Mintaimycins, a Group of Novel Peptide Metabolites from Micromonospora sp. C-3509.

A group of peptide metabolites (1-4), designated as mintaimycins, were isolated from Micromonospora sp. C-3509. The planar structures of mintaimycins were determined by combination of mass spectrometry, 1D and 2D NMR spectroscopy, and the stereochemistry of mintaimycins were partially resolved by Marfey's or Mosher's method. Mintaimycins featured a central ß-methylphenylalanine or phenylalanine linked at its amino group with 5-methyl-2-hexenoic acid, and at its carboxyl group with 5-hydroxy-norleucine or leucine that combined a derivative of hexanoic acid or 4-methylpentanoic acid. Mintaimycin A1 (1), the principal component, was found to exhibit the biological activity of inducing pre-adipocyte differentiation of 3T3-L1 fibroblast cells at 10.0 µmol/L.

Isarubrolone C Promotes Autophagic Degradation of Virus Proteins via Activating ATG10S in HepG2 Cells.

Isarubrolone C is a bioactive polycyclic tropoloalkaloid from Streptomyces. Our previous study showed that isarubrolone C could trigger autophagy. Here, we report isarubrolone C potential in broad-spectrum antiviral effect and its antiviral mechanism in vitro. Our results show that isarubrolone C activated autophagy and reduced levels of viral proteins in the cells harboring HCV-CORE/NS5B, HBx, ZIKV-NS5, and HIV-RT, respectively. The role of isarubrolone C in suppression of the viral proteins was via an autophagic degradation pathway rather than a proteasome pathway. Co-immunoprecipitation assays revealed that isarubrolone C promoted both autophagy flux opening and the viral proteins being enwrapped in autolysosomes. PCR assays showed that isarubrolone C elevated the transcription levels of ATG10/ATG10S and IL28A. Further, ATG10S high expression could efficiently enhance IL28A expression and the ability of isarubrolone C to degrade the viral proteins by promoting the colocalization of viral proteins with autolysosomes. Additionally, knockdown of endogenous IL28A caused both losses of the isarubrolone C antiviral effect and autolysosome formation. These results indicate that the role of isarubrolone C antiviruses is achieved by triggering the autophagic mechanism, which is mediated by endogenous ATG10S and IL28A activation. This is the first report about isarubrolone C potential of in vitro broad-spectrum antiviruses.

Cervinomycins C1-4 with cytotoxic and antibacterial activity from Streptomyces sp. CPCC 204980.

Polycyclic xanthones are secondary metabolites from actinomycetes and cervinomycin A and B are bioactive 26-membered polycyclic xanthones from Streptomyces sp. CPCC 204980. Herein, we report cervinomycins C1-4 (1-4) from the same strain. The structures of 1-4 were determined by 1D- and 2D-NMR, or single-crystal X-ray diffraction. Compounds 1-4 feature the open or loss of A (oxazolidine) ring in their angular polycyclic framework compared with cervinomycin B. Compounds 1-4 showed potent cytotoxicity against human cancer cell lines HCT116 and BxPC-3, with IC50 at 0.9-801.0 nM and strong anti-Gram-positive bacterial activity.

Cytotoxic and Antibacterial Cervinomycins B1-4 from a Streptomyces Species.

AntiSMASH analysis of genome DNA of Streptomyces CPCC 204980, a soil isolate with potent antibacterial activity, revealed a gene cluster for polycyclic xanthones. A subsequent chemical study confirmed that the microorganism produced polycyclic xanthone cervinomycin A2 (1) and the new congeners cervinomycins B1-4 (2-5). The structures of 1-5 were determined by comprehensive analyses of MS and NMR data, which indicated that 2-5 featured a common dihydro-D ring in the polycyclic xanthone core moiety of their molecules. 2-5 are toxic to human cancer cells and active against Gram-positive bacteria.

Genome-Guided Discovery of Pretilactam from Actinosynnema pretiosum ATCC 31565.

