The dendritic cell receptor for endocytosis, DEC-205, can recycle and enhance antigen presentation via major histocompatibility complex class II-positive lysosomal compartments

Many receptors for endocytosis recycle into and out of cells through early endosomes. We now find in dendritic cells that the DEC-205 multilectin receptor targets late endosomes or lysosomes rich in major histocompatibility complex class II (MHC II) products, whereas the homologous macrophage mannose receptor (MMR), as expected, is found in more peripheral endosomes. To analyze this finding, the cytosolic tails of DEC-205 and MMR were fused to the external domain of the CD16 Fcgamma receptor and studied in stable L cell transfectants. The two cytosolic domains each mediated rapid uptake of human immunoglobulin (Ig)G followed by recycling of intact CD16 to the cell surface. However, the DEC-205 tail recycled the CD16 through MHC II-positive late endosomal/lysosomal vacuoles and also mediated a 100-fold increase in antigen presentation. The mechanism of late endosomal targeting, which occurred in the absence of human IgG, involved two functional regions: a membrane-proximal region with a coated pit sequence for uptake, and a distal region with an EDE triad for the unusual deeper targeting. Therefore, the DEC-205 cytosolic domain mediates a new pathway of receptor-mediated endocytosis that entails efficient recycling through late endosomes and a greatly enhanced efficiency of antigen presentation to CD4(+) T cells.     

Phenology simulation model of Scotinophara lurida (Hemiptera: Pentatomidae)

A phenology simulation model was developed for Scotinophara lurida (Burmeister). The components for the model were a degree-day immigration flight model of overwintered adults, temperature-dependent developmental models of each stage, survival rates of each stage, and an adult oviposition model. A degree-day model for immigration flight of overwintered adults was developed with blacklight trap catch data by a Weibull function. Laboratory experiments using seven constant temperature regimens were conducted to determine the effect of temperature on the development of immature stages. Developmental rates of each immature stage fit well to a linear model. Distribution of developmental time for each immature stage was successfully modeled against physiological age by a Weibull function. To determine the temperature effect on longevity, fecundity, and survival of female adults, laboratory and greenhouse experiments were conducted. The adult developmental rate (1/median longevity) was described by a linear model. The oviposition model was developed incorporating the three components of average total fecundity, cumulative oviposition rate function, and survival rate function. The simulation model predicted the time of peak occurrences of life stages of S. lurida well.     

Concurrent expression of heme oxygenase-1 and p53 in human retinal pigment epithelial cell line

Heme oxygenase-1 (HO-1) is a stress-responsive protein that is known to regulate cellular functions such as cell proliferation, inflammation, and apoptosis. Here, we investigated the effects of HO activity on the expression of p53 in the human retinal pigment epithelium (RPE) cell line ARPE-19. Cobalt protoporphyrin (CoPP) induced the expression of both HO-1 and p53 without significant toxicity to the cells. In addition, the blockage of HO activity with the iron chelator DFO or with HO-1 siRNA inhibited the CoPP-induced expression of p53. Similarly, zinc protoporphyrin (ZnPP), an inhibitor of HO, suppressed p53 expression in ARPE-19 cells, although ZnPP increased the level of HO-1 protein while inhibiting HO activity. Also, CoPP-induced p53 expression was not affected by the formation of reactive oxygen species (ROS). Based on these results, we conclude that HO activity is involved in the regulation of p53 expression in a ROS-independent mechanism, and also suggest that the expression of p53 in ARPE-19 cells is associated with heme metabolites such as biliverdin/bilirubin, carbon monoxide, and iron produced by the activity of HO.     

Measuring similarities between gene expression profiles through new data transformations

Background  

Clustering methods are widely used on gene expression data to categorize genes with similar expression profiles. Finding an appropriate (dis)similarity measure is critical to the analysis. In our study, we developed a new measure for clustering the genes when the key factor is the shape of the profile, and when the expression magnitude should also be accounted for in determining the gene relationship. This is achieved by modeling the shape and magnitude parameters separately in a gene expression profile, and then using the estimated shape and magnitude parameters to define a measure in a new feature space.     

Molecular characterization of a novel thermostable mannose-6-phosphate isomerase from Thermus thermophilus

Mannose-6-phosphate isomerase catalyzes the interconversion of mannose-6-phosphate and fructose-6-phosphate. The gene encoding a putative mannose-6-phosphate isomerase from Thermus thermophilus was cloned and expressed in Escherichia coli. The native enzyme was a 29 kDa monomer with activity maxima for mannose 6-phosphate at pH 7.0 and 80 °C in the presence of 0.5 mM Zn²⁺ that was present at one molecule per monomer. The half-lives of the enzyme at 65, 70, 75, 80, and 85 °C were 13, 6.5, 3.7, 1.8, and 0.2 h, respectively. The 15 putative active-site residues within 4.5 Å of the substrate mannose 6-phosphate in the homology model were individually replaced with other amino acids. The sequence alignments, activities, and kinetic analyses of the wild-type and mutant enzymes with amino acid changes at His50, Glu67, His122, and Glu132 as well as homology modeling suggested that these four residues are metal-binding residues and may be indirectly involved in catalysis. In the model, Arg11, Lys37, Gln48, Lys65 and Arg142 were located within 3 Å of the bound mannose 6-phosphate. Alanine substitutions of Gln48 as well as Arg142 resulted in increase of K_m and dramatic decrease of k_cat, and alanine substitutions of Arg11, Lys37, and Lys65 affected enzyme activity. These results suggest that these 5 residues are substrate-binding residues. Although Trp13 was located more than 3 Å from the substrate and may not interact directly with substrate or metal, the ring of Trp13 was essential for enzyme activity.     

Regulation of 5-hydroxyeicosanoid dehydrogenase activity in monocytic cells

The requirement of DAG (diacylglycerol) to recruit PKD (protein kinase D) to the TGN (trans-Golgi network) for the targeting of transport carriers to the cell surface, has led us to a search for new components involved in this regulatory pathway. Previous findings reveal that the heterotrimeric Gbetagamma (GTP-binding protein betagamma subunits) act as PKD activators, leading to fission of transport vesicles at the TGN. We have recently shown that PKCeta (protein kinase Ceta) functions as an intermediate member in the vesicle generating pathway. DAG is capable of activating this kinase at the TGN, and at the same time is able to recruit PKD to this organelle in order to interact with PKCeta, allowing phosphorylation of PKD's activation loop. The most qualified candidates for the production of DAG at the TGN are PI-PLCs (phosphatidylinositol-specific phospholipases C), since some members of this family can be directly activated by Gbetagamma, utilizing PtdIns(4,5)P2 as a substrate, to produce the second messengers DAG and InsP3. In the present study we show that betagamma-dependent Golgi fragmentation, PKD1 activation and TGN to plasma membrane transport were affected by a specific PI-PLC inhibitor, U73122 [1-(6-{[17-3-methoxyestra-1,3,5(10)-trien-17-yl]amino}hexyl)-1H-pyrrole-2,5-dione]. In addition, a recently described PI-PLC activator, m-3M3FBS [2,4,6-trimethyl-N-(m-3-trifluoromethylphenyl)benzenesulfonamide], induced vesiculation of the Golgi apparatus as well as PKD1 phosphorylation at its activation loop. Finally, using siRNA (small interfering RNA) to block several PI-PLCs, we were able to identify PLCbeta3 as the sole member of this family involved in the regulation of the formation of transport carriers at the TGN. In conclusion, we demonstrate that fission of transport carriers at the TGN is dependent on PI-PLCs, specifically PLCbeta3, which is necessary to activate PKCeta and PKD in that Golgi compartment, via DAG production.