Sirtuins regulate proteomic responses near thermal tolerance limits in the blue mussels and .

The blue mussels and are competing species with biogeographical ranges set in part by environmental exposure to heat and hyposalinity. The underlying cellular mechanisms influencing interspecific differences in stress tolerance are unknown, but are believed to be under regulation by sirtuins, nicotinamide adenine dinucleotide (NAD)-dependent deacylases that play a critical role in the cellular stress response. A comparison of the proteomic responses of and to an acute heat shock in the presence and absence of the sirtuin inhibitor suramin (SIRT1, 2 and 5) showed that sirtuins affected molecular chaperones, oxidative stress proteins, metabolic enzymes, cytoskeletal and signaling proteins more in the heat-sensitive than in the heat-tolerant Interactions between sirtuin inhibition and changes in the abundance of proteins of β-oxidation and oxidative stress in suggest a greater role of sirtuins in shifting metabolism to reduce the production of reactive oxygen species near thermal limits. Furthermore, RNA-binding proteins initiating and inhibiting translation were affected by suramin in and , respectively. Western blot analysis showed that the levels of mitochondrial sirtuin 5 (SIRT5) were generally three times higher and increased with acute heat stress in response to sirtuin inhibition in but not in , suggesting a possible feedback response in the former species and a greater reliance on SIRT5 for its stress response. Our findings suggest that SIRT5 plays an important role in setting interspecific differences in stress tolerance in by affecting the stress proteome.