Novel cell-penetrating-amyloid peptide conjugates preferentially kill cancer cells

Biotechnological applications of amyloid fibrils

Protein aggregates and amyloid fibrils have special qualities and are used in a variety of biotechnological applications. They are extensively employed in bioremediation, biomaterials, and biocatalysis. Because of their capacity to encapsulate and release pharmaceuticals and their sensitivity to certain molecules, respectively, they are also used in drug delivery and biosensor applications. They have also demonstrated potential in the domains of food and bioremediation. Additionally, amyloid peptides have drawn interest in biological applications, especially in the investigation of illnesses like Parkinson's and Alzheimer's. The unique characteristics of amyloid fibrils, namely their mechanical strength and β-sheet structure, make them adaptable to a wide range of biotechnological uses. Even with their promise, one important factor to keep in mind before widely using modified amyloid materials is their potential toxicity. Thus, current research aims to overcome safety concerns while maximizing their potential.

Advancement and application of novel cell-penetrating peptide in cancer management

Cell-penetrating peptides (CPPs) are small amino acid sequences with the potential to enter cell membranes. Along with nucleic acids, large proteins, and other chemical compounds, they can deliver several bioactive cargos inside cells. Numerous CPPs have been extracted from natural or synthetic materials since the discovery of the first CPP. In the past few decades, a significant variety of studies have shown the potential of CPPs to cure different diseases. The low toxicity in peptide compared to other drug delivery carriers is a significant benefit of CPP-based therapy, in addition to the high efficacy brought about by swift and effective delivery. A significant tendency for intracellular DNA delivery may also be observed when nanoparticles and the cell penetration peptide are combined. CPPs are frequently used to increase intracellular absorption of nucleic acid, and other therapeutic agents inside the cell. Due to long-term side effects and possible toxicity, its implementation is restricted. The use of cell-permeating peptides is a commonly used technique to increase their intracellular absorption. Additionally, CPPs have lately been sought for application in vivo, following their success in cellular studies. This review will go through the numerous CPPs, the chemical modifications that improve their cellular uptake, the various means for getting them across cell membranes, and the biological activity they acquire after being conjugate with specific chemicals.

Studies of cell-penetrating peptides by biophysical methods

Biophysical studies have a very high impact on the understanding of internalization, molecular mechanisms, interactions, and localization of CPPs and CPP/cargo conjugates in live cells or in vivo. Biophysical studies are often first carried out in test-tube set-ups or in vitro, leading to the complicated in vivo systems. This review describes recent studies of CPP internalization, mechanisms, and localization. The multiple methods in these studies reveal different novel and important aspects and define the rules for CPP mechanisms, hopefully leading to their improved applicability to novel and safe therapies.

Specific Activation of the CD271 Intracellular Domain in Combination with Chemotherapy or Targeted Therapy Inhibits Melanoma Progression

CD271 (NGFR) is a neurotrophin receptor that belongs to the tumor necrosis receptor (TNFR) family. Upon ligand binding, CD271 can mediate either survival or cell death. Although the role of CD271 as a marker of tumor-initiating cells is still a matter of debate, its role in melanoma progression has been well documented. Moreover, CD271 has been shown to be upregulated after exposure to both chemotherapy and targeted therapy. In this study, we demonstrate that activation of CD271 by a short β-amyloid-derived peptide (Aβ^(25-35)) in combination with either chemotherapy or MAPK inhibitors induces apoptosis in 2D and 3D cultures of eight melanoma cell lines. This combinatorial treatment significantly reduced metastasis in a zebrafish xenograft model and led to significantly decreased tumor volume in mice. Administration of Aβ^(25-35) in ex vivo tumors from immunotherapy- and targeted therapy-resistant patients significantly reduced proliferation of melanoma cells, showing that activation of CD271 can overcome drug resistance. Aβ^(25-35) was specific to CD271-expressing cells and induced CD271 cleavage and phosphorylation of JNK (pJNK). The direct protein-protein interaction of pJNK with CD271 led to PARP1 cleavage, p53 and caspase activation, and pJNK-dependent cell death. Aβ^(25-35) also mediated mitochondrial reactive oxygen species (mROS) accumulation, which induced CD271 overexpression. Finally, CD271 upregulation inhibited mROS production, revealing the presence of a negative feedback loop in mROS regulation. These results indicate that targeting CD271 can activate cell death pathways to inhibit melanoma progression and potentially overcome resistance to targeted therapy. SIGNIFICANCE: The discovery of a means to specifically activate the CD271 death domain reveals unknown pathways mediated by the receptor and highlights new treatment possibilities for melanoma.

