Elongation factor 1-alpha is released into the culture medium during growth of Giardia intestinalis trophozoites

摘要

The molecular pathogenesis of the intestinal parasite Giardia intestinalis is still not fully understood but excretory-secretory products have been suggested to be important during host-parasite interactions. Here we used SOS-PAGE gels and MALDI-TOF analysis to identify proteins released by Giardia trophozoites during in vitro growth. Serum proteins (mainly bovine serum albumin) in the growth medium, bind to the parasite surface and they are continuously released, which interfere with parasite secretome characterization. However, we identified two released Giardia proteins: elongation factor-1 alpha (EF-1 alpha) and a 58 kDa protein, identified as arginine deiminase (ADI). This is the first description of EF-1 alpha as a released/secreted Giardia protein, whereas ADI has been identified in an earlier secretome study. Two genes encoding EF-1 alpha were detected in the Giardia WB genome 35 kbp apart with almost identical coding sequences but with different promoter and 3' regions. Promoter luciferase-fusions showed that both genes are transcribed in trophozoites. The EF-1 alpha protein localizes to the nuclear region in trophozoites but it relocalizes to the cytoplasm during host-cell interaction. Recombinant EF-1 alpha is recognized by serum from giardiasis patients. Our results suggest that released EF-1 alpha protein can be important during Giardia infections