A simple method for production and purification of soluble and biologically active recombinant human leukemia inhibitory factor (hLIF) fusion protein in Escherichia coli

RNA polymerase II dynamics shape enhancer-promoter interactions

How enhancers control target gene expression over long genomic distances remains an important unsolved problem. Here we investigated enhancer-promoter communication by integrating data from nucleosome-resolution genomic contact maps, nascent transcription and perturbations affecting either RNA polymerase II (Pol II) dynamics or the activity of thousands of candidate enhancers. Integration of new Micro-C experiments with published CRISPRi data demonstrated that enhancers spend more time in close proximity to their target promoters in functional enhancer-promoter pairs compared to nonfunctional pairs, which can be attributed in part to factors unrelated to genomic position. Manipulation of the transcription cycle demonstrated a key role for Pol II in enhancer-promoter interactions. Notably, promoter-proximal paused Pol II itself partially stabilized interactions. We propose an updated model in which elements of transcriptional dynamics shape the duration or frequency of interactions to facilitate enhancer-promoter communication.

Production of biologically active recombinant buffalo leukemia inhibitory factor (BuLIF) in Escherichia Coli

Background

Leukemia inhibitory factor (LIF) is a multifunctional cytokine which plays multiple roles in different biological processes such as implantation, bone remodeling, and hematopoiesis. The buESCs are difficult to culture due to lack of proper understanding of the culture conditions. LIF is one of the important factors which maintain the pluripotency in embryonic stem cells and commercial LIF from murine and human origin is used in the establishment of buffalo embryonic stem cells (buESCs). The LIF from a foreign origin is not able to maintain pluripotency and proliferation in buESCs for a long term which is contributed by difference in the binding sites on LIF; therefore, culture medium supplemented with buffalo-specific LIF may enhance the efficiency of buESCs by improving the environment of culture conditions. The high cost of LIF is another major drawback which restricts buESCs research, thus limits the scope of buffalo stem cell use. Various methods have been developed to produce human and murine LIF in prokaryotic system. However, Buffalo leukemia inhibitory factor (BuLIF) has not been yet produced in prokaryotic system. Here, we describe a simple strategy for the expression and purification of biologically active BuLIF in Escherichia coli (E. coli).

Results

The BuLIF cDNA from buffalo (Bubalus bubalis) was cloned into pET22b(+) and expressed in E. coli Lemo-21(DE3). The expression of BuLIF was directed into periplasmic space of E. coli which resulted in the formation of soluble recombinant protein. One step immobilized metal affinity chromatography (IMAC chromatography) was performed for purification of BuLIF with ≥ 95% of homogeneity. The recombinant protein was confirmed by western blot and identified by mass spectroscopy. The biological activity of recombinant BuLIF was determined on murine myeloid leukemic cells (M1 cells) by MTT proliferation assay. The addition of BuLIF increased the reduction of MTT by stimulated M1 cells in a dose-dependent manner. The BuLIF induced the formation of macrophage like structures from M1 cells where they engulfed fluorescent latex beads. The recombinant BuLIF successfully maintained pluripotency in buffalo embryonic stem cells (buESCs) and were positive for stem cells markers such as Oct-4, Sox-2, Nanog, and alkaline phosphatase activity.

Conclusions

The present study demonstrated a simple method for the production of bioactive BuLIF in E. coli through single step purification. BuLIF effectively maintained buffalo embryonic stem cells pluripotency. Thus, this purified BuLIF can be used in stem cell study, biomedical, and agricultural research.

Supplementary Information

The online version contains supplementary material available at 10.1186/s43141-022-00328-1.

Efficient production process of bioactive recombinant human leukemia inhibitory factor in Chinese hamster ovary cells

The rhLIF is widely used as an essential factor in stem cell cultures for cell therapies. However, all the recombinant LIFs commercially available are expensive, and no commercially available rhLIF meet the standards recommended by USP for use in cell therapies. The current study reports the efficient production of N-glycosylated and bioactive rhLIF in CHO cells. The production rate of established rhLIF-expressing rCHO cells was approximately 0.85 g/l in 12-day fed-batch cultures using a 7.5 l bioreactor. The rhLIF protein was purified via a four-step purification procedure with approximately 57% recovery rate and greater than 99% purity. The purified rhLIF was N-glycosylated and biologically active with an EC₅₀ of 0.167 ng/ml and a specific activity of 0.86 × 10³ IU/mg. The purification procedure controlled the levels of process-related impurities below critical levels recommended by USP for cytokines used in cell therapies. The current work is the first production process of N-glycosylated and bioactive rhLIF, which can be applied to large-scale manufacture of GMP-grade rhLIF for use as an ancillary material in cell therapy.

