Conjugation of a novel Apaf-1 inhibitor to peptide-based cell-membrane transporters: effective methods to improve inhibition of mitochondria-mediated apoptosis

We have identified a family of peptoids that inhibits in vitro the activity of the apoptosome, a macromolecular complex that activates mitochondrial-dependent apoptosis pathways. The analysis of peptide-based cell compatible delivery systems of the most active peptoid is presented. The active peptoid was then fused to cell penetrating peptides (CPP) as penetratin (PEN-peptoid) and HIV-1 TAT (TAT-peptoid). PEN-peptoid showed greater cell viability and as a consequence better efficiency as an apoptosis inhibitor than the TAT-peptoid. The intracellular trafficking of both inhibitors was studied by flow cytometry and confocal fluorescence microscopy. Finally, the influence of the cargo (peptoid) molecules on the conformational behavior of the CPP in buffers and in membrane mimetic environments was analyzed using circular dichroism (CD) spectroscopy.     

Estrogen Receptor (ER)α-regulated Lipocalin 2 Expression in Adipose Tissue Links Obesity with Breast Cancer Progression

Obesity is associated with increased breast cancer (BrCA) incidence. Considering that inactivation of estrogen receptor (ER)α promotes obesity and metabolic dysfunction in women and female mice, understanding the mechanisms and tissue-specific sites of ERα action to combat metabolic-related disease, including BrCA, is of clinical importance. To study the role of ERα in adipose tissue we generated fat-specific ERα knock-out (FERKO) mice. Herein we show that ERα deletion increased adipocyte size, fat pad weight, and tissue expression and circulating levels of the secreted glycoprotein, lipocalin 2 (Lcn2), an adipokine previously associated with BrCA development. Chromatin immunoprecipitation and luciferase reporter studies showed that ERα binds the Lcn2 promoter to repress its expression. Because adipocytes constitute an important cell type of the breast microenvironment, we examined the impact of adipocyte ERα deletion on cancer cell behavior. Conditioned medium from ERα-null adipocytes and medium containing pure Lcn2 increased proliferation and migration of a subset of BrCA cells in culture. The proliferative and promigratory effects of ERα-deficient adipocyte-conditioned medium on BrCA cells was reversed by Lcn2 deletion. BrCA cell responsiveness to exogenous Lcn2 was heightened in cell types where endogenous Lcn2 expression was minimal, but components of the Lcn2 signaling pathway were enriched, i.e. SLC22A17 and 3-hydroxybutyrate dehydrogenase (BDH2). In breast tumor biopsies from women diagnosed with BrCA we found that BDH2 expression was positively associated with adiposity and circulating Lcn2 levels. Collectively these data suggest that reduction of ERα expression in adipose tissue promotes adiposity and is linked with the progression and severity of BrCA via increased adipocyte-specific Lcn2 production and enhanced tumor cell Lcn2 sensitivity.     

MiR-187 Targets the Androgen-Regulated Gene ALDH1A3 in Prostate Cancer

miRNAs are predicted to control the activity of approximately 60% of all protein-coding genes participating in the regulation of several cellular processes and diseases, including cancer. Recently, we have demonstrated that miR-187 is significantly downregulated in prostate cancer (PCa) and here we propose a proteomic approach to identify its potential targets. For this purpose, PC-3 cells were transiently transfected with miR-187 precursor and miRNA mimic negative control. Proteins were analyzed by a two-dimensional difference gel electrophoresis (2D-DIGE) and defined as differentially regulated if the observed fold change was ±1.06. Then, MALDI-TOF MS analysis was performed after protein digestion and low abundance proteins were identified by LC–MS/MS. Peptides were identified by searching against the Expasy SWISS PROT database, and target validation was performed both in vitro by western blot and qRT-PCR and in clinical samples by qRT-PCR, immunohistochemistry and ELISA. DIGE analysis showed 9 differentially expressed spots (p<0.05) and 7 showed a down-regulated expression upon miR-187 re-introduction. Among these targets we identified aldehyde dehydrogenase 1A3 (ALDH1A3). ALDH1A3 expression was significantly downregulated in PC3, LNCaP and DU-145 cells after miR-187 re-introduction. Supporting these data, the expression of ALDH1A3 was found significantly (p<0.0001) up-regulated in PCa samples and inversely correlated (p<0.0001) with miR-187 expression, its expression being directly associated with Gleason score (p = 0.05). The expression of ALDH1A3 was measured in urine samples to evaluate the predictive capability of this biomarker for the presence of PCa and, at a signification level of 10%, PSA and also ALDH1A3 were significantly associated with a positive biopsy of PCa. In conclusion, our data illustrate for the first time the role of ALDH1A3 as a miR-187 target in PCa and provide insights in the utility of using this protein as a new biomarker for PCa.     

