Recognition of Fibronectin by Penicillium marneffei Conidia via a Sialic Acid-Dependent Process and Its Relationship to the Interaction Between Conidia and Laminin

Abstract

Adhesion of Penicillium marneffei conidia to the extracellular matrix protein laminin via a sialic acid-dependent process has previously been demonstrated. This study describes the interaction of P. marneffei conidia with fibronectin and examines the relationship of this process to the recognition of laminin via conidia. Immunofluorescence microscopy demonstrated that fibronectin bound to the surface of conidia and to phialides, but not to hyphae, in a pattern similar to that reported for laminin. Conidia were able to bind to fibronectin immobilized on microtiter plates in a concentration-dependent manner. However, binding to fibronectin (at any given concentration of protein and conidia) was less than that to laminin under equivalent conditions. Soluble fibronectin and antifibronectin antibody inhibited adherence of conidia to fibronectin in the plate adherence assay; soluble laminin also caused pronounced inhibition. Various monosaccharides and several peptides had no effect on adherence to fibronectin. However, N-acetylneuraminic acid abolished adherence to fibronectin, indicating that the interaction was mediated through a sialic acid-dependent process; the latter parallels observations of laminin binding by conidia. Fibronectin binding (and binding of laminin) was considerably reduced by prolonged preincubation of conidia with chymotrypsin, suggesting the protein nature of the binding site. Conidia from older cultures were more adherent to both immobilized fibronectin and laminin than conidia from younger cultures. Ligand affinity binding demonstrated the presence of a 20-kDa protein with the ability to bind both fibronectin and laminin. There would therefore appear to be a common receptor for the binding of fibronectin and laminin on the surface of P. marneffei, and the interaction described here maybe important in mediating attachment of the fungus to host tissue.

Binding of extracellular matrix proteins to Paracoccidioides brasiliensis

“…Adhesion of microorganisms to host cells and tissues represents a critical step in the process of infection [13,15,16]. We previously demonstrated that P. brasiliensis was capable of adhering to and invading epithelial cells.…”

“…Immunofluorescence microscopy was performed as previously described and adapted [16], using suspensions of yeast forms of P. brasiliensis (10 7 cells/ml). Briefly, yeasts were resuspended in phosphate-buffered saline (PBS) 10 mM, pH 7.4, containing the ECM components at a concentration of 500 mg/ml (fibronectin, laminin, types I and IV collagen) or bovine serum albumin (BSA) and incubated for 3 h at 37 C. The suspensions were washed and resuspended with specific ECM antibodies (Sigma) diluted 1:10 in PBS, and finally incubated for 1 h at 37 C. Suspensions were then washed and resuspended in goat anti-rabbit (1:20 dilution, Sigma) for laminin and fibronectin, and goat anti-mouse IgG FITC conjugate in PBS for types I and IV collagen, for 1 h at 37 C. Finally, the suspensions were washed again and examined.…”

Involvement of extracellular matrix proteins in the course of experimental paracoccidioidomycosis

“…The interaction of ECMp with various infectious agents has been reported, where these ECMp could serve as adherence substrates (Silva-Filho et al, 1988;Furtado et al, 1992;Li et al, 1995;Gaur et al, 1999;Wasylnka & Moore, 2000). Of particular interest in this context is the identification of ECM-binding proteins on the surface of several fungi of clinical importance such as Candida albicans (López-Ribot et al, 1996;Gaur et al, 1999), Aspergillus fumigatus (Coulot et al, 1994;Gil et al, 1996;Wasylnka & Moore, 2000), Histoplasma capsulatum (McMahon et al, 1995), Cryptococcus neoformans (Rodrigues et al, 2003), Pneumocystis carinii (Narasimhan et al, 1994), Sporothrix schenckii (Lima et al, 2001) and Penicillium marneffei (Hamilton et al, 1998(Hamilton et al, , 1999.…”

Sixty Years from Segretain’s Description: What Have We Learned and Should Learn About the Basic Mycology of Talaromyces marneffei?

“…Although the infection route for talaromycosis is still unclear as discussed above, it is generally believed that patients acquire pathogenic conidia through inhalation. After entering the host's airway, conidia bind to the extracellular matrices [107][108][109][110], which is mediated by glyceraldehyde-3-phosphate dehydrogenase (GAPDH) [110], and adhere to the host bronchoalveolar epithelium. There, the fungus interacts with epithelial cells [111,112] and is phagocytosed by pulmonary macrophages.…”