Abstract

To date, microRNAs (miRNAs) in human plasma have been discovered within circulating microvesicles (cMV), bound to Argonaute 2 and associated with HDL and LDL microvesicles. The protein GW182 shares an association with both multivesicular bodies and the Argonaute family of proteins. GW182 has the capacity to bind all human Argonaute proteins (1-4) and their associated miRs. In the cell, GW182 is associated with the membrane of multivesicular bodies and has the ability to congregate Argonaute-loaded RISC complexes. In addition, GW182 has been observed on the surface of purified exosomes.

Here we investigated the relationship of GW182 with Argonaute and cMV in human plasma and urine. A monoclonal antibody directed toward GW182 was used to capture the protein. This isolate also contained Argonaute proteins as determined by Western analysis. The co-precipitation of GW182 and Argonaute suggests that these two proteins retain their functional relationship in plasma. RNA was then isolated from precipitates for miRNA detection and analysis. The GW182-associated miRNA profile from human plasma contained individual miRNAs whose abundance either equaled or surpassed that of their matched Argonaute 2 immuno-precipitated miRNAs. This implies that GW182 maintains an association with the family of Argonaute proteins and a subset of cMV in human plasma.