BINDING OF EXTRACELLULAR-MATRIX PROTEINS TO ASPERGILLUS-FUMIGATUS CONIDIA

As detected by confocal immunofluorescence microscopy, binding of fibr onectin and laminin appeared to be associated with the protrusions pre sent on the outer cell wail layer of resting Aspergillus fumigatus con idia. Flow cytometry confirmed that binding of laminin to conidia was dose dependent and saturable. Laminin binding was virtually eliminated in trypsin-treated organisms, thus suggesting the protein nature of t he binding site, Conidia were also able to specifically adhere to lami nin immobilized on microtiter plates. Sodium dodecyl sulfate-polyacryl amide gel electrophoresis and Western blotting (immunoblotting) with l aminin and antilaminin antibody of whole conidial homogenates allowed identification, among the complex array of protein and glycoprotein sp ecies, of one polypeptide with an apparent molecular mass of 37 kDa wh ich specifically interacts with laminin, The fact that binding of coni dia to soluble or immobilized laminin or fibronectin was inhibited by fibronectin or laminin, respectively, suggests the existence of common binding sites for both ligands on the surface of conidia. Intact coni dia were also able to adhere to type I and TV collagen immobilized on microtiter plates; adhesion was found to be dose dependent and saturab le. Adhesion to immobilized type I and IV collagen was markedly inhibi ted by laminin and weakly inhibited by fibronectin. Coincubation of co nidia with Arg-Gly-Asp (RGD) peptides caused a dose-dependent decrease in binding of cells to immobilized or soluble fibronectin, yet intera ction of cells with soluble or immobilized laminin and type I and IV c ollagen remained unaffected, Interactions described here could be impo rtant in mediating attachment of the fungus to host tissues, thus play ing a role in the establishment of the disease.