Biology subjects

Stoeber, M.

Publications and source records attributed to Stoeber, M..

9 recordsLinked to original sources

bioRxiv2026

An engineered nanobody inhibitor for molecular-to-circuit control of opioid receptor function

Opioid receptors (ORs) orchestrate pain relief, reward, and dependence, yet their signaling arises from diverse cell types and subcellular compartments that cannot be selectively interrogated with existing pharmacological or genetic approaches. Single-domain antibodies, or nanobodies (Nbs), can probe receptor states, but their potential as tools for controlling native receptor signaling at the system level has remained unexplored. Here, we engineer a suite of high-affinity intracellular Nbs that bind active ORs through structure-guided evolution and in silico design. Iterative optimization yields Nb64, a potent inhibitor that rapidly suppresses transducer engagement, receptor internalization, and downstream signaling, including endogenous pathways in neuronal cells. Organelle targeting highlights Nb64s capacity to control OR activity with subcellular precision, while bio-reversible cell-penetrating peptide (CPP) conjugation enables non-genetic cytosolic delivery. Cell-type-specific expression of Nb64 in VTA interneurons attenuates fentanyl-evoked dopamine release and behavioral responses in mice, demonstrating targeted control of opioid actions in vivo. Nb64 provides a versatile strategy for dissecting OR biology and establishes a generalizable framework for precision inhibition of native GPCR signaling in vivo.

neuroscience↗

bioRxiv2025

CRISPR screen identifies CNIH1 as a selective driver of GPCR export

G protein-coupled receptors (GPCRs), the largest family of transmembrane proteins, transduce extracellular stimuli into intracellular signaling cascades to orchestrate human physiology. The transport of newly synthesized receptors from the endoplasmic reticulum (ER) to the plasma membrane (PM) determines cellular responsiveness to incoming ligands, yet the molecular machinery governing GPCR export remains incompletely defined. Here, we combine a synchronized cargo-release assay with a genome-wide CRISPR/Cas9 screen to systematically map regulators of GPCR ER-to-PM transport. Focusing on the {delta}-opioid receptor (DOR), a prototypical class A GPCR, we identify CNIH1 as a dedicated export factor. In the absence of CNIH1, DOR is retained intracellularly with immature glycosylation, and drives reduced PM signaling. CNIH1 localizes to both ER exit sites and the Golgi, promoting the anterograde transport of a subset of class A GPCRs. Opioid receptors directly interact with CNIH1 and require its putative COPII-binding site for export. Distinct from other human cornichon homologs, CNIH1 defines a selective GPCR-sorting receptor that couples GPCR biosynthesis to signaling competence.

cell biology↗

bioRxiv2025

Visualizing the Dominant GPCR Coupling of Pathogenic Gαo Mutants in GNAO1-Related Disorders

Heterozygous mutations in the GNAO1 gene, which encodes the Go subunit of heterotrimeric G proteins, cause a spectrum of rare neurodevelopmental disorders ranging from early-onset epileptic encephalopathy to milder dystonia phenotypes. Disease dominance of Go mutants appears to arise from multiple functional disruptions, including impaired guanine nucleotide handling, failure to adopt the active conformation, and neomorphic interactions with Ric8A/B chaperones. In parallel, several Go variants have been independently reported to dominantly engage G protein-coupled receptors (GPCRs) or to sequester G{beta}{gamma}, two mechanistically distinct behaviors. These conclusions were inferred from different indirect biosensor assays, likely contributing to the apparent contradiction in their proposed mechanisms. To overcome this, we developed a split-YFP-based bimolecular fluorescence complementation (BiFC) assay to visualize receptor-Go protein complexes at the plasma membrane. Using this system, we found that severe Go variants (S47G, G203R, R209C, E246K) fail to disengage from activated Gi/o-coupled GPCRs, thereby preventing downstream receptor phosphorylation and endocytosis. By contrast, milder dystonia-linked mutants (C215Y and T241_N242insPQ) showed near-normal receptor internalization and only minor phosphorylation defects. These findings establish dominant GPCR coupling as a molecular hallmark of severe GNAO1-related disorders and point to split-YFP BiFC as a robust platform for probing mutant G protein behavior in genetic disease.

cell biology↗

bioRxiv2024

Probing PAC1 receptor activation across species with an engineered sensor

Class-B1 G protein-coupled receptors (GPCRs) are an important family of clinically relevant drug targets that remain difficult to investigate via high-throughput screening and in animal models. Here, we engineered PAClight1P78A, a novel genetically-encoded sensor based on a class-B1 GPCR (the human PAC1 receptor, hmPAC1R) endowed with high dynamic range ({Delta}F/F0 = 1100%), excellent ligand selectivity and rapid activation kinetics ({tau}ON = 1.15 sec). To showcase the utility of this tool for in vitro applications, we thoroughly characterized and compared its expression, brightness and performance between PAClight1P78A transfected and stably-expressing cells. Demonstrating its use in animal models, we show robust expression and fluorescence responses upon exogenous ligand application ex vivo and in vivo in mice, as well as in living zebrafish larvae. Thus, the new GPCR-based sensor can be used for a wide range of applications across the life sciences empowering both basic research and drug development efforts.

