Nobel Prize in Medicine awarded for discovery of the cellular mechanism behind the sense of touch
This year, the Nobel Committee for Physiology or Medicine awarded the Medicine Prize to two American researchers for their efforts to unravel the molecular and genetic mysteries behind the sense of touch. The recipients, Dr David Julius of the University of San Francisco and Dr Ardem Patapoutian of Scripps Research in La Jolla, Calif., Were jointly honored this week “for their discoveries of temperature and touch receptors.”
Professor Abdel El Manira, neuroscientist and member of the Nobel Committee, explained that “without the receptors we would not be able to feel our world, to feel the urge to take our hand away from a flame, or even from ourselves. stand up. The discoveries have profoundly changed our view of how we perceive the world around us. “
There is perhaps an unspoken irony that the Nobel committee decided to attribute, during such a cataclysmic pandemic where people were taken into custody and invited to social distancing to stem the tides of infection and death. repeated, their prestigious award to a problem is literally in depth.
But on closer inspection, we understand the importance of these discoveries that have escaped scientists until recently. The results offer a much more convincing assessment of human society and provide a deep dialectical connection between the physical world and life. In other words, life, more than just a replication, interacts with the world. But it does so through the limitations imposed by the physical world. And through this interaction, he learns to change.
Dr Patapoutian, in a review article published in the journal Nature last year, wrote: “From the sound of a whisper to the hammer on a finger, many familiar environmental cues occur in the form of mechanical forces. Mechanotransduction, the conversion of mechanical disturbances into electrochemical signals, is conserved in all areas of life. It is perhaps the oldest sensory process and it may have protected the earliest protocells from the osmotic and mechanical forces that threatened to shatter their membranes.
The award for understanding the mechanism behind touch and temperature is only the latest, perhaps the last, recognized by the Nobel Committee. During the press conference following the announcement, Dr Julius said: “This is the last major sensory system to go through molecular analysis… for things like temperature and pressure sensors, we really didn’t have examples of the types of molecules. [used in vision and smell] that we might be looking for.
In 1961 George von Békésy, a Hungarian biophysicist, received the Nobel Prize for his work on the impact of sound on the human cochlea, translating sound wave frequencies into nerve signals leading to the brain. In 1967, three recipients, Ragnar Granit, Haldan Keffer Hartline and George Wald, shared the award “for their discoveries concerning the primary physiological and chemical visual process in the eye”. Then, in 2004, Dr Linda Buck and Dr Richard Axel were credited with discovering hundreds of odor receptors in the nose and how the olfactory system was organized and connected to the brain.
Dr Julius’ discovery was based on work first carried out by Hungarian researchers in the late 1940s. The use of large doses of capsaicin, the active ingredient in chili peppers that causes the sensation of heat, rubbed on lab mice relieved pain. Although discoveries of drugs followed that could help lower body temperature, decrease inflammation, and promote dilation of blood vessels, no one understood how these mechanisms worked until Dr. Julius and his team are embarking on a systematic search for molecules responsible for the detection of capsaicin.
After an exhaustive process of trial and error, his team identified a gene in sensory nerve cells that responded to the “burning” ingredient. This gene, now known as TRPV1, instructs the cell to build a protein known as ion channel which allows the cell to perceive Heat also painful and react.
Ion channels are special proteins (or gates) housed in a cell’s membrane that allow physical communication with the external environment of the cell through the influx and efflux of various ions. These ions act as chemical signals that lead to a cascade of secondary and tertiary signals to which the cell responds, leading to a concerted response from the living organism.
The work of Julius and Patapoutian converged, albeit independently, when they both used menthol to discover the receptor to detect cold, named TRPM8, including several others that have intermediate responses.
Patapoutian then undertook research to identify similar ion channels that involved a response to mechanical forces. This involved working with cell lines that emit a small burst of electrical signals when pushed with a micropipette, a fine-tipped instrument for collecting tiny amounts of fluids. Through the iterative process of turning off genes in these cells, they identified the crucial protein for sensing pressure, an ion channel they named PIEZO1.
In a thought-provoking statement examining the discovery of numerous mechanical-electrical ion channels, authors Dr Dominique Douguet and Dr Eric Honoré, writing in the journal Cell, said: “The opening of mechanosensitive ion channels at the plasma membrane of mammalian cells, in the microsecond range, is the first event to occur during mechanical stimulation.” Precisely, the shear forces which stretch and bend a cell lead to opening these doors with the ensuing response which converts the mechanical stimulation into a chemical reaction which leads to the formation of a sensation at the molecular level at an exorbitant rate.
Since then, many mechanically activated ion channels have been identified that provide a conscious sense of touch and the unconscious sense associated with the regulation of blood pressure and other organic functions involved in the life process. This capacity of our cells to perceive mechanical forces is a fundamental process preserved in the evolution of life.
As the Nobel Committee’s statement noted, “The laureates identified critical missing links in our understanding of the complex interplay between our senses and the environment. The groundbreaking discoveries … of this year’s Nobel Laureates have enabled us to understand how heat, cold and mechanical forces can initiate the nerve impulses that allow us to perceive and adapt to the world around us.
However, Professor Patrick Haggard of the Institute of Cognitive Neuroscience at University College London said it best. “This is the closest understanding scientists have had to our own conscious experiences.”