Roles of cholesterol in vesicle fusion and motion.
Although it is well established that exocytosis of neurotransmitters and hormones is highly regulated by numerous secretory proteins, such as SNARE proteins, there is an increasing appreciation of the importance of the chemophysical properties and organization of membrane lipids to various aspects of the exocytotic program. Based on amperometric recordings by carbon fiber microelectrodes, we show that deprivation of membrane cholesterol by methyl-beta-cyclodextrin not only inhibited the extent of membrane depolarization-induced exocytosis, it also adversely affected the kinetics and quantal size of vesicle fusion in neuroendocrine PC12 cells. In addition, total internal fluorescence microscopy studies revealed that cholesterol depletion impaired vesicle docking and trafficking, which are believed to correlate with the dynamics of exocytosis. Furthermore, we found that free cholesterol is able to directly trigger vesicle fusion, albeit with less potency and slower kinetics as compared to membrane depolarization stimulation. These results underscore the versatile roles of cholesterol in facilitating exocytosis.
Zhang
Jing
J
Division of Bioengineering, Nanyang Technological University, Singapore.
Xue
Renhao
R
Ong
Wei-Yi
WY
Chen
Peng
P
D000818:Animals; D000963:Antimetabolites / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology*; D002784:Cholesterol / Q000378:metabolism*; D022162:Cytoplasmic Vesicles / Q000187:drug effects / Q000502:physiology*; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008839:Microelectrodes; D008856:Microscopy, Fluorescence; D009038:Motion; D016716:PC12 Cells; D011188:Potassium / Q000378:metabolism; D051381:Rats; D014741:Video Recording; D047392:beta-Cyclodextrins / Q000494:pharmacology
D000963:Antimetabolites; D047392:beta-Cyclodextrins; C108732:methyl-beta-cyclodextrin; D002784:Cholesterol; D011188:Potassium