Dynamic imaging of single secretory granule in cultured PC12 cells

Fluorescent labeling and dynamic imaging of secretory vesicles are new powerful means to study the mechanisms of protein and membrane trafficking. The large dense-core granules in PC12 cells were labeled by transfecting EGFP-hpNPY chimera and imaged with epi-fluorescence and evanescent field (EF) fluorescence simultaneously. Under epi-fluorescence illumination, the cells exhibited nearly uniform fluorescence, however, EF-fluorescence excitation revealed distinct fluorescent spots corresponding to GFP-labeled granules. The trafficking, docking and fusing with plasma membrane of individual granule in cultured PC12 cells were observed directly by EF fluorescence imaging.