Rôle du récepteur de la gastrine dans le pancréas endocrine

Présents dans le pancréas humain fœtal, la gastrine et son récepteur, le récepteur CCK2, pourraient contribuer activement à la différenciation des cellules de l'îlot de Langerhans en induisant l'expression du gène du glucagon dans les cellules alpha. A partir d'un nouveau modèle de cellules alpha pancréatiques exprimant le récepteur CCK2, nous montrons que la gastrine stimule l'expression du gène du glucagon en activant le facteur de transcription Egr-1 via la cascade de signalisation MEK1/ERK1/2. De plus, nous démontrons que Egr-1 est indispensable à l'expression basale du gène du glucagon. Par ailleurs, la capacité de 4 lignées pancréatiques canalaires humaines à exprimer certains gènes du lignage cellulaire endocrine a été étudiée. En réponse à des agents pro-différenciateurs, la lignée BxPC3 semble être un modèle adéquat pour l'étude de la différenciation endocrine dans le pancréas adulte.Expressed in human fetal pancreas, gastrin and its receptor (CCK2 receptor) may actively contribute to the differentiation of endocrine cells by inducing glucagon gene expression in alpha cells. Using a new alpha pancreatic cell model expressing the CCK2 receptor, we show that gastrin stimulates glucagon gene expression by activating the MEK1/ERK1/2 signaling cascade and the transcription factor Egr-1. Moreover, expression of genes involved in endocrine lineage was investigated from 4 human pancreatic duct cell lines. In response to agents which can induce endocrine differentiation, BxPC3 cell line seems to be a suitable model in order to study mechanisms controlling endocrine differentiation in adult pancreas.TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

E3 Ubiquitin Ligase TRIP12: Regulation, Structure, and Physiopathological Functions

The Thyroid hormone Receptor Interacting Protein 12 (TRIP12) protein belongs to the 28-member Homologous to the E6-AP C-Terminus (HECT) E3 ubiquitin ligase family. First described as an interactor of the thyroid hormone receptor, TRIP12’s biological importance was revealed by the embryonic lethality of a murine model bearing an inactivating mutation in the TRIP12 gene. Further studies showed the participation of TRIP12 in the regulation of major biological processes such as cell cycle progression, DNA damage repair, chromatin remodeling, and cell differentiation by an ubiquitination-mediated degradation of key protein substrates. Moreover, alterations of TRIP12 expression have been reported in cancers that can serve as predictive markers of therapeutic response. The TRIP12 gene is also referenced as a causative gene associated to intellectual disorders such as Clark–Baraitser syndrome and is clearly implicated in Autism Spectrum Disorder. The aim of the review is to provide an exhaustive and integrated overview of the different aspects of TRIP12 ranging from its regulation, molecular functions and physio-pathological implications

Oncogène

La mutation ponctuelle de l’oncogène Kras confère un gain de prolifération non contrôlée pour la cellule cancéreuse qui acquiert ainsi un pouvoir oncogénique amplifié. Cette mutation est retrouvée dans 75 à 95 % des cancers du pancréas, mais aussi dans les lésions précancéreuses de type PanIN (pancreatic intraepithelial neoplasia) ou TIPMP (tumeur intracanalaire papillaire mucineuse du pancréas). Ces lésions, ainsi que le microenvironnement tumoral, ont été reproduits dans des modèles transgéniques établis chez la souris à partir de la mutation de Kras (souris Pdx1 [pancreatic and duodenal homeobox 1]-Cre ; KrasG12D) associée ou non à l’inactivation de gènes suppresseurs de tumeurs (TP53, DPC4, INK4A). La recherche de la mutation de Kras en clinique humaine est facile et fiable à partir des milieux biologiques, en particulier sur le matériel de cytoponction de masses pancréatiques prélevé sous écho-endoscopie. Cette recherche devrait être utile dans un avenir proche pour l’aide au diagnostic positif de cancer, en cas de d’examen cytopathologique douteux ou non contributif, mais aussi pour le diagnostic différentiel avec la pancréatite chronique dans sa forme pseudotumorale

The epigenetic mechanisms underlying the long-term effects of maternal obesity and/or maternal separation in mice

