Identification of a family of four UDP-polypeptide N-acetylgalactosaminyl transferases in Cryptosporidium species

• There are 4 ppGalNAc-Ts each in the genomes of C. parvum, C. hominis and C. muris.
• All four contain a catalytic domain and a ricin B lectin domain.
• All four ppGalNAc-Ts are differentially expressed during C. parvum infection in vitro.
• C. parvum lysates display ppGalNAc-T activity in vitro.

Although mucin-type O-glycans are critical for Cryptosporidium infection, the enzymes catalyzing their synthesis have not been studied. Here, we report four UDP N-acetyl-α-d-galactosamine:polypeptide N-acetylgalactosaminyl transferases (ppGalNAc-Ts) from the genomes of C. parvum, C. hominis and C. muris. All are Type II membrane proteins which include a cytoplasmic tail, a transmembrane domain, a stem region, a glycosyltransferase family 2 domain and a C-terminal ricin B lectin domain. All are expressed during C. parvum infection in vitro, with Cp-ppGalNAc-T1 and -T4 expressed at 24 h and Cp-ppGalNAc-T2 and -T3 at 48 and 72 h post-infection, suggesting that their expression may be developmentally regulated. C. parvum sporozoite lysates display ppGalNAc-T enzymatic activity against non-glycosylated and pre-glycosylated peptides suggesting that they contain enzymes capable of glycosylating both types of substrates. The importance of mucin-type O-glycans in Cryptosporidium–host cell interactions raises the possibility that Cp-ppGalNAc-Ts may serve as targets for intervention in cryptosporidiosis.

Domain structure of Cryptosporidium UDP-polypeptide N-acetyl galactosaminyl transferases, a family of four enzymes that catalyze the synthesis of O-glycans on mucin-like glycoproteins which mediate attachment and invasion.Figure optionsDownload high-quality image (150 K)Download as PowerPoint slide