Identification of a Novel Function of PiT1 Critical for Cell Proliferation and Independent of Its Phosphate Transport Activity

PiT1 is a Na⁺-phosphate (P_i) cotransporter located at the plasma membrane that enables P_i entry into the cell. Its broad tissue expression pattern has led to the idea that together with the closely related family member PiT2, PiT1 is the ubiquitous supplier of P_i to the cell. Moreover, the role of P_i in phosphorylation reactions, ATP production, DNA structure, and synthesis has led to the view that P_i availability could be an important determinant of cell growth. However, these issues have not been clearly addressed to date, and the role of either P_i or PiT proteins in cell proliferation is unknown. Using RNA interference in HeLa and HepG2 cells, we show that transient or stable PiT1 depletion markedly reduces cell proliferation, delays cell cycle, and impairs mitosis and cytokinesis. In vivo, PiT1 depletion greatly reduced tumor growth when engineered HeLa cells were injected into nude mice. We provide evidence that this effect on cell proliferation is specific to PiT1 and not shared by PiT2 and is not the consequence of impaired membrane Na⁺-P_i transport. Moreover, we show that modulation of cell proliferation by PiT1 is independent from its transport function because the proliferation of PiT1-depleted cells can be rescued by non-transporting PiT1 mutants. PiT1 depletion leads to the phosphorylation of p38 mitogen-activated protein (MAP) kinase, whereas other MAP kinases and downstream targets of mammalian target of rapamycin (mTOR) remain unaffected. This study is the first to describe the effects of a P_i transporter in cell proliferation, tumor growth, and cell signaling.     

Differential regulation of the human versus the mouse apolipoprotein AV gene by PPARalpha: Implications for the study of pharmaceutical modifiers of hypertriglyceridemia in mice

Mice have been used widely to define the mechanism of action of fibric acid derivatives. The fibrates are pharmacological agonists of the peroxisome proliferator-activated receptor α (PPARα), whose activation in human subjects promotes potent reduction in plasma levels of triglycerides (TG) with concomitant increase in those of HDL-cholesterol. The impact of PPARα agonists on gene expression in humans and rodents is however distinct; such distinctions include differential regulation of key genes of lipid metabolism. We evaluated the question as to whether the human and murine genes encoding apolipoprotein apoAV, a regulator of plasma concentrations of TG-rich lipoproteins, might be differentially regulated in response to fibrates. Fenofibrate, a classic PPARα agonist, repressed expression of mouse Apoa5 in vivo in a mouse model transgenic for the human APOA5 gene; by contrast, expression of the human ortholog was up-regulated. Our findings are consistent with the presence of a functional PPAR-binding element in the promoter of the human APOA5 gene; this element is however degenerate and non-functional in the corresponding mouse Apoa5 sequence, as demonstrated by reporter assays and gel shift analyses. These data further highlights the distinct mechanisms which are implicated in the metabolism of TG-rich lipoproteins in mice as compared to man. They equally emphasize the importance of the choice of a mouse model for investigation of the impact of pharmaceutical modifiers on hypertriglyceridemia.     

PTools: an opensource molecular docking library

Background  

Macromolecular docking is a challenging field of bioinformatics. Developing new algorithms is a slow process generally involving routine tasks that should be found in a robust library and not programmed from scratch for every new software application.     

In Very Young Infants Severity of Acute Bronchiolitis Depends On Carried Viruses

Background

RT amplification reaction has revealed that various single viruses or viral co-infections caused acute bronchiolitis in infants, and RV appeared to have a growing involvement in early respiratory diseases. Because remaining controversial, the objective was to determine prospectively the respective role of RSV, RV, hMPV and co-infections on the severity of acute bronchiolitis in very young infants.

