Every animal secretes mucus, placing them among the most diverse biological materials. Mucus hydrogels are complex mixtures of water, ions, carbohydrates, and proteins. Uncertainty surrounding their composition and how interactions between components contribute to mucus function complicates efforts to exploit their properties. There is substantial interest in commercializing mucus from the garden snail, Cornu aspersum, for skincare, drug delivery, tissue engineering, and composite materials. C. aspersum secretes three mucus—one shielding the animal from environmental threats, one adhesive mucus from the pedal surface of the foot, and another pedal mucus that is lubricating. It remains a mystery how compositional differences account for their substantially different properties. Here, we characterize mucus proteins, glycosylation, ion content, and mechanical properties that could be used to provide insight into structure-function relationships through an integrative “mucomics” approach. We identify macromolecular components of these hydrogels, including a previously unreported protein class termed Conserved Anterior Mollusk Proteins (CAMPs). Revealing differences between C. aspersum mucus shows how considering structure at all levels can inform the design of mucus-inspired materials.

Biosynthesis of macromolecules requires precursors such as sugars or amino acids, originating from exogenous/dietary sources, reutilization/salvage of degraded molecules, or de novo synthesis. Since these sources are assumed to contribute to one homogenous pool, their individual contributions are often overlooked. Protein glycosylation uses monosaccharides from all the above sources to produce nucleotide sugars required to assemble hundreds of distinct glycans. Here, we demonstrate that cells identify the origin/heritage of the monosaccharide, fucose, for glycosylation. We measured the contribution of GDP-fucose from each of these sources for glycan synthesis and found that different fucosyltransferases, individual glycoproteins, and linkage-specific fucose residues identify and select different GDP-fucose pools dependent on their heritage. This supports the hypothesis that GDP-fucose exists in multiple, distinct pools, not as a single homogenous pool. The selection is tightly regulated since the overall pool size remains constant. We present novel perspectives on monosaccharide metabolism, which may have a general applicability.

Root-knot nematodes (RKN) ( Meloidogyne spp.) represent one of the most damaging groups of plant-parasitic nematodes. They secrete effector proteins through a protrusible stylet to manipulate host cells for their benefit. Stylet-secreted effector proteins are produced within specialized secretory esophageal gland cells, one dorsal gland (DG) and two subventral glands (SvG), whose activity differ throughout the nematode life cycle. Previous gland transcriptomic profiling studies identified dozens of candidate RKN effectors but were focused on the juvenile stages of the nematode, when the SvGs are most active. We developed a new approach to enrich for the active DGs of M. incognita adult female RKN for RNA and protein extraction. Female heads were manually cut from the body, and a combination of sonication and vortexing was used to dislodge contents inside the heads. DG-enriched fractions were collected by filtering, using cell strainers. Comparative transcriptome profiling of pre-parasitic second-stage juveniles, female heads, and DG-enriched samples was conducted using RNA sequencing. Application of an established effector mining pipeline led to the identification of 83 candidate effector genes upregulated in DG-enriched samples of adult females that code for proteins with a predicted signal peptide but lack transmembrane domains or homology to proteins in the free-living nematode Caenorhabditis elegans. In situ hybridization resulted in the identification of 14 new DG-specific candidate effectors expressed in adult females. Taken together, we have identified novel candidate Meloidogyne effector genes that may have essential roles during later stages of parasitism. [ ] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Nature is rich with examples of highly specialized biological materials produced by organisms for functions, including defense, hunting, and protection. Along these lines, velvet worms (Onychophora) expel a protein-based slime used for hunting and defense that upon shearing and dehydration forms fibers as stiff as thermoplastics. These fibers can dissolve back into their precursor proteins in water, after which they can be drawn into new fibers, providing biological inspiration to design recyclable materials. Elevated phosphorus content in velvet worm slime was previously observed and putatively ascribed to protein phosphorylation. Here, we show instead that phosphorus is primarily present as phosphonate moieties in the slime of distantly related velvet worm species. Using high-resolution nuclear magnetic resonance (NMR), natural abundance dynamic nuclear polarization (DNP), and mass spectrometry (MS), we demonstrate that 2-aminoethyl phosphonate (2-AEP) is associated with glycans linked to large slime proteins, while transcriptomic analyses confirm the expression of 2-AEP synthesizing enzymes in slime glands. The evolutionary conservation of this rare protein modification suggests an essential functional role of phosphonates in velvet worm slime and should stimulate further study of the function of this unusual chemical modification in nature.

Identification of N‐ and O‐glycosylation on specific sites of proteins, along with glycan structural information, is necessary to determine the roles glycoproteins play in normal and pathologic cellular functions. Because such glycosylation is macro‐ and micro‐heterogeneous and alters the dissociation behavior of glycopeptides, specific sample preparation, mass spectrometry, and data analysis techniques are required. Advanced tandem mass spectrometry–based glycoproteomics coupled with powerful data mining algorithms are key elements for characterization of protein glycosylation. This article includes the detailed, streamlined sample preparation method for liquid chromatography–mass spectrometry data acquisition and subsequent bioinformatics‐based data annotation using the publicly available GlycReSoft program for highly efficient identification and quantification of glycoprotein glycosylation. © 2021 Wiley Periodicals LLC.This article was corrected on 25 July 2022. See the end of the full text for details.Basic Protocol 1: Characterization of glycans and site occupancy on purified glycoproteinSupport Protocol 1: In‐gel digestion of glycoproteinsSupport Protocol 2: Detection of glycoproteins from cells/tissue through glycopeptide enrichmentBasic Protocol 2: Acquisition of glycopeptides through high‐resolution nano‐LC‐MS/MSBasic Protocol 3: Identification and quantification of glycopeptides using GlycReSoft

The coronavirus disease 2019 (COVID‐19) pandemic is an ongoing global public health crisis. The causative agent, the SARS‐CoV‐2 virus, enters host cells via molecular interactions between the viral spike protein and the host cell ACE2 surface protein. The SARS‐CoV‐2 spike protein is extensively decorated with up to 66 N‐linked glycans. Glycosylation of viral proteins is known to function in immune evasion strategies but may also function in the molecular events of viral entry into host cells. Here, we show that N‐glycosylation at Asn331 and Asn343 of SARS‐CoV‐2 spike protein is required for it to bind to ACE2 and for the entry of pseudovirus harboring the SARS‐CoV‐2 spike protein into cells. Interestingly, high‐content glycan binding screening data have shown that N‐glycosylation of Asn331 and Asn343 of the RBD is important for binding to the specific glycan molecule G4GN (Galβ−1,4 GlcNAc), which is critical for spike‐RBD‐ACE2 binding. Furthermore, IL‐6 was identified through antibody array analysis of conditioned media of the corresponding pseudovirus assay. Mutation of N‐glycosylation of Asn331 and Asn343 sites of the spike receptor‐binding domain (RBD) significantly reduced the transcriptional upregulation of pro‐inflammatory signaling molecule IL‐6. In addition, IL‐6 levels correlated with spike protein levels in COVID‐19 patients' serum. These findings establish the importance of RBD glycosylation in SARS‐CoV‐2 pathogenesis, which can be exploited for the development of novel therapeutics for COVID‐19.