Alteration of cadherin-mediated cell-cell adhesion is frequently associated to tyrosine phosphorylation of p120- and β-catenins. We have examined the role of this modification in these proteins in the control of β-catenin/E-cadherin binding usingin vitro assays with recombinant proteins. Recombinant pp60^c-src efficiently phosphorylated both catenins in vitro, with stoichiometries of 1.5 and 2.0 mol of phosphate/mol of protein for β-catenin and p120-catenin, respectively. pp60^c-src phosphorylation had opposing effects on the affinities of β-catenin and p120 for the cytosolic domain of E-cadherin; it decreased (in the case of β-catenin) or increased (for p120) catenin/E-cadherin binding. However, a role for p120-catenin in the modulation of β-catenin/E-cadherin binding was not observed, since addition of phosphorylated p120-catenin did not modify the affinity of phosphorylated (or unphosphorylated) β-catenin for E-cadherin. The phosphorylated Tyr residues were identified as Tyr-86 and Tyr-654. Experiments using point mutants in these two residues indicated that, although Tyr-86 was a better substrate for pp60^c-src, only modification of Tyr-654 was relevant for the interaction with E-cadherin. Transient transfections of different mutants demonstrated that Tyr-654 is phosphorylated in conditions in which adherens junctions are disrupted and evidenced that binding of β-catenin to E-cadherin in vivo is controlled by phosphorylation of β-catenin Tyr-654.

Background— Spontaneous Ca ²⁺ release from the sarcoplasmic reticulum (SR) can generate afterdepolarizations, and these have the potential to initiate arrhythmias. Therefore, an association may exist between spontaneous SR Ca ²⁺ release and initiation of atrial fibrillation (AF), but this has not yet been reported. Methods and Results— Spontaneous Ca ²⁺ release from the SR, manifested as Ca ²⁺ sparks and Ca ²⁺ waves, was recorded with confocal microscopy in atrial myocytes isolated from patients with and those without AF. In addition, the spontaneous inward current associated with Ca ²⁺ waves was measured with the use of the perforated patch-clamp technique. The Ca ²⁺ spark frequency was higher in 8 patients with AF than in 16 patients without (6.0±1.2 versus 2.8±0.8 sparks/mm per second, P <0.05). Similarly, the spontaneous Ca ²⁺ wave frequency was greater in patients with AF (2.8±0.5 versus 1.1±0.3 waves/mm per second, P <0.01). The spontaneous inward current frequency was also higher in 10 patients with AF than in 13 patients without this arrhythmia (0.101±0.028 versus 0.031±0.007 per second, P <0.05, at a clamped potential of −80 mV). In contrast, both the Ca ²⁺ released from the SR and the Na ⁺ -Ca ²⁺ exchange rate induced by a rapid caffeine application were comparable in patients with and without AF. Conclusions— The observed increase in spontaneous Ca ²⁺ release in patients with AF probably is due to an upregulation of the SR Ca ²⁺ release channel activity, which may contribute to the development of AF.

Undesired immune responses have drastically hampered outcomes after allogeneic organ transplantation and cell therapy, and also lead to inflammatory diseases and autoimmunity. Umbilical cord mesenchymal stem cells (UCMSCs) have powerful regenerative and immunomodulatory potential, and their secreted extracellular vesicles (EVs) are envisaged as a promising natural source of nanoparticles to increase outcomes in organ transplantation and control inflammatory diseases. However, poor EV preparations containing highly-abundant soluble proteins may mask genuine vesicular-associated functions and provide misleading data. Here, we used Size-Exclusion Chromatography (SEC) to successfully isolate EVs from UCMSCs-conditioned medium. These vesicles were defined as positive for CD9, CD63, CD73 and CD90, and their size and morphology characterized by NTA and cryo-EM. Their immunomodulatory potential was determined in polyclonal T cell proliferation assays, analysis of cytokine profiles and in the skewing of monocyte polarization. In sharp contrast to the non-EV containing fractions, to the complete conditioned medium and to ultracentrifuged pellet, SEC-purified EVs from UCMSCs inhibited T cell proliferation, resembling the effect of parental UCMSCs. Moreover, while SEC-EVs did not induce cytokine response, the non-EV fractions, conditioned medium and ultracentrifuged pellet promoted the secretion of pro-inflammatory cytokines by polyclonally stimulated T cells and supported Th17 polarization. In contrast, EVs did not induce monocyte polarization, but the non-EV fraction induced CD163 and CD206 expression and TNF-α production in monocytes. These findings increase the growing evidence confirming that EVs are an active component of MSC's paracrine immunosuppressive function and affirm their potential for therapeutics in nanomedicine. In addition, our results highlight the importance of well-purified and defined preparations of MSC-derived EVs to achieve the immunosuppressive effect.

Sacubitril/Valsartan, proved superiority over other conventional heart failure management treatments, but its mechanisms of action remains obscure. In this study, we sought to explore the mechanistic details for Sacubitril/Valsartan in heart failure and post-myocardial infarction remodeling, using an in silico, systems biology approach. Myocardial transcriptome obtained in response to myocardial infarction in swine was analyzed to address post-infarction ventricular remodeling. Swine transcriptome hits were mapped to their human equivalents using Reciprocal Best (blast) Hits, Gene Name Correspondence, and InParanoid database. Heart failure remodeling was studied using public data available in gene expression omnibus (accession GSE57345, subseries GSE57338), processed using the GEO2R tool. Using the Therapeutic Performance Mapping System technology, dedicated mathematical models trained to fit a set of molecular criteria, defining both pathologies and including all the information available on Sacubitril/Valsartan, were generated. All relationships incorporated into the biological network were drawn from public resources (including KEGG, REACTOME, INTACT, BIOGRID, and MINT). An artificial neural network analysis revealed that Sacubitril/Valsartan acts synergistically against cardiomyocyte cell death and left ventricular extracellular matrix remodeling via eight principal synergistic nodes. When studying each pathway independently, Valsartan was found to improve cardiac remodeling by inhibiting members of the guanine nucleotide-binding protein family, while Sacubitril attenuated cardiomyocyte cell death, hypertrophy, and impaired myocyte contractility by inhibiting PTEN. The complex molecular mechanisms of action of Sacubitril/Valsartan upon post-myocardial infarction and heart failure cardiac remodeling were delineated using a systems biology approach. Further, this dataset provides pathophysiological rationale for the use of Sacubitril/Valsartan to prevent post-infarct remodeling.