Trace-elements driven up-regulation of secreted proteases expression in the human-pathogenic fungus Trichophyton rubrum.

Background: Trichophyton rubrum is a widespread human pathogenic fungus, colonizing keratinized tissue of outer body-parts. Thereby, the pathogen is relying on nutrients available from the host. The invasive mechanism of the pathogen is relaying on secreted proteases, which hydrolyze skin-proteins for subsequent up-take.

Methods: In this study, we analyzed the gene expression of secreted proteases by RNAseq. In the results, we show the expression profile of 31 secreted protease genes under three conditions: keratin medium and keratin medium with trace-elements or with glucose.

Results: By adding trace-elements to keratin medium, the expression of secreted proteases increased from 1.8 % to 3.3 %. Across all groups of secreted proteases, higher expression was observed. The genes SUB4, MEP1, MEP3, MEP5, MEP9, LAP1, LAP2 and MCPA were significantly stronger expressed, whereby MEP5 (∼6 fold) and SUB4 (∼5.8 fold) were strongest up-regulated.

Discussion: We discuss the influence and significance of trace-elements on secreted proteases. Further, we speculate about the disturbed nutritional immunity in psoriatic and atopic skin as factor for increased risk of getting severe T. rubrum infections.