Acevaltrate promotes apoptosis and inhibits proliferation by suppressing HIF-1α accumulation in cancer cells.

Acevaltrate is a natural product isolated from the roots of Valeriana glechomifolia F.G.Mey. (Valerianaceae) and has been shown to exhibit anti-cancer activity. However, the mechanism by which acevaltrate inhibits tumor growth is not fully understood. We here demonstrated the effect of acevaltrate on hypoxia-inducible factor-1α (HIF-1α) expression. Acevaltrate showed a potent inhibitory activity against HIF-1α induced by hypoxia in various cancer cells. This compound markedly decreased the hypoxia-induced accumulation of HIF-1α protein dose-dependently. Further analysis revealed that acevaltrate inhibited HIF-1α protein synthesis and promoted degradation of HIF-1α protein, without affecting the expression level of HIF-1α mRNA. Moreover, the phosphorylation levels of mammalian target of rapamycin (mTOR), ribosomal protein S6 kinase (p70S6K), and eIF4E binding protein-1 (4E-BP1) were significantly suppressed by acevaltrate. In addition, acevaltrate promoted apoptosis and inhibited proliferation, which was potentially mediated by suppression of HIF-1α. We also found that acevaltrate administration inhibited tumor growth in mouse xenograft model. Taken together, these results suggested that acevaltrate was a potent inhibitor of HIF-1α and provided a new insight into the mechanisms of acevaltrate against cancers.

CBR1 decreases protein carbonyl levels via the ROS/Akt/CREB pathway to extend lifespan in the cotton bollworm, Helicoverpa armigera.

Reactive oxygen species (ROS) are considered a major cause of ageing and ageing-related diseases through protein carbonylation. Little is known about the molecular mechanisms that confer protection against ROS. Here, we observed that, compared with nondiapause-destined pupae, high protein carbonyl levels are present in the brains of diapause-destined pupae, which is a 'non-ageing' phase in the moth Helicoverpa armigera. Protein carbonyl levels respond to ROS and decrease metabolic activity to induce diapause in order to extend lifespan. However, protein carbonylation in the brains of diapause-destined pupae still occurs at a physiological level compared to young adult brains. We find that ROS activate Akt, and Akt then phosphorylates the transcription factor CREB to facilitate its nuclear import. CREB binds to the promoter of carbonyl reductase 1 (CBR1) and regulates its expression. High CBR1 levels reduce protein carbonyl levels to maintain physiological levels. This is the first report showing that the moth brain can naturally control protein carbonyl levels through a distinct ROS-Akt-CREB-CBR1 pathway to extend lifespan.

COXIV and SIRT2-mediated G6PD deacetylation modulate ROS homeostasis to extend pupal lifespan.

Previous studies have shown that high physiological levels of reactive oxygen species (ROS) in the brain promote pupal diapause, which extends the pupal lifespan. However, the molecular mechanisms of ROS generation are unclear. In this paper, we found that mitochondrial ROS (mtROS) levels in the brains of Helicoverpa armigera diapause-destined pupae (DP) were higher and that the expression of cytochrome oxidase subunit IV (COXIV) was lower than in NP. In addition, downregulating COXIV caused mitochondrial dysfunction which elevated mtROS levels. Protein kinase A (PKA) was downregulated in DP, which led to the downregulated expression of the mitochondrial transcription factor TFAM. Low TFAM activity failed to promote COXIV expression and resulted in the high ROS levels that induced diapause. In addition, low sirtuin 2 expression suppressed glucose-6-phosphate dehydrogenase (G6PD) deacetylation at K382, which led to reduced G6PD activity and low NADPH levels, thereby maintaining high levels of ROS. Two proteins, COXIV and G6PD, thus play key roles in the elevated accumulation of ROS that induce diapause and extend the pupal lifespan.

TGF-ß signaling regulates p-Akt levels via PP2A during diapause entry in the cotton bollworm, Helicoverpa armigera.

Akt, which is a key kinase in the insulin signaling pathway, plays important roles in glucose metabolism, cell proliferation, transcription and cell migration. Our previous studies indicated that low insulin levels and high p-Akt levels are present in diapause-destined individuals. Here, we show that PI3K, which is upstream of Akt, is low in diapause-destined pupal brains but high in p-Akt levels, implying that p-Akt is modified by factors other than the insulin signaling pathway. Protein phosphatase 2A (PP2A), which is a key regulator in the TGF-ß signaling pathway, can directly bind to and dephosphorylate Akt. Low PP2A expression and activity in diapause-destined individuals suggest that a weak Akt dephosphorylation contributes to p-Akt accumulation. In addition, transforming growth factor-ß receptor I (TßRI), which is upstream of PP2A, increases the activity of PP2A and decreases the p-Akt levels. These results show that TGF-ß signaling decreases p-Akt levels by increasing the activity of PP2A. This is the first report showing that TGF-ß signaling negatively regulates the insulin pathway in insect development or diapause.