Olfactory receptor trafficking involves conserved regulatory steps

Olfactory receptors are difficult to functionally express in heterologous c ells. They are typically retained in the endoplasmic reticulum of cells com monly used for functional expression studies and are only released to the p lasma membrane in mature cells of the olfactory receptor neuron lineage. A recently developed olfactory cell line, odora, traffics olfactory receptors to the plasma membrane when differentiated. We found that undifferentiated odora cells do not traffic olfactory receptors to their surface, even thou gh they release the receptors to the Golgi apparatus and endosomes. This be havior differs from other cell lines tested thus far. Differentiated odora cells also properly traffic vomeronasal receptors of the VN1 type, which la ck sequence similarity to olfactory receptors. ODR-4, a protein that is nec essary for plasma membrane trafficking of a chemosensory receptor in nemato des, facilitates trafficking of rat olfactory receptor U131 in odora and Ch inese hamster ovary cells. Olfactory receptor trafficking from the endoplas mic reticulum to the plasma membrane involves at least two steps whose regu lation depends on the maturation state of cells in the olfactory receptor n euron lineage. These results also indicate that some components of the regu latory mechanism are conserved.