A Systematic Review of Electrophysiological Findings in Binge-Purge Eating Disorders: A Window Into Brain Dynamics

Binge-purge eating disorders (BP-ED), such as bulimia nervosa and binge eating disorder, may share some neurobiological features. Electroencephalography (EEG) is a non-invasive measurement modality that may aid in research and diagnosis of BP-ED. We conducted a systematic review of the literature on EEG findings in BP-ED, seeking to summarize and analyze the current evidence, as well as identify shortcomings and gaps to inform new perspectives for future studies. Following PRISMA Statement recommendations, the PubMed, Embase, and Web of Science databases were searched using terms related to “electroencephalography” and “binge-purge” eating disorders. Of 555 articles retrieved, 15 met predefined inclusion criteria and were included for full-text analysis. Eleven studies investigated EEG by means of event-related potentials (ERP) in BP-ED individuals: 7 using eating disorder-related stimuli (i.e., food, body image) and 4 using non-eating disorder-related stimuli (i.e., facial expressions or auditory clicks). These studies found significant differences in the N200, P200, P300, and LPP components in BP-ED participants compared to controls, indicating that this population exhibits impairments in selective attention, attentional allocation/processing, and allocation of motivational or emotion-based attention. Five studies investigated EEG using frequency analysis; reporting significant differences in beta activity in fronto-temporal and occipito-temporo-parietal areas in BP-ED individuals compared to controls, revealing a dysfunctional brain network. However, the small number of studies, the heterogeneity of samples, study paradigms, stimulus types, and the lack of an adequate assessment of neuropsychological parameters are some limitations of the current literature. Although some EEG data are promising and consistent with neuroimaging and neuropsychological findings in individuals with BP-ED, future studies need to overcome current methodological shortcomings.

STochastic Optical Reconstruction Microscopy (STORM) reveals the nanoscale organization of pathological aggregates in human brain

AIMS

Histological analysis of brain tissue samples provides valuable information about the pathological processes leading to common neurodegenerative disorders. In this context, the development of novel high-resolution imaging approaches is a current challenge in neuroscience.

METHODS

To this end, we used a recent super-resolution imaging technique called STochastic Optical Reconstruction Microscopy (STORM) to analyse human brain sections. We combined STORM cell imaging protocols with neuropathological techniques to image cryopreserved brain samples from control subjects and patients with neurodegenerative diseases.

RESULTS

This approach allowed us to perform 2D-, 3D- and two-colour-STORM in neocortex, white matter and brainstem samples. STORM proved to be particularly effective at visualizing the organization of dense protein inclusions and we imaged with a <50 nm resolution pathological aggregates within the central nervous system of patients with Alzheimer's disease, Parkinson's disease, Lewy body dementia and fronto-temporal lobar degeneration. Aggregated Aβ branches appeared reticulated and cross-linked in the extracellular matrix, with widths from 60 to 240 nm. Intraneuronal Tau and TDP-43 inclusions were denser, with a honeycomb pattern in the soma and a filamentous organization in the axons. Finally, STORM imaging of α-synuclein pathology revealed the internal organization of Lewy bodies that could not be observed by conventional fluorescence microscopy.

CONCLUSIONS

STORM imaging of human brain samples opens further gates to a more comprehensive understanding of common neurological disorders. The convenience of this technique should open a straightforward extension of its application for super-resolution imaging of the human brain, with promising avenues to current challenges in neuroscience.

Antibody- and macrophage-mediated segmental demyelination in chronic inflammatory demyelinating polyneuropathy: clinical, electrophysiological, immunological and pathological correlates

BACKGROUND AND PURPOSE

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is a heterogeneous autoimmune disorder critically lacking diagnostic biomarkers. Autoantibodies to nodal and paranodal components have recently been described in a small subset of patients. Here, the diagnostic value of immune reactivity toward the myelin compartment was investigated.

METHODS

Ninety-four French CIDP patients were retrospectively studied. The reactivity toward the peripheral nerve was investigated. Sural nerve biopsies were examined by electron microscopy and immunofluorescence.

RESULTS

Twenty-one patients (22%) and three patients (3%) presented with a strong immunoglobulin G or immunoglobulin M reactivity respectively against the myelin compartment. The clinical, electrophysiological and morphological features were examined in nine of these patients for whom sural nerve biopsies were available. Seven patients were electrodiagnosed with definite CIDP, one with possible CIDP and one was unclassifiable but sural nerve biopsy argued for CIDP diagnosis. Electron microscopy of sural nerve biopsies demonstrated the presence of macrophage-mediated demyelination restricted to the internode in all nine patients. Immunolabelling for voltage-gated sodium channels, myelin and axonal markers confirmed the presence of segmental demyelination and of remyelination. The nodal and paranodal regions, however, were unaffected in these patients. Nerve conduction studies corroborated the multifocal and segmental profile, and seven patients showed increased duration of proximal (1.5-5.1 times) and/or distal (1.2-3.4 times) compound muscle action potential in at least two nerves.

