Probing the structure and function of human glutaminase-interacting protein: a possible target for drug design

PDZ domains are one of the most ubiquitous protein-protein interaction modules found in living systems. Glutaminase interacting protein (GIP), also known as Tax interacting protein 1 (TIP-1), is a PDZ domain-containing protein, which plays pivotal roles in many aspects of cellular signaling, protein scaffolding and modulation of tumor growth. We report here the overexpression, efficient refolding, single-step purification, and biophysical characterization of recombinant human GIP with three different C-terminal target protein recognition sequence motifs by CD, fluorescence, and high-resolution solution NMR methods. It is clear from our NMR analysis that GIP contains 2 alpha-helices and 6 beta-strands. The three target protein C-terminal recognition motifs employed in our interaction studies are glutaminase, beta-catenin and FAS. This is the first report of GIP recognition of the cell surface protein FAS, which belongs to the tumor necrosis factor (TNF) receptor family and mediates cell apoptosis. The dissociation constant ( K D) values for the binding of GIP with different interacting partners as measured by fluorescence spectroscopy range from 1.66 to 2.64 microM. Significant chemical shift perturbations were observed upon titration of GIP with above three ligands as monitored by 2D {(1)H, (15)N}-HSQC NMR spectroscopy. GIP undergoes a conformational change upon ligand binding.     

Optimization of invertase immobilization by adsorption in ionic exchange resin for sucrose hydrolysis

This work presents as a main objective to study the immobilization process of yeast invertase by adsorption in the ion exchanging resin Duolite A-568 for invert sugar production. Initially, a kinetic study of the soluble form of the enzyme was carried out. At the sequence was studied the immobilization process of yeast invertase in the weakly exchanging anionic resin Duolite A-568. The influences of the pH, enzyme concentration and temperature in the enzyme immobilization were analyzed through a central composite design (CCD). The results indicated that the retention of the catalytic activity in immobilization was strongly dependent of these variables, being maximum in a pH value of 5.0, with an enzyme concentration of 12.5 g/L (1.875 g of protein per liter) and temperature of 30 °C. The simultaneous influence of pH and temperature on the free and immobilized invertase activity was also studied through a CCD.     

The Role of Endangered Species Reintroduction in Ecosystem Restoration: Tortoise–Cactus Interactions on Española Island, Galápagos

We evaluated the role that endangered species reintroduction efforts can play in the larger context of ecosystem restoration. To do so, we examined interactions between endangered giant tortoises (Geochelone nigra hoodensis), currently being reintroduced to Isla Española, Galápagos, and an arboreal cactus (Opuntia megasperma var. megasperma), which is itself endangered and a keystone resource for many animals on the island. We collected information on spatial patterns of occurrence of cacti, tortoises, and woody vegetation and compared recruitment of juvenile cacti in areas occupied versus unoccupied by tortoises. Reintroduced tortoises appeared to suppress cactus recruitment near the few remaining adult cacti at the study site, but facilitate it at longer distances, with tortoise–cactus interactions mediated by the presence of woody vegetation, which likely alters tortoise movements and thereby patterns of cactus seed dispersal. The net effect of tortoises on cacti appeared to be positive insofar as tortoise presence was associated with greater recruitment of juveniles into cactus populations. Our study provides support for reintroducing endangered reptiles and other animals to aid ecosystem restoration in areas where they might once have played an important role in grazing upon and dispersing plants.     

Does wintering north or south of the Sahara correlate with timing and breeding performance in black‐tailed godwits?

Migrating long distances requires time and energy, and may interact with an individual's performance during breeding. These seasonal interactions in migratory animals are best described in populations with disjunct nonbreeding distributions. The black‐tailed godwit (Limosa limosa limosa), which breeds in agricultural grasslands in Western Europe, has such a disjunct nonbreeding distribution: The majority spend the nonbreeding season in West Africa, while a growing number winters north of the Sahara on the Iberian Peninsula. To test whether crossing the Sahara has an effect on breeding season phenology and reproductive parameters, we examined differences in the timing of arrival, breeding habitat quality, lay date, egg volume, and daily nest survival among godwits (154 females and 157 males), individually marked in a breeding area in the Netherlands for which wintering destination was known on the basis of resightings. We also examined whether individual repeatability in arrival date differed between birds wintering north or south of the Sahara. Contrary to expectation, godwits wintering south of the Sahara arrived two days earlier and initiated their clutch six days earlier than godwits wintering north of the Sahara. Arrival date was equally repeatable for both groups, and egg volume larger in birds wintering north of the Sahara. Despite these differences, we found no association between wintering location and the quality of breeding habitat or nest survival. This suggests that the crossing of an important ecological barrier and doubling of the migration distance, twice a year, do not have clear negative reproductive consequences for some long‐distance migrants.     

