Tyrosine hydroxylase conditional KO mice reveal peripheral tissue-dependent differences in dopamine biosynthetic pathways.

Dopamine (DA) exerts well-known functions in the brain as a neurotransmitter. In addition, it plays important physiological roles in peripheral organs, but it is largely unknown how and where peripheral DA is synthesized and regulated. Catecholamines in peripheral tissues are either produced within the tissue itself and/or derived from sympathetic neurons, which release neurotransmitters for uptake by peripheral tissues. To evaluate DA-producing ability of each peripheral tissue, we generated conditional KO mice (cKO mice) in which the tyrosine hydroxylase (TH) gene is ablated in the sympathoadrenal system, thus eliminating sympathetic neurons as a DA source. We then examined the alterations in the noradrenaline (NA), DA, and 3,4-dihydroxyphenylalanine (DOPA) contents in peripheral organs and performed immunohistochemical analyses of TH-expressing cells. In the heart and pancreas of cKO mice, both the TH protein and NA levels were significantly decreased, and the DA contents were decreased in parallel with NA contents, indicating that the DA supply originated from sympathetic neurons. We found TH-immunoreactive cells in the stomach and lung, where the TH protein showed a decreasing trend, but the DA levels were not decreased in cKO mice. Moreover, we found a significant correlation between the DA content in the kidney and the plasma DOPA concentration, suggesting that the kidney takes up DOPA from blood to make DA. The aforementioned data unravel differences in the DA biosynthetic pathway among tissues and support the role of sympathetic neurons as a DA supplier.

Improving the Solubility of Artificial Ligands of Streptavidin to Enable More Practical Reversible Switching of Protein Localization in Cells.

Chemical inducers that can control target-protein localization in living cells are powerful tools to investigate dynamic biological systems. We recently reported the retention using selective hook or "RUSH" system for reversible localization change of proteins of interest by addition/washout of small-molecule artificial ligands of streptavidin (ALiS). However, the utility of previously developed ALiS was restricted by limited solubility in water. Here, we overcame this problem by X-ray crystal structure-guided design of a more soluble ALiS derivative (ALiS-3), which retains sufficient streptavidin-binding affinity for use in the RUSH system. The ALiS-3-streptavidin interaction was characterized in detail. ALiS-3 is a convenient and effective tool for dynamic control of α-mannosidase II localization between ER and Golgi in living cells.

Development of a potent and selective FLT3 kinase inhibitor by systematic expansion of a non-selective fragment-screening hit.

A non-selective inhibitor (1) of FMS-like tyrosine kinase-3 (FLT3) was identified by fragment screening and systematically modified to afford a potent and selective inhibitor 26. We confirmed that 26 inhibited the growth of FLT-3-activated human acute myeloid leukemia cell line MV4-11. Our design strategy enabled rapid development of a novel type of FLT3 inhibitor from the hit fragment in the absence of target-structural information.

Artificial Ligands of Streptavidin (ALiS): Discovery, Characterization, and Application for Reversible Control of Intracellular Protein Transport.

Artificial ligands of streptavidin (ALiS) with association constants of ∼10(6) M(-1) were discovered by high-throughput screening of our chemical library, and their binding characteristics, including X-ray crystal structure of the streptavidin complex, were determined. Unlike biotin and its derivatives, ALiS exhibits fast dissociation kinetics and excellent cell permeability. The streptavidin-ALiS system provides a novel, practical compound-dependent methodology for repeated reversible cycling of protein localization between intracellular organella.

Supramolecular Ligands for Histone Tails by Employing a Multivalent Display of Trisulfonated Calix[4]arenes.

Post-translational modification of histone tails plays critical roles in gene regulation. Thus, molecules recognizing histone tails and controlling their epigenetic modification are desirable as biochemical tools to elucidate regulatory mechanisms. There are, however, only a few synthetic ligands that bind to histone tails with substantial affinity. We report CA2 and CA3, which exhibited sub-micromolar affinity to histone tails (especially tails with a trimethylated lysine). Multivalent display of trisulfonated calix[4]arene was important for strong binding. CA2 was applicable not only to synthetic tail peptides but also to endogenous histone proteins, and was successfully used to pull-down endogenous histones from nuclear extract. These findings indicate the utility of these supramolecular ligands as biochemical tools for studying chromatin regulator protein and as a targeting motif in ligand-directed catalysis to control epigenetic modifications.

