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 b eing 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 ne urons. We now provide molecular evidence for two components of the phosphoi nositide signaling pathway in lobster olfactory receptor neurons, a G prote in alpha subunit of the G(q) family and an inositol 1,4,5-trisphosphate-gat ed 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 memb ranes in the ciliary transduction compartment of these cells at both the li ght microscopic and electron microscopic levels. Given the absence of intra cellular organelles in the sub-micron diameter olfactory cilia, this findin g indicates that the IP3 receptor is associated with the plasma membrane an d provides the first definitive evidence for plasma membrane localization o f an IP3R in neurons. The association of the IP3 receptor with the plasma m embrane may be a novel mechanism for regulating intracellular cations in re stricted cellular compartments of neurons.