Elucidating the Protein Composition and Biogenesis Mechanisms of Tumor Microvesicles

Motivated by their established roles in cancer progression and clinical promise, we explore tumor microvesicle (TMV) biology through the investigation of their molecular constituents and the underlying mechanisms dictating biogenesis. Utilizing a proximity ligase assay, we have developed a novel approach to characterizing TMV protein cargos. These studies enhance our overall understanding of the molecular “signature” of TMVs, which will act as a library to gain insight into all areas of their biology. Among the proteins identified, we confirm and characterize the annexin A1- S100A11 tethering complex in the biogenesis of TMVs. We demonstrate these structures form membrane contact sites between ER and ARF6-positive endosomes, which facilitate the positioning of these endosomal compartments to the cell surface for MAPK signaling and TMV release. We further determine the formation of this tethering complex is dictated by annexin A1 post-translational modifications. Finally, we provide preliminary evidence to suggest that annexin A1 phosphorylation and cleavage impact not only TMV biogenesis but other key pathways in the endolysosomal system. Overall, this dissertation utilizes novel approaches to studying TMVs and makes significant strides in our understanding of their biology.