Odor-stimulated phosphatidylinositol 3-kinase in lobster olfactory receptor cells.

Two antagonists of phosphoinositide 3-OH kinases (PI3Ks), LY294002 and Wortmannin, reduced the magnitude of the receptor potential in lobster olfactory receptor neurons (ORNs) recorded by patch clamping the cells in vivo. An antibody directed against the c-terminus of human PI3K-P110 beta detected a molecule of predicted size in the outer dendrites of the ORNs. Two 3-phosphoinositides, PI(3,4)P(2) (1--4 microM) and PI(3,4,5)P(3) (1--4 microM) applied to the cytoplasmic side of inside-out patches taken from cultured lobster ORNs, reversibly activated a Na(+)-gated channel previously implicated in the transduction cascade in these cells. 3-Phosphoinositides were the most effective phosphoinositide (1 microM) in enhancing the open probability of the channel. Collectively, these results implicate 3-phosphoinositides in lobster olfactory transduction and raise the need to consider the 3-phosphoinositide pathway in olfactory transduction.