Biomedical subjects

Jesús Espada

Publications and source records attributed to Jesús Espada.

4 recordsLinked to original sources

PubMed2005

Direct metabolic regulation of beta-catenin activity by the p85alpha regulatory subunit of phosphoinositide 3-OH kinase.

Class IA phosphoinositide 3-OH kinases (PI3K) are lipid kinases composed of catalytic and regulatory subunits. These lipid kinases can regulate the metabolic stability and signaling activity of beta-catenin, a central component of the E-cadherin/catenin cell-cell adhesion complex, and of the Wnt signaling pathway. This regulation occurs at the level of glycogen synthase kinase 3 (GSK3), a serine/threonine kinase that marks beta-catenin to enter a destruction pathway. In addition, the regulatory subunit p85alpha directly binds beta-catenin, but the role of this interaction in the context of the lipid kinase regulation of beta-catenin signaling is unknown. Here we report that expression of exogenous p85alpha in mouse keratinocytes increases the metabolic stability and has a strong synergistic effect on the transcriptional activity of beta-catenin. Both effects are associated to the formation of beta-catenin/p85alpha and inhibition of beta-catenin/APC complexes and are independent of GSK3 and PI3K activities. These findings suggest that p85alpha can act as a direct metabolic regulator of beta-catenin activity.

Adenomatous Polyposis Coli Protein↗

PubMed2005

Non-aqueous permanent mounting for immunofluorescence microscopy.

It is generally assumed that an aqueous mounting medium is necessary for the preservation of immunofluorescent-labelled microscopical preparations and polyvinyl alcohol-based solutions (e.g. Mowiol) being the most frequently used mounting media; however, both the quality and intensity of the fluorescence signal in most immunolabelled preparations after aqueous mounting slowly diminish with time, and finally, samples become unsuitable for examination. In the present work, we describe a very simple and rapid non-aqueous mounting procedure for cultured cells and tissue sections, which preserves the fluorescent signal in an excellent way after immunodetection or use of other specific labelling methods. It is based on the current histological protocol in which, after fluorescence labelling, preparations are dehydrated in ethanol, cleared in xylene and mounted in DePeX. Using this non-aqueous mounting medium, the fluorescent signal remains high and stable, allowing a suitable and permanent preservation of labelled and counterstained microscopical preparations.

Animals↗

PubMed2005

Loss of E-cadherin mediated cell-cell adhesion as an early trigger of apoptosis induced by photodynamic treatment.

Photodynamic treatment with different photosensitizers (PSs) can result in the specific induction of apoptosis in many cell types. It is commonly accepted that this apoptotic response depends on the mitochondrial accumulation of the PS. Accumulation in other cellular organelles, such as lysosomes or the Golgi complex, and subsequent photodamage resulting in an apoptotic process has been also described. However, the role played by cell adhesion in apoptosis induced in epithelial cells after photodynamic treatment is not well characterized. Here, we have used a murine keratinocyte line, showing a strong dependence on E-cadherin for cell-cell adhesion and survival, to analyze the relevance of this adhesion complex in the context of zinc(II)-phthalocyanine (ZnPc) photodynamic treatment. We report that under apoptotic conditions, ZnPc phototreatment induces a rapid disorganization of the E-cadherin mediated cell-cell adhesion, which largely preceded both the detachment of cells from the substrate, via beta-1 integrins and the induction of apoptotic mitochondrial markers. Therefore, the alteration in E-cadherin, alpha- and beta-catenins adhesion proteins preceded the release of cytochrome c (cyt c) from mitochondria to the cytosol and the activation of caspase 3. In addition, blocking E-cadherin function with a specific antibody (Decma-1) induced apoptosis in this cell system. These results strongly suggest that the E-cadherin adhesion complex could be the primary target of ZnPc phototreatment, and that loss of E-cadherin mediated cell adhesion after early photodamage triggers an apoptotic response.

Animals↗

PubMed2004

A mouse skin multistage carcinogenesis model reflects the aberrant DNA methylation patterns of human tumors.

Whereas accepted models of tumorigenesis exist for genetic lesions, the timing of epigenetic alterations in cancer is not clearly understood. We have analyzed the profile of aberrations in DNA methylation occurring in cells lines and primary tumors of one of the best-characterized mouse carcinogenesis systems, the multistage skin cancer progression model. Initial analysis using high-performance capillary electrophoresis and immunolocalization revealed a loss of genomic 5-methylcytosine associated with the degree of tumor aggressiveness. Paradoxically, this occurs in the context of a growing number of hypermethylated CpG islands of tumor suppressor genes at the most malignant stages of carcinogenesis. We have observed this last phenomenon using two approaches, a candidate gene approach, studying genes with well-known methylation-associated silencing in human tumors, and a mouse cDNA microarray expression analysis after treatment with DNA demethylating drugs. The transition from epithelial to spindle cell morphology is particularly associated with major epigenetic alterations, such as E-cadherin methylation, demethylation of the Snail promoter, and a decrease of the global DNA methylation. Analysis of data obtained from the cDNA microarray strategy led to the identification of new genes that undergo methylation-associated silencing and have growth-inhibitory effects, such as the insulin-like growth factor binding protein-3. Most importantly, all of the above genes were also hypermethylated in human cancer cell lines and primary tumors, underlining the value of the mouse skin carcinogenesis model for the study of aberrant DNA methylation events in cancer cells.

5-Methylcytosine↗