Ciliary Intrinsic Mechanisms Regulate Dynamic Ciliary Extracellular Vesicle Release from Sensory Neurons

Extracellular vesicles (EVs) are submicron membranous structures and key mediators of intercellular communication. Recent research has highlighted roles for cilia-derived EVs in signal transduction, underscoring their importance as bioactive extracellular organelles containing conserved ciliary signaling proteins. Members of the transient receptor potential (TRP) channel polycystin-2 (PKD-2) family are found in ciliary EVs of the green algae Chlamydomonas and the nematode Caenorhabditis elegans and in EVs in the mouse embryonic node and isolated from human urine. In C. elegans, PKD-2 is expressed in male-specific EV-releasing sensory neurons, which extend ciliary tips to ciliary pore and directly release EVs into the environment. Males release EVs in a mechanically stimulated manner, regulate EV cargo content in response to mating partners, and deposit PKD-2::GFP-labeled EVs on the vulval cuticle of hermaphrodites during mating. Combined, our findings suggest that ciliary EV release is a dynamic process. Herein, we identify mechanisms controlling dynamic EV shedding using time-lapse imaging. Cilia can sustain the release of PKD-2-labeled EVs for 2 h. This extended release doesn't require neuronal transmission. Instead, ciliary intrinsic mechanisms regulate PKD-2 ciliary membrane replenishment and dynamic EV release. The kinesin-3 motor kinesin-like protein 6 (KLP-6) is necessary for initial and extended EV release, while the transition zone protein NPHP-4 is required only for sustained EV release. The dynamic replenishment of PKD-2 at the ciliary tip is key to sustained EV release. Our study provides a comprehensive portrait of real-time ciliary EV release and mechanisms supporting cilia as proficient EV release platforms.