LKR/SDH Plays Important Roles throughout the Tick Life Cycle Including a Long Starvation Period

BACKGROUND:Lysine-ketoglutarate reductase/saccharopine dehydrogenase (LKR/SDH) is a bifunctional enzyme catalyzing the first two steps of lysine catabolism in plants and mammals. However, to date, the properties of the lysine degradation pathway and biological functions of LKR/SDH have been very little described in arthropods such as ticks. METHODOLOGY/PRINCIPAL FINDINGS:We isolated and characterized the gene encoding lysine-ketoglutarate reductase (LKR, EC 1.5.1.8) and saccharopine dehydrogenase (SDH, EC 1.5.1.9) from a tick, Haemaphysalis longicornis, cDNA library that encodes a bifunctional polypeptide bearing domains similar to the plant and mammalian LKR/SDH enzymes. Expression of LKR/SDH was detected in all developmental stages, indicating an important role throughout the tick life cycle, including a long period of starvation after detachment from the host. The LKR/SDH mRNA transcripts were more abundant in unfed and starved ticks than in fed and engorged ticks, suggesting that tick LKR/SDH are important for the starved tick. Gene silencing of LKR/SDH by RNAi indicated that the tick LKR/SDH plays an integral role in the osmotic regulation of water balance and development of eggs in ovary of engorged females. CONCLUSIONS/SIGNIFICANCE:Transcription analysis and gene silencing of LKR/SDH indicated that tick LKR/SDH enzyme plays not only important roles in egg production, reproduction and development of the tick, but also in carbon, nitrogen and water balance, crucial physiological processes for the survival of ticks. This is the first report on the role of LKR/SDH in osmotic regulation in animals including vertebrate and arthropods

Yokukansan Inhibits Neuronal Death during ER Stress by Regulating the Unfolded Protein Response

Recently, several studies have reported Yokukansan (Tsumura TJ-54), a traditional Japanese medicine, as a potential new drug for the treatment of Alzheimer's disease (AD). Endoplasmic reticulum (ER) stress is known to play an important role in the pathogenesis of AD, particularly in neuronal death. Therefore, we examined the effect of Yokukansan on ER stress-induced neurotoxicity and on familial AD-linked presenilin-1 mutation-associated cell death.We employed the WST-1 assay and monitored morphological changes to evaluate cell viability following Yokukansan treatment or treatment with its components. Western blotting and PCR were used to observe the expression levels of GRP78/BiP, caspase-4 and C/EBP homologous protein.Yokukansan inhibited neuronal death during ER stress, with Cnidii Rhizoma (Senkyu), a component of Yokukansan, being particularly effective. We also showed that Yokukansan and Senkyu affect the unfolded protein response following ER stress and that these drugs inhibit the activation of caspase-4, resulting in the inhibition of ER stress-induced neuronal death. Furthermore, we found that the protective effect of Yokukansan and Senkyu against ER stress could be attributed to the ferulic acid content of these two drugs.Our results indicate that Yokukansan, Senkyu and ferulic acid are protective against ER stress-induced neuronal cell death and may provide a possible new treatment for AD