A versatile platform for activity determination of cytokines and growth factors based on the human TSLP (thymic stromal lymphopoietin) receptor

Cytokines and growth factors are signaling proteins involved in communication processes between cells. They are involved in the control of numerous essential physiological processes such as cell proliferation, gene transcription and differentiation; therefore being in the focus of basic and applied research. Many of them are also of relevance for human diseases. When observed as potential targets for pharmacological intervention and objects of structure/function studies, it is important to measure their biological activities, optionally along with potential inhibitors, in a convenient and rational manner. Such tests are frequently laborious to set up and their establishment is complicated by the necessity to employ problematic cell types and sophisticated assays. Here we present a robust and modular activity assay system which can be adapted to virtually all ligands that signal through dimerization of membrane receptors from different families. The technique rests on fusing ligandbinding domains of specific receptors to the transmembrane and intracellular components of the thymic stromal lymphopoietin (TSLP) receptor which translates signals into readily quantifiable luciferase expression in reporter cells. We show that the activation of various hematopoietic cytokine receptors, of receptor tyrosine kinases as well as of receptors bearing serine/threonine kinase domains by their respective ligands was faithfully reflected both upon transient and stable introduction of hybrid receptor and reporter gene constructs into the murine pro B cell line Ba/F3. Moreover, we demonstrate the suitability of this platform for the functional characterization of cytokine/growth factor receptor inhibitors.