Canadian researchers, working in partnership with Brazilian colleagues, have developed 13 bioluminescence sensors for use in testing the effectiveness of new medical drugs in the laboratory.
The study, published in the journalScience Signaling, paves the way for new drugs to be tested and characterized. The biosensors are based on the action of G protein-coupled receptors (GPCRs), which are membrane-bound proteins involved in communication between cells.
The researchers did not choose to study GPCRs by chance. Between one-third and half of all drugs currently on the market are estimated to target these receptors.
"These proteins are targets of drugs used to treat a wide array of disorders and diseases, including allergy, pain, hypertension and diabetes, among others. The new biosensors are expected to be relevant to the discovery and development of new drugs for the treatment of even more diseases," said Claudio Miguel da Costa-Neto, a professor in the Biochemistry and Immunology Department of the University of São Paulo's Ribeirão Preto Medical School (FMRP-USP) in Brazil and one of the authors of the article.
Costa-Neto explained that until a few years ago, the in vitro tests used in new drug development -- performed before clinical trials in animal models and humans -- showed only whether the compound activated or blocked a given cellular response.
"To risk an analogy, until a few years ago these tests were performed as if there were a lamp that could be switched on or off," he said. "We've recently found it possible to analyze the different pathways that can be activated by a receptor and to what extent a given signaling pathway is activated. So it's no longer just a matter of an on or off switch. It's as if we had a room with several LED lights or a dimmer, and could say how many pathways were activated, which ones, and above all how the pathways were activated or blocked. Our biosensors, and others that are being developed by other groups, provide a more complete answer, a signaling profile, as it were."
The study describes how the researchers developed, validated and used a suite of bioluminescence resonance energy transfer (BRET) -- based biosensors to measure the different intracellular signaling pathways and detect the action of pharmaceuticals in cultured cells. The signaling cascades resulting from interactions between GPCRs and their ligands (including hormones and neurotransmitters) control a wide array of processes in cells, making them key targets for new drug discovery.
The international team of researchers used genetic engineering and molecular biology techniques to add fluorescent and luminescent enzymes (such as luciferase, the light-producing substance found in glow-worms) to the GPCR ligands.
"When one of these receptors is activated by a drug and the protein inside the cell interacts with the receptor, light emitted by luciferase is transferred to the fluorescent protein and activates it. In this manner, we can accurately measure different levels of a drug's action," Costa-Neto...