Lactate oxidase/catalase-displaying nanoparticles efficiently consume lactate in the tumor microenvironment to effectively suppress tumor growth.

The aggressive proliferation of tumor cells often requires increased glucose uptake and excessive anaerobic glycolysis, leading to the massive production and secretion of lactate to form a unique tumor microenvironment (TME). Therefore, regulating appropriate lactate levels in the TME would be a promising approach to control tumor cell proliferation and immune suppression. To effectively consume lactate in the TME, lactate oxidase (LOX) and catalase (CAT) were displayed onto Aquifex aeolicus lumazine synthase protein nanoparticles (AaLS) to form either AaLS/LOX or AaLS/LOX/CAT. These complexes successfully consumed lactate produced by CT26 murine colon carcinoma cells under both normoxic and hypoxic conditions. Specifically, AaLS/LOX generated a large amount of H2O2 with complete lactate consumption to induce drastic necrotic cell death regardless of culture condition. However, AaLS/LOX/CAT generated residual H2O2, leading to necrotic cell death only under hypoxic condition similar to the TME. While the local administration of AaLS/LOX to the tumor site resulted in mice death, that of AaLS/LOX/CAT significantly suppressed tumor growth without any severe side effects. AaLS/LOX/CAT effectively consumed lactate to produce adequate amounts of H2O2 which sufficiently suppress tumor growth and adequately modulate the TME, transforming environments that are favorable to tumor suppressive neutrophils but adverse to tumor-supportive tumor-associated macrophages. Collectively, these findings showed that the modular functionalization of protein nanoparticles with multiple metabolic enzymes may offer the opportunity to develop new enzyme complex-based therapeutic tools that can modulate the TME by controlling cancer metabolism.

Load and Display: Engineering Encapsulin as a Modular Nanoplatform for Protein-Cargo Encapsulation and Protein-Ligand Decoration Using Split Intein and SpyTag/SpyCatcher.

Protein cage nanoparticles have a unique spherical hollow structure that provides a modifiable interior space and an exterior surface. For full application, it is desirable to utilize both the interior space and the exterior surface simultaneously with two different functionalities in a well-combined way. Here, we genetically engineered encapsulin protein cage nanoparticles (Encap) as modular nanoplatforms by introducing a split-C-intein (IntC) fragment and SpyTag into the interior and exterior surfaces, respectively. A complementary split-N-intein (IntN) was fused to various protein cargoes, such as NanoLuc luciferase (Nluc), enhanced green fluorescent protein (eGFP), and Nluc-miniSOG, individually, which led to their successful encapsulation into Encaps to form Cargo@Encap through split intein-mediated protein ligation during protein coexpression and cage assembly in bacteria. Conversely, the SpyCatcher protein was fused to various protein ligands, such as a glutathione binder (GST-SC), dimerizing ligands (FKBP12-SC and FRB-SC), and a cancer-targeting affibody (SC-EGFRAfb); subsequently, they were displayed on Cargo@Encaps through SpyTag/SpyCatcher ligation to form Cargo@Encap/Ligands in a mix-and-match manner. Nluc@Encap/glutathione-S-transferase (GST) was effectively immobilized on glutathione (GSH)-coated solid supports exhibiting repetitive and long-term usage of the encapsulated luciferases. We also established luciferase-embedded layer-by-layer (LbL) nanostructures by alternately depositing Nluc@Encap/FKBP12 and Nluc@Encap/FRB in the presence of rapamycin and applied enhanced green fluorescent protein (eGFP)@Encap/EGFRAfb as a target-specific fluorescent imaging probe to visualize specific cancer cells selectively. Modular functionalization of the interior space and the exterior surface of a protein cage nanoparticle may offer the opportunity to develop new protein-based nanostructured devices and nanomedical tools.

Development of Recombinant Immunoglobulin G-Binding Luciferase-Based Signal Amplifiers in Immunoassays.

