Journal of Peptide Science最新文献

Recently, we presented cell-permeable CaaX peptides as versatile tools to study intracellular prenylation of proteins. These peptides consist of a cell-penetrating peptide (CPP) and a C-terminal CaaX motif derived from Ras proteins and demonstrated high cellular accumulation and the ability to influence Ras signaling in cancerous cells. Here, we aimed to gain a deeper insight into how such cell-permeable CaaX peptides, particularly the KRas4B-derived CaaX-1 peptide, interact with farnesyltransferase (FTase) and likely influence further intracellular processes. We show that CaaX-1 is farnesylated by FTase ex cellulo and that an intact CaaX motif is required for modification. A competition experiment revealed a slower farnesylation of CaaX-1 by FTase compared to a CaaX motif-containing control peptide. CaaX-1 inhibited farnesylation of this control peptide at considerably lower concentrations; thus, a higher affinity for FTase is hypothesized. Notably, AlphaFold3 not only predicted interactions between CaaX-1 and FTase but also suggested interactions between the peptide and geranylgeranyltransferase type I. This finding encourages further investigation, as cross-prenylation is a well-known drawback of FTase inhibitors. Our results are further evidence for the usefulness of CaaX peptides as tools to study and manipulate the prenylation of proteins. They offer real potential for the development of novel inhibitors targeting the prenylation pathway.

Marine organisms serve as a rich source of bioactive natural compounds, including antimicrobial agents. Jellyfish, which are ancient marine invertebrates with hundreds of millions of years of evolutionary history, have been in continuous contact with a diverse array of pathogenic microorganisms from seawater, which may give rise to a distinctive innate immune system and related defensive molecules. However, it is difficult and inefficient to isolate active ingredients directly from jellyfish for enrichment, though few jellyfish-sourced antimicrobial peptides (AMPs) have been reported. In this study, we utilized transcriptomic big data with bioinformatic tools to dig deeper into potential antimicrobial components in jellyfish, and identified a new AMP JFP-2826 from Rhopilema esculentum. The 20-mer peptide exhibited an alpha-helix structure and showed antimicrobial activity against selected bacterial strains; more importantly, JFP-2826 demonstrated good selectivity for marine-specific Vibrio including Vibrio vulnificus. Sequence analysis of the full-length protein of JFP-2826 revealed that it is derived from the housekeeping gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH), which is probably produced through enzymatic cleavage of the N-terminal fragment. This suggests that GAPDH of jellyfish might have a newly discovered antimicrobial-related function that is conducted by releasing JFP-2826-like cryptic peptides. JFP-2826 can be subjected to further structural modifications and optimizations to potentially become a potent lead peptide for the development of novel antimicrobial drugs treating infections of marine pathogens.

This study investigated a peptide-based GRP78-targeting strategy for short-interfering (si) RNA delivery in cancer cells. Synthetic fluorescein-labeled amphiphilic peptides composed of the hydrophobic cell surface (cs) GRP78-targeting and hydrophilic, polycationic arginine-rich cell penetrating peptides demonstrated GRP78-dependent cell uptake in the DU145 prostate cancer cells, and to a lesser extent in the non-cancerous human lung fibroblast WI-38 cell line. Mechanistic studies revealed energy-dependent GRP78 receptor-mediated endocytosis of the GRP78-targeting peptide with polyarginine (W1-R9). The cytosolic accumulation of this peptide underscored its potential utility in siRNA delivery. Peptide:siRNA complexes formed stably condensed nanoparticles, with calcium functioning as an ionic stabilizer and additive promoting endosomal siRNA escape for RNA interference (RNAi) activity. Preliminary peptide-based siRNA transfections in the DU145 cells demonstrated that GRP78 knockdown led to an interplay in between pro-survival and cell death outcomes under ER stress induction. Thus, the GRP78-targeting polyarginine peptides enables efficient cell uptake for specific siRNA delivery in the DU145 cells. This class of bio-active synthetic peptides is important for the investigation of cancer biology, leading to the innovation of cancer-targeted gene delivery and therapy approaches.

Antibody mimetic peptides have evolved as versatile tools for biomedical applications, based on their ability to interfere with protein–protein interactions. We had previously designed a functional mimic of the broadly neutralizing HIV-1 antibody b12 that recognizes the CD4 binding site of the HIV-1 envelope glycoprotein gp120. The molecular details of the interaction of a linear variant of this peptide (H1H3s) with gp120 have now been characterized through cross-linking mass spectrometry, confirming the proposed involvement of the CD4 binding site of gp120 in the interaction. In addition, a variant of the b12 mimetic peptide composed mostly of D-amino acids was shown to be stable towards proteolytic degradation, while the binding and HIV-1 neutralizing properties were largely preserved. Furthermore, a peptide variant in which aspartate residues were replaced with lysine was shown to strongly enhance infection of cells with HIV-1 and GALV glycoprotein pseudotyped viral vectors, respectively, introducing this peptide as a tool to facilitate retroviral gene transfer. Collectively, the presented results highlight the versatile potential therapeutic and gene transfer applications of H1H3s and its variants in particular, as well as antibody mimetic peptides in general.

Peptides and proteins have become increasingly important in the treatment of various diseases, including infections, metabolic disorders, and cancers. Over the past decades, the number of approved peptide- and protein-based drugs has grown significantly, now accounting for about 25% of the global pharmaceutical market. This increase has been recorded since the introduction of the first therapeutic peptide, insulin, in 1921. Therapeutic peptides and proteins offer several advantages over small molecule drugs, including high specificity, potency, and safety; however, they also face challenges related to instability in liquid formulations. To address this issue, numerous formulation techniques have been developed to enhance their stability. In either state, physical and chemical characterization of the peptide or protein of interest is crucial for ensuring the identity, purity, and activity of these therapeutic agents. Regulatory bodies such as the FDA, ICH, and EMA have established guidelines for the analysis, stability testing, and quality control of peptides and biologics to ensure the safety and effectiveness of these drugs. In the present review, these guidelines and the consequences thereof are summarized and provided to support the notion of developing tailored bioanalytical workflows for each peptide or protein drug.