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PROTEOMIC ANALYSIS OF THE SECRETIONS OF PSEUDALLESCHERIA BOYDII, A HUMAN FUNGAL PATHOGEN WITH UNKNOWN GENOME
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Abstract
Pseudallescheria boydii is a filamentous fungus that causes a wide array
of infections that can affect practically all the organs of the human body. The
treatment of pseudallescheriosis is difficult since P. boydii exhibits intrinsic resistance
to the majority of antifungal drugs used in the clinic and the virulence attributes
expressed by this fungus are unknown. The study of the secretion of molecules is an
important approach for understanding the pathogenicity of fungi. With this task in
mind, we have shown that mycelial cells of P. boydii were able to actively secrete
proteins into the extracellular environment; some of them were recognized by
antibodies present in the serum of a patient with pseudallescheriosis. Additionally,
molecules secreted by P. boydii induced in vitro irreversible damage in pulmonary
epithelial cells. Subsequently, two-dimensional gel electrophoresis combined with
mass spectrometry was carried out in order to start the construction of a map of
secreted proteins from P. boydii mycelial cells. The two-dimensional map showed that
most of the proteins (around 100 spots) were focused at pH ranging from 4 to 7 withmolecular masses ranging from 14 to >117 kDa.
Fifty spots were randomly selected, of which 30 (60%) were consistently identified, while 20 (40%) spots generated peptides that
showed no resemblance to any known protein from other fungi and/or MS with low quality. Notably, we identified proteins
involved in metabolic pathways (energy/carbohydrate, nucleotide, and fatty acid), cell wall remodeling, RNA processing, signaling,
protein degradation/nutrition, translation machinery, drug elimination and/or detoxification, protection against environmental
stress, cytoskeleton/movement proteins, and immunogenic molecules. Since the genome of this fungus is not sequenced, we
performed enzymatic and immunodetection assays in order to corroborate the presence of some released proteins. The
identification of proteins actively secreted by P. boydii provides important new information for understanding immune modulation
and provides important new perspectives on the biology of this intriguing fungus.
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