Exploring the impact of the recombinant Escherichia coli strain on defensins antimicrobial activity: BL21 versus Origami strain

Overexpression and biophysical and functional characterization of a recombinant FGF21

Fibroblast growth factor 21 (FGF21) is an endocrine FGF that plays a vital role in regulating essential metabolic pathways. FGF21 increases glucose uptake by cells, promotes fatty acid oxidation, reduces blood glucose levels, and alleviates metabolic diseases. However, detailed studies on its stability and biophysical characteristics have not been reported. Herein, we present the overexpression, biophysical characterization, and metabolic activity of a soluble recombinant FGF21 (rFGF21). The far-UV circular dichroism spectra of rFGF21 show a negative trough at 215 nm, indicating that the protein's backbone predominantly adopts a β sheet conformation. rFGF21 shows intrinsic tyrosine fluorescence at 305 nm. Thermal denaturation using differential scanning calorimetry reveals that rFGF21 is relatively thermally unstable, with a melting temperature of 46.8°C (±0.1°C). The urea-induced unfolding of rFGF21 is rapid, with a chemical transition midpoint of 0.4 M. rFGF21 is readily cleaved by trypsin in limited trypsin digestion assays. Isothermal titration calorimetry experiments show that rFGF21 does not bind to heparin. Interestingly, rFGF21 demonstrates proliferative activity in NIH/3T3 fibroblasts and enhances mitochondrial oxidative phosphorylation and fatty acid oxidation in 3T3-L1 adipocytes. These findings provide a crucial framework for the engineering of novel structure-based variants of FGF21 with improved stability and biological activity to treat metabolic disorders.

Recent advances in recombinant production of soluble proteins in E. coli

BACKGROUND

E. coli still remains the most commonly used organism to produce recombinant proteins in research labs. This condition is mirrored by the attention that researchers dedicate to understanding the biology behind protein expression, which is then exploited to improve the effectiveness of the technology. This effort is witnessed by an impressive number of publications, and this review aims to organize the most relevant novelties proposed in recent years.

RESULTS

The examined contributions address several of the known bottlenecks related to recombinant expression in E. coli, such as improved glycosylation pathways, more reliable production of proteins whose folding depends on the formation of disulfide bonds, the possibility of controlling and even benefiting from the formation of aggregates or the need to overcome the dependence of bacteria on antibiotics during bacterial culture. Nevertheless, the majority of the published papers aimed at identifying the conditions for optimal control of the translation process to achieve maximal yields of functional exogenous proteins.

CONCLUSIONS

Despite community commitment, the critical question of what really is the metabolic burden and how it affects both host metabolism and recombinant protein production remains elusive because some experimental results are contradictory. This contribution aims to offer researchers a tool to orient themselves in this complexity. The new capacities offered by artificial intelligence tools could help clarifying this issue, but the training phase will probably require more systematic experimental approaches to collect sufficiently uniform data.

Micro RNA profiles in colostrum exosomes obtained from primiparous or multiparous dairy cows

Colostrum is rich in membranous vesicles of endocytic origin named exosomes, with proteins, lipids, RNA, and/or DNA cargos which can play different roles in physiological processes. Like other colostrum bioactive compounds, exosomes could be also influenced by individual characteristics. The objective of the study was to characterize miRNA cargo of colostrum exosomes from primiparous and multiparous cows in different farms. Twenty-seven colostrum samples of clinically healthy Holstein cows (11 primiparous and 16 multiparous) from 3 different farms were obtained and frozen. After thawing, exosomes were isolated following an ultracentrifugation protocol, and characterized morphologically. Particle size distribution and western immunoblotting were also analyzMaed. After RNA extraction, miRNAs were sequenced and analyzed to assess potential differences in profiles between primiparous and multiparous cows from different farms. Fourteen miRNA were upregulated and 11 miRNAs downregulated in primiparous compared with multiparous cows. Most of the miRNA differences between primiparous and multiparous cows regulate the gene expression of factors involved in mammary gland development and differentiation, and lipogenesis. In addition, miRNAs from one of the farms showed 8 miRNAs downregulated and 12 upregulated compared with the other 2 farms, independently of parity. Differences in miRNA between farms were mainly associated with immune and inflammatory-related genes. In conclusion, miRNA cargos of bovine colostrum exosomes differ in primiparous and multiparous cows, and some on-farm practices might also determine the content and activity of miRNA in colostrum exosomes.

