Dermatophytes are highly specialized filamentous fungi which cause the majority of superficial mycoses in humans and animals. The high secreted proteolytic activity of these microorganisms during growth on proteins is assumed to be linked to their particular ability to exclusively infect keratinized host structures such as the skin stratum corneum, hair, and nails. Individual secreted dermatophyte proteases were recently described and linked with the in vitro digestion of keratin. However, the overall adaptation and transcriptional response of dermatophytes during protein degradation are largely unknown. To address this question, we constructed a cDNA microarray for the human pathogenic dermatophyte Trichophyton rubrum that was based on transcripts of the fungus grown on proteins. Profiles of gene expression during the growth of T. rubrum on soy and keratin protein displayed the activation of a large set of genes that encode secreted endo-and exoproteases. In addition, other specifically induced factors potentially implicated in protein utilization were identified, including heat shock proteins, transporters, metabolic enzymes, transcription factors, and hypothetical proteins with unknown functions. Of particular interest is the strong upregulation of key enzymes of the glyoxylate cycle in T. rubrum during growth on soy and keratin, namely, isocitrate lyase and malate synthase. This broad-scale transcriptional analysis of dermatophytes during growth on proteins reveals new putative pathogenicityrelated host adaptation mechanisms of these human pathogenic fungi.Dermatophytes are highly specialized fungi which are the most common agents of superficial mycoses in humans and animals (13, 34). Among the human pathogenic dermatophytes, the anthropophilic species Trichophyton rubrum is clinically the most commonly observed. In contrast to most other medically important fungi, dermatophytes are not opportunists but are obligate pathogens, infecting exclusively the skin stratum corneum, nails, or hair. The ability of dermatophytes to degrade and utilize compact hard keratin within such host structures is presumably related to their common secreted keratinolytic activity, which is therefore a major putative virulence attribute of these fungi. Individual endo-and exoproteases secreted by dermatophytes are similar to those of species of the genus Aspergillus. However, in contrast to those of Aspergillus spp., dermatophyte-secreted endoproteases are multiple and members of two large protein families, the subtilisins (Subs) S8 (serine proteases) and the fungalysins M36 (metalloproteases) (see the MEROPS peptidase database, http://merops.sanger.ac.uk) (10, 11). More than 20 genes that encode secreted proteases have been identified in dermatophytes, some of which have been characterized in detail on the molecular level (reviewed in reference 23).In order to better understand the basic mechanisms of protein degradation by dermatophytes, the secretome of different dermatophyte species was previously analyzed during in vitro growt...

Dermatophytes are the most common infectious agents responsible for superficial mycosis in humans and animals. Various species in this group of fungi show overlapping characteristics. We investigated the possibility that closely related dermatophyte species with different behaviours secrete distinct proteins when grown in the same culture medium. Protein patterns from culture filtrates of several strains of the same species were very similar. In contrast, secreted protein profiles from various species were different, and so a specific signature could be associated with each of the six analysed species. In particular, protein patterns were useful to distinguish Trichophyton tonsurans from Trichophyton equinum, which cannot be differentiated by ribosomal DNA sequencing. The secreted proteases Sub2, Sub6 and Sub7 of the subtilisin family, as well as Mep3 and Mep4 of the fungalisin family were identified. SUB6, SUB7, MEP3 and MEP4 genes were cloned and sequenced. Although the protein sequence of each protease was highly conserved across species, their level of secretion by the various species was not equivalent. These results suggest that a switch of habitat could be related to a differential expression of genes encoding homologous secreted proteins.

Dermatophytes cause most superficial mycoses in humans and animals. Their pathogenicity is probably linked with the secretion of proteins degrading keratinised structures. Using 2D-PAGE and a shotgun mass spectrometry approach, we identified 80 proteins from Trichophyton rubrum and Trichophyton violaceum secretomes, under conditions mimicking those in the host. Identified proteins included endo- and exoproteases, other hydrolases, and oxidoreductases. Our findings can contribute to a better understanding of the virulence mechanisms of the two species and the different types of infection they cause.