Author: Liu Amy
Date: May 2008
A new study published in Nature shows that insects' ability to smell evolved differently from that of other organisms. It has been believed that the ability to smell in all organisms, including insects, is dependent on a general pathway, or sequence of biochemical reactions within cells. Now Leslie Vosshall, head of the Laboratory of Neurogenetics and Behavior at Rockefeller University, and Kazushige Touhara, researcher at the University of Tokyo, say that insects' olfactory senses bypass these pathways altogether.
The olfactory pathway involves the interaction of a scent molecule and a large protein known as a G-protein coupled receptor, on the surface of a cell in the nose of an animal. This interaction activates a sequence of biochemical reactions ultimately leading to the opening of an ion channel, which causes ions to flow into the cell and an electrical signal to reach the brain. The new model of insect smell, however, cuts out the G-protein pathway and shows that scent molecules directly activate the ion channel.
The discovery came when Touhara and colleagues at the University of Tokyo performed experiments on cells with insect olfactory receptors. The researchers found that the cells' response to scent molecules was too quick for the complicated G-protein pathway to be feasible. "The most consistent interpretation is that these are ion channels directly gated by odors," explained Vosshall. Deactivating certain proteins essential to the G-protein pathway did not affect the response of the ion channels to the scent molecules, indicating that the pathway was not essential to insects' sense of smell.
This newfound understanding of insects' olfactory abilities may help researchers understand how "DEET" and other insect repellents work, says Vosshall. "I am optimistic that we can come up with blockers specific for this very strange family of insect olfactory ion channels," she said.
Written by Amu Liu
Reviewed by Pooja Ghatalia, Jeff Kost
Published by Pooja Ghatalia.