IGF-I receptor-induced cell-cell adhesion of MCF-7 breast cancer cells requires the expression of junction protein ZO-1

Hyperactivation of the insulin-like growth factor I receptor (IGF-IR) contributes to primary breast cancer development, but the role of the IGF-IR in tumor metastasis is unclear. Here we studied the effects of the IGF-IR on intercellular connections mediated by the major epithelial adhesion protein, E-cadherin (E-cad). We found that IGF-IR overexpression markedly stimulated aggregation in E-cad-positive MCF-7 breast cancer cells, but not in E-cad-negative MDA-MB-231 cells. However, when the IGF-IR and E-cad were co-expressed in MDA-MB-231 cells, cell-cell adhesion was substantially increased. The IGF-IR-dependent cell-cell adhesion of MCF-7 cells was not related to altered expression of E-cad or alpha-, beta-, or gamma-catenins but coincided with the up-regulation of another element of the E-cad complex, zonula occludens-1 (ZO-1). ZO-1 expression (mRNA and protein) was induced by IGF-I and was blocked in MCF-7 cells with a tyrosine kinase-defective IGF-IR mutant. By co-immunoprecipitation, we found that ZO-1 associates with the E-cad complex and the IGF-IR. High levels of ZO-1 coincided with an increased IGF-IR/alpha-catenin/ZO-1-binding and improved ZO-1/actin association, whereas down-regulation of ZO-1 by the expression of an anti-ZO-1 RNA inhibited IGF-IR-dependent cell-cell adhesion. The results suggested that one of the mechanisms by which the activated IGF-IR regulates E-cad-mediated cell-cell adhesion is overexpression of ZO-1 and the resulting stronger connections between the E-cad complex and the actin cytoskeleton. We hypothesize that in E-cad-positive cells, the IGF-IR may produce antimetastatic effects.     

The human tumor suppressor arf interacts with spinophilin/neurabin II, a type 1 protein-phosphatase-binding protein

The INK4a gene, one of the most often disrupted loci in human cancer, encodes two unrelated proteins, p16(INK4a) and p14(ARF) (ARF) both capable of inducing cell cycle arrest. Although it has been clearly demonstrated that ARF inhibits cell cycle via p53 stabilization, very little is known about the involvement of ARF in other cell cycle regulatory pathways, as well as on the mechanisms responsible for activating ARF following oncoproliferative stimuli. In search of factors that might associate with ARF to control its activity or its specificity, we performed a yeast two-hybrid screen. We report here that the human homologue of spinophilin/neurabin II, a regulatory subunit of protein phosphatase 1 catalytic subunit specifically interacts with ARF, both in yeast and in mammalian cells. We also show that ectopic expression of spinophilin/neurabin II inhibits the formation of G418-resistant colonies when transfected into human and mouse cell lines, regardless of p53 and ARF status. Moreover, spinophilin/ARF coexpression in Saos-2 cells, where ARF ectopic expression is ineffective, somehow results in a synergic effect. These data demonstrate a role for spinophilin in cell growth and suggest that ARF and spinophilin could act in partially overlapping pathways.     

Interaction of Pig Kidney and Lentil Seedling Copper-Containing Amine Oxidases with Guanidinium Compounds

The effect of guanidinium compounds on the catalytic mechanism of pig kidney and lentil seedling amine oxidases has been investigated by polarographic techniques and spectroscopy. Guanidine does not inhibit the lentil enzyme and is a weak inhibitor for pig kidney amine oxidase (K(i) =1 mM), whereas aminoguanidine is an irreversible inhibitor of both enzymes, with a K(i) value of 10(-6) M. 1,4-Diguanidino butane (arcaine) is a competitive inhibitor for both pig and lentil amine oxidases. Amiloride is a competitive inhibitor for pig enzyme, but upon prolonged incubation with this drug the enzyme gradually loses its activity in an irreversible manner.     

Helicobacter pylori vacuolating toxin forms anion-selective channels in planar lipid bilayers: possible implications for the mechanism of cellular vacuolation

The Helicobacter pylori VacA toxin plays a major role in the gastric pathologies associated with this bacterium. When added to cultured cells, VacA induces vacuolation, an effect potentiated by preexposure of the toxin to low pH. Its mechanism of action is unknown. We report here that VacA forms anion-selective, voltage-dependent pores in artificial membranes. Channel formation was greatly potentiated by acidic conditions or by pretreatment of VacA at low pH. No requirement for particular lipid(s) was identified. Selectivity studies showed that anion selectivity was maintained over the pH range 4.8-12, with the following permeability sequence: Cl- approximately HCO3- > pyruvate > gluconate > K+ approximately Li+ approximately Ba2+ > NH4+. Membrane permeabilization was due to the incorporation of channels with a voltage-dependent conductance in the 10-30 pS range (2 M KCl), displaying a voltage-independent high open probability. Deletion of the NH2 terminus domain (p37) or chemical modification of VacA by diethylpyrocarbonate inhibited both channel activity and vacuolation of HeLa cells without affecting toxin internalization by the cells. Collectively, these observations strongly suggest that VacA channel formation is needed to induce cellular vacuolation, possibly by inducing an osmotic imbalance of intracellular acidic compartments.     