Methods and Principal Findings

209 infants (median age: 2.4 months) were enrolled in a prospective study of infants <1 year old, hospitalized for a first episode of bronchiolitis during the winter epidemic season and with no high risk for severe disease. The severity was assessed by recording SaO₂% at admission, a daily clinical score (scale 0–18), the duration of oxygen supplementation and the length of hospitalization. Viruses were identified in 94.7% by RT amplification reaction: RSV only (45.8%), RV only (7.2%), hMPV only (3.8%), dual RSV/RV (14.3%), and other virus only (2%) or coinfections (9%). RV compared respectively with RSV and dual RSV/RV infection caused a significant less severe disease with a lower clinical score (5[3.2–6] vs. 6[4–8], p = 0.01 and 5.5[5–7], p = 0.04), a shorter time in oxygen supplementation (0[0–1] days vs. 2[0–3] days, p = 0.02 and 2[0–3] days, p = 0.03) and a shorter hospital stay (3[3–4.7] days vs.6 [5–8] days, p = 0.001 and 5[4–6] days, p = 0.04). Conversely, RSV infants had also longer duration of hospitalization in comparison with RSV/RV (p = 0.01) and hMPV (p = 0.04). The multivariate analyses showed that the type of virus carried was independently associated with the duration of hospitalization.

Conclusion

This study underlined the role of RV in early respiratory diseases, as frequently carried by young infants with a first acute bronchiolitis. RSV caused the more severe disease and conversely RV the lesser severity. No additional effect of dual RSV/RV infection was observed on the severity.     

Fat Depot‐specific Impact of Visceral Obesity on Adipocyte Adiponectin Release in Women

Our objective was to examine omental and subcutaneous adipocyte adiponectin release in women. We tested the hypothesis that adiponectin release would be reduced to a greater extent in omental than in subcutaneous adipocytes of women with visceral obesity. Omental and subcutaneous adipose tissue samples were obtained from 52 women undergoing abdominal hysterectomies (age: 47.1 ± 4.8 years; BMI: 26.7 ± 4.7 kg/m²). Adipocytes were isolated and their adiponectin release in the medium was measured over 2 h. Measures of body fat accumulation and distribution were obtained using dual‐energy X‐ray absorptiometry and computed tomography, respectively. Adiponectin release by omental and subcutaneous adipocytes was similar in lean individuals; however, in subsamples of obese or visceral obese women, adiponectin release by omental adipocytes was significantly reduced while that of subcutaneous adipocytes was not affected. Omental adipocyte adiponectin release was significantly and negatively correlated with total body fat mass (r = ?0.47, P < 0.01), visceral adipose tissue area (r = ?0.50, P < 0.01), omental adipocyte diameter (r = ?0.43, P < 0.01), triglyceride levels (r = ?0.32, P ≤ 0.05), cholesterol/high‐density lipoprotein (HDL)‐cholesterol (r = ?0.31, P ≤ 0.05), fasting glucose (r = ?0.39, P ≤ 0.01), fasting insulin (r = ?0.36, P ≤ 0.05), homeostasis model assessment index (r = ?0.39, P ≤ 0.01), and positively associated with HDL‐cholesterol concentrations (r = 0.33, P ≤ 0.05). Adiponectin release from subcutaneous cells was not associated with any measure of adiposity, lipid profile, or glucose homeostasis. In conclusion, compared to subcutaneous adipocyte adiponectin release, omental adipocyte adiponectin release is reduced to a greater extent in visceral obese women and better predicts obesity‐associated metabolic abnormalities.     

Vaccination against Human Influenza A/H3N2 Virus Prevents the Induction of Heterosubtypic Immunity against Lethal Infection with Avian Influenza A/H5N1 Virus

Annual vaccination against seasonal influenza viruses is recommended for certain individuals that have a high risk for complications resulting from infection with these viruses. Recently it was recommended in a number of countries including the USA to vaccinate all healthy children between 6 and 59 months of age as well. However, vaccination of immunologically naïve subjects against seasonal influenza may prevent the induction of heterosubtypic immunity against potentially pandemic strains of an alternative subtype, otherwise induced by infection with the seasonal strains.Here we show in a mouse model that the induction of protective heterosubtypic immunity by infection with a human A/H3N2 influenza virus is prevented by effective vaccination against the A/H3N2 strain. Consequently, vaccinated mice were no longer protected against a lethal infection with an avian A/H5N1 influenza virus. As a result H3N2-vaccinated mice continued to loose body weight after A/H5N1 infection, had 100-fold higher lung virus titers on day 7 post infection and more severe histopathological changes than mice that were not protected by vaccination against A/H3N2 influenza.The lack of protection correlated with reduced virus-specific CD8+ T cell responses after A/H5N1 virus challenge infection. These findings may have implications for the general recommendation to vaccinate all healthy children against seasonal influenza in the light of the current pandemic threat caused by highly pathogenic avian A/H5N1 influenza viruses.     

