Advances in recombinant protein expression for use in pharmaceutical research

Enhanced Recombinant Protein Expression in Insect Cells by Natural and Recombinant Components of Lepidoptera Hemolymph

Prior research has established the anti-apoptotic effects in insect cell cultures of Bombyx mori (B. mori) hemolymph, as well as the heightened production yields of recombinant proteins facilitated by baculovirus vectors in insect cells cultivated in media supplemented with this hemolymph. In this study, we investigated the hemolymph of another Lepidoptera species, Trichoplusia ni (T. ni), and observed similar beneficial effects in insect cells cultivated in media supplemented with this natural substance. We observed enhancements in both production yield (approximately 1.5 times higher) and late-stage cell viabilities post-infection (30-40% higher). Storage-protein 2 from B. mori (SP2Bm) has previously been identified as one of the abundant hemolymph proteins potentially responsible for the beneficial effects observed after the use of B. mori hemolymph-supplemented cell culture media. By employing a dual baculovirus vector that co-expresses the SP2Bm protein alongside the GFP protein, we achieved a threefold increase in reporter protein production compared to a baculovirus vector expressing GFP alone. This study underscores the potential of hemolymph proteins sourced from various Lepidoptera species as biotechnological tools to augment baculovirus vector productivities, whether utilized as natural supplements in cell culture media or as hemolymph-derived recombinant proteins co-expressed by baculovirus vectors.

Optimizing Recombinant Cas9 Expression: Insights from E. coli BL21(DE3) Strains for Enhanced Protein Purification and Genome Editing

The CRISPR-Cas9 system is a revolutionary tool in genetic engineering, offering unprecedented precision and efficiency in genome editing. Cas9, an enzyme derived from bacteria, is guided by RNA to edit DNA sequences within cells precisely. However, while CRISPR-Cas9 presents notable benefits and encouraging outcomes as a molecular tool and a potential therapeutic agent, the process of producing and purifying recombinant Cas9 protein remains a formidable hurdle. In this study, we systematically investigated the expression of recombinant SpCas9-His in four distinct Escherichia coli (E. coli) strains (Rosetta2, BL21(DE3), BL21(DE3)-pLysS, and BL21(DE3)-Star). Through optimization of culture conditions, including temperature and post-induction time, the BL21(DE3)-pLysS strain demonstrated efficient SpCas9 protein expression. This study also presents a detailed protocol for the purification of recombinant SpCas9, along with detailed troubleshooting tips. Results indicate successful SpCas9 protein expression using E. coli BL21(DE3)-pLysS at 0.5 mM IPTG concentration. Furthermore, the findings suggest potential avenues for further enhancements, paving the way for large-scale Cas9 production. This research contributes valuable insights into optimizing E. coli strains and culture conditions for enhanced Cas9 expression, offering a step forward in the development of efficient genome editing tools and therapeutic proteins.

A Step-by-Step Guide for the Production of Recombinant Fluorescent TAT-HA-Tagged Proteins and their Transduction into Mammalian Cells

Investigating the function of target proteins for functional prospection or therapeutic applications typically requires the production and purification of recombinant proteins. The fusion of these proteins with tag peptides and fluorescently derived proteins allows the monitoring of candidate proteins using SDS-PAGE coupled with western blotting and fluorescent microscopy, respectively. However, protein engineering poses a significant challenge for many researchers. In this protocol, we describe step-by-step the engineering of a recombinant protein with various tags: TAT-HA (trans-activator of transduction-hemagglutinin), 6×His and EGFP (enhanced green fluorescent protein) or mCherry. Fusion proteins are produced in E. coli BL21(DE3) cells and purified by immobilized metal affinity chromatography (IMAC) using a Ni-nitrilotriacetic acid (NTA) column. Then, tagged recombinant proteins are introduced into cultured animal cells by using the penetrating peptide TAT-HA. Here, we present a thorough protocol providing a detailed guide encompassing every critical step from plasmid DNA molecular assembly to protein expression and subsequent purification and outlines the conditions necessary for protein transduction technology into animal cells in a comprehensive manner. We believe that this protocol will be a valuable resource for researchers seeking an exhaustive, step-by-step guide for the successful production and purification of recombinant proteins and their entry by transduction within living cells. © 2024 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: DNA cloning, molecular assembly strategies, and protein production Basic Protocol 2: Protein purification Basic Protocol 3: Protein transduction in mammalian cells.

A Versatile Method for Inducible Protein Production in 293 Cells Using the PiggyBac Transposon System

The production of recombinant proteins has helped in understanding of their function and developing new therapies. However, one of the major bottlenecks for protein production is the establishment of reliable mammalian cell lines with high expression levels. In this chapter, we describe a simple and robust system that allows for the quick establishment of stable transgenic 293 cell lines with reproducible and high protein expression levels. This methodology is based on the piggyBac transposon system and enables the inducible production of the protein of interest. Finally, this methodology can easily be used in conventional laboratory cell culture settings without requiring specialized devices.

Production of Bioactive Human PAX4 Protein from E. coli

Paired box 4 (PAX4) is a pivotal transcription factor involved in pancreatogenesis during embryogenesis, and in adults, it is key for β-cell proliferation and survival. Additionally, PAX4 also functions as a tumor suppressor protein in human melanomas. The present study demonstrates the production of bioactive recombinant human PAX4 transcription factor. At first, the inserts (PAX4 protein-coding sequence having tags at either ends) were cloned in an expression vector to give rise to pET28a(+)-HTN-PAX4 and pET28a(+)-PAX4-NTH genetic constructs, and these were then transformed into Escherichia coli (E. coli) for their expression. The HTN-PAX4 and PAX4-NTH fusion proteins produced were purified with a yield of ~ 3.15 mg and ~ 0.83 mg, respectively, from 1.2 L E. coli culture. Further, the secondary structure retention of the PAX4 fusion proteins and their potential to internalize the mammalian cell and its nucleus was demonstrated. The bioactivity of these fusion proteins was investigated using various assays (cell migration, cell proliferation and cell cycle assays), demonstrating it to function as a tumor suppressor protein. Thus, this macromolecule can prospectively help understand the function of human PAX4 in cellular processes, disease-specific investigations and direct cellular reprogramming.

