Crystal structure of a thermophilic GrpE protein: insight into thermosensing function for the DnaK chaperone system.

A homodimeric GrpE protein functions as a nucleotide exchange factor of the eubacterium DnaK molecular chaperone system. The co-chaperone GrpE accelerates ADP dissociation from, and promotes ATP binding to, DnaK, which cooperatively facilitates the DnaK chaperone cycle with another co-chaperone, DnaJ. GrpE characteristically undergoes two-step conformational changes in response to elevation of the environmental temperature. In the first transition at heat-shock temperatures, a fully reversible and functionally deficient structural alteration takes place in GrpE, and then the higher temperatures lead to the irreversible dissociation of the GrpE dimer into monomers as the second transition. GrpE is also thought to be a thermosensor of the DnaK system, since it is the only member of the DnaK system that changes its structure reversibly and loses its function at heat-shock temperatures of various organisms. We here report the crystal structure of GrpE from Thermus thermophilus HB8 (GrpE(Tth)) at 3.23 A resolution. The resolved structure is compared with that of GrpE from mesophilic Escherichia coli (GrpE(Eco)), revealing structural similarities, particularly in the DnaK interaction regions, and structural characteristics for the thermal stability of GrpE(Tth). In addition, the structure analysis raised the possibility that the polypeptide chain in the reported GrpE(Eco) structure was misinterpreted. Comparison of these two GrpE structures combined with the results of limited proteolysis experiments provides insight into the protein dynamics of GrpE(Tth) correlated with the shift of temperature, and also suggests that the localized and partial unfolding at the plausible DnaK interaction sites of GrpE(Tth) causes functional deficiency of nucleotide exchange factor in response to the heat shock

Control of STING Agonistic/Antagonistic Activity Using Amine-Skeleton-Based c-di-GMP Analogues

Stimulator of Interferon Genes (STING) is a type of endoplasmic reticulum (ER)-membrane receptor. STING is activated by a ligand binding, which leads to an enhancement of the immune-system response. Therefore, a STING ligand can be used to regulate the immune system in therapeutic strategies. However, the natural (or native) STING ligand, cyclic-di-nucleotide (CDN), is unsuitable for pharmaceutical use because of its susceptibility to degradation by enzymes and its low cell-membrane permeability. In this study, we designed and synthesized CDN derivatives by replacing the sugar-phosphodiester moiety, which is responsible for various problems of natural CDNs, with an amine skeleton. As a result, we identified novel STING ligands that activate or inhibit STING. The cyclic ligand 7, with a cyclic amine structure containing two guanines, was found to have agonistic activity, whereas the linear ligand 12 showed antagonistic activity. In addition, these synthetic ligands were more chemically stable than the natural ligands

Fluoxetine-induced dematuration of hippocampal neurons and adult cortical neurogenesis in the common marmoset

The selective serotonin reuptake inhibitor fluoxetine (FLX) is widely used to treat depression and anxiety disorders. Chronic FLX treatment reportedly induces cellular responses in the brain, including increased adult hippocampal and cortical neurogenesis and reversal of neuron maturation in the hippocampus, amygdala, and cortex. However, because most previous studies have used rodent models, it remains unclear whether these FLX-induced changes occur in the primate brain. To evaluate the effects of FLX in the primate brain, we used immunohistological methods to assess neurogenesis and the expression of neuronal maturity markers following chronic FLX treatment (3 mg/kg/day for 4 weeks) in adult marmosets (n = 3 per group). We found increased expression of doublecortin and calretinin, markers of immature neurons, in the hippocampal dentate gyrus of FLX-treated marmosets. Further, FLX treatment reduced parvalbumin expression and the number of neurons with perineuronal nets, which indicate mature fast-spiking interneurons, in the hippocampus, but not in the amygdala or cerebral cortex. We also found that FLX treatment increased the generation of cortical interneurons; however, significant up-regulation of adult hippocampal neurogenesis was not observed in FLX-treated marmosets. These results suggest that dematuration of hippocampal neurons and increased cortical neurogenesis may play roles in FLX-induced effects and/or side effects. Our results are consistent with those of previous studies showing hippocampal dematuration and increased cortical neurogenesis in FLX-treated rodents. In contrast, FLX did not affect hippocampal neurogenesis or dematuration of interneurons in the amygdala and cerebral cortex

Development of a low-alpha-emitting {\mu}-PIC for NEWAGE direction-sensitive dark-matter search

NEWAGE is a direction-sensitive dark-matter-search experiment that uses a micro-patterned gaseous detector, or {\mu}-PIC, as the readout. The main background sources are {\alpha}-rays from radioactive contaminants in the {\mu}-PIC. We have therefore developed a low-alpha-emitting {\mu}-PICs and measured its performances. We measured the surface {\alpha}-ray emission rate of the {\mu}-PIC in the Kamioka mine using a surface {\alpha}-ray counter based on a micro TPC.Comment: 6 pages, 4 figure

Comparison of non-invasive, scalp-recorded auditory steady-state responses in humans, rhesus monkeys, and common marmosets

Auditory steady-state responses (ASSRs) are basic neural responses used to probe the ability of auditory circuits to produce synchronous activity to repetitive external stimulation. Reduced ASSR has been observed in patients with schizophrenia, especially at 40 Hz. Although ASSR is a translatable biomarker with a potential both in animal models and patients with schizophrenia, little is known about the features of ASSR in monkeys. Herein, we recorded the ASSR from humans, rhesus monkeys, and marmosets using the same method to directly compare the characteristics of ASSRs among the species. We used auditory trains on a wide range of frequencies to investigate the suitable frequency for ASSRs induction, because monkeys usually use stimulus frequency ranges different from humans for vocalization. We found that monkeys and marmosets also show auditory event-related potentials and phase-locking activity in gamma-frequency trains, although the optimal frequency with the best synchronization differed among these species. These results suggest that the ASSR could be a useful translational, cross-species biomarker to examine the generation of gamma-band synchronization in nonhuman primate models of schizophrenia