A quantum mechanics/molecular mechanics study of the catalytic mechanism of the thymidylate synthase

A theoretical study of the molecular mechanism of the thymidylate synthase-catalyzed reaction has been carried out using hybrid quantum mechanics/molecular mechanics methods. We have examined all of the stationary points (reactants, intermediates, transition structures, and products) on the multidimensional potential energy surfaces for the multistep enzymatic process. The characterization of these relevant structures facilitates the gaining of insight into the role of the different residues in the active site. Furthermore, analysis of the full energy profile has revealed that the step corresponding to the reduction of the exocyclic methylene intermediate by hydride transfer from the 6S position of 5,6,7,8-tetrahydrofolate (H4folate), forming dTMP and 7,8-dihydrofolate (H2folate), is the rate-limiting step, in accordance with the experimental data. In this step, the hydride transfer and the scission of an overall conserved active site cysteine residue (Cys146 in Escherichia coli) take place in a concerted but very asynchronous way. These findings have also been tested with primary and secondary deuterium, tritium, and sulfur kinetic isotope effects, and the calculations have been compared to experimental data. Finally, the incorporation of high-level quantum mechanical corrections to the semiempirical AM1 Hamiltonian into our hybrid scheme has allowed us to obtain reasonable values of the energy barrier for the rate-limiting step. The resulting picture of the complete multistep enzyme mechanism that is obtained reveals several new features of substantial mechanistic interest.     

Coaggregation, cointernalization, and codesensitization of adenosine A2A receptors and dopamine D2 receptors

Antagonistic and reciprocal interactions are known to exist between adenosine and dopamine receptors in the striatum. In the present study, double immunofluorescence experiments with confocal laser microscopy showed a high degree of colocalization of adenosine A(2A) receptors (A(2A)R) and dopamine D(2) receptors (D(2)R) in cell membranes of SH-SY5Y human neuroblastoma cells stably transfected with human D(2)R and in cultured striatal cells. A(2A)R/D(2)R heteromeric complexes were demonstrated in coimmunoprecipitation experiments in membrane preparations from D(2)R-transfected SH-SY5Y cells and from mouse fibroblast Ltk(-) cells stably transfected with human D(2)R (long form) and transiently cotransfected with the A(2A)R double-tagged with hemagglutinin. Long term exposure to A(2A)R and D(2)R agonists in D(2)R-cotransfected SH-SY5Y cells resulted in coaggregation, cointernalization and codesensitization of A(2A)R and D(2)R. These results give a molecular basis for adenosine-dopamine antagonism at the membrane level and have implications for treatment of Parkinson's disease and schizophrenia, in which D(2)R are involved.     

Genetically Based Location from Triploid Populations and Gene Ontology of a 3.3-Mb Genome Region Linked to Alternaria Brown Spot Resistance in Citrus Reveal Clusters of Resistance Genes

Genetic analysis of phenotypical traits and marker-trait association in polyploid species is generally considered as a challenge. In the present work, different approaches were combined taking advantage of the particular genetic structures of 2n gametes resulting from second division restitution (SDR) to map a genome region linked to Alternaria brown spot (ABS) resistance in triploid citrus progeny. ABS in citrus is a serious disease caused by the tangerine pathotype of the fungus Alternaria alternata. This pathogen produces ACT-toxin, which induces necrotic lesions on fruit and young leaves, defoliation and fruit drop in susceptible genotypes. It is a strong concern for triploid breeding programs aiming to produce seedless mandarin cultivars. The monolocus dominant inheritance of susceptibility, proposed on the basis of diploid population studies, was corroborated in triploid progeny. Bulk segregant analysis coupled with genome scan using a large set of genetically mapped SNP markers and targeted genetic mapping by half tetrad analysis, using SSR and SNP markers, allowed locating a 3.3 Mb genomic region linked to ABS resistance near the centromere of chromosome III. Clusters of resistance genes were identified by gene ontology analysis of this genomic region. Some of these genes are good candidates to control the dominant susceptibility to the ACT-toxin. SSR and SNP markers were developed for efficient early marker-assisted selection of ABS resistant hybrids.