Hidenori Nakajima

Spliceostatin A targets SF3b and inhibits both splicing and nuclear retention of pre-mRNA

The removal of intervening sequences from transcripts is catalyzed by the spliceosome, a multicomponent complex that assembles on the newly synthesized pre-mRNA. Pre-mRNA translation in the cytoplasm leads to the generation of aberrant proteins that are potentially harmful. Therefore, tight control to prevent undesired pre-mRNA export from the nucleus and its subsequent translation is an essential requirement for reliable gene expression. Here, we show that the natural product FR901464 (1) and its methylated derivative, spliceostatin A (2), inhibit in vitro splicing and promote pre-mRNA accumulation by binding to SF3b, a subcomplex of the U2 small nuclear ribonucleoprotein in the spliceosome. Importantly, treatment of cells with these compounds resulted in leakage of pre-mRNA to the cytoplasm, where it was translated. Knockdown of SF3b by small interfering RNA induced phenotypes similar to those seen with spliceostatin A treatment. Thus, the inhibition of pre-mRNA splicing during early steps involving SF3b allows unspliced mRNA leakage and translation.

Inhibition of hypoxia-induced angiogenesis by FK228, a specific histone deacetylase inhibitor, via suppression of HIF-1α activity

Hypoxia is generally detected in central regions of solid tumors and regulates a variety of transcription factors including hypoxia-inducible factor-1 (HIF-1). HIF-1 plays a pivotal role in cellular response to low oxygen concentration, such as angiogenesis in tumor. Here, we found that a histone deacetylase (HDAC) inhibitor, FK228, inhibits the induction and activity of HIF-1 in response to hypoxia. Moreover, FK228 significantly suppressed the induction of vascular endothelial growth factor (VEGF) under hypoxia, suggesting that FK228 contributes to the inhibition of tumor angiogenesis. In Lewis lung carcinoma model, FK228 also blocked angiogenesis induced by hypoxia. These results suggest that FK228 can downregulate hypoxia-responsive angiogenesis through suppression of HIF-1alpha activity.

Renoprotective properties of pirfenidone in subtotally nephrectomized rats.

Renal fibrosis is the final common pathway of chronic kidney disease, and its progression predicts the degree of renal dysfunction. We investigated the renoprotective properties of pirfenidone in a remnant kidney model of chronic renal failure to determine its pharmacological potency compared to enalapril. Five-sixths nephrectomized rats were fed diet containing pirfenidone (approximately 700mg/kg/day) for 8weeks. Pirfenidone steadily inhibited the progression of proteinuria, but not to a significant degree. Pirfenidone prevented the elevation of plasma creatinine and blood urea nitrogen. At the end of the experiment, pirfenidone had reduced systolic blood pressure by means of its renoprotective effect. In a histological study, pirfenidone improved interstitial fibrosis in the renal cortex. These effects were supported by the suppression of the expression of TGF-beta and fibronectin in the mRNA of the kidney. In contrast, pirfenidone had little effect on the expression of alpha-smooth muscle actin, which is one of the proteins responsible for epithelial-mesenchymal transition. This property was confirmed by the TGF-beta-induced transdifferentiation observed in cultured normal rat kidney tubular epithelial NRK52E cells. These results suggest that pirfenidone improves the progression of chronic renal failure via its antifibrotic action, although pirfenidone has less effective TGF-beta-induced epithelial to mesenchymal transdifferentiation.

FR177391, a new anti-hyperlipidemic agent from Serratia. I. Taxonomy, fermentation, isolation, physico-chemical properties, structure elucidation and biological activities.

In the course of screening for a new anti-hyperlipidemic agent from microbial products, we found that FR177391, produced by Serratia liquefaciens No. 1821, alleviated the decrease in lipid droplet formation in differentiated 3T3-L1 adipocyte cells, induced by the addition of tumor necrosis factor-α. Structural elucidation by spectroscopic methods and X-ray crystallographic analysis of its propylamide derivative revealed that FR177391 was a chlorinated macrocyclic lactone.