In general immunoassays, secondary antibodies are covalently linked with enzymes and bind to the Fc region of target-bound primary antibodies to amplify signals of low-abundant target molecules. The antibodies themselves are obtained from large mammals and are further modified with enzymes. In this study, we developed novel recombinant immunoglobulin G (IgG)-binding luciferase-based signal amplifiers (rILSAs) by genetically fusing luciferase (Nluc) with antimouse IgG1 nanobody (MG1Nb) and antibody-binding domain (ABD), individually or together, in a mix-and-match manner. We obtained three different highly pure rILSAs in large quantities using a bacterial overexpression system and one-step purification. Mouse-specific rILSA, MG1Nb-Nluc, and rabbit-specific rILSA, Nluc-ABD, selectively bound to target-molecule-bound mouse IgG1 and rabbit IgG primary antibodies, whereas the bispecific rILSA, MG1Nb-Nluc-ABD, mutually bound to both mouse IgG1 and rabbit IgG primary antibodies. All rILSAs exhibited an outstanding signal-amplifying capability comparable to those of conventional horseradish-peroxidase-conjugated secondary antibodies, regardless of the target molecules, in various immunoassay formats, such as enzyme-linked immunosorbent assay, Western blot, and lateral flow assays. Each rILSA was selected for its own individual purpose and applied to various types of target analytes, in combination with a variety of target-specific primary antibodies, effectively minimizing the use of animals as well as reducing the costs and time associated with the production and chemical conjugation of signal-amplifying enzymes.

Development of target-tunable P22 VLP-based delivery nanoplatforms using bacterial superglue.

Protein cage nanoparticles are widely used as targeted delivery nanoplatforms, because they have well-defined symmetric architectures, high biocompatibility, and enough plasticity to be modified to produce a range of different functionalities. Targeting peptides and ligands are often incorporated on the surface of protein cage nanoparticles. In this research, we adopted the SpyTag/SpyCatcher protein ligation system to covalently display target-specific affibody molecules on the exterior surface of bacteriophage P22 virus-like particles (VLP) and evaluated their modularity and efficacy of targeted delivery. We genetically introduced the 13 amino acid SpyTag peptide into the C-terminus of the P22 capsid protein to construct a target-tunable nanoplatform. We constructed two different SpyCatcher-fused affibody molecules as targeting ligands, SC-EGFRAfb and SC-HER2Afb, which selectively bind to EGFR and HER2 surface markers, respectively. We produced target-specific P22 VLP-based delivery nanoplatforms for the target cell lines by selectively combining SpyTagged P22 VLP and SC-fused affibody molecules. We confirmed its target-switchable modularity through cell imaging and verified the target-specific drug delivery efficacy of the affibody molecules displaying P22 VLP using cell viability assays. The P22 VLP-based delivery nanoplatforms can be used as multifunctional delivery vehicles by ligating other functional proteins, as well as affibody molecules. The interior cavity of P22 VLP can be also used to load cargoes like enzymes and therapeutic proteins. We anticipate that the nanoplatforms will provide new opportunities for developing target-specific functional protein delivery systems.

Fabrication of Nanoreaction Clusters with Dual-Functionalized Protein Cage Nanobuilding Blocks.

Fabrication of functional nanostructures is a prominent issue in nanotechnology, because they often exhibit unique properties that are different from the individual building blocks. Protein cage nanoparticles are attractive nanobuilding blocks for constructing nanostructures due to their well-defined symmetric spherical structures, polyvalent nature, and functional plasticity. Here, a lumazine synthase protein cage nanoparticle is genetically modified to be used as a template to generate functional nanobuilding blocks and covalently display enzymes (ß-lactamase) and protein ligands (FKBP12/FRB) on its surface, making dual-functional nanobuilding blocks. Nanoreaction clusters are subsequently created by ligand-mediated alternate deposition of two complementary building blocks using layer-by-layer (LbL) assemblies. 3D nanoreaction clusters provide enhanced enzymatic activity compared with monolayered building block arrays. The approaches described here may provide new opportunities for fabricating functional nanostructures and nanoreaction clusters, leading to the development of new protein nanoparticle-based nanostructured biosensor devices.

Protein Cage Nanoparticles as Delivery Nanoplatforms.

Protein cage nanoparticles are made of biomaterials, proteins, and have well-defined cage-like architectures designed and built by nature. They are composed of multiple copies of one or a small number of chemically identical subunits having a highly uniform nano-size and symmetric structure. Protein cage nanoparticles have genetic and chemical plasticity amenable to simultaneously introducing multiple cell-specific targeting ligands, diagnostic agents, and their corresponding therapeutic agents at desired sites depending on its purpose. A wide range of protein cage nanoparticles, such as ferritin, lumazine synthase, encapsulin, and virus-like particles, has been extensively explored and utilized in biomedical fields as effective delivery nanoplatforms of diagnostics and/or therapeutics. Highly biocompatible and plastic protein cage nanoparticles may provide a new paradigm for developing simple, but versatile in vivo delivery systems.

