Protein Chimeras Research Articles

Identification of Potential Interacting Proteins With the Extracellular Loops of the Neuronal Glycoprotein M6a by TMT/MS.

Nowadays, great efforts are made to gain insight into the molecular mechanisms that underlie structural neuronal plasticity. Moreover, the identification of signaling pathways involved in the development of psychiatric disorders aids the screening of possible therapeutic targets. Genetic variations or alterations in GPM6A expression are linked to neurological disorders such as schizophrenia, depression, and Alzheimer’s disease. GPM6A encodes the neuronal surface glycoprotein M6a that promotes filopodia/spine, dendrite, and synapse formation by unknown mechanisms. A substantial body of evidence suggests that the extracellular loops of M6a command its function. However, the proteins that associate with them and that modulate neuronal plasticity have not been determined yet. To address this question, we generated a chimera protein that only contains the extracellular loops of M6a and performed a co-immunoprecipitation with rat hippocampus samples followed by TMT/MS. Here, we report 72 proteins, which are good candidates to interact with M6a’s extracellular loops and modify its function. Gene ontology (GO) analysis showed that 63% of the potential M6a’s interactor proteins belong to the category “synapse,” at both sides of the synaptic cleft, “neuron projections” (51%) and “presynapse” (49%). In this sense, we showed that endogenous M6a interacts with piccolo, synaptic vesicle protein 2B, and synapsin 1 in mature cultured hippocampal neurons. Interestingly, about 28% of the proteins left were related to the “myelin sheath” annotation, suggesting that M6a could interact with proteins at the surface of oligodendrocytes. Indeed, we demonstrated the (cis and trans) interaction between M6a and proteolipid protein (PLP) in neuroblastoma N2a cells. Finally, the 72 proteins were subjected to disease-associated genes and variants screening by DisGeNET. Apart from the diseases that have already been associated with M6a, most of the proteins are also involved in “autistic disorder,” “epilepsy,” and “seizures” increasing the spectrum of disorders in which M6a could play a role. Data are available via ProteomeXchange with identifier PXD017347.

Rab35 Targeting to the Plasma Membrane Is Dependent on the C-terminal Polybasic Cluster

Rab35, a member of the Rab GTPase family, has been implicated in various cellular processes including cell motility and membrane trafficking. Although Rab35 is localized to the plasma membrane, Rab proteins that are identified to have high sequence homology with Rab35 exhibit distinct subcellular localization patterns. Comparing the amino acid sequences between Rab35 and its family members revealed a significant variation in an approximate 30-amino acid region of the C-terminus. This suggests that this region determines the subcellular localization of individual Rab proteins. To confirm this hypothesis, we constructed Rab35–Rab10 chimera proteins by exchanging their C-terminal domains with one another. Confocal microscopy of RAW264 cells expressing EGFP-fused Rab35–Rab10 chimeras has indicated that the C-terminal region of Rab35 is critical for its plasma membrane localization. Furthermore, we were able to determine that a basic amino acid cluster exists in the C-terminal region of Rab35 and that Rab35 localization shifts to the Golgi membrane when the number of basic amino acids in this region is reduced. Thus, it is likely that the approximate 30-amino acid C-terminal region containing basic clusters is responsible for Rab35 plasma membrane localization and that its preferential localization depends on the number of basic amino acids.

Design, expression, purification and crystallization of human 14-3-3ζ protein chimera with phosphopeptide from proapoptotic protein BAD

14-3-3 protein isoforms regulate multiple processes in eukaryotes, including apoptosis and cell division. 14-3-3 proteins preferentially recognize phosphorylated unstructured motifs, justifying the protein-peptide binding approach to study 14-3-3/phosphotarget complexes. Tethering of human 14-3-3σ with partner phosphopeptides via a short linker has provided structural information equivalent to the use of synthetic phosphopeptides, simultaneously facilitating purification and crystallization. Nevertheless, the broader applicability to other 14-3-3 isoforms and phosphopeptides was unclear. Here, we designed a novel 14-3-3ζ chimera with a conserved phosphopeptide from BAD, whose complex with 14-3-3 is a gatekeeper of apoptosis regulation. The chimera could be bacterially expressed and purified without affinity tags. Co-expressed PKA efficiently phosphorylates BAD within the chimera and blocks its interaction with a known 14-3-3 phosphotarget, suggesting occupation of the 14-3-3 grooves by the tethered BAD phosphopeptide. Efficient crystallization of the engineered protein suggests suitability of the “chimeric” approach for studies of other relevant 14-3-3 complexes.

