Journal of Peptide Science最新文献

Protein–protein interactions (PPIs) have been recognized as a promising target for the development of new drugs, as proved by the growing number of PPI modulators reaching clinical trials. In this context, peptides represent a valid alternative to small molecules, owing to their unique ability to mimic the target protein structure and interact with wider surface areas. Among the possible fields of interest, bacterial PPIs represent an attractive target to face the urgent necessity to fight antibiotic resistance. Growing attention has been paid to the YgjD/YeaZ/YjeE complex responsible for the essential t⁶A₃₇ tRNA modification in bacteria. We previously identified an α-helix on the surface of Pseudomonas aeruginosa YeaZ, crucial for the YeaZ-YeaZ homodimer formation and the conserved YeaZ-YgjD interactions. Herein, we present our studies for impairing the PPIs involved in the formation of the YeaZ dimers through synthetic peptide derivatives of this helical moiety, both in vitro with purified components and on P. aeruginosa cells. Our results proved the possibility of targeting those PPIs which are usually essential for protein functioning and thus are refractory to mutational changes and antibiotic resistance development.

Chemical synthesis of complex peptides and proteins continues to play increasingly important roles in industry and academia, where strategies for covalent ligation of two or more peptide fragments to produce longer peptides and proteins in convergent manners have become critical. In recent decades, efficient and site-selective ligation strategies mediated by exploiting the biocatalytic capacity of nature's diverse toolkit (i.e., enzymes) have been widely recognized as a powerful extension of existing chemical strategies. In this review, we present a chronological overview of the development of proteases, transpeptidases, transglutaminases, and ubiquitin ligases. We survey the different properties between the ligation reactions of various enzymes, including the selectivity and efficiency of the reaction, the ligation “scar” left in the product, the type of amide bond formed (natural or isopeptide), the synthetic availability of the reactants, and whether the enzymes are orthogonal to another. This review also describes how the inherent specificity of these enzymes can be exploited for peptide and protein ligation.

The melanocortin 4 receptor (MC4R) plays a critical role in satiety and energy homeostasis, and its dysregulation is implicated in numerous hyperphagic and obese disease states. Setmelanotide, a disulfide-based cyclic peptide, can rescue MC4R activity and treat obesities caused by genetic defects in MC4R signaling. But this peptide has moderate blood–brain barrier penetrance and metabolic stability, which can limit its efficacy in practice. Based on the cryo-electron microscopy structure of setmelanotide-bound MC4R, we hypothesized that replacing its lone disulfide bond with more metabolically stable and permeability-enhancing carbon-based linker groups could improve pharmacokinetic properties without abolishing activity. To test this, we used chemistry developed by our lab to prepare 11 carbocyclic (alkyl, aryl, perfluoroalkyl, and ethereal) analogs of setmelanotide and determined their biochemical potencies at MC4R in vitro. Ten analogs displayed full agonism, showing that disulfide replacement is tolerant of linkers ranging in size, rigidity, and functional groups, with heteroatom- or aryl-rich linkers displaying superior potencies.

Antimicrobial peptides (AMPs) are a promising source of new compounds against resistant bacteria. Temporins are a class of AMPs found on the amphibian Rana temporaria and show activity against Gram-positive and Gram-negative bacteria. There are few studies on how these antimicrobials have been used, but new Temporin-F derivatives were engineered with Lys-substitutions to assess the impact of the net charge on antimicrobial activity and toxicity. We demonstrated through some assays that it is possible to increase the antibacterial activity while maintaining a reduced peptide hemolytic activity with specific substitutions. Our lead synthetic peptide, G6K-Temporin F, has shown higher antimicrobial activity against Gram-negative and Gram-positive bacteria in vitro (MIC range 2 to 32 μmol L⁻¹), with low hemolytic activity maintained, resulting in an increase in the therapeutic window (TW), of 12.5. Also, it showed more resistant to enzymatic degradation. On the other hand, more significant increases in net charges, such as in P3K-G11K-Temporin F, result in a severe increase in toxicity with lower gains in antimicrobial activity (TW of 0.65). In conclusion, we demonstrated that a moderate increase in net charge can lead to a more active analog and G6K-Temporin F is revealed to be promising as a candidate for new AMP therapeutics.

Self-assembling peptide hydrogels (SAPHs) have been used in the past decade as reliable three-dimensional (3D) synthetic scaffolds for the culture of a variety of mammalian cells in vitro. Thanks to their versatile physicochemical properties, they allow researchers to tailor the hydrogel properties, including stiffness and functionality to the targeted cells and cells' behaviour. One of the advantages of using SAPH scaffolds is the ease of functionalisation. In the present work, we discuss the effect that functionalising the FEFEFKFK (F, phenylalanine; K, lysine; and E, glutamic acid) hydrogel scaffold using the cell-binding RGDS (fibronectin — R, arginine; G, glycine; D, aspartic acid; S, serine) epitope affects the material properties as well as the function of encapsulated human osteoblast cells. RGDS functionalisation resulted in cells adopting an elongated morphology, suggesting attachment and increased proliferation. While this led to higher cell viability, it also resulted in a decrease in extra-cellular matrix (ECM) protein production as well as a decrease in calcium ion deposition, suggesting lower mineralisation capabilities. The work clearly shows that SAPHs are a flexible platform that allow the modification of scaffolds in a controlled manner to investigate cell–material interactions.

