Phosphatidylinositol 4,5-bisphosphate Impacts Extracellular Vesicle Shedding from C. elegans Ciliated Sensory Neurons
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Small secreted extracellular vesicles (EVs) mediate intercellular transport of bioactive macromolecules. How the membrane lipid phosphatidylinositol 4,5-bisphosphate (PI(4,5)P 2 ), which plays a critical role in many cellular processes, impacts EV biogenesis is unclear. The primary cilium, a sensory organelle protruding from most non-dividing cells, transmits signals by shedding EVs called ectosomes. Here, we altered ciliary PI(4,5)P 2 by manipulating expression of the type I phosphatidylinositol 4-phosphate 5-kinase (PIP5K1) PPK-1 and deletion of the phosphoinositide 5-phosphatase (INPP5E) inpp-1 , then determined the impact on release of EVs that carried cargos tagged with fluorescent proteins. We discovered that increasing PI(4,5)P 2 differentially affected ectosome shedding from distinct compartments, decreasing biogenesis of an EV subpopulation from the ciliary base, but enhancing budding from the cilium distal tip. Altering PI(4,5)P 2 levels also impacted the abundance and distribution of EV cargos in the cilium, but not the sorting of the protein cargos into distinct subsets of ectosomes. Finally, manipulating PI(4,5)P 2 did not affect cilium length, suggesting that changing PI(4,5)P 2 levels can serve as a mechanism to regulate ectosome biogenesis in response to physiological stimuli without impacting cilium morphology.
Summary Statement
Extracellular vesicles (EVs), released from most, if not all, cell types, share bioactive cargo that cannot readily cross the plasma membrane with recipient cells. EVs play numerous roles in physiological processes as well as the propagation of pathophysiological conditions, including cancer, neurodegenerative, kidney, and cardiovascular diseases. Here, we sought to determine the impact of the membrane lipid phosphatidylinositol (4,5)-bisphosphate (PI(4,5)P 2 ) on EV biogenesis. We used a genetic approach to manipulate PI(4,5)P 2 levels in the primary cilium, a specialized sensory organelle that serves as a platform for signal transmission by shedding EVs. We discovered that high PI(4,5)P 2 differentially impacts two distinct EV subpopulations, decreasing shedding of ectosomes derived from the ciliary base, but increasing budding from the cilium distal tip. This work defines a new role for PI(4,5)P 2 in the regulation of EV biogenesis and ciliary biology.
