Effects of rapamycin on life span and on expression of TOR and S6K in Brachionus calyciflorus (Rotifera)

Abstract

The mechanistic target of rapamycin (mTOR) coordinates a complex signal pathway from translation to autophagy that is a key regulator of not only growth and proliferation but also metabolism and aging. mTOR is sensitive to many environmental and endocrine stimuli. We investigated the influence of TOR signaling on aging and reproduction of the rotifer Brachionus calyciflorus using rapamycin as an exogenous inhibitor. We found that 2 and 4 μM rapamycin extended B. calyciflorus life span by 15 and 22%, respectively compared with controls (p < 0.05). The reproductive peak was significantly delayed by rapamycin at 2 and 4 μM (p < 0.01), but the pre- and post-reproduction periods were not significantly different from controls (p > 0.05). Partial cDNAs coding 375 bp for TOR and 951 bp for S6 kinase (S6K) were obtained from B. calyciflorus expressed sequence tags. The identities of the deduced amino acid sequences of B. calyciflorus cDNAs to their human orthologs were 58% for TOR and 68% for S6K. TOR and S6K mRNA expression were up- or down-regulated by different rapamycin concentrations (0.5, 1, 2, 4, 8, and 16 μM) and treatment intervals (control, 12, 24, 36, and 48 h). The results indicated that TOR inhibition acted additively to extend rotifer life span, with up- and down-regulation simultaneously impacting reproduction and gene expression.