A Model of Potassium-Assisted Olfactory Sensory Neuron Response to Odorant.

Odorants interact with specialized G-protein coupled receptors lining the cilia of the olfactory sensory neuron initiating an intracellular cascade of signal transduction events resulting in cAMP-gated ion channel opening and generation of ion currents. These ion currents polarize the cilia membrane resulting in the voltage transition across the olfactory epithelium, which can be recorded as an electroolfactogram (EOG). The observed dose-dependent change of the EOG amplitude after stimulation of olfactory epithelium with the mixture of odorant and electron donors and acceptors indicates a potential involvement of electrons in the initial events of signal transduction. Our model of signal transduction consists of a dimer of the G-protein coupled olfactory receptors positioned vertically in the phospholipid bilayer between olfactory extracellular mucus layer and the intracellular cytoplasm, within the cilia of the olfactory sensory neuron. In this model, two identical receptors of the dimer form an odorant activated potassium ion channel. Prior to odorant binding at the receptor, the ion channel gate is closed. Each receptor has a single biding site for the odorant molecule on the extracellular end located within the mucus layer, and a binding site for the heterotrimeric G-protein complex within the cytoplasm. The brief binding of odorant molecules to the mucosal part of the receptors causes the ion channel to open and pass intracellular potassium ions to the extracellular mucus layer. The potassium-coupled electrons polarize the cytoplasmic portion of the receptors and facilitate activation of the bound G-protein complex thereby influencing the subsequent signal cascade.