David Julius of the University of California, San Francisco, and Ardem Patapoutian of the Scripps Research Institute in La Jolla, California, are the two scientists who were recently awarded the 2021 Nobel Prize in Physiology or Medicine for their discoveries in how cells sense touch and temperature.
2021 Nobel Prize in Physiology or Medicine
According to Stat News, David Julius's work is involved in experiments with the chemical in hot peppers called capsaicin. Through his experiments, he was able to identify the sensory cells in the nerve endings of the skin that responds to heat.
On the other hand, Ardem Patapoutian's work unlocked the molecular basis for sensing temperature or the mechanical force involved in detecting cold. He used pressure-sensitive cells to identify a new class of sensors that respond to the mechanical stimuli in the internal organs and the skin.
The Nobel committee said that these discoveries explain how humans interpret temperature, pain, touch, and location and movement of the body, also known as proprioception.
Thomas Periman, the secretary of the Nobel committee, said that their contribution to the field of medicine unlocks one of nature's greatest mysteries. The two scientists were able to explain how stimuli are converted to nerve signals at a molecular level, which is important for survival.
The Capsaicin-Sensitive Nerve Cell
Julius figured out how capsaicin, which generates heat in hot peppers, is detected by sensory cells. According to New Scientist, his lab works in the 1990s led his team to discover capsaicin-sensitive nerve cells as he and his team took the DNA of genes known to be active in sensory cells and added fragments of DNA that do not usually respond to capsaicin.
They eventually focused on TRP receptors, such as the gene TRPV1 receptor that responds to heat and TRPM8 that responds to cold temperatures or menthol. High temperatures open up the ion channel of TRPV1 and change the voltage that makes the nerve fire, providing the sensation of heat.
Over time, researchers showed that different TRP receptors could recognize heat and other chemicals. These help sense warm temperatures.
Touch-Sensitive Cells
Almost similar to Julius, ARS Technica reported that Patapoutian and his lab members also figure out how sensory cells function to detect touch. They started by identifying a touch-sensitive cell by hooking up cells to equipment that could recognize nerve impulses and then poked these cells. Eventually, the team discovered the type of cell that sends nerve impulses when poked.
They created a list of cells that are touch-sensitive and compared them to insensitive cells. They generated a total of 72 genes that could be responsible for sensing. Then they inactivated those cells one by one to identify the single touch-sensitive cell.
Patapoutian call this protein PIEZO1, which has a close resemblance to PIEZO2. Oddly, some organisms, like flies and worms, lack this gene despite sharing similar features with vertebrates.
Previous studies reveal that mice that lack PIEZO2 could lose their ability to determine how inflated their lungs are, while those who lose this gene later in life experience blood pressure problems, bladder problems, and digestive issues. Lastly, since this gene is also involved in proprioception, the loss of this gene could cause severe balance and movement problems.
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