Telomere length in fibroblasts and blood cells from healthy centenarians

Several lines of evidence indicate that telomere shortening during in vitro aging of human somatic cells plays a causal role in cellular senescence. A critical telomere length seems to be associated with the replicative block characterizing senescent cells. In this paper we analyzed the mean length of the terminal restriction fragments (TRF) in fibroblast strains from 4 healthy centenarians, that is, in cells aged in vivo, and from 11 individuals of different ages. No correlation between mean TRF length and donor age was found. As expected, telomere shortening was detected during in vitro propagation of centenarian fibroblasts, suggesting that in fibroblasts aged in vivo telomeres can be far from reaching a critical length. Accordingly, chromosome analysis did not show the presence of telomeric associations in early passage centenarian fibroblasts. In blood cells from various individuals, the expected inverse correlation between mean TRF length and donor age was found. In particular, a substantial difference (about 2 kb) between telomere length in the two cell types was observed in the same centenarian. Expression analysis of three senescence-induced genes, i.e., fibronectin, apolipoprotein J, and p21, revealed for only the fibronectin expression levels a clear positive correlation with donor age. Our results suggest that (1) telomere shortening could play a different role in the aging of different cell types and (2) the characteristics of fibroblasts aged in vitro might not be representative of what occurs in vivo.     

Megalin (gp330) is an endocytic receptor for thyroglobulin on cultured fisher rat thyroid cells

We recently reported that megalin (gp330), an endocytic receptor found on the apical surface of thyroid cells, binds thyroglobulin (Tg) with high affinity in solid phase assays. Megalin-bound Tg was releasable by heparin. Here we show that Fisher rat thyroid (FRTL-5) cells, a differentiated rat thyroid cell line, can bind and endocytose Tg via megalin. We first demonstrated that FRTL-5 cells express megalin in a thyroid-stimulating hormone-dependent manner. Evidence of Tg binding to megalin on FRTL-5 cells and on an immortalized rat renal proximal tubule cell line (IRPT cells), was obtained by incubating the cells with 125I-Tg, followed by chemical cross-linking and immunoprecipitation of 125I-Tg with antibodies against megalin. To investigate cell binding further, we developed an assay in which cells were incubated with unlabeled Tg at 4 degrees C, followed by incubation with heparin, which released almost all of the cell-bound Tg into the medium. In solid phase experiments designed to illuminate the mechanism of heparin release, we demonstrated that Tg is a heparin-binding protein, as are several megalin ligands. The amount of Tg released by heparin from FRTL-5 and IRPT cells, measured by enzyme-linked immunosorbent assay (ELISA), was markedly reduced by two megalin competitors, receptor-associated protein (RAP) and 1H2 (monoclonal antibody against megalin), indicating that much of the Tg released by heparin had been bound to megalin ( approximately 60-80%). The amount inhibited by RAP was considered to represent specific binding to megalin, which was saturable and of high affinity (Kd approximately 11.2 nM). Tg endocytosis by FRTL-5 and IRPT cells was demonstrated in experiments in which cells were incubated with unlabeled Tg at 37 degrees C, followed by heparin to remove cell-bound Tg. The amount of Tg internalized (measured by ELISA in the cell lysates) was reduced by RAP and 1H2, indicating that Tg endocytosis is partially mediated by megalin.     

Nociceptin receptor activation inhibits tachykinergic non adrenergic non cholinergic contraction of guinea pig isolated bronchus

