Interaction of murine macrophage-membrane proteins with components of the pathogenic fungusHistoplasma capsulatum

Abstract

The interaction of macrophage-membrane proteins and histoplasmin, a crude antigen of the pathogenic fungus Histoplasma capsulatum, was studied using murine peritoneal macrophages. Membrane proteins were purified via membrane attachment to polycationic beads and solubilized in Tris-HCl/SDS/DTT/glycerol for protein extraction; afterwards they were adsorbed or not with H. capsulatum yeast or lectin binding-enriched by affinity chromatography. Membrane proteins and histoplasmin interactions were detected by ELISA and immunoblotting assays using anti-H. capsulatum human or mouse serum and biotinylated goat anti-human or anti-mouse IgG/streptavidin-peroxidase system to reveal the interaction. Results indicate that macrophage-membrane proteins and histoplasmin components interact in a dose-dependent reaction, and adsorption of macrophage-membrane proteins by yeast cells induces a critical decrease in the interaction. Macrophage-membrane glycoproteins with terminal D-galactosyl residues, purified by chromatography with Abrus precatorius lectin, bound to histoplasmin; and two bands of 68kD and 180kD of transferred membrane protein samples interacted with histoplasmin components, as revealed by immunoblot assays. Specificity for beta-galactoside residues on the macrophage-membrane was confirmed by galactose inhibition of the interaction between macrophage-membrane proteins and histoplasmin components, in competitive ELISA using sugars, as well as by enzymatic cleavage of the galactoside residues.

Surface architecture of Histoplasma capsulatum

“…The expression of lectins by pathogenic microorganisms has been correlated to the organism attachment and invasion to host tissues (Mendes-Giannini et al, 2000 ; Singh et al, 2011 ). Interestingly, Hc has components with lectin activity on the yeast surface that can bind to surface molecules on murine macrophages (Taylor et al, 1998 ; Duarte-Escalante et al, 2003 ). It has been shown that a lectin-like molecule plays a role in the binding to macrophage surface proteins suggesting that the specific receptor for histoplasmin components on macrophage could be an oligosaccharide–protein complex containing galactose (mainly β-anomer) as determinant, since enzymatic cleavage of galactosyl residues or a galactose N -acetyl- d -galactosamine compound reduced this interaction (Maldonado et al, 1994 , 1998 ; Taylor et al, 1998 ).…”

Sialic acid-specific lectins: occurrence, specificity and function

“…Early studies showed that a 50-kDa cell wall protein from H. capsulatum yeast was able to bind laminin with high affinity, a process thought to be important in the initial stages of infection [100]. Later, a specific lectin-like interaction between H. capsulatum yeast and macrophage-membrane proteins was identified [101]. This lectin-like binding was initially thought to be specific for b-Gal residues; however, more recent studies have shown binding to human erythrocytes may be mediated through Sia [102].…”

Adhesion ofHistoplasma capsulatumto pneumocytes and biofilm formation on an abiotic surface

“…A lectinmediated interaction between H. capsulatum yeast and host cells has been considered, in which lectin activity is associated with a component present on the yeast cell surface. This lectin-like activity is specific to galactosylated surface molecules (mainly b-anomer) on murine macrophages (Taylor et al 1998;MendesGiannini et al 2000;Duarte-Escalante et al 2003). H. capsulatum yeast also has the ability to bind and agglutinate human erythrocytes through this lectin-like component (Taylor et al 2004).…”