Production and characterization of recombinant human leukemia inhibitory factor and evaluation of anti-fertility effects of rabbit anti-rhLIF in Balb/c mice

Human leukemia inhibitory factor (hLIF) is a cytokine of interleukin-6 family. This study aimed to evaluate the recombinant production rate of active hLIF by different vector-host systems under various conditions. Moreover, a rabbit polyclonal antibody (pAb) against recombinant hLIF (rhLIF) was produced and its anti-fertility effects were explored in Balb/c mice. Four different constructs including pET22b/hLIF, pET28b/hLIF, pET32b/hLIF and pColdI/hLIF were designed and transformed into BL21-(DE3), Rosetta-(DE3), Origami-(DE3) and Shuffle T7-(DE3) host cells. The expression level and proliferative effect of rhLIF were measured by SDS-PAGE and MTT assays, respectively. Rabbit pAb to rhLIF was produced and characterized using enzyme-linked immunosorbent assay and western blot techniques. The Balb/c mice were divided into two intervention and control groups. Then, they were intraperitoneally injected by purified rabbit anti-rhLIF and non-immunized rabbit pAb, respectively. After sacrifice on day 7, the number of implantation sites was counted. The rhLIF was successfully expressed by pET32b/hLIF and pColdI/hLIF vectors in all hosts with no significant difference in the rate of their expression. The rhLIF was purified and checked for activity. The results showed that it is functionally active and the produced anti-rhLIF pAb could specifically bind to commercial rhLIF. Passive immunization results showed that anti-rhLIF antibody completely inhibited fertility in all injected Balb/c mice compared to controls. Although previous studies showed expression of rhLIF using various methods, using different vector-host systems ensures us of successful biological active expression of it. The pAb against rhLIF could be a powerful tool for inducing in vivo infertility.

In Vivo Removal of N-Terminal Fusion Domains From Recombinant Target Proteins Produced in Nicotiana benthamiana

Plants show great potential for producing recombinant proteins in a cost-effective manner. Many strategies have therefore been employed to express high levels of recombinant proteins in plants. Although foreign domains are fused to target proteins for high expression or as an affinity tag for purification, the retention of foreign domains on a target protein may be undesirable, especially for biomedical purposes. Thus, their removal is often crucial at a certain time point after translation. Here, we developed a new strategy to produce target proteins without foreign domains. This involved in vivo removal of foreign domains fused to the N-terminus by the small ubiquitin-related modifier (SUMO) domain/SUMO-specific protease system. This strategy was tested successfully by generating a recombinant gene, BiP:p38:bdSUMO : His:hLIF, that produced human leukemia inhibitory factor (hLIF) fused to p38, a coat protein of the Turnip crinkle virus; the inclusion of p38 increased levels of protein expression. The recombinant protein was expressed at high levels in the leaf tissue of Nicotiana benthamiana. Coexpression of bdSENP1, a SUMO-specific protease, proteolytically released His:hLIF from the full-length recombinant protein in the endoplasmic reticulum of N. benthamiana leaf cells. His:hLIF was purified from leaf extracts via Ni²⁺-NTA affinity purification resulting in a yield of 32.49 mg/kg, and the N-terminal 5-residues were verified by amino acid sequencing. Plant-produced His:hLIF was able to maintain the pluripotency of mouse embryonic stem cells. This technique thus provides a novel method of removing foreign domains from a target protein in planta.

Recombinant purified buffalo leukemia inhibitory factor plays an inhibitory role in cell growth