neuroscience↗

bioRxiv2023

Structural Basis of μ-Opioid Receptor-Targeting by a Nanobody Antagonist

The -opioid receptor (OR), a prototypical member of the G protein-coupled receptor (GPCR) family, is the molecular target of opioid analgesics such as morphine and fentanyl. Due to the limitations and severe side effects of currently available opioid drugs, there is considerable interest in developing novel modulators of OR function. Most GPCR ligands today are small molecules, however biologics, including antibodies and nanobodies, are emerging as alternative therapeutics with clear advantages such as affinity and target selectivity. Here, we describe the nanobody NbE, which selectively binds to the OR and acts as an antagonist. We functionally characterize NbE as an extracellular and genetically encoded {micro}OR ligand and uncover the molecular basis for {micro}OR antagonism by solving the cryo-EM structure of the NbE-{micro}OR complex. NbE displays a unique ligand binding mode and achieves {micro}OR selectivity by interactions with the orthosteric pocket and extracellular receptor loops. Based on a {beta}-hairpin loop formed by NbE that deeply inserts into the {micro}OR and centers most binding contacts, we design short peptide analogues that retain {micro}OR antagonism. The work illustrates the potential of nanobodies to uniquely engage with GPCRs and describes novel OR ligands that can serve as a basis for therapeutic developments.

molecular biology↗

bioRxiv2023

Development of a genetically-encoded sensor for probing endogenous nociceptin opioid peptide release

Nociceptin/orphanin-FQ (N/OFQ) is a recently appreciated critical opioid peptide with key regulatory functions in several central behavioral processes including motivation, stress, feeding, and sleep. The functional relevance of N/OFQ action in the mammalian brain remains unclear due to a lack of high-resolution approaches to detect this neuropeptide with appropriate spatial and temporal resolution. Here we develop and characterize NOPLight, a genetically encoded sensor that sensitively reports changes in endogenous N/OFQ release. We characterized the affinity, pharmacological profile, spectral properties, kinetics, ligand selectivity, and potential interaction with intracellular signal transducers of NOPLight in vitro. Its functionality was established in acute brain slices by exogeneous N/OFQ application and chemogenetic induction of endogenous N/OFQ release from PNOC neurons. In vivo studies with fibre photometry enabled direct recording of NOPLight binding to exogenous N/OFQ receptor ligands, as well as detection of endogenous N/OFQ release within the paranigral ventral tegmental area (pnVTA) during natural behaviors and chemogenetic activation of PNOC neurons. In summary, we show here that NOPLight can be used to detect N/OFQ opioid peptide signal dynamics in tissue and freely behaving animals.

neuroscience↗

bioRxiv2022

Subcellular location defines GPCR signal transduction

G protein-coupled receptors in intracellular organelles can be activated in response to membrane permeant ligands, which contributes to the diversity and specificity of agonist action. The opioid receptors (ORs) provide a striking example, where opioid drugs activate ORs in the Golgi apparatus within seconds of drug addition. Till date, our knowledge on the signaling of intracellular GPCRs remains incomplete and it is unknown if the downstream effects triggered by ORs in plasma membrane and Golgi apparatus differ. To address this gap, we first assess the recruitment of signal transducers to ORs in both compartments. We find that Golgi-localized ORs couple to Gi/o probes and are phosphorylated by GPCR kinases (GRK2/3), but unlike plasma membrane receptors, do not recruit {beta}-arrestin or a specific G probe. Subsequent molecular dynamics simulations with OR-transducer complexes in model bilayers mimicking plasma membrane or Golgi composition reveal that the lipid environment promotes location selective coupling. Unbiased global analyses then show that OR activation in the plasma membrane and Golgi apparatus has strikingly different downstream effects on transcription and protein phosphorylation. Taken together, the study delineates OR signal transduction with unprecedented spatial resolution and reveals that the subcellular location defines the signaling effect of opioid drugs.

cell biology↗

bioRxiv2019

Agonist-selective recruitment of engineered protein probes and of GRK2 by opioid receptors in living cells

G protein-coupled receptors (GPCRs) signal through allostery, and it is increasingly clear that chemically distinct agonists can produce different receptor-based effects. It has been proposed that agonists selectively promote receptors to recruit one cellular interacting partner over another, introducing allosteric bias into the signaling system. However, the core underlying hypothesis - that different agonists drive GPCRs to engage different cytoplasmic proteins in living cells - remains untested due to the complexity of downstream readouts through which receptor-proximal interactions are typically inferred. Here we describe a scalable cell-based assay to overcome this challenge, based on the use of engineered GPCR-interacting proteins as orthogonal biosensors that are disconnected from endogenous transduction mechanisms. Focusing on opioid receptors, we directly demonstrate differences between protein probe recruitment produced by chemically distinct opioid ligands in living cells. We then show how the selective recruitment applies to GRK2, a biologically relevant opioid receptor regulator protein, through discrete interactions of GRK2 with receptors or with G protein beta-gamma subunits which are differentially promoted by agonists.

cell biology↗

bioRxiv2018

A genetically encoded biosensor reveals location bias of opioid drug action

Opioid receptors (ORs) precisely modulate behavior when activated by native peptide ligands but distort behaviors to produce pathology when activated by non-peptide drugs. A fundamental question is how drugs differ from peptides in their actions on target neurons. One way that drugs can differ is by imposing selective effects on the conformational equilibrium of individual ORs. We wondered if drugs can also impose selective effects on the location of OR activation in individual OR-expressing neurons. Here we develop a genetically encoded biosensor that directly localizes ligand-induced activation and deactivation of ORs in living cells, and use it to generate the first real-time map of the spatiotemporal organization of - and {delta}-OR activation in neurons. Peptide agonists produce a characteristic activation pattern initiated in the plasma membrane and propagating to endosomes after receptor internalization. Drugs produce a different activation pattern by uniquely driving OR activation in the somatic Golgi apparatus and extending throughout the dendritic arbor in Golgi outposts. These results demonstrate a new approach to probe the cellular basis of neuromodulation and reveal that drugs profoundly distort the spatiotemporal landscape of neuronal OR activation.

neuroscience↗