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Expression and secretion of Aspergillus fumigatus proteases are regulated in response to different protein substrates
Edward Farnell1, Karine Rousseau, David J Thornton
1Respiratory Research Group, School of Translational Medicine, University of Manchester, Manchester M13 9PT, UK. edward.farnell@postgrad.manchester.ac.uk
Abstract:
The ubiquitous filamentous fungus Aspergillus fumigatus secretes a number of allergens with protease activity and has been linked to a variety of allergic conditions such as Severe Asthma with Fungal Sensitization (SAFS) and Allergic Bronchopulmonary Aspergillosis (ABPA). However, it is unclear which allergen proteases are being secreted during fungal invasion and whether the local biological environment regulates their expression. Understanding the dynamic expression of allergen proteases during growth of A. fumigatus may lead to further characterisation of the pathogenesis of these disorders as well as improved standardisation in the commercial production of these allergens. Secretion of proteases during germination and early growth of A. fumigatus was investigated in response to various complex protein sources (pig lung homogenate, mucin or casein). Protease inhibitor studies demonstrated that A. fumigatus (AF293 strain) secretes predominately serine proteases during growth in pig lung based medium and mainly metalloproteases during growth in casein based medium but suppressed protease secretion in unmodified Vogel's minimal medium and secreted both types in mucin based medium. Analysis of gene transcription and protein identification by mass spectrometry showed that the matrix metalloprotease, Mep/Asp f 5 and the serine protease, Alp1/Asp f 13, were upregulated and secreted during growth in pig lung medium, whereas Alp1 was predominately expressed and secreted in mucin based medium. In casein medium, the matrix metalloprotease, Lap1, was also upregulated and secreted in addition to Mep and Alp1. These findings suggest that A. fumigatus is able to detect different complex proteins available as substrates in its environment and regulate protease secretion accordingly. There is a requirement for the standardisation of A. fumigatus allergen extracts used both in clinical diagnosis of A. fumigatus allergy and in research studies.
Insights
Aspergillus fumigatus secretes different proteases based on its environment, impacting fungal allergies. Understanding this protease regulation is key for diagnosing and treating conditions like SAFS and ABPA.
Area of Science:
- Medical Mycology
- Molecular Biology
- Allergology
Background:
- * Aspergillus fumigatus is a fungus that causes allergic diseases like Severe Asthma with Fungal Sensitization (SAFS) and Allergic Bronchopulmonary Aspergillosis (ABPA).
- * The specific allergen proteases secreted by A. fumigatus during infection and how the environment influences them remain unclear.
- * Understanding protease secretion is crucial for characterizing disease mechanisms and standardizing allergen production for diagnostics.
Purpose of the Study:
- * To investigate the types and regulation of proteases secreted by A. fumigatus during germination and early growth.
- * To determine how different environmental protein sources influence protease secretion and gene expression.
- * To identify specific allergen proteases involved in A. fumigatus-related allergic responses.
Main Methods:
- * Culturing A. fumigatus (AF293 strain) in media with various protein sources (pig lung, mucin, casein).
- * Employing protease inhibitor studies to identify protease classes (serine, metalloproteases).
- * Analyzing gene transcription and using mass spectrometry for protein identification.
Main Results:
- * A. fumigatus secreted serine proteases in pig lung medium and metalloproteases in casein medium.
- * Protease secretion was suppressed in minimal medium but included both types in mucin medium.
- * Matrix metalloprotease Mep/Asp f 5 and serine protease Alp1/Asp f 13 were upregulated in pig lung medium.
- * Alp1 was predominant in mucin medium, while Mep and Alp1 were secreted in casein medium.
Conclusions:
- * A. fumigatus dynamically regulates protease secretion in response to available protein substrates in its environment.
- * Identified key proteases (Mep/Asp f 5, Alp1/Asp f 13, Lap1) secreted under different conditions.
- * Highlights the need for standardized A. fumigatus allergen extracts for clinical diagnosis and research.
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