The speed of FtsZ treadmilling is tightly regulated by membrane binding

As one of the key elements in bacterial cell division, the cytoskeletal protein FtsZ appears to be highly involved in circumferential treadmilling along the inner membrane, yielding circular vortices when transferred to flat membranes. However, it remains unclear how a membrane-targeted protein can produce these dynamics. Here, we dissect the roles of membrane binding, GTPase activity, and the unstructured C-terminal linker on the treadmilling of a chimera FtsZ protein through in vitro reconstitution of different FtsZ-YFP-mts variants on supported membranes. In summary, our results suggest substantial robustness of dynamic vortex formation, where only significant mutations, resulting in abolished membrane binding or compromised lateral interactions, are detrimental for the generation of treadmilling rings. In addition to GTPase activity, which directly affects treadmilling dynamics, we found a striking correlation of membrane binding with treadmilling speed as a result of changing the MTS on our chimera proteins. This discovery leads to the hypothesis that the in vivo existence of two alternative tether proteins for FtsZ could be a mechanism for controlling FtsZ treadmilling.

A Bioorthogonal Click Chemistry Toolbox for Targeted Synthesis of Branched and Well-Defined Protein-Protein Conjugates.

Bioorthogonal chemistry holds great potential to generate difficult‐to‐access protein–protein conjugate architectures. Current applications are hampered by challenging protein expression systems, slow conjugation chemistry, use of undesirable catalysts, or often do not result in quantitative product formation. Here we present a highly efficient technology for protein functionalization with commonly used bioorthogonal motifs for Diels–Alder cycloaddition with inverse electron demand (DAinv). With the aim of precisely generating branched protein chimeras, we systematically assessed the reactivity, stability and side product formation of various bioorthogonal chemistries directly at the protein level. We demonstrate the efficiency and versatility of our conjugation platform using different functional proteins and the therapeutic antibody trastuzumab. This technology enables fast and routine access to tailored and hitherto inaccessible protein chimeras useful for a variety of scientific disciplines. We expect our work to substantially enhance antibody applications such as immunodetection and protein toxin‐based targeted cancer therapies.

First-in-human phase I study of ARV-110, an androgen receptor (AR) PROTAC degrader in patients (pts) with metastatic castrate-resistant prostate cancer (mCRPC) following enzalutamide (ENZ) and/or abiraterone (ABI).

