Background: Gliadins, a family of wheat proteins, are central to the pathogenesis of celiac disease (CD). In addition to 'immunogenic' effects, gliadin directly affects cultured cells and intestine preparations, and produces damage in vivo, via a separate 'toxic' peptide, such as A-gliadin p31-43 (P31-43). Aims: Understanding the molecular mechanisms underlying direct non T-cell mediated effects of gliadin peptides, and assessing their potential role in promoting CD.Method: Gliadin effects were tested on a number of cell lines and on cultured mucosa samples by evaluating cytoskeleton rearrangements, endocytosis, proliferation and apoptosis. Standard biochemical methods were used to assess prolonged epidermal growth factor receptor (EGFR) activation. Results: Crude gliadin peptic-tryptic peptides (PTG], or P31-43 alone, fully reproduce the effects of epidermal growth factor (EGF] on actin cytosketon, cell cycle and cell proliferation of various cell lines. Inhibitor studies demonstrate the role of EGFR in the early response to gliadin exposure, pointing to activation of the EGFR pathway. Peptide P31-43 is not similar to any EGFR ligand, but can delay inactivation of the EGFR interfering with its endocytosis. Gliadin-induced delay of EGFR endocytosis in cultured intestinal biopsies, together with S-phase entry of epithelial intestinal cells, confirm a role for EGFR activation in CD. Conclusion: The ability of gliadin peptides to delay EGFR inactivation through interference with the endocytic pathway suggests a model where gliadin fragments amplify the effects of trace amounts of EGF, and possibly of other growth factors, by prolonging receptor activation. The results, using cultures of coeliac intestinal biopsies, highlight the role of the EGF pathway in establishing and maintaining the typical atrophic and proliferative alterations of the small intestine in CD.

Purification and amino acid sequence analysis of a proteolytic fragment of fibronectin (FN) from transformed human cells demonstrated that a high percentage of these FN molecules contains an extra amino acid sequence which is present only in a very low percentage of FN molecules from normal fibroblasts and is undetectable in plasma FN. This new amino acid sequence introduces into the FN molecule a site very sensitive to a number of proteolytic enzymes. By analyzing the cellular mRNA and genomic clones, we have demonstrated that this sequence derives from a differential splicing pattern of the FN mRNA precursors, which leads in transformed cells to a high‐level expression of an extra type III homology repeat (ED‐B) coded for by a previously unobserved exon. Here we also report the complete sequence of this new exon. These results demonstrate that in malignant cells the mechanisms regulating the splicing of FN mRNA precursors are altered.

We have analyzed the spatial organization of large scale chromatin domains in chinese hamster fibroblast, human lymphoid (IM-9), and marsupial kidney epithelial (PtK) cells by labeling DNA at defined stages of S phase via pulsed incorporation of halogenated deoxynucleosides. Most, if not all, chromosomes contribute multiple chromatin domains to both peripheral and internal nucleoplasmic compartments. The peripheral compartment contains predominantly late replicating G/Q bands, whereas early replicating R bands preferentially localize to the internal nucleoplasmic compartment. During mitosis, the labeled chromatin domains that were separated in interphase form a pattern of intercalated bands along the length of each metaphase chromosome. The transition from a banded (mitotic) to a compartmentalized (interphasic) organization of chromatin domains occurs during the late telophase/early G1 stage and is independent of transcriptional activation of the genome. Interestingly, generation of micronuclei with a few chromosomes showed that the spatial separation of early and late replicating chromatin compartments is recapitulated independently of chromosome number, even in micronuclei containing only a single chromosome. Our data strongly support the notion that the compartmentalization of large-scale (band size) chromatin domains seen in the intact nucleus is a magnified image of a similar compartmentalization occurring in individual chromosome territories.

BackgroundAndrogen receptor (AR) controls male morphogenesis, gametogenesis and prostate growth as well as development of prostate cancer. These findings support a role for AR in cell migration and invasiveness. However, the molecular mechanism involved in AR-mediated cell migration still remains elusive.Methodology/Principal FindingsMouse embryo NIH3T3 fibroblasts and highly metastatic human fibrosarcoma HT1080 cells harbor low levels of transcriptionally incompetent AR. We now report that, through extra nuclear action, AR triggers migration of both cell types upon stimulation with physiological concentrations of the androgen R1881. We analyzed the initial events leading to androgen-induced cell migration and observed that challenging NIH3T3 cells with 10 nM R1881 rapidly induces interaction of AR with filamin A (FlnA) at cytoskeleton. AR/FlnA complex recruits integrin beta 1, thus activating its dependent cascade. Silencing of AR, FlnA and integrin beta 1 shows that this ternary complex controls focal adhesion kinase (FAK), paxillin and Rac, thereby driving cell migration. FAK-null fibroblasts migrate poorly and Rac inhibition by EHT impairs motility of androgen-treated NIH3T3 cells. Interestingly, FAK and Rac activation by androgens are independent of each other. Findings in human fibrosarcoma HT1080 cells strengthen the role of Rac in androgen signaling. The Rac inhibitor significantly impairs androgen-induced migration in these cells. A mutant AR, deleted of the sequence interacting with FlnA, fails to mediate FAK activation and paxillin tyrosine phosphorylation in androgen-stimulated cells, further reinforcing the role of AR/FlnA interaction in androgen-mediated motility.Conclusions/SignificanceThe present report, for the first time, indicates that the extra nuclear AR/FlnA/integrin beta 1 complex is the key by which androgen activates signaling leading to cell migration. Assembly of this ternary complex may control organ development and prostate cancer metastasis.

