Biology subjects

Schwenk, J.

Publications and source records attributed to Schwenk, J..

8 recordsLinked to original sources

bioRxiv2026

Distribution, assembly and mechanism of GluN1/GluN3A excitatory glycine receptors

NMDA receptors play key roles in brain development, plasticity and diseases. While glutamate and glycine co-gated GluN2-containing NMDARs have been extensively characterized, little is known regarding GluN3A-containing NMDARs that form receptors gated by glycine only. Here, combining native purification, mass spectrometry, cryo-EM and electrophysiology, we provide key insights on the molecular logic of GluN3A-NMDARs. We demonstrate that native GluN3A receptors account for a sizeable fraction of total NMDARs, are enriched at extrasynaptic compartments in the adult brain, and assemble specifically as diheteromeric GluN1/GluN3A excitatory glycine receptors (eGlyRs) rather than as triheteromeric GluN1/GluN2/GluN3A receptors. The architecture of eGlyRs reveal splayed and loosely packed extracellular domains, strikingly different from conventional GluN1/GluN2 receptors. Through back-and- forth structural and functional validations, we demonstrate how the combined effects of a weak ligand-binding domain (LBD) dimer interface and high intrinsic mobility of the N-terminal domains (NTDs) shape the atypical gating of eGlyRs. These findings illuminate GluN3A-NMDAR physiology and mechanism, with implications for neuronal signaling and pharmacology.

neuroscience↗

bioRxiv2024

Longitudinal blood microsampling and proteome monitoring facilitate timely intervention in experimental type 1 diabetes

Symptoms of immune-mediated diseases (IMIDs) typically appear after irreversible tissue damage, making early interventions based on pre-symptomatic indicators crucial. Current efforts to identify molecular markers of early disease lack the resolution, convenience and cost efficiency required to prevent irreversible tissue damage. Analyzing frequently self-collected samples, such as dried blood spots (DBS), could enable the earlier detection of diseases, identify disease-predictive markers and facilitate tailored interventions. To test this, we regularly microsampled a mouse model infected with a type 1-diabetes (T1D)-associated virus. This longitudinal DBS sample collection was analyzed for 92 circulating proteins, revealing transient molecular changes in virus-infected animals that would have been missed with less frequent sampling. Machine learning predicted infection status after day 2 post-infection with >90% accuracy, enabling well-timed treatment of virus-infected animals and diabetes prevention. Our study demonstrates the utility of frequent blood microsampling to monitor disease during the pre-symptomatic phase, allowing for timely interventions. TeaserFrequent blood microsampling detects early biomarkers, enabling timely intervention in immune-mediated diseases

systems biology↗

bioRxiv2024

A ternary Neurexin-T178-PTPR complex represents a core-module of neuronal synapse organization

The organization of cell-cell contacts is fundamental for multi-cellular life and operation of organs. Synapses, prototypic contact sites for neuronal communication, are key to brain function and work over the last decades identified multiple synaptic cell adhesion molecules (sCAMs) that drive their organization. Whether these sCAMs operate independently or in coordination through yet unknown linker proteins remained elusive. Here, we used a systematic large-scale multi-epitope affinity-purification approach combined with quantitative mass spectrometry and immuno-EM to comprehensively map trans-synaptic protein networks in the mouse brain. We discover a presynaptic core-module assembled from the two major sCAM families, Neurexins1-3 and LAR-type receptor protein tyrosine phosphatases (PTPRD,S,F), and the previously uncharacterized tetraspanin proteins T178A, B. These ternary Neurexin-T178-PTPR complexes form through their trans-membrane domains and assemble during biogenesis in the ER. Loss of T178B results in module dissociation, strong reduction of LAR-PTPRs and re-distribution of synaptic Neurexins. At synapses, the Neurexin-T178-PTPR module recruits stable and extended trans-synaptic protein networks with defined pre- and post-synaptic partners and secreted extracellular linkers. The network architecture robustly interlinks the distinct functional modules/machineries of the presynaptic active zone and establishes tight associations with XKR-type lipid scramblases and postsynaptic GABAergic and glutamatergic neurotransmitter receptors. Our data identify a universal presynaptic core-module for synaptic adhesion and trans-synaptic signaling in the mammalian brain.

neuroscience↗

bioRxiv2023

Expanding the GPCR-RAMP interactome

Receptor activity-modifying proteins (RAMPs) can form complexes with G protein-coupled receptors (GPCRs) and regulate their cellular trafficking and pharmacology. RAMP interactions have been identified for about 50 GPCRs, but only a few GPCR-RAMP complexes have been studied in detail. To elucidate a complete interactome between GPCRs and the three RAMPs, we developed a customized library of 215 Dual Epitope-Tagged (DuET) GPCRs representing all GPCR subfamilies. Using a multiplexed suspension bead array (SBA) assay, we identified 122 GPCRs that showed strong evidence for interaction with at least one RAMP. We screened for native interactions in three cell lines and found 23 GPCRs that formed complexes with RAMPs. Mapping the GPCR-RAMP interactome expands the current system-wide functional characterization of RAMP-interacting GPCRs to inform the design of selective GPCR-targeted therapeutics. One-Sentence SummaryNovel complexes between G protein-coupled receptors and interacting proteins point to a system-wide regulation of GPCR function.