3500 Background: Proteolysis Targeting Chimera (PROTAC) protein degraders induce selective degradation of targeted proteins by engaging the ubiquitin proteasome system. ARV-110 is an orally bioavailable PROTAC that specifically degrades AR ≥ 95% and achieves anti-tumor activity in ENZ-naïve and -resistant prostate cancer xenograft models. Methods: To define the maximum tolerated dose (MTD) and recommended phase 2 dose (RP2D) of ARV-110, pts with ≥ 2 prior therapies for mCRPC, including ENZ and/or ABI, received ARV-110 orally once daily. Dose escalation is per 3+3 design. Endpoints include dose limiting toxicities (DLTs), adverse events (AEs), pharmacokinetics (PK), biomarkers (e.g., AR mutation analysis), RECIST and PSA response. Results: By January 2020, 18 pts were dosed: 35 mg (N = 3), 70 mg (N = 4), 140 mg (N = 8), 280 mg (N = 3). 12 pts received both ENZ and ABI; 14 received prior chemotherapy. 1 of 18 pts experienced a DLT (280 mg) of Grade (Gr) 4 elevated AST/ALT followed by acute renal failure while taking rosuvastatin (ROS). A 2nd pt had Gr 3 AST/ALT with ROS that resolved off ROS, permitting ARV-110 retreatment. ROS plasma concentrations demonstrated significant increases concurrent with AST/ALT elevations in both pts. Subsequently, ROS was prohibited without further ≥Gr 2 AST/ALT AEs. No other related Gr 3/4 AEs were reported. ARV-110 PK was generally dose proportional and at 140 mg reached levels associated with preclinical anti-tumor activity. 15 pts were evaluable for PSA response (excludes 1 pt stopped after 1 dose for early progression and 2 pts initiated 2 weeks before cutoff, all at 140 mg). Of these, 8 pts initiated dosing at ≥140 mg. 2 pts achieved confirmed PSA declines of >50%, both at 140 mg. Prior therapy in both pts included ENZ and ABI, chemotherapy, bicalutamide and radium-223 plus other regimens. 1 pt had 2 AR mutations known to confer ENZ resistance. The 2nd pt also achieved an unconfirmed RECIST partial response (confirmatory scan pending). Both responses were ongoing at data cutoff (8+ and 21+ weeks of treatment). Conclusions: To date, ARV-110 has an acceptable safety profile. Concurrent ROS is now prohibited. MTD has not yet been established; determination of RP2D continues. ARV-110 demonstrates antitumor activity in mCRPC after ENZ/ABI with 2 ongoing confirmed PSA responses, one of which was associated with tumor reduction. Updated data for this first PROTAC in clinical testing will be presented. Clinical trial information: NCT03888612 .

C-terminal of ABCA1 separately regulates cholesterol floppase activity and cholesterol efflux activity.

ATP-Binding Cassette A1 (ABCA1) is a key lipid transporter for cholesterol homeostasis. We recently reported that ABCA1 not only exports excess cholesterol in an apoA-I dependent manner, but that it also flops cholesterol from the inner to the outer leaflet of the plasma membrane. However, the relationship between these two activities of ABCA1 is still unclear. In this study, we analyzed the subcellular localization of ABCA1 by using a newly generated monoclonal antibody against its extracellular domain and the functions of eleven chimera proteins, in which the C-terminal domain of ABCA1 was replaced with those of the other ABCA subfamily members. We identified two motifs important for the functions of ABCA1. Three periodically repeated leucine residues were necessary for the cholesterol floppase activity but not the cholesterol efflux activity, while a VFVNFA motif was essential for both activities of ABCA1. These results suggest that the C-terminal of ABCA1 separately regulates the cholesterol floppase activity and the cholesterol efflux activity.

Synthetic antibodies against BRIL as universal fiducial marks for single\u2212particle cryoEM structure determination of membrane proteins

We propose the concept of universal fiducials based on a set of pre-made semi-synthetic antibodies (sABs) generated by customized phage display selections against the fusion protein BRIL, an engineered variant of apocytochrome b562a. These sABs can bind to BRIL fused either into the loops or termini of different GPCRs, ion channels, receptors and transporters without disrupting their structure. A crystal structure of BRIL in complex with an affinity-matured sAB (BAG2) that bound to all systems tested delineates the footprint of interaction. Negative stain and cryoEM data of several examples of BRIL-membrane protein chimera highlight the effectiveness of the sABs as universal fiducial marks. Taken together with a cryoEM structure of sAB bound human nicotinic acetylcholine receptor, this work demonstrates that these anti-BRIL sABs can greatly enhance the particle properties leading to improved cryoEM outcomes, especially for challenging membrane proteins.