Design and synthesis of an in vivo-efficacious PIM3 kinase inhibitor as a candidate anti-pancreatic cancer agent.

Serine/threonine kinase PIM3 is a potential therapeutic target for pancreatic cancer. Here, we describe the evolution of our previous PIM1 inhibitor 1 into PIM3 inhibitor 11 guided by use of the crystal structure of PIM1 as a surrogate to provide a basis for rational modification. Compound 11 potently inhibits PIM3 kinase activity, as well as growth of several pancreatic cancer cell lines. In a mouse xenograft model, 11 inhibited growth of human pancreatic cancer cell line PCI66 with negligible body weight loss. Thus, 11 appears to be a promising lead compound for further optimization to develop new anti-pancreatic cancer agents.

Production of marmoset eggs and embryos from xenotransplanted ovary tissues.

The common marmoset (Callithrix jacchus) has attracted attention as a valuable primate model for the analysis of human diseases. Despite the potential for primate genetic modification, however, its widespread lab usage has been limited due to the requirement for a large number of eggs. To make up for traditional oocyte retrieval methods such as hormone administration and surgical techniques, we carried out an alternative approach by utilizing ovarian tissue from deceased marmosets that had been disposed of. This ovarian tissue contains oocytes and can be used as a valuable source of follicles and oocytes. In this approach, the ovarian tissue sections were transplanted under the renal capsules of immunodeficient mice first. Subsequent steps consist of development of follicles by hormone administrations, induction of oocyte maturation and fertilization, and culture of the embryo. This method was first established with rat ovaries, then applied to marmoset ovaries, ultimately resulting in the successful acquisition of the late-stage marmoset embryos. This approach has the potential to contribute to advancements in genetic modification research and disease modeling through the use of primate models, promoting biotechnology with non-human primates and the 3Rs principle in animal experimentation.

Development of NIR fluorescent dyes based on Si-rhodamine for in vivo imaging.

We have developed a series of novel near-infrared (NIR) wavelength-excitable fluorescent dyes, SiR-NIRs, by modifying the Si-rhodamine scaffold to obtain emission in the range suitable for in vivo imaging. Among them, SiR680 and SiR700 showed sufficiently high quantum efficiency in aqueous media. Both antibody-bound and free dye exhibited high tolerance to photobleaching in aqueous solution. Subcutaneous xenograft tumors were successfully visualized in a mouse tumor model using SiR700-labeled anti-tenascin-C (TN-C) antibody, SiR700-RCB1. SiR-NIRs are expected to be useful as labeling agents for in vivo imaging studies including multicolor imaging, and also as scaffolds for NIR fluorescence probes.

D1 Receptor Mediated Dopaminergic Neurotransmission Facilitates Remote Memory of Contextual Fear Conditioning.

Dopaminergic neurotransmission via dopamine D1 receptors (D1Rs) is considered to play an important role not only in reward-based learning but also in aversive learning. The contextual and auditory cued fear conditioning tests involve the processing of classical fear conditioning and evaluates aversive learning memory. It is possible to evaluate aversive learning memory in two different types of neural transmission circuits. In addition, when evaluating the role of dopaminergic neurotransmission via D1R, to avoid the effects in D1R-mediated neural circuitry alterations during development, it is important to examine using mice who D1R expression in the mature stage is suppressed. Herein, we investigated the role of dopaminergic neurotransmission via D1Rs in aversive memory formation in contextual and auditory cued fear conditioning tests using D1R knockdown (KD) mice, in which the expression of D1Rs could be conditionally and reversibly controlled with doxycycline (Dox) treatment. For aversive memory, we examined memory formation using recent memory 1 day after conditioning, and remote memory 4 weeks after conditioning. Furthermore, immunostaining of the brain tissues of D1RKD mice was performed after aversive footshock stimulation to investigate the distribution of activated c-Fos, an immediate-early gene, in the hippocampus (CA1, CA3, dentate gyrus), striatum, amygdala, and prefrontal cortex during aversive memory formation. After aversive footshock stimulation, immunoblotting was performed using hippocampal, striatal, and amygdalar samples from D1RKD mice to investigate the increase in the amount of c-Fos and phosphorylated SNAP-25 at Ser187 residue. When D1R expression was suppressed using Dox, behavioral experiments revealed impaired contextual fear learning in remote aversion memory following footshock stimulation. Furthermore, expression analysis showed a slight increase in the post-stimulation amount of c-Fos in the hippocampus and striatum, and a significant increase in the amount of phosphorylated SNAP-25 in the hippocampus, striatum, and prefrontal cortex before and after stimulation. These findings indicate that deficiency in D1R-mediated dopaminergic neurotransmission is an important factor in impairing contextual fear memory formation for remote memory.

