Biological Effects of a Simplified Synthetic Analogue of Ion‐Channel‐Forming Polytheonamide B on Plasma Membrane and Lysosomes

• Published in: Chemistry : a European journal 2019-11, Vol.25 (66), p.15198-15204
• Main Authors: Xue, Yun‐Wei, Hayata, Atsushi, Itoh, Hiroaki, Inoue, Masayuki
• Format: Article
• Language: English
• Subjects: Amino acids; Apoptosis; Apoptosis - drug effects; Biological effects; Cell death; Cell Membrane - metabolism; Chemistry; cytotoxic agents; Cytotoxicity; Depolarization; Disruption; Fluorescent Dyes - chemistry; Humans; Hydrogen-Ion Concentration; Hydrophobic and Hydrophilic Interactions; Intracellular Signaling Peptides and Proteins - chemistry; Intracellular Signaling Peptides and Proteins - metabolism; Intracellular Signaling Peptides and Proteins - pharmacology; ion channels; Localization; Lysosomes; Lysosomes - metabolism; MCF-7 Cells; mechanisms of action; Membrane potential; Membrane Potentials - drug effects; Membranes; natural products; Neutralization; peptides; pH effects; Spectrometry, Fluorescence; Toxicity
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201903974

Polytheonamide B (1) is a linear 48‐mer natural peptide with alternating d‐ and l‐amino acid residues. Compound 1 forms conducting channels for monovalent ions and exhibits potent cytotoxicity against MCF‐7 cells. Previously, we reported that nanomolar concentrations of 1 induce plasma membrane depolarization and lysosomal pH disruption, which triggers apoptosis. Here, we report the cellular localization and biological action of a simplified synthetic analogue of 1, polytheonamide mimic 3. Compared with 1, the toxicity of 3 against MCF‐7 cells is 16 times weaker. Although its plasma membrane depolarization effect is only 3.6 times lower, more 3 (20‐fold) is required to neutralize lysosomal pH. Thus, the effective concentrations for lysosomal neutralization and cytotoxicity by 3 are comparable. These results strongly suggest that the activity of 3 against the lysosomal membrane is more important for apoptotic cell death than its effects on the plasma membrane, and provide valuable information regarding the unique behavior of polytheonamide‐based molecules. No effect without internalization: The detailed cellular behavior of a polytheonamide mimic 3, a structurally simplified synthetic analogue of ion‐channel‐forming 48‐mer natural peptide polytheonamide B (1), was investigated. Similarly to 1, compound 3 induces both plasma membrane depolarization and lysosomal pH neutralization. The intracellular effect of 3 on lysosomes is shown to be more important for its cytotoxicity (see figure).