Biology subjects

Ravn-Boess, N.

Publications and source records attributed to Ravn-Boess, N..

6 recordsLinked to original sources

bioRxiv2025

A developmentally regulated long-range enhancer-promoter contact mediates human neural development

SOX2 is a core pluripotency factor in human embryonic stem cells (hESCs), but upon differentiation to the three germ layers, its expression is preserved selectively in neuroectoderm. The mechanisms regulating SOX2 transcription in distinct developmental stages remain incompletely understood. Here, we demonstrate that a distant enhancer 550 kb from the human SOX2 locus is selectively activated in neural stem cells (NSCs) and establishes long-range contact with the SOX2 gene. CRISPR-Cas9 excision of the enhancer has no effect in hESCs but reduces SOX2 transcription in NSCs and impairs neuroectodermal differentiation and forebrain specification in teratomas and cerebral organoids. CRISPR excision of a CTCF recognition motif adjacent to the enhancer does not affect enhancer activation in neuroectoderm but reduces chromatin looping and SOX2 transcription to partially reproduce phenotypes seen with enhancer deletion. Our findings indicate that the development of the human nervous system depends on a developmentally regulated long-range contact between a distant enhancer and the SOX2 locus.

developmental biology↗

bioRxiv2025

Engineering Antibody-Drug Conjugates targeting an Adhesion GPCR, CD97

Adhesion G protein-coupled receptors (aGPCRs) are key cell-adhesion molecules involved in many cellular functions and contribute to human diseases, including cancer. aGPCRs are characterized by large extracellular regions that could serve as readily accessible antigens. However, the potential of aGPCRs as targets for biologic therapeutics has not been extensively explored. CD97, also known as ADGRE5, is an aGPCR that is upregulated in various cancer types, including acute myeloid leukemia (AML) and glioblastoma (GBM), and their respective cancer stem cells. Here, we developed antibody-drug conjugates (ADCs) targeting CD97 and assessed their efficacy against AML and GBM cells. We generated a panel of synthetic human antibodies targeting distinct epitopes of CD97, from which we identified an antibody that was efficiently internalized. This antibody binds to all isoforms of human CD97 but not to its close homolog, EMR2. Structure determination by single-particle cryo-electron microscopy revealed that this antibody targets the CD97 GPCR autoproteolysis-inducing (GAIN) domain, whose presence is conserved in aGPCRs, through an unconventional binding mode where it extensively utilizes the light chain framework for antigen recognition. Screening of conjugation methods and payloads resulted in a stable ADC that effectively killed AML and GBM cell lines, as well as patient-derived GBM stem cells, with minimal cytotoxicity against peripheral blood mononuclear cells from healthy donors. Our study demonstrates the therapeutic potential of targeting CD97, as well as the aGPCR GAIN domain in general, and broadens our mechanistic understanding of antibody-antigen interactions.

biochemistry↗

bioRxiv2023

The expression profile and tumorigenic mechanisms of CD97 (ADGRE5) in glioblastoma render it a targetable vulnerability

Glioblastoma (GBM) is the most common and aggressive primary brain malignancy. Adhesion G protein-coupled receptors (aGPCRs) have attracted interest for their functional role in gliomagenesis and their potential as treatment targets. To identify therapeutically targetable opportunities among aGPCR family members in unbiased fashion, we analyzed expression levels of all aGPCRs in GBM and non-neoplastic brain tissue. Using bulk and single cell transcriptomic and proteomic data, we show that CD97 (ADGRE5), an aGPCR previously implicated in GBM pathogenesis, is the most promising aGPCR target in GBM, by virtue of its abundance in all GBM tumors and its de novo expression profile in GBM compared to normal brain tissue and neural progenitors. CD97 knockdown or knockout significantly reduces the tumor initiation capacity of patient-derived GBM cultures (PDGC) in vitro and in vivo. Transcriptomic and metabolomic data from PDGCs suggest that CD97 promotes glycolytic metabolism. The oncogenic and metabolic effects of CD97 are mediated by the MAPK pathway. Activation of MAPK signaling depends on phosphorylation of the cytosolic C-terminus of CD97 and recruitment of {beta}-arrestin. Using single-cell RNA-sequencing and biochemical assays, we demonstrate that THY1/CD90 is the most likely CD97 ligand in GBM. Lastly, we show that targeting of PDGCs with an anti-CD97 antibody-drug conjugate in vitro selectively kills tumor cells but not human astrocytes or neural stem cells. Our studies identify CD97 as an important regulator of tumor metabolism in GBM, elucidate mechanisms of receptor activation and signaling, and provide strong scientific rationale for developing biologics to target it for therapeutic purposes.

