The sensing of acid pH by the dermatophyte Trichophyton rubrum correlates with its infecting capacity

SILVEIRA HC; GRAS DE; FERREIRA-NOZAWA MS; ONO CJ; ROSSI A; MARTINEZ-ROSSI NM

Águas de Lindóia

Encuentro; XXXV Reunião Anual da Sociedade Brasileira de Bioquímica e Biologia Molecular; 2006

Dermatophytosis is commonly caused by fungi that parasite human skin and nails. Although several factors contribute to their pathogenicity, the successful initiation of infection depends on the capacity of the infecting dermatophyte to sense and overcome the acid pH of the skin. Thus, it is important to understand the metabolic responses that govern the pH signaling in dermatophytes. The functionality of gene pacC, which encodes a protein that is homologous to the PacC/Rim101p family of pH signaling transcription regulators, was examined in T. rubrum for the ability of the wild type H6 and pacC-1 mutant strains to grow on human nails in vitro. The disruption of gene pacC was checked by Southern analysis for the predicted disruption restriction fragments and by Western blot analysis after incubation of both the H6 and pacC-1 strains at pH 5.0, where proteolyses of the PacC protein at pH 5.0 was shown. Moreover, disruption of gene pacC was correlated with a decreased ability of the pacC-1 mutant strain to grow on human nail fragments as the only source of nutrition, which is consistent with the fact that keratinolytic proteases are under the regulation of gene pacC. Thus, in order to identify genes supposedly expressed in the initial steps of infection, we submitted the strain H6 of the dermatophyte T. rubrum to acid pH and isolated the transcripts up regulated in this experimental condition by employing the suppression subtractive hybridization (SSH) approach. Out of a total of 300 cDNA clones analyzed by dot-blot macro-arrays, 96 clones were confirmed as differentially expressed at pH 5.0, which represented 21 different genes after Phred/Phrap analysis. Based on BLAST homology, the hypothetical proteins represent 57% of the total, and putative proteins identified are involved in the metabolism, cell differentiation, cell cycle and drug resistance mechanisms. These studies suggested that the infecting capacity of T. rubrum depends on the action of protein PacC, which is presumed to regulate a large metabolic machinery essential for initiating the infection process.