Movie 1

Actin filaments form a scaffold around secretory granules after fusion with the apical plasma membrane in mouse salivary acinar cells in vivo. Related to Figures 1A-D and S1C.
Intravital confocal imaging of actin filament assembly during isoproterenol-stimulated secretory granule exocytosis in submandibular salivary gland acinar cells in an mTomato x Lifeact-GFP mouse. A close-up view of a single exocytosis event is shown with granule membrane marked by mTomato (red) and actin filaments labeled by Lifeact-GFP (green). Time zero is set to one frame first appearance of Lifeact-GFP signal on the secretory granule. Contrast and brightness was adjusted in each channel for optimal visualization of the granule at early stage post-fusion. Time-lapse image frames were acquired at 944 ms intervals and playback was set to 7.5 frames per sec (approximately 7.8 x real time). Time is displayed in seconds. Scale bar = 3 μm.