Targeting transforming growth factor-β (TGF-β) receptors is a promising pharmacological approach to normalize aberrant signaling in genetic and non-genetic TGF-β associated diseases including fibrosis, cancer, cardiovascular and musculoskeletal disorders. To identify novel TGF-β receptor kinase inhibitors, methods like in vitro kinase assays, western blot or transcriptional reporter assays are often used for screening purposes. While these methods may have certain advantages, the lack of integration of key features such as receptor specificity, high-throughput capability, and cellular context resemblance remains a major disadvantage. This deficiency could ultimately hinder the translation of study outcomes into later (clinical) stages of drug development. In this study, we introduce an adjusted and optimized live cell NanoBRET Target Engagement (TE)-based method to identify TGF-β receptor specific kinase inhibitors. This comprehensive toolkit contains various TGF-β type I and type II receptors, with corresponding nanoBRET tracers, and disease-related cell lines, including novel non-commercially available materials. The nanoBRET capacity and kinase inhibitory window can be significantly enhanced for functional measurements when stable expression cell lines and substantially low tracer concentrations are used. In addition, this system can be tailored to study TGF-β associated genetic disorders and possibly be used to screen for disease-specific therapeutics. Therefore, the use of this optimized, live cell, antibody-independent nanoBRET Target Engagement assay is highly encouraged for future high-throughput compound screens targeting TGF-β/BMP receptors.

The Hippo pathway plays an important role in organ size control and tissue homeostasis. Dysregulation is involved in many pathologies, including cancer, which has attracted interest in targeting the Hippo pathway. Since the upstream components are bona fide tumor suppressors, it is feasible to target oncogenic downstream targets such as TAZ, a key downstream effector in the Hippo pathway. Its activity is regulated by phosphorylation on multiple sites, with Ser89 playing a critical role in regulation of TAZ activity. Phosphorylation of TAZ at Ser89 promotes binding to 14–3–3 scaffolding proteins, preventing nuclear translocation and abolishing target gene transcription. Here we describe the development of a cell-based assay suitable for high-throughput screening, based on a split NanoLuc luciferase, for monitoring interactions between 14 3–3 and TAZ in living cells. We have validated the assay by screening of a kinase-biased library. The assay can be quickly adapted for higher throughput and thus offers a valuable tool to study new signal inputs involved in regulation of TAZ activity as well as for identification of molecules that modulate the Hippo pathway.

The use of organoid models in biomedical research has grown substantially since their inception. As they gain popularity among scientists seeking more complex and biologically relevant systems, there is a direct need to expand and clarify potential uses of such systems in diverse experimental contexts. Herein we outline a high-content screening (HCS) platform that allows researchers to screen drugs or other compounds against three-dimensional (3D) cell culture systems in a multi-well format (384-well). Furthermore, we compare the quality of robotic liquid handling with manual pipetting and characterize and contrast the phenotypic effects detected by confocal imaging and biochemical assays in response to drug treatment. We show that robotic liquid handling is more consistent and amendable to high throughput experimental designs when compared to manual pipetting due to improved precision and automated randomization capabilities. We also show that image-based techniques are more sensitive to detecting phenotypic changes within organoid cultures than traditional biochemical assays that evaluate cell viability, supporting their integration into organoid screening workflows. Finally, we highlight the enhanced capabilities of confocal imaging in this organoid screening platform as they relate to discerning organoid drug responses in single-well co-cultures of organoids derived from primary human biopsies and patient-derived xenograft (PDX) models. Altogether, this platform enables automated, imaging-based HCS of 3D cellular models in a non-destructive manner, opening the path to complementary analysis through integrated downstream methods.

The importance of a drug's kinetic profile and interplay of structure-kinetic activity with PK/PD has long been appreciated in drug discovery. However, technical challenges have often limited detailed kinetic characterization of compounds to the latter stages of projects. This review highlights the advances that have been made in recent years in techniques, instrumentation, and data analysis to increase the throughput of detailed kinetic and mechanistic characterization, enabling its application earlier in the drug discovery process.

Methylation of proteins and nucleic acids plays a fundamental role in epigenetic regulation, and discovery of methyltransferase (MT) inhibitors is an area of intense activity. Because of the diversity of MTs and their products, assay methods that detect S-adenosylhomocysteine (SAH) – the invariant product of S-adenosylmethionine (SAM)-dependent methylation reactions - offer some advantages over methods that detect specific methylation events. However, direct, homogenous detection of SAH requires a reagent capable of discriminating between SAH and SAM, which differ by a single methyl group. Moreover, MTs are slow enzymes and many have submicromolar affinities for SAM; these properties translate to a need for detection of SAH at low nanomolar concentrations in the presence of excess SAM. To meet these needs, we leveraged the exquisite molecular recognition properties of a naturally occurring SAH-sensing RNA aptamer, or riboswitch. By splitting the riboswitch into two fragments, such that SAH binding induces assembly of a trimeric complex, we engineered sensors that transduce binding of SAH into positive fluorescence polarization (FP) and time resolved Förster resonance energy transfer (TR-FRET) signals. The split riboswitch configuration, called the AptaFluor™ SAH Methyltransferase Assay, allows robust detection of SAH (Z’ > 0.7) at concentrations below 10 nM, with overnight signal stability in the presence of typical MT assay components. The AptaFluor assay tolerates diverse MT substrates, including histones, nucleosomes, DNA and RNA, and we demonstrated its utility as a robust, enzymatic assay method for several methyltransferases with SAM Km values < 1 µM. The assay was validated for HTS by performing a pilot screen of 1,280 compounds against the SARS-CoV-2 RNA capping enzyme, nsp14. By enabling direct, homogenous detection of SAH at low nanomolar concentrations, the AptaFluor assay provides a universal platform for screening and profiling MTs at physiologically relevant SAM concentrations.