Establishment of a Pseudovirus Platform for Neuraminidase Inhibiting Antibody Analysis

Neuraminidase (NA)-based immunity to influenza can be useful for protecting against novel antigenic variants. To develop safe and effective tools to assess NA-based immunity, we generated a baculovirus-based pseudotyped virus, N1-Bac, that expresses the full-length NA of the influenza A/California/07/2009 (H1N1)pdm09 strain. We evaluated the level of NA-inhibiting (NI) antibodies in the paired blood sera of influenza patients by means of an enzyme-linked lectin assay (ELLA) using the influenza virus or N1-Bac. Additionally, we evaluated the level of NA antibodies by means of the enzyme-linked immunosorbent assay (ELISA) with an N1-expressing Sf21 culture. We detected a strong correlation between our results from using the influenza virus and NA-Bac pseudoviruses to detect NI antibodies and a medium-strong correlation between NI antibodies and NA antibodies determined by an N1-cell ELISA, indicating that baculovirus-based platforms can be successfully used to evaluate NI or NA antibodies. Furthermore, animal experiments showed that immunization with N1-Bac protected against infection with a drift variant of the A/H1N1pdm09 influenza virus. Our results demonstrate that recombinant baculovirus can be an effective influenza pseudotype to evaluate influenza serologic immunity and protect against influenza virus infection.

Recombinant Protein Production Using the Baculovirus Expression Vector System (BEVS)

The baculovirus expression vector system (BEVS) is one of the most popular eukaryotic systems for recombinant protein production. The focus of our protein production platform is the provision of recombinant proteins for research use, where generally only small quantities are required, in the range of tens of micrograms to a few hundred milligrams. Here, we present methods that reflect our standard operating procedures and setup to be able to frequently, and often repeatedly, produce many different types of proteins.

Synthetic Biology: Bottom-Up Assembly of Molecular Systems

The bottom-up assembly of biological and chemical components opens exciting opportunities to engineer artificial vesicular systems for applications with previously unmet requirements. The modular combination of scaffolds and functional building blocks enables the engineering of complex systems with biomimetic or new-to-nature functionalities. Inspired by the compartmentalized organization of cells and organelles, lipid or polymer vesicles are widely used as model membrane systems to investigate the translocation of solutes and the transduction of signals by membrane proteins. The bottom-up assembly and functionalization of such artificial compartments enables full control over their composition and can thus provide specifically optimized environments for synthetic biological processes. This review aims to inspire future endeavors by providing a diverse toolbox of molecular modules, engineering methodologies, and different approaches to assemble artificial vesicular systems. Important technical and practical aspects are addressed and selected applications are presented, highlighting particular achievements and limitations of the bottom-up approach. Complementing the cutting-edge technological achievements, fundamental aspects are also discussed to cater to the inherently diverse background of the target audience, which results from the interdisciplinary nature of synthetic biology. The engineering of proteins as functional modules and the use of lipids and block copolymers as scaffold modules for the assembly of functionalized vesicular systems are explored in detail. Particular emphasis is placed on ensuring the controlled assembly of these components into increasingly complex vesicular systems. Finally, all descriptions are presented in the greater context of engineering valuable synthetic biological systems for applications in biocatalysis, biosensing, bioremediation, or targeted drug delivery.

Caveolin-1β promotes the production of active human microsomal glutathione S-transferase in induced intracellular vesicles inSpodoptera frugiperda21 insect cells

The heterologous expression in Spodoptera frugiperda 21 (Sf21) insect cells of the β isoform of canine caveolin-1 (caveolin-1β), using a baculovirus-based vector, resulted in intracellular vesicles enriched in caveolin-1β. We investigated whether these vesicles could act as membrane reservoirs, and promote the production of an active membrane protein (MP) when co-expressed with caveolin-1β. We chose hMGST1 (human microsomal glutathione S-transferase 1) as the co-expressed MP. It belongs to the membrane-associated proteins in eicosanoid and glutathione metabolism (MAPEG) family of integral MPs, and, as a phase II detoxification enzyme, it catalyzes glutathione conjugation of lipophilic drugs present in the lipid membranes. In addition to its pharmaceutical interest, its GST activity can be conveniently measured. The expression of both MPs were followed by Western blots and membrane fractionation on density gradient, and their cell localization by immunolabeling and transmission electron microscopy. We showed that caveolin-1β kept its capacity to induce intracellular vesicles in the host when co-expressed with hMGST1, and that hMGST1 is in part addressed to these vesicles. Remarkably, a fourfold increase in the amount of active hMGST1 was found in the most enriched membrane fraction, along with an increase of its specific activity by 60% when it was co-expressed with caveolin-1β. Thus, heterologously expressed caveolin-1β was able to induce cytoplasmic vesicles in which a co-expressed exogenous MP is diverted and sequestered, providing a favorable environment for this cargo.

In vivo enzymatic digestion of HRV 3C protease cleavage sites-containing proteins produced in a silkworm-baculovirus expression system

Baculovirus expression vector system (BEVS) has been recognized as a potent protein expression system in engineering valuable enzymes and vaccines. Various fusion tags facilitate protein purification, leaving the potential risk to influence the target protein's biological activity negatively. It is of great interest to consider removing the additional tags using site-specific proteases, such as human rhinoviruses (HRV) 3C protease. The current study validated the cleavage activity of 3C protease in Escherichia coli and silkworm-BEVS systems by mixing the cell or fat body lysates of 3C protein and 3C site containing target protein in vitro. Further verification has been performed in the fat body lysate from co-expression of both constructs, showing remarkable cleavage efficiency in vivo silkworm larvae. We also achieved the glutathione-S-transferase (GST) tag-cleaved product of the VP15 protein from the White spot syndrome virus after purification, suggesting that we successfully established a coinfection-based recognition-and-reaction BEVS platform for the tag-free protein engineering.

Plasmid-Based Gene Expression Systems for Lactic Acid Bacteria: A Review

Lactic acid bacteria (LAB) play a very vital role in food production, preservation, and as probiotic agents. Some of these species can colonize and survive longer in the gastrointestinal tract (GIT), where their presence is crucially helpful to promote human health. LAB has also been used as a safe and efficient incubator to produce proteins of interest. With the advent of genetic engineering, recombinant LAB have been effectively employed as vectors for delivering therapeutic molecules to mucosal tissues of the oral, nasal, and vaginal tracks and for shuttling therapeutics for diabetes, cancer, viral infections, and several gastrointestinal infections. The most important tool needed to develop genetically engineered LABs to produce proteins of interest is a plasmid-based gene expression system. To date, a handful of constitutive and inducible vectors for LAB have been developed, but their limited availability, host specificity, instability, and low carrying capacity have narrowed their spectrum of applications. The current review discusses the plasmid-based vectors that have been developed so far for LAB; their functionality, potency, and constraints; and further highlights the need for a new, more stable, and effective gene expression platform for LAB.