A Novel Generation of Tailored Antimicrobial Drugs Based on Recombinant Multidomain Proteins

Antibiotic resistance has exponentially increased during the last years. It is necessary to develop new antimicrobial drugs to prevent and treat infectious diseases caused by multidrug- or extensively-drug resistant (MDR/XDR)-bacteria. Host Defense Peptides (HDPs) have a versatile role, acting as antimicrobial peptides and regulators of several innate immunity functions. The results shown by previous studies using synthetic HDPs are only the tip of the iceberg, since the synergistic potential of HDPs and their production as recombinant proteins are fields practically unexplored. The present study aims to move a step forward through the development of a new generation of tailored antimicrobials, using a rational design of recombinant multidomain proteins based on HDPs. This strategy is based on a two-phase process, starting with the construction of the first generation molecules using single HDPs and further selecting those HDPs with higher bactericidal efficiencies to be combined in the second generation of broad-spectrum antimicrobials. As a proof of concept, we have designed three new antimicrobials, named D5L37βD3, D5L37D5L37 and D5LAL37βD3. After an in-depth exploration, we found D5L37D5L37 to be the most promising one, since it was equally effective against four relevant pathogens in healthcare-associated infections, such as methicillin-susceptible (MSSA) and methicillin-resistant (MRSA) Staphylococcus aureus, methicillin-resistant Staphylococcus epidermidis (MRSE) and MDR Pseudomonas aeruginosa, being MRSA, MRSE and P. aeruginosa MDR strains. The low MIC values and versatile activity against planktonic and biofilm forms reinforce the use of this platform to isolate and produce unlimited HDP combinations as new antimicrobial drugs by effective means.

Host Defense Peptides in Nutrition and Diseases: A Contributor of Immunology Modulation

Host defense peptides (HDPs) are primary components of the innate immune system with diverse biological functions, such as antibacterial ability and immunomodulatory function. HDPs are produced and released by immune and epithelial cells against microbial invasion, which are widely distributed in humans, animals, plants, and microbes. Notably, there are great differences in endogenous HDP distribution and expression in humans and animals. Moreover, HDP expression could be regulated by exogenous substances, such as nutrients, and different physiological statuses in health and disease. In this review, we systematically assessed the regulation of expression and mechanism of endogenous HDPs from nutrition and disease perspectives, providing a basis to identify the specificity and regularity of HDP expression. Furthermore, the regulation mechanism of HDP expression was summarized systematically, and the differences in the regulation between nutrients and diseases were explored. From this review, we provide novel ideas targeted the immune regulation of HDPs for protecting host health in nutrition and practical and effective new ideas using the immune regulation theory for further research on protecting host health from pathogenic infection and excessive immunity diseases under the global challenge of the antibiotic-abuse-induced series of problems, including food security and microbial resistance.

Quality comparison of recombinant soluble proteins and proteins solubilized from bacterial inclusion bodies

Recombinant protein production in bacteria is often accompanied by the formation of aggregates, known as inclusion bodies (IBs). Although several strategies have been developed to minimize protein aggregation, many heterologous proteins are produced in aggregated form. For these proteins, purification necessarily requires processes of solubilization and refolding, often involving denaturing agents. However, the presence of biologically active recombinant proteins forming IBs has driven a redefinition of the protocols used to obtain soluble protein avoiding the protein denaturation step. Among the different strategies described, the detergent n-lauroylsarcosine (NLS) has proved to be effective. However, the impact of the NLS on final protein quality has not been evaluated so far. Here, the activity of three antimicrobial proteins (all as GFP fusions) obtained from the soluble fraction was compared with those solubilized from IBs. Results showed that NLS solubilized proteins from IBs efficiently, but that protein activity was impaired. Thus, a solubilization protocol without detergents was evaluated, demonstrating that this strategy efficiently solubilized proteins embedded in IBs while retaining their biological activity. These results showed that the protocol used for IB solubilization has an impact on final protein quality and that IBs can be solubilized through a very simple step, obtaining fully active proteins.

The future of recombinant host defense peptides

The antimicrobial resistance crisis calls for the discovery and production of new antimicrobials. Host defense peptides (HDPs) are small proteins with potent antibacterial and immunomodulatory activities that are attractive for translational applications, with several already under clinical trials. Traditionally, antimicrobial peptides have been produced by chemical synthesis, which is expensive and requires the use of toxic reagents, hindering the large-scale development of HDPs. Alternatively, HDPs can be produced recombinantly to overcome these limitations. Their antimicrobial nature, however, can make them toxic to the hosts of recombinant production. In this review we explore the different strategies that are used to fine-tune their activities, bioengineer them, and optimize the recombinant production of HDPs in various cell factories.