An in vitro and in vivo study of the brain-targeting effects of an epidermal growth factor-functionalized cholera toxin-like chimeric protein

The development of neuroprotective drugs has proven to be extremely difficult because of the blood-brain barrier. Intranasal administration is thought to transport the drug from the nasal cavity along the olfactory and trigeminal nerves to the brain, thus bypassing the blood-brain barrier. However, macromolecular protein drugs have low delivery efficiency via this route in general. We hypothesized that an innocuous cholera toxin-like chimeric protein could better enhance the efficiency of protein delivery through the intranasal route. To test this hypothesis, we designed an enhanced green fluorescent protein (EGFP) chimera to evaluate the effect of the cholera toxin (CT) as a carrier for drug delivery into the brain. Then, the EGFP was replaced with epidermal growth factor (EGF) in the chimeric protein, and the therapeutic effect of the new chimeric protein was studied in an LPS-induced neuritis mouse model. The results suggest that the CT-like chimeric protein can bypass the blood-brain barrier and enter the brain in approximately 30 min. This EGF chimeric protein can effectively protect the spatial cognitive ability of and confer anti-anxiety protection to mice. The results indicate that cholera toxin-like chimeric proteins are potential tools for effectively delivering macromodecular drugs into the brain through intranasal administration.

Selectin-Binding Assay by Flow Cytometry.

Cell-cell interactions mediated by selectins and their ligand glycans play pivotal roles in a variety of biological processes represented by leukocyte recruitment to inflammatory sites, lymphocyte homing, and extravasation of cancer cells. The interactions are enhanced at least partly through the upregulation of the selectin-ligand glycan expression, which is observed, for instance, during the activation of leukocytes or epithelial-mesenchymal transition of cancer cells. Selectin-binding assays such as cell adhesion assay or rolling assay have long been used to directly evaluate the activity of these cells in the selectin-mediated processes. In this chapter, we introduce a highly quantitative assay by flow cytometry using recombinant selectin-Ig(Fc) chimera proteins, showing our procedure and tips for E-selectin-binding assay of colon cancer cells undergoing epithelial-mesenchymal transition.

A thermo-responsive, self-assembling biointerface for on demand release of surface-immobilised proteins.

Dedicated chemistries for on-demand capture and release of biomolecules at the solid-liquid interface are required for applications in drug delivery, for the synthesis of switchable surfaces used in analytical devices and for the assembly of next-generation biomaterials with complex architectures and functions. Here we report the engineering of a binary self-assembling polypeptide system for reversible protein capture, immobilisation and controlled thermo-responsive release from a solid surface. The first element of the binary system is a universal protein substrate immobilised on a solid surface. This protein is bio-inspired by the neuronal SNAP25, which is the protein involved in the docking and fusion of synaptic vesicles to the synaptic membrane. The second element is an artificial chimeric protein engineered to include distinct domains from three different proteins: Syntaxin, VAMP and SNAP25. These native proteins constitute the machinery dedicated to vesicle trafficking in eukaryotes. We removed approximately 70% of native protein sequence from these proteins and constructed a protein chimera capable of high affinity interaction and self-assembly with immobilised substrate. The interaction of the two parts of the engineered protein complex is strong but fully-reversible and therefore the chimera can be recombinantly fused as a tag to a protein of interest, to allow spontaneous assembly and stimuli-sensitive release from the surface upon heating at a predetermined temperature. Two thermo-responsive tags are reported: the first presents remarkable thermal stability with melting temperature of the order of 80 °C; the second disassembles at a substantially lower temperature of about 45 °C. The latter is a promising candidate for remote-controlled localised delivery of therapeutic proteins, as physiologically tolerable local increase of temperatures in the 40-45 °C range can be achieved using magnetic fields, infra-red light or focused ultrasound. Importantly, these two novel polypeptides provide a broader blueprint for the engineering of future functional proteins with predictable folding and response to external stimuli.

Comprehensive engineering of the tarantula venom peptide huwentoxin-IV to inhibit the human voltage-gated sodium channel hNav1.7

Comprehensive engineering of the tarantula venom peptide huwentoxin-IV to inhibit the human voltage-gated sodium channel hNav1.7

Molecular Dynamics Simulation of Transmembrane Transport of Chloride Ions in Mutants of Channelrhodopsin.

