Regulation of phenotypic transitions in the fungal pathogen Candida albicans

The human commensal fungus Candida albicans can cause not only superficial infections, but also life-threatening disease in immunocompromised individuals. C. albicans can grow in several morphological forms. The ability to switch between different phenotypic forms has been thought to contribute to its virulence. The yeast-filamentous growth transition and white-opaque switching represent two typical morphological switching systems, which have been intensively studied in C. albicans. The interplay between environmental factors and genes determines the morphology of C. albicans. This review focuses on the regulation of phenotypic changes in this pathogenic organism by external environmental cues and internal genes.

Serum detection of epidermal growth factor receptor gene mutations using mutant-enriched sequencing in Chinese patients with advanced non-small cell lung cancer

Epidermal growth factor receptor gene (EGFR) mutations are among the best predictive markers of the efficacy of EGFR tyrosine kinase inhibitor (EGFR-TKI) treatment. Mutations in the EGFR gene confer sensitivity to EGFR-TKIs in patients with advanced non-small cell lung cancer (NSCLC). This study determined the concordance rate of EGFR mutations in serum samples and tumour tissue from Chinese patients with advanced NSCLC and compared two detection methods: mutant-enriched polymerase chain reaction-based DNA sequencing and non-enriched sequencing. The EGFR mutation status in serum was consistent with that in paired tumour samples, with a concordance rate of 93.1% for mutant-enriched sequencing. In serum samples, mutant-enriched sequencing demonstrated sensitivity and specificity of 77.8% and 100%, respectively, and was more sensitive than the non-enriched assay. Mutant-enriched sequencing in serum may provide a non-invasive and sensitive method for detecting EGFR mutation status in patients with unresectable NSCLC.

Roles of Candida albicans Gat2, a GATA-type zinc finger transcription factor, in biofilm formation, filamentous growth and virulence

Candida albicans is the most common human fungal pathogen, causing not only superficial infections, but also life-threatening systemic disease. C. albicans can grow in several morphological forms including unicellular yeast-form, elongated hyphae and pseudohyphae. In certain natural environments, C. albicans also exists as biofilms, which are structured and surface-attached microbial communities. Transcription factors play a critical role in morphogenesis and biofilm development. In this study, we identified four adhesion-promoting transcription factors (Tec1, Cph1, Ume6 and Gat2) by screening a transcription factor overexpression library. Sequence analysis indicates that Gat2 is a GATA-type zinc finger transcription factor. Here we showed that the gat2/gat2 mutant failed to form biofilms on the plastic and silicone surfaces. Overexpression of GAT2 gene promoted filamentous and invasive growth on agar containing Lee's medium, while deletion of this gene had an opposite effect. However, inactivation of Gat2 had no obvious effect on N-acetyl-glucosamine (GlcNAc) induced hyphal development. In a mouse model of systemic infection, the gat2/gat2 mutant showed strongly attenuated virulence. Our results suggest that Gat2 plays a critical role in C. albicans biofilm formation, filamentous growth and virulence.

STAT3 gene polymorphisms and susceptibility to non-small cell lung cancer

Signal transducer and activator of transcription protein 3 (STAT3) has been implicated in cancer development and is recognized as a type of oncogene. However, association studies of single nucleotide polymorphisms (SNPs) in the STAT3 gene with cancer risk are rare and not available for lung cancer. We examined whether STAT3 polymorphisms are associated with the risk of non-small cell lung cancer (NSCLC). Eight SNPs in the STAT3 gene were genotyped by TaqMan assays in 326 NSCLC cases and 432 controls in a Chinese population. Significant decreased risk of NSCLC was observed for carriers of minor alleles rs4796793 (odds ratio (OR) = 0.68, 95% confidence interval (CI) = 0.51-0.92), rs7211777 (OR = 0.67, 95%CI = 0.50-0.90), rs12949918 (OR = 0.73, 95%CI = 0.54-0.97), rs744166 (OR = 0.69, 95%CI = 0.51-0.92), rs9912773 (OR = 0.75, 95%CI = 0.55-0.98), and rs3869550 (OR = 0.70, 95%CI = 0.53-0.94). The GGCGGC haplotype, comprised of minor alleles of the six NSCLC-associated SNPs, had a 0.78-fold (95%CI = 0.62-0.97) significantly decreased risk of NSCLC, as compared to the most common haplotype of CATACT. Stratification analyses by clinical stage showed that the trend for the association between STAT3 polymorphisms and NSCLC risk was present both for stage I/II and stage III/IV, and appeared moderately stronger for stage III/IV. We conclude that polymorphisms in the STAT3 gene may have a protective role in the development of NSCLC, particular of stage III/IV NSCLC.

