Cryptosporidium parvum cyclic GMP-dependent protein kinase (PKG): An essential mediator of merozoite egress

Cryptosporidiosis is an obligate intracellular pathogen causing diarrhea. Merozoite egress is essential for infection to spread between host cells. However, the mechanisms of egress have yet to be defined. We hypothesized that Cyclic GMP-Dependent Protein Kinase G (PKG) may be involved in Cryptosporidium egress. In this study, Cryptosporidium parvum PKG was silenced by using antisense RNA sequences. PKG-silencing significantly inhibited egress of merozoites from infected HCT-8 cells into the supernatant and led to retention of intracellular forms within the host cells. This data identifies PKG as a key mediator of merozoite egress, a key step in the parasite lifecycle.