Endogenous Membrane Receptor Labeling by Reactive Cytokines and Growth Factors to Chase Their Dynamics in Live Cells

Summary Cytokine and growth factor receptors localized on cell membranes play key roles in many biological events. Because the dynamic behaviors of receptors are deeply involved in cytokine- and growth-factor-dependent signaling pathways, reliable techniques for real-time imaging of receptors in live cells are strongly desired. Here, we describe a method of covalently labeling and imaging membrane receptors in live cells by using chemically reactive cytokines and growth factors coupled with 4-dimethylaminopyridine (DMAP), an organocatalyst that facilitates acyl transfer. Construction of the DMAP cytokines and growth factors relies on non-covalent coordination chemistry between an oligo-histidine tag and dimeric Ni(II)-nitrilotriacetate in an in situ manner. This supramolecular approach is relatively simple and flexible and can be applied to labeling not only transiently but also endogenously expressed receptors. Moreover, given the benefit of this traceless labeling of the receptors, our technique allows real-time imaging of the ligand-induced dynamics of endogenously expressed receptors in live cells.