Associations between metabolic syndrome and its components and alcohol drinking

AIMS

The relationship between alcohol drinking and metabolic syndrome (MetS) and its components are not fully confirmed, we examined relationship between alcohol drinking and MetS and its components.

METHODS

2,538 Mongolian people aged 20 or more were included in this study. The data for demographic characteristics, lifestyle factors, family history of hypertension, blood pressure (BP) measurements and physical examination were obtained, and fasting plasma glucose (FPG) and lipids examined for all participants. Associations between MetS and its components and alcohol drinking were analyzed with Logistic regression.

RESULTS

The risks of MetS associated with alcohol drinking and various drinking volume were not significant after adjustment for other variables. Alcohol drinking was significantly and positively associated with high BP and high TG, the multivariate adjusted OR (95% CI) of high BP and high TG for drinking were 1.399(1.109, 1.764) and 2.464(1.866, 3.252), respectively, compared with no drinking. However, drinking was inversely associated with low HDL-C, the multivariate adjusted OR (95% CI) of low HDL-C was 0.597(0.479, 0.745) for alcohol drinking compared with no drinking.

CONCLUSIONS

Alcohol drinking was significantly and positively associated with high BP and high TG, while alcohol drinking inversely associated with low HDL-C.

Intranasal localizability of odorants: influence of stimulus volume

When an odorant is presented to one side of the nose and air to the other, the ability to localize which side received the odorant depends upon trigeminal nerve stimulation. It has been shown that performance on this lateralization task increases as stimulus concentration increases. In this study, we determined the influences of stimulus volume and sex on the ability to localize each of 8 odorants presented at neat concentrations: anethole, geraniol, limonene, linalool, menthol, methyl salicylate, phenyl ethanol, and vanillin. At a low stimulus volume (11 mL), only menthol was localized at an above-chance level. At a high stimulus volume (21 mL), above-chance localization occurred for all odorants except vanillin. Women were significantly better than men in localizing menthol. Stimuli rated as most intense were those that were most readily localized. The detection performance measures, as well as rated intensity values, significantly correlated with earlier findings of the trigeminal detectability of odorants presented to anosmic and normosmic subjects. This study suggests that differences in stimulus volume may explain some discrepant findings within the trigeminal chemosensory literature and supports the concept that vanillin may be a "relatively pure" olfactory stimulus.

A soluble thymic stromal lymphopoietin (TSLP) antagonist, TSLPR-immunoglobulin, reduces the severity of allergic disease by regulating pulmonary dendritic cells