Continuous zebularine treatment effectively sustains demethylation in human bladder cancer cells

During tumorigenesis, tumor suppressor and cancer-related genes are commonly silenced by aberrant DNA methylation in their promoter regions. Recently, we reported that zebularine [1-(beta-D-ribofuranosyl)-1,2-dihydropyrimidin-2-one] acts as an inhibitor of DNA methylation and exhibits chemical stability and minimal cytotoxicity both in vitro and in vivo. Here we show that continuous application of zebularine to T24 cells induces and maintains p16 gene expression and sustains demethylation of the 5' region for over 40 days, preventing remethylation. In addition, continuous zebularine treatment effectively and globally demethylated various hypermethylated regions, especially CpG-poor regions. The drug caused a complete depletion of extractable DNA methyltransferase 1 (DNMT1) and partial depletion of DNMT3a and DNMT3b3. Last, sequential treatment with 5-aza-2'-deoxycytidine followed by zebularine hindered the remethylation of the p16 5' region and gene resilencing, suggesting the possible combination use of both drugs as a potential anticancer regimen.     

An evolving neural network for the interpretation of gene expression patterns

It is of central interest in biology to understand how gene activity networks are coordinated and integrated in the cell. Within the field of genomics, microarray technologies have become a powerful technique for monitoring simultaneously the expression patterns of thousands of genes under different sets of conditions. A main task now is to propose analytical methods that can suggest which groups of genes are activated by similar conditions. We review several techniques based on self-organizing map and clustering algorithms but implemented through a network of units controlled by biologically inspired functions (see Table 1). The computer tool, named NBIA, permits a categorization that generates a set of gene groups with coordinated expression patterns.     

A nitrophenyl-based prodrug type for colorectal targeting of prednisolone,budesonide and celecoxib

Celecoxib is a COX-2 inhibitor drug that can be used to reduce the risk of colorectal adenocarcinoma. Glucocorticoids are used in the treatment of inflammatory bowel disease. A limitation to the use of both drug types is that they undergo absorption from the intestinal tract with serious side effects. The prodrug systems introduced here involve forming a nitro-substituted acylsulfonamide group in the case of celecoxib and a nitro-substituted 21-ester for the glucocorticoids. Drug release is triggered by the nitro reductase action of the colonic microflora, liberating a cyclization competent species. The release of the active parent drugs was evaluated in vitro using Clostridium perfringens and epithelial transport through Caco-2 monolayer evaluation was carried out to estimate the absorption properties of the prodrugs compared to the parental drugs.     

Fluorine level in the bone and cartilage in children treated with ciprofloxacin (data obtained from the femur distal part]

Comparative data on the content of fluorine in various sections of the left femur distal part, i.e. spongy bone, process zone and articular cartilage are presented. The examination was performed on postmortem sections from 10 pediatric cases (the average age of 9.5 years) with mucoviscidosis or aplastic anemia treated before the death for up to 12 months with ciprofloxacin in a dose of 20 to 40 mg/kg body weight. The control postmortem sections were from 10 practically healthy children (the average age of 10.4 years) killed in a car accident. The sections were subjected to 2-stage dry ashing with ionometric determination of the fluorine ions. The results were treated according to the V.Yu. Urbach procedure. It was shown that the content of fluorine in the sponge bone and process zone in both the groups did not significantly differ. A comparatively high content of fluorine was detected only in the postmortem sections of the articular cartilage from the children of the main group who however had no chondrotoxic symptoms while alive. That means that the difference is statistically and clinically insignificant.