Tracking of secretory vesicles of PC12 cells by total internal reflection fluorescence microscopy

Total internal reflection fluorescence microscopy is used to detect cellular events near the plasma membrane. Behaviours of secretory vesicles near the cell surface of living PC 12 cells, a neuroendocrine cell line, are studied. The secretory vesicles are labelled by over-expression of enhanced green fluorescent protein-tagged Rab3A, one of the small G proteins involved in the fusion of secretory vesicles to plasma membrane in PC12 cells. Images acquired by a fast cooled charge-coupled device camera using conventional fluorescence microscopy and total internal reflection fluorescence microscopy are compared and analysed. Within the small evanescent range (< 200 nm), the movements of the secretory vesicles of PC12 cells before and after stimulation by high K⁺ are examined. The movements of one vesicle relative to another already docked on the membrane are detected. Total internal reflection fluorescence microscopy provides a novel optical method to trace and analyse the exocytotic events and vesicle specifically near a cell membrane without interference of signals from other parts of the cell.