Biomedical subjects

Angeliki Fotinopoulou

Publications and source records attributed to Angeliki Fotinopoulou.

3 recordsLinked to original sources

PubMed2005

BRI2 interacts with amyloid precursor protein (APP) and regulates amyloid beta (Abeta) production.

Transmembrane proteins BRI2 and amyloid precursor protein (APP) co-localize with amyloid beta (Abeta) lesions in sporadic Alzheimer disease and mutations in both precursor proteins are linked to early-onset familial cases of cerebral amyloidosis associated with dementia and/or cerebral hemorrhage. A specific interaction between BRI2 and APP was unveiled by immunoprecipitation experiments using transfected and non-transfected cells. The use of deletion mutants further revealed that stretches 648-719 of APP751 and 46-106 of BRI2, both inclusive of the full transmembrane domains, are sufficient for the interaction. Removal of most of the APP and BRI2 extracellular domains without affecting the interaction implies that both proteins interact when are expressed on the same cell membrane (cis) rather than on adjacent cells (trans). The presence of BRI2 had a modulatory effect on APP processing, specifically increasing the levels of cellular APP as well as beta-secretase-generated COOH-terminal fragments while decreasing the levels of alpha-secretase-generated COOH-terminal fragments as well as the secretion of total APP and Abeta peptides. Determining the precise molecular pathways affected by the specific binding between APP and BRI2 could result in the identification of common therapeutic targets for these sporadic and familial neurodegenerative disorders.

Adaptor Proteins, Signal Transducing↗

PubMed2004

Presenilin 1 and cadherins: stabilization of cell-cell adhesion and proteolysis-dependent regulation of transcription.

Presenilin-1 (PS1) has gained intensive attention in relation to Alzheimer's disease, since it has been shown that PS1 mutations are linked to familial Alzheimer's disease (FAD), and that PS1 is a member of the high molecular weight complex of gamma-secretase, which generates the carboxyl end of beta-amyloid peptide (gamma-cleavage). A parallel line of evidence suggests that upon formation of cell-cell contacts, presenilin colocalizes with cadherins at the cell surface and stabilizes the cadherin-based adhesion complex. Under conditions stimulating cell-cell dissociation, cadherins are processed by a PS1/gamma-secretase activity, promoting disassembly of adherens junctions, and resulting in the increase of cytosolic beta-catenin, which is an important regulator of the Wnt/Wingless signaling pathway. PS1 also controls the cleavage of a number of transmembrane proteins at the interface of their transmembrane and cytosolic domains (epsilon-cleavage), producing intracellular fragments with a putative transcriptional role. Remarkably, cleavage of N-cadherin by PS1 produces an intracellular fragment that downregulates CREB-mediated transcription, indicating a role of PS1 in gene expression. PS1 mutations associated with FAD abolish production of the N-cadherin intracellular fragment and thus fail to suppress CREB-dependent transcription. These findings suggest an alternative explanation for FAD that is separate from the widely accepted 'amyloid hypothesis': dysfunction in transcription regulatory mechanisms.

Alzheimer Disease↗

PubMed2003

Screening for glycosylation changes on recombinant human IgG using lectin methods.

Two lectin-binding methods were investigated as possible ways of monitoring the glycosylation of human monoclonal antibodies during their development and production. Carbohydrate composition was assessed in various preparations that were produced in different host cell types, cell sublines or batches of the same cells. The lectin binding was measured with ELISA and surface plasmon resonance (SPR). For comparative purposes, the monosaccharide content of many of the preparations was also measured by high-pressure anion exchange chromatography (HPAEC)/pulsed amperometric detection (PAD). Both lectin methods detected modifications in glycosylation when antibodies were produced in different ways; SPR was more sensitive than ELISA for some lectins and vice versa. Generally, the lectin results agreed with those obtained by the monosaccharide analysis; however, the former were much better for assessing N -acetylneuraminic acid changes. The latter were impossible to assess by HPAEC/PAD because of their low levels. The lectin-based methods also had the advantages that they were quicker to perform and required less expertise and could quickly identify structures that monosaccharide analysis might miss. It is suggested that, in the development of therapeutic proteins, monosaccharide analysis and/or oligosaccharide profiling is initially performed but later routine batches of the glycoprotein are screened with a lectin method. Of the two lectin methods used, SPR is much quicker when performing a screen, whereas ELISA is particularly useful for comparing a particular carbohydrate feature on different samples of the same glycoprotein.

Enzyme-Linked Immunosorbent Assay↗