Huntingtin proteolysis releases non-polyQ fragments that cause toxicity through dynamin 1 dysregulation

Cleavage of mutant huntingtin (HTT) is an essential process in Huntington's disease (HD), an inherited neurodegenerative disorder. Cleavage generates N-ter fragments that contain the polyQ stretch and whose nuclear toxicity is well established. However, the functional defects induced by cleavage of full-length HTT remain elusive. Moreover, the contribution of non-polyQ C-terminal fragments is unknown. Using time- and site-specific control of full-length HTT proteolysis, we show that specific cleavages are required to disrupt intramolecular interactions within HTT and to cause toxicity in cells and flies. Surprisingly, in addition to the canonical pathogenic N-ter fragments, the C-ter fragments generated, that do not contain the polyQ stretch, induced toxicity via dilation of the endoplasmic reticulum (ER) and increased ER stress. C-ter HTT bound to dynamin 1 and subsequently impaired its activity at ER membranes. Our findings support a role for HTT on dynamin 1 function and ER homoeostasis. Proteolysis-induced alteration of this function may be relevant to disease. Synopsis The development of a time and site-specifically controlled cleavage of the mutant huntingtin protein reveals a pathogenic mechanism induced by the non-polyQ-containing fragments that are generated upon proteolysis during disease progression. Huntingtin proteolysis generates N-ter fragments that contain the toxic polyQ stretch but also the corresponding C-ter fragments. N-ter to C-ter intramolecular interactions present in full-length huntingtin are abrogated by sequential cleavages. Whereas the N-ter polyQ fragments translocate into the nucleus, the non-polyQ C-ter huntingtin fragments remain in the cytoplasm and cause ER dilation, stress and cell death. C-ter huntingtin fragments bind and inactivate dynamin 1 at the ER thus causing ER dilation and toxicity. Site-specifically controlled cleavage of the mutant huntingtin protein reveals a pathogenic mechanism induced by non-polyQ-containing fragments that are generated upon proteolysis during disease progression.</p

Analysis of the esophageal carcinogenesis in an in vivo model : identification of new therapeutic targets

Le pronostic de l’adénocarcinome œsophagien (ADC) est très sombre, avec un taux de survie à 5 ans inférieur à 10 %, du à sa détection tardive. L’incidence de ce cancer est en constante augmentation depuis une trentaine d’année dans les pays occidentaux. L’ADC se développe sur un œsophage de Barrett, metaplasia induite par une exposition chronique de l’ œsophage au reflux duodéno-gastro-œsophagien. Notre équipe a précédemment montré que certains acides biliaires presents dans ce reflux régulent l’expression des deux mucines membranaires MUC1 et MUC4, ainsi que la PI3K et NF&#61547;B dans une lignée cellulaire d’adénocarcinome œsophagien humain. But du travail : Déterminer si le reflux duodéno-gastro-œsophagien induit une carcinogenèse œsophagienne dans un modèle in vivo, ainsi qu’identifier de nouvelles proteins associées à cette carcinogenèse. Matériel et méthodes : Un modèle de reflux chronique induit par chirurgie à été réalisé. L’expression des ARN ainsi que des protéines a été étudiée grâce aux techniques de RT-PCR, qRT-PCR, puces à ARN et immunohistochimie. Les propriétés biologiques de cellules issues d’un adénocarcinome œsophagien humain (OE33) ont été étudiées in vitro. Résultats : Tous les rats subissant un reflux montrent une inflammation ainsi qu’une néo-expression de gènes connus pour participer à la progression tumorale, plus particulièrement dans la différenciation, la prolifération, l’adhésion et la formation de métastases. Parmi ces gènes activés on retrouve les deux voies de signalisation PI3K et KF&#61547;B. De manière intéressante on observe une néoexpression des deux mucines membranaires Muc1 et Muc4 ainsi qu’une surexpression de deux protéines associées à la progression tumorale, S100a4 et Mcm6. Ces différents gènes participent à la régulation des propriétés biologiques des cellules d’adénocarcinome œsophagien. Conclusion : L’ensemble de ces résultats montre qu’une exposition chronique au reflux duodéno-gastro-œsophagien induit la progression vers un adénocarcinome œsophagien dans un modèle in vivo chez le rat. Nous avons mis en évidence des voies de signalisation ainsi que des proteins associées à la carcinogenèse œsophagienne, ces dernières pouvant être considérées comme de potentiels marqueurs ou cibles thérapeutiques dirigées contre l’adénocarcinome œsophagien. Mots clés : Adénocarcinome œsophagien, Œsophage de Barrett, reflux, biomarqueurs, mucines.Œsophageal adenocarcinoma (ADK) has a very poor prognosis with a survival rate at 5 years at 10%, due to its late detection. Its incidence has been increasing for the last 30 years. ADK develops on Barrett œsophagus, a metaplastic lesion induced by chronic exposure of œsophagus to the duodeno-gastro-œsophageal reflux. Moreover we showed previously that bile acids activate MUC1 and MUC4 mucins, PI3K and NF&#954;B signalling pathways in human adenocarcinomatous cells. Aim: To determine whether the reflux induces œsophageal carcinogenesis in an in vivo model, and to identify new tumor-associated proteins. Material and methods: A rat model of chronic reflux induced by surgery was established. Expression of RNA and proteins was studied using RT-PCR, qRT-PCR, micro-arrays and immunohistochemistry. Effects on cell biological properties were carried out in vitro in OE33 œsophageal adenocarcinomatous cells. Results: All rats with reflux showed inflammation and neoexpression of genes involved in tumor progression with alterations of markers involved in differentiation, proliferation, adhesion and metastasis in which key pathways such as PI3K and NF&#954;B were found activated. More importantly, Muc1 and Muc4 mucins were neoexpressed, and two new tumor-associate proteins, S100a4 and Mcm6, were overexpressed in tumors and showed in vitro effects on œsophageal cancer cell biological properties. Conclusion: Altogether, these data indicate that progression toward adenocarcinoma was effective following induction of a chronic reflux in rat œsophagus and that signalling pathways and new tumor-associated proteins were identified that may be new biomarkers and new therapeutic targets in œsophageal adenocarcinoma. Key words: Œsophageal adenocarcinoma, Barrett œsophagus, reflux, biomarkers, mucins

