Throughout life, cells communicate to coordinate the organism’s response to stimuli. Cells release extracellular vesicles that carry signals to alter development or disease response. Released vesicles can also seal the cell membrane after damage. The goal of our research is to discover how vesicles bud from the surface of cells, how cells take up extracellular vesicles, and what signals extracellular vesicles send in animals. Defining how vesicles form is an essential first step to designing strategies to induce or suppress their formation and thereby determine their signaling capability. This research could also lead to new strategies to monitor or influence disease severity.

Most cells release extracellular vesicles (EVs) carrying lipid, protein, and nucleic acid signals. While much is known about their signaling potential, EV formation is poorly understood. As a postdoctoral fellow, Dr. Wehman used the genetic model system C. elegans to discover the first protein that prevents EV budding, TAT-5. In tat-5 mutant worms, too many EVs are produced. TAT-5 is an evolutionarily conserved protein that regulates the distribution of specific lipids across the two layers of the plasma membrane. This finding suggests that lipids have instructive roles in regulating membrane dynamics. Our research aims to define exactly how TAT-5 and lipid distribution regulate EV budding.

In addition to TAT-5, conserved regulators of viral budding also have a role in EV budding in C. elegans, including the small GTPase RAB-11 and the membrane-sculpting complex known as ESCRT. Using the same strategy that identified TAT-5, RAB-11, and the ESCRT machinery, we are using the power of C. elegans genetics to identify additional proteins that regulate EV budding. Our studies are building a pathway of proteins that regulate TAT-5 localization and activity and thereby EV release. The proteins we identify may be used to alter EV production in other systems, which could impact the availability of non-invasive biomarkers and have the potential to influence disease state.

In addition to overproducing EVs, tat-5 mutant worms also have defects in EV uptake. Studying tat-5 and other mutants revealed that cells take up organelles released during cell division, including the mitotic midbody and the meiotic polar body. Thus, we can also use C. elegans to study the pathways of EV uptake and determine their fate. Analyzing defects in EV uptake complements our studies on EV budding and will allow us to elucidate the interplay of lipids and lipid regulators during dynamic remodeling of the membrane. Studying the fate of EVs also provides important insights into the mechanisms of EV signaling.

Finally, studying the mechanisms of EV production has provided us with techniques to induce or prevent their formation. This allows us to test which signaling pathways require EVs for signaling to occur. In flies and mice, EVs carry morphogens important for development. We are studying how changing EV production or uptake affects conserved signaling pathways during C. elegans development. In summary, our research will determine the roles of lipid and protein molecules during membrane dynamics and will define the intercellular signaling roles of EVs.