The 2021 Nobel prize for physiology or medicine has been awarded to David Julius and Ardem Patapoutian for discovering how cells detect temperature and touch.
“This really unlocks one of the secrets of nature,” said the secretary of the Nobel committee, Thomas Perlmann. “It explains at a molecular level how these stimuli can be converted into nerve signals. It is something that is crucial for our survival.”
The ability to sense heat and mechanical pressure is vital for everything from avoiding getting burned to knowing when we need to urinate, but until recently we didn’t know exactly how nerve cells detect heat and touch.
To discover how nerve cells detect heat, David Julius at the University of California, San Francisco, exploited the fact that capsaicin in chillies activates heat receptors. In the 1990s, his team took the DNA of genes known to be active in sensory cells and added fragments to cells that don’t normally respond to capsaicin.
By trying out thousands of different fragments to see which enabled the cells to make the receptor and respond to capsaicin, they identified a protein now called TRPV1 that codes for an ion channel that sits in the cell membrane of nerves. Higher temperatures open the ion channel, leading to a change in voltage that makes the nerve fire and thus provides the sensation of heat.
Teams led by Julius and Ardem Patapoutian, at Scripps Research in La Jolla, California, then independently discovered a similar ion channel called TRPM8 that opens in response to cold rather than heat. Both teams exploited the fact that menthol triggers these cold receptors. Several similar ion channels have since been discovered, allowing a range of different temperatures to be sensed.
To identify touch receptors, Patapoutian’s team used cells that produce an electrical signal when poked. The team also identified 270 genes that might code for touch receptor proteins. The researchers switched off these genes in the cells one by one.
In this way, they found PIEZO1, an ion channel that opens in response to mechanical pressure. That enabled them to identify a similar protein called PIEZO2. These receptors help the body detect things such as blood pressure, bladder pressure and breathing in addition to external touches.
Perlmann said he spoke briefly to Julius and Patapoutian before the announcement. “I only had a few minutes to talk to them but they were incredibly happy and as far as I could tell they were very surprised and little bit shocked maybe,” he said.
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