Extracellular vesicles (EVs) secreted by eukaryotic and prokaryotic cells to transport lipids, proteins and nucleic acids to the external environment have important roles in cell-cell communication through cargo transfer. We identified and characterized EVs from Entamoeba histolytica, a protozoan parasite and a human pathogen. Conditioned medium from amebic parasites contained particles consistent with the expected size and morphology of EVs. Mass spectrometry was used to characterize the EV proteome and showed that it was enriched in common exosome marker proteins including proteins associated with vesicle formation, cell-signaling, metabolism, and cytoskeletal proteins. Additionally, the EVs were found to selectively package small RNAs (sRNA), which were protected within the vesicles against RNase treatment. Sequencing analysis of the sRNA contained in EVs revealed that the majority were 27nt in size and represented a subset of the cellular antisense small RNA population that has previously been characterized in Entamoeba RNAi pathway proteins, including Argonaute were also present in amebic EVs. Interestingly, we found that the amebic EVs impact inter-cellular communication between parasites and altered encystation efficiency. EVs isolated from encysting parasites promoted encystation in other parasites whereas EVs from metabolically active trophozoites impeded encystation. Overall, the data reveals that Entamoeba secrete EVs that are similar in size and shape to previously characterized exosomes from other organisms and that these EVs contain a defined protein and small RNA cargo and have roles in intercellular communication amongst parasites and influence growth kinetics.
Characterization of extracellular vesicles from Entamoeba histolytica identifies roles in intercellular communication that regulates parasite growth and development