pathway to facilitate 20E or JH signaling cascade, in short, by switching its phosphorylation status to regulate insect development.

Computational model of EGFR and IGF1R pathways in lung cancer: a Systems Biology approach for Translational Oncology

In this paper we propose a Systems Biology approach to understand the molecular biology of the Epidermal Growth Factor Receptor (EGFR, also known as ErbB1/HER1) and type 1 Insulin-like Growth Factor (IGF1R) pathways in non-small cell lung cancer (NSCLC). This approach, combined with Translational Oncology methodologies, is used to address the experimental evidence of a close relationship among EGFR and IGF1R protein expression, by immunohistochemistry (IHC) and gene amplification, by in situ hybridization (FISH) and the corresponding ability to develop a more aggressive behavior. We develop a detailed in silico model, based on ordinary differential equations, of the pathways and study the dynamic implications of receptor alterations on the time behavior of the MAPK cascade down to ERK, which in turn governs proliferation and cell migration. In addition, an extensive sensitivity analysis of the proposed model is carried out and a simplified model is proposed which allows us to infer a similar relationship among EGFR and IGF1R activities and disease outcome.

Triggering Ras signalling by intracellular Francisella tularensis through recruitment of PKCα and βI to the SOS2/GrB2 complex is essential for bacterial proliferation in the cytosol

Intracellular proliferation of Francisella tularensis is essential for manifestation of the fatal disease tularaemia, and is classified as a category A bioterrorism agent. The F. tularensis-containing phagosome (FCP) matures into a late endosome-like phagosome with limited fusion to lysosomes, followed by rapid bacterial escape into the cytosol. The Francisella pathogenicity island (FPI) encodes a type VI-like secretion system, and the FPI-encoded IglC is essential for evasion of lysosomal fusion and phagosomal escape. Many host signalling events are likely to be modulated by F. tularensis to render the cell permissive for intracellular proliferation but they are not fully understood. Here we show that within 15 min of infection, intracellular F. tularensis ssp. novicida triggers IglC-dependent temporal activation of Ras, but attached extracellular bacteria fail to trigger Ras activation, which has never been shown for other intracellular pathogens. Intracellular F. tularensis ssp. novicida triggers activation of Ras through recruitment of PKCα and PKCβI to the SOS2/GrB2 complex. Silencing of SOS2, GrB2 and PKCα and PKCβI by RNAi has no effect on evasion of lysosomal fusion and bacterial escape into the cytosol but renders the cytosol non-permissive for replication of F. tularensis ssp. novicida. Since Ras activation promotes cell survival, we show that silencing of SOS2, GrB2 and PKCα and βI is associated with rapid early activation of caspase-3 within 8 h post infection. However, silencing of SOS2, GrB2 and PKCα and βI does not affect phosphorylation of Akt or Erk, indicating that activation of the PI3K/Akt and the Erk signalling cascade are independent of the F. tularensis-triggered Ras activation. We conclude that intracellular F. tularensis ssp. novicida triggers temporal and early activation of Ras through the SOS2/GrB2/PKCα/PKCβI quaternary complex. Temporal and rapid trigger of Ras signalling by intracellular F. tularensis is essential for intracellular bacterial proliferation within the cytosol, and this is associated with downregulation of early caspase-3 activation.

Novel nitric oxide-releasing derivatives of farnesylthiosalicylic acid: synthesis and evaluation of antihepatocellular carcinoma activity

Novel furoxan-based nitric oxide (NO) releasing derivatives (8a-p) of farnesylthiosalicylic acid (FTS) were synthesized. Compound 8l displayed the strongest inhibition on the proliferation of human hepatocellular carcinoma (HCC) cells in vitro, superior to FTS, sorafenib, and furoxan moiety, selectively induced high frequency of HCC cell apoptosis, and produced high levels of NO in HCC cells but not in nontumor liver cells. Furthermore, 8l exhibited low acute toxicity to mice and significantly inhibited the growth of HCC tumors in vivo and the Ras-related signaling in the tumors. Therefore, our novel findings may provide a new framework for the design of new NO-releasing furoxan/FTS hybrids for the intervention of human HCC.

Concordance and interaction of guanine nucleotide dissociation inhibitor (RhoGDI) with RhoA in oogenesis and early development of the sea urchin

Rho GTPases are Ras-related GTPases that regulate a variety of cellular processes. In the sea urchin Strongylocentrotus purpuratus, RhoA in the oocyte associates with the membrane of the cortical granules and directs their movement from the cytoplasm to the cell cortex during maturation to an egg. RhoA also plays an important role regulating the Na(+) -H(+) exchanger activity, which determines the internal pH of the cell during the first minutes of embryogenesis. We investigated how this activity may be regulated by a guanine-nucleotide dissociation inhibitor (RhoGDI). The sequence of this RhoA regulatory protein was identified in the genome on the basis of its similarity to other RhoGDI species, especially for key segments in the formation of the isoprenyl-binding pocket and in interactions with the Rho GTPase. We examined the expression and the subcellular localization of RhoGDI during oogenesis and in different developmental stages. We found that RhoGDI mRNA levels were high in eggs and during cleavage divisions until blastula, when it disappeared, only to reappear in gastrula stage. RhoGDI localization overlaps the presence of RhoA during oogenesis and in embryonic development, reinforcing the regulatory premise of the interaction. By use of recombinant protein interactions in vitro, we also find that these two proteins selectively interact. These results support the hypothesis of a functional relationship in vivo and now enable mechanistic insight for the cellular and organelle rearrangements that occur during oogenesis and embryonic development.

Structural study of the Cdc25 domain from Ral-specific guanine-nucleotide exchange factor RalGPS1a

The guanine-nucleotide exchange factor (GEF) RalGPS1a activates small GTPase Ral proteins such as RalA and RalB by stimulating the exchange of Ral bound GDP to GTP, thus regulating various downstream cellular processes. RalGPS1a is composed of an Nterminal Cdc25-like catalytic domain, followed by a PXXP motif and a C-terminal pleckstrin homology (PH) domain. The Cdc25 domain of RalGPS1a, which shares about 30% sequence identity with other Cdc25-domain proteins, is thought to be directly engaged in binding and activating the substrate Ral protein. Here we report the crystal structure of the Cdc25 domain of RalGPS1a. The bowl shaped structure is homologous to the Cdc25 domains of SOS and RasGRF1. The most remarkable difference between these three Cdc25 domains lies in their active sites, referred to as the helical hairpin region. Consistent with previous enzymological studies, the helical hairpin of RalGPS1a adopts a conformation favorable for substrate binding. A modeled RalGPS1a-RalA complex structure reveals an extensive binding surface similar to that of the SOS-Ras complex. However, analysis of the electrostatic surface potential suggests an interaction mode between the RalGPS1a active site helical hairpin and the switch 1 region of substrate RalA distinct from that of the SOS-Ras complex.