Biomedical subjects

Richard Poulsom

Publications and source records attributed to Richard Poulsom.

58 records · Page 4Linked to original sources

PubMed2002

Variable nuclear localization of alpha-catenin in colorectal carcinoma.

The E-cadherin/catenin complex plays a major role in epithelial cell-cell adhesion. Both beta-catenin and gamma-catenin bind directly to the cytoplasmic domain of E-cadherin whereas alpha-catenin links the bound beta-catenin or gamma-catenin to the actin microfilament network of the cellular cytoskeleton. Significant changes in the expression and/or structure of members of the complex can occur in neoplasia. Several studies have reported on the nuclear localization of beta- and gamma-catenin and on their role in influencing the transcriptional activity of several proto-oncogenes. The cellular localization of alpha-catenin has not been studied in detail. The aim of this study was to investigate the cellular localization of alpha-catenin in colorectal carcinoma both in vitro and in vivo and to assess whether it might be relevant to tumor behavior. The expression of alpha-catenin was examined in a panel of colorectal carcinoma cell lines (SW480, SW620, HCT116, HT29, and Caco-2) using a combination of immunohistochemistry, confocal fluorescence microscopy, and Western blotting. The expression of alpha-catenin was also studied by immunohistochemistry in 15 sporadic colorectal adenomas, 30 sporadic colorectal adenocarcinomas, and their 13 lymph node metastases. From familial adenomatous polyposis patients, 20 adenomas and 5 adenocarcinomas were studied. Nuclear localization of alpha-catenin was detected in the colorectal carcinoma cell lines when the cells were dispersed rather than confluent. alpha-catenin was not detected in the nuclei in any of the sporadic or familial adenomas. However, it was detected in one sporadic and one familial adenocarcinoma but not in any of the lymph node deposits. alpha-catenin can localize to the nuclei of colorectal tumor cells, and this may be related to lack of perception of connection to adjacent cells.

Cell Nucleus↗

PubMed2002

Embryo transfer experiments and ovarian transplantation identify the ovary as the only site in which nuclear receptor interacting protein 1/RIP140 action is crucial for female fertility.

Spatial and temporal regulation of gene expression by a number of different nuclear receptors is critical in female reproduction. In this study we investigated whether the nuclear receptor corepressor nuclear receptor interacting protein 1 (Nrip1)/RIP140, which is essential for ovulation, is also required for postovulatory events, leading to pregnancy and parturition. Expression analysis indicated that Nrip1 is present in the uterus in stromal and glandular epithelial cells, primary decidual cells, and subsequently in differentiating decidual cells at the anti-mesometrial side of the implantation site. It also indicated a temporal regulation of Nrip1 in the corpora lutea at different stages of pregnancy, with increased levels at midgestation at approximately d 9.5 postcoitum (pc). By performing both embryo and ovarian transfer experiments we demonstrate that, provided the block to ovulation is by-passed, Nrip1(-/-) mice are capable of establishing and maintaining pregnancies. However, although the majority of offspring derived from ovarian transplantation survived, approximately 50% of embryos were resorbed by d 13.5 pc after embryo transfer, and the majority of pups were stillborn or died soon thereafter. Thus, although Nrip1 is differentially expressed in the reproductive tract, we conclude that the ovary is the only site in which its action is essential for fertility, with a crucial role in ovulation and a secondary role in the maintenance of pregnancy.

Adaptor Proteins, Signal Transducing↗

PubMed2001

The S100 family heterodimer, MRP-8/14, binds with high affinity to heparin and heparan sulfate glycosaminoglycans on endothelial cells.

The S100 family proteins MRP-8 (S100A8) and MRP-14 (S100A9) form a heterodimer that is abundantly expressed in neutrophils, monocytes, and some secretory epithelia. In inflamed tissues, the MRP-8/14 complex is deposited onto the endothelium of venules associated with extravasating leukocytes. To explore the receptor interactions of MRP-8/14, we use a model system in which the purified MRP-8/14 complex binds to the cell surface of an endothelial cell line, HMEC-1. This interaction is mediated by the MRP-14 subunit and is mirrored by recombinant MRP-14 alone. The cell surface binding of MRP-14 was blocked by heparin, heparan sulfate, and chondroitin sulfate B, and the binding sites were sensitive to heparinase I and trypsin treatment but not to chondroitinase ABC. Furthermore MRP-8/14 and MRP-14 did not bind to a glycosaminoglycan-minus cell line. MRP-14 has a high affinity for heparin (K(d) = 6.1 +/- 3.4 nm), and this interaction mimicked that with the endothelial cells. We therefore conclude that the MRP-8/14 complex binds to endothelial cells via the MRP-14 subunit interacting chiefly with heparan sulfate proteoglycans. CD36 and RAGE, two other putative receptors for MRP-8/14, were not expressed by HMEC-1 cells. This binding activity may explain the immobilization of the MRP-8/14 complex on endothelium that is observed in vivo.

Animals↗

PubMedDate not supplied

Selective binding of nucleotide probes by eosinophilic cationic protein during in situ hybridisation.

During in situ hybridisation on frozen and paraffin-embedded sections of bowel for IkappaB alpha, oligodeoxyribonucleotide probes were found to bind more avidly to eosinophils than target mRNA. This binding could not be obviated using strategies previously employed to block either binding of long DNA probes (200-mers) to eosinophils in bone marrow smears, or of riboprobes to eosinophils in sections of bowel, without removing specific hybridisation of probes. That this binding could arise through interaction of anionic oligodeoxyribonucleotides with eosinophil cationic protein, which has an unusually high pI, and is abundant in cytoplasmic granules of eosinophils, was demonstrated in vitro using real-time biomolecular interaction analysis with a BiacoreX instrument. Finally, a relationship between probe hydrophobicity, measured by reverse phase ion-pair high performance liquid chromatography, and in situ binding of individual probes to eosinophils was demonstrated. Effective tissue penetration by hydrophobic probes and subsequent strong probe-eosinophilic cationic protein interactions therefore may confound the interpretation of in situ hybridisation performed with oligonucleotide probes in eosinophil-containing tissues, such as bowel and nasal polyps.

Antisense Elements (Genetics)↗