Recent studies show that thymic stromal lymphopoietin (TSLP) plays a critical role in the upstream phase of the allergic cascade to induce T helper type 2 cell (Th2)-dominant allergic diseases. However, the effect of blocking TSLP signalling with the soluble TSLP receptor (TSLPR), TSLPR-immunoglobulin (Ig), on asthma development needs further investigation. Here, we examined the effects of TSLPR-Ig on asthmatic airway inflammation and dendritic cell (DC) function. TSLPR-Ig (comprising the extracellular domain of murine TSLPR and an IgG2a Fc tail) purified from transfected COS-7 cells reduced the expression of CD40, CD80 and CD86 on TSLP-activated DCs in vitro. We also investigated the mechanisms underlying TSLPR-Ig-mediated amelioration of allergic airway inflammation in a murine asthma model. When TSLP signalling was blocked by intratracheal administration of TSLPR-Ig prior to sensitization, allergen-specific serum IgE levels, airway tissue inflammation, inflammatory cell infiltration and Th2 cytokine levels in the bronchiolar lavage fluid (BALF) were reduced significantly. This was because of the TSLP-Ig-mediated down-regulation of co-stimulatory molecule expression on pulmonary DCs. We also transferred bone marrow-derived mature DCs (mDCs) into the airways of asthmatic mice. Intratracheal administration of TSLPR-Ig prior to the transfer of mDCs reduced eosinophilic airway inflammation and Th2 differentiation significantly. Collectively, these data suggest that local use of TSLPR-Ig prevents airway inflammation, at least in part, by regulating DC function, and that blocking TSLP signalling using TSLPR-Ig may be a novel strategy for the treatment of asthma bronchiale.

Candida albicans Zcf37, a zinc finger protein, is required for stabilization of the white state

Candida albicans, the most prevalent human fungal pathogen, can switch stochastically between white and opaque phases. In this study, we identified Zcf37, a zinc finger protein, as a new regulator of white-opaque switching. Deletion of ZCF37 increased white-to-opaque switching frequency and stabilized the opaque state. Overexpression of ZCF37 promoted conversion of opaque cells to white phase, but needed existence of Efg1, a key regulator required for maintenance of the white state. Deletion of EFG1 abolished the effect of ectopically expressed Zcf37 on opaque-to-white switching, whereas ectopic expression of EFG1 promoted white cell formation without presence of Zcf37. Our results suggest that Zcf37 acts as an activator of white cell formation and a repressor of opaque state and functions upstream of Efg1.

Characterization of ORF29 of Bombyx mori nucleopolyhedrovirus

ORF 29 of Bombyx mori nucleopolyhedrovirus (BmNPV ORF29), a conserved gene among all the lepidopteran baculoviruses, was subjected to analysis of sequence and transcription/translation in the insect BmN cells in vitro. His-tagged BmNPV ORF29 fusion protein was expressed in Escherichia coli, purified and used for the production of an antiserum. All the homologs of BmNPV ORF29 in baculoviruses contain a Nudix motif with slight modifications in the N-terminal part. A 654 nts-long transcript of BmNPV ORF29 in BmN cells was detected at 3-48 hrs p.i. indicating the early nature of the gene. In the virus-infected cells, the BmNPV ORF29 protein of 26 K was present in both the cytoplasm and nucleus. In the virions, the protein was present in Budded virus (BV), but not in Occlusion-derived virus (ODV). These results suggest that BmNPV ORF29 is a functional ORF of BmNPV, which encodes a 26 K protein expressed in the early stage of infection cycle.

Proteomic analysis of 3T3-L1 preadipocytes having a higher cell proliferation rate after treatment with low-molecular-weight silk fibroin peptides

OBJECTIVES

Previous studies have reported that fibroin peptides can be used in a new strategy for development of anti-diabetic peptide drugs. In this study, we separated silk fibroin hydrolysates (SFH) containing silk fibroin peptides into four components according to their molecular weight and tested the effects of these together with three synthetic silk fibroin hexapeptides GAGAGS, GAGAGY, GAGAGA on cell proliferation of 3T3-L1 preadipocytes. The aim of this study was to investigate protein expression profiles of 3T3-L1 preadipocytes and those treated with SFH component Fraction I and the synthetic silk fibroin hexapeptide GAGAGS to be able to elucidate difference in protein expression between the 3T3-L1 preadipocytes and those treated with fibroin peptides Fraction I and GAGAGS.

