Cancer progression: is inhibin alpha from Venus or Mars?

The inhibin field has been perplexed by the information that inhibin alpha is a tumour suppressor in mice yet is elevated in women with ovarian cancer. Furthermore, we have consistently observed a down-regulation or loss of inhibin alpha in prostate cancer patient samples and cell lines. However, our latest data have prompted us to re-evaluate the role of inhibin alpha in prostate and other cancers. Using the analogy of TGF-beta as a springboard for our hypothesis, we offer a unifying model whereby the previously conflicting observations in mice, men and women can be explained. We propose that initially inhibin alpha is tumour-suppressive and is expressed in benign and early-stage primary cancers. Tumour-suppressive inhibin alpha is then silenced as the tumour progresses but is reactivated as a pro-metastatic factor in advanced, aggressive cancers.     

Predictome: a database of putative functional links between proteins

The current deluge of genomic sequences has spawned the creation of tools capable of making sense of the data. Computational and high-throughput experimental methods for generating links between proteins have recently been emerging. These methods effectively act as hypothesis machines, allowing researchers to screen large sets of data to detect interesting patterns that can then be studied in greater detail. Although the potential use of these putative links in predicting gene function has been demonstrated, a central repository for all such links for many genomes would maximize their usefulness. Here we present Predictome, a database of predicted links between the proteins of 44 genomes based on the implementation of three computational methods—chromosomal proximity, phylogenetic profiling and domain fusion—and large-scale experimental screenings of protein–protein interaction data. The combination of data from various predictive methods in one database allows for their comparison with each other, as well as visualization of their correlation with known pathway information. As a repository for such data, Predictome is an ongoing resource for the community, providing functional relationships among proteins as new genomic data emerges. Predictome is available at http://predictome.bu.edu.     

VEGFR1 (Flt1) Regulates Rab4 Recycling to Control Fibronectin Polymerization and Endothelial Vessel Branching

The cell's main receptor for VEGF, VEGFR2 (Kdr) is one of the most important positive regulators of new blood vessel growth and its downstream signalling is well characterized. By contrast, VEGFR1 (Flt1) and the mechanisms by which this VEGF receptor promotes branching morphogenesis in angiogenesis remain relatively unclear. Here we report that engagement of VEGFR1 activates a Rab4A-dependent pathway that transports αvβ3 integrin from early endosomes to the plasma membrane, and that this is required for VEGF-driven fibronectin polymerization in endothelial cells. Furthermore, VEGFR1 acts to promote endothelial tubule branching in an organotypic model of angiogenesis via a mechanism that requires Rab4A and αvβ3 integrin. We conclude that a recycling pathway regulated by Rab4A is a critical effector of VEGFR1 during branching morphogenesis of the vasculature.     

Comparative analysis of the regulation of the interferon-inducible protein kinase PKR by Epstein-Barr virus RNAs EBER-1 and EBER-2 and adenovirus VAI RNA.

The interferon-inducible protein kinase PKR interacts with a number of small viral RNA species, including adenovirus VAI RNA and the Epstein-Barr virus-encoded RNA EBER-1. These RNAs bind to PKR and protect protein synthesis from inhibition by double-stranded RNA in the reticulocyte lysate system. Using a peptide phosphorylation assay we show here that EBER-1, like VAI, directly inhibits the activation of purified PKR. A second Epstein-Barr virus RNA, EBER-2, also regulates PKR. EBER-1, EBER-2 and VAI RNA exhibit mutually competitive binding to the native or recombinant enzyme, as assessed by U.V. crosslinking experiments and filter binding assays. The affinities of all three RNAs for PKR in vitro are similar (Kd = ca. 0.3 nM). Since this protein kinase has been proposed to exert a tumour suppressor function in vivo, the ability of EBER-1 to inhibit its activation suggests a role for this small RNA in cell transformation by Epstein-Barr virus.     

Phylogenetically related Argentinean and Australian Escherichia coli O157 isolates are distinguished by virulence clades and alternative Shiga toxin 1 and 2 prophages