Leukemia Inhibitory Factor (LIF) is a polyfunctional cytokine, involved in numerous regulatory effects in vivo and in vitro, varying from cell proliferation to differentiation, and has therapeutic potential for treating various diseases. In the current study, a COS-1 cell line overexpressing recombinant Buffalo LIF (rBuLIF) was established. The rBuLIF was purified to homogeneity from the total cell lysate of COS-1 cells using a two-step affinity chromatography. The purified LIF was confirmed by western blot and mass spectrometer (MS/MS). Particularly, high-resolution MS has identified the rBuLIF with 73% of sequence coverage with highest confidence parameters and with the search engine score of 4580. We determined the molecular weight of rBuLIF protein to be 58.99 kDa and 48.9 kDa with and without glycosylation, respectively. Moreover, the purified rBuLIF was verified to be functionally active by measuring the growth inhibition of M1 myeloid leukemia cells, revealing a maximum inhibition at 72 hours and half-maximal effective concentration (EC50) of 0.0555 ng/ml, corresponding to a specific activity of >1.6×10⁷ units/mg. Next, we evaluated the effect of rBuLIF on buffalo mammary epithelial cell lines for its role in involution and also identified the IC50 value for BuMEC migrating cells to be 77.8 ng/ml. Additionally, the treatment of MECs (BuMEC and EpH4) displayed significant (P < 0.05) reduction in growth progression, as confirmed by qRT-PCR analysis, suggesting its strong involvement in the involution of the mammary gland in vivo. Thus, we conclude that the glycosylated rBuLIF, purified from COS-1 cells was found to be functionally active as its natural counterpart.

Production of soluble bioactive mouse leukemia inhibitory factor from Escherichia coli using MBP tag

Embryonic stem cells and induced pluripotent stem cells depend on one of cytokines called leukemia inhibitory factor (LIF) to retain their undifferentiated state and pluripotency. Nevertheless, further progresses of stem cell scientific investigation and its possible application are limited owing to the expense of commercial LIF. Here we introduced a simple, practical and high level expression of MBP-mouse LIF through Escherichia coli system which was bioactive. The mLIF cDNA was inserted into vector of pMAL-C2X in order to generate N-terminal MBP-mLIF recombinant proteins in the cytoplasm of Escherichia coli. MBP-mLIF as a soluble form was expressed. One-step purification through gravitational affinity chromatography was accomplished to acquire high purity (>92%) MBP-mLIF. The MBP-mLIF products specifically suppressed the growth of M1cells in a dose-dependent pattern. MBP-mLIF also was proved the ability to maintain the pluripotency of iPSCs. These outcomes revealed that the N-end MBP tags of the MBP-mLIF did not obstruct mLIF bioactivity. This method to generate recombinant MBP-mLIF is a simple, practical, economical and user-friendly protocol.

A novel glucosamine derivative with low cytotoxicity enhances chondrogenic differentiation of ATDC5

Glucosamine (GlcN) is a component of native cartilage extracellular matrix and useful in cartilage repair, but it was limited by toxicity in high concentrations. With the aim of altering bioactive properties of GlcN to reduce the toxicity and to facilitate chondrogenesis for hyaline cartilage formation, we introduced an amino-group modification with double bond into GlcN to produce N-acryloyl-glucosamine (AGA). The cell ATDC5 was chosen to evaluate its cytotoxicity and chondrogenesis capability. Cell proliferation and cytotoxicity assay showed that AGA had significantly reduced the cytotoxicity compared to GlcN, and promoted ATDC5 proliferation. Alcian blue staining and biochemical analysis indicated that AGA enhanced extracellular matrix deposition. Both the mRNA and protein levels of articular cartilage markers, like Collagen II and Aggrecan were up-regulated, as shown by quantitative real-time PCR and immunofluorescence staining. Moreover, the level of fibrocartilage marker Collagen I and hypertrophic marker Collagen Χ weren't significantly changed. Overall, these results demonstrated that the AGA achieved the functional double-bond, reduction in toxicity and enhancement in chondrogenesis could be more potential in cartilage repair.

Effects of cholic acid modified glucosamine on chondrogenic differentiation

Glucosamine hydrochloride is a widely used drug for the treatment of osteoarthritis and can be easily modified by other molecules because of its alterable functional groups.

Expression and Purification of Recombinant Human Basic Fibroblast Growth Factor Fusion Proteins and Their Uses in Human Stem Cell Culture

To reduce the cost of cytokines and growth factors in stem cell research, a simple method for the production of soluble and biological active human basic fibroblast growth factor (hbFGF) fusion protein in <i>Escherichia coli</i> was established. Under optimal conditions, approximately 60-80 mg of >95% pure hbFGF fusion proteins (Trx-6xHis-hbFGF and 6xHis-hbFGF) were obtained from 1 liter of culture broth. The purified hbFGF proteins, both with and without the fusion tags, were biologically active, which was confirmed by their ability to stimulate proliferation of NIH3T3 cells. The fusion proteins also have the ability to support several culture passages of undifferentiated human embryonic stem cells and induce pluripotent stem cells. This paper describes a low-cost and uncomplicated method for the production and purification of biologically active hbFGF fusion proteins.

