Constitutive expression of recombinant human hyaluronidase PH20 by Pichia pastoris

Engineering protein translocation and unfolded protein response enhanced human PH-20 secretion in Pichia pastoris

Hyaluronidases catalyze the degradation of hyaluronan (HA), which is finding rising applications in medicine, cosmetic, and food industries. Recombinant expression of hyaluronidases in microbial hosts has been given special attention as a sustainable way to substitute animal tissue-derived hyaluronidases. In this study, we focused on optimizing the secretion of hyaluronidase from Homo sapiens in Pichia pastoris by secretion pathway engineering. The recombinant hyaluronidase was first expressed under the control of a constitutive promoter PGCW14. Then, two endoplasmic reticulum-related secretory pathways were engineered to improve the secretion capability of the recombinant strain. Signal peptide optimization suggested redirecting the protein into co-translational translocation using the ost1-proα signal sequence improved the secretion level by 20%. Enhancing the co-translational translocation by overexpressing signal recognition particle components further enhanced the secretory capability by 48%. Then, activating the unfolded protein response by overexpressing a transcriptional factor ScHac1p led to a secreted hyaluronidase activity of 4.06 U/mL, which was 2.1-fold higher than the original strain. Finally, fed-batch fermentation elevated the production to 19.82 U/mL. The combined engineering strategy described here could be applied to enhance the secretion capability of other proteins in yeast hosts. KEY POINTS: • Improving protein secretion by enhancing co-translational translocation in P. pastoris was reported for the first time. • Overexpressing Hac1p homologous from different origins improved the rhPH-20 secretion. • A 4.9-fold increase in rhPH-20 secretion was achieved after fermentation optimization and fed-batch fermentation.

Zinc-Iron Bimetallic Peroxides Modulate the Tumor Stromal Microenvironment and Enhance Cell Immunogenicity for Enhanced Breast Cancer Immunotherapy Therapy

Immunotherapy has emerged as a potential approach for breast cancer treatment. However, the rigid stromal microenvironment and low immunogenicity of breast tumors strongly reduce sensitivity to immunotherapy. To sensitize patients to breast cancer immunotherapy, hyaluronic acid-modified zinc peroxide-iron nanocomposites (Fe-ZnO2@HA, abbreviated FZOH) were synthesized to remodel the stromal microenvironment and increase tumor immunogenicity. The constructed FZOH spontaneously generated highly oxidative hydroxyl radicals (·OH) that degrade hyaluronic acid (HA) in the tumor extracellular matrix (ECM), thereby reshaping the tumor stromal microenvironment and enhancing blood perfusion, drug penetration, and immune cell infiltration. Furthermore, FZOH not only triggers pyroptosis through the activation of the caspase-1/GSDMD-dependent pathway but also induces ferroptosis through various mechanisms, including increasing the levels of Fe2+ in the intracellular iron pool, downregulating the expression of FPN1 to inhibit iron efflux, and activating the p53 signaling pathway to cause the failure of the SLC7A11-GSH-GPX4 signaling axis. Upon treatment with FZOH, 4T1 cancer cells undergo both ferroptosis and pyroptosis, exhibiting a strong immunogenic response. The remodeling of the tumor stromal microenvironment and the immunogenic response of the cells induced by FZOH collectively compensate for the limitations of cancer immunotherapy and significantly enhance the antitumor immune response to the immune checkpoint inhibitor αPD-1. This study proposes a perspective for enhancing immune therapy for breast cancer.

Cell-free reduction of carboxylic acids with secreted carboxylic acid reductase

Mycobacterium marinum CAR (MmCAR) is one of the most widely used CARs as the key enzyme for the synthesis of aldehydes, alcohols and further products from the respective carboxylic acids. Herein, we describe the first functionally secreted 131 kDa CAR and its isolated A-domain using Komagataella phaffii and a methanol-free constitutive expression strategy. Precipitated and lyophilized MmCAR (500 µg) was isolated from the culture supernatant and showed no decrease in activity for piperonylic acid (80% conversion), even when stored for up to 3 weeks at 4°C. Lyophilized MmCAR precipitate gave 48% yield of E/Z-nonanal-4-nitrobenzoyloxime from the reduction of nonanoic acid and in-situ derivatization with O-4-nitrobenzoyl-hydroxylamine. Furthermore, K. phaffii could successfully secrete the MmCAR adenylation domain. Its activity was confirmed by the amidation of benzoic acid with n-hexylamine. Neither enzyme variant was glycosylated by the yeast. In summary, functional CAR can be secreted by K. phaffii and used for cell free conversion of carboxylic acids to various products.

