Publications

Background By 2016, signs of emergence of Plasmodium falciparum resistance to artemisinin and partner drugs were detected in the Greater Mekong Subregion. Recently, the independent evolution of artemisinin resistance has also been reported in Africa and South America. This alarming scenario calls for the urgent development of new antimalarials with novel modes of action. We investigated the interference with protein aggregation, which is potentially toxic for the cell and occurs abundantly in all Plasmodium stages, as a hitherto unexplored drug target in the pathogen. Results Attempts to exacerbate the P. falciparum proteome's propensity to aggregation by delivering endogenous aggregative peptides to in vitro cultures of this parasite did not significantly affect their growth. In contrast, protein aggregation inhibitors clearly reduced the pathogen's viability. One such compound, the bis(styrylpyridinium) salt YAT2150, exhibited potent antiplasmodial activity with an in vitro IC50 of 90 nM for chloroquine- and artemisinin-resistant lines, arresting asexual blood parasites at the trophozoite stage, as well as interfering with the development of both sexual and hepatic forms of Plasmodium. At its IC50, this compound is a powerful inhibitor of the aggregation of the model amyloid beta peptide fragment 1-40, and it reduces the amount of aggregated proteins in P. falciparum cultures, suggesting that the underlying antimalarial mechanism consists in a generalized impairment of proteostasis in the pathogen. YAT2150 has an easy, rapid, and inexpensive synthesis, and because it fluoresces when it accumulates in its main localization in the Plasmodium cytosol, it is a theranostic agent. Conclusions Inhibiting protein aggregation in Plasmodium significantly reduces the parasite's viability in vitro. Since YAT2150 belongs to a novel structural class of antiplasmodials with a mode of action that potentially targets multiple gene products, rapid evolution of resistance to this drug is unlikely to occur, making it a promising compound for the post-artemisinin era.

JTD Keywords: amyloid pan-inhibitors, antimalarial drugs, malaria, plasmodium falciparum, protein aggregation, Amyloid formation, Amyloid pan-inhibitors, Antimalarial drugs, Colocalization, Cytosolic delivery, Derivatives, Disease, Drug, In-vitro, Malaria, Mechanism, Plasmodium falciparum, Polyglutamine, Protein aggregation, Yat2150

© 2020 Wiley-VCH GmbH Cytosolic protein delivery remains elusive. The inability of most proteins to cross the cellular membrane is a huge hurdle. Here we explore the unique photothermal properties of gold nanorods (AuNRs) to trigger cytosolic delivery of proteins. Both partners, protein and AuNRs, are modified with a protease-resistant cell-penetrating peptide with nuclear targeting properties to induce internalization. Once internalized, spatiotemporal control of protein release is achieved by near-infrared laser irradiation in the safe second biological window. Importantly, catalytic amounts of AuNRs are sufficient to trigger cytosolic protein delivery. To the best of our knowledge, this is the first time that AuNRs with their maximum of absorption in the second biological window are used to deliver proteins into the intracellular space. This strategy represents a powerful tool for the cytosolic delivery of virtually any class of protein.

JTD Keywords: cell-penetrating peptide, cytosolic delivery, gold nanorod, near-infrared irradiation, Cell-penetrating peptide, Cytosolic delivery, Gold nanorod, Near-infrared irradiation

© 2021 by the authors. Licensee MDPI, Basel, Switzerland. Achieving intracellular delivery of protein therapeutics within cells remains a significant challenge. Although custom formulations are available for some protein therapeutics, the development of non‐toxic delivery systems that can incorporate a variety of active protein cargo and maintain their stability, is a topic of great relevance. This study utilized ionic polyphosphazenes (PZ) that can assemble into supramolecular complexes through non‐covalent interactions with different types of protein cargo. We tested a PEGylated graft copolymer (PZ‐PEG) and a pyrrolidone containing linear derivative (PZ‐PYR) for their ability to intracellularly deliver FITC‐avidin, a model protein. In endothelial cells, PZ‐PYR/protein exhibited both faster internalization and higher uptake levels than PZ‐PEG/protein, while in cancer cells both polymers achieved similar uptake levels over time, although the internalization rate was slower for PZ‐PYR/protein. Uptake was mediated by endocytosis through multiple mechanisms, PZ‐PEG/avidin colocalized more profusely with endo-lysosomes, and PZ‐PYR/avidin achieved greater cytosolic delivery. Consequently, a PZ‐PYR-delivered anti‐F‐actin antibody was able to bind to cytosolic actin filaments without needing cell permeabilization. Similarly, a cell‐impermeable Bax‐BH3 peptide known to induce apoptosis, decreased cell viability when complexed with PZ‐PYR, demonstrating endo‐lysosomal escape. These biodegradable PZs were non‐toxic to cells and represent a promising platform for drug delivery of protein therapeutics.

JTD Keywords: cytosolic delivery, cytotoxicity, delivery of apoptotic peptides, endosomal escape, intracellular delivery of antibody, intracellular protein delivery, Cytosolic delivery, Cytotoxicity, Delivery of apoptotic peptides, Endosomal escape, Intracellular delivery of antibody, Intracellular protein delivery, Polyphosphazene polymers