Acid-Catalyzed Photosubstitution of 5-Fluoro-1,3-Dimethyluracil with Substituted Benzenes

Abstract

The substantial photosubstitution of 5-fluoro-1,3-dimethyluracil with substituted benzenes is first achieved by the addition of trifluoroacetic acid to the reaction mixture. The presence of protons is essential for the formation of 5-aryl-1,3-dimethyluracils.     

Structural Basis for the Different Stability and Activity between the Cdk5 Complexes with p35 and p39 Activators

Cyclin-dependent kinase 5 (Cdk5) is a brain-specific membrane-bound protein kinase that is activated by binding to the p35 or p39 activator. Previous studies have focused on p35-Cdk5, and little is known regarding p39-Cdk5. The lack of functional understanding of p39-Cdk5 is due, in part, to the labile property of p39-Cdk5, which dissociates and loses kinase activity in nonionic detergent conditions. Here we investigated the structural basis for the instability of p39-Cdk5. p39 and p35 contain N-terminal p10 regions and C-terminal Cdk5 activation domains (AD). Although p35 and p39 show higher homology in the C-terminal AD than the N-terminal region, the difference in stability is derived from the C-terminal AD. Based on the crystal structures of the p25 (p35 C-terminal region including AD)-Cdk5 complex, we simulated the three-dimensional structure of the p39 AD-Cdk5 complex and found differences in the hydrogen bond network between Cdk5 and its activators. Three amino acids of p35, Asp-259, Asn-266, and Ser-270, which are involved in hydrogen bond formation with Cdk5, are changed to Gln, Gln, and Pro in p39. Because these three amino acids in p39 do not participate in hydrogen bond formation, we predicted that the number of hydrogen bonds between p39 and Cdk5 was reduced compared with p35 and Cdk5. Using substitution mutants, we experimentally validated that the difference in the hydrogen bond network contributes to the different properties between Cdk5 and its activators.     

Actin Dynamics Regulated by the Balance of Neuronal Wiskott-Aldrich Syndrome Protein (N-WASP) and Cofilin Activities Determines the Biphasic Response of Glucose-induced Insulin Secretion

Actin dynamics in pancreatic β-cells is involved in insulin secretion. However, the molecular mechanisms of the regulation of actin dynamics by intracellular signals in pancreatic β-cells and its role in phasic insulin secretion are largely unknown. In this study, we elucidate the regulation of actin dynamics by neuronal Wiskott-Aldrich syndrome protein (N-WASP) and cofilin in pancreatic β-cells and demonstrate its role in glucose-induced insulin secretion (GIIS). N-WASP, which promotes actin polymerization through activation of the actin nucleation factor Arp2/3 complex, was found to be activated by glucose stimulation in insulin-secreting clonal pancreatic β-cells (MIN6-K8 β-cells). Introduction of a dominant-negative mutant of N-WASP, which lacks G-actin and Arp2/3 complex-binding region VCA, into MIN6-K8 β-cells or knockdown of N-WASP suppressed GIIS, especially the second phase. We also found that cofilin, which severs F-actin in its dephosphorylated (active) form, is converted to the phosphorylated (inactive) form by glucose stimulation in MIN6-K8 β-cells, thereby promoting F-actin remodeling. In addition, the dominant-negative mutant of cofilin, which inhibits activation of endogenous cofilin, or knockdown of cofilin reduced the second phase of GIIS. However, the first phase of GIIS occurs in the G-actin predominant state, in which cofilin activity predominates over N-WASP activity. Thus, actin dynamics regulated by the balance of N-WASP and cofilin activities determines the biphasic response of GIIS.     

