Glucosamine hydrochloride specifically inhibits COX-2 by preventing COX-2 N-glycosylation and by increasing COX-2 protein turnover in a proteasome-dependent manner

COX-2 and its products, including prostaglandin E(2), are involved in many inflammatory processes. Glucosamine (GS) is an amino monosaccharide and has been widely used for alternative regimen of (osteo) arthritis. However, the mechanism of action of GS on COX-2 expression remains unclear. Here we describe a new action mechanism of glucosamine hydrochloride (GS-HCl) to tackle endogenous and agonist-driven COX-2 at protein level. GS-HCl (but not GS sulfate, N-acetyl GS, or galactosamine HCl) resulted in a shift in the molecular mass of COX-2 from 72-74 to 66-70 kDa and concomitant inhibition of prostaglandin E(2) production in a concentration-dependent manner in interleukin (IL)-1beta-treated A549 human lung epithelial cells. Remarkably, GS-HCl-mediated decrease in COX-2 molecular mass was associated with inhibition of COX-2 N-glycosylation during translation, as assessed by the effect of tunicamycin, the protein N-glycosylation inhibitor, or of cycloheximide, the translation inhibitor, on COX-2 modification. Specifically, the effect of low concentration of GS-HCl (1 mM) or of tunicamycin (0.1 microg/ml) to produce the aglycosylated COX-2 was rescued by the proteasomal inhibitor MG132 but not by the lysosomal or caspase inhibitors. However, the proteasomal inhibitors did not show an effect at 5 mM GS-HCl, which produced the aglycosylated or completely deglycosylated form of COX-2. Notably, GS-HCl (5 mM) also facilitated degradation of the higher molecular species of COX-2 in IL-1beta-treated A549 cells that was retarded by MG132. GS-HCl (5 mM) was also able to decrease the molecular mass of endogenous and IL-1beta- or tumor necrosis factor-alpha-driven COX-2 in different human cell lines, including Hep2 (bronchial) and H292 (laryngeal). However, GS-HCl did not affect COX-1 protein expression. These results demonstrate for the first time that GS-HCl inhibits COX-2 activity by preventing COX-2 co-translational N-glycosylation and by facilitating COX-2 protein turnover during translation in a proteasome-dependent manner.     

Phosphorylation of CKBBP2/CRIF1 by protein kinase CKII promotes cell proliferation

CKII plays a significant role in cell proliferation and cell cycle control. In this report, yeast two-hybrid assay and pull-down assay demonstrate that CKBBP2/CRIF1 associates with the beta subunit of CKII in vitro and in vivo. Recombinant CKBBP2/CRIF1 is phosphorylated in vitro by purified CKII and by CKII inhibitor apigenin-sensitive protein kinase in HEK293 cell extract. Phosphoamino acid analysis and mutational analysis indicate that CKII phosphorylates serine at residue 221 within CKBBP2/CRIF1. Furthermore, serine to alanine mutation at residue 221 abrogates the phosphorylation of CKBBP2/CRIF1 observed in HEK293 cell extract, indicating that CKII is a major kinase that is responsible for phosphorylation of CKBBP2/CRIF1. As compared with the wild-type CKBBP2/CRIF1 or nonphosphorylatable mutant CKBBP2(S221A) (in which the serine-221 is replaced by alanine), overexpression of CKBBP2(S221E) in COS7 cells promotes cell proliferation. Taken together, the present results suggest that CKII may be involved in cell proliferation, at least in part, through the phosphorylation of serine-221 within CKBBP2/CRIF1.     

NF-kappaB inhibition enhances caspase-3 degradation of Akt1 and apoptosis in response to camptothecin

DNA damaging agents, such as camptothecin, and ionizing radiation (IR), can induce both NF-kappaB activation and apoptosis, however, the mechanism of their inter-regulation is not yet clear. In the present study, we discovered that Akt1 is degraded when cells deficient in Ataxia Telangiectasia mutated (ATM) were treated to CPT for apoptosis induction. While CPT-induced NF-kappaB activation could not be detected in ATM-deficient AT5BIVA cells, caspase-3 activation occurred and was even further enhanced by pretreatment with proteasome inhibitor-1 (Pro1), a NF-kappaB inhibitor. In contrast, activation of NF-kappaB but not of caspase-3 by CPT could be found in normal MRC5CV1 cells. NF-kappaB inhibition by Pro1, dominant negative mutant IkappaBalpha (S32/36) or p65 (N250), however, induced the caspase-3 activation in the normal cells, indicating the role of ATM-mediated NF-kappaB activation against cell apoptosis. On the other hand, interestingly, CPT significantly reduced the level of Akt1, this effect further enhanced by Pro1 pretreatment in AT5BIVA cells. In MRC5CV1 cells, however, Akt1 level could be reduced only when CPT and NF-kappaB inhibitors were co-treated to the cells, and this reversed by DEVD-cho treatment, demonstrating the caspase-3-mediated Akt1 degradation. Moreover, although MRC5CV1 cells were much more resistant to CPT compared with AT5BIVA, wortmannin and LY294002 significantly increased the chemosensitivity of MRC5CV1 cells to CPT. Given the accumulating evidences demonstrating Akt as a promising anticancer therapeutic target, all these results suggest that DNA damage induced apoptosis could be regulated by ATM-mediated NF-kappaB activation, and that Akt1 degradation be necessarily required for this apoptotic process.     

