Who is the "commander" of protein production?

Whether single-celled, mammalian, plankton or sequoia, growth is the fundamental principle of
all life on Earth.
The starting point for growth is usually the cell: to achieve this, the cell must double its composition and composition in a short time so that it can divide and start growing
.
The process behind this is complex and has not yet been deciphered to the final detail
.
Now, however, a team of researchers from Würzburg has succeeded in identifying a key mechanism
in this process.
Prof.
Utz Fischer from the Biological Center Würzburg (JMU) of Julius Maximilian University and Prof.
Jörg Vogel from the Würzburg Helmholtz Institute for RNA Infection (HIRI) have published their findings
in the latest issue of Cell Reports.

Ribosomes deliver new proteins

"In order for cells to grow, they have to produce a lot of new proteins
.
This happens in special factories inside cells known as ribosomes," explains Utz Fischer
, director of biochemistry at JMU.
In each human cell, up to 10 million ribosomes are dedicated to this task
.
Thus, most of the cell's resources and energy reserves are used not only for the production of proteins, but above all for the production and maintenance
of the ribosomes themselves.
It is thought that this requires up to 50% of cellular energy reserves, making ribosome production the "most expensive" process
in cells.

Of course, cells cannot consume such a large amount of energy and raw materials
irrationally.
Therefore, it constantly monitors its environment to ensure adequate nutrition and other growth stimuli
at all times.
As soon as the "supply situation" deteriorates, it stops growing and stops producing new ribosomes – but will still maintain a supply of enough ribosomes to be able to grow
again without delay when conditions are better.

Central command center

The central command post for this process is the so-called mTORC1 signaling complex, which is a nutritional sensor
for cells.
Dr.
Cornelius Schneider, a joint scientific collaborator of the two research labs and first author of the now published study, explains: "All the information about nutrition and other growth stimuli converges on
this signaling complex.
"

Based on this information, mTORC1 coordinates cellular responses to changing environmental conditions and controls ribosomal protein production
.
As the researchers demonstrated, it used the help of another protein, the scientific name of which is LARP1
.
"mTORC1 can affect the LARP1 protein in such a way that, in the case of nutritional deficiencies, it binds to the signaling sequence located at the starting position of mRNA, all ribosomal proteins
.
This leads to a decrease in protein production," explains Schneider
.
For example, messenger RNA is the transporter
of proteins' blueprint from the nucleus to the ribosome.

The basic supply is always there

Although ribosomal protein production is reduced to an absolute minimum, it is never completely shut down
.
"This means that cells can start producing large amounts of ribosomes
again at any time.
This allows it to react extremely quickly to changing environments and move from growth to energy efficiency," says
Utz Fischer.
In this way, it is possible for cells to maintain a basic supply
of a certain ribosomal protein mRNA at all times, even under poor conditions.

This also dovetails with another finding: LARP1 itself and the signaling network around mTORC1 are deregulated in different types of cancer because they are central
to determining cell growth.

An unusual mode of baseline translation adjusts cellular protein synthesis capacity to metabolic needs