A Library Approach to Cationic Amphiphilic Polyproline Helices that Target Intracellular Pathogenic Bacteria

Abstract

A number of pathogenic bacteria reproduce inside mammalian cells and are thus inaccessible to many antimicrobial drugs. Herein, we present a facile method to a focused library of antibacterial agents known as cationic amphiphilic polyproline helices (CAPHs). We identified three CAPHs from the library with superior cell penetration within macrophages and excellent antibacterial action against both Gram-positive and Gram-negative bacteria. These cell-penetrating antibacterial CAPHs have specific subcellular localizations that allow for targeting of pathogenic bacteria at their intracellular niches, a unique feature that promotes the successful clearance of intracellular pathogens ( Salmonella, Shigella, and Listeria) residing within macrophages. Furthermore, the selected CAPHs also significantly reduced bacterial infections in an in vivo model of Caenorhabditis elegans, with minimal in vivo toxicity.

Targeting Intracellular Pathogenic Bacteria Through N-Terminal Modification of Cationic Amphiphilic Polyproline Helices

“…flexneri), making treatment difficult. We had previously shown that altering the hydrophobic moieties on the backbone of CAPHs resulted in enhanced targeting of intracellular pathogens . Similarly, we wished to investigate if the N-terminal modifications on CAPHs could affect their ability to localize to specific subcellular compartments.…”

“…Altering the CAPH hydrophobic face has resulted in enhanced targeting of intracellular bacteria . Therefore, we wished to evaluate the role of N-terminal hydrophobic moieties on cell penetration and antimicrobial activity (Figure B).…”

Mitochondrion-Targeting Peptides and Peptidomimetics: Recent Progress and Design Principles

“…P14LRR, CAPH with 14 modified proline residues, demonstrated optimal mitochondrial localization at 2.5 μM . Later, it was found that extended CAPHs, such as 13-mer and 16-mer CAPHs, also have antibacterial activity, because the mitochondrial membrane and bacterial outer membrane share similar physicochemical properties. , …”

Antibiotic–cell‐penetrating peptide conjugates targeting challenging drug‐resistant and intracellular pathogenic bacteria

“…Elongation of the CAPHs, and sidechain and N‐terminal modifications demonstrated that the CAPH CPPs alone also display broad‐spectrum antibacterial activity, including activity against E. coli , S. aureus , and S. typhimurium , without perturbation of bacterial membranes or hemolysis (Hernandez‐Gordillo et al., 2014; Kuriakose et al., 2013; Nepal et al., 2015). Importantly, the subcellular localization of these CAPHs has been tailored to co‐localize with intracellular pathogenic bacteria, such as Listeria in the cytosol and Salmonella within vacuoles (Dietsche et al., 2020; Nepal et al., 2018). Therefore, coupled with cell penetration, these CPPs proved effective against intracellular bacteria with minimal mammalian cytotoxicity and minimal lysis of bacterial membranes.…”