Dopamine receptor 1 localizes to neuronal cilia in a dynamic process that requires the Bardet-Biedl syndrome proteins

Primary cilia are nearly ubiquitous cellular appendages that provide important sensory and signaling functions. Ciliary dysfunction underlies numerous human diseases, collectively termed ciliopathies. Primary cilia have distinct functions on different cell types and these functions are defined by the signaling proteins that localize to the ciliary membrane. Neurons throughout the mammalian brain possess primary cilia upon which certain G protein-coupled receptors localize. Yet, the precise signaling proteins present on the vast majority of neuronal cilia are unknown. Here, we report that dopamine receptor 1 (D1) localizes to cilia on mouse central neurons, thereby implicating neuronal cilia in dopamine signaling. Interestingly, ciliary localization of D1 is dynamic, and the receptor rapidly translocates to and from cilia in response to environmental cues. Notably, the translocation of D1 from cilia requires proteins mutated in the ciliopathy Bardet-Biedl syndrome (BBS), and we find that one of the BBS proteins, Bbs5, specifically interacts with D1.