The target molecule, known as IKK (for IKappa kinase), regulates processes that can trigger dramatic changes in cellular physiology. Scientists have linked these changes to many different disorders.
IKK stands at a pivot point in the middle of an important set of linked chain reactions known as the NF-KappaB pathway, which affect the activity levels of various genes. The position of IKK appears to make it the key regulator of the pathway and therefore a key to the behavior of the gene the pathway is attached to.
To use the firefly protein to monitor IKK, lead author Dr Shimon Gross altered cell lines to genetically fuse the luciferase protein to IKB (IKappaB), the protein that comes immediately after IKK in the NF-KappaB pathway. When the pathway is enabled, IKK triggers reactions that lead to the degradation of IKB. In cells with genetically altered IKB, the attached luciferase is broken down too, meaning scientists can detect increased IKK activity via decreased light from the cells.
“Our new system allows researchers to monitor whether drugs for these conditions are hitting this exact molecular target in cell culture and laboratory animals,” said senior investigator Dr David Piwnica-Worms, professor of molecular biology and pharmacology and of radiology.
In their study, Gross and Piwnica-Worms tested the technique in live mice by transplanting genetically altered tumor cells and by using a technique that inserted the fused IKB/luciferase protein into liver cells only. They are currently working to develop a line of mice with the IKB/luciferase fusion built into its genetic code.