Monday, 17 March 2014
Science Starting To Identify the Molecular Bases of the Sense of Touch
When it comes to senses such as vision, scientists have known for some time which molecules are responsible for transduction—the conversion of physical stimuli into nerve impulses. Until recently, however, the molecular bases of the sene of touch remained ill-defined. But in an article first published online in the journal Nature in December 2012, Dr. Zhiqiang Yan and his research team from the University of California at San Francisco (UCSF) reported having found what they believed was the missing link in transduction for the sense of touch.
This link is NOMPC (No mechanoreceptor potential C), a protein molecule in the transient receptor potential (TRP) family of ion channels. TRP ion channels are large protein molecules that are embedded in the cell membrane. A part of each of these molecules forms a pore that opens to let ions pass through the membrane and initiate nerve impulses. And in the case of NOMPC, the UCSF team discovered, the stimulus to which the channel receptor is sensitive consists of slight mechanical deformations in the skin.
Determining the role of NOMPC was a two-stage process. First, having observed an intriguing abundance of this molecule at the tips of the nerve endings of Type III sensory fibres in the larvae of Drosophila flies, the team successfully attempted to specifically deactivate this protein. The result: the larvae no longer reacted to gentle touch. Second, after further complex genetic manipulations, the researchers showed that neurons that do not normally respond to touch begin to do so after NOMPC protein molecules have been inserted in their membranes.
It thus appears that touch, an important sense that accompanies us throughout our lives, starting with our mother’s first caresses, is based on a simpler transduction mechanism than scientists had once thought: the presence of a molecule that is sensitive to mechanical stretching. What scientists still have to do is determine is the exact mechanism that enables the channel to open, and identify the analogous molecule in humans. Even the first part of this task may take years, as it did for the receptor for acetylcholine (as described in the French-language article to which a link is provided below).
We would love to report back on this research when we devote a future section of this website entirely to the sense of touch. But first we will have to find new sources to keep developing new content for this site. You can help: see our message in the column with the Donate button, to the right.
Secrets of gentle touch revealed
Drosophila NOMPC is a mechanotransduction channel subunit for gentle-touch sensation
Recherche specialisée : le récepteur à l’acétylcholine
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