Linkers of Cell Polarity and Cell Cycle Regulation in the Fission Yeast Protein Interaction Network

The study of gene and protein interaction networks has improved our understanding of the multiple, systemic levels of regulation found in eukaryotic and prokaryotic organisms. Here we carry out a large-scale analysis of the protein-protein interaction (PPI) network of fission yeast (Schizosaccharomyces pombe) and establish a method to identify ‘linker’ proteins that bridge diverse cellular processes - integrating Gene Ontology and PPI data with network theory measures. We test the method on a highly characterized subset of the genome consisting of proteins controlling the cell cycle, cell polarity and cytokinesis and identify proteins likely to play a key role in controlling the temporal changes in the localization of the polarity machinery. Experimental inspection of one such factor, the polarity-regulating RNB protein Sts5, confirms the prediction that it has a cell cycle dependent regulation. Detailed bibliographic inspection of other predicted ‘linkers’ also confirms the predictive power of the method. As the method is robust to network perturbations and can successfully predict linker proteins, it provides a powerful tool to study the interplay between different cellular processes.     

SPARC Controls Melanoma Cell Plasticity through Rac1

Cell transition to a more aggressive mesenchymal-like phenotype is a hallmark of cancer progression that involves different steps and requires tightly regulated cell plasticity. SPARC (Secreted Protein Acidic and Rich in Cysteine) is a matricellular protein that promotes this transition in various malignant cell types, including melanoma cells. We found that suppression of SPARC expression in human melanoma cells compromised cell migration, adhesion, cytoskeleton structure, and cell size. These changes involved the Akt/mTOR pathway. Re-expression of SPARC or protein addition restored all the cell features. Suppression of SPARC expression was associated with increased Rac1-GTP levels and its membrane localization. Expression of the dominant negative mutant of Rac1 counteracted almost all the changes observed in SPARC-deficient cells. Overall, these data suggest that most of the SPARC-mediated effects occurred mainly through the blockade of Rac1 activity.     

Dependence of lung injury on surface tension during low-volume ventilation in normal open-chest rabbits.

To evaluate the role of pulmonary surfactant in the prevention of lung injury caused by mechanical ventilation (MV) at low end-expiratory volumes, lung mechanics and morphometry were assessed in three groups of eight normal, open-chest rabbits ventilated for 3-4 h at zero end-expiratory pressure (ZEEP) with physiological tidal volumes (Vt = 10 ml/kg). One group was left untreated (group A); the other two received surfactant intratracheally (group B) or aerosolized dioctylsodiumsulfosuccinate (group C) before MV on ZEEP. Relative to initial MV on positive end-expiratory pressure (PEEP; 2.3 cmH(2)O), quasi-static elastance (Est) and airway (Rint) and viscoelastic resistance (Rvisc) increased on ZEEP in all groups. After restoration of PEEP, only Rint (124%) remained elevated in group A, only Est (36%) was significantly increased in group B, whereas in group C, Est, Rint, and Rvisc were all markedly augmented (274, 253, and 343%). In contrast, prolonged MV on PEEP had no effect on lung mechanics of eight open-chest rabbits (group D). Lung edema developed in group C (wet-to-dry ratio = 7.1), but not in the other groups. Relative to group D, both groups A and C, but not B, showed histological indexes of bronchiolar injury, whereas all groups exhibited an increased number of polymorphonuclear leukocytes in alveolar septa, which was significantly greater in group C. In conclusion, administration of exogenous surfactant largely prevents the histological and functional damage of prolonged MV at low lung volumes, whereas surfactant dysfunction worsens the functional alterations, also because of edema formation and, possibly, increased inflammatory response.     

Prevalence survey of schistosomiasis in Mindanao and the Visayas, The Philippines

The first two phases of a national prevalence survey of schistosomiasis in The Philippines were completed in Mindanao in 2005 and the Visayas in the first quarter of 2007. The design was a stratified two-step systematic cluster sampling, with two Kato-Katz thick smears examined from each participant. In Mindanao, a total of 22 provinces spread in six regions were covered by the survey with five barangays (equivalent to a village) per province for a total of 110 barangays. The response rate was 70.9% with a total of 21,390 individuals examined. The province of Maguindanao, a known endemic area for schistosomiasis japonica, failed to take part in the survey. In the Visayas, 10 out of 11 provinces, spread out in three regions, participated in the survey. There were 6321 respondents for an overall participation rate of 32.2%. Mindanao showed a wider coverage of the disease than the Visayas (60% versus 45%). By region, Caraga or Region 13 ranked first in Mindanao and Region 8 in the Visayas. By province, Agusan del Sur is first on the list, followed by Northern Samar and then Eastern Samar. Overall, the prevalence rate among males is higher than that of females suggesting the occupational hazard of farming and fishing among the males. The higher exposure among farmers and fishermen is also borne out by the age distribution of the disease. Prevalence remains consistently high among the adults compared with the younger age groups. The survey also covered other helminth infections that can be detected in a stool survey, notably soil-transmitted helminthes and food-borne trematodes.     