Cerebrocortical activation following unilateral labyrinthectomy in mice characterized by whole-brain clearing: implications for sensory reweighting.

Posture and gait are maintained by sensory inputs from the vestibular, visual, and somatosensory systems and motor outputs. Upon vestibular damage, the visual and/or somatosensory systems functionally substitute by cortical mechanisms called "sensory reweighting". We investigated the cerebrocortical mechanisms underlying sensory reweighting after unilateral labyrinthectomy (UL) in mice. Arc-dVenus transgenic mice, in which the gene encoding the fluorescent protein dVenus is transcribed under the control of the promoter of the immediate early gene Arc, were used in combination with whole-brain three-dimensional (3D) imaging. Performance on the rotarod was measured as a behavioral correlate of sensory reweighting. Following left UL, all mice showed the head roll-tilt until UL10, indicating the vestibular periphery damage. The rotarod performance worsened in the UL mice from UL1 to UL3, which rapidly recovered. Whole-brain 3D imaging revealed that the number of activated neurons in S1, but not in V1, in UL7 was higher than that in sham-treated mice. At UL7, medial prefrontal cortex (mPFC) and agranular insular cortex (AIC) activation was also observed. Therefore, sensory reweighting to the somatosensory system could compensate for vestibular dysfunction following UL; further, mPFC and AIC contribute to the integration of sensory and motor functions to restore balance.

Virtual screening and further development of novel ALK inhibitors.

Anaplastic lymphoma kinase (ALK) has been in the spotlight in recent years as a promising new target for therapy of non-small-cell lung cancer (NSCLC). Since the identification of the echinoderm microtubule-associated protein-like 4 (EML4)-ALK fusion gene in some NSCLC patients was reported in 2007, various research groups have been seeking ALK inhibitors. Above all, crizotinib (PF-02341066) has been under clinical trial, and its therapeutic efficacy of inhibiting ALK in NSCLC has been reported. Among anticancer drugs, drug resistance appears frequently necessitating various kinds of inhibitors. We identified novel ALK inhibitors by virtual screening from the public chemical library collected by the Chemical Biology Research Initiative (CBRI) at the University of Tokyo, and inhibitors that are more potent were developed.

Identification of novel ASK1 inhibitors using virtual screening.

Apoptosis signal-regulating kinase 1 (ASK1, also called MAP3K5) is a mitogen-activated protein kinase kinase kinase (MAP3K) that plays important roles in stress-induced cell death and inflammation, and is expected as a new therapeutic target for cancer, cardiovascular diseases, and neurodegenerative diseases. We identified novel ASK1 inhibitors by virtual screening from the public chemical library collected by Chemical Biology Research Initiative (CBRI) at the University of Tokyo.

[Dopamine and NMDA Receptors in Basal Ganglia Circuits and Their Roles regarding Motor Control and Learning].

Dopamine (DA) plays an important role in the basal ganglia (BG) for motor control, and DA deficiency as seen in Parkinson's disease, causes movement disorders. DA activates the direct pathway nerve via the D1 receptor (D1R) and inhibits the indirect pathway nerve via the D2 receptor (D2R). To understand the role of DA signaling, we review recent studies of the roles of D1R and D2R with respect to motor control, neural activity and memory learning using genetically engineered mice, and investigate their involvement in the BG oscillation phenomenon.

Neurotransmission through dopamine D1 receptors is required for aversive memory formation and Arc activation in the cerebral cortex.