CONCLUSION

Antibody- and macrophage-mediated demyelination appears responsible for conduction alterations in CIDP patients and nerve immunostaining assays may serve as a supportive diagnostic biomarker.

ADHD Rate in Obese Women With Binge Eating and Bulimic Behaviors From a Weight-Loss Clinic

OBJECTIVE

Few studies have demonstrated a possible association between ADHD and obesity in adults. The aim of this study was to investigate the prevalence of ADHD in a sample of obese women seeking treatment, and its relations with binge eating and bulimic behaviors.

METHOD

We performed a cross-sectional study in a clinical sample of one hundred fifty-five women, with a mean age of 38.9 (+10.7) years and a mean body mass index (BMI) of 39.2 (+5.29). Participants were evaluated with semistructured interviews and completed self-report psychiatric rating scales.

RESULTS

The rate of ADHD in the sample was of 28.3%. The presence of ADHD was significantly correlated with more severe binge eating, bulimic behaviors, and depressive symptomatology.

CONCLUSION

Similar to previous studies, a higher than expected rate of ADHD was observed among obese women. ADHD in obese individuals may be a risk factor for greater severity of disordered eating patterns.

Health Impact of Adverse Childhood Experiences Among Youths in Custody: The Significant Contribution of Sexual Abuse

BACKGROUND: Growing evidence suggests a graded relationship between adverse childhood experiences (ACE) and unfavorable health outcomes as early as in the teenage years. Youths under the welfare protection system represent an especially vulnerable group - presenting traumatic personal trajectory while cumulating family related-risk factors. Among early life adversities, specific experience might have a greatest contribution on the long-term health-risk.

OBJECTIVES: The objective of this analysis is to evaluate the contribution of sexual abuse as compare to other ACEs on different health issues in adolescent under court custody.

DESIGN/METHODS: This is a secondary analysis from a cross-sectional health evaluation study of youths in custodial facilities (2011-13). A total of 315 teenagers 14-17 y.o. (134 girls, 181 boys) completed a self-reported questionnaire about their health status and were then evaluated by a nurse/ doctor using a comprehensive standardized data collection checklist. We identified 8 ACEs: (1) single family; (2) violent death of family member; family history of (3) incarceration, (4) mental health issues, (5) substance abuse; personal history of (6) intrafamilial or (7) extrafamilial physical abuse; personal history of (8) sexual abuse. Multiple and logistic regression were performed between the ACEs and a number of relevant variables.

RESULTS: A personal history of sexual abuse was the most consistant ACE predicting negative health outcomes including perceived health status (R2=0.04; p=0.05), number of health problems identified / acute or chronic (p=0.00), psychosomatic complaints (R2=0.12; p=0.00), sleeping problems (OR=2.8; p=0.005), medication (OR=3.5; p=0.01). This trauma was also the most important factor for high-risk sexuality items evaluated: number of sexuality-related problems in girls (R2=0.15; p=0.00), vaginal sex before 13 y.o. (OR=1.8; p=0.48), number of partners (R2=0.04; p=0.03), sex work (OR=9.6; p=0.00), fear of STI (OR=3.2; p=0.001), as it was for mental health issues: mental health disorders (OR=4.3; p=0.00), suicidal ideation (OR=4.0; p=0.00), suicidal attempt (OR=3.6; p=0.00), self-inflicting injuries (R2=0.12 ; p = 0.01), depression (R2=0.08 ; p=0.00), low self-esteem (R2=0.07; p=0.00) and overdose (OR=2.1; p=0.02).

CONCLUSION: Among ACEs, a personal history of sexual abuse seems to be the most contributing factor for significant health outcomes. Some traumatic or adverse childhood events have a greater burden on subsequent health-risk. A simple question could help identified those at higher risk and higher needs for health services in teens under custody.

Influence of attention-deficit/hyperactivity disorder on binge eating behaviors and psychiatric comorbidity profile of obese women

OBJECTIVE

Previous studies have reported higher prevalence rates of attention-deficit/hyperactivity disorder (ADHD) both in eating disorders (ED) and in obese patients. We compared the psychiatric comorbidity profile of obese ADHD women with non-ADHD obese women and how ADHD symptoms impact in binge eating behaviors.

