Impact of Aspergillus fumigatus in allergic airway diseases

For decades, fungi have been recognized as associated with asthma and other reactive airway diseases. In contrast to type I-mediated allergies caused by pollen, fungi cause a large number of allergic diseases such as allergic bronchopulmonary mycoses, rhinitis, allergic sinusitis and hypersensitivity pneumonitis. Amongst the fungi, Aspergillus fumigatus is the most prevalent cause of severe pulmonary allergic disease, including allergic bronchopulmonary aspergillosis (ABPA), known to be associated with chronic lung injury and deterioration in pulmonary function in people with chronic asthma and cystic fibrosis (CF). The goal of this review is to discuss new understandings of host-pathogen interactions in the genesis of allergic airway diseases caused by A. fumigatus. Host and pathogen related factors that participate in triggering the inflammatory cycle leading to pulmonary exacerbations in ABPA are discussed

Identification of Critical Amino Acids in an Immunodominant IgE Epitope of Pen c 13, a Major Allergen from Penicillium citrinum

Background: Pen c 13, identified as a 33-kDa alkaline serine protease, is a major allergen secreted by Penicillium citrinum. Detailed knowledge about the epitopes responsible for IgE binding would help inform the diagnosis/prognosis of fungal allergy and facilitate the rational design of hypoallergenic candidate vaccines. The goal of the present study was to characterize the IgE epitopes of Pen c 13. Methodology/Principal Findings: Serum samples were collected from 10 patients with mold allergy and positive Pen c 13 skin test results. IgE-binding epitopes on rPen c 13 were mapped using an enzymatic digestion and chemical cleavage method, followed by dot-blotting and mass spectrometry. A B-cell epitope-predicting server and molecular modeling were used to predict the residues most likely involved in IgE binding. Theoretically predicted IgE-binding regions were further confirmed by site-directed mutagenesis assays. At least twelve different IgE-binding epitopes located throughout Pen c 13 were identified. Of these, peptides S16 (A 148 –E 166) and S22 (A 243 –K 274) were recognized by sera from 90 % and 100 % of the patients tested, and were further confirmed by inhibition assays. Peptide S22 was selected for further analysis of IgE-binding ability. The results of serum screening showed that the majority of IgE-binding ability resided in the C-terminus. One Pen c 13 mutant, G270A (T 261 –K 274), exhibited clearly enhanced IgE reactivity, whereas another, K274A, exhibited dramatically reduced IgE reactivity

The mitochondrial ribosomal of the large subunit, afo1p, determines cellular longevity through mitochondrial back-signaling via TOR1

Abstract: Yeast mother cell‐specific aging constitutes a model of replicative aging as it occurs in stem cell populations ofhigher eukaryotes. Here, we present a new long‐lived yeast deletion mutation, afo1 (for aging factor one), that confers a60% increase in replicative lifespan. AFO1/MRPL25 codes for a protein that is contained in the large subunit of themitochondrial ribosome. Double mutant experiments indicate that the longevity‐increasing action of the afo1 mutation isindependent of mitochondrial translation, yet involves the cytoplasmic Tor1p as well as the growth‐controllingtranscription factor Sfp1p. In their final cell cycle, the long‐lived mutant cells do show the phenotypes of yeast apoptosisindicating that the longevity of the mutant is not caused by an inaility to undergo programmed cell death. Furthermore,the afo1 mutation displays high resistance against oxidants. Despite the respiratory deficiency the mutant has paradoxicalincrease in growth rate compared to generic petite mutants. A comparison of the single and double mutant strains for afo1and fob1 shows that the longevity phenotype of afo1 is independen of the formation of ERCs (ribosomal DNA minicircles).AFO1/MRPL25 function establishes a new connection between mitochondria, metabolism and aging

The mitochondrial ribosomal of the large subunit, afo1p, determines cellular longevity through mitochondrial back-signaling via TOR1

Abstract: Yeast mother cell‐specific aging constitutes a model of replicative aging as it occurs in stem cell populations ofhigher eukaryotes. Here, we present a new long‐lived yeast deletion mutation, afo1 (for aging factor one), that confers a60% increase in replicative lifespan. AFO1/MRPL25 codes for a protein that is contained in the large subunit of themitochondrial ribosome. Double mutant experiments indicate that the longevity‐increasing action of the afo1 mutation isindependent of mitochondrial translation, yet involves the cytoplasmic Tor1p as well as the growth‐controllingtranscription factor Sfp1p. In their final cell cycle, the long‐lived mutant cells do show the phenotypes of yeast apoptosisindicating that the longevity of the mutant is not caused by an inaility to undergo programmed cell death. Furthermore,the afo1 mutation displays high resistance against oxidants. Despite the respiratory deficiency the mutant has paradoxicalincrease in growth rate compared to generic petite mutants. A comparison of the single and double mutant strains for afo1and fob1 shows that the longevity phenotype of afo1 is independen of the formation of ERCs (ribosomal DNA minicircles).AFO1/MRPL25 function establishes a new connection between mitochondria, metabolism and aging

Structural aspects of fungal allergens

Despite the increasing number of solved crystal structures of allergens, the key question why some proteins are allergenic and the vast majority is not remains unanswered. The situation is not different for fungal allergens which cover a wide variety of proteins with different chemical properties and biological functions. They cover enzymes, cell wall, secreted, and intracellular proteins which, except cross-reactive allergens, does not show any evidence for structural similarities at least at the three-dimensional level. However, from a diagnostic point of view, pure allergens biotechnologically produced by recombinant technology can provide us, in contrast to fungal extracts which are hardly producible as standardized reagents, with highly pure perfectly standardized diagnostic reagents

Yno1p/Aim14p, a NADPH-oxidase ortholog, controls extramitochondrial reactive oxygen species generation, apoptosis, and actin cable formation in yeast

The large protein superfamily of NADPH oxidases (NOX enzymes) is found in members of all eukaryotic kingdoms: animals, plants, fungi, and protists. The physiological functions of these NOX enzymes range from defense to specialized oxidative biosynthesis and to signaling. In filamentous fungi, NOX enzymes are involved in signaling cell differentiation, in particular in the formation of fruiting bodies. On the basis of bioinformatics analysis, until now it was believed that the genomes of unicellular fungi like Saccharomyces cerevisiae and Schizosaccharomyces pombe do not harbor genes coding for NOX enzymes. Nevertheless, the genome of S. cerevisiae contains nine ORFs showing sequence similarity to the catalytic subunits of mammalian NOX enzymes, only some of which have been functionally assigned as ferric reductases involved in iron ion transport. Here we show that one of the nine ORFs (YGL160W, AIM14) encodes a genuine NADPH oxidase, which is located in the endoplasmic reticulum (ER) and produces superoxide in a NADPH-dependent fashion. We renamed this ORF YNO1 (yeast NADPH oxidase 1). Overexpression of YNO1 causes YCA1-dependent apoptosis, whereas deletion of the gene makes cells less sensitive to apoptotic stimuli. Several independent lines of evidence point to regulation of the actin cytoskeleton by reactive oxygen species (ROS) produced by Yno1p