Onset of transcription of the aminopeptidase N (leukemia antigen CD 13) gene at the crypt/villus transition zone during rabbit enterocyte differentiation

AbstractThe sequence of a cDNA clone (2.82 kbp) of rabbit intestinal aminopeptidase N (CD 13) is reported. Using the corresponding anti-sense RNA probe, the distribution of aminopeptidase N mRNA along the crypt/villus axis of the rabbit small intestine was studied by in situ hybridization. The aminopeptidase N gene is expressed along the whole length of the villus with a maximum at its base. Expression was not detected in the crypt cells. The distribution of aminopeptidase N mRNA correlates with the presence of active enzyme as monitored by histochemical staining. The results are compatible with onset of transcription of the aminopeptidase N gene at the crypt/villus transition zone during the enterocyte differentiation

Homophilic Interactions between Cadherin Fragments at the Single Molecule Level: An AFM Study

We report measurements of the adhesion forces between single E-cadherin fragments anchored on solid surfaces. These fragments consist of the two outermost extracellular domains of the protein. The specificity of the measured rupture forces was demonstrated by Ca2+ exchange experiments. Two series of experiments were performed using two linkers of different rigidity and length. We find that the pull-off force is distributed with a maximum value independent of the linker and logarithmically dependent on the velocity of separation of the two surfaces. Our dynamical results are compatible with previous flow chamber experiments performed with the same fragments and can be compared from a different perspective with previously reported AFM experiments on the full-length extracellular domain of the VE-cadherin. Interestingly, using a rigid linker, we have been able for the first time to evidence the deformation of the cadherin molecule under mechanical stress, a piece of information not accessible with more classical grafting strategies

Polarisation de l'entérocyte. Biogénèse des domaines de la membrane plasmique

International audienc

Polarisation de l'entérocyte. Biogénèse des domaines de la membrane plasmique

International audienc

Expression of the Cytoplasmic Domain of E-cadherin Induces Precocious Mammary Epithelial Alveolar Formation and Affects Cell Polarity and Cell–Matrix Integrity

AbstractCadherins are cell adhesion molecules involved in cell–cell adhesion, signalling, and cellular proliferation and differentiation. E-cadherin is required for the formation of epithelium in vivo. We investigated the contribution of the cytoplasmic domain of E-cadherin to adhesion, signalling, and differentiation during murine mammary gland development, by in vivo expression of a gene encoding a truncated form of E-cadherin lacking the extracellular domain. The expression of this gene in mammary epithelial cells during pregnancy induced precocious lobular epithelial morphogenesis associated with morphological differentiation and the early synthesis of various molecules (advanced milk fat globule appearance and milk protein production). After delivery, when a fully differentiated and secretory epithelium is required for lactation, the cytoplasmic domain of E-cadherin had a dominant-negative effect on cell–cell adhesion and affected the structure and function of the epithelium. This also led to the partial loss of epithelial polarisation and changes in the basement membrane, both important in malignancy. Thus, the cytoplasmic domain of E-cadherin induces epithelial morphogenesis, but also alters the cohesiveness of the fully differentiated epithelium

Abstract 991: Cadherin-cadherin engagement promotes cell survival via Rac/Cdc42 and Stat3

Abstract Stat3 (signal transducer and activator of transcription-3) is activated by a number of receptor and non-receptor tyrosine kinases, while a constitutively active form of Stat3 alone is sufficient to induce neoplastic transformation. We recently demonstrated a dramatic increase in the activity of Stat3 in breast carcinoma as well as normal epithelial cells and fibroblasts, as a consequence of cell to cell adhesion (Oncogene 23:2600). Given the generally accepted, positive role of Stat3 in proliferation, the Stat3 activity increase observed in confluent cells, that is when cells do not divide, was an unexpected observation. Interestingly, by plating cells onto surfaces coated with fragments encompassing the two outermost domains of E-cadherin and cadherin-11, two members of the classical type I and II cadherin family of surface receptors, responsible for the formation of cell to cell junctions, we demonstrated that cadherin engagement per se can directly activate Stat3, in the absence of cell to cell contact. Examination of the mechanism of the cadherin-mediated, Stat3 activation unexpectedly revealed for the first time a dramatic surge in total Rac1 and Cdc42 protein levels by cadherin engagement, and a proportional increase in Rac1 and Cdc42 activity. Therefore, to examine the potential role of Rac/Cdc42 in the density-dependent, Stat3 activation, the ability of mutationally activated RacV12 to activate Stat3 at high cell densities was examined. The results revealed a dramatic increase in protein levels and activity of both the endogenous Rac and RacV12 with cell density, which was due to inhibition of proteasomal degradation in both cases. In addition, RacV12-expressing cells had higher Stat3, tyrosine-705 phosphorylation and activity levels at all densities, indicating that RacV12 is, in fact, able to activate Stat3. Further examination of the mechanism of Stat3 activation showed that both cadherin engagement and RacV12 expression caused a surge in mRNA of Interleukin-6 (IL6) family cytokines, known potent Stat3 activators. Knockdown of gp130, the common subunit of this family reduced Stat3 activity in densely growing normal, as well as in RacV12-transformed cells, indicating that the IL6 family may be responsible for the Stat3 activation both by cadherin engagement and Rac mutational activation. Indeed, Rac knockdown reduced the density-mediated, Stat3 activation, indicating that Rac is responsible for the Stat3 stimulation observed upon cadherin ligation. Inhibition of cadherin interactions using a peptide, a soluble cadherin fragment or genetic ablation induced apoptosis, pointing to a significant role of this pathway in cell survival signalling, a finding which could also have important therapeutic implications. (supported by CIHR, CBCF-Ontario chapter, US Army breast cancer program, NSERC and Breast Cancer Action Kingston). Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 991.</jats:p