BackgroundCeliac Disease (CD) is both a frequent disease (1∶100) and an interesting model of a disease induced by food. It consists in an immunogenic reaction to wheat gluten and glutenins that has been found to arise in a specific genetic background; however, this reaction is still only partially understood. Activation of innate immunity by gliadin peptides is an important component of the early events of the disease. In particular the so-called “toxic” A-gliadin peptide P31-43 induces several pleiotropic effects including Epidermal Growth Factor Receptor (EGFR)-dependent actin remodelling and proliferation in cultured cell lines and in enterocytes from CD patients. These effects are mediated by delayed EGFR degradation and prolonged EGFR activation in endocytic vesicles. In the present study we investigated the effects of gliadin peptides on the trafficking and maturation of endocytic vesicles.Methods/Principal FindingsBoth P31-43 and the control P57-68 peptide labelled with fluorochromes were found to enter CaCo-2 cells and interact with the endocytic compartment in pulse and chase, time-lapse, experiments. P31-43 was localised to vesicles carrying early endocytic markers at time points when P57-68-carrying vesicles mature into late endosomes. In time-lapse experiments the trafficking of P31-43-labelled vesicles was delayed, regardless of the cargo they were carrying. Furthermore in celiac enterocytes, from cultured duodenal biopsies, P31-43 trafficking is delayed in early endocytic vesicles. A sequence similarity search revealed that P31-43 is strikingly similar to Hrs, a key molecule regulating endocytic maturation. A-gliadin peptide P31-43 interfered with Hrs correct localisation to early endosomes as revealed by western blot and immunofluorescence microscopy.ConclusionsP31-43 and P57-68 enter cells by endocytosis. Only P31-43 localises at the endocytic membranes and delays vesicle trafficking by interfering with Hrs-mediated maturation to late endosomes in cells and intestinal biopsies. Consequently, in P31-43-treated cells, Receptor Tyrosin Kinase (RTK) activation is extended. This finding may explain the role played by gliadin peptides in inducing proliferation and other effects in enterocytes from CD biopsies.

Hammerhead ribozymes are efficient RNA enzymes characterized by a typical hammerhead secondary structure and a number of conserved bases. Little is known about the role of the ribose‐phosphate backbone, although it is obviously important since a DNA molecule with the same base sequence is not a catalyst. Here we describe the synthesis of artificial ribozymes where modified (2′‐O‐allyl‐ and 2′‐O‐methyl‐) ribonucleotides substitute for the corresponding ribonucleotides. A systematic analysis of partially substituted polymers identified a minimum set of six non‐contiguous positions where insertion of modified ribonucleotides strongly affects catalytic activity. Surprisingly, ribozymes completely substituted except for these six ribonucleotides are still very active. These molecules efficiently cleave in trans target RNAs in a sequence‐specific way, but, unlike RNA ribozymes, are very resistant to nuclease degradation and are very stable in serum. These properties make such synthetic polymers potentially useful for in vivo gene expression studies and therapeutic applications.

Background: Protein kinases are a well defined family of proteins, characterized by the presence of a common kinase catalytic domain and playing a significant role in many important cellular processes, such as proliferation, maintenance of cell shape, apoptosys. In many members of the family, additional non-kinase domains contribute further specialization, resulting in subcellular localization, protein binding and regulation of activity, among others. About 500 genes encode members of the kinase family in the human genome, and although many of them represent well known genes, a larger number of genes code for proteins of more recent identification, or for unknown proteins identified as kinase only after computational studies.

The essential sequences needed for Alu repeat transcription by RNA polymerase III were mapped. Experimental evidence is presented showing that the Alu repeat promoters are organised in a bipartite structure similar to the split tRNA promoters as suggested by DNA sequence homology. Furthermore, by combining fragments from efficiently and inefficiently transcribed natural Alu repeats in several recombinant clones, it was possible to investigate the regions responsible for their differences. It is clear that, apart from the short stretches of homology with the tRNA consensus sequence, there is very little constraint in the promoter sequences. However, our studies indicate that some influence on the efficiency of transcription may be exerted by regions outside the accepted promoter components.