Phosphatidylinositol 4,5-bisphosphate Impacts Extracellular Vesicle Shedding from C. elegans Ciliated Sensory Neurons

Small secreted extracellular vesicles (EVs) mediate intercellular transport of bioactive macromolecules. How the membrane lipid phosphatidylinositol 4,5-bisphosphate (PI(4,5)P₂), 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)P₂ 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)P₂ 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)P₂ 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)P₂ did not affect cilium length, suggesting that changing PI(4,5)P₂ levels can serve as a mechanism to regulate ectosome biogenesis in response to physiological stimuli without impacting cilium morphology.