It is demonstrated that the release of extracellular vesicles from the cilium relies on actomyosin contractility supported by non-muscle myosin IIA acting downstream of the RhoA-ROCK signaling pathway, and that the cilia of these cells release EVs independently of de novo actin polymerization.
Abstract
The release of extracellular vesicles (EV) from the primary cilium is a conserved process observed in many cell types. It serves as a rapid and efficient mechanism to release select proteins from the cilium, which can be used for either intercellular communication or membrane material disposal. Previous studies have shown that the release of EVs from the cilium relies on the actin cytoskeleton and proposed several molecular mechanisms that may perform this function. Using the model of IMCD3 cells, we now demonstrate that this process relies on actomyosin contractility supported by non-muscle myosin IIA acting downstream of the RhoA-ROCK signaling pathway. We further showed that the cilia of these cells release EVs independently of de novo actin polymerization, which we confirmed using an in vivo model of mutant photoreceptor cells that release massive amounts of vesicles from their cilia instead of elaborating into light-sensitive outer segment membrane structures.
It is shown that the actomyosin cortex beneath the plasma membrane, regulated by Arp2/3 complexes containing Arpc5, acts as a gatekeeper for the membrane availability during t-tubule growth.
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