[Secreted proteins of Giardia duodenalis--characteristic and role in biology of the parasite]

Abstract

The article presents the current knowledge on the proteines under question. The first analysed E-S products released by G. duodenalis was a polydisperse hydrophobic complex (16.5-225 kDa), protease VI sensitive, chloroform-methanol insoluble. Based on inhibition studies cysteine protease and metalloprotease were detected in the complex. The further analysis revealed that a 58 kDa heat stable as wall as protease sensitive glycoprotein secreted by G. duodenalis trophozoites is highly immunogenic for the hosts. Before encystation, G. duodenalis trophozoites secrete leucine-rich cyst wall proteins: CWP1, CWP2 and CWP3. Steady-state levels of CWPs gene transcripts are low in non-encysting trophozoites but increase more than 100-fold during encystation. Another protein, which expression also increases during encystation is gGSP (Giardia Granule-Specific Protein). The protein possesses typical strucutre of calcium-binding proteins. Inhibition of gGSP expression abolishes cyst wall formation, suggesting that this protein regulates Ca(2+)-dependent degranulation of encystation-specific secretory vesicles (ESVs) during cyst wall formation.