Biological complexity: nucleolus functions to protect (Introduction)

by David Turell , Wednesday, July 17, 2019, 19:26 (1956 days ago) @ David Turell

The nucleolus protects cells fro misfolded protein molecules:

https://phys.org/news/2019-07-function-nucleolus.html

" A new study shows that the nucleolus is also a site of quality control for proteins.

"When cells are stressed, proteins tend to misfold and to aggregate. To prevent proteins from clumping, some are temporarily stored in the nucleolus. The special biophysical conditions found in this organelle help to prevent harmful protein aggregation,

***

"The nucleolus is a structure found in the cell nucleus, which was first described in the 1830s. In the 1960s it was recognized that ribosomes, the cell's protein factories, are assembled in this organelle. Researchers have known for some time that proteins known as chaperones move into the nucleolus under certain circumstances. It has been suggested that this relocation is related to protein production. However, the new work shows that the chaperones that migrate to the nucleolus are already bound to stress-sensitive proteins.

"As a pioneer of chaperone research, F.-Ulrich Hartl and his team previously discovered that chaperones are crucial for the correct folding of proteins, and play a central role in protein quality control. If proteins fail to fold correctly, their misfolded forms can accumulate and clump together.

***

"Together they were able to show that the misfolded luciferase protein behaved differently within the nucleolus than in the rest of the cell. "In the nucleolus, misfolded proteins were kept in a liquid-like state instead of aggregating," explains Frédéric Frottin, first author of the study. This is possible due to the specific biophysical conditions that prevail within the organelle.

"'Proteins that usually tend to aggregate are stored in a less dangerous form during stress, which protects cells from damage. Once the cell has had time to recover, the proteins can be refolded and released from the nucleolus," continues Frottin. At this point, the cells have the capacity to activate further mechanisms that enable the protein to be repaired or degraded. The researchers also demonstrated that this protective mechanism fails if the cell stress lasts too long. "This is a new mechanism that maintains the integrity of the cell," says Mark Hipp. Maintaining this integrity is ultimately essential to inhibit the development of disease and retard the aging process. "

Comment: Protein molecules can perform proper functions only when folded in just the right configurations. Living biochemistry performs functions at high speed and must be protected from misfolding. This mechanism had to present when first life began or it would have continued to live. Only design fits.