Apoptosis is an important and necessary cell death program which promotes homeostasis and organismal survival. When dysregulated, however, it can lead to a myriad of pathologies from neurodegenerative diseases to cancer. Apoptosis is therefore the subject of intense study aimed at dissecting its pathways and molecular mechanisms. Although many assay methods exist for confirming whether an apoptotic response has occurred in vitro, most methods are destructive and involve laborious operator effort or specialized instrumentation. Here we describe a real-time, no-wash, microplate method which utilizes recombinant annexin V fusion proteins containing evolved binary subunits of NanoBiT™ luciferase. The fusion proteins, a time-released enzymatic substrate, a necrosis detection dye and exogenous calcium ions are delivered via an optimized and physiologically inert reagent directly to cells in culture at the time of treatment or dosing. Luminescent signals proportional to phosphatidylserine (PS) exposure and fluorescent signals generated as a result of loss of membrane integrity are then collected using a standard multimode plate reader at scheduled intervals over the exposure. The resulting luminescent and fluorescent data are then used to define the kinetics and magnitude of an apoptotic response. This study details our efforts to develop, characterize, and demonstrate the features of the assay by providing relevant examples from diverse cell models for programmed cell death.

ATP depletion and ADP formation are generic detection methods used for the identification of kinase and other ATP-utilizing enzyme inhibitors in high-throughput screening campaigns. However, the most widely used nucleotide detection approaches require high ATP consumption rates or involve the use of coupling enzymes, which can complicate the selection of lead compounds. As an alternative, we have developed the Transcreener (BellBrook Labs, Madison, WI) platform, which relies on the direct immunodetection of nucleotides. Here we describe the development of antibodies with >100-fold selectivity for ADP versus ATP, which enable robust detection of initial velocity rates (Z' > 0.7 at 10% substrate consumption) at ATP concentrations ranging from 0.1 microM to 1,000 microM in a competitive fluorescence polarization (FP) immunoassay. Competitive binding experiments indicate similar affinities for other nucleotide diphosphates, including 2' -deoxy ADP, GDP, and UDP. The antibody-tracer complex and the red-shifted, ratiometric FP signal are stable for at least 24 h at room temperature, providing suitable conditions for high-throughput screening. A method for calculating a kinase ATP Km with this FP immunoassay is also presented. The Transcreener ADP assay provides a simple, generic assay platform for inhibitor screening and selectivity profiling that can be used for any ADP-generating enzyme.

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High-content tumor cell migration assays in 3-dimensional (3D) extracellular matrix are a powerful tool for modeling and understanding the biology of this critical step in the process of metastasis. Currently available methods offer very limited throughput and are not amenable to studies of comparative pharmacology or small-scale screening. The authors present an automated approach to high-content tumor cell migration assays. A standard screening-sized plate with an array of microchannels was designed and constructed from common thermoplastics. After filling the channels with 3D matrix, cells were placed at one end of the channel, and migration into the channel was monitored via an imaging system. All liquid-handling steps were performed by standard liquid-handling robotics. Tumor cell migration in the channel was truly 3D and correlated with metastatic potential. The information-rich data from these assays were used to rank the potency of compounds inhibiting migration through 3D collagen as well as to gain additional insights into the compounds' activities related to cell health. This approach is compatible with a variety of multiparametric, morphological, and/or kinetic readouts.

Here we demonstrate the concept of kinase profiling using a panel of four kinases and 10 kinase inhibitors. We used the Kinase-Glo Plus Luminescent Kinase Assay and the Deerac Fluidics Equator HTS noncontact liquid-handling system to design and perform an ultrahigh-throughput profiling screen. We present IC50 values for each test compound and show how such profiling can streamline the initial drug discovery process.