ADAPTOR PROTEIN 2 REGULATES RECEPTOR-MEDIATED ENDOCYTOSIS AND CYST FORMATION IN GIARDIA LAMBLIA

RIVERO MR; VRANYCH CV; BISBAL MARIANO; MALETTO, BELKYS ANGELICA; ROPOLO, ANDREA SILVANA; TOUZ MC

BIOCHEMICAL JOURNAL

PORTLAND PRESS LTD

Año: 2010 vol. 428 p. 33 - 45

0264-6021

The parasite Giardia lamblia possesses peripheral vacuoles (PVs) that function as both endosomes and lysosomes and are implicated in the adaptation, differentiation, and survival of the parasite in different environments. The mechanisms by which this organism traffics essential proteins to these organelles and regulates their secretion have important implications in the control of parasite dissemination. In this study, we describe the participation of the heterotetrameric clathrin-adaptor protein gAP2 complex in lysosomal protein trafficking. A specific monoclonal antibody against the medium subunit (gu2) of gAP2 showed localization of this complex to the PVs, cytoplasm, and plasma membrane in the growing trophozoites. gAP2 also colocalized with clathrin in the PVs, suggesting its involvement in endocytosis. Uptake experiments using standard molecules for the study of endocytosis revealed that gAP2 specifically participated in the endocytosis of LDL. Targeted downregulation of the gene encoding gu2 in growing and encysting trophozoites resulted in a large decrease in the amount of cell growth and cyst wall formation, suggesting a distinct mechanism in which gAP2 is directly involved in both endocytosis and vesicular trafficking.