2 | Masaharu Somiya

Engineering of extracellular vesicles for small molecule-regulated cargo loading and cytoplasmic delivery of bioactive proteins

Fri, 20 May 2022 00:00:00 +0000

We established a method for the efficient protein loading into extracellular vesicles. FKBP and FRB pair can bind each other in the presence of a small molecule called rapamycin. FKBP and FRB are fused with CD81(EV marker membrane protein) and protein of interest (POI), respectively, so that POIs can be recruited into EVs in the presence of rapamycin. We confirmed this system worked well to load POIs into EVs and functional delivery using EVs coated with VSV-G which significantly facilitate the cytoplasmic cargo delivery.

Plasmids for this system are available through Addgene.

Find Masaharu Somiya Lab Plasmids

Reporter gene assay for membrane fusion of extracellular vesicles

Mon, 22 Nov 2021 15:00:33 +0000

Extracellular vesicles (EVs) secreted by living cells are expected to deliver biological cargo molecules, including RNA and proteins, to the cytoplasm of recipient cells. There is an increasing need to understand the mechanism of intercellular cargo delivery by EVs. However, the lack of a feasible bioassay has hampered our understanding of the biological processes of EV uptake, membrane fusion, and cargo delivery to recipient cells. Here, we describe a reporter gene assay that can measure the membrane fusion efficiency of EVs during cargo delivery to recipient cells. When EVs containing tetracycline transactivator (tTA)-fused tetraspanins are internalized by recipient cells and fuse with cell membranes, the tTA domain is exposed to the cytoplasm and cleaved by protease to induce tetracycline responsive element (TRE)-mediated reporter gene expression in recipient cells. This assay (designated as EV-mediated tetraspanin-tTA delivery assay, ETTD assay), enabled us to assess the cytoplasmic cargo delivery efficiency of EVs in recipient cells. With the help of a vesicular stomatitis virus-derived membrane fusion protein, the ETTD assay could detect significant enhancement of cargo delivery efficiency of EVs. Furthermore, the ETTD assay could evaluate the effect of potential cargo delivery enhancers/inhibitors. Thus, the ETTD assay may contribute to a better understanding of the underlying mechanism of the cytoplasmic cargo delivery by EVs.

Real-Time Luminescence Assay for Cytoplasmic Cargo Delivery of Extracellular Vesicles

Tue, 23 Mar 2021 15:00:00 +0000

Extracellular vesicles (EVs) have been considered to deliver biological cargos between cells and mediate intercellular communication and potential drug delivery carriers. However, the mechanisms that underlie the biological process of EV uptake and cytoplasmic cargo release in recipient cells are largely unknown. Quantitative and real-time assays for the assessment of cargo delivery efficiency inside recipient cells have not been feasible. In this study, we developed an EV cargo delivery (EVCD) assay using a split luciferase called a NanoBiT system. Recipient cells expressing LgBiT, a large subunit of luciferase, emit luminescence when EV cargo proteins fused with a small luminescence tag (HiBiT tag) that can complement LgBiT are delivered to the cytoplasm of recipient cells. Using the EVCD assay, the cargo delivery efficiency of EVs could be quantitatively measured in real time. This assay was highly sensitive in detecting a single event of cargo delivery per cell. We found that modification of EVs with a virus-derived fusogenic protein significantly enhanced the cytoplasmic cargo delivery; however, in the absence of a fusogenic protein, the cargo delivery efficiency of EVs was below the threshold of the assay. The EVCD assay could assess the effect of entry inhibitors on EV cargo delivery. Furthermore, using a luminescence microscope, the cytoplasmic cargo delivery of EVs was directly visualized in living cells. This assay could reveal the biological mechanism of the cargo delivery processes of EVs.

Cytoplasmic delivery of small interfering RNA by photoresponsive non-cationic liposomes

Thu, 18 Mar 2021 15:00:35 +0000

Small interfering RNA (siRNA) can specifically suppress gene expression by cleaving mRNA in the cytoplasm, termed RNA interference (RNAi). Although a nanoparticle-based siRNA delivery system has been approved for clinical use, the efficiency of cytoplasmic delivery of siRNA is still low. Recently, our group has established a highly efficient siRNA encapsulation method using non-cationic liposomes (LPs), which are more biocompatible than conventional cationic LPs. While non-cationic LPs containing siRNA were taken up by cells in vitro, the cytoplasmic release of siRNA and subsequent phenomena involving RNAi were not observed. It was considered that cytoplasmic delivery of siRNA, and siRNA release from LPs, should occur sequentially. We utilized amphiphilic photosensitizer Al (III) phthalocyanine chloride disulfonic acid (AlPcS2a), which can generate singlet oxygen under exposure to red light. When SK-HEP-1 cells expressing luciferase were treated with non-cationic LPs containing both siRNA and AlPcS2a, RNAi could be observed upon red light exposure, suggesting that singlet oxygen efficiently disrupts the membranous structures of endo/lysosomes and LPs. Thus, the combined use of AlPcS2a and red light is effective for utilizing non-cationic LPs for cytoplasmic delivery of siRNA.

Biocompatibility of highly purified bovine milk-derived extracellular vesicles

Tue, 20 Feb 2018 15:00:41 +0000

Extracellular vesicles (EVs) deliver biologically active cargos from donor cells to recipient cells for intercellular communication. Since the existence of RNA cargo was discovered, EVs have been considered to be useful drug-delivery systems. Specifically, EVs from bovine milk (mEV) are one of the most promising platforms, since bovine milk is a scalable source of EVs for mass production. However, it is still difficult to isolate pure EVs from bovine milk owing to the complexity of raw materials. Furthermore, the biocompatibility and immunotoxicity of mEVs are still unclear. In this study, we developed a new method for isolating bovine milk-derived EVs by employing acid treatment and ultracentrifugation. Isolated mEVs are spherical in shape, measure 120 nm in diameter and contain typical EV marker proteins, such as tetraspanins. Compared with the previously reported method, our method can isolate purer mEVs. When mEVs are contacted with the mouse macrophage cell line Raw264.7, mEVs are readily taken up by the cells without a cytotoxic effect, suggesting that mEVs can deliver the cargo molecules into cells. While systemic administration of mEVs into mice resulted in the absence of systemic toxicity, certain types of cytokines were slightly induced. No anaphylaxis effect was observed after serial administration of mEVs in mice. Thus, mEVs isolated using our method are well tolerated in vivo and may be useful for the drug-delivery application.