It is well-known that early life exposures to biological and/or social stressors may have a long-term impact on adult health. However, the biological mechanisms underlying the developmental origins of health and disease (DOHaD) are not fully understood. Epigenetic mechanisms are good candidates to explain how early events are memorized and induce a phenotype later in life. Various studies have thus shown in mammals that poor nutritional status of parents and low maternal care have an impact on the methylation of genes involved in physiology and in the hypothalamic-pituitary adrenal (HPA) axis in the offspring1,2,3. But the consequences of multiple adversities on epigenetic processes remain to be explored. In this context, our aim was to explore the epigenetic basis (DNA methylation) of maternal obesity combined with maternal separation stress in mice. We study the impact of a combination of maternal obesity and maternal separation on offspring’s physiology, behaviour (emotionality and motivation) and epigenome in C3H mice. Our results indicate that maternal obesity and maternal stress exacerbated anxiety-like behaviour in adult offspring. We hypothesised that epigenetic marks could be one of the molecular bases responsible for the embodiment of early exposure to stress. Currently, we use large-scale transcriptomic (RNA-seq) and DNA methylation (MeDIP-seq) analyses on adult offspring’s liver and nucleus accumbens, which are key organs for energy metabolism and food motivation. Preliminary results show that early life exposure to maternal obesity and stress affect metabolic pathways in liver at transcriptomic and epigenetic levels. Interestingly, we also reported a marked sexual dimorphism in the epigenetic effects of maternal obesity and stress. Our future work will focus on the heritability of these epigenetic marks across generations and their influence on observed phenotype

Les dérégulations de transcriptome et du méthylome hépatique associées au stress nutritionnel et psychosocial maternel sont amplifiées par un régime post-sevrage hypergras chez la souris

National audienc

The epigenetic mechanisms underlying the long-term effects of maternal obesity and/or maternal separation in mice

It is well-known that early life exposures to biological and/or social stressors may have a long-term impact on adult health. However, the biological mechanisms underlying the developmental origins of health and disease (DOHaD) are not fully understood. Epigenetic mechanisms are good candidates to explain how early events are memorized and induce a phenotype later in life. Various studies have thus shown in mammals that poor nutritional status of parents and low maternal care have an impact on the methylation of genes involved in physiology and in the hypothalamic-pituitary adrenal (HPA) axis in the offspring1,2,3. But the consequences of multiple adversities on epigenetic processes remain to be explored. In this context, our aim was to explore the epigenetic basis (DNA methylation) of maternal obesity combined with maternal separation stress in mice. We study the impact of a combination of maternal obesity and maternal separation on offspring’s physiology, behaviour (emotionality and motivation) and epigenome in C3H mice. Our results indicate that maternal obesity and maternal stress exacerbated anxiety-like behaviour in adult offspring. We hypothesised that epigenetic marks could be one of the molecular bases responsible for the embodiment of early exposure to stress. Currently, we use large-scale transcriptomic (RNA-seq) and DNA methylation (MeDIP-seq) analyses on adult offspring’s liver and nucleus accumbens, which are key organs for energy metabolism and food motivation. Preliminary results show that early life exposure to maternal obesity and stress affect metabolic pathways in liver at transcriptomic and epigenetic levels. Interestingly, we also reported a marked sexual dimorphism in the epigenetic effects of maternal obesity and stress. Our future work will focus on the heritability of these epigenetic marks across generations and their influence on observed phenotype

Differential tissular expression of the CCK(A) and CCK(B) gastrin receptor genes during postnatal development in the calf.

International audienceLocal and temporal expression of CCK(A) and CCK(B)/gastrin receptor genes was studied in the calf with a quantitative Reverse Transcription-Polymerase Chain Reaction (RT-PCR) method. Cerebral cortex, antrum, fundus, gall bladder, pancreas and liver were analyzed in calves at 0, 2, 7, 21, 28 and 150 days of age. Cerebral cortex and pancreas expressed both receptor genes with a ratio between CCK(A) and CCK(B)/gastrin receptor transcripts varying according to the age. Gall bladder and fundus showed an exclusive expression of CCK(A) and CCK(B)/gastrin receptor mRNAs, respectively, with the highest levels of transcripts in newborn and 28-day-old calves. The rank order for CCK(A) receptor mRNA expression was gall bladder > pancreas > cerebral cortex > antrum and that for CCK(B)/gastrin receptor mRNA expression was cerebral cortex / pancreas / fundus > antrum. No CCK(A) and CCK(B)/gastrin receptor mRNA was detected in liver, regardless of the age of calves. The present data represent a basis for a better understanding of the ontogeny of physiological functions linked to the CCK(A) and CCK(B)/gastrin receptors

Id3 modulates cellular localization of bHLH Ptf1-p48 protein.