DESIGN

Cross-sectional study of a clinical sample.

SUBJECTS

171 adult women were evaluated at a specialized clinic in obesity and ED.

MEASUREMENTS

Participants complete a semi-structured interview and psychopathology rating scales. A hierarchical regression model was employed to predict binge eating behavior.

RESULTS

Obese ADHD patients had a larger number of psychiatric comorbidities (p<0.001), especially Substance Abuse Disorders, and higher scores on psychopathology rating scales (p<0.05). The highest prediction for binge eating in the regression model was the presence of depressive symptoms, followed by ADHD inattention symptoms and trait-impulsivity.

CONCLUSION

ADHD should be routinely evaluated in obese since it is related with more severe psychopathology. Depressive symptoms can predict the presence of binge eating in obese patients.

The association between quality of life, depressive symptoms and glycemic control in a group of type 2 diabetes patients

AIMS

Several studies have demonstrated worse perception of quality of life (QoL) among patients with type 2 diabetes mellitus (T2DM). The purpose of our study was to assess QoL in a clinical sample of patients with T2DM and its association with depressive symptoms and glycemic control.

METHODS

One hundred outpatients from a sequential sample underwent clinical and psychiatric evaluation. The Problem Areas of Diabetes scale (PAID) and the Beck Depression Inventory (BDI) were used to assess, respectively, QoL and the presence of overall psychopathology. The levels of glycated hemoglobin (HbA1c) were used as the main parameter of glycemic control.

RESULTS

The perception degree of the QoL related with diabetes was associated with the severity of depressive symptoms (r=0.503; p<0.001), but not with HbA1c levels (p=0.117). However, the severity of general psychopathology, evaluated through the BDI scores, predicted the metabolic control, measured by HbA1c levels, among the patients in our sample (r=0.233; p=0.019).

CONCLUSIONS

In our study, PAID was a valuable tool for the evaluation of QoL in T2DM and the screening of depressive symptoms. However, no correlation observed between PAID scores and HbA1c levels. Self-perception evaluation of T2DM patient can help to identify susceptible subjects to current depression.

Review of literature of attention-deficit/hyperactivity disorder with comorbid eating disorders

OBJECTIVE: According to studies of prevalence, up to 70% of adults with attention deficit/hyperactivity disorder have at least one psychiatric comorbidity, which leads to diagnostic and therapeutic difficulties as well as more severe functional impairment. There is a paucity of data on the comorbidity of attention deficit/hyperactivity disorder and eating disorders. The objective of this study was to review the literature regarding the attention deficit/hyperactivity disorder/eating disorders comorbidity, performing a critical analysis of relevant data. METHOD: Articles in Medline, Lilacs, SciELO, ISI and PsycINFO databases from 1980 up to 2008, were searched. The references from the articles were used as additional sources of data. RESULTS: Fourteen articles were found: five prevalence studies, four case reports, three case-control studies, one symptom-assessment study of attention deficit/hyperactivity disorder and eating disorders, and one article regarding possible causes of the association between attention deficit/hyperactivity disorder and eating disorders. These articles suggested that adult women with attention deficit/hyperactivity disorder are at higher risk of developing eating disorders, especially bulimia nervosa. Bulimia Nervosa rates found in attention deficit/hyperactivity disorder groups ranged from 1% to 12%, versus 0% to 2% in control groups. CONCLUSIONS: Although there seems to be a relationship between attention deficit/hyperactivity disorder and eating disorders, the reduced number of studies available, with various methodologies, and small sample sizes limit the generalization of the findings.

Double-blind, randomized, placebo-controlled trial of topiramate plus cognitive-behavior therapy in binge-eating disorder

OBJECTIVE

To evaluate the efficacy and tolerability of adjunctive topiramate compared to placebo in reducing weight and binge eating in obese patients with binge-eating disorder (BED) receiving cognitive-behavior therapy (CBT).

METHOD

A double-blind, randomized, placebo-controlled trial of 21 weeks' duration was conducted at 4 university centers. Participants were 73 obese (body mass index >or= 30 kg/m(2)) outpatients with BED (DSM-IV criteria), both genders, and aged from 18 to 60 years. After a 2- to 5-week run-in period, selected participants were treated with group CBT (19 sessions) and topiramate (target daily dose, 200 mg) or placebo (September 2003-April 2005). The main outcome measure was weight change, and secondary outcome measures were binge frequencies, binge remission, Binge Eating Scale (BES) scores, and Beck Depression Inventory (BDI) scores.

