Dynasore inhibits rapid endocytosis in bovine chromaffin cells.
Vesicle recycling is vital for maintaining membrane homeostasis and neurotransmitter release. Multiple pathways for retrieving vesicles fused to the plasma membrane have been reported in neuroendocrine cells. Dynasore, a dynamin GTPase inhibitor, has been shown to specifically inhibit endocytosis and vesicle recycling in nerve terminals. To characterize its effects in modulating vesicle recycling and repetitive exocytosis, changes in the whole cell membrane capacitance of bovine chromaffin cells were recorded in the perforated-patch configuration. Constitutive endocytosis was blocked by dynasore treatment, as shown by an increase in membrane capacitance. The membrane capacitance was increased during strong depolarizations and declined within 30 s to a value lower than the prestimulus level. The amplitude, but not the time constant, of the rapid exponential decay was significantly decreased by dynasore treatment. Although the maximal increase in capacitance induced by stimulation was significantly increased by dynasore treatment, the intercepts at time 0 of the curve fitted to the decay phase were all approximately 110% of the membrane capacitance before stimulation, regardless of the dynasore concentration used. Membrane depolarization caused clathrin aggregation and F-actin continuity disruption at the cell boundary, whereas dynasore treatment induced clathrin aggregation without affecting F-actin continuity. The number of invagination pits on the surface of the plasma membrane determined using atomic force microscopy was increased and the pore was wider in dynasore-treated cells. Our data indicate that dynamin-mediated endocytosis is the main pathway responsible for rapid compensatory endocytosis.
Tsai
Chia-Chang
CC
Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan.
Lin
Chih-Lung
CL
Wang
Tzu-Lun
TL
Chou
Ai-Chuan
AC
Chou
Min-Yi
MY
Lee
Chia-Hsueh
CH
Peng
I-Wei
IW
Liao
Jia-Hong
JH
Chen
Yit-Tsong
YT
Pan
Chien-Yuan
CY
D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D019439:Chromaffin Cells / Q000187:drug effects / Q000502:physiology; D002966:Clathrin / Q000378:metabolism; D025802:Electric Capacitance; D004705:Endocytosis / Q000187:drug effects*; D005089:Exocytosis / Q000502:physiology; D005456:Fluorescent Dyes / Q000378:metabolism; D006835:Hydrazones / Q000494:pharmacology*; D018625:Microscopy, Atomic Force; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D011726:Pyridinium Compounds / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D022161:Transport Vesicles / Q000378:metabolism
D015220:Calcium Channels; D002966:Clathrin; C092350:FM 4-64; D005456:Fluorescent Dyes; D006835:Hydrazones; C511794:N'-(3,4-dihydroxybenzylidene)-3-hydroxy-2-naphthahydrazide; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds; D011188:Potassium; D002118:Calcium