The SUMO-conjugating system in Giardia lamblia

VRANYCH CV; RIVERO MR; TOUZ MC; ROPOLO ANDREA

Armação dos Búzios, RJ, Brasil

Congreso; . XIII International Congress of Protistology; 2009

Reversible post-translational modifications of proteins have critical roles in many cellular processes owing to their ability to cause rapid changes in functions of pre-existing proteins and sucellular structures. Sumoylation, a reversible post-translational modification of proteins by the small ubiquitin-related modifiers (SUMOs), is crucial in a variety of biological processes, including transcriptional regulation, signaling transduction, cell cycle progression and differentiation. SUMO proteins are highly conserved across eukaryotes and consist of four components in mammals, SUMO-1, SUMO-2, SUMO-3, and SUMO-4. There is only one SUMO gene SMT3 in budding yeast, while there exist at least eight SUMO paralogs in plants. In parasites, protein sumoylation has been described in Plasmodium falciparum and in Toxoplasma gondii. Here, we report that the sumoylation system is present in Giardia lamblia by means of the conserved components, including a single SUMO gene, the enzymes required for SUMO processing and ligation and the SUMO proteases for the conjugate disassembly. After amplification by PCR, all of the components of the sumoylation pathway were used to transfect Giardia lamblia trophozoites and the localization of each one was determined. In order to find sumoylation substrates, immunoblotting experiments using anti-SUMO mAb were performed. We could identify the enzyme arginine deiminase as a sumoylated protein. The ability of anti-SUMO mAb to immunoprecipitate the 85 kDa band of gADI confirmed the gADI-SUMO interaction. Proteins modified by SUMO could alter their sub-cellular localization, activity or stability. We found that during differentiation of the parasite mainly the sumoylated form of gADI translocate to the nucleus, inducing the downregulation of the encystation process. Overall, the SUMO conjugation system appears to be a functionally pathway for protein modification in Giardia lamblia with initial data indication that it may plays a role during cyst development. Supported by CONICET PIP1073.