Physical abilities of elderly nursing home residents: The SENIOR cohort

peer reviewe

Relationship between isometric strength of 6 muscle groups of the lower limbs and motor skills among nursing home residents

peer reviewe

Operatively induced chronic reflux in rats: A suitable model for studying esophageal carcinogenesis?

International audienceBackground. The mechanisms of esophageal reflux leading to esophageal adenocarcinoma (EA) remain poorly understood. This study appraises critically an operatively induced chronic reflux rat model. Methods. We randomized 108 Sprague-Dawley rats into 2 experimental groups; one was performing esophagoduodenal (ED) anastomosis with or without gastrectomy to induce duodeno-esophageal reflux (DER group; n = 63), and the other involved duodeno-gastro-esophageal reflux (DGER group; n = 45). Control groups included (i) Roux-en-Y esophagojejunal anastomosis, (ii) laparotomy alone, (iii) subtotal gastrectomy to induce duodenogastric reflux (DGR group), and (iv) the same procedure as in the DGER group plus proton pump inhibition (PPI group). The esophagus underwent histologic and molecular analyses. Results. The prevalence of Barrett's esophagus (BE), dysplasia, and EA in the experimental groups was 41%, 7%, and 11%, respectively. Histologic and molecular analyses in groups DER, DGER, and DGR suggested that BE occurred through de novo intestinal metaplasia and proximal migration of duodenal cells. No distant metastases were identified. The molecular characteristics of both BE and EA were similar to humans. BE was more common, and dysplasia and EA less frequent in the DER group when compared with the DGER group (44% vs 24% [ P = .038] and 7% vs 25% [ P = .012], respectively). Compared with the DGER group, carcinogenic sequence occurred less frequently in the PPI-treated group (P = .019). Conclusion. Despite pathophysiologic differences with humans, the rat model of esophagoduodenostomy reproduces accurately histologic and molecular lesions in the carcinogenetic sequence of BE and allowed us to identify novel, tumor-associated proteins that may be potential biomarkers and new therapeutic targets in EA

New 5-Aryl-1H-imidazoles display in vitro antitumor activity against apoptosis-resistant cancer models, including melanomas, through mitochondrial targeting.

We designed and synthesized 48 aryl-1H-imidazole derivatives and investigated their in vitro growth inhibitory activity in cancer cell lines known to present various levels of resistance to proapoptotic stimuli. The IC50 in vitro growth inhibitory concentration of these compounds ranged from >100 μM to single digit μM. Among the most active compounds, 2i displayed similar in vitro growth inhibition in cancer cells independent of the cells' levels of resistance to proapoptotic stimuli and was found to be cytostatic in melanoma cell lines. Compound 2i was then tested by the National Cancer Institute Human Tumor Cell Line Anti-Cancer Drug Screen, and the NCI COMPARE algorithm did not reveal any correlation between its growth inhibition profiles with the NCI database compound profiles. The use of transcriptomically characterized melanoma models then enabled us to highlight mitochondrial targeting by 2i. This hypothesis was further confirmed by reactive oxygen production measurement and oxygen consumption analysis.Journal ArticleResearch Support, Non-U.S. Gov'tSCOPUS: ar.jinfo:eu-repo/semantics/publishe