Dynasore inhibits rapid endocytosis in bovine chromaffin cells

Tsai CC, Lin CL, Wang TL, Chou AC, Chou MY, Lee CH, PengIW, Liao JH, Chen YT, Pan CY.Dynasore inhibits rapid endocytosisin bovine chromaffin cells.Am J Physiol Cell Physiol297: C397–C406,2009. First published June 10, 2009; doi:10.1152/ajpcell.00562.2008.—Vesicle recycling is vital for maintaining membrane homeostasis andneurotransmitter release. Multiple pathways for retrieving vesicles fusedto the plasma membrane have been reported in neuroendocrine cells.Dynasore, a dynamin GTPase inhibitor, has been shown to specifi-cally inhibit endocytosis and vesicle recycling in nerve terminals. Tocharacterize its effects in modulating vesicle recycling and repetitiveexocytosis, changes in the whole cell membrane capacitance of bovinechromaffin cells were recorded in the perforated-patch configuration.Constitutive endocytosis was blocked by dynasore treatment, asshown by an increase in membrane capacitance. The membranecapacitance was increased during strong depolarizations and declinedwithin 30 s to a value lower than the prestimulus level. The amplitude,but not the time constant, of the rapid exponential decay was signif-icantly decreased by dynasore treatment. Although the maximal in-crease in capacitance induced by stimulation was significantly in-creased by dynasore treatment, the intercepts attime 0of the curvefitted to the decay phase were all110% of the membrane capaci-tance before stimulation, regardless of the dynasore concentrationused. Membrane depolarization caused clathrin aggregation and F-actin continuity disruption at the cell boundary, whereas dynasoretreatment induced clathrin aggregation without affecting F-actin con-tinuity. The number of invagination pits on the surface of the plasmamembrane determined using atomic force microscopy was increasedand the pore was wider in dynasore-treated cells. Our data indicatethat dynamin-mediated endocytosis is the main pathway responsiblefor rapid compensatory endocytosis.