The pre-induction temperature affects recombinant HuGM-CSF aggregation in thermoinducible Escherichia coli

The overproduction of recombinant proteins in Escherichia coli leads to insoluble aggregates of proteins called inclusion bodies (IBs). IBs are considered dynamic entities that harbor high percentages of the recombinant protein, which can be found in different conformational states. The production conditions influence the properties of IBs and recombinant protein recovery and solubilization. The E. coli growth in thermoinduced systems is generally carried out at 30 °C and then recombinant protein production at 42 °C. Since the heat shock response in E. coli is triggered above 34 °C, the synthesis of heat shock proteins can modify the yields of the recombinant protein and the structural quality of IBs. The objective of this work was to evaluate the effect of different pre-induction temperatures (30 and 34 °C) on the growth of E. coli W3110 producing the human granulocyte-macrophage colony-stimulating factor (rHuGM-CSF) and on the IBs structure in a λpL/pR-cI857 thermoinducible system. The recombinant E. coli cultures growing at 34 °C showed a ~ 69% increase in the specific growth rate compared to cultures grown at 30 °C. The amount of rHuGM-CSF in IBs was significantly higher in cultures grown at 34 °C. Main folding chaperones (DnaK and GroEL) were associated with IBs and their co-chaperones (DnaJ and GroES) with the soluble protein fraction. Finally, IBs from cultures that grew at 34 °C had a lower content of amyloid-like structure and were more sensitive to proteolytic degradation than IBs obtained from cultures at 30 °C. Our study presents evidence that increasing the pre-induction temperature in a thermoinduced system allows obtaining higher recombinant protein and reducing amyloid contents of the IBs. KEY POINTS: • Pre-induction temperature determines inclusion bodies architecture • In pre-induction (above 34 °C), the heat shock response increases recombinant protein production • Inclusion bodies at higher pre-induction temperature show a lower amyloid content.

Insect Cells-Baculovirus System for the Production of Difficult to Express Proteins: From Expression Screening for Soluble Constructs to Protein Quality Control

Rapid preparation of proteins for functional and structural analysis is a major challenge both in academia and industry. The number potential targets continuously increases and many are difficult to express proteins which, when produced in bacteria, result in insoluble and/or misfolded recombinant proteins, protein aggregates, or unusable low protein yield. We focus here on the baculovirus expression vector system which is now commonly used for heterologous production of human targets. This chapter describes simple and cost-effective protocols that enable iterative cycles of construct design, expression screening and optimization of protein production. We detail time- and cost-effective methods for generation of baculoviruses by homologous recombination and titer evaluation. Handling of insect cell cultures and preparation of bacmid for cotransfection are also presented.

Transformation of Dunaliella salina by Agrobacterium tumefaciens for the Expression of the Hemagglutinin of Avian Influenza Virus H5

Avian influenza (AI) is one of the main threats to the poultry industry worldwide. Vaccination efforts are based on inactivated, live attenuated, and recombinant vaccines, where the virus hemagglutinin (HA) is the main component of any vaccine formulation. This study uses Dunaliella salina to express the AIV HA protein of an H5 virus. D. salina offers a system of feasible culture properties, generally recognized as safe for humans (GRAS), with N-glycosylation and nuclear transformation by Agrobacterium tumefaciens. The cloning and transformation of D. salina cells with the H5HA gene was confirmed by polymerase chain reaction (PCR). SDS-PAGE and Western blot confirmed HA5r protein expression, and the correct expression and biological activity of the HA5r protein were confirmed by a hemagglutination assay (HA). This study proves the feasibility of using a different biological system for expressing complex antigens from viruses. These findings suggest that a complex protein such as HA5r from AIV (H5N2) can be successfully expressed in D. salina.

Rational design of a new variant of Reteplase with optimized physicochemical profile and large-scale production in Escherichia coli

Structural engineering of the recombinant thrombolytic drug, Reteplase, and its cost-effective production are important goals in the pharmaceutical industry. In this study, a single-point mutant of the protein was rationally designed and evaluated in terms of physicochemical characteristics, enzymatic activity, as well as large-scale production settings. An accurate homology model of Reteplase was used as the input to appropriate tools to identify the aggregation-prone sites, while considering the structural stability. Selected variants underwent extensive molecular dynamic simulations (total 540 ns) to assess their solvation profile and their thermal stability. The Reteplase-fibrin interaction was investigated by docking. The best variant was expressed in E. coli, and Box-Behnken design was used through response surface methodology to optimize its expression conditions. M72R mutant demonstrated appropriate stability, enhanced enzymatic activity (p < 0.05), and strengthened binding to fibrin, compared to the wild type. The optimal conditions for the variant's production in a bioreactor was shown to be 37 ºC, induction with 0.5 mM IPTG, for 2 h of incubation. Under these conditions, the final amount of the produced enzyme was increased by about 23 mg/L compared to the wild type, with an increase in the enzymatic activity by about 2 IU/mL. This study thus offered a new Reteplase variant with nearly all favorable properties, except solubility. The impact of temperature and incubation time on its large-scale production were underlined as well.

Potential applications of recombinant bifidobacterial proteins in the food industry, biomedicine, process innovation and glycobiology

Bifidobacterial proteins have been widely studied to elucidate the metabolic mechanisms of diet adaptation and survival of Bifidobacteria, among others. The use of heterologous expression systems to obtain proteins in sufficient quantities to be characterized has been essential in these studies. L. lactis and the same Bifidobacterium as expression systems highlight ways to corroborate some of the functions attributed to these proteins. The most studied proteins are enzymes related to carbohydrate metabolism, particularly glycosidases, due to their potential application in the synthesis of neoglycoconjugates, prebiotic neooligosaccharides, and active metabolites as well as their high specificity and efficiency in processing glycoconjugates. In this review, we classified the recombinant bifidobacterial proteins reported to date whose characterization has demonstrated their usefulness or their ability to produce a product of commercial interest for the food industry, biomedicine, process innovation and glycobiology. Future directions for their study are also discussed.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-021-00957-1.

Development of a Scrub Typhus Diagnostic Platform Incorporating Cell-Surface Display Technology

Scrub typhus (ST), also known as tsutsugamushi disease and caused by rickettsia Orientia tsutsugamushi, is an underestimated fatal epidemic in the Asia-Pacific region, resulting in a million human infections each year. ST is easily misdiagnosed as clinical diagnosis is based on non-specific skin eschar and flu-like symptoms. Thus, the lack of accurate, convenient, and low-cost detection methods for ST poses a global health threat. To address this problem, we adopted baculovirus surface-display technology to express three variants of TSA56, the major membrane antigen of O. tsutsugamushi, as well as the passenger domain of ScaC (ScaC-PD), on insect Sf21 cell surfaces rather than biosafety level 3 bacteria in an enzyme-linked immunosorbent assay (ELISA). Recombinant TSA56 and ScaC-PD were all properly expressed and displayed on Sf21 cells. Our cell-based ELISA comprising the four antigen-displaying cell types interacted with monoclonal antibodies as well as serum samples from ST-positive field-caught rats. This cell-based ELISA presented high accuracy (96.3%), sensitivity (98.6%), and specificity (84.6%) when tested against the ST-positive rat sera. Results of a pilot study using human sera were also highly consistent with the results of immunofluorescence analyses. By adopting this approach, we circumvented complex purification and refolding processes required to generate recombinant O. tsutsugamushi antigens and reduced the need for expensive equipment and extensively trained operators. Thus, our system has the potential to become a widely used serological platform for diagnosing ST.

