The apicomplexan parasiteCryptosporidiumcauses significant diarrheal disease worldwide. Effective anticryptosporidial agents are lacking, in part because the molecular mechanisms underlyingCryptosporidium-host cell interactions are poorly understood. Previously, we identified and characterized a novelCryptosporidium parvumC-type lectin domain-containing mucin-like glycoprotein, CpClec. In this study, we evaluated the mechanisms underlying interactions of CpClec with intestinal epithelial cells by using an Fc-tagged recombinant protein. CpClec-Fc displayed Ca2+-dependent, saturable binding to HCT-8 and Caco-2 cells and competitively inhibitedC. parvumattachment to and infection of HCT-8 cells. Binding of CpClec-Fc was specifically inhibited by sulfated glycosaminoglycans, particularly heparin and heparan sulfate. Binding was reduced after the removal of heparan sulfate and following the inhibition of glycosaminoglycan synthesis or sulfation in HCT-8 cells. Like CpClec-Fc binding,C. parvumattachment to and infection of HCT-8 cells were inhibited by glycosaminoglycans and were reduced after heparan sulfate removal or inhibition of glycosaminoglycan synthesis or sulfation. Lastly, CpClec-Fc binding andC. parvumsporozoite attachment were significantly decreased in CHO cell mutants defective in glycosaminoglycan synthesis. Together, these results indicate that CpClec is a novel C-type lectin that mediatesC. parvumattachment and infection via Ca2+-dependent binding to sulfated proteoglycans on intestinal epithelial cells.
Sulfation of heparan sulfate in isolated rat intestinal epithelial cells