Biology subjects

Siepe, D. H.

Publications and source records attributed to Siepe, D. H..

3 recordsLinked to original sources

bioRxiv2022

Receptor Elimination by E3 Ubiquitin Ligase Recruitment (REULR): A Targeted Protein Degradation Toolbox

In recent years, targeted protein degradation (TPD) of plasma membrane proteins by hijacking the ubiquitin proteasome system (UPS) or the lysosomal pathway have emerged as novel therapeutic avenues in drug development to address and inhibit canonically difficult targets. While TPD strategies have been successful to target cell surface receptors, these approaches are limited by the availability of suitable binders to generate heterobifunctional molecules. Here, we present the development of a nanobody (VHH) based degradation toolbox termed REULR (Receptor Elimination by E3 Ubiquitin Ligase Recruitment). We generated human and mouse cross-reactive nanobodies against 5 transmembrane PA-TM-RING type E3 Ubiquitin Ligases (RNF218, RNF130, RNF167, RNF43, ZNRF3) covering a broad range and selectivity of tissue expression with which we characterized expression in human and mouse cell lines and immune cells (PBMCs). We demonstrate that heterobifunctional REULR molecules can enforce transmembrane E3 ligase interaction with a variety of disease relevant target receptors (EGFR, EPOR, PD-1) by induced proximity resulting in effective membrane clearance of the target receptor at varying levels. In addition, we designed E3 Ligase self-degrading molecules, fratricide REULRs (RNF128, RNF130, RENF167, RNF43, ZNRF3), that allow downregulation of one or several E3 Ligases from the cell surface and consequently modulate receptor signaling strength. REULR molecules represent a VHH-based, modular and versatile "mix and match" targeting strategy for facile modulation of cell surface proteins by induced proximity to transmembrane PA-TM-RING E3 ligases.

bioengineering↗

bioRxiv2022

Identification of orphan ligand-receptor relationships using a cell-based CRISPRa enrichment screening platform.

Secreted proteins, which include cytokines, hormones and growth factors, are extracellular ligands that control key signaling pathways mediating cell-cell communication within and between tissues and organs. Many drugs target secreted ligands and their cell-surface receptors. Still, there are hundreds of secreted human proteins that either have no identified receptors ("orphans") and are likely to act through cell surface receptors that have not yet been characterized. Discovery of secreted ligand-receptor interactions by high-throughput screening has been problematic, because the most commonly used high-throughput methods for protein-protein interaction (PPI) screening do not work well for extracellular interactions. Cell-based screening is a promising technology for definition of new ligand-receptor interactions, because multimerized ligands can enrich for cells expressing low affinity cell-surface receptors, and such methods do not require purification of receptor extracellular domains. Here, we present a proteo-genomic cell-based CRISPR activation (CRISPRa) enrichment screening platform employing customized pooled cell surface receptor sgRNA libraries in combination with a magnetic bead selection-based enrichment workflow for rapid, parallel ligand-receptor deorphanization. We curated 80 potentially high value orphan secreted proteins and ultimately screened 20 secreted ligands against two cell sgRNA libraries with targeted expression of all single-pass (TM1) or multi-pass (TM2+) receptors by CRISPRa. We identified previously unknown interactions in 12 of these screens, and validated several of them using surface plasmon resonance and/or cell binding. The newly deorphanized ligands include three receptor tyrosine phosphatase (RPTP) ligands and a chemokine like protein that binds to killer cell inhibitory receptors (KIRs). These new interactions provide a resource for future investigations of interactions between the human secreted and membrane proteomes.

cell biology↗

bioRxiv2021

Membrane phosphoinositides stabilize GPCR-arrestin complexes and offer temporal control of complex assembly and dynamics

Binding of arrestin to phosphorylated G protein-coupled receptors (GPCRs) is crucial for modulating signaling. Once internalized some GPCRs may complex with arrestin, while others interact transiently; this difference affects receptor signaling and recycling. Cell-based and in vitro biophysical assays reveal the role of membrane phosphoinositides (PIPs) in arrestin recruitment and GPCR-arrestin complex dynamics. We find that GPCRs broadly stratify into two groups, one requiring PIP-binding for arrestin recruitment and one that does not. Plasma membrane PIPs potentiate an active conformation of arrestin and stabilize GPCR-arrestin complexes by promoting a receptor core-engaged state of the complex. As allosteric modulators of GPCR-arrestin complex dynamics, membrane PIPs allow for additional conformational diversity beyond that imposed by GPCR phosphorylation alone. The dependance on membrane PIPs provides a mechanism for arrestin release from transiently associated GPCRs, allowing their rapid recycling, while explaining how stably associated GPCRs are able to engage G proteins at endosomes.

biochemistry↗