Protein Production and Purification of a Codon-Optimized Human NGN3 Transcription Factor from E. coli

Neurogenin 3 (NGN3) transcription factor is vital for the development of endocrine cells of the intestine and pancreas. NGN3 is also critical for the neural precursor cell determination in the neuroectoderm. Additionally, it is one of the vital transcription factors for deriving human β-cells from specialized somatic cells. In the current study, the production and purification of the human NGN3 protein from Escherichia coli (E. coli) is reported. First, the 642 bp protein-coding nucleotide sequence of the NGN3 gene was codon-optimized to enable enhanced protein expression in E. coli strain BL21(DE3). The codon-optimized NGN3 sequence was fused in-frame to three different fusion tags to enable cell penetration, nuclear translocation, and affinity purification. The gene insert with the fusion tags was subsequently cloned into an expression vector (pET28a( +)) for heterologous expression in BL21(DE3) cells. A suitable genetic construct and the ideal expression conditions were subsequently identified that produced a soluble form of the recombinant NGN3 fusion protein. This NGN3 fusion protein was purified to homogeneity (purity > 90%) under native conditions, and its secondary structure was retained post-purification. This purified protein, when applied to human cells, did not induce cytotoxicity. Further, the cellular uptake and nuclear translocation of the NGN3 fusion protein was demonstrated followed by its biological activity in PANC-1 cells. Prospectively, this recombinant protein can be utilized for various biological applications to investigate its functionality in cell reprogramming, biological processes, and diseases.

Facile expression and purification of active human growth hormone in E. coli by a cleavable self-aggregating tag scheme

Human growth hormone (hGH) plays an important role in growth control, growth promotion, cell development, and regulation of numerous metabolic pathways in the human body and has been approved by the U.S. FDA for the treatment of several human dysfunctions. Over-expression of recombinant hGH (rhGH) affords a misfolded form in cytoplasm of Escherichia coli, and the refolding step required to obtain active rhGH greatly affects its production costs. Herein, the cleavable self-aggregating tag (cSAT) scheme was used for the expression and purification of rhGH in E. coli. Four aggregating tags (L₆KD/α3-peptide/EFK8/ELK16) successfully drove rhGH into active protein aggregates. After the Mxe GyrA intein-mediated cleavage, 2.8-21.4 μg rhGH/mg wet cell weight was obtained at laboratory scale, of which the L₆KD fusion achieved the highest rhGH yield. The further refined rhGH maintained 92% of the bioactivity compared to commercial rhGH. The self-assembling of the aggregating tag might physically separate the hGH polypeptide chains, which in turn was beneficial to its folding into the active form. This study provided a simple and cost-effective approach for active rhGH production, and suggested an opportunity for improve folding of recombinant proteins in E. coli.

SynBac: Enhanced Baculovirus Genomes by Iterative Recombineering

Baculovirus expression vector systems (BEVS) are widely used to produce heterologous proteins for a wide range of applications. Developed more than 30 years ago, BEVS have been constantly modified to improve product quality and ease-of-use. Plasmid reagents were tailored and engineered to facilitate introduction of heterologous genes into baculoviral genomes. At the same time, detrimental modalities such as genes encoding proteases or apoptotic factors were removed to improve protein yield. Advances in DNA synthesis and manipulation now enable the engineering of part or whole synthetic baculovirus genomes, opening up new avenues to redesign and tailor the system to specific applications. Here, we describe a simple protocol for designing and constructing baculovirus genomes comprising segments of synthetic DNA through the use of iterative Red/ET homologous recombination reactions.

Impact of the Expression System on Recombinant Protein Production in Escherichia coli BL21

Recombinant protein production for medical, academic, or industrial applications is essential for our current life. Recombinant proteins are obtained mainly through microbial fermentation, with Escherichia coli being the host most used. In spite of that, some problems are associated with the production of recombinant proteins in E. coli, such as the formation of inclusion bodies, the metabolic burden, or the inefficient translocation/transport system of expressed proteins. Optimizing transcription of heterologous genes is essential to avoid these drawbacks and develop competitive biotechnological processes. Here, expression of YFP reporter protein is evaluated under the control of four promoters of different strength (P_T7lac, P_trc, P_tac, and P_BAD) and two different replication origins (high copy number pMB1′ and low copy number p15A). In addition, the study has been carried out with the E. coli BL21 wt and the ackA mutant strain growing in a rich medium with glucose or glycerol as carbon sources. Results showed that metabolic burden associated with transcription and translation of foreign genes involves a decrease in recombinant protein expression. It is necessary to find a balance between plasmid copy number and promoter strength to maximize soluble recombinant protein expression. The results obtained represent an important advance on the most suitable expression system to improve both the quantity and quality of recombinant proteins in bioproduction engineering.

Improvement of protein production by engineering a novel antiapoptotic baculovirus vector to suppress the expression of Sf-caspase-1 and Tn-caspase-1

The baculovirus expression vector system (BEVS) is an attractive manufacturing platform for recombinant protein production in insect cells. However, baculovirus infection commonly induces host apoptosis in 3-4 days which would subsequently terminate the protein expression. Previous studies have proved that protein production by BEVS can be elevated in apoptosis-suppressed insect cells. We also developed a baculovirus vector in our previous report to inhibit the apoptosis and improve protein production in Sf9 cells. In this study, we designed five short hairpin RNA (shRNA) expression cassettes targeting a conserved region in Spodoptera frugiperda caspase-1 (Sf-caspase-1) and Trichoplusia ni caspase-1 (Tn-caspase-1), and found that introduction of C to T mutations within the stem region of the expression cassette was beneficial for the heterologous protein expression. One of the improved shRNA expression cassettes was knocked into a bacmid with the deletion of several nonessential genes. The novel baculovirus vector demonstrated the ability to suppress cell apoptosis in both Sf9 and High Five cells, and exhibited superior recombinant protein productivity of intracellularly expressed GFP and firefly luciferase and secreted glycoprotein OD-Fc. The antiapoptotic baculovirus vector developed in this study could serve as a useful tool for the protein production in scientific research and pharmaceutical industries.

