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Chemical structure of cichorinotoxin, a cyclic lipodepsipeptide that is produced by Pseudomonas cichorii and causes varnish spots on lettuce.

ABSTRACT: Pseudomonas cichorii, which causes varnish spots on lettuce and seriously damages lettuce production during the summer season in the highland areas of Japan (e.g., Nagano and Iwate prefectures) was isolated. The structure of a toxin produced by this organism was analyzed based on the detailed evaluation of its 2D NMR and FABMS spectra, and this compound has not been reported previously. We propose the name cichorinotoxin for this toxin. In conjunction with the D or L configurations of each amino acid, which were determined by Marfey's method, we propose the structure of cichorinotoxin to be as follows: 3-hydroxydecanoyl-(Z)-dhThr¹-D-Pro²-D-Ala³-D-Ala⁴-D-Ala⁵-D-Val⁶-D-Ala⁷-(Z)-dhThr⁸-Ala⁹-Val¹⁰-D-Ile¹¹-Ser¹²-Ala¹³-Val¹⁴-Ala¹⁵-Val¹⁶-(Z)-dhThr¹⁷-D-alloThr¹⁸-Ala¹⁹-L-Dab²⁰-Ser²¹-Val²², and an ester linkage is present between D-alloThr¹⁸ and Val²² (dhThr: 2-aminobut-2-enoic acid; Dab: 2,4-diaminobutanoic acid). Thus, the toxin is a lipodepsipeptide with 22 amino acids. The mono- and tetraacetate derivatives and two alkaline hydrolysates, compounds A and B, were prepared. We discuss here the structure-activity relationships between the derivatives and their necrotic activities toward lettuce.

SUBMITTER: Komatsu H

PROVIDER: S-EPMC6369977 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Throughout recent history, metabolites of microbial origin have had an extraordinary impact on the welfare of humanity. In fact, natural products have largely been--and still are--considered an exceedingly valuable platform for the discovery of new drugs against diverse pathologies. Such value is partly due to their higher complexity and chemical diversity as compared to those of synthetic and combinatorial compounds. Mutations in the Von Hippel-Lindau (vhl) gene are responsible for VHL disease, congenital polycythemia, and are found in many sporadic tumor types. The primary cause of morbidity and mortality for these patients arises from progression of Renal Cell Carcinoma (RCC) or end-stage renal disease. Inactivation of the Von Hippel-Lindau (vhl) tumor suppressor gene arises in the majority of Renal Cell Carcinoma (RCC) as well as in other types of cancer and is associated with a high degree of vascularization and poor prognosis. Loss of pVHL function thus represents a pathognomonic molecular defect for therapeutic exploitation. In this study, renal carcinoma cell lines with naturally occurring vhl mutations (RCC4 VA) and their genetically matched wild-type vhl (RCC4 VHL) counterparts were seeded onto 96-well plates and treated with a collection of 1,040 organic extracts obtained from 130 bacterial strains belonging to at least 25 genera of the phyla Actinobacteria, Firmicutes, Proteobacteria and Bacteroidetes. This strategy allowed us to identify several extracts obtained from bacterial strain F-278,770T, the type strain of the recently proposed new species Pseudomonas granadensis, showing biological activities not associated with previously known bioactive metabolites. The fractionation and structural elucidation of one of these extracts led to the discovery of a new lipodepsipeptide (MDN-0066) with specific toxicity in pVHL deficient cells that is not detectable in cells with pVHL expression rescue. This specific toxicity is associated with apoptosis induction in VHL deficient cell line as demonstrated with PARP activation and Annexin V staining. Our study demonstrated the feasibility of selectively targeting the loss of the vhl tumor suppressor gene for potential clinical benefit. Our results may have great impact on the development of new targeted therapies from natural products for the treatment of cancer and other genetic diseases.

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Chemical structure of cichorinotoxin, a cyclic lipodepsipeptide that is produced by Pseudomonas cichorii and causes varnish spots on lettuce.

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