FIG 2.

Sporozoite invasion requires the proteasome and PKG. (A) Treatment of sporozoites with MG132 leads to a dose-dependent decrease in sporozoite invasion. PbGFP-Luc sporozoites were treated with different doses of MG132 prior to addition to HepG2 cells. The fraction of sporozoites that are intracellular 90 min after addition to HepG2 cells was determined. Results shown are from a representative experiment (average of 4 replicates ± standard deviations). The experiment was performed twice. (B) Treatment of sporozoites with MG132 and TSP has an enhanced effect on sporozoite invasion compared to treatment with TSP or MG132 alone. PbGFP-Luc sporozoites were treated with either TSP (0.5 μM) alone or in combination with MG132 (5 μM) prior to addition to HepG2 cells. The fraction of sporozoites that are intracellular 90 min after addition to HepG2 cells was determined. Results shown are the average of three experiments, each done in triplicate, ± standard errors. (C) Invasion by sporozoites with reduced PKG activity (PKG T₆₁₉Q-HA) is significantly more sensitive to MG132 inhibition than invasion by wild-type sporozoites (PKG-HA). Results shown are the average of four experiments, each done in triplicate or quadruplicate ± standard errors. Data were analyzed using an unpaired t test (*, P < 0.05; **, P < 0.005; ***, P < 0.0005; ns, not significant).