Secreted Metalloprotease Gene Family of Microsporum canis

Abstract

Keratinolytic proteases secreted by dermatophytes are likely to be virulence-related factors. Microsporum canis, the main agent of dermatophytosis in dogs and cats, causes a zoonosis that is frequently reported. Using Aspergillus fumigatus metalloprotease genomic sequence (MEP) as a probe, three genes (MEP1, MEP2, and MEP3) were isolated from an M. canis genomic library. They presented a quite-high percentage of identity with both A. fumigatus MEP and Aspergillus oryzae neutral protease I genes. At the amino acid level, they all contained an HEXXH consensus sequence, confirming that these M. canis genes (MEP genes) encode a zinc-containing metalloprotease gene family. Furthermore, MEP3 was found to be the gene encoding a previously isolated M. canis 43.5-kDa keratinolytic metalloprotease, and was successfully expressed as an active recombinant enzyme in Pichia pastoris. Reverse transcriptase nested PCR performed on total RNA extracted from the hair of M. canis-infected guinea pigs showed that at least MEP2 and MEP3 are produced during the infection process. This is the first report describing the isolation of a gene family encoding potential virulencerelated factors in dermatophytes.Dermatophytes are fungi that have the ability to invade keratinized structures, such as the superficial cornified skin layers, hair, and nails, causing a superficial cutaneous infection called dermatophytosis (48). Microsporum canis is the main agent of dermatophytosis in dogs and cats (41) and causes a zoonosis that has increased in several European countries (23). Furthermore, this zoophilic dermatophyte is the most frequently isolated agent in human tinea capitis in Belgium (20) and in Italy (38). The cat, considered as the natural host and the main reservoir of M. canis, is the principal source of human contamination (41). In addition, the existence of feline asymptomatic infection and the lack of efficient immunoprophylaxis are responsible for the high frequency of endemic M. canis dermatophytosis in catteries (41). In this context, studies on vaccination prophylaxis are recommended by the World Health Organization and the International Society of Human and Animal Mycology (50).Pathophysiological mechanisms of dermatophytosis, including M. canis infection, are poorly understood. Among potential fungal virulence factors, attention has been paid to proteases for their potential role in the nutrition of the fungi (2), in tissue invasion (1), and in the control of host defense mechanisms (8, 13). Given the ability of dermatophytes to invade and to be essentially confined to keratinized structures, it can be assumed that keratinolytic proteases (keratinases) might be significant virulence factors. Therefore, the characterization of keratinases seems to be a major step for a better understanding of dermatophytic infection pathogenesis and subsequently of the host-fungus relationship. Some keratinases have been isolated from Trichophyton rubrum (1,3,19,25), Trichophyton mentagrophytes (46, 51, 52), and M. canis (5,22,29,42,43).Recent...

Dermatófitos: interação patógeno-hospedeiro e resistência a antifúngicos

“…For this reason, the secretion of a great variety of enzymes by dermatophytes, such as proteases, lipases, elastases, collagenases, phosphatases and esterases, is one of the most important factors during the infectious process. 15,19,20 This enzymatic machinery is one of the best-characterized virulence factors of dermatophytes, allowing the hydrolisis of structural components of the epidermal tissue and the invasive character of these pathogens. Among the wide variety of enzymes secreted by dermatophytes, proteolytic enzymes are the most studied, and the importance of keratinolytic proteases to the pathogenicity is well established.…”

Plant and fungal gene expression in mycorrhizal protocorms of the orchidSerapias vomeraceacolonized byTulasnella calospora

“…M36 metallopeptidases (also known as fungalysins) are known to promote fungal pathogenicity both in animals and in plants. 19,20,21,22 We identified all members of this protein family in the T. calospora genome and assessed their expression in S. vomeracea mycorrhizal protocorms. Ten genes coding for putative fungalysins (Table 1) were found, that clustered in different phylogenetic groups inside this family (Fig.…”

“…Aspergillus fumigatus, Coccidioides immitis, Cryptococcus neoformans, Microsporum canis, dermatophytic fungi), where they help fungi during host tissue invasion either because they degrade structural components of the host extracellular matrix, 19,20 or because they degrade immunodominant cell surface antigens, thus escaping host recognition. 23 This gene family has expanded in the Onygenales, that includes several animal pathogens, 24 with a rapid functional divergence of the duplicated proteins.…”

Identification of a Chitinase-modifying Protein from Fusarium verticillioides

“…The purified protein was then shown to degrade the structural protein elastin, which is a component of human lungs, suggesting that fungalysins promote pathogenicity by degrading extracellular matrix proteins. This model was strengthened by the observation that a fungalysin from Microsporum canis, which causes skin diseases in cats and dogs, is able to degrade the structural protein keratin (4). Besides these examples, few protein-based studies of fungalysin proteins or their substrates have been reported.…”