Identification and Characterization of Cryptosporidium parvum Clec, a Novel C-Type Lectin Domain-Containing Mucin-Like Glycoprotein

Abstract

dCryptosporidium species are waterborne apicomplexan parasites that cause diarrheal disease worldwide. Although the mechanisms underlying Cryptosporidium-host cell interactions are not well understood, mucin-like glycoproteins of the parasite are known to mediate attachment and invasion in vitro. We identified C. parvum Clec (CpClec), a novel mucin-like glycoprotein that contains a C-type lectin domain (CTLD) and has orthologs in C. hominis and C. muris. CTLD-containing proteins are ligand-binding proteins that function in adhesion and signaling and are present in a wide range of organisms, from humans to viruses. However, this is the first report of a CTLD-containing protein in protozoa and in Apicomplexa. CpClec is predicted to be a type 1 membrane protein, with a CTLD, an O-glycosylated mucin-like domain, a transmembrane domain, and a cytoplasmic tail containing a YXX sorting motif. The predicted structure of CpClec displays several characteristics of canonical CTLD-containing proteins, including a long loop region hydrophobic core associated with calcium-dependent glycan binding as well as predicted calcium-and glycan-binding sites. CpClec expression during C. parvum infection in vitro is maximal at 48 h postinfection, suggesting that it is developmentally regulated. The 120-kDa mass of native CpClec is greater than predicted, most likely due to O-glycosylation. CpClec is localized to the surface of the apical region and to dense granules of sporozoites and merozoites. Taken together, these findings, along with the known functions of C. parvum mucin-like glycoproteins and of CTLD-containing proteins, strongly implicate a significant role for CpClec in Cryptosporidium-host cell interactions.

Diversity of extracellular proteins during the transition from the ‘proto-apicomplexan’ alveolates to the apicomplexan obligate parasites

“…Alveolates possess a great range of possible carbohydrate-binding domains that appear to either be specific to classes within alveolates, or have broader distribution within prokaryotes and eukaryotes. Some domains are well-described, such as the conserved domains lectin, ricin and chitin binding (see Table 1); whereas many lectin proteins were identified based upon experimental affinity for carbohydrates as, for example, in Cryptosporidium (Bhat et al 2007;Bhalchandra et al 2013). Examples of carbohydrate-binding receptors include recognition of erythrocyte surface sialic acid by the Plasmodium merozoite protein EBA-175 during invasion (reviewed in Gaur and Chitnis, 2011); recognition of sialic acid via an unrelated saccharide-binding module, as well as a gal-lectin domain, within MIC1 participating in host cell invasion by Toxoplasma (TGME49_291890 in Fig.…”

Genetic characterization of Cryptosporidium in animal and human isolates from Jordan

“…All samples were screened using an 18S qPCR as previously described (Yang et al, 2014) and a C. parvum and C. hominis specific qPCR at a unique Cryptosporidium specific gene (Clec) coding for a novel mucin-like glycoprotein that contains a Ctype lectin domain (CTLD) previously described (Morgan et al, 1996;Bhalchandra et al, 2013;Yang et al, 2009;. This was done to determine if there were any mixed infections with C. parvum and/or C. hominis in the samples.…”

Genetic diversity of Cryptosporidium in fish at the 18S and actin loci and high levels of mixed infections

“…Isolates positive at the 18S locus were also analyzed at the actin locus using PCR primers optimized for amplification of piscinederived Cryptosporidium species (which produce a 392 bp product), as previously described (Koinari et al, 2013). All positives were also screened using a C. parvum and C. hominis specific qPCR at a unique Cryptosporidium specific gene (Clec) coding for a novel mucin-like glycoprotein that contains a C-type lectin domain (CTLD) previously described (Morgan et al, 1996;Bhalchandra et al, 2013;Yang et al, 2009Yang et al, , 2013. This was done to determine if there were any mixed infections with C. parvum and/or C. hominis in the fish.…”