Structure of a high-resolution crystal form of human triosephosphate isomerase: improvement of crystals using the gel-tube method

Crystals of human triosephosphate isomerase with two crystal morphologies were obtained using the normal vapour-diffusion technique with identical crystallization conditions. One had a disordered plate shape and the crystals were hollow (crystal form 1). As a result, this form was very fragile, diffracted to 2.8 A resolution and had similar crystallographic parameters to those of the structure 1hti in the Protein Data Bank. The other had a fine needle shape (crystal form 2) and was formed more abundantly than crystal form 1, but was unsuitable for structure analysis. Since the normal vapour-diffusion method could not control the crystal morphology, gel-tube methods, both on earth and under microgravity, were applied for crystallization in order to control and improve the crystal quality. Whereas crystal form 1 was only slightly improved using this method, crystal form 2 was greatly improved and diffracted to 2.2 A resolution. Crystal form 2 contained a homodimer in the asymmetric unit, which was biologically essential. Its overall structure was similar to that of 1hti except for the flexible loop, which was located at the active centre Lys13.

The novel gluconeogenesis inhibitor FR225654 that originates from Phoma sp. no. 00144. II. Biological activities.

The novel gluconeogenesis inhibitor FR225654, isolated from the culture broth of Phoma sp. No. 00144, has an unique structure that consists of a highly oxygenated trans-decalin ring and a β-keto-enol, with a characteristic side chain. This compound selectively inhibited gluconeogenesis of rat primary hepatocytes and had hypoglycemic effects in several in vivo mouse models.

FR177391, a new anti-hyperlipidemic agent from Serratia. IV. Target identification and validation by chemical genetic approaches.

Natural products with distinct biological activities are very promising molecular probes to dissect the novel pathways of biology. FR177391, a product of bacteria, was obtained as a natural compound possessing anti-hyperlipidemic effects. FR177391 enhances differentiation of mouse 3T3-L1 fibroblasts to adipocytes and reduces the circulating levels of triglyceride in C57BL/KsJ-db/db mice, a obese non-insulin-dependent diabetes mellitus animal model, although its mechanism of actions remained to be unknown. We report here that the target protein for FR177391 was identified to be protein phosphatase 2A (PP2A) by employing the method of affinity chromatography. FR177391 potently inhibited PP2A activity at nano molar concentration, and shared its binding pocket with a phosphatase inhibitor, okadaic acid. In addition to the phenotypic alterations, the enhancement for phosphorylation of extracellular signal-regulated kinase (ERK) protein was observed in the FR177391-treated 3T3-L1 cells. These results suggest that prolonged activation of ERK protein due to inhibition of its dephosphorylation by PP2A plays an important role in adipocyte maturation and regulation of the blood revels of lipids.

The Novel Gluconeogenesis Inhibitor FR225654 that Originates from Phoma sp. No. 00144 : I. Taxonomy, Fermentation, Isolation and Physico-chemical Properties

FR225654, a novel gluconeogenesis inhibitor, was isolated from the culture broth of Phoma sp. No. 00144 and purified by adsorptive resin and reverse-phase column chromatography. This compound is a potent inhibitor of gluconeogenesis and is a promising candidate of anti-diabetic agent.

FR177391, a new anti-hyperlipidemic agent from Serratia. III. Microbial conversion of FR177391 and synthesis of FR177391 derivatives for its target protein screening by chemical genetic approaches.

FR177391 produced by Serratia liquefaciens No. 1821 enhances differentiation of mouse 3T3-L1 fibroblasts to adipocytes and reduces the circulating levels of triglyceride in C57BL/KsJ-db/bd mice, an obese non-insulin-dependent diabetes mellitus animal model, although its mechanism of actions remained to be unknown. Its active derivative, 20-hydroxy FR177391, and its inactive derivative, 3-hydroxy FR177391 were produced by microbial conversion of FR177391, and biotin-labeled FR177391 was synthesized from 20-hydroxy FR177391 as an active affinity ligand to identify target molecules of FR177391 by chemical genetic approaches.

The Novel Gluconeogenesis Inhibitor FR225654 that Originates from Phoma sp. No. 00144 : III. Structure Determination

A novel gluconeogenesis inhibitor, FR225654 was isolated from the culture broth of Phoma sp. No. 00144. Spectroscopic analysis concluded that FR225654 has a highly oxygenated trans-decalin ring and β-keto-enol in its main part, and has a characteristic side chain possessing a conjugated carboxylic acid and tri-substituted olefin.