[LUM#10] Cells in crisis
Energy conservation does not only apply to our lifestyle, it also determines the survival of our cells. François Favier and Vincent Ollendorff have identified the major role played by the REDD1 protein in reducing the energy expenditure of cells under stress.
"If we had to summarize the role of REDD1, we could say that it's a bit like the Pierre Rabhi of the cell, slowing down energy expenditure to adapt to conditions of scarcity," explain François Favier and Vincent Ollendorff, researchers at theMuscle Dynamics and Metabolism Laboratory, with a touch of humor. For nearly six years, they have been studying the reaction of muscle cells when faced with stressful situations that cause muscle atrophy.
Vital energy
Walking, running, catching an object, holding a yoga pose, talking... All these actions are made possible by muscle cells, which produce mechanical tension when they contract. To contract, these cells consume energy, or ATP. Each cellhas "a kind of factory capable of producing the ATP it needs to function. This is the mitochondrion," explains François Favier.
Under normal circumstances, this energy is used by the cell to synthesize the proteins essential for its functioning. " Liver cells produce proteins for digestion, eye cells for vision, and muscle cells for contraction," summarizes Vincent Ollendorff. This protein synthesis takes place in the endoplasmic reticulum, located near the mitochondria.
Sense of priorities
But what happens when the cell is faced with a stressful situation such as physical exertion, fasting, or a decrease in oxygen supply? "These situations lead to an inability to provide sufficient energy," explains François Favier. " To save itself , the cell must prioritize its activities and put protein synthesis, which consumes too much energy, on standby." The cell will then release proteins capable of slowing down energy expenditure.
In this role as an energy regulator, research had long identified the AMPK protein, "a kind of firefighter for the cell," as Vincent Ollendorff describes it, but the two Montpellier researchers are the first to highlight the early role of REDD1. "REDD1 could be compared to a fire extinguisher, " continues the biologist. " It acts before AMPK and in a more targeted, more appropriate way."
How does it work? "REED1 physically moves the energy-producing factory, the mitochondria, away from the site of protein synthesis in order to redirect energy to where the muscles contract and produce muscle tension," explains François Favier. Once the stressful situation has passed, the mitochondria and reticulum move closer together to resume the production of new proteins. This proves that in times of energy crisis, adaptation remains the best solution.
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