Docking and fusion of insulin secretory granules in SUR1 knock out mouse beta-cells observed by total internal reflection fluorescence microscopy

To explore how the sulfonylurea receptor (SUR1) is involved in docking and fusion of insulin granules, dynamic motion of single insulin secretory granules near the plasma membrane was examined in SUR1 knock-out (Sur1KO) beta-cells by total internal reflection fluorescence microscopy. Sur1KO beta-cells exhibited a marked reduction in the number of fusion events from previously docked granules. However, the number of docked granules declined during stimulation as a consequence of the release of docked granules into the cytoplasm vs. fusion with the plasma membrane. Thus, the impaired docking and fusion results in decreased insulin exocytosis from Sur1KO beta-cells.