Zinc-induced PTEN protein degradation through the proteasome pathway in human airway epithelial cells

The tumor suppressor PTEN is a putative negative regulator of the phosphatidylinositol 3-kinase/Akt pathway. Exposure to Zn2+ ions induces Akt activation, suggesting that PTEN may be modulated in this process. Therefore, the effects of Zn2+ on PTEN were studied in human airway epithelial cells and rat lungs. Treatment with Zn2+ resulted in a significant reduction in levels of PTEN protein in a dose- and time-dependent fashion in a human airway epithelial cell line. This effect of Zn2+was also observed in normal human airway epithelial cells in primary culture and in rat airway epithelium in vivo. Concomitantly, levels of PTEN mRNA were also significantly reduced by Zn2+ exposure. PTEN phosphatase activity evaluated by measuring Akt phosphorylation decreased after Zn2+ treatment. Pretreatment of the cells with a proteasome inhibitor significantly blocked zinc-induced reduction of PTEN protein as well as the increase in Akt phosphorylation, implicating the involvement of proteasome-mediated PTEN degradation. Further study revealed that Zn2+-induced ubiquitination of PTEN protein may mediate this process. A phosphatidylinositol 3-kinase inhibitor blocked PTEN degradation induced by Zn2+, suggesting that phosphatidylinositol 3-kinase may participate in the regulation of PTEN. However, both the proteasome inhibitor and phosphatidylinositol 3-kinase inhibitor failed to prevent significant down-regulation of PTEN mRNA expression in response to Zn2+. In summary, exposure to Zn2+ ions causes PTEN degradation and loss of function, which is mediated by an ubiquitin-associated proteolytic process in the airway epithelium.     

Synthesis,characterization and antitumor activity of novel octahedral Pt(IV) complexes

Novel platinum(IV) complexes were synthesized having octahedral structure for new antitumor agents. The series of (1,4-butanediamine)Pt(IV) complexes of the type trans,cis-[PtA(2)Cl(2)(1,4-butanediamine)] (A=hydroxo 9, acetato 12, trifluoroacetato 13 as axial ligands) and trans-[PtA(2)(malonate)(1,4-butanediamine)] (A=hydroxo 16, acetato 17, trifluoroacetato 18) were synthesized and characterized by IR, NMR and elemental analysis. The molecular structures of 12, 13 and 18 have been determined by X-ray diffraction methods. The crystals are monoclinic, P2 1/c with a=21.165 (5), b=9.050 (3), c=15.293 (3) A, beta=103.89 (2) degrees and Z=8 for 12, a=10.178 (5), b=12.894 (9), c=12.182 (8) A, beta=91.01 (5) degrees and Z=4 for 13 and a=10.460 (5), b=11.199 (8), c=15.641 (7) A, beta=98.41 (5) degrees, Z=4 for 18. Three crystallographically independent molecules of 12, 13 and 18 have octahedral coordination around Pt(IV) cation. The trans,cis-[PtA(2)Cl(2)(1,4-butanediamine)] were prepared by acetylation or trifluoroacetylation of trans,cis-[Pt(OH)(2)Cl(2)(1,4-butanediamine)]. The trans-[PtA(2)malonate(1,4-butanediamine)] 17 and 18 was prepared by a similar method. The in vitro cytotoxicity of theses Pt(IV) complexes have been evaluated against 12 cancer cell lines assayed by MTS method. The IC(50) values of the compounds 12 and 13 were shown to be lower than those of cisplatin. The in vivo antitumor activity of the Pt(IV) complexes was evaluated using mice bearing L1210 leukemia, B16 melanoma and L1210/cis-DDP cancer animal models. The compound 18 was found to highest activity against cisplatin-resistant cancer cells, L1210/cis-DDP, in vivo.     

Intragenomic length variation of the ribosomal DNA intergenic spacer in a malaria vector,Anopheles sinensis

We determined the complete sequences of six size variants of intergenic spacer (IGS) region from one individual of the malaria vector mosquito species, Anopheles sinensis. All six size variants observed in this study show almost the same basic primary structure in which three repeat regions (A, B, and C) are interspersed by highly conserved nonrepeating sections. In contrast to the well-ordered subrepeating patterns found in A and C, the repeat region B displays extremely variable and complicated profiles in the number and arrangement of subrepeat units among different size classes. It is apparent that the prominent level of length difference in the repeat regions B and C is responsible for the intragenomic length variations of the IGS molecule observed in the present study. High level of sequence homology and regularly arranged repeating pattern of 11 to 14 bp motif sequences harbored within the B repeat region allow us to consider that these motif sequences may be associated with their potential role as a recombination site. Compared to those previously published in other mosquito species, the IGS of A. sinensis showed a very unique structural format in subrepeat patterns of the IGS region. This result suggests that the structure and sequence profiles of the IGS region would provide useful information for the exploitation of a convenient molecular marker to identify morphologically complicated species complex and to characterize the genetic variation of population. This suggestion is far from being conclusive at present, but a further genetic study will bring more compelling evidences for this pending issue.     

GIP,a G-protein-coupled receptor interacting protein

A novel protein was cloned while screening for partners interacting with the second intracellular loop of the V2 vasopressin receptor (V2R). The protein was named GIP as in G-protein-coupled receptor Interacting Protein; the corresponding gene was located on the 17th chromosome where three exons encode for a 379-amino-acid protein.GIP subcellular localization was studied by immunocytochemistry and also using a biotinylating agent. The protein was found to be localized, at least in part, on the plasma membrane, probably in the form of a trimer.The results indicated that GIP is a transmembrane protein and the most part of the molecule is intracellular. Sequence homology inferred that GIP cytosolic domain is folded as a collagen-like helix followed by a globular domain.The interaction of the globular domain with the V2R was confirmed by pull-down experiments indicating that this structural motif can also interact with cytosolic proteins.     