Channelrhodopsins (ChRs) are light-gated transmembrane cation channels which are widely used for optogenetic technology. Replacing glutamate located at the central gate of the ion channel with positively charged amino acid residues will reverse ion selectivity and allow anion conduction. The structures and properties of the ion channel, the transport of chloride, and potential of mean force (PMF) of the chimera protein (C1C2) and its mutants, EK-TC, ER-TC and iChloC, were investigated by molecular dynamics simulation. The results show that the five-fold mutation in E122Q-E129R-E140S-D195N-T198C (iChloC) increases the flexibility of the transmembrane channel protein better than the double mutations in EK-TC and ER-TC, and results in an expanded ion channel pore size and decreased steric resistance. The iChloC mutant was also found to have a higher affinity for chloride ions and, based on surface electrostatic potential analysis, provides a favorable electrostatic environment for anion conduction. The PMF free energy curves revealed that high affinity Cl− binding sites are generated near the central gate of the three mutant proteins. The energy barriers for the EK-TC and ER-TC were found to be much higher than that of iChloC. The results suggest that the transmembrane ion channel of iChloC protein is better at facilitating the capture and transport of chloride ions.

BAFF is involved in the pathogenesis of IgA nephropathy by activating the TRAF6/NF‑κB signaling pathway in glomerular mesangial cells.

The aim of the present study was to investigate the involvement of B cell-activating factor (BAFF) in the pathogenesis of IgA nephropathy by activating the tumor necrosis factor receptor-associated factor 6 (TRAF6)/NF-κB signaling pathway in glomerular mesangial cells. For the clinical analysis, blood, urine and kidney tissue samples were collected from 58 patients diagnosed with primary IgA nephropathy by renal biopsy. For the in vitro study, glomerular mesangial cells were divided into five groups: Control (con)-short hairpin RNA (shRNA) (control group); con-shRNA + BAFF (20 ng/ml); con-shRNA + BAFF + BAFF-RFc chimera protein (500 µg/ml); TRAF6-shRNA; and TRAF6-shRNA + BAFF (20 ng/ml). For the in vivo experiments, 60 Sprague-Dawley rats were randomly divided into four groups: Con-small interfering RNA (siRNA) (control group); con-siRNA + IgA (IgA nephropathy group), BAFF-RFc chimera protein (2 µg/ml) + IgA, and TRAF6-siRNA (0.2 µM) + IgA. Reverse transcription-quantitative PCR was performed to evaluate the mRNA expression levels of TRAF6, connective tissue growth factor (CTGF), fibronectin (FN) and NF-κBP65. Western blot analysis was used to detect the protein expression levels of TRAF6, FN, CTGF and phosphorylated-NF-κBP65 in glomerular mesangial cells and kidney tissues. The results revealed that plasma BAFF levels were positively correlated with the severity of pathological damage in patients with IgA nephropathy. In vitro, BAFF induced the mRNA and protein expression of TRAF6, CTGF, FN and NF-κBP65 in glomerular mesangial cells. After the BAFF-RFc chimera protein was added to inhibit the binding of BAFF and BAFF-receptor (-R), this effect was reduced. In vivo, inhibition of the effects of BAFF via injection with the BAFF-R Fc chimera protein reduced kidney damage in rats suffering from IgA nephropathy. The effect on the expression of signaling pathway-associated proteins was also alleviated. In conclusion, BAFF enhanced the expression of fibroblast factors in the kidneys by activating the TRAF6/NF-κB signaling pathway.

