Agonist-induced GPCR shedding from the ciliary surface is dependent on ESCRT-III and VPS4.

BACKGROUND

Membrane trafficking of G protein-coupled receptors (GPCRs) is crucial for temporal and spatial control of cell-surface GPCR signaling. Receptor internalization is a well-documented method cells use for regulating a wide variety of GPCRs following their exposure to agonists.

RESULTS

We report that, upon agonist stimulation, a GPCR called vasoactive intestinal peptide receptor 2 (VPAC2) is shed, rather than being internalized, in vitro and in vivo, from the membrane of primary cilia--solitary hair-like organelles that project from the cell surface. VPAC2 is released into the extracellular milieu in the form of ciliary ectosomes that are devoid of exosome markers. The agonist-induced VPAC2 shedding is selective, as shown by the fact that other ciliary membrane proteins including two ciliary GPCRs are not shed with VPAC2. VPAC2 ectosome shedding is dependent on several components of endosomal sorting complexes required for transport (ESCRT), including a subset of ESCRT-III, VPS4, and LIP5. Agonist-stimulated VPAC2 is important for ciliary-ectosome generation because it allows VPS4 and LIP5 to transiently accumulate in primary cilia. Shedding of VPAC2 from the ciliary surface results in termination of intracellular VPAC2 signaling.

CONCLUSIONS

Agonist-induced GPCR shedding from the ciliary surface may represent an additional mode of GPCR trafficking and signal regulation.