Plasmodium berghei: Effect of protease inhibitors during gametogenesis and early zygote development

Plasmodium berghei: The effect of five protease inhibitors, TPCK, TLCK, PMSF, leupeptin, and 1,10-phenanthroline on in vitro gametogenesis and early zygote development of P. berghei was investigated. PMSF and leupeptin showed no effect. Cysteine/serine protease inhibitors TPCK/TLCK at concentrations of 75 and 100 μM were effective on inhibiting exflagellation center formation, and this effect was reversible with the addition of l-cysteine. Exflagellation center formation was most effectively blocked by 1,10-phenanthroline (1 mM), and exflagellation center numbers were restored by the addition of Zn2+. A reduction of ookinete production was observed when TPCK/TLCK (100 μM) was added at 2 h after gametogenesis, but no effect was observed with 1,10-phenanthroline (1 mM). Our results suggest that proteolysis is important in both gametocyte activation and sexual development of P. berghei.