Efficacy of echinomycin in hypoxia‐inducible factor‐mediated ocular angiogenesis

AbstractPurposeEchinomycin (EKN), an inhibitor of hypoxia‐inducible factor (HIF)‐1 DNA‐binding activity, has been implied as a possible therapeutic agent in ischemic diseases. We assessed EKN in hypoxia‐driven responses in vitro using human primary adult retinal pigment epithelium cells (aRPE), and in vivo using the laser‐induced mouse choroidal neovascularization (CNV) model.MethodsAdult retinal endothelial were kept at normoxia (20% O2) or exposed to hypoxia (1% O2), in the presence or absence of EKN. Epithelial wound‐healing was used to determine the dose of EKN. Effects of EKN on hypoxia‐mediated pathways were analyzed by western blot for HIF‐1a, qPCR of HIF‐target genes, and proteome array for soluble angiogenic factors. Inhibition of angiogenesis by EKN was determined in human primary adult retinal endothelial cells (aREC), exposed to EKN‐treated hypoxic conditioned aRPE medium by spheroid sprouting assay. 8‐week‐old C57BL/6J mice underwent laser‐induced CNV, as a model of HIF‐associated ocular neovascularization. Animals were treated with EKN and compared to a mouse VEGFR1‐Fc chimera protein (equivalent of aflibercept). CNV lesion area was determined by fluorescein angiography.ResultsAdult retinal endothelial treated with EKN demonstrated hypoxia‐dependent decreased cell proliferation in the wound‐healing assay. Lower HIF‐mediated transcripts were detected in hypoxic aRPE cells treated with EKN compared with non‐treated controls. These results were confirmed by proteome profiler for angiogenic factors, and subsequently reduced hREC sprouting. Laser‐induced mice treated with 1 mg of intravitreally injected EKN demonstrated a significant decrease in vascular lesion area when compared with 1 mg of VEGFR1 chimera or vehicle‐treated controls.ConclusionsOur data suggest EKN as a potent inhibitor of HIF‐mediated angiogenesis in retinal cells and in the mouse model of CNV, which could have future implications in the treatment of patients with neovascular age‐related macular degeneration.

Oncostatin M Is a Novel Niche Factor That Restrains Hematopoietic Stem Cell Mobilization in Response to G-CSF and CXCR4 Antagonist Plerixafor

Granulocyte colony-stimulating factor (G-CSF) and the CXCR4 chemokine receptor antagonist Plerixafor are used to mobilize hematopoietic stem and progenitor cells (HSPC). However, in the autologous setting, prior chemotherapy and radiotherapy impair HSPC mobilizing response to G-CSF and Plerixafor thereby precluding autologous HSC transplantation. We now demonstrate in mice that oncostatin M (OSM) production in the bone marrow (BM) is dramatically increased in response to G-CSF and that OSM counteracts the mobilizing effect of G-CSF and Plerixafor indirectly through the BM stroma. Indeed, by immunohistochemistry, a 4-day G-CSF treatment strongly increased OSM protein expression in cell clusters containing F4/80+ macrophages in the endosteal and central region of the mobilized BM. OSM concentration was 7-fold higher in BM fluids of G-CSF mobilized mice compared to control mice as measured by ELISA. To investigate OSM effects on HSPC mobilization, C57BL/6 mice (WT) and mice lacking the OSM receptor gene (OSMR-/-) were treated with 125 μg/kg human G-CSF bidaily for 2-6 days and/or Plerixafor (10 mg/kg) one hour before harvest. Absence of OSMR increased HSPC mobilization with a 4-fold increase in colony forming cells (CFC), phenotypic Lin-Kit+Sca1+ HSPC (LKS+ cells) and LKS+Flt3-CD48-CD150+ HSC into the blood at days 2 and 4 of G-CSF treatment and increased accumulation of HSPC and HSC in the spleen of OSMR-/- mice at day 6 of G-CSF treatment. In a competitive repopulation assay with serial dilutions of mobilized blood, deletion of OSMR gene enhanced ≈4-fold mobilization of functional reconstituting HSC in response to G-CSF as shown by Poisson's distribution analysis. HSPC mobilization in response to Plerixafor was also significantly enhanced with a doubling of CFC, HSPC and HSC into the blood of OSMR-/- mice compared to WT. OSMR gene deletion also significantly enhanced HSPC mobilization (3-fold) in response to G-CSF plus Plerixafor combination, the most effective mobilization regimen currently approved. To further demonstrate that endogenous OSM restrains HSPC mobilization in response to G-CSF, we produced a recombinant mouse OSM-trap, a dimeric protein chimera made of the extracellular domain of mouse OSMR and mouse gp130 fused with a mutant Fc fragment of mouse IgG2a. Co-administration of this OSM-trap together with G-CSF also increased HSPC and HSC mobilization into the blood in response to G-CSF compared to mice treated with G-CSF and control trap construct. This negative effect of endogenous OSM on HSPC mobilization was indirectly mediated by BM stromal cells. qRT-PCR on BM myeloid and stromal cells sorted from steady-state or mobilized mice showed that Osm mRNA is mostly expressed by CD11b+F4/80+CD169+VCAM1+ macrophages and CD11b+F4/80-Ly6G+ neutrophils. In sharp contrast, Osmr mRNA was undetectable in any sorted BM leukocyte population, but abundantly expressed by CD45-Lin-CD31+Sca1+CD105+ endothelial and CD45-Lin-CD31-CD51+PDGFRα+/-Sca-1+/- mesenchymal progenitor cells. OSMR protein was expressed by vascular beds in the BM as detected by IHC. Confirming the indirect effect of OSM, we found that recombinant OSM had no effect on HSPC chemotaxis in response to CXCL12, or HSPC adhesion to immobilized VCAM-1 or selectins in vitro. However, HSPC freshly isolated from the BM of OSMR-/- mice had enhanced chemotaxis in response to CXCL12 compared to HSPC isolated from WT mice. In conclusion, G-CSF increases OSM expression in the BM, and this appears to restrain HSPC mobilization in response to G-CSF via OSMR-expressing endothelial and mesenchymal cells that decreases HSPC responsiveness to CXCL12 gradient. Disclosures Winkler: GlycoMimetics: Patents & Royalties. Levesque:GlycoMimetics: Equity Ownership.

