Odorant receptor localization to olfactory cilia is mediated by ODR-4, a novel membrane-associated protein

Seven transmembrane domain receptors can be localized to different parts of the plasma membrane or to different intracellular compartments in a receptor-specific and cell type-specific fashion. We show here that the C. elegans genes odr-4 and odr-8 are required for localization of a subset of seven transmembrane domain odorant receptors to the cilia of olfactory neurons. Other cilia-signaling proteins, including ion channels, a G alpha protein, and even other receptor types, are localized via an odr-4/odr-8-independent pathway. odr-4 encodes a novel membrane protein that is expressed exclusively on intracellular membranes of chemosensory neurons, where it acts cell-autonomously to facilitate odorant receptor folding or localization.