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Migliaccio N.,University of Naples Federico II | Ruggiero I.,University of Naples Federico II | Martucci N.M.,University of Naples Federico II | Sanges C.,University of Naples Federico II | And 6 more authors.
Biochimie | Year: 2015

The eukaryotic translation elongation factor 1A (eEF1A) is a moonlighting protein that besides to its canonical role in protein synthesis is also involved in many other cellular processes such as cell survival and apoptosis. In a previous work, we identified eEF1A Raf-mediated phosphorylation sites and defined their role in the regulation of eEF1A half-life and apoptosis of human cancer cells. We proposed that the phosphorylation of eEF1A by C-Raf required the presence of both eEF1A isoforms thus suggesting the formation of a potential eEF1A heterodimer owning regulatory properties. This study aimed at investigating the cellular localization and interaction between two eEF1A isoforms. To this end, we developed chimera proteins by adding at the N-terminal end of both eEF1A1 and eEF1A2 cyan fluorescence protein (mCerulean) and yellow fluorescence protein (mVenus), respectively. The fluorescent eEF1A1 and eEF1A2 chimeras were both addressed to COS-7 cells and found co-localized in the cytoplasm at the level of cellular membranes. We highlighted FRET between the labeled N-termini of eEF1A isoforms. The intra-molecular FRET of this chimera was about 17%. Our results provide novel information on the intracellular distribution and interaction of eEF1A isoforms. © 2015 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). Source

Di Stadio C.S.,University of Naples Federico II | Altieri F.,University of Naples Federico II | Miselli G.,University of Naples Federico II | Elce A.,University of Naples Federico II | And 8 more authors.
Biochimie | Year: 2016

AMP18 is a stomach-specific secreted protein expressed in normal gastric mucosa but absent in gastric cancer. AMP18 plays a major role in maintaining gastric mucosa integrity and is characterized by the presence of a BRICHOS domain consisting of about 100 amino acids, present also in several unrelated proteins, and probably endowed with a chaperon-like activity. In this work, we exploited a functional proteomic strategy to identify potential AMP18 interactors with the aim to add knowledge on its functional role within gastric cell lines and tissues. To this purpose, recombinant biotinylated AMP18 was purified and incubated with protein extract from human normal gastric mucosa by applying an affinity chromatography strategy. The interacting proteins were identified by peptide mass fingerprinting using MALDI-TOF mass spectrometry. The pool of interacting proteins contained SLC26A3, a protein expressed in the apical membrane of intestinal epithelial cells, supposed to play a critical role in Cl- absorption and fluid homeostasis. The interaction was also confirmed by Western blot with anti-SLC26A3 on transfected AGS cell extract following AMP18 pull-down. Furthermore, the interaction between AMP18 and SLC26A3 was also validated by confocal microscopy that showed a co-localization of both proteins at plasma membrane level. More importantly, for the first time, we showed that SLC26A3 is down-regulated in gastric cancer and that the overexpression of AMP18 in AMP-transfected gastric cancer cells up-regulated the expression of SLC26A3 both at transcriptional and translational level, the latter probably through the activation of the MAP kinases pathway. These findings strongly suggest that AMP18 might play an anti-inflammatory role in maintaining mucosal integrity also by regulating SLC26A3 level. © 2015 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). Source

Villano V.,University of Naples Federico II | Di Stadio C.S.,University of Naples Federico II | Federico A.,University of Naples Federico II | Altieri F.,University of Naples Federico II | And 5 more authors.
Journal of Negative Results in BioMedicine | Year: 2016

Background: We aimed to ascertain if Gastrokine 1 mRNA in the sera of patients with gastric cancer might be an informative biomarker for the disease. Results: Analysis of GKN1 mRNA in serum samples from healthy individuals (n = 23) and from patients with diagnosis of gastric cancer (n = 16), performed by using absolute quantification based on standard curve method, did not show any significative statistical difference between the two unpaired group of individuals. Conclusions: Our preliminary results did not confirm GKN1 as a potential biomarker for gastric cancer. © 2016 The Author(s). Source

Rippa E.,University of Naples Federico II | Altieri F.,University of Naples Federico II | Di Stadio C.S.,University of Naples Federico II | Miselli G.,University of Naples Federico II | And 8 more authors.
Pathology Research and Practice | Year: 2015

Gastrokine 1 (GKN1) is a stomach-specific protein important in the replenishment of the surface lumen epithelial cell layer and in maintaining mucosal integrity. A role in cell proliferation and differentiation has also been hypothesized. Despite these findings, the function(s) as well as the cellular localization of GKN1 in the cellular machinery are currently not clarified. The investigation of subcellular localization of GKN1 in gastric cancer cells can provide insights into its potential cellular roles. Subcellular fractions of gastric cancer cells (AGS) transfected with full-length GKN1 (flGKN1) or incubated with recombinant GKN1 (rGKN1) lacking the first 20 amino acids at N-terminal were analyzed by Western blot and confocal microscopy and compared with those from normal gastric tissue. Wild type GKN1 (wtGKN1) and flGKN1 were revealed in the cytoplasm and in the membrane fractions of gastric cells, whereas rGKN1 was revealed in the cytoplasmic fractions, but a high amount was detected in the membrane pellet of the AGS lysate. The cellular distribution of GKN1 was also confirmed by confocal microscopy. The purified protein was also used to highlight its possible association with actin through confocal microscopy, pelleting assay, and size-exclusion chromatography. GKN1 co-localizes with actin in normal gastric tissue, but no direct interaction was observed between the two proteins in vitro. Most likely, GKN1 indirectly participates in actin stabilization since its overexpression in gastric cancer cells strongly increases the expression of tight and adherens junction proteins. © 2015 Elsevier GmbH. Source

Sanges C.,University of Naples Federico II | Sanges C.,University of Wurzburg | Scheuermann C.,University of Wurzburg | Zahedi R.P.,Leibniz Institute for Analytical Sciences | And 11 more authors.
Cell Death and Disease | Year: 2012

We identified eukaryotic translation elongation factor 1A (eEF1A) Raf-mediated phosphorylation sites and defined their role in the regulation of eEF1A half-life and of apoptosis of human cancer cells. Mass spectrometry identified in vitro S21 and T88 as phosphorylation sites mediated by B-Raf but not C-Raf on eEF1A1 whereas S21 was phosphorylated on eEF1A2 by both B- and C-Raf. Interestingly, S21 belongs to the first eEF1A GTP/GDP-binding consensus sequence. Phosphorylation of S21 was strongly enhanced when both eEF1A isoforms were preincubated prior the assay with C-Raf, suggesting that the eEF1A isoforms can heterodimerize thus increasing the accessibility of S21 to the phosphate. Overexpression of eEF1A1 in COS 7 cells confirmed the phosphorylation of T88 also in vivo. Compared with wt, in COS 7 cells overexpressed phosphodeficient (A) and phospho-mimicking (D) mutants of eEF1A1 (S21A/D and T88A/D) and of eEF1A2 (S21A/D), resulted less stable and more rapidly proteasome degraded. Transfection of S21 A/D eEF1A mutants in H1355 cells increased apoptosis in comparison with the wt isoforms. It indicates that the blockage of S21 interferes with or even supports C-Raf induced apoptosis rather than cell survival. Raf-mediated regulation of this site could be a crucial mechanism involved in the functional switching of eEF1A between its role in protein biosynthesis and its participation in other cellular processes. © 2012 Macmillan Publishers Limited All rights reserved. Source

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