Unique amalgamation of primary and secondary structural elements transform peptaibols into potent bioactive cell-penetrating peptides.
Lin DuApril L RisingerCarter A MitchellJianlan YouBlake W StampsNing PanJarrod B KingJean C BopassaSusan I V JudgeZhibo YangBradley S StevensonRobert H CichewiczPublished in: Proceedings of the National Academy of Sciences of the United States of America (2017)
Mass-spectrometry-based metabolomics and molecular phylogeny data were used to identify a metabolically prolific strain of Tolypocladium that was obtained from a deep-water Great Lakes sediment sample. An investigation of the isolate's secondary metabolome resulted in the purification of a 22-mer peptaibol, gichigamin A (1). This peptidic natural product exhibited an amino acid sequence including several β-alanines that occurred in a repeating ααβ motif, causing the compound to adopt a unique right-handed 311 helical structure. The unusual secondary structure of 1 was confirmed by spectroscopic approaches including solution NMR, electronic circular dichroism (ECD), and single-crystal X-ray diffraction analyses. Artificial and cell-based membrane permeability assays provided evidence that the unusual combination of structural features in gichigamins conferred on them an ability to penetrate the outer membranes of mammalian cells. Compound 1 exhibited potent in vitro cytotoxicity (GI50 0.55 ± 0.04 µM) and in vivo antitumor effects in a MIA PaCa-2 xenograft mouse model. While the primary mechanism of cytotoxicity for 1 was consistent with ion leakage, we found that it was also able to directly depolarize mitochondria. Semisynthetic modification of 1 provided several analogs, including a C-terminus-linked coumarin derivative (22) that exhibited appreciably increased potency (GI50 5.4 ± 0.1 nM), but lacked ion leakage capabilities associated with a majority of naturally occurring peptaibols such as alamethicin. Compound 22 was found to enter intact cells and induced cell death in a process that was preceded by mitochondrial depolarization.
Keyphrases
- cell death
- mass spectrometry
- amino acid
- mouse model
- high resolution
- cell cycle arrest
- single cell
- cell therapy
- molecular docking
- induced apoptosis
- oxidative stress
- magnetic resonance
- endothelial cells
- magnetic resonance imaging
- stem cells
- anti inflammatory
- diabetic rats
- high glucose
- photodynamic therapy
- electronic health record
- signaling pathway
- bone marrow
- gas chromatography
- machine learning
- molecular dynamics simulations
- stress induced
- deep learning