Author/Editor		Vind-Kezunovic, Dina; Hélix-Nielsen, Claus; Wojewodzka, Urszula; Gniadecki, Robert
Title		Line tension at lipid phase boundaries regulates formation of membrane vesicles in living cells
Type		članek
Vol. and No.		Letnik 1778, št. 11
Publication year		2008
Volume		str. 2480-2486
ISSN		0005-2736 - Biochimica et biophysica acta - Biomembranes
Language		eng
Abstract		Ternary lipid compositions in model membranes segregate into large-scale liquid-ordered (L(o)) and liquid-disordered (L(d)) phases. Here, we show mu m-sized lipid domain separation leading to vesicle formation in unperturbed human HaCaT keratinocytes. Budding vesicles in the apical portion of the plasma membrane were predominantly labelled with L(d) markers 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate, 1,1'-dilinoleyl-3.3.3',3'-tetramethylindocarbocyanine perchlorate, 1,1'-didodecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate and weakly stained by L(o) marker fluorescein-labeled cholera toxin B subunit which labels ganglioside GM(1) enriched plasma membrane rafts. Cholesterol depletion with methyl-beta-cyclodextrin enhanced DiI vesiculation, GM(1)/DiI domain separation and was accompanied by a detachment of the subcortical cytoskeleton from the plasma membrane. Based on these observations we describe the energetic requirements for plasma membrane vesiculation. We propose that the decrease in total 'L(o)/L(d)' boundary line tension arising from the coalescence of smaller L(d)-like domains makes it energetically favourable for L(d)-like domains to bend from flat mu m-sized surfaces to cap-like budding vesicles. Thus living cells may utilize membrane line tension energies as a control mechanism of exocytic events.
Keywords		domain formation line tension plasma membrane vesiculation fiziologija človeka biokemija