Superior Proteome Stability in Long-Lived Clams
The proteome is the set of all proteins expressed by an organism; stability in expression levels over time indicates fewer changes in the operation of metabolism, which might also indicate slower aging. Looking at proteomic stability as a hallmark of longevity seems a little tautological to me, but nonetheless now that the tools exist to cheaply and accurately measure genome-wide gene expression levels you will see researchers talking about this data and how it relates to degenerative aging. Long-lived naked mole rats, for example, appear to have a more stable proteome across their lifespans, and here we see that this is also the case for the longest-lived clam species:
Bivalve mollusks have several unique traits, including some species with exceptionally long lives, others with very short lives, and the ability to determine the age of any individual from growth rings in the shell. Exceptionally long-lived species are seldom studied yet have the potential to be particularly informative with respect to senescence-resistance mechanisms. To this end, we employed a range of marine bivalve mollusk species, with lifespans ranging from under a decade to over 500 years, in a comparative study to investigate the hypothesis that long life requires superior proteome stability. This experimental system provides a unique opportunity to study closely related organisms with vastly disparate longevities, including the longest lived animal, Arctica islandica.Specifically, we investigated relative ability to protect protein structure and function, both basally and under various stressors in our range of species. We found a consistent relationship between species longevity, resistance to protein unfolding, and maintenance of endogenous enzyme (creatine kinase) activity. Remarkably, our longest-lived species, Arctica islandica (maximum longevity of more than 500 years), had no increase in global proteome unfolding in response to several stressors. Additionally, the global proteome of shorter-lived species exhibited less resistance to temperature-induced protein aggregation than longer-lived species.
A reporter assay, in which the same protein's aggregation properties was assessed in lysates from each study species, suggests that some endogenous feature in the cells of long-lived species, perhaps small molecular chaperones, was at least partially responsible for their enhanced proteome stability. This study reinforces the relationship between proteostasis and longevity through assessment of unfolding, function, and aggregation in species ranging in longevity from less than a decade to more than five centuries.