Dopaminergic neurotransmission is considered to play an important role not only in reward-based learning, but also in aversive learning. Here, we investigated the role of dopaminergic neurotransmission via dopamine D1 receptors (D1Rs) in aversive memory formation in a passive avoidance test using D1R knockdown (KD) mice, in which the expression of D1Rs can conditionally and reversibly be controlled by doxycycline (Dox) treatment. We also performed whole-brain imaging after aversive footshock stimulation in activity-regulated cytoskeleton protein (Arc)-dVenus D1RKD mice, which were crossbred from Arc-dVenus transgenic mice and D1RKD mice, to examine the distribution of Arc-controlled dVenus expression in the hippocampus and cerebral cortex during aversive memory formation. Knockdown of D1R expression following Dox treatment resulted in impaired performance in the passive avoidance test and was associated with a decrease in dVenus expression in the cerebral cortex (visual, somatosensory, and motor cortices), but not the hippocampus, compared with control mice without Dox treatment. These findings indicate that D1R-mediated dopaminergic transmission is critical for aversive memory formation, specifically by influencing Arc expression in the cerebral cortex.

Gliotoxin suppresses NF-κB activation by selectively inhibiting linear ubiquitin chain assembly complex (LUBAC).

A linear ubiquitin chain, which consists of ubiquitin molecules linked via their N- and C-termini, is formed by a linear ubiquitin chain assembly complex (LUBAC) composed of HOIP, HOIL-1L, and SHARPIN, and conjugation of a linear ubiquitin chain on the NF-κB essential modulator (NEMO) is deeply involved in NF-κB activation induced by various signals. Since abnormal activation of NF-κB is associated with inflammatory disease and malignancy, we searched for an inhibitor of LUBAC by high-throughput screening (HTS) with a Tb(3+)-fluorescein FRET system. As a result, we found that the fungal metabolite gliotoxin inhibits LUBAC selectively by binding to the RING-IBR-RING domain of HOIP, the catalytic center of LUBAC. Gliotoxin has been well-known as an inhibitor of NF-κB activation, though its action mechanism has remained elusive. Here, we show that gliotoxin inhibits signal-induced NF-κB activation by selectively inhibiting LUBAC-mediated linear ubiquitin chain formation.

Rational evolution of a novel type of potent and selective proviral integration site in Moloney murine leukemia virus kinase 1 (PIM1) inhibitor from a screening-hit compound.

Serine/threonine kinase PIM1 is an emerging therapeutic target for hematopoietic and prostate cancer therapy. To develop a novel PIM1 inhibitor, we focused on 1, a metabolically labile, nonselective kinase inhibitor discovered in our previous screening study. We adopted a rational optimization strategy based mainly on structural information for the PIM1-1 complex to improve the potency and selectivity. This approach afforded the potent and metabolically stable PIM1-selective inhibitor 14, which shows only a marginal increase in molecular weight compared with 1 but has a significantly decreased cLogP. The validity of our design concept was confirmed by X-ray structure analysis. In a cellular study, 14 potently inhibited the growth of human leukemia cell line MV4-11 but had a negligible effect on the growth of WI-38 (surrogate for general toxicity). These results demonstrate the effectiveness of our design strategy for evolving the screening-hit compound 1 into a novel type of PIM1 inhibitor, 14.

Blockade of inflammatory responses by a small-molecule inhibitor of the Rac activator DOCK2.

Tissue infiltration of activated lymphocytes is a hallmark of transplant rejection and organ-specific autoimmune diseases. Migration and activation of lymphocytes depend on DOCK2, an atypical Rac activator predominantly expressed in hematopoietic cells. Although DOCK2 does not contain Dbl homology domain typically found in guanine nucleotide exchange factors, DOCK2 mediates the GTP-GDP exchange reaction for Rac through its DHR-2 domain. Here, we have identified 4-[3'-(2″-chlorophenyl)-2'-propen-1'-ylidene]-1-phenyl-3,5-pyrazolidinedione (CPYPP) as a small-molecule inhibitor of DOCK2. CPYPP bound to DOCK2 DHR-2 domain in a reversible manner and inhibited its catalytic activity in vitro. When lymphocytes were treated with CPYPP, both chemokine receptor- and antigen receptor-mediated Rac activation were blocked, resulting in marked reduction of chemotactic response and T cell activation. These results provide a rational of and a chemical scaffold for development of the DOCK2-targeting immunosuppressant.