The F-actin-microtubule crosslinker Shot is a platform for Krasavietz-mediated translational regulation of midline axon repulsion

Axon extension and guidance require a coordinated assembly of F-actin and microtubules as well as regulated translation. The molecular basis of how the translation of mRNAs encoding guidance proteins could be closely tied to the pace of cytoskeletal assembly is poorly understood. Previous studies have shown that the F-actin-microtubule crosslinker Short stop (Shot) is required for motor and sensory axon extension in the Drosophila embryo. Here, we provide biochemical and genetic evidence that Shot functions with a novel translation inhibitor, Krasavietz (Kra, Exba), to steer longitudinally directed CNS axons away from the midline. Kra binds directly to the C-terminus of Shot, and this interaction is required for the activity of Shot to support midline axon repulsion. shot and kra mutations lead to weak robo-like phenotypes, and synergistically affect midline avoidance of CNS axons. We also show that shot and kra dominantly enhance the frequency of midline crossovers in embryos heterozygous for slit or robo, and that in kra mutant embryos, some Robo-positive axons ectopically cross the midline that normally expresses the repellent Slit. Finally, we demonstrate that Kra also interacts with the translation initiation factor eIF2beta and inhibits translation in vitro. Together, these data suggest that Kra-mediated translational regulation plays important roles in midline axon repulsion and that Shot functions as a direct physical link between translational regulation and cytoskeleton reorganization.     

Syntheses of hydroxy substituted 2-phenyl-naphthalenes as inhibitors of tyrosinase

Oxyresveratrol and resveratrol, with hydroxy substituted trans-stilbene structure, exert potent inhibitory effects on cyclooxygenase, rat liver mitochondrial ATPase activity, and tyrosinase. As the isosteres of oxyresveratrol, a new family of hydroxyl substituted phenyl-naphthalenes were synthesized to show excellent inhibition of mushroom tyrosinase. Compound 10, which is isostere of resveratrol, showed IC50 value of 16.52 microM in mushroom tyrosinase activity. As compared to this, the reference compound, resveratrol, showed IC50 value of 55.61 microM. Compound 4, which is isostere of oxyresveratrol, showed IC50 value of 0.49 microM. Among the other three derivatives, compound 13 showed IC50 value of 0.034 microM.     

Amphiphilic effects of dibucaine HCl on rotational mobility of n-(9-anthroyloxy)stearic acid in neuronal and model membranes

We studied dibucaine's effects on specific locations of n-(9-anthroyloxy)palmitic acid or stearic acid (n-AS) within phospholipids of synaptosomal plasma membrane vesicles isolated from bovine cerebral cortex (SPMV) and model membranes. Giant unilamellar vesicles (GUVs) were prepared with total lipids (SPMVTL) and mixture of several phospholipids (SPMVPL) extracted from SPMV. Dibucaine.HCl increased rotational mobility (increased disordering) of hydrocarbon interior, but it decreased mobility (increased ordering) of membrane interface, in both native and model membranes. The degree of rotational mobility in accordance with the carbon atom numbers of phospholipids comprising neuronal and model membranes was in the order at the 16, 12, 9, 6 and 2 position of aliphatic chain present in phospholipids. The sensitivity of increasing or decreasing effect of rotational mobility of hydrocarbon interior or surface region by dibucaine.HCl differed depending on the neuronal and model membranes in the descending order of SPMV, SPMVPL and SPMVTL.     

The Hypernodulating nts mutation induces jasmonate synthetic pathway in soybean leaves

Symbiotic nitrogen fixation with nitrogen-fixing bacteria in the root nodules is a distinctly beneficial metabolic process in legume plants. Legumes control the nodule number and nodulation zone through a systemic negative regulatory system between shoot and root. Mutation in the soybean NTS gene encoding GmNARK, a CLAVATA1-like serine/threonine receptor-like kinase, causes excessive nodule development called hypernodulation. To examine the effect of nts mutation on the gene expression profile in the leaves, suppression subtractive hybridization was performed with the trifoliate leaves of nts mutant 'SS2-2' and the wild-type (WT) parent Sinpaldalkong2, and 75 EST clones that were highly expressed in the leaves of the SS2-2 mutant were identified. Interestingly, the expression of jasmonate (JA)-responsive genes such as vspA, vspB, and Lox2 were upregulated, whereas that of a salicylate-responsive gene PR1a was suppressed in the SS2-2 mutant. In addition, the level of JA was about two-fold higher in the leaves of the SS2-2 mutant than in those of the WT under natural growth conditions. Moreover, the JA-responsive gene expression persists in the leaves of SS2-2 mutant without rhizobia infection in the roots. Taken together, our results suggest that the nts mutation increases JA synthesis in mature leaves and consequently leads to constitutive expression of JA-responsive genes which is irrelevant to hypernodulation in the root.