期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 108, 期 2, 页码 822-827出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1017983108
关键词
mammal; olfaction; olfactory transduction
资金
- National Institutes of Health [DC06904]
- Human Frontier Science Program Organization Long-Term Fellowship
The sense of smell begins with odorant molecules binding to membrane receptors on the cilia of olfactory receptor neurons (ORNs), thereby activating a G protein, Golf, and the downstream effector enzyme, an adenylyl cyclase (ACIII). Recently, we have found in amphibian ORNs that an odorant-binding event has a low probability of activating sensory transduction at all; even when successful, the resulting unitary response apparently involves a single active G alpha(olf)-ACIII molecular complex. This low amplification is in contrast to rod phototransduction in vision, the best-quantified G-protein signaling pathway, where each photoisomerized rhodopsin molecule is well known to produce substantial amplification by activating many G-protein, and hence effector-enzyme, molecules. We have now carried out similar experiments on mouse ORNs, which offer, additionally, the advantage of genetics. Indeed, we found the same low probability of transduction, based on the unitary olfactory response having a fairly constant amplitude and similar kinetics across different odorants and randomly encountered ORNs. Also, consistent with our picture, the unitary response of G alpha(+/-)(olf) ORNs was similar to WT in amplitude, although their G alpha(olf)-protein expression was only half of normal. Finally, from the action potential firing, we estimated that <= 19 odorant-binding events successfully triggering transduction in a WT mouse ORN will lead to signaling to the brain.
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