ASSEMBLY OF ACTIN FILAMENTS INDUCED BY SEQUESTRATION OF MEMBRANE CHOLESTEROL IN TRANSFORMED CELLS
T.N. Efremova, V.I. Chubinskij-Nadezhdin,1 S.Y. Khaitlina, E.A. Morachevskaya
Institute of Cytology of the RAS, St.Petersburg;
1 e-mail: vchubinskiy@gmail.com
Cholesterol is one of the major lipid components of plasma membrane and it plays an important role in various signaling processes in mammalian cells. Our study focused on the
role of membrane cholesterol in organization and dynamics of actin cytoskeleton. Experiments were performed on cultured transformed cells characterized by weakly developed
actin network and reduced stress fibers – human embryonic kidney HEK293 cells, epidermoid larynx carcinoma HEp-2 cells and mouse fibroblasts 3T3-SV40. Using F-actin labeling
with rhodamine-phalloidin, actin cytoskeleton rearrangements were analysed after sequestration of membrane cholesterol by cyclic oligosaccharide methyl-beta-cyclodextrin and polyene
macrolide antibiotic filipin. In cells treated with methyl-beta-cyclodextrin or filipin, similar processes of actin cytoskeleton reorganization involving filament assembly were revealed.
In carcinoma HEp-2 cells and fibroblasts 3T3-SV40, cholesterol-sequestering reagents induced intensive stress fiber formation and enhanced cell spreading which corresponded to
reversion of transformed phenotype. The rearrangements of cytoskeleton are likely initiated by disruption of lipid raft integrity that is critically dependent on the level of the membrane
cholesterol.
Key words: plasma membrane, actin cytoskeleton, cholesterol, lipid microdomains, human leukaemia, methyl-beta-cyclodextrin, filipin
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