Actinosynnema is a small but well-known genus of actinomycetes for production of ansamitocin, the payload component of antibody-drug conjugates against cancers. However, the secondary metabolite production profile of Actinosynnema pretiosum ATCC 31565, the most famous producer of ansamitocin, has never been fully explored. Our antiSMASH analysis of the genomic DNA of Actinosynnema pretiosum ATCC 31565 revealed a NRPS-PKS gene cluster for polyene macrolactam. The gene cluster is very similar to gene clusters for mirilactam and salinilactam, two 26-membered polyene macrolactams from Actinosynnema mirum and Salinispora tropica, respectively. Guided by this bioinformatics prediction, we characterized a novel 26-membered polyene macrolactam from Actinosynnema pretiosum ATCC 31565 and designated it pretilactam. The structure of pretilactam was elucidated by a comprehensive analysis of HRMS, 1D and 2D-NMR, with absolute configuration of chiral carbons predicted bioinformatically. Pretilactam features a dihydroxy tetrahydropyran moiety, and has a hexaene unit and a diene unit as its polyene system. A preliminary antibacterial assay indicated that pretilactam is inactive against Bacillus subtilis and Candida albicans.

Isarubrolones Containing a Pyridooxazinium Unit from Streptomyces as Autophagy Activators.

Isarubrolones are bioactive polycyclic tropoloalkaloids from Streptomyces. Three new isarubrolones (2-4), together with the known isarubrolone C (1) and isatropolones A (5) and C (6, 3( R)-hydroxyisatropolone A), were identified from Streptomyces sp. CPCC 204095. The structures of these compounds were determined using a combination of mass spectrometry, 1D and 2D NMR spectroscopy, and ECD. Compounds 3 and 4 feature a pyridooxazinium unit, which is rarely seen in natural products. Compound 6 could conjugate with amino acids or amines to expand the structural diversity of isarubrolones with a pentacyclic or hexacyclic core. Importantly, 1 and 3-6 were found to induce complete autophagy.

Geninthiocins C and D from Streptomyces as 35-membered macrocyclic thiopeptides with modified tail moiety.

Geninthiocin is a thiopeptide with 35-membered macrocyclic core moiety. It has potent anti-Gram-positive (G+) bacteria activity. Herein, we reported two new congeners (2-3) of geninthiocin (geninthiocin A, 1) from Streptomyces sp. CPCC 200267, and designated them as geninthiocins C and D, whose structures were determined by NMR. Geninthiocins A, C and D had the same 35-membered macrocyclic core moiety, but possessed a -Dha-Dha-NH2, -Dha-Ala-NH2, and -NH2 tail, respectively. Besides, the Ala residue in geninthiocin C was determined as L- configuration by C3 Marfey's method. In vitro assays indicated that geninthiocins C-D showed no antibacterial activity, in contrast to the potent anti-G+ bacteria activity displayed by geninthiocin A. Therefore, the -Dha-Dha-NH2 tail of geninthiocin A played an important role in its potent activity against G+ bacteria.

Quinohemanine, a quinoxalinone-bohemamine hybrid compound from Streptomyces sp. CPCC 200497.

A quinoxalinone-bohemamine hybrid compound quinohemanine (1), together with 1-methyl-2(H)-quinoxalin-2-one (2), was isolated from Streptomyces sp. CPCC 200497, a producer of quinomycins and bohemamines. Compounds 1 and 2 were purified using standard chromatographic methods, and their structures were defined through interpretation of HRMS, 1D, and 2D NMR data. Both 1 and 2 displayed moderate cytotoxicity against cancer cell line HepG2.

Cytotoxic Dibohemamines D-F from a Streptomyces Species.

Three dimeric analogues of bohemamines, dibohemamines D-F (1-3), together with dibohemamine A (4), were isolated from Streptomyces sp. CPCC 200497. Their structures were solved using a combination of mass spectrometry, 1D and 2D NMR spectroscopy, and CD. Dibohemamines D and E were new dimeric analogues of bohemamines, and dibohemamine F was a known compound obtained previously by semisynthesis. Dibohemamine F displayed potent cytotoxicity against cancer cell lines A549 and HepG2 with IC50 values of 1.1 and 0.3 µM, respectively. Dibohemamines D and E showed moderate cytotoxicity against cancer cell lines A549 and HepG2.

