Use of an Antibacterial Cell-Penetrating Peptide for Intracellular Protein Delivery and the Identification of Tyrphostin-A9 as an Allosteric Inhibitor of Furin

Cationic amphiphilic polyproline helices (CAPHs) have been shown to penetrate cells and target intracellular pathogenic bacteria. Disclosed herein are efforts made towards the structural optimization of these peptides by way of hydrophobic modification to increase their function. Additionally, with the rising interest of biologics as a therapeutic modality, the most optimal peptide with regards to cell uptake was leveraged with the aim of delivering protein cargo into cells. To this end, CAPH-GFP conjugates were prepared and shown to traverse the HeLa cell membrane via confocal imaging analysis, thus highlighting the versatility of the CAPHs platform.

Moreover, the proprotein convertase (PC) furin has been shown to be involved in the pathology of SARS- CoV-2 whereby it cleaves an acquired furin recognition sequence on the spike (S) glycoprotein, prompting a conformational change and promoting infection. Previous findings in our research lab had identified the molecule tyrphostin-A9 as being an inhibitor of furin through a library screen. Discussed herein are studies aimed at derivatizing the molecular scaffold of tyrphostin-A9 to determine structure-activity relationships and mechanism of action. Mechanistic analysis of the designed agents suggested an allosteric binding mode which is underrepresented for inhibitors of this protein.