Author/Editor		Rituper, Boštjan; Chowdhury Haque, Helena; Jorgačevski, Jernej; Coorssen, Jens R.; Kreft, Marko; Zorec, Robert
Title		Cholesterol-mediated membrane surface area dynamics in neuroendocrine cells
Type		članek
Vol. and No.		Letnik 1831, št. 7
Publication year		2013
Volume		str. 1228-1238
ISSN		1388-1981 - BBA - Molecular and Cell Biology of Lipids
Language		eng
Abstract		How cholesterol, a key membrane constituent, affects membrane surface area dynamics in secretory cells is unclear. Using methyl--cyclodextrin (MCD) to deplete cholesterol, we imaged melanotrophs from male Wistar rats in real-time and monitored membrane capacitance (Cm), fluctuations of which reflect exo- and endocytosis. Treatment with MCD reduced cellular cholesterol and caused a dose-dependent attenuation of the Ca2+-evoked increase in Cm (IC50 = 5.3 mM) vs. untreated cells. Cytosol dialysis of MCD enhanced the attenuation of Cm increase (IC50 = 3.3 mM), suggesting cholesterol depletion at intracellular membrane sites was involved in attenuating exocytosis. Acute extracellular application of MCD resulted in an immediate Cm decline, which correlated well with the cellular surface area decrease, indicating the involvement of cholesterol in the regulation of membrane surface area dynamics. This decline in Cm was three-fold slower than MCD-mediated fluorescent cholesterol decay, implying that the exocytosis is the likely physiological means for plasma membrane cholesterol replenishment. MCD had no effect on the specific Cm and the blockade of endocytosis by Dyngo 4a, confirmed by inhibition of dextran uptake, also had no effect on the time-course of MCD-induced Cm decline. Thus acute exposure to MCD evokes a Cm decline linked to the removal of membrane cholesterol, which cannot be compensated for by exocytosis. We propose that the primary contribution of cholesterol to surface area dynamics is via its role in regulated exocytosis.
Keywords		exocytosis endocytosis cholesterol eksocitoza endocitoza holesterol