MATERIALS AND METHODS

SFH was separated by dialysis. MTT assays were performed to test effects of SFH components and synthetic silk fibroin hexapeptides on 3T3-L1 preadipocyte proliferation. We generated proteome maps using two-dimensional gel electrophoresis and analysed them by peptide mass fingerprinting.

RESULTS

GAGAGS and peptide mixtures, Fraction I and Fraction II, had significant effect in promoting 3T3-L1 preadipocyte proliferation. In the proteomic analysis, 73 protein spots were successfully identified, including 15 which were differentially expressed.

CONCLUSIONS

Our results show that some silk fibroin peptides of low molecular weight SFH and hexapeptide GAGAGS affected 3T3-L1 preadipocyte proliferation.

Time-resolved pump-probe experiments at the LCLS

The first time-resolved x-ray/optical pump-probe experiments at the SLAC Linac Coherent Light Source (LCLS) used a combination of feedback methods and post-analysis binning techniques to synchronize an ultrafast optical laser to the linac-based x-ray laser. Transient molecular nitrogen alignment revival features were resolved in time-dependent x-ray-induced fragmentation spectra. These alignment features were used to find the temporal overlap of the pump and probe pulses. The strong-field dissociation of x-ray generated quasi-bound molecular dications was used to establish the residual timing jitter. This analysis shows that the relative arrival time of the Ti:Sapphire laser and the x-ray pulses had a distribution with a standard deviation of approximately 120 fs. The largest contribution to the jitter noise spectrum was the locking of the laser oscillator to the reference RF of the accelerator, which suggests that simple technical improvements could reduce the jitter to better than 50 fs.

Pre-transplant cytomegalovirus (CMV) serostatus remains the most important determinant of CMV reactivation after allogeneic hematopoietic stem cell transplantation in the era of surveillance and preemptive therapy

Between January 2001 and June 2008, 315 adult patients (median age 43 years, range 16-65) including 203 males and 112 females undergoing hematopoietic stem cell transplantation (HSCT) had serial monitoring for cytomegalovirus (CMV) followed by initiation of preemptive therapy. The majority (62.1%) had a conventional myeloablative transplant with 116 (36.9%) having a reduced-intensity conditioning (RIC) transplant, using either matched sibling/family (63.3%) or unrelated donors (36.7%). Graft source was peripheral blood stem cells in 257 (81.5%), bone marrow in 41 (13.1%), and cord blood in 16 (5.4%). T-cell depletion with anti-thymocyte globulin or alemtuzumab was used in 35%. Based upon CMV serostatus, patients were classified into low risk (donor [D]-/recipient [R]-), intermediate risk (D+/R-), or high risk (D-/R+ or D+/R+). Serial weekly monitoring for CMV viremia was performed using a qualitative polymerase chain reaction (PCR) and when positive, quantification was done using either pp65 antigen or a quantitative PCR. CMV reactivation was seen in 123 patients (39.1%) at a median of 50 days post HSCT (range 22-1978). CMV serostatus was the most important risk factor with incidence of 53% in the high-risk group (53.3%) compared with 10.2% in the intermediate risk and 0% in the low-risk group (P<0.0001). Other significant risk factors identified included use of alemtuzumab during conditioning (P=0.03), RIC transplants (P=0.06), and the presence of acute graft-versus-host disease (GVHD) (P<0.0001). On a multivariate analysis, CMV serostatus, RIC transplants, and acute GVHD remained independent predictors of CMV reactivation. All were treated with antiviral therapy with responses seen in 109 (88.6%). Sixteen patients (13%) developed CMV disease at a median of 59 days post HSCT (range 26 days-46 months), 8 of whom died. At a median follow up of 43 months (range 6-93), 166 patients (52.6%) are alive with a significantly higher survival among patients without CMV reactivation (57.2%) as compared with patients with CMV reactivation (45.5%; P=0.049). CMV reactivation and disease remains a major problem in high-risk patients undergoing allogeneic HSCT. Novel prophylactic measures such as immunotherapy and drug prophylaxis need to be considered in this specific group of patients.

