(Bio)Syntheses of chondramides and related cyclodepsipeptides

粘细菌产生丰富的生物活性天然产物，包括环肽和脱脂肽，如软骨和鱼藤酰胺。球粒主要与肌动蛋白细胞骨架相互作用，但只有零星的实验与尿胺和相关的多肽，可能是因为没有足够的材料可用于生物测试。因此，我们的目标是在多肽修饰的基础上开发一种高度灵活的合成Miuraenamide及其相关多肽的方法。这一概念将使我们能够通过在合成的最后一步引入相关侧链来容易地生成类似化合物的库。这些环多肽和相关化合物的化合物文库应在各种基于细胞的和体外生物检测中进行筛选，以建立结构-活性关系。此外，应该开发和应用有针对性的方法来阐明假定的分子靶标和表征蛋白质-配体的相互作用。该项目的另一个目标是生产和生物学评价新的软骨酰胺变种，这种变种基于结构变化，表现出比原始类似物更具癌细胞特异性的作用模式。在对这类化合物的新天然衍生物的初步研究中，在第一个资助期内发现的另一种生产者菌株中，已经表明核心结构的特定衍生化导致对癌细胞系更高的细胞毒性。总体而言，这些研究暗示了肌动蛋白以外的一个假定的细胞靶点(非靶点)，这将在进一步的研究中确定和研究。为了确保测试物质的充足供应，计划采用应由生物技术启动的合成方法。为了保证可持续供应，将对最初的软骨酰胺生产菌株进行基因工程改造，从而允许发酵生产新的软骨酰胺和进一步的衍生品。生物合成基因簇的靶向操作还将允许合成前体的掺入，以使突变合成起点能够产生所需的结构变体。此外，还将优化发酵生物技术的生产工艺，以适应具体要求。

Myxobacteria produce a wealth of bioactive natural products including cyclic peptides and depsipeptides such as the chondramides and miuraenamides. The chondramides mainly interact with the actin cytoskeleton, but only sporadic experiments have been carried out with the miuraenamides and related peptides, probably because not enough material is available for biological testing. Therefore, our aim is to develop a highly flexible protocol for the synthesis of miuraenamides and related peptides, based on peptide modification. This concept would allow us to generate libraries of similar compounds easily by introducing relevant side chains in the last step of the synthesis. Compound libraries of these cyclic depsipeptides and related compounds shall be screened in various cell-based and in vitro biological assays in order to establish structure-activity relationships. Furthermore, targeted approaches shall be developed and applied to elucidate putative molecular targets and to characterize protein-ligand interactions. A further aim of the project is the production and biological evaluation of novel chondramide variants, which exhibit, based on structural variations, a more cancer cell specific mode of action than the original analogs. In initial studies with novel natural derivatives of this compound class, found in an alternative producer strain during the first funding period, it has already been shown that specific derivatizations of the core structure lead to higher cytotoxicity towards cancer cell lines. Overall, these studies implied a putative cellular target other than actin (off-target), which shall be identified and investigated in further studies. To ensure sufficient supply of test substances synthetic approaches which should be accomplished by biotechnological onsets are planned. To guarantee for a sustainable supply the original chondramide producer strain will be genetically engineered, thereby allowing fermentative production of the novel chondramides plus further derivatives. The targeted manipulation of the biosynthesis gene cluster shall furthermore allow the incorporation of synthesized precursors to enable mutasynthetic onsets to produce desired structural variants. Also the fermentative biotechnological production process will be optimized and adapted to the specific requirements.