Insect High FiveTM cell line development using site-specific flipase recombination technology

Insect Trichoplusia ni High FiveTM (Hi5) cells have been widely explored for production of heterologous proteins, traditionally mostly using the lytic baculovirus expression vector system (BEVS), and more recently using virus-free transient gene expression systems. Stable expression in such host cells would circumvent the drawbacks associated with both systems when it comes to scale-up and implementation of more efficient high-cell density process modes for the manufacturing of biologics. In this work, we combined Flipase (Flp) recombinase-mediated cassette exchange (RMCE) with fluorescence-activated cell sorting (FACS) for generating a stable master clonal Hi5 cell line with the flexibility to express single or multiple proteins of interest from a tagged genomic locus. The 3-step protocol herein implemented consisted of (i) introducing the RMCE docking cassette into the cell genome by random integration followed by selection in Hygromycin B and FACS (Hi5-tagging population), (ii) eliminating cells tagged in loci with low recombination efficiency by transfecting the tagging population with an eGFP-containing target cassette followed by selection in G418 and FACS (Hi5-RMCE population), and (iii) isolation of pure eGFP-expressing cells by FACS and expansion to suspension cultures (Hi5-RMCE master clone). Exchangeability of the locus in the master clone was demonstrated in small-scale suspension cultures by replacing the target cassette by one containing a single protein (i.e. iCherry, as an intracellular protein model) or two proteins (i.e. influenza HA and M1 for virus-like particles production, as an extracellular protein model). Overall, the stable insect Hi5 cell platform herein assembled has the potential to assist and accelerate biologics development.

Community-Wide Experimental Evaluation of the PROSS Stability-Design Method

Recent years have seen a dramatic improvement in protein-design methodology. Nevertheless, most methods demand expert intervention, limiting their widespread adoption. By contrast, the PROSS algorithm for improving protein stability and heterologous expression levels has been successfully applied to a range of challenging enzymes and binding proteins. Here, we benchmark the application of PROSS as a stand-alone tool for protein scientists with no or limited experience in modeling. Twelve laboratories from the Protein Production and Purification Partnership in Europe (P4EU) challenged the PROSS algorithm with 14 unrelated protein targets without support from the PROSS developers. For each target, up to six designs were evaluated for expression levels and in some cases, for thermal stability and activity. In nine targets, designs exhibited increased heterologous expression levels either in prokaryotic and/or eukaryotic expression systems under experimental conditions that were tailored for each target protein. Furthermore, we observed increased thermal stability in nine of ten tested targets. In two prime examples, the human Stem Cell Factor (hSCF) and human Cadherin-Like Domain (CLD12) from the RET receptor, the wild type proteins were not expressible as soluble proteins in E. coli, yet the PROSS designs exhibited high expression levels in E. coli and HEK293 cells, respectively, and improved thermal stability. We conclude that PROSS may improve stability and expressibility in diverse cases, and that improvement typically requires target-specific expression conditions. This study demonstrates the strengths of community-wide efforts to probe the generality of new methods and recommends areas for future research to advance practically useful algorithms for protein science.

Optimizing the First TPR Domain of the Human SPAG1 Protein Provides Insight into the HSP70 and HSP90 Binding Properties

Tetratricopeptide repeat domains, or TPR domains, are protein domains that mediate protein:protein interaction. As they allow contacts between proteins, they are of particular interest in transient steps of the assembly process of macromolecular complexes, such as the ribosome or the dynein arms. In this study, we focused on the first TPR domain of the human SPAG1 protein. SPAG1 is a multidomain protein that is important for ciliogenesis whose known mutations are linked to primary ciliary dyskinesia syndrome. It can interact with the chaperones RUVBL1/2, HSP70, and HSP90. Using protein sequence optimization in combination with structural and biophysical approaches, we analyzed, with atomistic precision, how the C-terminal tails of HSPs bind a variant form of SPAG1-TPR1 that mimics the wild-type domain. We discuss our results with regard to other complex three-dimensional structures with the aim of highlighting the motifs in the TPR sequences that could drive the positioning of the HSP peptides. These data could be important for the druggability of TPR regulators.

Simple and rapid plaque assay for recombinant baculoviruses expressing influenza hemagglutinin

Recombinant baculoviruses (rBVs) have been extensively used to generate virus-like particles, and baculoviruses expressing antigenic proteins have become efficient tools for inducing protective immunity. However, current methods for generating baculoviruses are costly and inefficient. Thus, the development of a simple, rapid, and accurate method of baculovirus titration is critically important. We established a method of plaque assay using an immunostaining method by which plaques can be easily visualized in Sf9 cells under a light microscope. Sf9 cells were infected with recombinant baculoviruses expressing influenza hemagglutinin surface proteins from H1N1 (A/California/04/09) or rH5N1 (A/Vietnam/1203/04). The infected cells were incubated with anti-HA antibody and the plaques were visualized using the chromogen 3'3-diaminobenzidine (DAB). Plaques were observed from days 1 to 6 post-infection, and differences in Sf9 cell seeding densities resulted in variations in the final plaque quantification. Sf9 cells seeded at a concentration of 5.5 × 104 cells/well or 7.5 × 104 cells/well showed the higher plaque titers at days 3, 4, and 5 post-infection than those found at days 1, 2, and 6 post-infection. With 5.5 × 104 cells/well or 7.5 × 104 cells/well of cell concentrations, recombinant baculovirus for rBV-HA (H1N1) showed 6 × 107 pfu/ml of titer and rBVs for rBV-HA (rH5N1) showed 5.4 × 107 pfu/ml of titer. Three days of baculovirus incubation with a certain concentration of Sf9 cells seeded are required for a rapid, simple, and accurate plaque assay, which could significantly contribute to all baculovirus-related studies.

Impact of structural biologists and the Protein Data Bank on small-molecule drug discovery and development

The Protein Data Bank (PDB) is an international core data resource central to fundamental biology, biomedicine, bioenergy, and biotechnology/bioengineering. Now celebrating its 50th anniversary, the PDB houses >175,000 experimentally determined atomic structures of proteins, nucleic acids, and their complexes with one another and small molecules and drugs. The importance of three-dimensional (3D) biostructure information for research and education obtains from the intimate link between molecular form and function evident throughout biology. Among the most prolific consumers of PDB data are biomedical researchers, who rely on the open access resource as the authoritative source of well-validated, expertly curated biostructures. This review recounts how the PDB grew from just seven protein structures to contain more than 49,000 structures of human proteins that have proven critical for understanding their roles in human health and disease. It then describes how these structures are used in academe and industry to validate drug targets, assess target druggability, characterize how tool compounds and other small-molecules bind to drug targets, guide medicinal chemistry optimization of binding affinity and selectivity, and overcome challenges during preclinical drug development. Three case studies drawn from oncology exemplify how structural biologists and open access to PDB structures impacted recent regulatory approvals of antineoplastic drugs.

