Integrated cell-based platform to study EGFR activation and transactivation.

The epidermal growth factor receptor (EGFR) pathway is one of the most deregulated molecular pathways in human epithelial cancers. Many approved drugs were optimized to directly target EGFR but yielded only modest clinical improvement in cancer patients due to low efficacy and drug resistance. Transactivation of EGFR by other cell surface receptors such as G-protein-coupled receptors (GPCRs) was proposed to explain this lack of efficacy.

G-protein-coupled receptor-mediated MAPK and PI3-kinase signaling is maintained in Chinese hamster ovary cells after γ-irradiation.

To expedite G-protein-coupled receptor (GPCR) drug screening studies, cell lines amenable to transfection (e.g. CHO cells) have been widely used as cellular models.

An emerging role for kinase screening in GPCR drug discovery.

GPCRs are a large class of cell-surface receptors that are involved in a diverse array of biological processes, including many that are critical to diseases. As a result, GPCRs are a major focus for drug discovery research, and have been highly amenable to therapeutic intervention. However, the successes to date may represent the 'low-hanging fruit' (ie, outcomes that have been easiest to achieve).

Aequorin functional assay for characterization of G-protein-coupled receptors: implementation with cryopreserved transiently transfected cells.

Assay technologies that measure intracellular Ca(2+) release are among the predominant methods for evaluation of GPCR function. These measurements have historically been performed using cell-permeable fluorescent dyes, although the use of the recombinant photoprotein aequorin (AEQ) as a Ca(2+) sensor has gained popularity with recent advances in instrumentation. The requirement of the AEQ system for cells expressing both the photoprotein and the GPCR target of interest has necessitated the labor-intensive development of cell lines stably expressing both proteins.

Functional characterization of human receptors for short chain fatty acids and their role in polymorphonuclear cell activation.

Short chain fatty acids (SCFAs), including acetate, propionate, and butyrate, are produced at high concentration by bacteria in the gut and subsequently released in the bloodstream. Basal acetate concentrations in the blood (about 100 microm) can further increase to millimolar concentrations following alcohol intake. It was known previously that SCFAs can activate leukocytes, particularly neutrophils.

Aequorin-based functional assays for G-protein-coupled receptors, ion channels, and tyrosine kinase receptors.

Aequorin is a photoprotein originating from jellyfish, whose luminescent activity is dependent on the concentration of calcium ions. Due to the high sensitivity and low background linked to luminescent assays, as well as to its absence of toxicity and its large linear dynamic range, aequorin has been used as an intracellular calcium indicator since its discovery in the early 1960s. The first applications of aequorin involved its microinjection in cells.

Two subtypes of ecdysis-triggering hormone receptor in Drosophila melanogaster.

Insect ecdysis is a hormonally programmed physiological sequence that enables insects to escape their old cuticle at the end of each developmental stage. The immediate events leading to ecdysis, which are initiated upon release of ecdysis-triggering hormones (ETH) into the bloodstream, include respiratory inflation and sequential stereotypic behaviors that facilitate shedding of the cuticle. Here we report that the Drosophila gene CG5911 encodes two functionally distinct subtypes of G protein-coupled receptors through alternative splicing (CG5911a and CG5911b) that respond preferentially to ecdysis-triggering hormones of flies and moths.

Recombinant aequorin as a reporter for receptor-mediated changes of intracellular Ca2+ -levels in Drosophila S2 cells.

The bioluminescent Ca(2+)-sensitive reporter protein, aequorin, was employed to develop an insect cell-based functional assay system for monitoring receptor-mediated changes of intracellular Ca(2)(+)-concentrations. Drosophila Schneider 2 (S2) cells were genetically engineered to stably express both apoaequorin and the insect tachykinin-related peptide receptor, STKR. Lom-TK III, an STKR agonist, was shown to elicit concentration-dependent bioluminescent responses in these S2-STKR-Aeq cells.

Identification of natural ligands for the orphan G protein-coupled receptors GPR7 and GPR8.

GPR7 and GPR8 are two structurally related orphan G protein-coupled receptors, presenting high similarities with opioid and somatostatin receptors. Two peptides, L8 and L8C, derived from a larger precursor, were recently described as natural ligands for GPR8 (Mori, M., Shimomura, Y.

Adaptation of aequorin functional assay to high throughput screening.

AequoScreen, a cellular aequorin-based functional assay, has been optimized for luminescent high-throughput screening (HTS) of G protein-coupled receptor (GPCRs). AequoScreen is a homogeneous assay in which the cells are loaded with the apoaequorin cofactor coelenterazine, diluted in assay buffer, and injected into plates containing the samples to be tested. A flash of light is emitted following the calcium increase resulting from the activation of the GPCR by the sample.