Do you think that cell biology can no longer surprise us? Professor Allan Albig ofUniversity of Boise has something to tell you. The organelles, those tiny compartments that inhabit our cells, are revealing unexpected secrets. Like the fluidly moving drops in one of those 70s lamps (remember them), some of them move, merge and separate without having membranes around them. A discovery that not only challenges our knowledge, but opens new perspectives on the very origin of life. Let me try to explain better.
Organelles that challenge tradition
Remember high school biology class? Organelles were described as small organs inside the cells, each with its own specific task and protective membrane. mitochondria produce energy, the lysosomes they recycle waste, the core holds the DNA and so on. This was more or less the standard model, seemingly unchangeable.
But science is made of surprises. A mid 2000s, researchers have made an extraordinary discovery: some organelles function perfectly without membranes. A revelation that has shaken the foundations of cell biology. These "rebel" organelles they behave completely differently than we expected. We call them biomolecular condensates, and are radically changing our understanding of how cells work. cells.
A liquid dance in the heart of the cell
If we could observe these biomolecular condensates under the microscope, we would see a fascinating spectacle. They behave like bubbles in a liquid: they continually merge, separate, and reform. They are not made of wax, but of proteins and RNA molecules that prefer to interact with each other rather than with their surroundings.
As it turned out in 2022, researchers
have identified about 30 types of these membrane-free condensates: they exceed the number of traditional organelles, which stops at about a dozen.
In other words, the “true” standard model is made up of “mixed” cells rather than “regimented” cells. And it is interesting to note that these organelles have very different functions. Some are involved in the formation of cells reproductive, others in protein production. But for many others, the precise role remains a mystery to be discovered.
Proteins That Break the Rules
One of the most surprising aspects of this discovery is the way in which these organelles challenge our understanding of protein structure. Since 1950, when scientists they observed for the first time the structure of myoglobin, it has always been thought that the shape of a protein determines its function. But the proteins that form biomolecular condensates do not follow this rule. They contain “disordered” regions, without a defined shape. When they were discovered in the early 80s, these intrinsically disordered proteins (IDPs) have puzzled researchers. Their existence and role in the formation of biomolecular condensates is forcing us to rethink some fundamental principles of cell biology.
A new look at bacteria
The discovery of these organelles is also revolutionizing our understanding of cells bacterial. Traditionally, bacteria were thought to be very simple organisms, lacking organelles. We now know that this is not the case.
Although only the 6% of bacterial proteins have disordered regions, compared to 30-40% of eukaryotic cell proteins, researchers have identified several biomolecular condensates in bacteria. This discovery is showing us that even the simplest organisms
they have a greater level of complexity than we imagined.
The Origin of Life in a New Light
Perhaps the most fascinating perspective opened up by this discovery concerns the origin of life on Earth. Until now, scientists have always thought that the first forms of life must have been enclosed in lipid membranes. But the formation of these membranes required materials that were probably not available on the early Earth.
The discovery that RNA can spontaneously form biomolecular condensates opens up completely new scenarios. Perhaps the first living molecules did not need membranes to organize themselves into proto-cells.
“Wireless” Organelles: Towards New Cures for Neurodegenerative Diseases
The implications of these findings go far beyond basic biology. Researchers are already developing new therapeutic approaches based on the manipulation of biomolecular condensates for the treatment of diseases such as Alzheimer's, Huntington's disease and ALS. Drugs capable of promoting or dissolving these condensates are being tested. It is still too early to say whether these approaches will be successful, but the prospects are promising.
The road is still long, but one thing is certain: membrane-less organelles are showing us that cells They still have many secrets to reveal. And perhaps, before long, school biology textbooks will have to be rewritten to include these fascinating actors of the microscopic world.
1 comment on “Organelles, new discoveries rewrite cellular biology”
Comments are closed.