RESULTS

Repeated-measures random regression analysis revealed a greater rate of weight reduction associated with topiramate over the course of treatment (p < .001), with patients taking topiramate attaining a clinically significant weight loss (-6.8 kg) compared to patients taking placebo (-0.9 kg). Although rates of reduction of binge frequencies, BES scores, and BDI scores did not differ between groups during treatment, a greater number of patients of the topiramate plus CBT group (31/37) attained binge remission compared to patients taking placebo (22/36) during the trial (p = .03). No difference between groups was found in completion rates; 1 patient (topiramate group) withdrew for adverse effect. Paresthesia and taste perversion were more frequent with topiramate, and insomnia was more frequent with placebo (p < .05).

CONCLUSIONS

Topiramate added to CBT improved the efficacy of the later, increasing binge remission and weight loss in the short run. Topiramate was well tolerated, as shown by few adverse events during treatment.

CLINICAL TRIALS REGISTRATION

ClinicalTrials.gov identifier NCT00307619.

Transtornos alimentares comórbidos em uma amostra clínica de adultos com transtorno do déficit de atenção com hiperatividade

A comorbidade de transtornos alimentares (TA) com o transtorno do déficit de atenção com hiperatividade (TDAH) é pouco investigada, apesar de relevante para o tratamento clínico. MÉTODOS: 86 adultos com transtorno do déficit de atenção com hipeartividade segundo o DSM-IV de uma amostra inicial de 107 indivíduos auto-referidos para um centro especializado em TDAH foram entrevistados com o SCID-P para avaliar a presença de transtornos alimentares e outros transtornos comórbidos. RESULTADOS: Nove pacientes apresentavam transtornos alimentares, sendo o transtorno da compulsão alimentar periódica (TCAP) o diagnóstico mais comum. O grupo com transtornos alimentares revelou maior número de comorbidades (p=0,02), não foram observadas, entretanto, diferenças quanto ao sexo, idade na avaliação atual, escolaridade e tipo de transtorno do déficit de atenção com hiperatividade entre os grupos. CONCLUSÃO: Amostras clínicas de transtorno do déficit de atenção com hiperatividade podem apresentar elevada prevalência de comorbidade com transtorno da compulsão alimentar periódica. Pacientes com transtorno do déficit de atenção com hiperatividade e transtornos alimentares podem apresentar um perfil diferente de comorbidades.

Neuropsicologia dos transtornos alimentares: revisão sistemática da literatura

ANTECEDENTES: A etiologia dos transtornos alimentares (TA) ainda não se encontra estabelecida. Dentre os diversos fatores envolvidos, a hipótese de uma disfunção do sistema nervoso central tem sido explorada de diversas maneiras. Assim, a avaliação neuropsicológica de pacientes com TA tem por finalidade investigar a ocorrência de déficits cognitivos associados a estas patologias. OBJETIVOS: O objetivo deste artigo é avaliar o estado atual das investigações sobre a avaliação neuropsicológica em pacientes com TA. MÉTODOS: Foi realizada uma pesquisa bibliográfica - utilizando as seguintes bases de dados como estratégias de procura: MedLINE, PsychoINFO, LILACS e Cochrane Data Bank -, procurando artigos relacionados ao tema e publicados até o ano de 2004. RESULTADOS: A anorexia nervosa é o transtorno alimentar que conta com mais estudos neuropsicológicos e, de uma forma geral, os resultados apontam para déficits de atenção, déficits viso-espaciais e de viso-construção. Na bulimia nervosa, as alterações mais encontradas são déficits de atenção seletiva e das funções executivas. O transtorno da compulsão alimentar periódica ainda não conta com estudos neuropsicológicos até o momento. Após um tratamento bem-sucedido do transtorno alimentar, embora haja uma diminuição dos déficits cognitivos, algumas alterações cognitivas parecem persistir. CONCLUSÕES: Os transtornos alimentares parecem estar associados a algum grau de disfunção neuropsicológica, muito embora as funções específicas que se apresentam deficitárias variem entre os estudos encontrados, talvez em decorrência de variações metodológicas. O fato de que, após o tratamento, alguns pacientes apresentem uma melhora no funcionamento cognitivo poderia indicar que, em alguns casos, os déficits seriam funcionais. A ausência de melhora no funcionamento cognitivo de alguns pacientes, após diversas formas de intervenção, pode sugerir que estes déficits antecederiam o desenvolvimento dos transtornos alimentares, podendo, assim, contribuir para seu desenvolvimento ou para um pior prognóstico. O melhor delineamento do perfil cognitivo dos pacientes com transtorno alimentar torna-se importante para orientar abordagens terapêuticas mais seletivas.

