A novel lipid compound, epolactaene, induces apoptosis: its action is modulated by its side chain structure

Epo-C12 inhibits peroxiredoxin 1 peroxidase activity

Epo-C12 is a synthetic derivative of epolactaene, isolated from Penicillium sp. BM 1689-P. Epo-C12 induces apoptosis in human acute lymphoblastoid leukemia BALL-1 cells. In our previous studies, seven proteins that bind to Epo-C12 were identified by a combination of pull-down experiments using biotinylated Epo-C12 (Bio-Epo-C12) and mass spectrometry. In the present study, the effect of Epo-C12 on peroxiredoxin 1 (Prx 1), one of the proteins that binds to Epo-C12, was investigated. Epo-C12 inhibited Prx 1 peroxidase activity. However, it did not suppress its chaperone activity. Binding experiments between Bio-Epo-C12 and point-mutated Prx 1s suggest that Epo-C12 binds to Cys⁵² and Cys⁸³ in Prx 1. The present study revealed that Prx 1 is one of the target proteins through which Epo-C12 exerts an apoptotic effect in BALL-1 cells.

Benzothiazole inhibits the growth of Phytophthora capsici through inducing apoptosis and suppressing stress responses and metabolic detoxification

Benzothiazole (BZO) is an antimicrobial secondary metabolite volatilized by many plants and microbes. However, the mechanism of BZO against phytopathogens is still unclear. Here, we found that BZO has antimicrobial activity against the oomycete pathogen Phytophthora capsici. Transcriptome and proteome analyses demonstrated that BZO significantly suppressed the expression of genes and proteins involved in morphology, abiotic stress defense and detoxification, but induced the activity of apoptosis. Annexin V-FITC/PI staining confirmed that the process of apoptosis was significantly induced by BZO at concentration of 150 mg L^-1. FITC-phalloidin actin-cytoskeleton staining combined with hyphal cell wall staining and hyphal ultrastructure studies further confirmed that BZO disrupted the cell membrane and hyphal morphology through disrupting the cytoskeleton, eventually inhibiting the growth of hyphae. These data demonstrated that BZO has multiple modes of action and may act as potential leading compound for the development of new oomycete fungicides. These results also showed that the combination of transcriptomic and proteomic approaches was a useful method for exploring the novel antifungal mechanisms of natural compounds.

Synthetic and structure-activity relationship studies on bioactive natural products

This review summarizes our research into the synthesis and structure-activity relationships of epolactaene, neoechinulin A, plakevulin A, pseudodeflectusin and ustusorane C. These natural products are attractive in view of their apoptosis-inducing activity, cytoprotective activity against peroxynitrite, inhibitory activity against DNA polymerases, and cytotoxicity in cancer cells.

Chemistry and biology of non-tetramic gamma-hydroxy-gamma-lactams and gamma-alkylidene-gamma-lactams from natural sources

Natural products containing non-tetramic gamma-hydroxy-gamma-lactams and gamma-alkylidene-gamma-lactams are usually but not exclusively derived from the mixed polyketide-non-ribosomal peptide biosynthetic pathway. Often they are fungal metabolites, although some plant- and marine-derived exceptions exist. Owing to their unique structures and biological properties, they have gained interest in the chemical and biological communities. In this review, we aim to emphasize the structural originality of these compounds, their biological properties and the synthetic efforts developed to reach them; 157 references are cited.

Epolactaene binds human Hsp60 Cys442 resulting in the inhibition of chaperone activity

Epolactaene is a microbial metabolite isolated from Penicillium sp., from which we synthesized its derivative ETB (epolactaene tertiary butyl ester). In the present paper, we report on the identification of the binding proteins of epolactaene/ETB, and the results of our investigation into its inhibitory mechanism. Using biotin-labelled derivatives of epolactaene/ETB, human Hsp (heat-shock protein) 60 was identified as a binding protein of epolactaene/ETB in vitro as well as in situ. In addition, we found that Hsp60 pre-incubated with epolactaene/ETB lost its chaperone activity. The in vitro binding study showed that biotin-conjugated epolactaene/ETB covalently binds to Hsp60. In order to investigate the binding site, binding experiments with alanine mutants of Hsp60 cysteine residues were conducted. As a result, it was suggested that Cys442 is responsible for the covalent binding with biotin-conjugated epolactaene/ETB. Furthermore, the replacement of Hsp60 Cys442 with an alanine residue renders the chaperone activity resistant to ETB inhibition, while the alanine replacement of other cysteine residues do not. These results indicate that this cysteine residue is alkylated by ETB, leading to Hsp60 inactivation.

Apoptosis-inducing effect of epolactaene derivatives on BALL-1 cells

Epolactaene, a neuritogenic compound in human neuroblastoma SH-SY5Y, induces apoptosis in a human leukemia B-cell line, BALL-1. The apoptosis-inducing activities of 34 epolactaene derivatives, including those of the newly synthesized alpha-alkyl-alpha,beta-epoxy-gamma-lactam derivative and cyclopropane derivatives, were also tested. The structure-activity relationships of the epolactaene derivatives as an inducer of apoptosis are described. The alpha-acyl-alpha,beta-epoxy-gamma-lactam moiety as well as the hydrophobicity derived from the long alkyl side chain are both important for activity. Compound 1e displayed the strongest activity among all the synthesized compounds with an IC50 value of 0.70 microM.

Structure–activity relationships of epolactaene derivatives: structural requirements for inhibition of Hsp60 chaperone activity

Epolactaene is a microbial metabolite isolated from the fungal strain Penicillium sp. It arrests the cell cycle at the G0/G1 phase and induces the outgrowth of neurites in human neuroblastoma SH-SY5Y cells. In this communication, we report the structure-activity relationships (SARs) of new epolactaene derivatives, including those lacking the epoxylactam moiety and having various side chains. These derivatives were evaluated for their ability to inhibit the growth of human cancer cell lines. They were also analyzed for their ability to affect human heat shock protein 60 (Hsp60), which we have already identified as a protein that binds to epolactaene. We also identified the important structural framework of epolactaene/ETB (epolactaene tertiary butyl ester) for not only binding to Hsp60 but also inhibiting Hsp60 chaperone activity.

Structure–activity relationships of epolactaene analogs as DNA polymerases inhibitors

Epolactaene, a neuritogenic compound in human neuroblastoma cells, showed inhibitory activities against DNA polymerases alpha and beta. The synthesis and inhibitory activities of epolactaene analogs are described. The alpha,beta-epoxy-gamma-lactam moiety in the core and the length of the side chain greatly influenced the activities. Compound 5 was the strongest inhibitor of DNA polymerase alpha and beta of all synthesized compounds with IC(50) values of 13 and 78 microM, respectively. N- and O-alkyl derivatives that had modified core moieties showed moderate inhibition.