In Vitro Monolayer Culture of Dispersed Neural Stem Cells on the E-Cadherin-Based Substrate with Long-Term Stemness Maintenance.

Neural stem cells (NSCs) play an important role in neural tissue engineering because of their capacity of self-renewal and differentiation to multiple cell lineages. The in vitro conventional neurosphere culture protocol has some limitations such as limited nutrition and oxygen penetration and distribution causing the heterogeneity of cells inside, inaccessibility of internal cells, and inhomogeneous cellular morphology and properties. As a result, cultivation as a monolayer is a better way to study NSCs and obtain a homogeneous cell population. The cadherins are a classical family of homophilic cell adhesion molecules mediating cell-cell adhesion. Here, we used a recombinant human E-cadherin mouse IgG Fc chimera protein that self-assembles on a hydrophobic polystyrene surface via hydrophobic interaction to obtain an E-cadherin-coated culture plate (ECP). The rat fetal NSCs were cultured on the ECP and routine tissue culture plate (TCP) from passage 2 to passage 5. NSCs on TCP formed uniform floating neurospheres and grew up over time, while cells on the ECP adhered on the bottom of the plate and exhibited individual cells with scattering morphology, forming intercellular connections between cells. The cell proliferation and differentiation behaviors that were evaluated by Cell Counting Kit-8 assay (CCK-8), immunofluorescence staining, and real-time quantitative polymerase chain reaction showed NSCs could maintain the capacity for self-renewal and ability to differentiate into neurons, oligodendrocytes, and astrocytes after the long-term in vitro cell culture and passaging. Therefore, our study indicated that hE-cad-Fc could provide a homogeneous environment for individual cells in monolayer conditions to maintain the capacity of self-renewal and differentiation by mimicking the cell–cell interaction.

HER3-targeted protein chimera forms endosomolytic capsomeres and self-assembles into stealth nucleocapsids for systemic tumor homing of RNA interference in vivo.