International audiencePtf1-p48 is a pancreas-specific bHLH transcriptional protein, which, in the normal adult pancreas, shows a restricted expression in acinar cells where it is predominantly localized in the nucleus and activates the transcription of exocrine-specific genes. Ptf1-p48 partners with two proteins to form the PTF1 active complex: a bHLH E-protein and suppressor of hairless RBP-J. Cytoplasmic mislocalization of Ptf1-p48 has been reported in pancreatic pathologies, suggesting its contribution in the early steps of pancreatic carcinogenesis. The aim of the our work was to elucidate the mechanisms regulating Ptf1-p48 subcellular localization. We hypothesized a role of Id proteins acting in a dominant-negative fashion by heterodimerizing with bHLH proteins. We reproduced Ptf1-p48 cytoplasmic mislocalization in acinar AR4-2J cells and demonstrated that a proliferative signal elicited by gastrin leads to increases in Id3 protein expression and levels of Id3/E47 and Id3/Ptf1-p48 interactions, and a decrease in the level of E47/Ptf1-p48 interaction. By contrast, Id3 silencing reversed the cytoplasmic mislocalization of Ptf1-p48 induced by gastrin. As E47 is responsible for the nuclear import of the PTF1 complex, disruption of this complex via Id3 interactions with both E47 and Ptf1-p48 appears to induce cytoplasmic mislocalization of Ptf1-p48. We then found that Ptf1-p48 is either absent or mislocalized in the cytoplasm and Id3 is overexpressed in human and murine pancreatic preneoplastic lesions. Our data provide novel insight into the regulation of Ptf1-p48 function and provide evidence that Ptf1-p48 cytoplasmic mislocalization and Id3 overexpression are early events in pancreatic cancer progression

Partial agonism, neutral antagonism, and inverse agonism at the human wild-type and constitutively active cholecystokinin-2 receptors.

Cholecystokinin receptor-2 (CCK2R) is a G protein receptor that regulates a number of physiological functions. Activation of CCK2R and/or expression of a constitutively active CCK2R variant may contribute to human diseases, including digestive cancers. Search for antagonists of the CCK2R has been an important challenge during the last few years, leading to discovery of a set of chemically distinct compounds. However, several early-discovered antagonists turned out to be partial agonists. In this context, we carried out pharmacological characterization of six CCK2R antagonists using COS-7 cells expressing the human CCK2R or a CCK2R mutant having a robust constitutive activity on inositol phosphates production, and we investigated the molecular mechanisms which, at a CCK2R binding site, account for these features. Results indicated that three compounds, 3R(+)-N-(2,3-dihydro-1-methyl-2-oxo-5-phenyl-1H-1,4-benzodiazepin-3-yl)-N'-(3-methylphenyl)urea (L365,260), 4-{[2-[[3-(lH-indol-3-yl)-2-methyl-1-oxo-2-[[[1.7.7-trimethyl-bicyclo[2.2.1]hept-2-yl)-oxy]carbonyl]amino]propyl]amino]-1-phenylethyl]amino-4-oxo-[lS-la.2[S*(S*)]4a]}-butanoate N-methyl-D-glucamine (PD135,158), and (R)-1-naphthalenepropanoic acid, b-[2-[[2-(8-azaspiro-[4.5]dec-8-ylcarbonyl)-4,6-dimethylphenyl]amino]-2-oxoethyl] (CR2945), were partial agonists; one molecule, 1-[(R)-2,3-dihydro-1-(2,3-dihydro-1-(2-methylphenacyl)-2-oxo-5-phenyl-1H-1,4-benzodiazepin-3-yl]-3-(3-methylphenyl)urea (YM022), was a neutral antagonist; and two compounds, N-(+)-[1-(adamant-1-ylmethyl)-2,4-dioxo-5-phenyl2,3,4,5-tetrahydro-1H-1,5-benzodiazepin-3-yl]-N'-phenylurea (GV150,013X) and ([(N-[methoxy-3 phenyl] N-[N-methyl N-phenyl carbamoylmethyl], carbomoyl-methyl)-3 ureido]-3-phenyl)2-propionic acid (RPR101,048), were inverse agonists. Furthermore, target- and pharmacophore-based docking of ligands followed by molecular dynamic simulation experiments resulted in consistent motion of aromatic residues belonging to a network presumably important for activation, thus providing the first structural explanations for the different pharmacological profiles of tested compounds. This study confirms that several referenced so-called antagonists are in fact partial agonists, and because of this undesired activity, we suggest that newly generated molecules should be preferred to efficiently block CCK2R-related physiological effects. Furthermore, data on the structural basis for the different pharmacological features of CCK2R ligands will serve to further clarify CCK2R mechanism of activation.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe