Characterization of a phosphoinositide-mediated odor transduction pathway reveals plasma membrane localization of an inositol 1,4,5-trisphosphate receptor in lobster olfactory receptor neurons

The role of phosphoinositide signaling in olfactory transduction is still being resolved. Compelling functional evidence for the transduction of odor signals via phosphoinositide pathways in olfactory transduction comes from invertebrate olfactory systems, in particular lobster olfactory receptor neurons. We now provide molecular evidence for two components of the phosphoinositide signaling pathway in lobster olfactory receptor neurons, a G protein alpha subunit of the G(q) family and an inositol 1,4,5-trisphosphate-gated channel or an inositol 1,4,5 trisphosphate (IP3) receptor. Both proteins localize to the site of olfactory transduction, the outer dendrite of the olfactory receptor neurons. Furthermore, the IP3 receptor localizes to membranes in the ciliary transduction compartment of these cells at both the light microscopic and electron microscopic levels. Given the absence of intracellular organelles in the sub-micron diameter olfactory cilia, this finding indicates that the IP3 receptor is associated with the plasma membrane and provides the first definitive evidence for plasma membrane localization of an IP3R in neurons. The association of the IP3 receptor with the plasma membrane may be a novel mechanism for regulating intracellular cations in restricted cellular compartments of neurons.