Liposome nanoparticle conjugation and cell penetrating peptide sequences (CPPs) enhance the cellular delivery of the tau aggregation inhibitor RI-AG03

Given the pathological role of Tau aggregation in Alzheimer's disease (AD), our laboratory previously developed the novel Tau aggregation inhibitor peptide, RI-AG03. As Tau aggregates accumulate intracellularly, it is essential that the peptide can traverse the cell membrane. Here we examine the cellular uptake and intracellular trafficking of RI-AG03, in both a free and liposome-conjugated form. We also characterize the impact of adding the cell-penetrating peptide (CPP) sequences, polyarginine (polyR) or transactivator of transcription (TAT), to RI-AG03. Our data show that liposome conjugation of CPP containing RI-AG03 peptides, with either the polyR or TAT sequence, increased cellular liposome association three-fold. Inhibition of macropinocytosis modestly reduced the uptake of unconjugated and RI-AG03-polyR-linked liposomes, while having no effect on RI-AG03-TAT-conjugated liposome uptake. Further supporting macropinocytosis-mediated internalization, a 'fair' co-localisation of the free and liposome-conjugated RI-AG03-polyR peptide with macropinosomes and lysosomes was observed. Interestingly, we also demonstrate that RI-AG03-polyR detaches from liposomes following cellular uptake, thereby largely evading organellar entrapment. Collectively, our data indicate that direct membrane penetration and macropinocytosis are key routes for the internalization of liposomes conjugated with CPP containing RI-AG03. Our study also demonstrates that peptide-liposomes are suitable nanocarriers for the cellular delivery of RI-AG03, furthering their potential use in targeting Tau pathology in AD.

Live-Cell Visualization of DNA Transfer and Pilus Dynamics During Bacterial Conjugation

Bacterial genomes are highly plastic and evolve rapidly by acquiring new genetic information through horizontal gene transfer mechanisms. Capturing DNA transfer by conjugation between bacterial cells in real time is relevant to address bacterial genomes' dynamic architecture comprehensively. Here, we describe a method allowing the direct visualization of bacterial conjugation in live cells, including the fluorescent labeling of the conjugative pilus and the monitoring of plasmid DNA transfer from donor to recipient cells.

Design, Synthesis, and Evaluation of N- and C-Terminal Protein Bioconjugates as G Protein-Coupled Receptor Agonists

A G protein-coupled receptor (GPCR) agonist protein, thaumatin, was site-specifically conjugated at the N- or C-terminus with a fluorophore for visualization of GPCR:agonist interactions. The N-terminus was specifically conjugated using a synthetic 2-pyridinecarboxyaldehyde reagent. The interaction profiles observed for N- and C-terminal conjugates were varied; N-terminal conjugates interacted very weakly with the GPCR of interest, whereas C-terminal conjugates bound to the receptor. These chemical biology tools allow interactions of therapeutic proteins:GPCR to be monitored and visualized. The methodology used for site-specific bioconjugation represents an advance in application of 2-pyridinecarboxyaldehydes for N-terminal specific bioconjugations.