Photophysical characterization and photodynamic activity of metallo 5-(4-(trimethylammonium)phenyl)-10,15,20-tris(2,4,6-trimethoxyphenyl)porphyrin in homogeneous and biomimetic media

The photophysical properties and photodynamic effect of Zn(ii), Pd(ii), Cu(ii) and free-base 5-(4-(trimethylammonium)phenyl)-10,15,20-tris(2,4,6-trimethoxy phenyl)porphyrin (H2P) iodide have been studied in N,N-dimethylformamide (DMF) and in different biomimetic systems. The absorption, fluorescence, triplet state and singlet molecular oxygen production of the metal complexes were all referred to H2P. The photodynamic activity was first analyzed using 9,10-dimethylanthracene and guanosine 5'-monophosphate in N,N-dimethylformamide. The photooxidation processes were also investigated in benzene/benzyl-n-hexadecyldimethyl ammonium chloride/water reverse micelles. Photosensitization efficiency of these porphyrins was H2P approximately ZnP > PdP in homogeneous solution and ZnP > H2P > PdP in micelles, whereas no photooxidation effect was detected using the Cu(ii) complex. Human erythrocytes were used as a biological membrane model. The photohemolytic activity depended on irradiation time, sensitizer and concentration of the agent. When cells were treated with 1 microM sensitizer, the hemolytic activity was H2P > ZnP > CuP. However, it was H2P > ZnP approximately CuP using 5 microM of the respective porphyrin. Although CuP could undergo a type I photoreaction, in all cases the photohemolytic effect considerably diminishes in anoxic conditions, indicating that an oxygen atmosphere is required for the mechanism of cellular membrane damage. The behavior of these amphiphilic metallo porphyrins provides information on the photodynamic activity of these agents in biomimetic microenvironments.     

Silencing survivin gene expression promotes apoptosis of human breast cancer cells through a caspase-independent pathway

Survivin is recognized as an attractive target in cancer therapy because of its selective overexpression in the majority of tumors. Upregulated expression of this protein correlates with increased tumor grade, recurrence risk and decreased cancer patients survival. In this study, we assessed the efficacy of two survivin-specific small interfering RNA (siRNA) constructs to inhibit T47D human breast cancer cell growth. After siRNA transfection, T47D cells showed a significant reduction in proliferation and survival exhibiting clear signs of apoptosis. pSil_1 that targeted exon 1 exhibited a stronger inhibitory effect on cell growth, and increased cell apoptosis compared to pSil_30 that targeted exon 4. Cell apoptosis was found to be mediated by translocation of the mitochondrial apoptosis inducing factor (AIF), while no changes were observed in caspase-3 activation and Bid cleavage. Thus, silencing survivin expression using siRNA strategies represents a suitable therapeutic approach to selectively modulate the survival and growth of human breast cancer cells.     

Life history of the bird cherry-oat aphid, Rhopalosiphum padi, on transgenic and non-transformed wheat challenged with Wheat streak mosaic virus

The life history of the bird cherry-oat aphid, Rhopalosiphum padi (L.) (Hemiptera: Aphididae), was studied via laboratory assays on Wheat streak mosaic virus (WSMV)-infected and non-infected transgenic and non-transformed wheat [ Triticum aestivum L. (Poaceae)]. Although R. padi is not a WSMV vector, it is known to colonize WSMV-infected wheat plants. Two transgenic soft white winter wheat genotypes, 366-D03 and 366-D8, that express the WSMV coat protein gene, and the WSMV-susceptible non-transformed cultivar Daws were tested. All genotypes showed disease symptoms when infected with WSMV. Whereas plant height was significantly reduced on virus-infected compared to non-infected plants of all genotypes, virus-infected transgenic plants exhibited lower virus titer and lower disease rating scores than Daws. No significant effects of WSMV infection or genotypes were observed on the length of R. padi nymphal development period, nor on their pre-, and post-reproductive periods. Rhopalosiphum padi reproductive period was significantly longer on Daws infected with WSMV than on non-infected plants of this cultivar. In contrast, there were no significant differences in length of R. padi reproductive period between virus-infected and non-infected transgenic plants within a genotype. Rhopalosiphum padi daily fecundity was significantly lower and adult longevity significantly longer on virus-infected than on non-infected plants of all genotypes. Total aphid fecundity and intrinsic rate of increase were not significantly different among treatments. The percentage of winged aphids that developed was greater on WSMV-infected compared to non-infected plants within a genotype. Results indicate that both virus infection status of plants and wheat genotype influence the life history of R. padi.