Trachyspic acid 19-butyl ester, a new inhibitor of Plk1 polo box domain-dependent recognition from uncharacterized fungus RKGS-F2684

Abstract

Polo-like kinase 1 (Plk1) is a serine-threonine protein kinase that possesses many essential functions during mitosis and is one of the key regulators of mitotic cell division. 1,2 Although it has a catalytic domain of protein kinase at its N-terminus, it possesses a phosphopeptide binding domain named polo box domain (PBD) at its C-terminus. 3,4 PBD binds to other protein in a phosphorylation dependent manner. PBD-dependent binding not only is important for the subcellular localization, but is also necessary for the targeting of Plk1 to specific substrates. 3 Plk1 is frequently overexpressed in many cancers and inhibition of Plk1 by antisence oligonucleotides or small interfering RNA (siRNA) is highly effective in inhibiting cancer cell proliferation. The reduction of Plk1 is also shown to induce tumor regression in mouse xenograft model. 5 Thus, Plk1 is considered to be an attractive target for the treatment of human cancers. [6][7][8] Several inhibitors of its catalytic activity are developed and some of them have proceeded to clinical trials. 9,10 We established a screening system for the inhibitors of PBD-dependent binding. 11 In this system, the open reading frame of a green fluorescent protein (GFP) is fused to PBD and expressed in bacteria. Target phosphopeptides for the PBD binding sequence are chemically synthesized and bound covalently to maleimide-activated 96-well plates. The binding of GFP-PBD to the phosphopeptides was quantitated through spectrofluorometry. Using this system, we have obtained purpurogallin, a benzotropolone-containing natural compound from nutgalls as an inhibitor of PBD. 11 Several other inhibitors of PBD are also identified by other groups but currently no clinical trials have been reported. 12 We have developed a structure based compound isolation technique named NPPlot (Natural Products Plot), where secondary metabolites from microorganisms are analyzed by their MW and retention time on DAD-LC/MS. 13 These analytical data are accumulated and used for the spectral database establishment. Using the method, we have isolated several new metabolites with unprecedented skeletons from microbial sources, such as verticilactam, 14 spirotoamides, 15 pyrrolizilactone 16 and recently opantimycin A. 17 In the present study, we combined our high-throughput screening system for PBD inhibitors and the methodology of the fractionation of microbial metabolites with spectral database. Using these techniques, a new 5,5-spiroacetal metabolite, trachyspic acid 19-butyl ester (1) together with a known metabolite trachyspic acid (2) 18 with potent PBD inhibitory activity was isolated from uncharacterized fungus RKGS-F2684 (Figure 1). We report here the isolation, structure and biological activity of 1.In the course of screening from about 3000 microbial extracts using our high-throughput screening system, we found that the extracts from fungal strain RKGS-F2684, which was isolated from a soil sample collected in Kumamoto, Japan in 1995, contained potent inhibitory activity. An ethyl acetate sol...

Recent Progress in Development of Polo-Like Kinase 1 Inhibitors: Efforts So Far

“…It also showed an excellent specificity profile for Plk1 (Ki=0.012±0.001 µM) over other two kinases, Plk2 (Ki=5.5±0.7 µM) and Plk3 (Ki=3.7±0.2 µM). This study provided an excellent opportunity to design Plk1 inhibitors targeting both functional and enzymatic domains to overcome the specificity of ATP-competitive kinase inhibitors 84. Chen et al also reported 5-(ethylsulfonyl)-2-(4-fluorophenyl)-4-(phenylsulfonyl) oxazole (T521)…”

Targeting Heparanase in Cancer: Inhibition by Synthetic, Chemically Modified, and Natural Compounds

“…Polo-like kinase 1 (Plk1) is a serine-threonine protein kinase involved in the regulation of mitotic cell division and often overexpressed in various malignancies. The C terminus of Plk1 has polo-box domain (PBD), which is essential for interaction with other proteins and subcellular localization (Nogawa et al., 2017). A metabolite named trachyspic acid 19-butyl ester ( 17 ) (Figure 5) along with trachyspic acid was isolated from uncharacterized fungus RKGS-F2684 (Nogawa et al., 2017).…”

“…The C terminus of Plk1 has polo-box domain (PBD), which is essential for interaction with other proteins and subcellular localization (Nogawa et al., 2017). A metabolite named trachyspic acid 19-butyl ester ( 17 ) (Figure 5) along with trachyspic acid was isolated from uncharacterized fungus RKGS-F2684 (Nogawa et al., 2017). Trachyspic acid 19-butyl ester and trachyspic acid showed inhibition toward PBD-dependent binding with an IC 50 value of 102 and 128 μM, which was comparable with purpurogallin (IC 50 : 114 μM), which served as positive control (Nogawa et al., 2017).…”

“…A metabolite named trachyspic acid 19-butyl ester ( 17 ) (Figure 5) along with trachyspic acid was isolated from uncharacterized fungus RKGS-F2684 (Nogawa et al., 2017). Trachyspic acid 19-butyl ester and trachyspic acid showed inhibition toward PBD-dependent binding with an IC 50 value of 102 and 128 μM, which was comparable with purpurogallin (IC 50 : 114 μM), which served as positive control (Nogawa et al., 2017). This result shed light on other probable cellular targets of trachyspic acid derivatives.…”

One‐pot two‐step synthesis of fused thiazinofuranone linked geminal bis 1,2,3‐triazole hybrids and their in vitro cytotoxic screening

“…Furanones and their fused frameworks are versatile heterocyclic moieties that exist in many natural products [1,2] and biologically active compounds [3]. In particular, 2,2-di substituted furanone core is present in many natural products such as Pseurotin A [4], Hyperolactone C [5,6], Trachyspic acid [7,8], Jatrophone [9], Eremantholide A [10], Cephalimysin A [11], Geiparvarin [12,13], Bullatenone [14] Griseofulvin [15] and have been discovered to possess a broad range of medicinal applications [3] and also used for the synthesis of fluorescent materials [16].…”