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Monday, April 09, 2007
3:00 PM - 4:00 PM
CNLS Conference Room (TA-3, Bldg 1690)

Colloquium

Role of Zn nanoclusters in signal transduction in olfactory neurons

Vitaly Vodyanoy
Auburn University

Proteons, small particles of misfolded proteins (40-250 nm) polymerized around inorganic centers, were found in animal and human blood, plants, and soil. Proteons form by reversible seeded aggregation of proteins around protein nucleating centers (PNCs). PNCs are comprised of 1–2-nm metallic nanoclusters containing 40–300 atoms. Each milliliter of human blood contained ~7 × 1013 PNCs and ~3 × 108 proteons. We recently discovered that G-protein governed olfactory signals are strongly enhanced by PNCs. We hypothesize that PNCs (small metallic nanoclusters) provide an electronic coupling between G-proteins and extracellular receptors (signals). The primary events of olfactory transduction occur at the cilia of olfactory receptor neurons and involve the binding of odorants to receptor proteins followed by activation of heterotrimeric guanine nucleotide-binding proteins (G-proteins), and effector enzymes. Two different effector enzymes, G-protein-coupled adenylyl cyclase and phospholipase C, are known to control primary responses of olfactory neurons to odor stimulation in invertebrates and vertebrates. Although the excitatory reactions involving signal pathways are well explored, the mechanism of transferring of signal from the receptor protein to G-protein is unknown. In 1996 Luka Turin [A spectroscopic mechanism for primary olfactory reception, Chemical Senses Vol 21/ 6 pp773-791] has provided a plausible mechanism of signal transduction between the odorant receptor and G-protein. He proposed that a process called "inelastic electron tunneling" is responsible for this transduction. For this electron transfer Turin suggested that a zinc ion binding sites are present both on the odorant receptor protein and the G-protein. While Turin’s theory has not been proved, it seems quite reasonable. We hypothesized that zinc metal nanoclusters and not zinc ions play role in the electron tunneling and provide a mechanism for the signal transduction between receptor proteins and G-proteins. In order to examine this hypothesis we made experiments showing that introduction of zinc nanoclusters (or PNC) to a rat olfactory epithelium or to a single olfactory neuron dramatically increases the electrical response to odorant. The effect is dose dependent and reversible. The nanoclusters made of Cu, Au, and Ag produce no significant effects when they are added instead of zinc (or PNC) particles. These results may be useful for understanding of molecular mechanisms of initial events in olfaction. The work is supported by a grant from Fetzer Foundation.

Host: Lev Boulaevskii, LANL/T-11