Expressing of Recombinant VEGFR2-specific Nanobody in Baculovirus Expression System

Background

Baculovirus expression system, introduced more than 20 years ago, is considered as a useful tool for large and complex eukaryotic recombinant protein production. A baculovirus expression vector is a recombinant virus which desired foreign protein coding sequences is under control of the virus gene promoter. Baculovirus only infects insect cells and do not normally infect vertebrates therefore, they possess no risk of biological risks for human.

Objectives

The aim of this study was to recombinant expression of vascular endothelial growth factor (VEGF) reseptor-2 specific Nanobody in the baculovirus expression system.

Materials and Methods

Gene of specific Nanobody against the VEGF reseptor-2 that called 3VGR19 was cloned and expressed in baculovirus system.

Results

3VGR19 Nanobody gene was amplified by Polymerase Chain Reaction (PCR) using the specific primers, and was cloned in pFastBac HTA plasmid. DH10Bac bacteria was transformed with resulted donor plasmid. The cultured Sf9 insect cell line was transfected with recombinant bacmid, and finally, the expression and purification of 3VGR19 was confirmed in insect cells.

Conclusions

In conclusion, Transient infection of insect cells with baculovirus can be a promising technology for expression of antibody fragments.

Enabling NMR Studies of High Molecular Weight Systems Without the Need for Deuteration: The XL-ALSOFAST Experiment with Delayed Decoupling

Current biological research increasingly focusses on large human proteins and their complexes. Such proteins are difficult to study by NMR spectroscopy because they often can only be produced in higher eukaryotic expression systems, where deuteration is hardly feasible. Here, we present the XL-ALSOFAST-[13 C,1 H]-HMQC experiment with much improved sensitivity for fully protonated high molecular weight proteins. For the tested systems ranging from 100 to 240 kDa in size, 3-fold higher sensitivity was obtained on average for fast relaxing signals compared to current state-of-the-art experiments. In the XL-ALSOFAST approach, non-observed magnetisation is optimally exploited and transverse relaxation is minimized by the newly introduced concept of delayed decoupling. The combination of high sensitivity and superior artefact suppression makes it ideal for studying inherently unstable membrane proteins or for analysing therapeutic antibodies at natural 13 C abundance. The XL-ALSOFAST and delayed decoupling will therefore expand the range of biomolecular systems accessible to NMR spectroscopy.

Over-Production of Therapeutic Growth Factors for Articular Cartilage Regeneration by Protein Production Platforms and Protein Packaging Cell Lines

Simple Summary

Osteoarthritis (OA) is the most common form of arthritis across the world. Most of the existing drugs for OA treat the symptoms of pain and inflammation. There are no drugs that can dure the disease. There are a number of new treatments for OA including cell therapy and gene therapy. This articles outlines the concept behind TissueGene-C, a new biological drug for OA. This new treatment includes cartilage cells mixed with a genetically modified cell line called GP2-293, which is effectively a “drug factory”, over-producing the growth factors that are important for cartilage regeneration and changing the environment inside joints. The mixture is injected into the affected knee joint. These cells are designed to be short-lived and cannot reproduce. Therefore, after they have done their job, they die and are cleared by immune cells. This is a new and modern approach to treating OA and TissueGene-C is the prototype cell therapy for OA. In the future, it is entirely possible to combine different clones of genetically engineered cells like GP2-293 that have been designed to over-produce a growth factor or biological drug with cells from the cartilage endplate of the intervertebral disc to treat degeneration in the spine.

Abstract

This review article focuses on the current state-of-the-art cellular and molecular biotechnology for the over-production of clinically relevant therapeutic and anabolic growth factors. We discuss how the currently available tools and emerging technologies can be used for the regenerative treatment of osteoarthritis (OA). Transfected protein packaging cell lines such as GP-293 cells may be used as “cellular factories” for large-scale production of therapeutic proteins and pro-anabolic growth factors, particularly in the context of cartilage regeneration. However, when irradiated with gamma or x-rays, these cells lose their capacity for replication, which makes them safe for use as a live cell component of intra-articular injections. This innovation is already here, in the form of TissueGene-C, a new biological drug that consists of normal allogeneic primary chondrocytes combined with transduced GP2-293 cells that overexpress the growth factor transforming growth factor β1 (TGF-β1). TissueGene-C has revolutionized the concept of cell therapy, allowing drug companies to develop live cells as biological drug delivery systems for direct intra-articular injection of growth factors whose half-lives are in the order of minutes. Therefore, in this paper, we discuss the potential for new innovations in regenerative medicine for degenerative diseases of synovial joints using mammalian protein production platforms, specifically protein packaging cell lines, for over-producing growth factors for cartilage tissue regeneration and give recent examples. Mammalian protein production platforms that incorporate protein packaging eukaryotic cell lines are superior to prokaryotic bacterial expression systems and are likely to have a significant impact on the development of new humanized biological growth factor therapies for treating focal cartilage defects and more generally for the treatment of degenerative joint diseases such as OA, especially when injected directly into the joint.

Evaluation and Optimization of Protein Extraction From E. coli by Electroporation

Growing diversity of protein-based technologies dictates further development of bio manufacturing to lower the cost of production and maximize yields. Intracellularly expressed recombinant proteins must be extracted from production host prior to purification. Use of electroporation to obtain proteins from bacteria and yeasts has been demonstrated in several studies for different modes of operation and formats. Here we tested various protocols for protein extraction from Escherichia coli by means of electroporation. The tested protocols were compared to established extraction methods of ultrasonication and glass-bead milling in terms of protein yields and content of impurities such as host cell DNA and endotoxins in the lysate. Protein extraction yield was maximal when exponentially growing bacteria were treated at 37°C, regardless of the electroporation mode of operation (batch or flow). We were unable to eliminate co-extraction of host DNA and endotoxins, but with 8 × 1 ms, 5 kV/cm, 1 Hz pulses they were minimized. Yields with optimized electroporation (up to 86 g protein/kg dry weight) were inferior to those in ultrasonication (up to 144 g protein/kg dry weight) and glass-bead milling (up to 280 g protein/kg dry weight). Nevertheless, electroporation largely avoids cell lysis and disintegration with which the extract is a mix of extracted proteins with debris of the bacterial envelope and bacterial DNA, which necessitates further purification.

