BTK operates a phospho-tyrosine switch to regulate NLRP3 inflammasome activity

Activity of the NLRP3 inflammasome, a critical mediator of inflammation, is controlled by accessory proteins, posttranslational modifications, cellular localization, and oligomerization. How these factors relate is unclear. We show that a well-established drug target, Bruton’s tyrosine kinase (BTK), affects several levels of NLRP3 regulation. BTK directly interacts with NLRP3 in immune cells and phosphorylates four conserved tyrosine residues upon inflammasome activation, in vitro and in vivo. Furthermore, BTK promotes NLRP3 relocalization, oligomerization, ASC polymerization, and full inflammasome assembly, probably by charge neutralization, upon modification of a polybasic linker known to direct NLRP3 Golgi association and inflammasome nucleation. As NLRP3 tyrosine modification by BTK also positively regulates IL-1β release, we propose BTK as a multifunctional positive regulator of NLRP3 regulation and BTK phosphorylation of NLRP3 as a novel and therapeutically tractable step in the control of inflammation.

Tyrosine-Modification of Polypropylenimine (PPI) and Polyethylenimine (PEI) Strongly Improves Efficacy of siRNA-Mediated Gene Knockdown

The delivery of small interfering RNAs (siRNA) is an efficient method for gene silencing through the induction of RNA interference (RNAi). It critically relies, however, on efficient vehicles for siRNA formulation, for transfection in vitro as well as for their potential use in vivo. While polyethylenimines (PEIs) are among the most studied cationic polymers for nucleic acid delivery including small RNA molecules, polypropylenimines (PPIs) have been explored to a lesser extent. Previous studies have shown the benefit of the modification of small PEIs by tyrosine grafting which are featured in this paper. Additionally, we have now extended this approach towards PPIs, presenting tyrosine-modified PPIs (named PPI-Y) for the first time. In this study, we describe the marked improvement of PPI upon its tyrosine modification, leading to enhanced siRNA complexation, complex stability, siRNA delivery, knockdown efficacy and biocompatibility. Results of PPI-Y/siRNA complexes are also compared with data based on tyrosine-modified linear or branched PEIs (LPxY or PxY). Taken together, this establishes tyrosine-modified PPIs or PEIs as particularly promising polymeric systems for siRNA formulation and delivery.

Bioconjugation of Bacteriophage Pf1 and Extension to Pf1-Based Bionanomaterials

Background: Filamentous bacteriophages such as M13 are an important class of macromolecular assembly, rich in chemical moieties that can be used to impart modifiable positions at the nanoscale. Objective: To explore the structurally more complex Pf1 bacteriophage with respect to a diverse set of bioconjugation reactions and to prepare novel fluorescently-labelled Pf1-based composite biomembranes for future applications in areas such as nanoporous filtration biofilms and photoconducting nanocomposite materials. Methods: Pf1 was characterized with respect to amine (N-terminal, Gly1 and Lys20), carboxylate (aspartate, glutamate), and aromatic (tyrosine) modification and its extension to the creation of functional biomaterials. Modification with an amine reactive fluorophore was carried out with Pf1. Results: The reaction profiles between M13 and Pf1 differ, with M13 capable of modification at two primary amines on its major coat protein, while Pf1 is capable of a single reaction per coat protein. Subsequent to the production of dyefunctionalized Pf1, a biocomposite of wild type and functionalized Pf1 could be fabricated into a bulk material by glutaraldehyde (amine-reactive) crosslinking. These biomaterials were characterized by scanning electron and confocal microscopy, showing a distribution of patches of functionalized Pf1 within the main Pf1 construct. Conclusion: The current study provides a framework for future fabrication of advanced bionanomaterials based on the Pf1 bacteriophage.

A laccase-catalysed tyrosine click reaction

The tyrosine click reaction of peptides/proteins with the tyrosine modification reagent, N-methyl luminol, was catalysed by a laccase in the presence of molecular oxygen (O2) at 37 °C.

BTK operates a phospho-tyrosine switch to regulate NLRP3 inflammasome activity

Activity of the NLRP3 inflammasome, a critical mediator of inflammation (1), is controlled by accessory proteins (2, 3), post-translational modifications (4, 5), cellular localization (6, 7) and oligomerization (8). How these factors relate, is unclear. We show that the established drug target, Bruton’s Tyrosine Kinase (BTK) (2, 9), integrates several levels of NLRP3 regulation: BTK phosphorylation of four conserved tyrosine residues, by neutralizing the charge of a polybasic linker region, weakens the interaction of NLRP3 with Golgi phospholipids and may thus guide NLRP3 cytosolic localization. BTK activity also promotes NLRP3 oligomerization and subsequent formation of inflammasomes. As NLRP3 tyrosine modification ultimately also impacts on IL-1β release, we propose BTK-mediated, charge-switch-based NLRP3 regulation as a novel and therapeutically tractable step in the control of inflammation.One Sentence SummaryMulti-phosphorylation of NLRP3 by Bruton’s tyrosine kinase modulates NLRP3 cellular localization, inflammasome assembly, and IL-1β release.

Polymeric Nanoparticles Based on Tyrosine-Modified, Low Molecular Weight Polyethylenimines for siRNA Delivery

A major hurdle for exploring RNA interference (RNAi) in a therapeutic setting is still the issue of in vivo delivery of small RNA molecules (siRNAs). The chemical modification of polyethylenimines (PEIs) offers a particularly attractive avenue towards the development of more efficient non-viral delivery systems. Here, we explore tyrosine-modified polyethylenimines with low or very low molecular weight (P2Y, P5Y, P10Y) for siRNA delivery. In comparison to their respective parent PEI, they reveal considerably increased knockdown efficacies and very low cytotoxicity upon tyrosine modification, as determined in different reporter and wildtype cell lines. The delivery of siRNAs targeting the anti-apoptotic oncogene survivin or the serine/threonine-protein kinase PLK1 (polo-like kinase 1; PLK-1) oncogene reveals strong inhibitory effects in vitro. In a therapeutic in vivo setting, profound anti-tumor effects in a prostate carcinoma xenograft mouse model are observed upon systemic application of complexes for survivin or PLK1 knockdown, in the absence of in vivo toxicity. We thus demonstrate the tyrosine-modification of (very) low molecular weight PEIs for generating efficient nanocarriers for siRNA delivery in vitro and in vivo, present data on their physicochemical and biological properties, and show their efficacy as siRNA therapeutic in vivo, in the absence of adverse effects.