Lactate oxidase/vSIRPα conjugates efficiently consume tumor-produced lactates and locally produce tumor-necrotic H2O2 to suppress tumor growth.

Aggressive tumor formation often leads to excessive anaerobic glycolysis and massive production and accumulation of lactate in the tumor microenvironment (TME). To significantly curb lactate accumulation in TME, in this study, lactate oxidase (LOX) was used as a potential therapeutic enzyme and signal regulatory protein α variant (vSIRPα) as a tumor cell targeting ligand. SpyCatcher protein and SpyTag peptide were genetically fused to LOX and vSIRPα, respectively, to form SC-LOX and ST-vSIRPα and tumor-targeting LOX/vSIRPα conjugates were constructed via a SpyCatcher/SpyTag protein ligation system. LOX/vSIRPα conjugates selectively bound to the CD47-overexpressing mouse melanoma B16-F10 cells and effectively consumed lactate produced by the B16-F10 cells, generating adequate amounts of hydrogen peroxide (H2O2), which induces drastic necrotic tumor cell death. Local treatments of B16-F10 tumor-bearing mice with LOX/vSIRPα conjugates significantly suppressed B16-F10 tumor growth in vivo without any severe side effects. Tumor-targeting vSIRPα may allow longer retention of LOX in tumor sites, effectively consuming surrounding lactate in TME and locally generating adequate amounts of cytotoxic H2O2 to suppress tumor growth. The approach restraining the local lactate concentration and H2O2 in TME using LOX and vSIRPα could offer new opportunities for developing enzyme/targeting ligand conjugate-based therapeutic tools for tumor treatment.

Application of periostin peptide-decorated self-assembled protein cage nanoparticles for therapeutic angiogenesis.

Peptides are gaining substantial attention as therapeutics for human diseases. However, they have limitations such as low bioavailability and poor pharmacokinetics. Periostin, a matricellular protein, can stimulate the repair of ischemic tissues by promoting angiogenesis. We have previously reported that a novel angiogenic peptide (amino acids 142-151) is responsible for the pro-angiogenic activity of periostin. To improve the in vivo delivery efficiency of periostin peptide (PP), we used proteins self-assembled into a hollow cage-like structure as a drug delivery nanoplatform in the present study. The periostin peptide was genetically inserted into lumazine synthase (isolated from Aquifex aeolicus) consisting of 60 identical subunits with an icosahedral capsid architecture. The periostin peptide-bearing lumazine synthase protein cage nanoparticle with 60 periostin peptides multivalently displayed was expressed in Escherichia coli and purified to homogeneity. Next, we examined angiogenic activities of this periostin peptide-bearing lumazine synthase protein cage nanoparticle. AaLS-periostin peptide (AaLS-PP), but not AaLS, promoted migration, proliferation, and tube formation of human endothelial colony-forming cells in vitro. Intramuscular injection of PP and AaLS-PP increased blood perfusion and attenuated severe limb loss in the ischemic hindlimb. However, AaLS did not increase blood perfusion or alleviate tissue necrosis. Moreover, in vivo administration of AaLS-PP, but not AaLS, stimulated angiogenesis in the ischemic hindlimb. These results suggest that AaLS is a highly useful nanoplatform for delivering pro-angiogenic peptides such as PP. [BMB Reports 2022; 55(4): 175-180].

Construction of SARS-CoV-2 virus-like particles in plant.

The pandemic of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has caused a public health emergency, and research on the development of various types of vaccines is rapidly progressing at an unprecedented development speed internationally. Some vaccines have already been approved for emergency use and are being supplied to people around the world, but there are still many ongoing efforts to create new vaccines. Virus-like particles (VLPs) enable the construction of promising platforms in the field of vaccine development. Here, we demonstrate that non-infectious SARS-CoV-2 VLPs can be successfully assembled by co-expressing three important viral proteins membrane (M), envelop (E) and nucleocapsid (N) in plants. Plant-derived VLPs were purified by sedimentation through a sucrose cushion. The shape and size of plant-derived VLPs are similar to native SARS-CoV-2 VLPs without spike. Although the assembled VLPs do not have S protein spikes, they could be developed as formulations that can improve the immunogenicity of vaccines including S antigens, and further could be used as platforms that can carry S antigens of concern for various mutations.

Target-switchable Gd(III)-DOTA/protein cage nanoparticle conjugates with multiple targeting affibody molecules as target selective T1 contrast agents for high-field MRI.