Soluble overexpression and purification of bioactive human CCL2 in E. coli by maltose-binding protein

Human chemokine (C-C motif) ligand 2 (hCCL2) is a small cytokine in the CC chemokine family that attracts monocytes, memory T lymphocytes, and natural killer cells to the site of tissue injury- or infection-induced inflammation. hCCL2 has been implicated in the pathogeneses of diseases characterized by monocytic infiltrates, including psoriasis, rheumatoid arthritis, atherosclerosis, multiple sclerosis, and insulin-resistant diabetes. The prokaryotic overexpression of hCCL2 has been investigated previously in an attempt to develop biomedical applications for this factor, but this has been hampered by protein misfolding and aggregation into inclusion bodies. In our present study, we screened 7 protein tags-Trx, GST, MBP, NusA, His8, PDI, and PDIb'a'-for their ability to allow the soluble overexpression of hCCL2. Three tags-MBP, His8, and PDI-solubilized more than half of the expressed hCCL2 fusion proteins. Lowering the expression temperature to 18 °C significantly further improved the solubility of all fusion proteins. MBP was chosen for further study based on its solubility, expression level, ease of purification, and tag size. MBP-CCL2 was purified using conventional chromatography and cleaved using TEV or Factor Xa proteases. Biological activity was assessed using luciferase and cell migration assays. Factor Xa-cleaved hCCL2 was found to be active and TEV-cleaved hCCL2 showed relatively less activity. This is probably because the additional glycine residues present at the N-terminus of hCCL2 following TEV digestion interfere with the binding of hCCL2 to its receptor.

Soluble prokaryotic expression and purification of crotamine using an N-terminal maltose-binding protein tag

Crotamine is a peptide toxin found in the venom of the rattlesnake Crotalus durissus terrificus. Interestingly, crotamine demonstrates promising anticancer, antimicrobial, and antifungal activities. The crotamine peptide can also deliver plasmids into rapidly dividing cells, such as cancer and stem cells, and demonstrates potent analgesic effects. Efficiently producing crotamine in mammalian cells is difficult because it is both cell-permeable and cytotoxic. Prokaryotic expression of this peptide is also difficult to maintain because it does not fold properly in the cytoplasm, resulting in aggregation and in the formation of inclusion bodies. In our current study, we show for the first time that N-terminal fusion with three protein tags-N-utilization substance protein A (NusA), protein disulfide isomerase b'a' domain (PDIb'a'), and maltose-binding protein (MBP)-enables the soluble overexpression of crotamine in the cytoplasm of Escherichia coli. MBP-tagged crotamine was purified using Ni affinity, anion exchange, and MBP chromatography. The tag was cleaved using TEV protease, and the final product was pure on a silver-stained gels. In total, 0.9 mg pure crotamine was obtained from each liter of bacterial culture with endotoxin level approximately 0.15 EU/μg, which is low enough to use in biomedical applications. The identity and intramolecular disulfide bonds were confirmed using MALDI-TOF MS analysis. Purified crotamine inhibited the hKv1.3 channel (but not hKv1.5) in a dose-dependent manner with IC50 value of 67.2 ± 44.7 nM (n = 10), indicating the correct protein folding. The crotamine product fused with MBP at its N-terminus also inhibited the hKv1.3 channel, suggesting that the N-terminus is not involved in the channel binding of the toxin.

Soluble prokaryotic overexpression and purification of bioactive human granulocyte colony-stimulating factor by maltose binding protein and protein disulfide isomerase