A scalable insect cell-based production process of the human recombinant BMX for in-vitro covalent ligand high-throughput screening

Bone Marrow Tyrosine kinase in the chromosome X (BMX) is a TEC family kinase associated with numerous pathological pathways in cancer cells. Covalent inhibition of BMX activity holds promise as a therapeutic approach against cancer. To screen for potent and selective covalent BMX inhibitors, large quantities of highly pure BMX are normally required which is challenging with the currently available production and purification processes. Here, we developed a scalable production process for the human recombinant BMX (hrBMX) using the insect cell-baculovirus expression vector system. Comparable expression levels were obtained in small-scale shake flasks (13 mL) and in stirred-tank bioreactors (STB, 5 L). A two-step chromatographic-based process was implemented, reducing purification times by 75% when compared to traditional processes, while maintaining hrBMX stability. The final production yield was 24 mg of purified hrBMX per litter of cell culture, with a purity of > 99%. Product quality was assessed and confirmed through a series of biochemical and biophysical assays, including circular dichroism and dynamic light scattering. Overall, the platform herein developed was capable of generating 100 mg purified hrBMX from 5 L STB in just 34 days, thus having the potential to assist in-vitro covalent ligand high-throughput screening for BMX activity inhibition.

A rapid approach for in locus overexpression of Trypanosoma brucei proteins

Altering amounts of a protein in a cell has become a crucial tool for understanding its function. In many organisms, including the protozoan parasite Trypanosoma brucei, protein overexpression has been achieved by inserting a protein-coding sequence into an overexpression vector. Here, we have adapted the PCR only based system for tagging trypanosome proteins at their endogenous loci such that it in addition enables a tetracycline-inducible T7 RNA polymerase-mediated protein overexpression. Hence, this approach bypasses the need for molecular cloning, making it rapid and cost effective. We validated the approach for ten flagellum-associated proteins with molecular weights ranging from 40 to over 500 kDa. For a majority of the recombinant proteins a significant (3-50 fold) increase in the cellular amount was achieved upon induction of overexpression. Two of the largest proteins studied, the dynein heavy chains, were significantly overexpressed, while two were not. Our data suggest that this may reflect the extent of the T7 RNA polymerase processivity on the trypanosome genomic DNA. We further show that the overexpression is informative as to cellular functions of the studied proteins, and that these cultures can serve as an excellent source for purification of the overexpressed proteins. We believe that this rapid in locus overexpression system will become a valuable tool to interrogate cellular functions and biochemical activities of trypanosome proteins.

Facile and scalable expression and purification of transcription factor IIH (TFIIH) core complex

Transcription factor IIH (TFIIH) plays essential roles in both the initiation of RNA Polymerase II-mediated transcription and the Nucleotide Excision Repair (NER) pathway in eukaryotes. In NER, the 7-subunit TFIIH Core sub-complex is responsible for the opening and extension of the DNA bubble created at the lesion site, utilizing the molecular motors XPB and XPD. Mutations in Core subunits are associated with a series of severe autosomal recessive disorders characterised by symptoms such as mild-to-extreme photosensitivity, premature ageing, physical and neurological anomalies, and in some cases an increased susceptibility to cancer. Although TFIIH Core has been successfully obtained in the past, the process has always remained challenging and laborious, involving many steps that severely hindered the amount of pure, active complex obtained. This has limited biochemical and functional studies of the NER process. Here we describe improved and simplified processes for the cloning, expression and purification of the 7-subunit TFIIH Core sub-complex. The combined use of auto-cleavable 2A-like sequences derived from the Foot-and-Mouth Disease Virus (FMDV) and the MultiBac™ cloning system, a powerful baculoviral expression vector specifically conceived for the obtaining of multi-subunit eukaryotic complexes, allowed us to obtain a single, 7-gene plasmid in a short time using regular restriction cloning strategies. Additionally, expression of the construct in High Five™ insect cells paired with a simple 5-step purification protocol allowed the extraction of a pure, active TFIIH Core sub-complex in milligram quantities.

Direct characterization of overproduced proteins by native mass spectrometry

Proteins derived by recombinant technologies must be characterized to ensure quality, consistency and optimal production. These properties are usually assayed following purification procedures that are time consuming and labor intensive. Here, we describe a native mass spectrometry (MS) approach, direct-MS, for rapid characterization of intact overexpressed proteins immediately from crude samples. In this protocol, we discuss the multiple applications of the method and outline the necessary steps required for sample preparation, data collection and interpretation of results. We begin with the sample preparation workflows, which are relevant for recombinant proteins produced within bacteria, those analyzed straight from crude cell lysate, and secreted proteins generated in eukaryotic expression systems that are assessed directly from the growth culture medium. We continue with the mass acquisition steps that enable immediate definition of properties such as expressibility, solubility, assembly state, folding, overall structure, stability, post-translational modifications and associations with biomolecules. We demonstrate the applicability of the method by presenting the characterization of a computationally designed toxin-antitoxin heterodimer, activity and protein-interaction determination of a regulatory protein and detailed glycosylation analysis of a designed intact antibody. Overall, we describe a simple and rapid protocol that is relevant to both prokaryotic and eukaryotic expression systems and can be carried out on multiple mass spectrometers, such as Orbitrap and quadrupole time-of-flight (QTOF)-based mass spectroscopy platforms, that enable intact protein detection. The procedure takes from 30 min to several hours, from sample collection to data acquisition, depending on the depth of MS analysis.

Purification of Membrane Proteins by Affinity Chromatography with On-Column Protease Cleavage

A protocol is described for the isolation of recombinant polyhistidine-tagged membrane proteins from overexpressing Escherichia coli cells. The gene encoding a target membrane protein is cloned into an expression plasmid and then introduced into E. coli cells for overexpression. Membranes from bacterial cells are isolated and the tagged target membrane protein is solubilized in detergent and subsequently bound to an affinity matrix. Tagged proteins are commonly eluted by an excess of a solute that competes for the binding to the matrix. Alternatively, amino acid sequence-specific proteases can be used to cleave off the affinity purification tag directly on the purification column (i.e., on-column cleavage). This selectively releases the target protein and allows subsequent elution. Importantly, this step represents an additional purification step and can significantly increase the purity of the isolated protein.

