Non-olfactory G-protein-coupled receptors (GPCRs) regulate vital physiological functions and are targets for ∼34% of US Food and Drug Administration (FDA)-approved drugs. While small-molecule-activate Show more
Non-olfactory G-protein-coupled receptors (GPCRs) regulate vital physiological functions and are targets for ∼34% of US Food and Drug Administration (FDA)-approved drugs. While small-molecule-activated GPCRs are well studied, there is growing interest in peptide GPCRs, particularly the melanocortin-4 receptor (MC4R), a key regulator of energy balance and appetite. Activation of MC4R by β-melanocyte-stimulating hormone (β-MSH) reduces food intake, and pathway dysfunction leads to obesity. However, current methods to study GPCR-peptide interactions are resource intensive and low throughput. To address this, we developed a high-throughput cell surface peptide display platform with a β-arrestin-based MC4R reporter to screen over 2,000 β-MSH point mutants. This approach identified peptide variants that significantly impact MC4R activation, including a novel D5H mutant with enhanced receptor activation. Our results demonstrate a scalable method to directly link GPCR activation to peptide variants, offering insights for therapeutic peptide design. Show less
Antibody-drug conjugates (ADCs) selectively deliver chemotherapeutic agents to target cells and are important cancer therapeutics. However, the mechanisms by which ADCs are internalized and activated Show more
Antibody-drug conjugates (ADCs) selectively deliver chemotherapeutic agents to target cells and are important cancer therapeutics. However, the mechanisms by which ADCs are internalized and activated remain unclear. Using CRISPR-Cas9 screens, we uncover many known and novel endolysosomal regulators as modulators of ADC toxicity. We identify and characterize C18ORF8/RMC1 as a regulator of ADC toxicity through its role in endosomal maturation. Through comparative analysis of screens with ADCs bearing different linkers, we show that a subset of late endolysosomal regulators selectively influence toxicity of noncleavable linker ADCs. Surprisingly, we find cleavable valine-citrulline linkers can be processed rapidly after internalization without lysosomal delivery. Lastly, we show that sialic acid depletion enhances ADC lysosomal delivery and killing in diverse cancer cell types, including with FDA (US Food and Drug Administration)-approved trastuzumab emtansine (T-DM1) in Her2-positive breast cancer cells. Together, these results reveal new regulators of endolysosomal trafficking, provide important insights for ADC design and identify candidate combination therapy targets. Show less