Investigating How Clathrin-adaptor complex AP-2 Participates in Giardia lamblia Encystation

FELIZIANI C*; RIVERO MR*; QUASSOLLO G; ROPOLO A; TOUZ MC

INTERNATIONAL JOURNAL FOR PARASITOLOGY

ELSEVIER SCI LTD

Lugar: Amsterdam; Año: 2022

0020-7519

The protozoan parasite Giardia lamblia acquires cholesterol from the environment since it is unable to synthesize cholesterol de novo and this is vital for trophozoite growth. Conversely, the lack ofcholesterol was described as an essential event to trigger encystation, the differentiation oftrophozoites to mature cysts. During the G. lamblia cell cycle, cholesterol is acquired as a free molecule as well as through receptor-mediated endocytosis (RME) of lipoproteins. In this work, we describe the involvement of RME in the cell differentiation process of G. lamblia. We found that a reduction in the expression of the medium subunit (Glμ2) of the giardial adaptin protein GlAP2 impaired RME, triggering the process of encystation in growing cells. Contrary to expectations, decreasing Glμ2 expression produced a cohort of trophozoites that yielded significantly less mature cysts when cells were induced to encyst. Analysis of the subcellular localization of Glμ2 and the cyst wall protein 1 (CWP1) during encystation was later performed, to dissect the process. Our results showed, on one hand, that blocking RME by inhibiting Glμ2 expression, and probably cholesterol entry, is sufficient to induce cell differentiation but not to complete the process of encystation. On the other hand, we observed that GlAP2 is necessary to accomplish the final steps of encystation by sorting CWP1 to the plasma membrane for cyst wall formation. The understanding of the mechanisms involved in cyst formation should provide novel insights into the control of giardiasis, an endemic worldwide neglected disease.