Forming Exosomes without all the Founding Players

MOYANO S; LALLE M; TOUZ MC

Congreso; LI Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular. SAIB; 2016

Exosomes are vesicles released following multivesicular bodies (MVBs) fusion with the plasma membrane and have been implicated in a broad range of functions. MVBs formation is driven by the endosomal sorting complex required for transport (ESCRT) machinery. Five ESCRT complexes (0, I, II, III and Vps4) are sequentially recruited from the cytoplasm to the surface of the endosomal membrane. Although many of these components are present across all eukaryotic lineages, only a subset of them is present in Giardia lamblia. Using stable transfected parasites expressing HA-tagged proteins, we localized components of the ESCRT II and Vps4 complexes in the cytoplasm and nuclear membrane in trophozoites. Analysis of the interaction between ESCRT components using YTH assays highlighted the existence of intra and extracomplex interactions, suggesting that a conserved form of ESCRT assembly occurs in this parasite. Despite the absence of some ESCRT players and MVBs, Giardia seems to be able to form and secrete exosomes. Microvesicles, isolated from trophozoites grown in serum free medium, were enriched in known exosome markers, such as gActin, g14-3-3 protein and a gSNARE protein. Further analysis interfering with the ESCRT machineries will disclose whether exosome formation in Giardia is an ESCRT-dependent or independent pathway.