Stress Responsive Signal Transduction and the Control of Longevity Dirk Bohmann University of Rochester Dept. of Biomedical Genetics Lifespan is not a “hardwired” property of organisms and can be tuned by environmental and genetic parameters*. What are the critical regulators and effectors of longevity? Are they accessible to therapeutic manipulation? **at atleast leastin insome someorganisms organisms Oxidative Stress and Aging The rate with which oxidative damage accumulates throughout life is proportional to lifespan Fly Human Sohal et al. (1993) PNAS vol. 90 Stadtman (1992) Science vol. 257 Oxidative Stress and Aging Conditions that extend lifespan delay accumulation of damage: • long-lived mutants • caloric restriction • low temperature • decreased Insulin/IGF signaling What Regulates the Accumulation of Oxidative Damage? Stress Defense Signaling Pathways • • • • JNK p38 Nrf2 p53 and more rapid, massive, and transient Respond to Acute Stresses, e.g. Xenobiotics, Radiation, Injury, Hypoxia/Reperfusion Stress Defense Signaling Pathways • • • • JNK p38 Nrf2 p53 and more anti anti oxidant oxidant genes genes repair repair proteolysis proteolysis Graded Responses cell cell cycle cycle arrest arrest apoptosis apoptosis Stress Defense Signaling Pathways • • • • JNK p38 Nrf2 p53 and more Are acute stress response mechanisms relevant for aging? Stress Defense Signaling Pathways • JNK • Nrf2 Are acute stress response mechanisms relevant for aging? JNK The Drosophila JNK Signal Transduction Pathway Signal JNKKK Slp, Ask, Tak JNKK Hep JNK Bsk Foxo MKP Puc Jun/Fos Transcription Factors Anti oxidant genes are regulated by JNK Metallothionein Hsp 68 Glutathion S Transferase D1 Ferritin ¾ paraquat induction e.g.: Inducible by ROS stress in a JNK dependent manner JNK signaling confers resistance to acute oxidative stress Paraquat Hep Bsk Puc stress defense genes JNK signaling confers resistance to acute oxidative stress Paraquat Hep Bsk Puc stress defense genes JNK signaling confers resistance to acute oxidative stress Paraquat Hep Bsk Puc stress defense genes JNK signaling confers resistance to acute oxidative stress Paraquat Hep Bsk Puc stress defense genes JNK signaling protects against acute oxidative stress Gain of function JNK genotypes extend longevity Foxo dependently 120% survival proportion 100% Hep 80% 60% Dfoxo21/+ Dfoxo25/+ 40% Bsk +/+ pucE69/+,Dfoxo21/+ 20% pucE69/+,Dfoxo25/+ pucE69/+ 0% 0 10 20 30 40 50 Age (days) 60 70 80 90 100 Foxo 0.5x Puc Gain of function JNK genotypes extend longevity Foxo dependently 120% survival proportion 100% Hep 80% 60% Dfoxo21/+ Dfoxo25/+ 40% Bsk +/+ pucE69/+,Dfoxo21/+ 20% 0.5x Puc pucE69/+,Dfoxo25/+ pucE69/+ 0% 0 10 20 30 40 50 60 70 80 90 100 Foxo Age (days) Decrease of the negative regulator Puckered efficiently extends Lifespan Puc heterozygosity reduces protein damage, but does not affect growth, development and fertility JNK activation reduces protein damage, but does not affect growth, development and fertility Conclusions • Activation of Foxo by the JNK pathway can confer a longevity phenotype. • JNK signaling can delay the accumulation of oxidative damage throughout life of the organism. • JNK target genes both raise resistance against acute oxidative stress, and extend lifespan. • Lifespan effects require a long term moderate activation of JNK signaling. Nrf2 The NRF2/Keap signaling pathway Xenobiotics (TPA) Oxidants (H2O2) Phenolic “anti-oxidants” (tBHQ) Nrf2 Keap1 Keap1 Keap1 (an actin-binding protein) is the cytoplasmic inhibitor of Nrf2. Maf ARE: ROS signaling (mediated by inducers) dissociates Nrf2 from Keap1. Nrf2 Stress response genes Antioxidant Response Element Nfr2 can then translocate to the nucleus and trans activate its target genes. The NRF2/Keap signaling pathway Chemo preventive agents (i.e. Oltipraz) Chemotherapy Drugs Nrf2 Keap1 Keap1 NRF2 and Cancer NRF2 agonists are in clinical trials as cancer preventive agents. Maf ARE: Nrf2 Stress response genes Antioxidant Response Element Mutations in Keap can boost resistance to chemotherapy in non-small cell lung cancer. Drosophila Nrf2 and Keap1 Homologs - CncC Drosophila CncC/Nrf2 activates an antiOxidative stress gene expression program and a negative feedback loop. + CncC gstD1 thioredoxin gstE1 keap1 CncC activity can be measured with a GFP reporter CncC reporter responds to oxidative stress CncC is inducible by Cancer Chemoprevention agents CncC activation protects from acute oxidative stress CncC gain-of-function extends lifespan CncC 0.5x Keap1 CncC gain-of-function extends lifespan CncC 0.5x Keap1 Decrease of the negative regulator Keap1 extends Lifespan Conclusions • Artificial activation of acute stress response signaling pathways can extend lifespan. Speculations • The genetic programs that confer acute stress resistance overlap with those that regulate longevity. • Some components of acute stress response may also function in lifespan control. These may not be the highly regulated ones, but factors that set thresholds or base level activities. • Drugs that affect stress signaling, such as Nrf2 activators might be effective to counteract aging or its manifestations. Oxidative Stress Longevity Signals ? Signaling pathways Foxo, Nrf2, et al. “Stress defense genes” “Longevity genes” Henri Henri Jasper Jasper Carla Carla(Meng) (Meng Wang Wang Gerasimos Gerasimos Sykiotis Sykiotis