Profiling Ubiquitin and Ubiquitin-like Dependent Post-translational Modifications and Identification of Significant Alterations

Ubiquitin (ub) and ubiquitin-like (ubl) dependent post-translational modifications of proteins play fundamental biological regulatory roles within the cell by controlling protein stability, activity, interactions, and intracellular localization. They enable the cell to respond to signals and to adapt to changes in its environment. Alterations within these mechanisms can lead to severe pathological situations such as neurodegenerative diseases and cancers. The aim of the technique described here is to establish ub/ubls dependent PTMs profiles, rapidly and accurately, from cultured cell lines. The comparison of different profiles obtained from different conditions allows the identification of specific alterations, such as those induced by a treatment for example. Lentiviral mediated cell transduction is performed to create stable cell lines expressing a two-tags (6His and Flag) version of the modifier (ubiquitin or a ubl such as SUMO1 or Nedd8). These tags permit the purification of ubiquitin and therefore of ubiquitinated proteins from the cells. This is done through a two-step purification process: The first one is performed in denaturing conditions using the 6His tag, and the second one in native conditions using the Flag tag. This leads to a highly specific and pure isolation of modified proteins which are subsequently identified and semi-quantified by liquid chromatography followed by tandem mass spectrometry (LC-MS/MS) technology. Easy informatics analysis of MS data using Excel software enables the establishment of PTM profiles by eliminating background signals. These profiles are compared between each condition in order to identify specific alterations which will then be studied more specifically, starting with their validation by standard biochemistry techniques.

Ribonuclease MCPiP1 contributes to the loss of micro-RNA-200 family members in pancreatic cancer cells

The microRNA-200 (miR-200) family is frequently down-regulated in tumors, including pancreatic adenocarcinomas (PDACs). In this study we have examined the mechanisms involved in the loss of miR-200s in tumoral pancreatic cells. Whereas miR-200 gene promoters appear methylated in mature miR-200 deficient cell lines, miR-200 precursors are detected in nuclear but not cytoplasmic compartment of these cells, indicating that promoter hypermethylation is not sufficient to explain the deficit of mature miR-200s. The ribonuclease Monocyte Chemotactic Protein-induced Protein-1 (MCPiP1) may counteract Dicer1 in miRNA maturation process. MCPiP1/Dicer1 mRNA and protein ratios appear higher in miR-200 deficient compared to miR-200 proficient cells, suggesting that MCPiP1 may compete with Dicer1 in mature miR-200 deficient cells. Inhibition of MCPiP1 allows the detection of miR-200 precursors in cytoplasm of miR-200 deficient cells, confirming its involvement in the loss of miR-200s. Also, reversion of MCPiP1/Dicer1 ratio by over-expression of Dicer1 in miR-200 deficient cells leads to the recovery of mature miR-200s. Finally, whereas human malignant pancreatic tissues (PDACs) express lower miR-200 levels than non malignant tissues (non-MPDs), MCPiP1/Dicer1 ratio appears higher in PDACs, when compared to non-MPDs, supporting the hypothesis that MCPiP1/Dicer1 ratio is determinant in regulating miR-200 maturation process in a subset of tumoral pancreatic cells.

Cadherin-1 and cadherin-3 cooperation determines the aggressiveness of pancreatic ductal adenocarcinoma

Background:

Pancreatic ductal adenocarcinoma (PDAC) is characterised by an extensive tissue invasion and an early formation of metastasis. Alterations in the expression of cadherins have been reported in PDAC. Yet, how these changes contribute to tumour progression is poorly understood. Here, we investigated the relationship between cadherins expression and PDAC development.

Methods:

Cadherins expression was assessed by immunostaining in both human and murine tissue specimens. We have generated pancreatic cancer cell lines expressing both cadherin-1 and cadherin-3 or only one of these cadherins. Functional implications of such genetic alterations were analysed both in vitro and in vivo.

Results:

Cadherin-3 is detected early at the plasma membrane during progression of pancreatic intraepithelial neoplasia 1 (PanIN-1) to PDAC. Despite tumoural cells turn on cadherin-3, a significant amount of cadherin-1 remains expressed at the cell surface during tumourigenesis. We found that cadherin-3 regulates tumour growth, while cadherin-1 drives type I collagen organisation in the tumour. In vitro assays showed that cadherins differentially participate to PDAC aggressiveness. Cadherin-3 regulates cell migration, whereas cadherin-1 takes part in the invadopodia activity.

Conclusions:

Our results show differential, but complementary, roles for cadherins during PDAC carcinogenesis and illustrate how their expression conditions the PDAC aggressiveness.

Saccharomyces boulardii CNCM I-745 Restores intestinal Barrier Integrity by Regulation of E-cadherin Recycling

BACKGROUND AND AIMS

Alteration in intestinal permeability is the main factor underlying the pathogenesis of many diseases affecting the gut, such as inflammatory bowel disease [IBD]. Characterization of molecules targeting the restoration of intestinal barrier integrity is therefore vital for the development of alternative therapies. The yeast Saccharomyces boulardii CNCM I-745 [Sb], used to prevent and treat antibiotic-associated infectious and functional diarrhea, may have a beneficial effect in the treatment of IBD.

METHODS

We analyzed the impact of Sb supernatant on tissue integrity and components of adherens junctions using cultured explants of colon from both IBD and healthy patients. To evaluate the pathways by which Sb regulates the expression of E-cadherin at the cell surface, we developed in vitro assays using human colonic cell lines, including cell aggregation, a calcium switch assay, real-time measurement of transepithelial electrical resistance [TEER] and pulse-chase experiments.

RESULTS

We showed that Sb supernatant treatment of colonic explants protects the epithelial morphology and maintains E-cadherin expression at the cell surface. In vitro experiments revealed that Sb supernatant enhances E-cadherin delivery to the cell surface by re-routing endocytosed E-cadherin back to the plasma membrane. This process, involving Rab11A-dependent recycling endosome, leads to restoration of enterocyte adherens junctions, in addition to the overall restoration and strengthening of intestinal barrier function.

CONCLUSION

These findings open new possibilities of discovering novel options for prevention and therapy of diseases that affect intestinal permeability.