We studied the action of nociceptin (NC) on the atropine-resistant contractions of the guinea pig isolated bronchus evoked by the electrical field stimulation (EFS), an effect that is mediated by the activation of excitatory non adrenergic-non cholinergic (eNANC) nerves and the subsequent release of tachykinins. The functional site by which NC acts in this preparation was investigated using few different NC receptor agonists and the newly discovered NC receptor antagonist, [Phe1psi(CH2-NH)Gly2]NC(1-13)NH2 ([F/G]NC(1-13)NH2). NC inhibited in a concentration dependent manner (pEC50 7.14; Em - 87 +/- 3% of control values) EFS induced contractions. NC effect was mimicked by the NC analogues, NCNH2 and NC(1-13)NH2, but not by NC(1-9)NH2. NC (1 microM) did not affect the contractile effects of exogenously applied neurokinin A (1 microM). [F/G]NC(1-13)NH2 (10 microM) completely prevented the inhibition induced by NC (1 microM), whereas naloxone (1 microM) was found inactive. Both naloxone and ([F/G]NC(1-13)NH2 were per se inactive on basal resting tone as well as on the electrically induced contractions. The present findings show that NC inhibits the atropine-resistant EFS-induced contraction in the guinea pig bronchus by inhibiting eNANC nerves, and suggest the presence of NC receptors, distinct from opioid receptors, on the nerves of the guinea pig bronchus.     

Mouse K-Cl cotransporter KCC1: cloning, mapping, pathological expression, and functional regulation

Although K-Cl cotransporter (KCC1) mRNA is expressed in manytissues, K-Cl cotransport activity has been measured in few cell types,and detection of endogenous KCC1 polypeptide has not yet been reported.We have cloned the mouse erythroid KCC1 (mKCC1) cDNA and its flankinggenomic regions and mapped the mKCC1 gene to chromosome 8. Threeanti-peptide antibodies raised against recombinant mKCC1 function asimmunoblot and immunoprecipitation reagents. The tissue distributionsof mKCC1 mRNA and protein are widespread, and mKCC1 RNA isconstitutively expressed during erythroid differentiation of ES cells.KCC1 polypeptide or related antigen is present in erythrocytes ofmultiple species in which K-Cl cotransport activity has beendocumented. Erythroid KCC1 polypeptide abundance is elevated inproportion to reticulocyte counts in density-fractionated cells, inbleeding-induced reticulocytosis, in mouse models of sickle celldisease and thalassemia, and in the corresponding human disorders.mKCC1-mediated uptake of ⁸⁶Rb intoXenopus oocytes requires extracellularCl, is blocked by thediureticR(+)-[2-n-butyl-6,7-dichloro-2-cyclopentyl-2,3-dihydro-1-oxo-1H-indenyl-5-yl-)oxy]acetic acid, and exhibits an erythroid pattern of acute regulation, with activation by hypotonic swelling,N-ethylmaleimide, and staurosporine and inhibition by calyculin and okadaic acid. These reagents and findings will expedite studies of KCC1 structure-function relationships and of the pathobiology of KCC1-mediated K-Cl cotransport.

     

Effect of different growth hormone dosages on the growth velocity in children born small for gestational age

To assess whether short-term growth hormone (GH) treatment can improve the linear growth in children who were born small for gestational age (SGA), we started a randomized multicenter trial in 26 age- and sex-matched prepubertal children born SGA. During the 1st year of GH therapy, all children received GH 0.23 mg/kg/week, then during the 2nd year, 13 children received the same dose (group A), and in the other 13 children, the dose of GH was doubled, i.e., 0.46 mg/kg/week (group B). During the 1st year of therapy, the growth velocity significantly (p<0.0001) increased in all patients. During the 2nd year, group A showed a significant decrease of the growth velocity (p<0.015), whereas group B maintained the growth rate. The height in group A children significantly increased during the 1st and the 2nd year of GH therapy (p<0.000002 and p<0.000001, respectively), reaching the normal range in 8 out of 13 children at the end of 2 years of GH therapy. The height in group B children significantly increased during the 1st and the 2nd year of GH therapy (p<0.000001 and p<0.000001, respectively), reaching the normal range in all 11 children who completed the GH therapy. The height gain was similar in groups A and B treated with the same GH dosage during the 1st year of therapy. A greater increase in height gain was found in children of group B treated with the higher GH dosage during the 2nd year of therapy as compared with group A (p<0.02). Significant increases in insulin-like growth factor I (p<0.0001), acid-labile subunit (p<0.0002), and bone/chronological age ratio (p<0.0001) were found after the 1st year of GH therapy, but no significant changes were observed during the 2nd year, independently of the GH dose. In conclusion, the height velocity of children born SGA significantly increases during the 1st year of GH therapy, diminishes, but can decrease during the 2nd year, if the GH dosage is not raised.     

DNA detection by integrable electronics

This paper presents a new electronic methodology to detect DNA hybridization for rapid identification of diseases, as well as food and environmental monitoring on a genetic base. The proposed solution exploits a new (electrical) capacitive measurement circuit, not requiring any prior labeling of the DNA (as it is often the case with the commonly employed optical detection). The sensitivity, the reliability, and the reproducibility of this device have been evaluated by experiments performed with a (non-integrated) prototype implementation, easily integrable in IC and/or micro-fabricated lab-on-a-chip.