
Nobel Prize in Medicine 2021
On October 4, the Nobel Committee announced that the 2021 Nobel Prize
in Biomedical Sciences - the first prize of the Nobel season - belonged
to two American biologists David Julius and Ardem Patapoutian for their
discoveries of mechanisms, body temperature, and touch sensors.
Professor
David Julius is an American physiologist at the University of
California at San Francisco, and Professor Ardem Patapoutian is an
Armenian-American molecular biologist with the Scripps Research
Institute in La Jolla, California.
The two biologists previously
received the BBVA Foundation's Prize in Biology and Medicine for their
work. You can find out more about the Nobel Prize in Medicine 2021 at Medicinecontact.com
How do humans perceive temperature and pressure?
The
human ability to sense heat, cold, and touch is essential to survival
and underlies our interactions with the world around us.
In
everyday life, we take these sensations for granted, but how do nerve
impulses begin to sense temperature and pressure? This question has been
solved by this year's Nobel Prize winners in Biomedical Sciences.
Biologist
David Julius used capsaicin - a spicy compound from chili peppers that
causes the sensation of heat - to identify a sensor in the skin's nerve
endings that responds to heat. Biologist Ardem Patapoutian, using
sensitive cells, discovered a sensor that responds to mechanical stimuli
in the skin and internal organs.
These groundbreaking
discoveries have ignited extensive research, giving us a rapid
understanding of how the human nervous system perceives hot, cold, and
mechanical stimuli. These biologists have identified extremely important
relationships in the complex interplay between the human senses and the
environment.
One of the great mysteries facing humanity is how
humans perceive their environment. The mechanisms inside the human
body's senses have piqued our curiosity for thousands of years, such as
how light is detected by the eye, how sound waves affect our inner ear,
and how Various chemical compounds interact with receptors in the nose
and mouth to produce odors and tastes. . .
Humans also have
countless other ways of perceiving the world around them, like walking
barefoot on the grass on a hot summer day can help people feel the heat
of the sun, the caress of the wind, and grass underfoot. These
sensations of temperature, touch, and movement are essential for human
adaptation to ever-changing surroundings.
In the 17th century,
the philosopher René Descartes envisioned threads connecting different
parts of the skin to the brain. Accordingly, a foot that touches an open
flame sends a mechanical signal to the brain. Subsequent discoveries
revealed the existence of specialized sensory neurons that record
changes in the human environment.
In 1944, two scientists Joseph
Erlanger and Herbert Gasser received the Nobel Prize in Biomedical
Sciences that year for discovering different types of sensory nerve
fibers that respond to different stimuli, for example to painful and
painless touch.
Since then, it has been shown that neurons are
highly specialized to detect and transmit different types of stimuli,
allowing for the nuanced perception of human surroundings. Specifically,
the human ability to feel the difference in the texture of a surface
through the fingertips, or the ability to distinguish between both
pleasant warmth and painful heat….
Unknown discoveries
In
the late 1990s, biologist David Julius of the University of California,
San Francisco (USA) analyzed how the chemical compound capsaicin causes
the burning sensation that people feel when exposed to chili peppers.
Capsaicin has been known to activate the nerve cells that cause pain, but how this chemical function is an unanswered question.
Julius
and colleagues created a library of millions of DNA fragments that
correspond to genes expressed in sensory neurons that can respond to
pain, heat, and touch.
Julius and colleagues hypothesized that
the library would include a DNA fragment encoding a protein capable of
reacting with capsaicin. They mimicked individual genes in cultured
cells that would normally not respond to capsaicin. After a painstaking
search, scientists have identified a single gene that can make cells
sensitive to capsaicin. This gene, identified to encode a novel ion
channel protein and capsaicin receptor, was named TRPV1.
The
discovery of TRPV1 is a major breakthrough, leading the way towards the
discovery of additional temperature-sensing receptors.
Acting
independently, biologists David Julius and Ardem Patapoutian both used
the chemical menthol to identify TRPM8, a receptor-activated in cold.
Additional ion channels associated with TRPV1 and TRPM8 were identified
and activated by a range of different temperatures.
David Julius'
discovery of TRPV1 is a breakthrough that allows people to understand
how temperature differences can generate electrical signals in the
nervous system.
And Ardem Patapoutian and colleagues have
identified for the first time a cell line that emits measurable
electrical signals when individual cells are poked with a micropipette.
The
scientists assumed that the receptor activated by mechanical force was
an ion channel, and in the next step, 72 candidate genes encoding
possible receptors were identified. These genes were in turn inactivated
to reveal the gene responsible for mechanosensitivity in the cells
studied.
After an arduous search, Patapoutian and his colleagues
succeeded in identifying a single gene that silences cells that render
cells insensitive to micropipette probing. A new and completely unknown
mechanically induced ion channel has been discovered and named Piezo1,
after the Greek word for pressure.
Through its similarity to
Piezo1, a second gene was discovered and named Piezo2. Sensory neurons
were found to express high levels of Piezo2, and further studies have
firmly established that Piezo1 and Piezo2 are ion channels that are
directly activated when pressure is applied to the cell membrane.
The
Patapoutian breakthrough led to a series of demonstrations that the
Piezo2 ion channel is essential for touch. Furthermore, Piezo2 has been
shown to play an important role in the all-important sensing of body
position and movement, known as proprioception. In a further study,
Piezo1 and Piezo2 channels have been shown to regulate other important
physiological processes including blood pressure, respiration, and
urinary bladder control.