Pleiotropic phenotypes of fission yeast defective in ubiquinone-10 production. A study from the abc1Sp (coq8Sp) mutant

We previously constructed two Schizosaccahromyces pombe ubiquinone-10 (or Coenzyme Q10) less mutants, which are either defective for decaprenyl diphosphate synthase or p-hydroxybenzoate polyprenyl diphosphate transferase. To further confirm the roles of ubiquinone in S. pombe, we examined the phenotype of the abc1Sp (coq8Sp) mutant, which is highly speculated to be defective in ubiquinone biosynthesis. We show here that the abc1Sp defective strain did not produce UQ-10 and could not grow on minimal medium. The abc1Sp-deficient strain required supplementation with antioxidants such as cysteine or glutathione to grow on minimal medium. In support of the antioxidant function of ubiquinone, the abc1Sp-deficient strain is sensitive to H2O2 and Cu2+. In addition, expression of the stress inducible ctt1 gene was much induced in the ubiquinone less mutant than wild type. Interestingly, we also found that the abc1-deficient strain as well as other ubiquinone less mutants produced a significant amount of H2S, which suggests that oxidation of sulfide by ubiquinone may be an important pathway for sulfur metabolism in S. pombe. Thus, analysis of the phenotypes of S. pombe ubiquinone less mutants clearly demonstrate that ubiquinone has multiple functions in the cell apart from being an integral component of the electron transfer system.     

A muscle activation model of variable stimulation frequency response and stimulation history, based on positive feedback in calcium dynamics

 Muscle fiber response to a train of variable-frequency pulses includes the potentiation and catch-like effect. For better understanding of these phenomena, we built an activation model with emphasis on the calcium liberation from and re-sequestration into the sarcoplasmic reticulum, including calcium-induced calcium release. The model had two stable equilibrium points in the calcium concentration. Changes from the low to the high equilibrium point could be produced by high-frequency trains of pulses and would account for the potentiation. The model also showed a catch-like effect, as a long-lasting increment of muscle force after the application of a single extra pulse. The increase in force appeared in resting muscle, disappeared when the muscle was potentiated, and reappeared briefly if the stimulation was continued for long periods. Received: 31 January 2000 / Accepted in revised form: 2 August 2000     

Neonatal presentation of adult-onset type II citrullinemia

Adult-onset type II citrullinemia (CTLN2) is characterized by a liver-specific argininosuccinate synthetase deficiency caused by a deficiency of the citrin protein encoded by the SLC25A13 gene. Until now, however, no SLC25A13 mutations have been reported in children with liver diseases. We described three infants who presented as neonates with intrahepatic cholestasis associated with hypermethioninemia or hypergalactosemia detected by neonatal mass screening. DNA analyses of SLC25A13 revealed that one patient was a compound heterozygote for the 851de14 and IVS11+IG-->A mutations and two patients (siblings) were homozygotes for the IVS11+lG-->A mutation. These results suggested that there may be a variety of liver diseases related to CTLN2 in children.     

Role of nociceptin systems in learning and memory

This article summarizes our recent finding that the nociceptin system is involved in the regulation of learning and memory. The nociceptin-knockout mice show greater learning ability in the water maze task, an enhanced latent learning in the water finding task, better memory in the passive avoidance task, and further, larger long-term potentiation in the hippocampal CA1 region than wild-type mice. Nociceptin itself induces an impairment of passive avoidance task in wild-type mice, which is reversed by naloxone benzoylhydrazone (NalBzoH). Thus, the nociceptin system seems to play negative roles in learning and memory, and NalBzoH may act as a potent antagonist for the nociceptin receptor.     

Characterization of human junctophilin subtype genes

Junctophilin (JP) subtypes, namely JP-1, 2, and 3, have been currently identified in excitable cells and constitute a novel family of junctional membrane complex proteins. Our studies have suggested that JPs take part in the formation of junctional membrane complexes by spanning the membrane of the intracellular Ca(2+) store and interacting with the cell-surface membrane. In this report we describe the primary structures, genomic organization, and tissue distribution of human JP subtypes. By cloning and analyzing human genomic DNA segments, the protein-coding sequence interrupted with four introns was defined in each JP gene. The deduced human JP subtypes shared characteristic structural features with their rabbit and mouse counterparts. Genomic mapping demonstrated that JP genes do not cluster on the human genome. RNA blot hybridization indicated that tissue-specific expression patterns of JP genes in human are essentially the same as those in mouse; skeletal muscle contained both JP-1 and JP-2 mRNAs, the heart predominantly expressed JP-2 mRNA, and the brain specifically contained JP-3 mRNA. In the light of this, we propose intramolecular domains of JP subtypes based on the structural and functional characteristics.     

High-performance affinity beads for identifying drug receptors

We have developed a method using novel latex beads for rapid identification of drug receptors using affinity purification. Composed of a glycidylmethacrylate (GMA) and styrene copolymer core with a GMA polymer surface, the beads minimize nonspecific protein binding and maximize purification efficiency. We demonstrated their performance by efficiently purifying FK506-binding protein using FK506-conjugated beads, and found that the amount of material needed was significantly reduced compared with previous methods. Using the latex beads, we identified a redox-related factor, Ref-1, as a target protein of an anti-NF-kappaB drug, E3330, demonstrating the existence of a new class of receptors of anti-NF-kappaB drugs. Our results suggest that the latex beads could provide a tool for the identification and analysis of drug receptors and should therefore be useful in drug development.     

Chronic Powder Diet After Weaning Induces Sleep,Behavioral, Neuroanatomical,and Neurophysiological Changes in Mice

The purpose of this study is to clarify the effects of chronic powder diet feeding on sleep patterns and other physiological/anatomical changes in mice. C57BL/6 male mice were divided into two groups from weaning: a group fed with solid food (SD) and a group fed with powder food (PD), and sleep and physiological and anatomical changes were compared between the groups. PD exhibited less cranial bone structure development and a significant weight gain. Furthermore, these PD mice showed reduced number of neurogenesis in the hippocampus. Sleep analysis showed that PD induced attenuated diurnal sleep/wake rhythm, characterized by increased sleep during active period and decreased sleep during rest period. With food deprivation (FD), PD showed less enhancement of wake/locomotor activity compared to SD, indicating reduced food-seeking behavior during FD. These results suggest that powder feeding in mice results in a cluster of detrimental symptoms caused by abnormal energy metabolism and anatomical/neurological changes.