(Bio)Syntheses of chondramides and related cyclodepsipeptides

黏菌产生丰富的生物活性天然产物，包括环肽和沉积肽，如chondramides和miuraenamides。软骨酰胺主要与肌动蛋白细胞骨架相互作用，但只有零星的实验进行了miuraenamide和相关肽，可能是因为没有足够的材料可用于生物学测试。因此，我们的目标是开发一种基于肽修饰的高度灵活的合成miuraenamides和相关肽的方案。这个概念将允许我们在合成的最后一步引入相关的侧链，从而很容易地生成类似化合物的文库。这些环状沉积肽及相关化合物的化合物文库需要在各种细胞和体外生物实验中筛选，以建立结构-活性关系。此外，应该开发和应用靶向方法来阐明假定的分子靶标和表征蛋白质-配体相互作用。该项目的另一个目标是生产和生物学评估新的软骨酰胺变体，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。在对该化合物类的新型天然衍生物的初步研究中，在第一个资助期内在替代生产者菌株中发现，已经表明核心结构的特定衍生化导致对癌细胞系具有更高的细胞毒性。总的来说，这些研究暗示了肌动蛋白以外的一个假定的细胞靶标（脱靶），这需要在进一步的研究中识别和研究。为确保试验物质的充足供应，计划了应由生物技术开始完成的合成方法。为了保证可持续供应，将对原始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型软骨酰胺及其进一步衍生物。生物合成基因簇的靶向操作应进一步允许合成前体的结合，以使突变合成发作产生所需的结构变异。发酵生物技术生产工艺也将根据具体要求进行优化和调整。

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.