cancer biology↗

bioRxiv2023

Modulation of GPR133 (ADGRD1) Signaling by its Intracellular Interaction Partner Extended Synaptotagmin 1 (ESYT1)

GPR133 (ADGRD1) is an adhesion G protein-coupled receptor that signals through Gs and is required for growth of glioblastoma (GBM), an aggressive brain malignancy. The regulation of GPR133 signaling is incompletely understood. Here, we use proximity biotinylation proteomics to identify ESYT1, a Ca2+-dependent mediator of endoplasmic reticulum-plasma membrane bridge formation, as an intracellular interactor of GPR133. ESYT1 knockdown or knockout increases GPR133 signaling, while its overexpression has the opposite effect, without altering GPR133 levels in the plasma membrane. The GPR133-ESYT1 interaction requires the Ca2+-sensing C2C domain of ESYT1. Thapsigargin-mediated increases in cytosolic Ca2+ relieve signaling-suppressive effects of ESYT1 by promoting ESYT1-GPR133 dissociation. ESYT1 knockdown or knockout in GBM impairs tumor growth in vitro, suggesting functions of ESYT1 beyond the interaction with GPR133. Our findings suggest a novel mechanism for modulation of GPR133 signaling by increased cytosolic Ca2+, which reduces the signaling-suppressive interaction between GPR133 and ESYT1 to raise cAMP levels.

cell biology↗

bioRxiv2022

PTK7 is a positive allosteric modulator of GPR133 (ADGRD1) signaling in GBM

GPR133 (ADGRD1), an adhesion G protein-coupled receptor, supports growth of glioblastoma, a brain malignancy. We demonstrated that GPR133 is intramolecularly cleaved, and that dissociation of its N-terminal and C-terminal fragments (NTF and CTF) at the plasma membrane correlates with increased receptor signaling. However, how the extracellular interactome of GPR133 in glioblastoma modulates signaling remains unknown. Here, we use affinity purification and mass spectrometry to identify extracellular binding partners of GPR133 in patient-derived glioblastoma cells. We show that the transmembrane protein PTK7 binds the GPR133 NTF and its expression in trans increases GPR133 signaling. This effect requires the intramolecular cleavage of GPR133 and PTK7s anchoring in the plasma membrane. The GPR133-PTK7 interaction facilitates orthosteric activation of GPR133 by soluble peptide mimicking the endogenous tethered Stachel agonist, suggesting PTK7 binding allosterically enhances accessibility of GPR133s orthosteric Stachel binding pocket. GPR133 and PTK7 are expressed in adjacent cells in glioblastoma, where their knockdown phenocopies each other. We propose that this novel ligand-receptor interaction is relevant to the pathogenesis of glioblastoma, as well as physiological processes in several tissues.

cell biology↗

bioRxiv2020

Dissociation of the intramolecularly cleaved N- and C-terminal fragments of the adhesion G protein-coupled receptor GPR133 (ADGRD1) increases canonical signaling

GPR133 (ADGRD1), an adhesion G protein-coupled receptor (GPCR), is necessary for growth of glioblastoma (GBM), a brain malignancy. The extracellular N-terminus of GPR133 is thought to be autoproteolytically cleaved into an N-terminal and a C-terminal fragment (NTF and CTF). Nevertheless, the role of this cleavage in receptor activation remains unclear. Here, we show that the wild-type (WT) receptor is cleaved after protein synthesis and generates significantly more canonical signaling than an uncleavable point mutant (H543R) in patient-derived GBM cultures and HEK293T cells. However, the resulting NTF and CTF remain non-covalently bound until the receptor is trafficked to the plasma membrane, where we find NTF-CTF dissociation. Using a fusion of the hPAR1 receptor N-terminus and the CTF of GPR133, we demonstrate that thrombin-induced cleavage and shedding of the hPAR1 NTF increases receptor signaling. This study supports a model where dissociation of the NTF at the plasma membrane promotes GPR133 activation. Highlights- GPR133 is intramolecularly cleaved in patient-derived GBM cultures - Cleaved GPR133 signals at higher efficacy than the uncleavable GPR133 H543R mutant - The N- and C-terminal fragments (NTF and CTF) of GPR133 dissociate at the plasma membrane - Acute thrombin-induced cleavage of the human PAR1 NTF from the GPR133 CTF increases signaling eTOC BlurbFrenster et al. demonstrate intramolecular cleavage of the adhesion GPCR GPR133 in glioblastoma and HEK293T cells. The resulting N- and C-terminal fragments dissociate at the plasma membrane to increase canonical signaling. The findings suggest dissociation of GPR133s N-terminus at the plasma membrane represents a major mechanism of receptor activation.

cell biology↗