J. Neurochem. (2010) 113, 341–350.
Abstract
In vertebrates and some invertebrates, odorant molecules bind to G protein‐coupled receptors on olfactory receptor neurons (ORNs) to initiate signal transduction. Phosphoinositide 3‐kinase (PI3K) activity has been implicated physiologically in olfactory signal transduction, suggesting a potential role for a G protein‐coupled receptor‐activated class I PI3K. Using isoform‐specific antibodies, we identified a protein in the olfactory signal transduction compartment of lobster ORNs that is antigenically similar to mammalian PI3Kγ and cloned a gene for a PI3K with amino acid homology with PI3Kβ. The lobster olfactory PI3K co‐immunoprecipitates with the G protein α and β subunits, and an odorant‐evoked increase in phosphatidylinositol (3,4,5)‐trisphosphate can be detected in the signal transduction compartment of the ORNs. PI3Kγ and β isoform‐specific inhibitors reduce the odorant‐evoked output of lobster ORNs in vivo. Collectively, these findings provide evidence that PI3K is indeed activated by odorant receptors in lobster ORNs and further support the potential involvement of G protein activated PI3K signaling in olfactory transduction.