Tec1 mediates the pheromone response of the white phenotype of Candida albicans: insights into the evolution of new signal transduction pathways

The newly evolved pheromone response pathway of the white cell phenotype of the opportunistic human pathogen Candida albicans provides a unique view of how signal transduction pathways evolve.

The way in which signal transduction pathways evolve remains a mystery, primarily because we have few examples of ones that have newly evolved. There are numerous examples of how signal transduction pathways in the same organism selectively share components, most notably between the signal transduction pathways in Saccharomyces cerevisiae for the mating process, the filamentation process, cell wall integrity, ascospore formation, and osmoregulation. These examples, however, have not provided insights into how such pathways evolve. Here, through construction of an overexpression library for 107 transcription factors, and through mutational analyses, we have identified the transcription factor Tec1 as the last component of the newly evolved signal transduction pathway that regulates the pheromone response of the white cell phenotype in Candida albicans. The elucidation of this last component, Tec1, establishes a comprehensive description of the pheromone response pathway in the white cell phenotype of C. albicans, providing a unique perspective on how new signal transduction pathways may evolve. The three portions of this new regulatory pathway appear to have been derived from three different ancestral programs still functional in C. albicans. The upstream portion, including signals, receptors, the trimeric G protein complex, and the MAP kinase cascade, was derived intact from the upstream portion of the opaque pheromone response pathway of the mating process; Tec1, the transcription factor targeted by the MAP kinase pathway, was derived from a filamentation pathway; and the white-specific downstream target genes were derived from an ancestral biofilm process. The evolution of this pheromone response pathway provides a possible paradigm for how such signal transduction pathways evolve.

Signal transduction pathways regulate the response of cells to changes in the extracellular environment. Here, we report the identification of Tec1 as the single effector transcription factor of the pheromone response pathway of the human pathogen Candida albicans white cell type. This newly evolved pathway provides us with a unique opportunity to investigate signal transduction pathway evolution. In the C. albicans white-opaque transition, mating-competent opaque cells release mating pheromone that induces mating-incompetent white cells to form a biofilm which facilitates mating of the former. Each of the three major portions of the pathway that regulates white cell pheromone response appears to be derived from an ancestral pathway that is still intact and functional in C. albicans. The upstream portion—including the pheromone, its receptor, trimeric G protein complex, and a MAP kinase cascade—appears to be derived from the mating response pathway; transcription factor Tec1 from the filamentation pathway; and Tec1 target genes from the biofilm biosynthesis pathway. We posit that the sharing of upstream signaling components coordinates white and opaque cell pheromone responses, yet the divergence of downstream pathway components allows each cell type to elicit a unique phenotypic outcome. The white cell pheromone response pathway therefore provides a paradigm for how other such pathways may have evolved.

N-acetylglucosamine induces white to opaque switching, a mating prerequisite in Candida albicans

To mate, the fungal pathogen Candida albicans must undergo homozygosis at the mating-type locus and then switch from the white to opaque phenotype. Paradoxically, opaque cells were found to be unstable at physiological temperature, suggesting that mating had little chance of occurring in the host, the main niche of C. albicans. Recently, however, it was demonstrated that high levels of CO(2), equivalent to those found in the host gastrointestinal tract and select tissues, induced the white to opaque switch at physiological temperature, providing a possible resolution to the paradox. Here, we demonstrate that a second signal, N-acetylglucosamine (GlcNAc), a monosaccharide produced primarily by gastrointestinal tract bacteria, also serves as a potent inducer of white to opaque switching and functions primarily through the Ras1/cAMP pathway and phosphorylated Wor1, the gene product of the master switch locus. Our results therefore suggest that signals produced by bacterial co-members of the gastrointestinal tract microbiota regulate switching and therefore mating of C. albicans.