Dissecting the cell cycle regulation, DNA damage sensitivity and lifespan effects of caffeine in fission yeast

Abstract

Caffeine can modulate cell cycle progression, override DNA damage checkpoint signalling and increase chronological lifespan (CLS) in various model systems. Early studies suggested that caffeine inhibits the phosphatidylinositol 3-kinase-related kinase (PIKK) Rad3 to override DNA damage induced cell cycle arrest in fission yeast. We have previously sug gested that caffeine modulates cell cycle progression and lifespan by inhibit ing the Target of Rapamycin Complex 1 (TORC1). Nevertheless, whether this inhibition is direct or not, has remained elusive. TORC1 controls metabolism and mitosis timing by integrating nutrients and environmental stress response (ESR) signalling. Nutritional or other stresses activate the StyTSspT Ssp2 (AMP activated protein kinase complex, AMPK) pathway, which inhibits TORC1 and accelerates mitosis through Sck2 inhibition. Additionally, activa tion of the ESR pathway can extend lifespan in fission yeast. Here, we demonstrate that caffeine indirectly activates Ssp1, Ssp2 and the AMPKp regulatory subunit Amk2 to advance mitosis. Ssp2 is phosphorylated in an SspTdependent manner following exposure to caffeine. Furthermore, Ssp1 and Amk2, are required for resistance to caffeine under conditions of pro longed genotoxic stress. The effects of caffeine on DNA damage sensitivity are uncoupled from mitosis in AMPK pathway mutants. We propose that caf feine interacts synergistically with other genotoxic agents to increase DNA damage sensitivity. Our findings show that caffeine accelerates mitotic division and is beneficial for CLS through AMPK. Direct pharmacological targeting of AMPK may serve towards healthspan and lifespan benefits beyond yeasts, given the highly conserved nature of this key regulatory cellular en ergy sensor.