Preliminary Functional Characterization Of Malectin In Cryptosporidium Parvum

Cryptosporidium parvum is an important water-borne and food-borne zoonotic parasite.Cryptosporidial infection can cause abdominal pain,diarrhea and other symptoms in humans and animals.In developing countries,C.parvum and C.hominis are one of the top pathogens causing moderate to severe diarrhea in infants and toddlers.Glycosylation is one of the ubiquitous protein modifications in organisms,including Cryptosporidium and other apicomplexans.About 50% of proteins may be glycosylated.In Cryptosporidium,both N-and O-linked glycosylations are much simplified and differ from mammals.This study focused on a carbohydrate-binding protein,namely malectin,that was present only in the Cryptosporidium lineage,but absent in all other apicomplexans.In C.parvum,malectin(Cp Mal)was encoded at the locus cgd6＿110.Malectin is a carbohydrate-binding protein that binds Glc(2)N-glycan and is present in animals and some alveolates.This study aimed to characterize the general molecular and biochemical features of Cryptosporidium parvum malectin(Cp Mal).Polyclonal antibodies were raised for detecting native Cp Mal by western blotting and immunofluorescence assays.Recombinant Cp Mal and human malectin(Hs Mal)were produced,and their binding activities to amylose and the host cell surface were compared.Far-western blotting and far-immunofluorescence assays were used to detect potential binding partners of Cp Mal in the parasite.We found that native Cp Mal appeared to exist in dimeric form in the parasite and was distributed in a diffuse pattern over sporozoites but was highly concentrated on the anterior and posterior sides near the nuclei.Cp Mal,compared with Hs Mal,had significantly lower affinity for binding amylose but substantially higher activity for binding host cells.Recombinant Cp Mal recognized three high molecular weight protein bands and labeled the sporozoite posterior end corresponding to the crystalloid body,thus suggesting the presence of its potential ligands in the parasite.Conclusion.Cp Mal notably differs from Hs Mal in molecular and biochemical properties;thus,further investigation of its biochemical and biological roles is warranted.