Human granulocyte colony-stimulating factor (hGCSF), a neutrophil-promoting cytokine, is an effective therapeutic agent for neutropenia patients who have undergone several cancer treatments. Efficient production of hGCSF using E. coli is challenging because the hormone tends to aggregate and forms inclusion bodies. This study examined the ability of seven different N-terminal fusion tags to increase expression of soluble hGCSF in E. coli. Four tag proteins, namely maltose-binding protein (MBP), N-utilization substance protein A, protein disulfide isomerase (PDI), and the b'a' domain of PDI (PDIb'a'), increased the solubility of hGCSF under normal conditions. Lowering the expression temperature from 30°C to 18°C also increased the solubility of thioredoxin-tagged and glutathione S-transferase-tagged hGCSF. By contrast, hexahistidine-tagged hGCSF was insoluble at both temperatures. Simple conventional chromatographic methods were used to purify hGCSF from the overexpressed PDIb'a'-hGCSF and MBP-hGCSF proteins. In total, 11.3 mg or 10.2 mg of pure hGCSF were obtained from 500 mL cultures of E. coli expressing PDIb'a'-hGCSF or MBP-hGCSF, respectively. SDS-PAGE analysis and silver staining confirmed high purity of the isolated hGCSF proteins, and the endotoxin levels were less than 0.05 EU/µg of protein. Subsequently, the bioactivity of the purified hGCSF proteins similar to that of the commercially available hGCSF was confirmed using the mouse M-NFS-60 myelogenous leukemia cell line. The EC₅₀s of the cell proliferation dose-response curves for hGCSF proteins purified from MBP-hGCSF and PDIb'a'-hGCSF were 2.83±0.31 pM, and 3.38±0.41 pM, respectively. In summary, this study describes an efficient method for the soluble overexpression and purification of bioactive hGCSF in E. coli.

Soluble expression of human leukemia inhibitory factor with protein disulfide isomerase in Escherichia coli and its simple purification

Human leukemia inhibitory factor (hLIF) is a multifunctional cytokine that is essential for maintaining the pluripotency of embryonic stem cells. hLIF may be also be useful in aiding fertility through its effects on increasing the implantation rate of fertilized eggs. Thus these applications in biomedical research and clinical medicine create a high demand for bioactive hLIF. However, production of active hLIF is problematic since eukaryotic cells demonstrate limited expression and prokaryotic cells produce insoluble protein. Here, we have adopted a hybrid protein disulfide isomerase design to increase the solubility of hLIF in Escherichia coli. Low temperature expression of hLIF fused to the b'a' domain of protein disulfide isomerase (PDIb'a') increased the soluble expression in comparison to controls. A simple purification protocol for bioactive hLIF was established that includes removal of the PDIb'a' domain by cleavage by TEV protease. The resulting hLIF, which contains one extra glycine residue at the N-terminus, was highly pure and demonstrated endotoxin levels below 0.05 EU/μg. The presence of an intramolecular disulfide bond was identified using mass spectroscopy. This purified hLIF effectively maintained the pluripotency of a murine embryonic stem cell line. Thus we have developed an effective method to produce a pure bioactive version of hLIF in E. coli for use in biomedical research.

Immobilized metal ion affinity chromatography: a review on its applications

After 35 years of development, immobilized metal ion affinity chromatography (IMAC) has evolved into a popular protein purification technique. This review starts with a discussion of its mechanism and advantages. It continues with its applications which include the purification of histidine-tagged proteins, natural metal-binding proteins, and antibodies. IMAC used in conjunction with mass spectroscopy for phosphoprotein fractionation and proteomics is also covered. Finally, this review addresses the developments, limitations, and considerations of IMAC in the biopharmaceutical industry.

Functional inclusion bodies produced in bacteria as naturally occurring nanopills for advanced cell therapies

Inclusion bodies (50-500 nm in diameter) produced in recombinant bacteria can be engineered to contain functional proteins with therapeutic potential. Upon exposure, these protein particles are efficiently internalized by mammalian cells and promote recovery from diverse stresses. Being fully biocompatible, inclusion bodies are a novel platform, as tailored nanopills, for sustained drug release in advanced cell therapies.

Daedalus: a robust, turnkey platform for rapid production of decigram quantities of active recombinant proteins in human cell lines using novel lentiviral vectors

A key challenge for the academic and biopharmaceutical communities is the rapid and scalable production of recombinant proteins for supporting downstream applications ranging from therapeutic trials to structural genomics efforts. Here, we describe a novel system for the production of recombinant mammalian proteins, including immune receptors, cytokines and antibodies, in a human cell line culture system, often requiring <3 weeks to achieve stable, high-level expression: Daedalus. The inclusion of minimized ubiquitous chromatin opening elements in the transduction vectors is key for preventing genomic silencing and maintaining the stability of decigram levels of expression. This system can bypass the tedious and time-consuming steps of conventional protein production methods by employing the secretion pathway of serum-free adapted human suspension cell lines, such as 293 Freestyle. Using optimized lentiviral vectors, yields of 20–100 mg/l of correctly folded and post-translationally modified, endotoxin-free protein of up to ~70 kDa in size, can be achieved in conventional, small-scale (100 ml) culture. At these yields, most proteins can be purified using a single size-exclusion chromatography step, immediately appropriate for use in structural, biophysical or therapeutic applications.