Toll control: importins as sentinels of nuclear/cytoplasmic shuttle in Giardia lamblia

NAHUEL ZAMPONI; GONZALO MAYOL; ANDREA SILVANA ROPOLO; VICTORIA REVUELTA

cordoba

Congreso; LII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2016

SAIB

In eukaryotic cells, proteins larger than 50 kDa with nuclear localization signals (NLS) are transported across the nuclear envelope by a family of transport proteins called karyopherins or importins. This process first involved the recognition of NLSs by the adaptor importin α and binding by its N-terminal importin-β-binding (IBB) domain to importin β. In this mechanism also participates RanGTP, nuclear transport factor 2 and RCC1. In the early divergent protozoan Giardia lamblia, we have found the existence of all of these components. Particularly, we found two genes GL50803_16202 and GL50803_15106 which match by in-silico analysis with importin α and β, respectively. Immunofluorescence studies of growing transfected trophozoites over-expressing these proteins showed expected perinuclear localization. Interestingly, during the differentiation process (encystation), cells over-expressing importin α showed similar cyst production to wild-type cells while cells over-expressing importin β shown a 2-fold increase in the cyst production. The use of importazol (importin β inhibitor) showed a dramatically reduced cyst production. These results suggest that the classical nuclear transport is functional in Giardia being this mechanism essential during the differentiation process.