Shiga toxigenic Escherichia coli O157 is the leading cause of hemolytic uremic syndrome (HUS) worldwide. The frequencies of stx genotypes and the incidences of O157-related illness and HUS vary significantly between Argentina and Australia. Locus-specific polymorphism analysis revealed that lineage I/II (LI/II) E. coli O157 isolates were most prevalent in Argentina (90%) and Australia (88%). Argentinean LI/II isolates were shown to belong to clades 4 (28%) and 8 (72%), while Australian LI/II isolates were identified as clades 6 (15%), 7 (83%), and 8 (2%). Clade 8 was significantly associated with Shiga toxin bacteriophage insertion (SBI) type stx(2) (locus of insertion, argW) in Argentinean isolates (P < 0.0001). In Argentinean LI/II strains, stx(2) is carried by a prophage inserted at argW, whereas in Australian LI/II strains the argW locus is occupied by the novel stx(1) prophage. In both Argentinean and Australian LI/II strains, stx(2c) is almost exclusively carried by a prophage inserted at sbcB. However, alternative q(933)- or q(21)-related alleles were identified in the Australian stx(2c) prophage. Argentinean LI/II isolates were also distinguished from Australian isolates by the presence of the putative virulence determinant ECSP_3286 and the predominance of motile O157:H7 strains. Characteristics common to both Argentinean and Australian LI/II O157 strains included the presence of putative virulence determinants (ECSP_3620, ECSP_0242, ECSP_2687, ECSP_2870, and ECSP_2872) and the predominance of the tir255T allele. These data support further understanding of O157 phylogeny and may foster greater insight into the differential virulence of O157 lineages.     

Cutting edge: induced indoleamine 2,3 dioxygenase expression in dendritic cell subsets suppresses T cell clonal expansion

In mice, immunoregulatory APCs express the dendritic cell (DC) marker CD11c, and one or more distinctive markers (CD8alpha, B220, DX5). In this study, we show that expression of the tryptophan-degrading enzyme indoleamine 2,3 dioxygenase (IDO) is selectively induced in specific splenic DC subsets when mice were exposed to the synthetic immunomodulatory reagent CTLA4-Ig. CTLA4-Ig did not induce IDO expression in macrophages or lymphoid cells. Induction of IDO completely blocked clonal expansion of T cells from TCR transgenic mice following adoptive transfer, whereas CTLA4-Ig treatment did not block T cell clonal expansion in IDO-deficient recipients. Thus, IDO expression is an inducible feature of specific subsets of DCs, and provides a potential mechanistic explanation for their T cell regulatory properties.     

Reconstitution of purified amphiphilic pig intestinal microvillus aminopeptidase. Mode of membrane insertion and morphology.

Pig intestinal microvillus aminopeptidase (EC 3.4.11.2) was reincorporated into lipid membranes by using either beta-octyl glucoside or sodium deoxycholate. The results showed that for this enzyme the deoxycholate-dialysis method was the preferable one. By using this method, microvillus aminopeptidase was inserted almost quantitatively into either phosphatidylcholine vesicles or microvillus-lipid vesicles. By proteolytic treatment of the vesicles, by probing the aminopeptidase with an inhibitory antibody and by monitoring the positioning of the anchor with the aid of [125I]iodonaphthyl azide, it was demonstrated that the catalytically active part was located outside the liposomes and the anchoring peptide(2) was associated with the membrane. Electron-microscopic observation on this model system demonstrated a dimeric symmetrical structure of aminopeptidase (dimensions about 13.5 nm X 5.5 nm) separated by a 5 nm gap from the membrane. This distance corresponds to a molecular weight of 2000-5000 for this junctional segment of the anchor connecting the intramembrane part of the anchor with the catalytically active main part of the aminopeptidase.     

Growth and morphological changes in the small and the large intestine in piglets during the first three days after birth.

Growth and morphological changes in the small and the large intestine of piglets were examined during the first three days after birth. There was a 72% increase in small intestinal weight, virtually all of which occurred during the first day and was due primarily to a 115% increase in the weight of the mucosa. Associated with the tissue weight gain there was a 24% increase in small intestinal length, a 15% increase in small intestinal diameter, a 33-90% increase in villus height and a 14-51% increase in villus diameter, during the first day. The cellular population in the small intestinal mucosa, as indicated by its DNA content, increased progressively with age, and at three days had increased by 84-154%. The percentage increase in mucosal DNA content was highest in the duodenum, intermediate in the jejunum and lowest in the ileum. Histological features and tissue protein contents revealed a transient epithelial cellular swelling related to intracellular accumulation of protein on the first day. Protein accumulation was evident in the jejunum and ileum but not in the duodenum. The positions of the nuclei in the epithelial cells suggested that on the first day protein absorption was at a more advanced stage in the jejunum and the proximal ileum than in the distal ileum. Large intestinal weight increased by 33% during the first day and had doubled by the third day, and this weight gain was due to both mucosal and non-mucosal tissue growth. Villus-like structures were observed in the caecum and the proximal colon in piglets at birth and one day after birth but not in piglets three days after birth. It is speculated that such villus-like structures may have a functional significance during the transition to complete dependence on oral nutrition in newborns.