Genetic improvement of thermo-tolerance in wine Saccharomyces cerevisiae strains by a backcross approach

During red wine fermentation, high temperatures may cause stuck fermentation by affecting the physiology of fermenting yeast. This deleterious effect is the result of the complex interaction of temperature with other physicochemical parameters of grape juice, such as sugar and lipid content. The genetic background of fermenting yeast also interacts with this complex matrix and some strains are more resistant to high temperatures than others. Here, the temperature tolerance of nine commercial starters was evaluated, demonstrating that, at high sugar concentrations, half of them are sensitive to temperature. Using a classical backcross approach, one thermo-sensitive commercial starter was genetically improved by introducing quantitative trait loci conferring resistance to temperature. With this breeding program it is possible to obtain a thermo-resistant strain sharing most of its genome with the initial commercial starter. The parental and improved strains were compared for population growth and fermentation ability in various conditions. Despite their common genetic background, these two strains showed slight physiological differences in response to environmental changes that enable identification of the key physiological parameters influencing stuck fermentation.     

Evolution of Asthma Severity in a Cohort of Young Adults: Is There Any Gender Difference?

Introduction

Little is known about the distribution of asthma severity in men and women in the general population. The objective of our study was to describe asthma severity and change in severity according to gender in a cohort of adult asthmatics

Methods

Subjects with asthma were identified from random samples of the 22 to 44 year-olds from the general population, screened for asthma from 1991 to 1993 in 48 centers from 22 countries and followed-up during 1998–2002, as part of the European Community Respiratory Health Survey (ECRHS). All participants to follow-up with current asthma at baseline were eligible for the analysis. To assess change over the follow-up, asthma severity at the two surveys was defined using standardized data on respiratory symptoms, lung function and medication according to the Global Initiative for Asthma (GINA) Guidelines. Another quantitative score (Ronchetti) further considering hospitalizations was also analysed.

Results

The study included 685 subjects with asthma followed-up over a mean period of 8.65 yr (min 4.3-max 11.7). At baseline, asthma severity according to GINA was distributed as intermittent: 40.7%, 31.7% as mild persistent, 14% as moderate persistent, and 13.5% as severe persistent. Using the Ronchetti score derived classification, the distribution of asthma severity was 58% mild, (intermittent and mild persistent), 25.8% moderate, and 15.4% severe. Whatever the classification, there was no significant difference in the severity distribution between men and women. There was also no gender difference in the severity distribution among incident cases which developed asthma between the two surveys. Men with moderate-to-severe asthma at baseline were more likely than women to have moderate-to-severe asthma at follow-up. Using GINA, 69.2% of men vs. 53.1% of women (p = 0.09) with moderate-to-severe asthma at baseline were still moderate-to-severe at follow-up. Using Ronchetti score, 53.3% of men vs. 36.2% of women (p = 0.03) with moderate-to-severe asthma at baseline were still moderate-to-severe at follow-up.

Conclusions

There was no gender difference in asthma severity at the two surveys. However, our findings suggest that asthma severity might be less stable in women than in men.     

Origin and evolutionary plasticity of the gastric caecum in sea urchins (Echinodermata: Echinoidea)

Background  

The digestive tract of many metazoan invertebrates is characterized by the presence of caeca or diverticula that serve secretory and/or absorptive functions. With the development of various feeding habits, distinctive digestive organs may be present in certain taxa. This also holds true for sea urchins (Echinodermata: Echinoidea), in which a highly specialized gastric caecum can be found in members of a derived subgroup, the Irregularia (cake urchins, sea biscuits, sand dollars, heart urchins, and related forms). As such a specialized caecum has not been reported from "regular" sea urchin taxa, the aim of this study was to elucidate its evolutionary origin.