Identification of exosomes in the infective stage of entomopathogenic nematodes

• Published in: Journal of extracellular vesicles Vol. 7; p. 251
• Main Authors: Toubarro, Duarte, Frias, Jorge, Marcilla, Antonio, Galiano, Alicia, Simões, Nelson
• Format: Journal Article
• Language: English
• Published: Abingdon John Wiley & Sons, Inc 01-01-2018
• Subjects: Actin; Actinin; Clathrin; Connectin; Cytoskeleton; Dynamin; Entomopathogenic nematodes; Exosomes; Infective stages; Myosin; Pathogenicity; Proteins; Serine; Size distribution; Transthyretin; Tubulin; Vesicles
• ISSN: 2001-3078

Background: Entomopathogenic nematodes are insect parasitic nematodes able to kill the host short after the contact. Currently, the pathogenicity of these organisms is ascribed to excretory/secretory products (ESP), released by the infective nematode. In an attempt to identify the molecular effectors, we noticed the presence of exosome-like vesicles for the first time in Steinernema carpocapsae. Methods: Exosomes were isolated from the ESP by size-exclusion chromatography (Sepharose CL-2B) and particle size was determined by nanotracking analysis (NTA). Proteomic profile of exosomes was determined by MS/MS analysis. Exosomes in induced nematodes were detected by TEM analysis and size estimated. Results: Although almost 90% of the exosomes had a predicted size determined by TEM between 30 and 130 nm, the global size distribution determined by NTA ranged from 90.6 nm to 201.6 nm being the mean 146.1 nm and the mode 161.2 nm. The majority of exosomes detected by TEM were localized near to nematode lateral fields or alae and a few crossing the cuticle. MS/MS analysis of exosome vesicles allow to the identification of filament disassembly proteins (e.g. unc-78, dynamin, dystonin, titin), several cytoskeletal-related proteins (actin, tubulin, a-actinin and myosin) and vesicle transport-related proteins (clathrin, transthyretin), which are proteins known to be released by cells through a vesiculation process. However, the majority of proteins identified in S. carpocapsae exosomes belong to molecular binding and catalytic activity categories. In the former category, protein binding (GO:0005515) and carbohydrate binding (GO:0030246) were the most represented, and in the second category metalloendopeptidases and serine peptidases were the most relevant. Summary/Conclusion: Our findings reveal that exosomes are another mechanism by which EPNs interact with the host providing a mechanical way for the delivery of molecular effectors.