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Protein post-translational modification in Giardia lamblia: study of SUMOyloma and SUMOylation of cytoskeketal proteins


The network of microtubules (MTs) and microfilaments (F-actin) are crucial cytoskeletal structures responsible for the maintenance of the cell morphology, proliferation, migration and differentiation. These filaments regulate the dynamic a number of cellular processes and are reorganized, for example, during cell mitosis to form rounded cells with increased cortical rigidity. The cytoskeleton is reestablished after the cell division cycle allowing cells to return to their native shape. The modulation of such drastic changes in coordination with cell cycle progression suggests a tight regulation between the cytoskeleton, signaling cascades and mitosis. In this scenario, the post-translational modification of proteins by SUMOylation controls a series of cellular functions including the control of the cell division cycle.In mammalian cells, SUMO is covalently attached to components of the cytoskeleton as microtubule-associated proteins (MAPs), septins, nuclear actin and actin-binding proteins (ABPs). However, the role played by this modification on the cytoskeleton of protozoan parasites, as Giardia lamblia, is unknown. Results from our laboratory showed that knock down of the SUMO results in trophzoites less adhesive, decreased cell proliferation and deep morphological alterations, including at the ventral disc. Consistent with the reduced proliferation, SUMO knocked down trophozoites are arrested in G1 and in S phases of the cell cycle. To identify SUMO substrates possibly involved in these events, mass spectrometry analysis of anti-SUMO immunoprecipitates were performed. Among the identified SUMOylation targets, ±-tubulin was further validated by Western blot and confirmed to be a SUMO target in Giardia trophozoites. However, how the SUMOylation of ±-tubulin affects its functionality deserves further investigation. Considering this, in aim of this proposal focus on investigating and understanding in details the role played by the SUMO pathway on the (dis)assembly of the microtubule network (±- e ²-tubulina), on actin structures (giActina) and on the regualtion of the cell cycle in Giardia lamblia. (AU)

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