Novel Role of BKCA Channels in Exosomes

Student: Mayukha Dyta ’24
Research Mentor: Harpreet Singh (The Ohio State University Department of Physiology and Cell Biology)

Exosomes, extracellular vesicles, are important to cells because they help communication, transfer DNA, and deliver cargo from one cell to another. In order to deal with different environments in the body throughout its journey, we hypothesized that exosomes contain a large channel called Ca2+- gated K+ channels (BKCA channels) to regulate K+ (Potassium). By using the planar lipid bilayer system to replicate the cell wall environment, we were able to record BKCA channel activity in exosomes.

Exosomes are extracellular vesicles packaged within the cells and are important in intercellular communication, transferring genetic information, deliver the cargo to the target cells, and can be markers of diseases. During their journey from one cell to the other cell, they face differential ionic gradients. The mechanism of handling different ionic environments throughout the circulation is unknown. We predict that exosomes possess an ion-exchange mechanism and we hypothesize that exosomes contain large conductance voltage- and Ca2+- gated K+ channels (BKCA channels) to counter intracellular vs. extracellular potassium gradient. Hence to validate the hypothesis, we incorporated the lysed exosomal membranes in a planar lipid bilayer system to record the channel activity of BKCA channels. Exosomes showed voltage-dependent activity and were sensitive to Ca2+ ions in a dose-dependent manner. The channel activity of the exosomal BKCA channel was blocked by paxilline, a specific blocker for BKCA channels. Furthermore, we incorporated a novel Near Field Electrophysiology (NFE) method to show the presence of K+ currents mediated through the BKCA channel in intact exosomes. NFE result suggests K+ currents mediated through BKCA were sensitive to iberiotoxin, a specific inhibitor of the BKCA channel. The localization of BKCA channels in exosomes was established through immunocytochemical analysis. Exosomes isolated from plasma of wild type and BKCA knockout (KO) mice revealed a lesser number of circulating exosomes in KO mice and were smaller in size compared to the exosomes from BKCA WT. Overall, the study elucidates the novel role of BKCA channels in exosome survival and structural integrity.