Binding of a biosynthetic intermediate to AtrA modulates the production of lidamycin by Streptomyces globisporus.

The control of secondary production in streptomycetes involves the funneling of environmental and physiological signals to the cluster-situated (transcriptional) regulators (CSRs) of the biosynthetic genes. For some systems, the binding of biosynthetic products to the CSR has been shown to provide negative feedback. Here we show for the production of lidamycin (C-1027), a clinically relevant antitumor agent, by Streptomyces globisporus that negative feedback can extend to a point higher in the regulatory cascade. We show that the DNA-binding activity of the S. globisporus orthologue of AtrA, which was initially described as a transcriptional activator of actinorhodin biosynthesis in S. coelicolor, is inhibited by the binding of heptaene, a biosynthetic intermediate of lidamycin. Additional experiments described here show that S. globisporus AtrA binds in vivo as well as in vitro to the promoter region of the gene encoding SgcR1, one of the CSRs of lidamycin production. The feedback to the pleiotropic regulator AtrA is likely to provide a mechanism for coordinating the production of lidamycin with that of other secondary metabolites. The activity of AtrA is also regulated by actinorhodin. As AtrA is evolutionarily conserved, negative feedback of the type described here may be widespread within the streptomycetes.

Synthesis and biological evaluation of geldanamycin analogs against human cancer cells.

PURPOSE: To find novel potential and less toxic benquinone anamycin heat shock protein 90 (Hsp90) inhibitors as anticancer agents, a limited series of 17-substituted or 17,19-disubstituted 17-demethoxygeldanamycin analogs were synthesized and tested for anti-proliferation activity against human cancer cells. Liver toxicity was also tested in vivo. METHODS: Five 17-alkylamino-17-demethoxygeldanamycins and two 17-alkylamino-19-methylthio-17-demethoxygeldanamycins were synthesized from geldanamycin (GA) and 19-methylthiogeldanamycin (19-S(methyl)-GA), respectively. Anti-proliferation activities of the GA analogs were determined in MCF7, HeLa, HCT116 and HepG2 cells using the MTT method. Western blot and cell cycle analyses were performed for mechanistic study. The growth inhibition effect of potential geldanamycins was also investigated in normal Buffalo rat liver (BRL) cells. In vivo liver toxicity was tested in Institute of Cancer Research (ICR) mice by tail vein injection of the tested compounds. RESULTS: Most of the 17-alkylaminogeldanamycins exhibited obvious growth inhibition effects on multiple human cancer cell lines. The anti-proliferation activity of 19-methylthio-substituted geldanamycins was significantly lower compared with no 19-substitution geldanamycins in all tested cancer cells. The compound 1b (17-[2-(piperidinyl-1'-yl)-ethylamino]-17-demethoxygeldanamycin) exhibited the highest anti-proliferation activity in MCF7, HeLa and HCT116 cells, which was much more effective than GA and the developing Hsp90 inhibitor 17-AAG (17-allylamino-17-demethoxygeldanamycin). Meanwhile, compound 1b exhibited weaker growth inhibition effect on BRL cell line than GA and 17-AAG. 1b induced cell cycle arrest at the G2/M phase in MCF7 cells. Cleavage of PARP associated with apoptosis and degradation of the Hsp90 client protein Akt and Her2 was also induced by treatment of 1b in HeLa and MCF7 cell lines. In spite of the relatively weaker activity of 1b compared with GA and 17-AAG against HepG2 cells, 1b was further identified with lower hepatotoxicity than GA in vivo. CONCLUSION: Compound 1b is regarded as a new potential Hsp90 inhibitor with low hepatotoxicity for further study.

6-Deoxy-13-hydroxy-8,11-dione-dihydrogranaticin B, an intermediate in granaticin biosynthesis, from Streptomyces sp. CPCC 200532.

