Epsin 1 is Involved in Recruitment of Ubiquitinated EGF Receptors into Clathrin-Coated Pits

Epsin consists of an epsin NH₂-terminal homology domain that promotes interaction with phospholipids, several AP-2-binding sites, two clathrin-binding sequences and several Eps15 homology domain-binding motifs. Epsin additionally possesses ubiquitin-interacting motifs (UIMs) and has been demonstrated to bind ubiquitinated cargo. We therefore investigated whether epsin promoted clathrin-mediated endocytosis of the ubiquitinated EGF receptor (EGFR). By immunoprecipitation, we found that epsin 1 interacted with ubiquitinated EGFR and that functional UIMs were essential for complex formation. Furthermore, RNA interference-mediated knockdown of epsin 1 was found to inhibit internalization of the EGFR, while having no effect on endocytosis of the transferrin receptor. Additionally, upon knockdown of epsin 1, translocation of the EGFR to central parts of clathrin-coated pits was inhibited. This supports the contention that epsin 1 promotes endocytosis of the ubiquitinated EGFR.     

In-Depth Proteome Analysis of Arabidopsis Leaf Peroxisomes Combined with in Vivo Subcellular Targeting Verification Indicates Novel Metabolic and Regulatory Functions of Peroxisomes

Peroxisomes are metabolically diverse organelles with essential roles in plant development. The major protein constituents of plant peroxisomes are well characterized, whereas only a few low-abundance and regulatory proteins have been reported to date. We performed an in-depth proteome analysis of Arabidopsis (Arabidopsis thaliana) leaf peroxisomes using one-dimensional gel electrophoresis followed by liquid chromatography and tandem mass spectrometry. We detected 65 established plant peroxisomal proteins, 30 proteins whose association with Arabidopsis peroxisomes had been previously demonstrated only by proteomic data, and 55 putative novel proteins of peroxisomes. We subsequently tested the subcellular targeting of yellow fluorescent protein fusions for selected proteins and confirmed the peroxisomal localization for 12 proteins containing predicted peroxisome targeting signals type 1 or 2 (PTS1/2), three proteins carrying PTS-related peptides, and four proteins that lack conventional targeting signals. We thereby established the tripeptides SLM> and SKV> (where > indicates the stop codon) as new PTS1s and the nonapeptide RVx₅HF as a putative new PTS2. The 19 peroxisomal proteins conclusively identified from this study potentially carry out novel metabolic and regulatory functions of peroxisomes. Thus, this study represents an important step toward defining the complete plant peroxisomal proteome.     

Hypotensive hypovolemia and hypoglycemia activate different hindbrain catecholamine neurons with projections to the hypothalamus

To better understand the involvement of hindbrain catecholamine neurons in hypovolemia-induced secretion of AVP, we injected antidopamine beta-hydroxylase saporin (DSAP) or unconjugated saporin (SAP) control solution into the hypothalamic paraventricular nucleus (PVH) of anesthetized rats to retrogradely lesion catecholamine neurons innervating magnocellular areas of the hypothalamus. Subsequently, hypotensive hypovolemia was induced by remote blood withdrawal (4.5 ml, 1 ml/min) using an intra-atrial catheter. Blood was sampled at 2, 5, 20, and 50 min after onset of blood withdrawal. The AVP response was severely impaired by DSAP. Peak responses at 50 min were 51 pg/ml in SAP control and 17 pg/ml in DSAP-lesioned rats, indicating the importance of catecholamine neurons for this response. We also measured AVP responses to osmotic challenge induced by administration of hypertonic saline (1 M, 15 ml/kg, sc) and to insulin-induced hypoglycemia. Osmotic challenge increased AVP levels, but the response was not impaired by DSAP, indicating that AVP neurons were not damaged by the DSAP injection. Insulin-induced hypoglycemia did not increase AVP levels in either DSAP- or SAP-treated rats. However, the same dose of insulin increased food intake and corticosterone secretion in SAP controls, and these responses were profoundly impaired by DSAP. Thus catecholamine neurons are required for both the AVP response to hypotensive hypovolemia and for feeding and corticosterone responses to hypoglycemia. Lack of an AVP response to insulin-induced hypoglycemia in intact rats therefore indicates that responses to hypovolemia and hypoglycemia are mediated by different catecholamine neurons under distinct sensory controls.     

Homoisoflavonoid derivatives from the roots of Ophiopogon japonicus and their in vitro anti-inflammation activity

Three new homoisoflavonoids (1?3) were isolated from the roots of Ophiopogon japonicus (Liliaceae). The structures of new metabolites were determined on the basis of spectroscopic analyses including 2D NMR. The anti-inflammatory activities of new compounds (1?3) were investigated by their effects on the release of the inflammatory chemokine eotaxin, stimulated by IL-4 and the combination of IL-4 and TNF-α in BEAS-2B cells, which mimics the in vivo conditions in bronchial allergic asthma.     

Population dynamics of Rattus argentiventer, Rattus losea, and Rattus rattus inhabiting a mixed-farming system in the Red River Delta, Vietnam

Rodent pests cause significant damage to lowland irrigated rice crops in the Red River Delta of northern Vietnam. Data from a 4-year study were examined to look at the population dynamics of the ricefield rat, Rattus argentiventer (representing 50% of captures), the lesser ricefield rat, Rattus losea (30% of captures), and the black rat, Rattus rattus complex (9% of captures) that inhabit the irrigated mixed-cropping system. We tested the hypothesis that these rodent species were breeding in response to the availability of high-quality food provided by crops rather than in response to rainfall. The abundance of rodents fluctuated annually, with a main peak following the spring rice crop, and a secondary peak following the summer rice crop. There was a strong relationship between the monthly abundance of rats and rainfall, but a weak relationship between monthly rates of increase and rainfall. There were distinct peaks in breeding activity during the reproductive stages of the rice crops suggesting that changes in crop stages were more important than rainfall in this seasonal, but irrigated agroecosystem. The modal litter size for R. argentiventer was 8 (mean of 8.67±0.20 SE, range 2–16), where the mode for R. losea, was 7 (mean of 7.32±0.15 SE, range 3–14). Management of these species needs to be conducted prior to the onset of the main breeding seasons.     

Investigation of Obesity Candidate Genes On Porcine Fat Deposition Quantitative Trait Loci Regions

Objectives: To investigate possible obesity candidate genes in regions of porcine quantitative trait loci (QTL) for fat deposition and obesity‐related phenotypes. Research Methods and Procedures: Chromosome mapping and QTL analyses of obesity candidate genes were performed using DNA panels from a reference pig family. Statistical association analyses of these genes were performed for fat deposition phenotypes in several other commercial pig populations. Results: Eight candidate genes were mapped to QTL regions of pig chromosomes in this study. These candidate genes also served as anchor loci to determine homologous human chromosomal locations of pig fat deposition QTL. Preliminary analyses of relationships among polymorphisms of individual candidate genes and a variety of phenotypic measurements in a large number of pigs were performed. On the basis of available data, gene‐gene interactions were also studied. Discussion: Comparative analysis of obesity‐related genes in the pig is not only important for development of marker‐assisted selection on growth and fat deposition traits in the pig but also provides for an understanding of their genetic roles in the development of human obesity.