Okumura, C. Y., Baum, L. G. & Johnson, P. J. Galectin-1 on cervical epithelial cells is a receptor for the sexually transmitted human parasite Trichomonas vaginalis. Cell. Microbiol. 1, 2078-2090

Department of Microbiology, Immunology, and Molecular Genetics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA.
Cellular Microbiology (Impact Factor: 4.92). 10/2008; 10(10):2078-90. DOI: 10.1111/j.1462-5822.2008.01190.x
Source: PubMed


The extracellular protozoan parasite Trichomonas vaginalis causes the most prevalent non-viral sexually transmitted human infection, yet the pathogenesis of infection is poorly understood, and host cell receptors have not been described. The surface of T. vaginalis is covered with a glycoconjugate called lipophosphoglycan (LPG), which plays a role in the adherence and cytotoxicity of parasites to human cells. T. vaginalis LPG contains high amounts of galactose, making this polysaccharide a candidate for recognition by the galactose-binding galectin family of lectins. Here we show that galectin-1 (gal-1) is expressed by human cervical epithelial cells and binds T. vaginalis LPG. Gal-1 binds to parasites in a carbohydrate-dependent manner that is inhibited in the presence of T. vaginalis LPG. Addition of purified gal-1 to cervical epithelial cells also enhances parasite binding, while a decrease in gal-1 expression by small interfering RNA (siRNA) transfection decreases parasite binding. In contrast, the related galectin-7 (gal-7) does not bind T. vaginalis in a carbohydrate-dependent manner, and is unable to mediate attachment of parasites to host cells. Our data are consistent with the presence of multiple host cell receptors for T. vaginalis of which gal-1 is the first to be identified and highlight the importance of glycoconjugates in host-pathogen interactions.

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Available from: Cheryl Y M Okumura, Jan 05, 2015
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    • "Glycans on the viral surface can be recognized by host lectins that function as pattern recognition receptors (PRRs) that signal to activate and regulate the appropriate innate and adaptive immune responses (Barrionuevo et al. 2007; Jeon et al. 2010). However, multiple examples reveal that co-evolution of host-pathogen consortia has led to subversion of the immune recognition roles of lectins to facilitate adhesion and entry of the pathogens into the host cells (Kamhawi et al. 2004; Ouellet et al. 2005; Okumura et al. 2008; Yang et al. 2011). Galectins are good examples of these opposing recognition functions of lectins that may be either beneficial for the host in their roles as "
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    • "Interestingly, we found that most of the TvTSPs analysed were up-regulated upon contact with VECs, suggesting a role for these proteins in host : parasite interaction. Since in vitro attachment of the parasites is mostly completed within ∼ 20 min of exposure to the VECs (Okumura et al., 2008), the pattern of up-regulation suggests TvTSPs plays a role in events occurring downstream of adherence. It is important to note that while most of the TvTSP genes we found were up regulated upon exposure of B7RC2 strain to host cells, these genes were not reported in the up regulated group in the Gould et al. analysis (Gould et al., 2013). "
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    • "The multivalency of galectins resulting from their oligomerization is not only key to their cooperative binding to complex carbohydrate ligands and their ability to crosslink surface glycans and form lattices (Vasta et al., 2004; Rabinovich et al., 2007), but would also enable galectins to facilitate the attachment of pathogens to the cell surface (Ahmad et al., 2004; Nieminen et al., 2007; Vasta, 2009). This subversion of galectins functions as PRRs has already been reported for the galectin-mediated attachment of viruses (Ouellet et al., 2005; Garner et al., 2010; St-Pierre et al., 2011; Yang et al., 2011), bacteria (Okumura et al., 2008), and eukaryotic parasites (Kamhawi et al., 2004). Prior studies have provided evidence that the release of sialic acid by the activity of the IAV neuraminidase promotes the adhesion of S. pneumoniae to airway epithelial cells in the form of a biofilm, that makes the pathogen less accessible to host factors and antibiotics and facilitates host invasion (Trappetti et al., 2009). "
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