Magnetic resonance imaging (MRI) is a non-invasive in vivo imaging tool, providing high enough spatial resolution to obtain both the anatomical and the physiological information of patients. However, MRI generally suffers from relatively low sensitivity often requiring the aid of contrast agents (CA) to enhance the contrast of vessels and/or the tissues of interest from the background. The targeted delivery of diagnostic probes to the specific lesion is a powerful approach for early diagnosis and signal enhancement leading to the effective treatment of various diseases. Here, we established targeting ligand switchable nanoplatforms using lumazine synthase protein cage nanoparticles derived from Aquifex aeolicus (AaLS) by genetically introducing the SpyTag peptide (ST) to the C-terminus of the AaLS subunits to form an ST-displaying AaLS (AaLS-ST). Conversely, multiple targeting ligands were constructed by genetically fusing SpyCatcher protein (SC) to either HER2 or EGFR targeting affibody molecules (SC-HER2Afb or SC-EGFRAfb). Gd(III)-DOTA complexes were chemically attached to the AaLS-ST and the external surface of the Gd(III)-DOTA conjugated AaLS-ST (Gd(III)-DOTA-AaLS-ST) were successfully decorated with either the HER2Afb or the EGFRAfb. The resulting Gd(III)-DOTA-AaLS/HER2Afb and Gd(III)-DOTA-AaLS/EGFR2Afb exhibited high r1 relaxivity values of 57 and 25 mM-1 s-1 at 1.4 and 7 T, respectively, which were 10-fold or higher than those of the clinically used Dotarem. Their target-selective contrast enhancements were confirmed with in vitro cell-based MRI scans and the in vivo MR imaging of tumor-bearing mouse models at 7 T. A target-switchable AaLS-based nanoplatform that was developed in this study might serve as a promising T1 CA developing platform at a high magnetic field to detect various tumor sites in a target-specific manner in future clinical applications.

Rhamnogalacturonan-I-Type Polysaccharide Purified from Broccoli Exerts Anti-Metastatic Activities Via Innate Immune Cell Activation.

To examine the anti-metastatic activities of polysaccharides in broccoli, purified polysaccharides (BCE-I, -II, and -III) were isolated by fractionation of broccoli enzyme extracts and subsequent ethanol precipitation. BCE-I mainly consisted of galactose and arabinose, whereas BCE-II mainly consisted of galacturonic acid and rhamnose, and BCE-III mainly consisted of rhamnose and galactose. Of the three fractions, stimulation of murine peritoneal macrophages by BCE-I showed the greatest enhancement of tumor necrosis factor-α, interleukin (IL)-12, and IL-6 secretion. In addition, intravenous (i.v.) administration of BCE-I enhanced the lethal activity of natural killer (NK) cells on YAC-1 tumor cells significantly and dose-dependently in an ex vivo experiment of NK cell activity. In an experimental model using lung metastasis of Colon26-M3.1 carcinoma cells, prophylactic i.v. and oral administration of BCE-I significantly and dose-dependently inhibited lung metastatic activity. Furthermore, the inhibitory activity of BCE-1 on lung metastasis partially disappeared when NK cell function was removed through treatment of rabbit anti-asialo GM1. These results indicated that BCE-I has potent antitumor metastatic activity, and that its anti-metastatic activity has relevance to the stimulation of NK and other immune cells.

Signaling pathway and structural features of macrophage-activating pectic polysaccharide from Korean citrus, Cheongkyool peels.

To characterize the immuno-stimulating ingredient from the Korean citrus, Cheongkyool, a crude polysaccharide (CCE-0) was isolated from the pectinase digests of Cheongkyool peels, from which the complex polysaccharide CCE-I was purified to homogeneity by gel filtration. CCE-I highly enhanced the production of IL-6, TNF-α, and NO in RAW 264.7 cell lines. It augmented the mRNA expression of IL-6, TNF-α, and iNOS in a dose-dependent manner. Moreover, CCE-I dose-dependently induced phosphorylation of MAPKs and NF-κB related proteins and led to the nuclear translocation of p65. The effect of CCE-I on NO and IL-6 production was suppressed by treatment with specific antibodies for TLR2, TLR4, and scavenger receptors. Conversely, the primary structure of CCE-I that exhibited potent immunostimulatory activity was characterized by sugar composition, linkage analysis, and oligosaccharide analysis after ß-elimination. The results suggested that CCE-I may be a rhamnogalacturonan-I type, highly branched polysaccharide with short arabinan and galactan side chains.