A newly created model helps to clarify the processes by which cells grow old and die, and which are known to be involved in the onset of neurodegenerative disorders like Alzheimer’s and Parkinson’s disease.
The study describing this model, “Proteostasis collapse is a driver of cell aging and death,” was published in PNAS.
To remain healthy, cells must be able to produce proteins and chaperone them: keeping proteins correctly folded, and destroying those that aren’t.
But as cells age, oxidative stress — an imbalance between reactive and inflammatory free radicals and the ability of cells to detoxify them — slowly leads to the accumulation of irreparably damaged proteins inside cells that eventually overwhelm their “quality control” mechanisms.
“Irreparably damaged proteins accumulate with age, increasingly distracting the chaperones from folding the healthy proteins the cell needs. The tipping point to death occurs when replenishing good proteins no longer keeps up with depletion from misfolding, aggregation, and damage,” the researchers wrote.
Investigators with the Laufer Center for Physical & Quantitative Biology at Stony Brook University created a model that is able to predict the lifespan of the round worm Caenorhabditis elegans, an animal model often used in aging studies, based on its protein quality control mechanisms.
In their study, scientists showed their model’s predictions matched the results of experiments they performed on round worms to assess the effects of oxidative damage on the animals’ lifespan.
In one experiment, they found that animals raised at a temperature of 20 degrees Celsius (about 68 degrees Farhenheit) had an average lifespan of 20 days. Worms were raised at higher temperatures and in the presence of free radicals (byproducts of oxidative stress), however, had lifespans of only a few hours.
“As the cell is stressed by heat, proteins unfold, misfold, and aggregate. Chaperones are recruited, but with age, the synthesis [production] of ‘good protein’ and the chaperoning of those spontaneously unfolding ultimately succumb to damage levels, at which bad protein becomes overwhelming,” the researchers said.
Their work also found that mutant animals with more chaperones or proteasomes — a complex of enzymes responsible for the destruction of unnecessary or damaged proteins — lived longer.
All these findings were in agreement with the foundations of their model, which stated that oxidative stress and protein instability increase with age and are the root cause of cell degeneration.
“This modeling is unique by being mathematically detailed and describing a broad range of cellular processes across the cell’s whole proteome [all proteins found in a cell],” Ken A. Dill, PhD, a distinguished professor and director of the Laufer Center for Physical & Quantitative Biology, and a study co-author, said in a news release.
“Often, aging-related studies look at the effects of one or two proteins at a time, rather than seeking, more generally, the cellular aging mechanism itself,” Dill added.
This study also sets the foundation for future research into the molecular origins of aging disorders associated with protein misfolding, such as Parkinson’s.
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