The Molecular Composition and Biodistribution of ARRDC1- Mediated Microvesicles

Abstract

Eukaryotic cells release into the extracellular environment diverse types of membrane vesicles primarily of endosomal and plasma membrane origin called exosomes and microvesicles, respectively, and collectively called "Extracellular vesicles (EVs). Our lab has discovered a novel subset of EVs known as ARRDC1-Mediated Microvesicles (ARMMs) that have the ability to deliver of a myriad of molecular cargos(Wang et al., 2018). The budding of ARMMs requires arrestin-domain containing protein 1 (ARRDC1), which is localized to the cytosolic side of the plasma membrane. Interestingly, similar to viruses such as HIV and Ebola, ARRDC1 also recruits the ESCRT I complex protein TSG101 to the cell surface via its proline rich tetrapeptide motif (PS/TAPP), to initiate and drive the budding of the vesicles(Nabhan et al., 2012). Although ARMMs show promise as a platform for the delivery of therapeutic molecules, the endogenous molecular composition and biodistribution of ARMMs remains mysterious. In this study, I identified conserved “ARMMs enriched” proteins utilizing high-throughput proteomic analysis. ARMMs possess a vast array of DNA/RNA components, lipids, sugars, metabolites, and glycoproteins that may illuminate potential biological/pathophysiological roles for ARMMs in vivo. In addition to this, we make progress in defining the in vivo biodistribution for ARMMs by leveraging the transparent nematode C. elegans. The worm is easily amendable to genetics, microscopy, and contains ARRDC1 homologs, in this study, we identify C. elegans ARRD-13, as the functional equivalent of ARRDC1 in the worm. Similar to ARRDC1, ARRD-13 is expressed on the plasma membrane of mammalian cells and is also secreted into the extracellular mileu. Finally, our preliminary results also suggest that endogenous ARRD-13 localizes to macrophage like scavenger cells called “coelomocytes.” Taken together, our findings shed light on the biodistribution of ARMMS as well as potential biological roles for ARMMs. Furthermore, these results may also elucidate the utility of ARMMs as a biomarker for a myriad of pathophysiological states ranging from ER stress responses to cancer pathogenesis, providing a comprehensive foundation to characterizing the biological role for ARMMs in vivo.