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Cyclic phosphatidic acid (cPA), a structural analog of lysophosphatidic acid (LPA), is one of the simplest phospholipids found in every cell type. cPA is a specific, high-affinity antagonist of peroxisome proliferator-activated receptor gamma (PPARγ); however, the molecular mechanism by which cPA inhibits cellular proliferation remains to be clarified. In this study, we found that inhibition of PPARγ prevents proliferation of human colon cancer HT-29 cells. cPA suppressed cell growth, and this effect was reversed by the addition of a PPARγ agonist. These results indicate that the physiological effects of cPA are partly due to PPARγ inhibition. Our results identify PPARγ as a molecular mediator of cPA activity in HT-29 cells, and suggest that cPA and the PPARγ pathway might be therapeutic targets in the treatment of colon cancer.

The absolute stereochemistry of melleumin A (1) and B (2), novel peptide compounds isolated from the myxomycete Physarum melleum, was determined by synthesis of their segments and by a modified Mosher's method. Total synthesis of melleumin B (2) was achieved by a stereoselective method, which provided further evidence for all the absolute stereochemistries of melleumin B (2). The Wnt signal inhibitory activities of 2 and its 10R-epimer 19 were evaluated. Compound 19 showed moderate inhibition of Wnt signal transcription, which suggests that melleumin analogues might be useful as Wnt signal inhibitors.

The total synthesis of melleumin A (1), a novel cyclic depsipeptide isolated from the myxomycete Physarum melleum, and 3-epi-melleumin A (6) was achieved. Melleumin A-like compounds were also designed and synthesized; analysis of these melleumin A-like compounds showed moderate Wnt signal inhibition. Comparison of the inhibition activity of melleumin B and its three epimers, melleumin A, 3-epi-melleumin A and three melleumin A-like compounds led to further investigation of the structural conformation of the active molecules. The scaffold of melleumin is a potential target in the search for "peptide-like" Wnt signaling inhibitors.

Cyclic phosphatidic acid (cPA) is a naturally occurring phospholipid mediator, which has a quite unique cyclic phosphate ring at sn-2 and sn-3 positions of the glycerol backbone. We have designed and chemically synthesized several metabolically stabilized derivatives of cPA. 2-Carba-cPA (2ccPA) is one of the synthesized compounds in which the phosphate oxygen was replaced with a methylene group at the sn-2 position, and it showed much more potent biological activities than natural cPA. Here, we developed a new method of 2ccPA enantiomeric synthesis. And we examined the effects of 2ccPA enantiomers on autotaxin (ATX) activity, cancer cell invasion and nociceptive reflex. As well as racemic-2ccPA, both enantiomers showed inhibitory effects on ATX activity, cancer cell invasion and nociceptive reflex. As their effects were not significantly different from each other, the chirality of 2ccPA may not be critical for these biological functions of 2ccPA.

Cyclic phosphatidic acid (CPA) is found in cells from slime mold to humans and has a largely unknown function. We previously reported that cPA significantly inhibited the lipid accumulation in 3T3-L1 adipocytes through inhibition of PPAR gamma activation. We find here that CPA reduced intracellular triglyceride levels and inhibited the phosphodiesterase 3B (PDE3B) expression in 3T3-L1 adipocytes. PPAR gamma activation in adipogenesis that can be blocked by treatment with cPA then participates in adipocyte function through inhibition of PDE3B expression. We also found the intracellular cAMP levels in 3T3-L1 adipocytes increased after exposure to cPA. These findings contribute to the participation of cPA on the lipolytic activity in 3T3-L1 adipocytes. Our studies imply that CPA might be a therapeutic compound in the treatment of obesity and obesity-related diseases., Article, BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS. 404(1):109-114 (2011)

Cholesteryl glucoside (CG), a membrane glycolipid, regulates heat shock response. CG is rapidly induced by heat shock before the activation of heat shock transcription factor 1 (HSF1) and production of heat shock protein 70 (HSP70), and the addition of CG in turn induces HSF1 activation and HSP70 production in human fibroblasts; thus, a reasonable correlation is that CG functions as a crucial lipid mediator in stress responses in the animal. In this study, we focused on a CG-synthesizing enzyme, animal sterol glucosyltransferase, which has not yet been identified. In this study, we describe a novel type of animal sterol glucosyltransferase in hog stomach and human fibroblasts (TIG-3) detected by a sensitive assay with a fluorescence-labeled substrate. The cationic requirement, inhibitor resistance, and substrate specificity of animal sterol glucosyltransferase were studied. Interestingly, animal sterol glucosyltransferase did not use uridine diphosphate glucose (UDP-glucose) as an immediate glucose donor, as has been shown in plants and fungi. Among the glycolipids tested in vitro, glucosylceramide (GlcCer) was the most effective substrate for CG formation in animal tissues and cultured cells. Using chemically synthesized [U-((13))C]Glc-β-Cer as a glucose donor, we confirmed by mass spectrometry that [U-((13))C]CG was synthesized in hog stomach homogenate. These results suggest that animal sterol glucosyltransferase transfers glucose moiety from GlcCer to cholesterol. Additionally, using GM-95, a mutant B16 melanoma cell line that does not express ceramide glucosyltransferase, we showed that GlcCer is an essential substrate for animal sterol glucosyltransferase in the cell.

The absolute stereochemistry of melleumin A (1) and B (2), novel peptide compounds isolated from the myxomycete Physarum melleum, was determined by synthesis of their segments and by a modified Mosher’s method. Total synthesis of melleumin B (2) was achieved by a stereoselective method, which provided further evidence for all the absolute stereochemistries of melleumin B (2). The Wnt signal inhibitory activities of 2 and its 10R-epimer 19 were evaluated. Compound 19 showed moderate inhibition of Wnt signal transcription, which suggests that melleumin analogues might be useful as Wnt signal inhibitors.

Γwo stereoisomers of melleumin B (1), seco acid methyl ester of melleumin A (2), which are novel peptide compounds isolated from the myxomycete Physarum melleum, were synthesized and evaluated for their inhibition of Wnt signal transcription. The 3R-epimer and (3R, 4S, 10R, 11R)-isomer of 1 showed moderate inhibition of the Wnt signal.

During our studies in a search for natural products from myxomycetes [1], we have isolated a novel peptide lactone, melleumin A (1), and its seco acid methyl ester, melleumin B (2), from the cultured plasmodium of the myxomycete Physarum melleum [2]. Absolute stereochemistry of these compounds was determined by synthesis of a segment and HPLC analysis [3]. We recently achieved total syntheses of melleumins A (1) and B (2), which further provided evidence for the whole structure of them. We also examined the Wnt signal inhibitory activity of 1, 2, and diastereomers (3–5) prepared by synthesis. The Wnt signaling pathway has important functions in vertebrate development, and its deregulation is believed to occur early in human colorectal cancer. Recently, compounds down-regulating Wnt signaling were therefore expected in new strategy for cancer therapy. A cell-based luciferase assay system showed that compound 3 moderately inhibited Wnt signal transcriptional activity and its diastereomers showed inhibition enhancement, suggesting that melleumin analogues may be useful as Wnt signal inhibitors. References: 1. Ishibashi, M. (2007) Yakugakuzasshi 127: 1369–1381. 2. Nakatani, S. et al. (2005) Tetrahedron Lett. 46: 267–271. 3. Hanazawa, S. et al. (2008) Bioorg. Med. Chem. Lett. 18: 95–98.