The gradual accumulation of damage to all kinds of molecules in the cell is often considered as the primary cause of aging. This escalating damage could cause the progressive failure of cell processes, finally leading to deterioration and death. Increased degradation of damaged proteins and replacement by resynthesized proteins, referred to as protein turnover, could minimize this escalating protein damage, therefore slowing down the aging process.
At the Braeckman lab for aging physiology at Ghent University, researchers study aging in Caenorhabditis elegans, a small 1-millimeter roundworm with a maximal lifespan expectancy of only two weeks. A single mutation, discovered many years ago, can double the worm's lifespan. However, the underlying molecular mechanism for this doubling is not well understood.
Ineke Dhondt, a researcher in the Braeckman team, verified the protein turnover hypothesis in this long-lived mutant. This was done in collaboration with the Pacific Northwest National Laboratory in the USA. Using mass spectrometry, rates of protein synthesis and degradation of individual proteins could be measured in worms with normal and doubled lifespans.
Intriguingly, the researchers observed slower synthesis and degradation rates for the majority of proteins in the long-lived worm. Proteins with unchanged turnover rates were found too. The increased protein turnover, as predicted by the hypothesis, could not be found. This calls into question the story of damage accumulation that could be avoided by degradation and re-synthesis of proteins.
Over the last few years, a new view emerges in biogerontology that challenges the role of molecular damage in the aging process. Damage does occur, but it probably is not the primary cause of aging. Recent insights support the hyperfunction theory, which states that the synthesis of biomolecules is less orchestrated in aging individuals, leading to uncoordinated synthesis of irrelevant macromolecules (hypertrophy), causing a progressive decline of cell functionality. Since the mutation in the long-lived worm studied in this research is located in a gene responsible for the stimulation of growth processes, it seems plausible that lower growth in this mutant results in decreased hypertrophy and therefore slowing of the aging process. It is likely that aging is not caused by damage accumulation, but rather by derailed growth and developmental processes.
This research was published in the journal Cell Reports.
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