Fine-Tuned Gene Expression Elements from Hybrid Promoter Libraries in Pichia pastoris

As a desirable microbial cell factory, Pichia pastoris has garnered extensive utilization in metabolic engineering. Nevertheless, the lack of fine-tuned gene expression components has significantly constrained the potential scope of applications. Here, a gradient strength promoter library was constructed by random hybridization and high-throughput screening. The hybrid promoter, phy47, performed best with 2.93-fold higher GFP expression levels than GAP. The broad applicability of the novel hybrid promoter variants in biotechnological production was further validated in the biosynthesis of pinene and rHuPH20 with higher titers. The upstream regulatory sequences (UASE and URSD) were identified and applied to promoters GAP and ENO1, resulting in a 34 and 43% increase and an 18 and 37% decrease in the expression level, respectively. Yeast one-hybrid analysis showed that transcription factor HAP2 activates the hybrid promoter through a direct interaction with the crucial regulatory region UASH. Furthermore, a short segment of tunable activation sequence (20 bp) was also screened, and artificial promoters were constructed in tandem with the addition of regulatory sequence, resulting in a 61% expansion of the expression range. This study provides a molecular tool and regulatory elements for further synthetic biology research in P. pastoris.

Enzymatic Production of Low-Molecular-Weight Hyaluronan and Its Oligosaccharides: A Review and Prospects

Hyaluronic acid (HA) is a nonsulfated linear glycosaminoglycan with a negative charge. Different from the high-molecular-weight HAs, the low-molecular-weight HAs (LMW-HAs, 4-120 kDa) and hyaluronan oligosaccharides (O-HAs, <4 kDa) exhibit certain unique biological properties, owing to which these have a wide range of applications in the field of medicine. However, the chemical synthesis of high-purity LMW-HAs and O-HAs requires complex procedures, which renders this process difficult to achieve. The degradation of HA is achieved under the catalysis of hyaluronidases. In recent years, various hyaluronidase genes have been identified, and their enzymatic properties have been analyzed. In this context, the present review summarizes the hyaluronidases from different sources, which have been characterized. The review focuses on the crystal structure and the catalytic mechanism underlying the biological properties of hyaluronidases. In addition, the molecular weight distributions and the preparation approaches of the enzymatic products LMW-HAs and O-HAs are described. The general orientation of the research on hyaluronidases was speculated based on the existing literature. Accordingly, the efficient large-scale production of LMW-HAs and O-HAs using the green enzymatic approach was anticipated.

Insights into the source, mechanism and biotechnological applications of hyaluronidases

It has long been found that hyaluronidases exist in a variety of organisms, playing their roles in various biological processes including infection, envenomation and metabolic regulation through degrading hyaluronan. However, exploiting them as a bioresource for specific applications had not been extensively studied until the latest decades. In recent years, new application scenarios have been developed, which extended the field of application, and emphasized the research value of hyaluronidase. This critical review comprehensively summarizes existing studies on hyaluronidase from different source, particularly in their structures, action patterns, and biological functions in human and mammals. Furthermore, we give in-depth insight into the resource mining and protein engineering process of hyaluronidase, as well as strategies for their high-level production, indicating that mixed strategies should be adopted to obtain well-performing hyaluronidase with efficiency. In addition, advances in application of hyaluronidase were summarized and discussed. Finally, prospects for future researches are proposed, highlighting the importance of further investigation into the characteristics of hyaluronidases, and the necessity of investigating their products for the development of their application value.

Active Expression of Human Hyaluronidase PH20 and Characterization of Its Hydrolysis Pattern

Hyaluronidases are a group of glycosidases catalyzing the degradation of hyaluronic acid (HA). Because of the advantages of effectively hydrolyzing the HA-rich matrix and low immunogenicity, human hyaluronidase PH20 (hPH20) is widely used in the medical field. Here, we realized the active expression of recombinant hPH20 by Pichia pastoris under a methanol-induced promoter PAOX1. By optimizing the composition of the C-terminal domain and fusing protein tags, we constructed a fusion mutant AP2-△491C with the extracellular hyaluronidase activity of 258.1 U·L-1 in a 3-L bioreactor, the highest expression level of recombinant hPH20 produced by microbes. Furthermore, we found recombinant hPH20 hydrolyzed the β-1,4 glycosidic bonds sequentially from the reducing end of o-HAs, with HA6 NA as the smallest substrate. The result will provide important theoretical guidance for the directed evolution of the enzyme to prepare multifunctional o-HAs with specific molecular weights.

