Authors
F S Damasceno1; K Figarella2; M Duszenko2; A M Silber1; 1 Biomedical Science Institute - USP, Brazil; 2 University of Tuebingen, Germany Discussion
Trypanosoma brucei is the causative agent of African Trypanosomiasis. In this work, we investigated the importance of glutamine (Gln) and glutamine synthetase (TbGS) for cell proliferation, cytokinesis and glutamylation of tubulin in T. brucei bloodstream forms. For this purpose, SMB cells were cultivated in HMI-9 medium Gln-free or not, with or without TbGS knockdown induction. The uninduced and induced parasites cultivated in the Gln-free medium were not able to maintain the proper proliferation rate, whereas the induced parasites, cultivated in the control medium, grew properly. The results show that parasites depend on the extracellular supply of Gln. Moreover, parasites synchronized in the G1 cell cycle phase and cultivated in Gln-free medium, were able to proceed from G1 to S and G2 phases and resulted in polyploid cells, but were not able to complete cell division. This finding suggests that Gln participates in cytokinesis, a process that depends on the integrity and dynamic of the cytoskeleton. Interestingly, parasites maintained in Gln-free medium decreased the level of glutamylated tubulin, but recovered when Gln was added back to the medium. In conclusion: Gln is important for tubulin glutamylation that is a prerequisite for cell proliferation and cytokinesis in bloodstream forms of T. brucei. 