A new granaticin analogue and its hydrolysis product were isolated from Streptomyces sp. CPCC 200532. Their structures were determined to be 6-deoxy-13-hydroxy-8,11-dione-dihydrogranaticins B (1) and A (2), respectively, by detailed analysis of spectroscopic data. Compound 1 was regarded as an intermediate in granaticin biosynthesis, as it was bioconvertable to granaticin B. Compared to granaticin B, 1 showed similar cytotoxicity against cancer cell line HCT116, but decreased cytotoxicity against cancer cell lines A549, HeLa, and HepG2. Compound 2 displayed lower cytotoxicity than 1 against all four cancer cell lines tested.

[Synthetic biology toward microbial secondary metabolites and pharmaceuticals].

Microbial secondary metabolites are one of the major sources of anti-bacterial, anti-fungal, antitumor, anti-virus and immunosuppressive agents for clinical use. Present challenges in microbial pharmaceutical development are the discovery of novel secondary metabolites with significant biological activities, improving the fermentation titers of industrial microbial strains, and production of natural product drugs by re-establishing their biosynthetic pathways in suitable microbial hosts. Synthetic biology, which is developed from systematic biology and metabolic engineering, provides a significant driving force for microbial pharmaceutical development. The review describes the major applications of synthetic biology in novel microbial secondary metabolite discovery, improved production of known secondary metabolites and the production of some natural drugs in genetically modified or reconstructed model microorganisms.

19-[(1'S,4'R)-4'-Hydroxy-1'-methoxy-2'-oxopentyl]geldanamycin, a natural geldanamycin analogue from Streptomyces hygroscopicus 17997.

A novel natural geldanamycin analogue was discovered in Streptomyces hygroscopicus 17997. Its 4,5-dihydro form was also identified in the gdmP gene disruption mutant of Streptomyces hygroscopicus 17997. The structures of the two compounds were determined to be 19-[(1'S,4'R)-4'-hydroxy-1'-methoxy-2'-oxopentyl]geldanamycin (1) and 19-[(1'S,4'R)-4'-hydroxy-1'-methoxy-2'-oxopentyl]-4,5-dihydrogeldanamycin (2), respectively, by extensive spectroscopic data analysis, including 2D NMR, modified Mosher's method, and electronic circular dichroism. Compared to geldanamycin, 1 and 2 showed increased water solubility and decreased cytotoxicity against HepG2 cells.

Novel 4,5-dihydro-thiazinogeldanamycin in a gdmP mutant strain of Streptomyces hygroscopicus 17997.

Novel geldanamycin derivative, 4,5-dihydro-thiazinogeldanamycin (3), was characterized from the gdmP mutant in Streptomyces hygroscopicus 17997, besides expected 4,5-dihydro-geldanamycin (2). The presence of this compound would suggest an unknown post-PKS modification in geldanamycin biosynthesis. Compound 3 exhibited moderate anti-HSV-1-virus activity and higher water solubility than geldanamycin (1). Cysteine served as a precursor to synthesize 3, whose formation required obligatory enzymatic assistance.

Thiazinogeldanamycin, a new geldanamycin derivative produced by Streptomyces hygroscopicus 17997.

A new geldanamycin (GDM) derivative was discovered and isolated from the fermentation broth of Streptomyces hygroscopicus 17997. Its chemical structure was elucidated as thiazinogeldanamycin by LC-MS, sulfur analysis, and NMR. The addition of cysteine to the fermentation medium significantly stimulated the production level of thiazinogeldanamycin, suggesting cysteine as a precursor of thiazinogeldanamycin production. Although showing a decreased cytotoxicity against HepG2 cancer cells, thiazinogeldanamycin exhibited an improved water solubility and photostability. Thiazinogeldanamycin may represent the first natural GDM derivative characterized so far that uses GDM as its precursor. Its appearance also clearly indicates that an appropriate end-point of fermentation is of critical importance for the maximal production of GDM by Streptomyces hygroscopicus 17997.