Photoreceptor Proteins Initiate Microglial Activation via Toll-like Receptor 4 in Retinal Degeneration Mediated by All-trans-retinal

Although several genetic and biochemical factors are associated with the pathogenesis of retinal degeneration, it has yet to be determined how these different impairments can cause similar degenerative phenotypes. Here, we report microglial/macrophage activation in both a Stargardt disease and age-related macular degeneration mouse model caused by delayed clearance of all-trans-retinal from the retina, and in a retinitis pigmentosa mouse model with impaired retinal pigment epithelium (RPE) phagocytosis. Mouse microglia displayed RPE cytotoxicity and increased production of inflammatory chemokines/cytokines, Ccl2, Il1b, and Tnf, after coincubation with ligands that activate innate immunity. Notably, phagocytosis of photoreceptor proteins increased the activation of microglia/macrophages and RPE cells isolated from model mice as well as wild-type mice. The mRNA levels of Tlr2 and Tlr4, which can recognize proteins as their ligands, were elevated in mice with retinal degeneration. Bone marrow-derived macrophages from Tlr4-deficient mice did not increase Ccl2 after coincubation with photoreceptor proteins. Tlr4^−/−Abca4^−/−Rdh8^−/− mice displayed milder retinal degenerative phenotypes than Abca4^−/−Rdh8^−/− mice. Additionally, inactivation of microglia/macrophages by pharmacological approaches attenuated mouse retinal degeneration. This study demonstrates an important contribution of TLR4-mediated microglial activation by endogenous photoreceptor proteins in retinal inflammation that aggravates retinal cell death. This pathway is likely to represent an underlying common pathology in degenerative retinal disorders.     

Optically Detected Structural Change in the N-Terminal Region of?the?Voltage-Sensor Domain

The voltage-sensor domain (VSD) is a functional module that undergoes structural transitions in response to membrane potential changes and regulates its effectors, thereby playing a crucial role in amplifying and decoding membrane electrical signals. Ion-conductive pore and phosphoinositide phosphatase are the downstream effectors of voltage-gated channels and the voltage-sensing phosphatase, respectively. It is known that upon transition, the VSD generally acts on the region C-terminal to S4. However, whether the VSD also induces any structural changes in the N-terminal region of S1 has not been addressed directly. Here, we report the existence of such an N-terminal effect. We used two distinct optical reporters—one based on the Förster resonance energy transfer between a pair of fluorescent proteins, and the other based on fluorophore-labeled HaloTag—and studied the behavior of these reporters placed at the N-terminal end of the monomeric VSD derived from voltage-sensing phosphatase. We found that both of these reporters were affected by the VSD transition, generating voltage-dependent fluorescence readouts. We also observed that whereas the voltage dependencies of the N- and C-terminal effects appear to be tightly coupled, the local structural rearrangements reflect the way in which the VSD is loaded, demonstrating the flexible nature of the VSD.     

Synthesis of Isoprenyl Chalcone “Sophoradin”

Nicotine has been found an effective photosensitizer for DDT. At DDT: nicotine (1:5), DDT along with its formed degradation products DDD, DDE and DBP disappeared within 18 and 60 days under UV and sunlight respectively. Because of persistence, nicotine proved a superior photosensitizer to N,N′-diethylaniline. In DDT emulsifiable concentrates it led to high alkalinity but no DDT degradation up to 60 days at 20~25°C. 0.1 and 0.5% DDT emulsions from these formulations showed no adverse effect on Daucus carrota, Vicia faba, Brassica oleracea var. botrytis, and Dahlia sp., but showed mild to severe phytotoxicity against Pisum sativum and Cicer arietinum; caused by high concentration of nicotine. On Clerodendrum sp. in sunlight, these formulations showed over 20% faster DDT loss between 3~15 days of application. DDT-nicotine mixtures showed no synergism against Tribolium castaneum Herbst.     

Biotransformation of 3-(3′,5′ -Dichlorophenyl)-5,5-dimethyl oxazolidine-2,4-dione

Using 3-(3′,5′-dichlorophenyl)-5,5-dimethyloxazolidine-2,4-dione labeled with ¹⁴C or ³H, absorption, excretion, and tissue distribution in male Wistar rats were studied, and metabolites excreted were identified. At the dosage rates of 100, 300, 1000 and 3000 mg/kg, the maximum excretion of orally administered radioactivity occurred within 24 hr. Increase in the dosage rate was paralleled by decrease in the proportion of urinary elimination. Essentially all the radioactivity was excreted in 2 weeks. DDOD level was generally low in most tissues. Adipose tissue contained higher radioactivity compared with others. Most of the urinary metabolites identified were characterized by hydroxylation at the 4′ position of the benzene ring moiety, and hydrolytic or oxidative modification of the oxazolidine ring portion.