The nucleolus is a well-known structure in the cell nucleus that is easily visible under a light microscope. The nuclear proteome is rich in stress-sensitive proteins, suggesting that effective protein quality control mechanisms are in place to ensure conformational maintenance.
This nuclear structure is knowing to be the site of ribosome production. A new study showing that the nucleolus is also a site of quality control for proteins. When cells are stressing, proteins tend to misfold and to aggregate. To prevent proteins from clumping, some are temporarily storing in the nuclear. In mammalian tissue culture cells; under stress conditions misfolded proteins entered the granular component phase of the nucleolar.
Nuclear protein aggregates have been observed in various neurodegenerative disorders such as amyotrophic lateral sclerosis and Huntington’s disease, but protein quality control in the nucleus is not well understood. Here, we used a combination of fluorescence imaging, biochemical analyses, and proteomics to investigate the fate of stress-denatured and aberrant proteins in the nucleus, focusing specifically on the role of the nucleolus and its phase-separated nature in protein quality control.
Functions for nucleolus
The nucleolus is a structure finding in the cell nucleus; which was first described in the 1830s. In the 1960s it was recognizing that ribosomes; the cell’s protein factories, are assembling in this organelle. owever, new work showing that chaperones that migrate to nucleolus are already bound to stress-sensitive proteins.
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. If proteins fail to fold correctly, their misfolded forms can accumulate and clump together. The resulting protein aggregates can often be observing in neurodegenerative diseases, such as Alzheimer’s, Parkinson’s or Huntington’s disease.
By fusing the enzyme to a fluorescent protein; the scientists can track it under the microscope; and observe whether the protein is correctly folding or is misfolding and forms aggregates. able to show that stressing cells by heating them to 43°C results in the transport of the misfolded luciferase protein; together with the chaperones, into the nucleolus.
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; misfolding proteins were keeping in a liquid-like state instead of aggregating. Proteins that usually tend to aggregate are storing in a less dangerous form during stress; which protects cells from damage.