Polypeptide composition of an adenovirus type 5 used in cancer gene therapy

For cancer gene therapy, a recombinant adenovirus serotype 5 named RPR/INGN201 has been constructed by susbtitution of the E1 region with human tumor suppressor gene p53. The protein components of RPR/INGN201 virions were separated by reversed-phase HPLC and were individually identified by electrospray time-of-flight mass spectrometry and N-terminal sequencing, both on intact proteins and on their proteolytic fragments after trypsin digestion. Twenty-five peptide components of the proteome (including fiber) with greater than 0.25-0.5% contribution to the protein content of the virus were identified and characterized. Fiber was confirmed to be partially glycosylated (both the non-glycosylated and the monoglycosylated states were identified), and two proteins were isolated and identified as phosphorylation derivatives, namely protein V (non-phosphorylated and monophosphorylated) and protein IIIa (mono- and diphosphorylated). This new analytical tool proved to be very useful not only for refining our current knowledge of the polypeptide repertoire of purified infectious virions but also for monitoring and very rapidly identifying structural modifications resulting from changes in the manufacturing process. It was also used successfully for the characterization of various adenoviral constructs.

The up-regulation of vascular endothelial growth factor in mutated Ha-ras HaCaT cell lines is reduced by a farnesyl transferase inhibitor

The induction of tumor angiogenesis is mediated in particular by an increased production of VEGF. As ras oncogene is implicated in tumorigenesis, the inhibition of farnesyl transferase activity has recently been developed. The purpose of this study was to evaluate whether expression of mutated Ha-ras oncogene is associated with an altered expression of VEGF in an in vitro model of human skin carcinogenesis and to appreciate the effect of a new farnesyl transferase inhibitor on this VEGF expression. The amounts of VEGF secreted by an HaCaT cell line and two cell clones (metastatic or not) obtained after mutated c-Ha-ras transfection were compared. Our findings showed that the release of VEGF is greater for HaCaT-ras than for HaCaT cells and could be down-regulated using a protein farnesyl transferase inhibitor, in a reversible and dose-dependent manner. These results confirm that the Ha-ras oncogene can contribute to tumor development and progression of epidermal tumors through neoangiogenesis and that farnesyl transferase inhibitors as anticancer drugs may be efficient for the reduction of skin tumor growth.

Intracellular expression and functional properties of an anti-p21Ras scFv derived from a rat hybridoma containing specific lambda and irrelevant kappa light chains

A rat single-chain Fv (Y238 scFv) was derived from the Y13-238 monoclonal antibody, a non-neutralizing anti-Ras antibody. The Y13-238 hybridoma expresses two functional light chains. N-terminus microsequencing of these chains showed the presence of the Y3 Ag1.2.3 Vkappa chain derived from the rat fusion partner and of a rat Vlambda chain. Primers designed for rat Vlambda amplification allowed the cloning of a functional scFv that could bind p21Ras. The kinetics of interaction of purified Y238 scFv with the p21Ras protein was evaluated by BIAcore with a NTA sensor chip and gave an apparent affinity constant in the nanomolar range (K(D)=4.58+/-0.63 nM). Immunoprecipitation experiments of Y238 scFv expressed in Xenopus laevis oocytes confirmed the specificity of the scFv for the Ras protein. Y238 scFv could be intracellularly expressed in oocytes and in mammaliam cells without adverse effect on the Ras signalling cascade. This scFv was therefore used as control in experiments where another anti-Ras scFv (Y259 scFv, derived from the neutralizing anti-Ras mAb Y13-259) blocked the Ras pathway in vitro and led to tumor regression in a nude mouse model [Cochet, O., Kenigsberg, M., Delumeau, I., Virone-Oddos, A., Multon, M.C., Fridman, W.H., Schweighoffer, F., Teillaud, J.L., Tocqué, B., 1998. Intracellular expression of an antibody fragment-neutralizing p21 ras promotes tumor regression. Cancer Res. 58, 1170-1176.]. Finally, BIAcore analyses indicated that the epitopes recognized by Y238 and Y259 scFvs are not overlapping and allowed a more precise definition of the Y13-238 epitope.

