Advances in analytical methodologies to guide bioprocess engineering for bio-therapeutics

Identification of a type II LacNAc specific binding lectin CMRBL from Cordyceps militaris

The Cordyceps militaris gene CCM_03832 encodes a ricin-B like lectin. The gene was cloned and expressed in Escherichia coli, and its protein product, named CMRBL (C. militaris ricin-B like lectin), was purified by galactose affinity chromatography. Of nine different sources of erythrocytes, CMRBL showed only specific hemagglutinating activity against rat and rabbit erythrocytes with titers of 2² and 2⁸, respectively. Glycan array analyses by the Consortium for Functional Glycomics showed that CMRBL possesses very high specific binding activity of glycans terminated with type II LacNAc (non-reducing Galβ1-4GlcNAc). Compared with other well-known Gal-terminated binding lectins such as Erythrina cristagalli agglutinin, Ricinus communis agglutinin, and Jacalin, CMRBL showed better binding specificity to type II LacNAc compared the other lectins. CMRBL showed lowest binding activity to ZR-75-30 and MDA-MB-468 cell lines among five tested cell lines (H22, THP-1, MDA-MB-231, ZR-75-30, and MDA-MB-468 cells). Transfection of type II LacNAc main galactosyltransferase B4GALT3 to ZR-75-30 significantly improved CMRBL binding activity compared with control. CMRBL was also applied for testing the type II LacNAc modification of Etanercept successfully. Our data suggest that CMRBL would be a useful tool to recognize type II LacNAc, especially distinguish type II from other galactose-terminated glycans in glycan biology research.

Comprehensive N- and O-Glycoproteomic Analysis of Multiple Chinese Hamster Ovary Host Cell Lines

Glycoproteomic analysis of three Chinese hamster ovary (CHO) suspension host cell lines (CHO-K1, CHO-S, and CHO-Pro5) commonly utilized in biopharmaceutical settings for recombinant protein production is reported. Intracellular and secreted glycoproteins were examined. We utilized an immobilization and chemoenzymatic strategy in our analysis. Glycoproteins or glycopeptides were first immobilized through reductive amination, and the sialyl moieties were amidated for protection. The desired N- or O-glycans and glycopeptides were released from the immobilization resin by enzymatic or chemical digestion. Glycopeptides were studied by Orbitrap Liquid chromatography-mass spectrometry (LC/MS), and the released glycans were analyzed by Matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF). Differences were detected in the relative abundances of N- and O-glycopeptide types, their resident and released glycans, and their glycoprotein complexity. Ontogeny analysis revealed key differences in features, such as general metabolic and biosynthetic pathways, including glycosylation systems, as well as distributions in cellular compartments. Host cell lines and subfraction differences were observed in both N- and O-glycan and glycoprotein pools. Differences were observed in sialyl and fucosyl glycan distributions. Key differences were also observed among glycoproteins that are problematic contaminants in recombinant antibody production. The differences revealed in this study should inform the choice of cell lines best suited for a particular bioproduction application.

Discrepancies between High-Resolution Native and Glycopeptide-Centric Mass Spectrometric Approaches: A Case Study into the Glycosylation of Erythropoietin Variants

Glycosylation represents a critical quality attribute modulating a myriad of physiochemical properties and effector functions of biotherapeutics. Furthermore, a rising landscape of glycosylated biotherapeutics including biosimilars, biobetters, and fusion proteins harboring complicated and dynamic glycosylation profiles requires tailored analytical approaches capable of characterizing their heterogeneous nature. In this work, we perform in-depth evaluation of the glycosylation profiles of three glycoengineered variants of the widely used biotherapeutic erythropoietin. We analyzed these samples in parallel using a glycopeptide-centric liquid chromatography/mass spectrometry approach and high-resolution native mass spectrometry. Although for all of the studied variants the glycopeptide and native mass spectrometry data were in good qualitative agreement, we observed substantial quantitative differences arising from ionization deficiencies and unwanted neutral losses, in particular, for sialylated glycopeptides in the glycoproteomics approach. However, the latter provides direct information about glycosite localization. We conclude that the combined parallel use of native mass spectrometry and bottom-up glycoproteomics offers superior characterization of glycosylated biotherapeutics and thus provides a valuable attribute in the characterization of glycoengineered proteins and other complex biotherapeutics.

Elastin-like recombinamers-based hydrogel modulates post-ischemic remodeling in a non-transmural myocardial infarction in sheep

Ischemic heart disease is a leading cause of mortality due to irreversible damage to cardiac muscle. Inspired by the post-ischemic microenvironment, we devised an extracellular matrix (ECM)-mimicking hydrogel using catalyst-free click chemistry covalent bonding between two elastin-like recombinamers (ELRs). The resulting customized hydrogel included functional domains for cell adhesion and protease cleavage sites, sensitive to cleavage by matrix metalloproteases overexpressed after myocardial infarction (MI). The scaffold permitted stromal cell invasion and endothelial cell sprouting in vitro. The incidence of non-transmural infarcts has increased clinically over the past decade, and there is currently no treatment preventing further functional deterioration in the infarcted areas. Here, we have developed a clinically relevant ovine model of non-transmural infarcts induced by multiple suture ligations. Intramyocardial injections of the degradable ELRs-hydrogel led to complete functional recovery of ejection fraction 21 days after the intervention. We observed less fibrosis and more angiogenesis in the ELRs-hydrogel-treated ischemic core region compared to the untreated animals, as validated by the expression, proteomic, glycomic, and histological analyses. These findings were accompanied by enhanced preservation of GATA4⁺ cardiomyocytes in the border zone of the infarct. We propose that our customized ECM favors cardiomyocyte preservation in the border zone by modulating the ischemic core and a marked functional recovery. The functional benefits obtained by the timely injection of the ELRs-hydrogel in a clinically relevant MI model support the potential utility of this treatment for further clinical translation.

