SENSITIVITY TO LYSIS BY NATURAL KILLERS DEPENDS ON THE INTEGRITY OF LIPID RAFTS IN PLASMA MEMBRANE OF TRANSFORMED CELLS
N. A. Filatova, V. I. Chubinskij-Nadezhdin, V. A. Ivanov, E. A. Morachevskaya 1
Institute of Cytology RAS, St. Petersburg;
1 e-mail: elenmo@mail.cytspb.rssi.ru
The present work focused on the role of cholesterol-rich membrane microdomains (rafts) in cellular mechanisms of innate immunity and anticancer defence. The lytic effect of natural killers
(NK) was examined in dependence on cholesterol content in transformed target cells. In the current study, K562 human erythroleukaemia cells were the targets. K562 cells were treated with
methyl-beta-cyclodextrin (MbCD) to deplete membrane cholesterol that was verified by enzymatic method. With the use of 3H-uridine test, NK (mouse splenocytes) cytotoxity
was estimated under various conditions, specifically, after incubation of K562 cells with MbCD or inactive analog alpha-cyclodextrin. The data obtained show that cholesterol-depleting treatment
(2.5 or 5 mM MbCD) of target cells results in full loss of their sensitivity to NK lysis. The effect is likely to be due to disintegrity of lipid rafts that is critically dependent on the level of membrane
cholesterol. Visualization of cell surface changes by fluorescent labeling of ganglioside GM1 confirmed our conclusions.
Key words: plasma membrane, natural killers, cholesterol, lipid rafts, human leukaemia K562 cells, met-hyl-beta-cyclodextrin, alpha-cyclodextrin
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