Synthesis and bioactivity evaluation of penta-1,4-diene-3-one oxime ether derivatives

A series of penta-1,4-diene-3-one oxime ether derivatives were synthesized, and their antiviral and antifungal activities were evaluated. Bioactivity evaluations showed that most target compounds had significant antiviral effects against tobacco mosaic virus (TMV). Among them, (1E,3Z,4E)-1-(4-(benzyloxy)phenyl)-5-(furan-2-yl)penta-1,4-dien-3-one O-(3-fluorobenzyl) oxime (5e) was found to have good curative activity against TMV, with an inhibition rate of 64.6%, which was better than that of ribavirin (45.2%). (1E,3Z,4E)-1-(4-(benzyloxy) phenyl)-5-(furan-2-yl)penta-1,4-dien-3-one O-((6-chloropyridin-3-yl)methyl) oxime (5d) had a remarkable protective effect against TMV, with an inhibitory rate of 66.9%, which was better than that of ribavirin (61.8%). The inhibitory rate of (1E,3Z,4E)-1-(2-(benzyloxy)phenyl)-5-(furan-2-yl)penta-1,4-dien-3-one O-(4-chlorobenzyl) oxime(5m) in inactivation activity against TMV was 87.0%, which was better than that of ribavirin (77.9%). Further molecular docking studies indicated that compound 5m shows strong binding affinities toward the coat protein of tobacco mosaic virus. This result indicates that penta-1,4-diene-3-one oxime ether derivatives can play a significant role in discovering new antiviral agents.

Surfing the Blood Coagulation Cascade: Insight into the Vital Factor Xa

Factor Xa (FXa) plays a key role in haemostasis, it is a central part of the blood coagulation cascade which catalyzes the production of thrombin and leads to clot formation and wound closure. Therefore, FXa is an attractive target for the development of new anticoagulant agents. In this review, we will first describe the molecular features of this fundamental protein in order to understand its mechanism of action, an essential background for the design of novel inhibitors by means of synthetic organic chemistry or using peptides obtained from recombinant methodologies. Then, we will review the current state of the synthesis of novel direct FXa inhibitors along with their mechanisms of action. Finally, approved reversal agents that aid in maintaining blood haemostasis by using these commercial drugs will also be discussed.

A practical method for efficient and optimal production of Seleno-methionine-labeled recombinant protein complexes in the insect cells

The use of Seleno-methionine (SeMet) incorporated protein crystals for single or multi-wavelength anomalous diffraction (SAD or MAD) to facilitate phasing has become almost synonymous with modern X-ray crystallography. The anomalous signals from SeMets can be used for phasing as well as sequence markers for subsequent model building. The production of large quantities of SeMet incorporated recombinant proteins is relatively straightforward when expressed in Escherichia coli. In contrast, production of SeMet substituted recombinant proteins expressed in the insect cells is not as robust due to the toxicity of SeMet in eukaryotic systems. Previous protocols for SeMet-incorporation in the insect cells are laborious, and more suited for secreted proteins. In addition, these protocols have generally not addressed the SeMet toxicity issue, and typically result in low recovery of the labeled proteins. Here we report that SeMet toxicity can be circumvented by fully infecting insect cells with baculovirus. Quantitatively controlling infection levels using our Titer Estimation of Quality Control (TEQC) method allow for the incorporation of substantial amounts of SeMet, resulting in an efficient and optimal production of labeled recombinant protein complexes. With the method described here, we were able to consistently reach incorporation levels of about 75% and protein yield of 60-90% compared with native protein expression.

Application of recurrent neural network for online prediction of cell density of recombinant Pichia pastoris producing HBsAg

Artificial neural networking (ANN) seems to be a promising soft sensor for implementing current approaches of quality by design (QbD) and process analytical technologies (PAT) in the biopharmaceutical industry. In this study, we aimed to implement best-fitted ANN architecture for online prediction of the biomass amount of recombinant Pichia pastoris (P. pastoris) - expressing intracellular hepatitis B surface antigen (HBsAg) - during the fed-batch fermentation process using methanol as a sole carbon source. For this purpose, at the induction phase of methanol fed-batch fermentation, carbon evolution rate (CER), dissolved oxygen (DO), and methanol feed rate were selected as input vectors and total wet cell weight (WCW) was considered as output vector for the ANN. The obtained results indicated that after training recurrent ANN with data sets of four fed-batch runs, this toolbox could predict the WCW of the next fed-batch fermentation process at each specified time point with high accuracy. The R-squared and root-mean-square error between actual and predicted values were found to be 0.9985 and 13.73, respectively. This verified toolbox could have major importance in the biopharmaceutical industry since recombinant P. pastoris is widely used for the large-scale production of HBsAg.

Evaluation of Reference Genes for Normalization of RT-qPCR Gene Expression Data for Trichoplusia ni Cells During Antheraea pernyi (Lepidoptera: Saturniidae) Multicapsid Nucleopolyhedrovirus (AnpeNPV) Infection

Baculovirus infection impacts global gene expression in the host cell, including the expression of housekeeping genes. Evaluation of candidate reference genes during a viral infection will inform the selection of appropriate reference gene(s) for the normalization of expression data generated by Reverse Transcription Quantitative Real-timePolymerase Chain Reaction (RT-qPCR). Antheraea pernyi multicapsid nucleopolyhedrovirus (AnpeNPV) is able to infect the High Five cells (Tn-Hi5). In the present study, 10 candidate reference genes were evaluated in AnpeNPV-infected Tn-Hi5 cells. Gene expression data were analyzed using geNorm, NormFinder, BestKeeper, and RefFinder. The candidate genes were further validated as reliable reference genes for RT-qPCR by analyzing the expression of three target genes. The results of data analysis using four statistical methods showed that RPS18 was the least stable among the candidate reference genes tested. 18S rRNA and 28S rRNA were not suitable as reference genes for RT-qPCR analysis in AnpeNPV-infected Tn-Hi5 cells. Comprehensive ranking of the 10 candidate reference genes by RefFinder analysis indicated that Ann B, c45128_g1, and ACT were the top three genes. Normalization of the expression of three target genes using the candidate reference genes indicated the same expression pattern when Ann B and c45128_g1 were used as reference genes, with slight differences in the relative expression at each infection time point. Overall, Ann B and c45128_g1 were recommended to be more suitable than the most commonly used reference genes, such as ACT, GAPDH, and TUB, for RT-qPCR data normalization in AnpeNPV-infected Tn-Hi5 cells up to 48 hpi.

Ultrasensitive Quantification of Recombinant Proteins Using AAA-MS

Recombinant proteins are essential components of therapeutic, biotechnological, food, and household products. In some cases, recombinant proteins must be purified and their quantity and/or concentration precisely determined. In this chapter, we describe a protocol for the quantification of purified recombinant proteins. The protocol is based on a microwave-assisted acidic hydrolysis of the target protein followed by high-resolution mass spectrometry (HRMS) analysis of the hydrolytic products. Absolute quantification is obtained by adding controlled amounts of labeled amino acids that serve as standards.