Radiolabeled peptides play a key role in nuclear medicine to selectively deliver radionuclides to malignancies for diagnosis (imaging) and therapy. Yet, their efficiency is often compromised by low metabolic stability. The use of 1,4-disubstituted 1,2,3-triazoles (1,4-Tzs) as stable amide bond bioisosteres can increase the half-life of peptides in vivo while maintaining their biological properties. Previously, the amide-to-triazole substitution strategy was used for the stabilization of the pansomatostatin radioligand [¹¹¹In]In-AT2S, resulting in the mono-triazolo-peptidomimetic [¹¹¹In]In-XG1, a radiotracer with moderately enhanced stability in vivo and retained ability to bind multiple somatostatin receptor (SSTR) subtypes. However, inclusion of additional 1,4-Tz led to a loss of affinity towards SST₂R, the receptor overexpressed by most SSTR-positive cancers. To enhance further the stability of [¹¹¹In]In-XG1, alternative modifications at the enzymatically labile position Thr¹⁰-Phe¹¹ were employed. Three novel 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-peptide conjugates were synthesized with a 1,4-Tz (Asn⁵-Ψ[Tz]-Phe⁶) and either a β-amino acid (β-Phe¹¹), reduced amide bond (Thr¹⁰-Ψ[NH]-Phe¹¹), or N-methylated amino acid (N-Me-Phe¹¹). Two of the new peptidomimetics were more stable in blood plasma in vitro than [¹¹¹In]In-XG1. Yet none of them retained high affinity towards SST₂R. We demonstrate for the first time the combination of the amide-to-triazole substitution strategy with alternative stabilization methods to improve the metabolic stability of tumor-targeting peptides.

Supramolecular hydrogels, particularly low-molecular-weight peptide hydrogels, are promising drug delivery systems due to their ability to change the solubility, targeting, metabolism and toxicity of drugs. Magneto-plasmonic liposomes, in addition to being remotely controllable with the application of an external magnetic field, also increase the efficiency of encapsulated drug release through thermal stimulation, for example, with magnetic and optical hyperthermia. Thus, the combination of those two materials—giving magneto-plasmonic lipogels—brings together several functionalities, among which are hyperthermia and spatiotemporally controlled drug delivery. In this work, a novel dehydrodipeptide hydrogelator was synthesised, and the respective hydrogel was functionalized with magneto-plasmonic liposomes. After individually characterising the components with regard to their rheological, spectroscopic and magnetic properties, the magneto-plasmonic lipogel was equally characterised and evaluated concerning its ability to deliver drugs in a controlled fashion. To this end, the response of the 5(6)-carboxyfluorescein-loaded magneto-plasmonic lipogel to near-infrared light was assessed. The results showed that the system is a proper carrier of hydrophilic drugs and allows to envisage photo-responsive drug delivery. These facts, together with the magnetic guidance and hyperthermia capabilities of the developed composite gel, may pave the way to a new era in the treatment of cancer and other diseases.

Peptides have attracted great interest as platforms for the design of nanocomposite hydrogels due to their distinct bioactivity, biofunctionality and biocompatibility. Previously, we have reported on a family of peptides that self-assembled to form stabilised three-dimensional hydrogel networks, displaying potent antimicrobial activity. In this paper, we report on the use of these hydrogelator sequences and their analogues as stabilisers and growth controllers to synthesise anisotropic gold nanoparticles (AuNPs) of different sizes and shapes. In particular, hollow spherical nanoparticles were obtained for HG2.81-AuNPs, whereas hexagonal nanoparticles were observed for TOH_1N-AuNPs and PentaOH-AuNPs in their respective hydrogel networks. The PentaOH-AuNPs' hydrogel exhibited excellent results with high antimicrobial potency against Staphylococcus aureus and Pseudomonas aeruginosa ATCC 27853 and negligible cytotoxicity. On the other hand, TOH_1N-AuNPs showed no antibacterial activity and no cytotoxicity, demonstrating the versatility of these peptides. This work gives credence towards the development of these materials towards further applications such as in tissue culture technology and wound dressing materials.

Liraglutide (LGT) is a synthetic glucagon-like peptide-1 analogue mainly used for the treatment of type-2 diabetes or obesity. Comprehensive stability testing is essential in the development and routine quality control of synthetic therapeutic peptide pharmaceuticals. The GLP-1 peptide drugs are usually formulated in aqueous-base solution, which can generate stability issues during manufacturing, storage or shipment. The current study endeavors to observe the chemical stability behavior of LGT by exposing the drug substance to oxidative and hydrolytic stress conditions. A simple liquid chromatography (LC) method was developed where sufficient resolution between LGT and the generated degradation products was achieved. In total, 19 degradation products (DPs) were separated under acidic, basic and oxidative stress conditions. Using LC-HRMS, MS/MS studies, the generated degradation products were identified and characterized. The mechanistic fragmentation pathway for all generated DPs were established and the plausible chemical structure for the identified DPs was predicted based on MS/MS data. The results strongly suggest that LGT is highly susceptible to degrade under oxidative and hydrolytic conditions. Furthermore, this study provides insights into the hydrolytic and oxidative stability of LGT, which can be implied during generic and novel formulation drug development and discovery in synthesizing relatively stable GLP-1 analogues.