RNA interference represents a potent intervention for cancer treatment but requires a robust delivery agent for transporting gene-modulating molecules, such as small interfering RNAs (siRNAs). Although numerous molecular approaches for siRNA delivery are adequate in vitro, delivery to therapeutic targets in vivo is limited by payload integrity, cell targeting, efficient cell uptake, and membrane penetration. We constructed nonviral biomaterials to transport small nucleic acids to cell targets, including tumor cells, on the basis of the self-assembling and cell-penetrating activities of the adenovirus capsid penton base. Our recombinant penton base chimera contains polypeptide domains designed for noncovalent assembly with anionic molecules and tumor homing. Here, structural modeling, molecular dynamics simulations, and functional assays suggest that it forms pentameric units resembling viral capsomeres that assemble into larger capsid-like structures when combined with siRNA cargo. Pentamerization forms a barrel lined with charged residues mediating pH-responsive dissociation and exposing masked domains, providing insight on the endosomolytic mechanism. The therapeutic impact was examined on tumors expressing high levels of HER3/ErbB3 that are resistant to clinical inhibitors. Our findings suggest that our construct may utilize ligand mimicry to avoid host attack and target the siRNA to HER3+ tumors by forming multivalent capsid-like structures.

E-cadherin-Fc chimera protein matrix enhances cancer stem-like properties and induces mesenchymal features in colon cancer cells.

Cancer stem cells (CSC) are a subpopulation of tumor cells with properties of high tumorigenicity and drug resistance, which lead to recurrence and poor prognosis. Although a better understanding of CSC is essential for developing cancer therapies, scarcity of the CSC population has hindered such analyses. The aim of the present study was to elucidate whether the E‐cadherin‐Fc chimera protein (E‐cad‐Fc) enhances cancer stem‐like properties because studies show that soluble E‐cadherin stimulates human epithelial growth factor receptor (EGFR) and downstream signaling pathways that are reported to play a crucial role in CSC. For this purpose, we used ornithine decarboxylase (ODC)‐degron–transduced (Degron(+)) KM12SM cells as a CSC model that retains relatively low CSC properties. Compared to cultures without E‐cad‐Fc treatment, we found that E‐cad‐Fc treatment further suppressed proteasome activity and largely enhanced cancer stem‐like properties of ODC‐degron–transduced KM12SM cells. These results include increased expression of stem cell markers Lgr5, Bmi‐1, SOX9, CD44, and CD44v9, aldehyde dehydrogenase (ALDH), and enhancement of robust spheroid formation, and chemoresistance to 5‐fluorouracil (5‐FU) and oxaliplatin (L‐OHP). These effects could be attributed to activation of the EGFR pathway as identified by extensive phosphorylation of EGFR, ERK, PI3K, AKT, and mTOR. In SW480 cells, E‐cad‐Fc matrix induced some CSC markers such as CD44v9 and ALDH. We also found that E‐cad‐Fc matrix showed high efficiency of inducing mesenchymal changes in colon cancer cells. Our data suggest that the E‐cad‐Fc matrix may enhance CSC properties such as enhancement of chemoresistance and sphere formation.

Luciferase‐Induced Photouncaging: Bioluminolysis

AbstractBioluminescence resonance energy transfer (BRET) has been widely used for studying dynamic processes in biological systems such as protein–protein interactions and other signaling events. Aside from acting as a reporter, BRET can also turn on functions in living systems. Herein, we report the application of BRET to performing a biorthogonal reaction in living cells; namely, releasing functional molecules through energy transfer to a coumarin molecule, a process termed bioluminolysis. An efficient BRET from Nanoluc‐Halotag chimera protein (H‐Luc) to a coumarin substrate yields the excited state of coumarin, which in turn triggers hydrolysis to uncage a target molecule. Compared to the conventional methods, this novel uncaging system requires no external light source and shows fast kinetics (t1/2<2 min). We applied this BRET uncaging system to release a potent kinase inhibitor, ibrutinib, in living cells, highlighting its broad utility in controlling the supply of bioactive small molecules in vivo.