Variation of silica bodies in leaf epidermal long cells within and among seventeen species of Oryza (Poaceae)

Morphometric procedures were used with scanning electron microscopy backscattered images to study silica bodies in epidermal long cells of four different leaf veins of 17 of the 20 species of Oryza. The veins studied were midrib, large vein, small vein, and marginal vein. Image analysis was used to study morphological variations among the silica bodies. Statistical analyses were based on 11 variables. Even within a single leaf, silica bodies were not uniform. However, the degree of morphological variation normally showed a distribution of morpholgical types around one modal shape. The most significant differences observed were between silica bodies of the midrib and those of other veins. Bodies varied with respect to both size and shape. Computer-assisted image analysis is an effective tool for categorizing basic data and for statistical analysis of variation among silica bodies. Morphological variation among silica bodies of a single leaf may be related to water-conducting systems and their influence on silica availability and phytolith formation.     

Luminal and systemic signals trigger intestinal adaptation in the juvenile python

Juvenile pythons undergo large rapid upregulation of intestinal mass and intestinal transporter activities upon feeding. Because it is also easy to do surgery on pythons and to maintain them in the laboratory, we used a python model to examine signals and agents for intestinal adaptation. We surgically isolated the middle third of the small intestine from enteric continuity, leaving its mesenteric nerve and vascular supply intact. Intestinal continuity was restored by an end-to-end anastomosis between the proximal and distal thirds. Within 24 h of the snake's feeding, the reanastomosed proximal and distal segments (receiving luminal nutrients) had upregulated amino acid and glucose uptakes by up to 15-fold, had doubled intestinal mass, and thereby soon achieved total nutrient uptake capacities equal to those of the normal fed full-length intestine. At this time, however, the isolated middle segment, receiving no luminal nutrients, experienced no changes from the fasted state in either nutrient uptakes or in morphology. By 3 days postfeeding, the isolated middle segment had upregulated nutrient uptakes to the same levels as the reanastomosed proximal and distal segments, but it still lacked any appreciable morphological response. These contrasting results for the reanastomosed intestine and for the isolated middle segment suggest that luminal nutrients and/or pancreatic biliary secretions are the agents triggering rapid upregulation of transporters and of intestinal mass and that systemic nerve or hormonal signals later trigger transporter regulation but no trophic response.     

Characterization of Incidental Liver Lesions: Comparison of Multidetector CT versus Gd-EOB-DTPA-Enhanced MR Imaging

As a result of recent developments in imaging modalities and wide spread routine medical checkups and screening, more incidental liver lesions are found frequently on US these days. When incidental liver lesions are found on US, physicians have to make a decision whether to just follow up or to undergo additional imaging studies for lesion characterization. In order to choose the next appropriate imaging modality, the diagnostic accuracy of each imaging study needs to be considered. Therefore, we tried to compare the accuracy of contrast-enhanced multidetector CT (MDCT) and Gd-EOB-DTPA-enhanced MRI for characterization of incidental liver masses. We included 127 incidentally found focal liver lesions (94 benign and 33 malignant) from 80 patients (M∶F = 45∶35) without primary extrahepatic malignancy or chronic liver disease. Two radiologists independently reviewed Gd-EOB-DTPA-enhanced MRI and MDCT. The proportion of confident interpretations for differentiation of benign and malignant lesions and for the specific diagnosis of diseases were compared. The proportion of confident interpretations for the differentiation of benign and malignant lesions was significantly higher with EOB-MRI(94.5%–97.6%) than with MDCT (74.0%–92.9%). In terms of specific diagnosis, sensitivity and accuracy were significantly higher with EOB-MRI than with MDCT for the diagnosis of focal nodular hyperplasia (FNH) and focal eosinophilic infiltration. The diagnoses of the remaining diseases were comparable between EOB-MRI and MDCT. Hence, our results suggested that Gd-EOB-MRI may provide a higher proportion of confident interpretations than MDCT, especially for the diagnosis of incidentally found FNH and focal eosinophilic infiltration.     

Differential immune response of adipocytes to virulent and attenuated Mycobacterium tuberculosis

Mycobacterium tuberculosis (M. tb) takes advantage of various cell types, allowing it to remain in the host for long periods. Because adipocytes have been proposed as niches for dormant M. tb in the latent state, understanding the interaction of virulent M. tb with adipocytes is important. We compared changes in cytokine secretion from 3T3-L1 murine adipocytes infected with virulent M. tb H37Rv (V-M. tb) and attenuated M. tb H37Ra (A-M. tb) strains. Both strains maintained non-replicating states within adipocytes until 10 days post-infection. Adipocytes infected with V-M. tb secreted lower levels of pro-inflammatory cytokines, such as tumor necrosis factor-α, interleukin (IL)-12p40, IL-6, and IL-17, and lower levels of nitric oxide than those infected with A-M. tb. In contrast, the anti-inflammatory cytokines, IL-10 and IL-4, were markedly induced in V-M. tb-infected adipocytes versus those infected with A-M. tb at an early time point. Heat-killed or formalin-fixed bacteria induced lower levels of cytokines and no difference was observed between strains. Moreover, V-M. tb induced a high level of necrosis versus A-M. tb in conjunction with increased levels of LHD. These results suggest that V-M. tb regulates cytokine expression in its favor, increasing cytokines necessary for immune evasion and decreasing those required for protective immunity.