Amyloid-like Self-Assembly of a Hydrophobic Cell-Penetrating Peptide and Its Use as a Carrier for Nucleic Acids

Cell-penetrating peptides (CPPs) are a topical subject potentially exploitable for creating nanotherapeutics for the delivery of bioactive loads. These compounds are often classified into three major categories according to their physicochemical characteristics: cationic, amphiphilic, and hydrophobic. Among them, the group of hydrophobic CPPs has received increasing attention in recent years due to toxicity concerns posed by highly cationic CPPs. The hexapeptide PFVYLI (P, proline; F, phenylalanine; V, valine; Y, tyrosine; L, leucine; and I, isoleucine), a fragment derived from the C-terminal portion of α1-antitrypsin, is a prototypal example of hydrophobic CPP. This sequence shows reduced cytotoxicity and a capacity of nuclear localization, and its small size readily hints at its suitability as a building block to construct nanostructured materials. In this study, we examine the self-assembling properties of PFVYLI and investigate its ability to form noncovalent complexes with nucleic acids. By using a combination of biophysical tools including synchrotron small-angle X-ray scattering and atomic force microscopy-based infrared spectroscopy, we discovered that this CPP self-assembles into discrete nanofibrils with remarkable amyloidogenic features. Over the course of days, these fibrils coalesce into rodlike crystals that easily reach the micrometer range. Despite lacking cationic residues in the composition, PFVYLI forms noncovalent complexes with nucleic acids that retain β-sheet pairing found in amyloid aggregates. In vitro vectorization experiments performed with double-stranded DNA fragments indicate that complexes promote the internalization of nucleic acids, revealing that tropism toward cell membranes is preserved upon complexation. On the other hand, transfection assays with splice-correction oligonucleotides (SCOs) for luciferase expression show limited bioactivity across a narrow concentration window, suggesting that the propensity to form amyloidogenic aggregates may trigger endosomal entrapment. We anticipate that the findings presented here open perspectives for using this archetypical hydrophobic CPP in the fabrication of nanostructured scaffolds, which potentially integrate properties of amyloids and translocation capabilities of CPPs.

"What Doesn't Kill You Makes You Stronger": Future Applications of Amyloid Aggregates in Biomedicine

Amyloid proteins are linked to the pathogenesis of several diseases including Alzheimer's disease, but at the same time a range of functional amyloids are physiologically important in humans. Although the disease pathogenies have been associated with protein aggregation, the mechanisms and factors that lead to protein aggregation are not completely understood. Paradoxically, unique characteristics of amyloids provide new opportunities for engineering innovative materials with biomedical applications. In this review, we discuss not only outstanding advances in biomedical applications of amyloid peptides, but also the mechanism of amyloid aggregation, factors affecting the process, and core sequences driving the aggregation. We aim with this review to provide a useful manual for those who engineer amyloids for innovative medicine solutions.

Interaction of the Anti-Proliferative GPER Inverse Agonist ERα17p with the Breast Cancer Cell Plasma Membrane: From Biophysics to Biology

The peptide ERα17p, which corresponds to the 295-311 fragment of the hinge/AF2 domains of the human estrogen receptor α (ERα), exerts apoptosis in breast cancer cells through a mechanism involving the G protein-coupled estrogen-dependent receptor GPER. Besides this receptor-mediated mechanism, we have detected a direct interaction (Kd value in the micromolar range) of this peptide with lipid vesicles mimicking the plasma membrane of eukaryotes. The reversible and not reversible pools of interacting peptide may correspond to soluble and aggregated membrane-interacting peptide populations, respectively. By using circular dichroism (CD) spectroscopy, we have shown that the interaction of the peptide with this membrane model was associated with its folding into β sheet. A slight leakage of the 5(6)-fluorescein was also observed, indicating lipid bilayer permeability. When the peptide was incubated with living breast cancer cells at the active concentration of 10 μM, aggregates were detected at the plasma membrane under the form of spheres. This insoluble pool of peptide, which seems to result from a fibrillation process, is internalized in micrometric vacuoles under the form of fibrils, without evidence of cytotoxicity, at least at the microscopic level. This study provides new information on the interaction of ERα17p with breast cancer cell membranes as well as on its mechanism of action, with respect to direct membrane effects.