Identification of End-Binding 1 Protein as Novel α-4 Giardin-Binding Partners in Giardia lamblia Trophozoites

Background: Giardia lamblia (syn. G. intestinalis, G. duodenalis) is a primitive opportunistic protozoon, and one of the earliest differentiated eukaryotes. Despite its primitive nature, G. lamblia has a sophisticated cytoskeleton system, which is closely related to its proliferation and pathogenicity. Meanwhile, α giardin is a G. lamblia-specific cytoskeleton protein, which belongs to the annexin superfamily. Interestingly, G. lamblia has 21 annexin-like α giardins, i.e., more than higher eukaryotes. The functional differences among α giardin members are not fully understood. Methods: We took α-4 giardin, a member of α giardin family, as a research object. A morpholino-mediated knockdown experiment was performed to identify the effect of α-4 giardin on G. lamblia trophozoites biological traits. A yeast two-hybrid cDNA library of G. lamblia strain C2 trophozoites was screened for interaction partners of α-4 giardin. Co-immunoprecipitation and fluorescent colocalization confirmed the relationship between G. lamblia EB1 (gEB1) and α-4 giardin. Results: α-4 Giardin could inhibit the proliferation and adhesion of G. lamblia trophozoites. In addition, it interacted with G. lamblia EB1 (gEB1). Conclusions: α-4 Giardin was involved in proliferation and adhesion in G. lamblia trophozoites, and EB1, a crucial roles in mitosis, was an interacting partner of α-4 giardin.