Differential interactions of the growth factor receptor-bound protein 2 N-SH3 domain with son of sevenless and dynamin. Potential role in the Ras-dependent signaling pathway

In this paper, we show that the 36-45 surface-exposed sequence WYKAELNGKD of growth factor receptor-bound protein 2 (Grb2) N-SH3 domain inhibits the interaction between Grb2 and a 97-kDa protein identified as dynamin. Moreover, the peptide GPPPQVPSRPNR from dynamin also blocks the binding of dynamin to the proline-rich recognition platform of Grb2. Mutations in the 36-45 motif show that Glu-40 is critical for dynamin recognition. These observations were confirmed by immunoprecipitation experiments, carried out using ER 22 cells. It was also observed that the proline-rich peptide from dynamin was unable to dissociate the Grb2.Sos complex, whereas the proline-rich peptide from Son of sevenless (Sos) inhibited Grb2. dynamin interaction. A time-dependent stimulation of epidermal growth factor receptor overexpressing clone 22 (ER 22) cells by epidermal growth factor resulted in an immediate increase of the Grb2.Sos complex and a concomitant decrease in Grb2.dynamin. This suggests that the recruitment of Grb2.Sos to the membrane, triggered by epidermal growth factor stimulation, activates the Ras-dependent signaling and simultaneously enhances free dynamin levels, leading to both receptor internalization and endocytotic processes.

[Normalization of a computerized visual attention test (TAVIS)]

The authors present the normative data of a computerized test (TAVIS) that address visual attention in children and adolescents being the first neuropsychological instrument as such devised and developed in Brazil. Selective, alternate and sustained attention aspects are evaluated through three different tasks. Omission and action errors as well as time reaction are evaluated. The advantages and limitations of the test are commented.

A role for Sam68 in cell cycle progression antagonized by a spliced variant within the KH domain

Sam68 is the main tyrosine-phosphorylated and Src-associated protein in mitotic cells. Sam68 exhibits a conserved functional KH (hnRNPK homology) RNA binding domain and binds single strand nucleic acids. Tyrosine phosphorylation mediates the interaction of Sam68 with many SH3- and SH2-containing proteins and negatively regulates its nucleic acid binding properties. But the function and the impact of Sam68 on cell signaling and cell proliferation remains elusive. We report here the identification of a natural isoform of Sam68 with a deletion within the KH domain. This isoform, called Sam68DeltaKH, is specifically expressed at growth arrest upon confluency in normal cells. In cells that do not enter quiescence at confluency such as Src-transformed cells, no recruitment of Sam68DeltaKH is observed. Transfected Sam68DeltaKH inhibits serum-induced DNA synthesis and cyclin D1 expression. Sam68 overcomes these effects, suggesting that isoforms of Sam68 are involved, through KH domain signaling, in cell proliferation, and more precisely in G1/S transition.

Synthesis and conformational analysis of peptide inhibitors of farnesyltransferase

Farnesylation of the ras oncogene product by Farnesyl Transferase (FTase) is known to be a critical step in cell transformation leading to uncontrolled proliferation. The peptide CysValTicMet is a potent FTase inhibitor, but its degradation by amino-peptidases and its only weak internalization into cells make it a bad candidate for a future cancer drug. We have prepared improved CysValTicMet analogues using several approaches: (i) amino terminal modifications or introduction of pseudopeptides or non-natural amino acids to increase proteolytic stability, (ii) introduction of hydrophobic aliphatic chains to increase cell internalization and metabolic stability and (iii) transformation into prodrugs. Additionally, we have carried out comparative conformational analysis studies by molecular dynamics of some of the here presented peptides and of our recently described peptidomimetic inhibitors of FTase.

A Ras-GTPase-activating protein SH3-domain-binding protein

We report the purification of a Ras-GTPase-activating protein (GAP)-binding protein, G3BP, a ubiquitously expressed cytosolic 68-kDa protein that coimmunoprecipitates with GAP. G3BP physically associates with the SH3 domain of GAP, which previously had been shown to be essential for Ras signaling. The G3BP cDNA revealed that G3BP is a novel 466-amino-acid protein that shares several features with heterogeneous nuclear RNA-binding proteins, including ribonucleoprotein (RNP) motifs RNP1 and RNP2, an RG-rich domain, and acidic sequences. Recombinant G3BP binds effectively to the GAP SH3 domain G3BP coimmunoprecipitates with GAP only when cells are in a proliferating state, suggesting a recruitment of a GAP-G3BP complex when Ras is in its activated conformation.

