Involement of importins in the translocation of arginine deiminase to the nuclei in Giardia lamblia

GONZALO MAYOL; NAHUEL ZAMPONI; AGOSTINA SALUSSO; ANDREA ROPOLO

Mar del Plata

Congreso; LI Reunion Anual de la Sociedad Argentina de Investigacion en Bioquimica y Biologia Molecular; 2015

Inthe protozoan parasite Giardia lamblia,the enzyme Arginine Deiminase (ADI) plays a key role during the proliferativeand the differentiation process. Particularly, during encystation ADItranslocates from the cytoplasm to the nuclei. In eukaryotic cells, proteinslarger than 50 kDa with nuclear localization signals (NLS) are transportedacross the nuclear envelope by a family of transport proteins calledkaryopherins or importins. This process first involved the recognition of NLSsby the adaptor importin á and binding by its N-terminal importin-â-binding(IBB) domain to importin â. We found in the Giardia database two genes (GL50803_16202 and GL50803_15106) which by in-silico analysis matchwith importin á and â respectively. GL50803_16202 (importin á) shows theclassical armadillo repeats composed of a pair of alpha helices that form ahairpin structure. GL50803_15106 (importin â) shows24 HEAT repeats that form rod-like helical structures. An inhibitor of nucleartransport like importazol (importin â inhibitor) reduced the growth of Giardia trophozoites and the number ofcyst produced. Also, there is an accumulation of ADI over the nuclear envelope.These results suggest that in Giardiathe classical nuclear transport is functional being this mechanism employs byADI to translocate from the cytoplasm to the nuclei.