Routine Analysis of N-Glycans Using Liquid Chromatography Coupled to Routine Mass Detection

Analysis of N-glycans are commonly conducted via enzymatic release, labeling, and liquid chromatography (LC) separation and fluorescent detection. Mass spectrometry (MS) has been increasingly used as an orthogonal detection method to provide additional structural information and increase the confidence of N-glycan analysis. In this chapter, we describe a method to perform routine analysis of N-glycans including the sample preparation with a signal-enhancement label, LC-MS data generation, and data analysis. Using this method, up to 24 N-glycan samples can be prepared at one time and analyzed by LC-MS. With the addition of automation platform, up to 96 N-glycan samples can be prepared and analyzed in a high-throughput manner.

Region-Specific Characterization of N-Glycans in the Striatum and Substantia Nigra of an Adult Rodent Brain

N-glycan alterations in the nervous system can result in different neuropathological symptoms such as mental retardation, seizures, and epilepsy. Studies have reported the characterization of N-glycans in rodent brains, but there is a lack of spatial resolution as either the tissue samples were homogenized or specific proteins were selected for analysis of glycosylation. We hypothesize that region-specific resolution of N-glycans isolated from the striatum and substantia nigra (SN) can give an insight into the establishment and pathophysiological degeneration of neural circuitry in Parkinson's disease. Specific objectives of the study include isolation of N-glycans from the rat striatum and SN; reproducibility, resolution, and relative quantitation of N-glycome using ultra-performance liquid chromatography (UPLC), weak anion exchange-UPLC, and lectin histochemistry. The total N-glycomes from the striatum and SN were characterized using database mining (GlycoStore), exoglycosidase digestions, and liquid chromatography-mass spectrometry. It revealed significant differences in complex and oligomannose type N-glycans, sialylation (mono-, di-, and tetra-), fucosylation (tri-, core, and outer arm), and galactosylation (di-, tri-, and tetra-) between striatum and SN N-glycans with the detection of phosphorylated N-glycans in SN which were not detected in the striatum. This study presents the most comprehensive comparative analysis of relative abundances of N-glycans in the striatum and SN of rodent brains, serving as a foundation for identifying "brain-type" glycans as biomarkers or therapeutic targets and their modulation in neurodegenerative disorders.

Discovery of Highly Active Recombinant PNGase H+ Variants Through the Rational Exploration of Unstudied Acidobacterial Genomes

Peptide-N ⁴-(N-acetyl-β-glucosaminyl) asparagine amidases (PNGases, N-glycanases, EC 3.5.1.52) are indispensable tools in releasing N-glycans from glycoproteins. So far, only a limited number of PNGase candidates are available for the structural analysis of glycoproteins and their glycan moieties. Herein, a panel of 13 novel PNGase H⁺ candidates (the suffix H⁺ refers to the acidic pH optimum of these acidobacterial PNGases) was tested in their recombinant form for their deglycosylation performance. One candidate (originating from the bacterial species Dyella japonica) showed superior properties both in solution-phase and immobilized on amino-, epoxy- and nitrilotriacetate resins when compared to currently acidic available PNGases. The high expression yield compared to a previously described PNGase H⁺, broad substrate specificity, and good storage stability of this novel N-glycanase makes it a valuable tool for the analysis of protein glycosylation.

Distinct glycosylation in membrane proteins within neonatal versus adult myocardial tissue

Mammalian hearts have regenerative potential restricted to early neonatal stage and lost within seven days after birth. Carbohydrates exclusive to cardiac neonatal tissue may be key regulators of regenerative potential. Although cell surface and extracellular matrix glycosylation are known modulators of tissue and cellular function and development, variation in cardiac glycosylation from neonatal tissue to maturation has not been fully examined. In this study, glycosylation of the adult rat cardiac ventricle showed no variability between the two strains analysed, nor were there any differences between the glycosylation of the right or left ventricle using lectin histochemistry and microarray profiling. However, in the Sprague-Dawley strain, neonatal cardiac glycosylation in the left ventricle differed from adult tissues using mass spectrometric analysis, showing a higher expression of high mannose structures and lower expression of complex N-linked glycans in the three-day-old neonatal tissue. Man₆GlcNAc₂ was identified as the main high mannose N-linked structure that was decreased in adult while higher expression of sialylated N-linked glycans and lower core fucosylation for complex structures were associated with ageing. The occurrence of mucin core type 2 O-linked glycans was reduced in adult and one sulfated core type 2 O-linked structure was identified in neonatal tissue. Interestingly, O-linked glycans from mature tissue contained both N-acetylneuraminic acid (Neu5Ac) and N-glycolylneuraminic acid (Neu5Gc), while all sialylated N-linked glycans detected contained only Neu5Ac. As glycans are associated with intracellular communication, the specific neonatal structures found may indicate a role for glycosylation in the neonatal associated regenerative capacity of the mammalian heart. New strategies targeting tissue glycosylation could be a key contributor to achieve an effective regeneration of the mammalian heart in pathological scenarios such as myocardial infarction.

Analyzing protein glycosylation using UHPLC: a review

Ultrahigh performance liquid chromatography (UHPLC) uses small stationary-phase particle size (<2 μm) and high pressure in order to achieve rapid and efficient separations. The speed and high resolution of this method has made it a valuable tool for analyzing the complex glycosylation patterns found in post-translationally modified proteins. This article highlights the differences between UHPLC and HPLC and reviews recent UHPLC applications and developments for detecting glycosylated proteins (e.g., glycomics studies) and characterizing glycosylated pharmaceuticals (e.g., monoclonal antibodies).