Deglycosylation by the Acidic Glycosidase PNGase H+ Enables Analysis of N-Linked Glycoproteins by Hydrogen/Deuterium Exchange Mass Spectrometry

Hydrogen/deuterium exchange monitored by mass spectrometry (HDX-MS) has become an important method to study the structural dynamics of proteins. However, glycoproteins represent a challenge to the traditional HDX-MS workflow for determining the deuterium uptake of the protein segments that contain the glycan. We have recently demonstrated the utility of the glycosidase PNGase A to enable HDX-MS analysis of N-glycosylated protein regions. Here, we have investigated the use of the acidic glycosidase PNGase H⁺, which has a pH optimum at 2.6, to efficiently deglycosylate N-linked glycosylated peptides during HDX-MS analysis of glycoproteins. Our results show that PNGase H⁺ retains high deglycosylation activity at HDX quench conditions. When used in an HDX-MS workflow, PNGase H⁺ allowed the extraction of HDX data from all five glycosylated regions of the serpin α₁-antichymotrypsin. We demonstrate that PNGase A and PNGase H⁺ are capable of similar deglycosylation performance during HDX-MS analysis of α₁-antichymotrypsin and the IgG1 antibody trastuzumab (TZ). However, PNGase H⁺ provides broader specificity and greater tolerance to the disulfide-bond reducing agent TCEP, while PNGase A offers advantages in terms of commercial availability and purity. Overall, our findings demonstrate the unique features of PNGase H⁺ for improving conformational analysis of glycoproteins by HDX-MS, in particular, challenging glycoproteins containing both glycosylations and disulfide bonds.

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.

Analysis of N-glycans from Raphanus sativus Cultivars Using PNGase H

In recent years, the carbohydrate moieties of plants have received considerable attention, as they are a potential source of cross-reactive, allergy-provoking immune responses. In addition, carbohydrate structures also play a critical role in plant metabolism. Here, we present a simple and rapid method for preparing and analyzing N-glycans from different cultivars of radish (Raphanus sativus) using an N-glycanase specific for the release of plant-derived carbohydrate structures. To achieve this, crude trichloroacetic acid precipitates of radish homogenates were treated with PNGase H⁺, and labeled using 2-aminobenzamide as a fluorescent tag. The labeled N-glycan samples were subsequently analyzed by ultra performance liquid chromatography (UPLC) separation and matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry for a detailed structural evaluation and to quantify relative abundancies of the radish-derived N-glycan structures. This protocol can also be used for the analysis of N-glycans from various other plant species, and may be useful for further investigation of the function and effects of N-glycans on human health.

Double-balloon catheter versus prostaglandin E2 for cervical ripening and labour induction: a systematic review and meta-analysis of randomised controlled trials

BACKGROUND

Induction of labour has become an increasingly common procedure. Ripening methods, including mechanical devices and pharmacological agents, improve the success rate of labour induction.

OBJECTIVE

To compare the efficacy and safety of the double-balloon catheter with prostaglandin E2 agents used for labour induction.

SEARCH STRATEGY

We searched electronic sources from MEDLINE, Embase and Web of Science, the Cochrane Library Database of Systematic Reviews, and ClinicalTrials.gov website.

SELECTION CRITERIA

Only randomised controlled trials comparing the PGE2 agents with the double-balloon catheter for cervical ripening and labour induction in women with unfavourable cervices were included in the analysis.

DATA COLLECTION AND ANALYSIS

The main outcomes included the vaginal delivery rate within 24 hours and risk of caesarean section. We calculated relative risks and mean differences using fixed- and random-effects models.

MAIN RESULTS

Nine studies (1866 patients) were included in this systematic review. Both the double-balloon catheter and PGE2 agents were comparable with regard to rate of caesarean section (RR 0.92; 95% CI 0.79, 1.07), vaginal delivery within 24 hours (RR 0.95; 95% CI 0.78, 1.16) and maternal adverse events, but the risk of excessive uterine activity (RR 10.02; 95% CI 3.99, 25.17) and need for neonatal intensive care unit admissions (RR 1.31; 95% CI 1.01, 1.69) were significantly increased in women who received PGE2 agents.

CONCLUSIONS

The double-balloon catheter demonstrated greater safety and cost-effectiveness than PGE2 agents for cervical ripening and labour induction. The efficacy profiles of both methods were similar.

TWEETABLE ABSTRACT

Double-balloon catheter versus prostaglandin E2 for cervical ripening and labour induction.

Transmembrane 7 superfamily member 4 regulates cell cycle progression in breast cancer cells

OBJECTIVE

TM7SF4 (transmembrane 7 superfamily member 4) gene encodes a seven-pass transmembrane protein that is primarily expressed in dendritic cells called as dendritic cell-specific expressed seven transmembrane protein (DC-STAMP). This protein regulates immunological functions, osteoclastogenesis and myeloid differentiation. Although the roles of TM7SF4 have been currently studied on Paget's disease of bone and papillary thyroid cancers, it is unclear whether TM7SF4 plays a role in breast cancer. In current study, we investigated the expression of TM7SF4 in human breast cancer cell lines.

MATERIALS AND METHODS

In this study, five breast cancer lines were cultured. Small hairpin RNA against TM7SF4 using a lentiviral vector was generated and transfected into MCF-7 breast cancer cells. Effects of down-regulating TM7SF4 in transfected cells were examined by Western blot, RT-PCR, apoptotic rate, colony formation, and cell cycle analyses.

RESULTS

The results demonstrated that down-regulation of TM7SF4 led to a decrease in colony formation in MCF-7 cells compared to the control group. This is likely due to a decrease in proliferation and cell cycle and an increase in apoptosis.

CONCLUSIONS

To our knowledge, our data demonstrate for the first time that TM7SF4 plays an essential role in regulating cell cycle progression in breast cancer.