NMR structure of the N-terminal SH3 domain of GRB2 and its complex with a proline-rich peptide from Sos

GRB2 is a small adaptor protein of 217 amino acids comprising one SH2 domain surrounded by two SH3 domains. GRB2 couples receptor tyrosine kinase activation to Ras signalling by interacting, through its SH3 domains, to the carboxy-terminal proline-rich regions of the guanine nucleotide exchange factor Sos. Here we report the synthesis and solution structure of the amino-terminal SH3 domain of GRB2 and of its more stable Ser 32 mutant. 1H NMR analysis of the complex between the Ser-32-GRB2-N-SH3 domain and the proline-rich peptide VPPPVPPRRR, derived from h-Sos, shows that relative to the SH3 peptide complexes described for PI3K, Fyn and Abl, the proline-rich peptide in this complex binds in the opposite orientation.

Cloning of a Grb2 isoform with apoptotic properties

Growth factor receptor-bound protein 2 (Grb2) links tyrosine-phosphorylated proteins to a guanine nucleotide releasing factor of the son of sevenless (Sos) class by attaching to the former by its Src homology 2 (SH2) moiety and to the latter by its SH3 domains. An isoform of grb2 complementary DNA (cDNA) was cloned that has a deletion in the SH2 domain. The protein encoded by this cDNA, Grb3-3, did not bind to phosphorylated epidermal growth factor receptor (EGFR) but retained functional SH3 domains and inhibited EGF-induced transactivation of a Ras-responsive element. The messenger RNA encoding Grb3-3 was expressed in high amounts in the thymus of rats at an age when massive negative selection of thymocytes occurs. Microinjection of Grb3-3 into Swiss 3T3 fibroblasts induced apoptosis. These findings indicate that Grb3-3, by acting as a dominant negative protein over Grb2 and by suppressing proliferative signals, may trigger active programmed cell death.

Solution structure of GAP SH3 domain by 1H NMR and spatial arrangement of essential Ras signaling-involved sequence

Src homology 3 (SH3) domains are found in numerous cytoplasmic proteins involved in intracellular signal transduction. We used 2-D 1H NMR to determine the structure of the SH3 domain of the guanosine triphosphatase-activating protein (GAP), an essential component of the Ras signaling pathway. The structure of the GAP SH3 domain (275-350) was found to be a compact beta-barrel made of six antiparallel beta-strands arranged in two roughly perpendicular beta-sheets with the acidic residues located at the surface of the protein. The Trp317, Trp319, Thr321 and Leu323 residues belonging to the sequence (317-326), which was shown to be essential for Ras signaling, formed two nearby lipophilic bulges followed by a hydrophilic domain (Arg324-Asp326). These structural data could be used to characterize the still unidentified downstream components of GAP, which are involved in Ras signaling, and to rationally design inhibitors of this pathway.

Saccharomyces cerevisiae CDC25 (1028-1589) is a guanine nucleotide releasing factor for mammalian ras proteins and is oncogenic in NIH3T3 cells

The best characterized yeast guanine nucleotide releasing factor is CDC25, which acts on RAS and thereby stimulates cAMP production in Saccharomyces cerevisiae. In order to determine if CDC25 could be a specific GDP-GTP releasing factor for the mammalian proteins Ha-ras, Ki-ras, and N-ras, its functions were studied both in vitro and in NIH3T3 cells. The 561 amino acid composing the C-terminal domain of CDC25 (CDC25 C-domain) released guanine nucleotides (both GDP and GTP) from Ha-, Ki-, and N-ras but not from Rap1A, Rab5, and Rab11. CDC25 acted on oncogenically activated Ha-ras even if the last 23 amino acids (167-189) of the Ras proteins were not present. CDC25 transformed NIH3T3 cells; its transforming capacity was enhanced by overexpression of wild-type Ha-ras. CDC25 C-domain probably exerts its effects through the activation of cellular Ras proteins. These data suggest that the CDC25 C-domain can function as an upstream activator of Ras proteins in a heterologous system and therefore could be a useful tool to study the regulation of Ras activation by growth factor receptors.

Identification of the SH3 domain of GAP as an essential sequence for Ras-GAP-mediated signaling

Guanosine triphosphatase activating protein (GAP) is an essential component of Ras signaling pathways. GAP functions in different cell types as a deactivator and a transmitter of cellular Ras signals. A domain (amino acids 275 to 351) encompassing the Src homology region 3 (SH3) of GAP was found to be essential for GAP signaling. A monoclonal antibody was used to block germinal vesicle breakdown (GVBD) induced by the oncogenic protein Ha-ras Lys12 in Xenopus oocytes. The monoclonal antibody, which was found to recognize the peptide containing amino acids 275 to 351 within the amino-terminal domain of GAP, did not modify the stimulation of the Ha-Ras-GTPase by GAP. Injection of peptides corresponding to amino acids 275 to 351 and 317 to 326 blocked GVBD induced by insulin or by Ha-Ras Lys12 but not that induced by progesterone. These findings confirm that GAP is an effector for Ras in Xenopus oocytes and that the SH3 domain is essential for signal transduction.

