INTERACTION OF A NOVEL FLUORESCENT ANALOG OF INTERFERON-GAMMA WITH TRANSFORMED-CELLS

A fluorescent analog of human recombinant interferon-gamma (IFN-gamma) was prepared for the first time. The recovered pyrene-labeled IFN-gam ma (py-IFN-gamma), with an estimated seven pyrene molecules per IFN-ga mma, retained over half of its original biological activity. Binding o f py-IFN-gamma to human amnion WISH cells showed appreciable enhanceme nt in fluorescence polarization from 0.055 to 0.215 and in fluorescenc e lifetime from 56 to 80 ns. The ratio of the vibronic peaks did not c hange, indicating that the pyrene molecules remained in water environm ent even after binding. Py-IFN-gamma provides a novel tool for unravel ing the mechanism of the initial interaction between this antiprolifer ative lymphokine and its target, cancer cell membrane receptors. Its f luorescence could provide the means to follow receptor recycling when it occurs.