Site-specific integration as an efficient method for production of recombinant human hyaluronidase PH20 in semi-adherent cells

PH20 is a hyaluronidase enzyme that can hydrolyze the glycosidic bond in hyaluronic acid as the major proteoglycan found in extracellular matrices. In the present study, we constructed and characterized two donor plasmids, one of them with one and the second with two PH20 expression cassettes. The expression vectors were site specifically integrated into the genome of HEK293T cells using PhiC31 integrase system to develop HEK293T stable cell lines secreting His-tagged recombinant human PH20 (rhPH20) in the culture supernatant. The produced rhPH20 was quantified using ELISA and turbidimetric assay tests, and its catalytic activity was also assessed by treating the mouse cumulus-oocyte complexes. Our results showed that the secreted rhPH20 in the culture supernatant had the specific activity of 16,660 IU/mg and the recombinant enzyme was able to remove the cumulus cells from oocytes. The results also indicated that phiC31 enzyme inserted the PH20-expressing donor vectors into the specific pseudo attP sites including 10q21.2 and 20q11.22 in the genome of the target cells with different copy numbers. Taken together, our findings demonstrate that PhiC31 integrase system is able to be applied as a robust tool for efficient production and secretion of soluble and active rhPH20 by HEK293T cells as a semi-adherent human cell line. KEY POINTS: • Efficient production of human recombinant PH20 in a semi-adherent human cell line • Successful application of PhiC31 integrase system for generation of stable recombinant clones • Use of a human cell line for expression of a recombinant human protein due to complex and efficient post-translational modifications and protein folding.

Engineered Bacteria Enhance Immunotherapy and Targeted Therapy through Stromal Remodeling of Tumors

Desmoplastic solid tumors are characterized by the rapid build-up of extracellular matrix (ECM) macromolecules, such as hyaluronic acid (HA). The resulting physiological barrier prevents the infiltration of immune cells and also impedes the delivery of anticancer agents. The development of a hypervesiculating Escherichia coli Nissle (ΔECHy) based tumor targeting bacterial system capable of distributing a fusion peptide, cytolysin A (ClyA)-hyaluronidase (Hy) via outer membrane vesicles (OMVs) is reported. The capability of targeting hypoxic tumors, manufacturing recombinant proteins in situ and the added advantage of an on-site OMV based distribution system makes the engineered bacterial vector a unique candidate for peptide delivery. The HA degrading potential of Hy for stromal modulation is combined with the cytolytic activity of ClyA followed by testing it within syngeneic cancer models. ΔECHy is combined with immune checkpoint antibodies and tyrosine kinase inhibitors (TKIs) to demonstrate that remodeling the tumor stroma results in the improvement of immunotherapy outcomes and enhancing the efficacy of biological signaling inhibitors. The biocompatibility of ΔECHy is also investigated to show that the engineered bacteria are effectively cleared, elicit minimal inflammatory and immune responses, and therefore could be a reliable candidate as a live biotherapeutic.

Hyaluronidases and hyaluronate lyases: From humans to bacteriophages

Hyaluronan is a non-sulfated negatively-charged linear polymer distributed in most parts of the human body, where it is located around cells in the extracellular matrix of connective tissues and plays an essential role in the organization of tissue architecture. Moreover, hyaluronan is involved in many biological processes and used in many clinical, cosmetic, pharmaceutic, and biotechnological applications worldwide. As interest in hyaluronan applications increases, so does interest in hyaluronidases and hyaluronate lyases, as these enzymes play a major part in hyaluronan degradation. Many hyaluronidases and hyaluronate lyases produced by eukaryotic cells, bacteria, and bacteriophages have so far been described and annotated, and their ability to cleave hyaluronan has been experimentally proven. These enzymes belong to several carbohydrate-active enzyme families, share very low sequence identity, and differ in their cleaving mechanisms and in their structural and functional properties. This review presents a summary of annotated and characterized hyaluronidases and hyaluronate lyases isolated from different sources belonging to distinct protein families, with a main focus on the binding and catalytic residues of the discussed enzymes in the context of their biochemical properties. In addition, the application potential of individual groups of hyaluronidases and hyaluronate lyases is evaluated.

Current advances in the biosynthesis of hyaluronic acid with variable molecular weights

Hyaluronic acid (HA) is a naturally formed acidic mucopolysaccharide, with excellent moisturising properties and used widely in the medicine, cosmetics, and food industries. The industrial production of specific molecular weight HA has become imperative. Different biological activities and physiological functions of HA mainly depend on the degree of polymerisation. This article reviews the research status and development prospects of the green biosynthesis and molecular weight regulation of HA. There is an application-based prerequisite of specific molecular weight of HA that could be regulated either during the fermentation process or via a controlled HA degradation process. This work provides an important theoretical basis for the downstream efficient production of diversified HA, which will further accelerate the research applications of HA and provide a good scientific basis and method reference for the study of the molecular weight regulation of similar biopolymers.