The Saccharomyces cerevisiae gene product SDC25 C-domain functions as an oncoprotein in NIH3T3 cells

Ras proteins in mammalian cells cycle between a GTP-bound 'on' state and a GDP-bound 'off' state. Activation of Ras p21 results from the dissociation of tightly bound GDP and the exchange of bound GDP for GTP. A guanine nucleotide exchange factor is required for this activation. Activation promotes interaction with effector molecules and allows the signal to be transduced. In Saccharomyces cerevisiae, the function of guanine nucleotide exchange has been ascribed to the product of the CDC25 gene. The C-terminus domain of SDC25, a homologue of CDC25, can substitute for the CDC25 protein in yeast. We have demonstrated that the SDC25 C-terminus domain promotes GTP binding to Ras p21 in CHO cells. In the present study, we found that the stable expression of the SDC25 C-terminus domain induced transformation of NIH3T3 cells. Ras proteins in these tumorigenic cells were GTP bound. In addition, the coexpression of wild-type Ha-Ras protein with the SDC25 C-terminus was found to enhance the tumorigenic properties of the NIH3T3 cells. These results imply that, in subsets of human tumours, cellular Ras p21 might be found in its GTP-bound active form as a consequence of an oncogenic activation of a mammalian Ras guanine nucleotide exchange factor.

Evidence for at least four antigenic sites on type O foot-and-mouth disease virus involved in neutralization; identification by single and multiple site monoclonal antibody-resistant mutants

Neutralizing monoclonal antibodies raised against type O foot-and-mouth disease virus have been characterized on the basis of their reactivity with a panel of single site monoclonal antibody-resistant mutants which had defined three antigenic sites. Five antibodies neutralized all these mutants, but by selecting further single site mutants with one of these antibodies it was possible to define a fourth site involved in virus neutralization. Two monoclonal antibodies still neutralized these mutants and all multiple site resistant mutants. One multiple site resistant mutant was resistant to neutralization at each of four antigenic sites but was still efficiently neutralized by type O convalescent cattle sera. The relationship between sites recognized by different monoclonal antibodies generated in different laboratories is discussed.

Monoclonal antibodies against synovial collagenase: use for immunopurification and characterization of the latent and active enzyme

Monoclonal antibodies have been produced against porcine synovial collagenase which recognize both the active enzyme and its inactive precursor. These antibodies inhibited the collagenolytic activity of collagenase, but not its activity with a synthetic peptide substrate. The antibodies were also able to recognize human synovial, human skin fibroblast and human chondrocyte collagenase but not the enzyme from human granulocytes. One of the monoclonal antibodies was successfully used for the immunopurification of the porcine enzyme and these experiments led to the demonstration of an endogenous activator of procollagenase in the synovial cell culture medium.

Localization of a neutralization epitope of foot-and-mouth disease virus using neutralizing monoclonal antibodies

Neutralizing monoclonal antibodies raised against intact foot-and-mouth disease virus reacted with intact particles and with isolated VP1 from different strains from the same subtype. Prior treatment of the virus with either trypsin or with arginine-specific protease abolished recognition of both the virus and of VP1, suggesting the presence of a neutralization epitope in the central region of VP1 cleaved by these two enzymes. A synthetic peptide analogue of part of this region showed poor reactivity, however, with neutralizing antibody.

Phenylalanine ammonia-lyase in tobacco mosaic virus-infected hypersensitive tobacco. Density-labelling evidence of de novo synthesis

A strong increase in phenylalanine ammonia-lyase (EC 4.3.1.5) activity occurs in tobacco mosaic virus-infected tobacco leaves developing necrotic local lesions. Comparison of physicochemical properties of the partially purified enzymes extracted from healthy and infected leaves showed that the hypersensitive reaction leads to an increase in the pool size of the same active enzyme molecules as those present in non-infected material. The molecular mechanism of enzyme formation was investigated by radiolabelling with [3H]leucine and by density labelling with 2H2O. Abnormal patterns of incorporation of radioactivity into all soluble proteins were found in infected leaves carrying local lesions. In contrast, uptake of deuterium into the amino acid pool was the same in healthy and infected leaves. Unstimulated phenylalanine ammonia-lyase was shown to be a long-lived enzyme (half-life: 25-35 h). Results of comparative density labelling experiments unequivocally demonstrated that the increased enzyme pool size arose from an increased rate of synthesis mediated by the hypersensitive reaction.