No abstract

G protein-coupled receptors (GPCRs) are important drug targets that mediate various signaling pathways by activating G proteins and engaging β-arrestin proteins. Despite its importance for the development of therapeutics with fewer side effects, the underlying mechanism that controls the balance between these signaling modes of GPCRs remains largely unclear. Here, we show that assembly into dimers and oligomers can largely influence the signaling mode of the platelet-activating factor receptor (PAFR). Single-particle analysis results show that PAFR can form oligomers at low densities through two possible dimer interfaces. Stabilization of PAFR oligomers through cross-linking increases G protein activity, and decreases β-arrestin recruitment and agonist-induced internalization significantly. Reciprocally, β-arrestin prevents PAFR oligomerization. Our results highlight a mechanism involved in the control of receptor signaling, and thereby provide important insights into the relationship between GPCR oligomerization and downstream signaling.

Applications of enzymes are intensively studied, particularly for biomedical applications. However, encapsulation or immobilization of enzymes without deactivation and long-term use of enzymes are still at issue. This study focuses on the polymeric vesicles "PICsomes" for encapsulation of enzymes to develop a hecto-nanometer-scaled enzyme-loaded reactor. The catalytic activity of a PICsome-based enzyme nanoreactor is carefully examined to clarify the effect of compartmentalization by PICsome. Encapsulation by PICsome provides a stability enhancement of enzymes after 24 h incubation at 37 °C, which is particularly helpful for maintaining the high effective concentration of β-galactosidase. Moreover, to control the microenvironment inside the nanoreactor, a large amount of dextran, a neutral macromolecule, is encapsulated together with β-galactosidase in the PICsome. The resulting dextran-coloaded nanoreactor contributes to the enhancement of enzyme stability, even after exposure to 24 h incubation at -20 °C, mainly due to the antifreezing effect.

A plasmid DNA and gold nanorods were directly injected to tumor in mice, and the tumor was heated to 39–42 °C through the photothermal effect of the gold nanorods. The heat treatment enhanced transgene expression from the plasmid DNA in the tumor and induced heat shock protein HSP70, related to several immune responses. This transfection technique combined with heat treatment will be applicable to DNA vaccination and gene therapy for immunological diseases.