biochemistry↗

bioRxiv2022

Multiplexed selectivity screening of anti-GPCR antibodies

G protein-coupled receptors (GPCRs) control critical cellular signaling pathways. Therapeutic agents, such as antibodies (Abs), are being developed to modulate GPCR signaling pathways. However, validating the selectivity of anti-GPCR Abs is challenging due to sequence similarities of individual receptors within GPCR subfamilies. To address this, we developed a multiplexed immunoassay to test >400 anti-GPCR Abs from the Human Protein Atlas targeting a customized library of 215 expressed and solubilized GPCRs representing all GPCR subfamilies. We found that ~61% of Abs were selective for their intended target, ~11% to bind off-target, and ~28% not to bind any GPCR. Antigens of on-target Abs were, on average, significantly longer, more disordered, and less likely to be buried in the interior of the GPCR protein than the other Abs. These results provide important insights into the immunogenicity of GPCR epitopes and form a basis for the design of therapeutic Abs and the detection of pathological auto-antibodies. TEASERA multiplexed library-to-library selectivity analysis of 400 anti-GPCR antibodies within subfamilies of 200 solubilized receptors.

biochemistry↗

bioRxiv2022

Soluble amyloid-β precursor peptide does not regulate GABAB receptor activity

Amyloid-{beta} precursor protein (APP) regulates neuronal activity through the release of secreted APP (sAPP) acting at cell-surface receptors. APP and sAPP were reported to bind to the extracellular sushi domain 1 (SD1) of GABAB receptors (GBRs). A 17 amino-acid peptide (APP17) derived from APP was sufficient for SD1 binding and shown to mimic the inhibitory effect of sAPP on neurotransmitter release and neuronal activity. The functional effects of APP17 and sAPP were similar to those of the GBR agonist baclofen and blocked by a GBR antagonist. These experiments led to the proposal that sAPP activates GBRs to exert its neuronal effects. However, whether APP17 and sAPP indeed influence classical GBR signaling pathways in heterologous cells was not analyzed. Here, we confirm that APP17 binds to GBRs with nanomolar affinity. However, biochemical and electrophysiological assays indicate that APP17 does not influence GBR activity in heterologous cells. Moreover, we found no evidence for APP17 regulating K+ currents in cultured neurons, neurotransmitter release in brain slices, or neuronal activity in vivo. Our results show that APP17 is not a functional GBR ligand and indicate that sAPP exerts neuronal effects through receptors other than GBRs.

neuroscience↗

bioRxiv2020

Facets of individual-specific health signatures determined from longitudinal plasma proteome profiling

BackgroundPrecision medicine approaches aim to tackle diseases on an individual level through molecular profiling. Despite the growing knowledge about diseases and the reported diversity of molecular phenotypes, the descriptions of human health on an individual level have been far less elaborate. MethodsTo provide insights into the longitudinal protein signatures of well-being, we profiled blood plasma collected over one year from 101 clinically healthy individuals using multiplexed antibody assays. After applying an antibody validation scheme, we utilized > 700 protein profiles for in-depth analyses of the individuals short-term health trajectories. FindingsWe found signatures of circulating proteomes to be highly individual-specific. Considering technical and longitudinal variability, we observed both stable and fluctuating proteins in the circulation, as well as networks of proteins that covaried over time. For each participant, there were unique protein profiles and some of these could be explained by associations to genetic variants. InterpretationThis study demonstrates that there was noticeable diversity among clinically healthy subjects, and facets of individual-specific signatures emerged by monitoring the variability of the circulating proteomes over time. Longitudinal profiling of circulating proteomes has the potential to enable a more personal hence precise assessment of health states, and thereby provide a valuable component of precision medicine approaches. FundingThis work was supported by the Erling Persson Foundation for the KTH Centre for Precision Medicine and the Swedish Heart and Lung Foundation for the SCAPIS project. We also acknowledge the Knut and Alice Wallenberg Foundation for funding the Human Protein Atlas project, Science for Life Laboratory for Plasma Profiling Facility, and the Swedish Research Council (Grant no 2017-00641).

biochemistry↗

bioRxiv2019

Mass Spectrometry-based Plasma Proteomics: Considerations from Sample Collection to Achieving Translatable Data

The proteomic analyses of human blood and blood-derived products (e.g. plasma) offers an attractive avenue to translate research progress from the laboratory into the clinic. However, due to its unique protein composition, performing proteomics assays with plasma is challenging. Plasma proteomics has regained interest due to recent technological advances, but challenges imposed by both complications inherent to studying human biology (e.g. inter-individual variability), analysis of biospecimen (e.g. sample variability), as well as technological limitations remain. As part of the Human Proteome Project (HPP), the Human Plasma Proteome Project (HPPP) brings together key aspects of the plasma proteomics pipeline. Here, we provide considerations and recommendations concerning study design, plasma collection, quality metrics, plasma processing workflows, mass spectrometry (MS) data acquisition, data processing and bioinformatic analysis. With exciting opportunities in studying human health and disease though this plasma proteomics pipeline, a more informed analysis of human plasma will accelerate interest whilst enhancing possibilities for the incorporation of proteomics-scaled assays into clinical practice.\n\n\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=51 SRC=\"FIGDIR/small/716563v2_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (20K):\norg.highwire.dtl.DTLVardef@1faf719org.highwire.dtl.DTLVardef@174c1b1org.highwire.dtl.DTLVardef@5860baorg.highwire.dtl.DTLVardef@366c21_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