Disruption of lipid rafts causes apoptotic cell death in HaCaT keratinocytes.
Lipid rafts are cholesterol-enriched microdomains in plasma membranes. The functional activity of many membrane proteins, including death and growth factor receptors, depends on their insertion in lipid rafts. We have previously demonstrated the presence of lipid rafts in keratinocytes and shown that lipid rafts are involved in the control of keratinocyte proliferation and metabolic activity. In this work, we investigated the effect of lipid-raft disruption on HaCaT keratinocyte survival. Lipid rafts could be disrupted or rearranged with cholesterol-targeting detergents: methyl-beta-cyclodextrin and filipin III. Moreover, cholesterol oxidation by a specific oxidase or blocking of cholesterol synthesis by mevastatin had a similar effect on lipid rafts. All cholesterol-modifying substances caused cell death in a concentration-dependent manner. More detailed studies on the effects of cyclodextrin revealed apoptotic cell death at concentrations >or=0.5% (w/v). The molecular mechanism of apoptosis precipitated by raft disruption remains unknown but does not seem to be dependent of either membrane permeabilization or cell-cycle arrest imposed by cholesterol-modifying compounds.
Bang
Bo
B
Department of Dermatology, Bispebjerg Hospital, University of Copenhagen, Copenhagen, Denmark. bb22@bbh.hosp.dk
Gniadecki
Robert
R
Gajkowska
Barbara
B
D017209:Apoptosis; D002453:Cell Cycle; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D049109:Cell Proliferation; D002784:Cholesterol / Q000737:chemistry / Q000378:metabolism; D002789:Cholesterol Oxidase / Q000378:metabolism; D003902:Detergents / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D005372:Filipin / Q000737:chemistry; D006801:Humans; D020287:In Situ Nick-End Labeling; D015603:Keratinocytes / Q000166:cytology*; D008055:Lipids / Q000737:chemistry*; D008148:Lovastatin / Q000031:analogs & derivatives* / Q000737:chemistry; D021962:Membrane Microdomains / Q000737:chemistry*; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D013997:Time Factors; D047392:beta-Cyclodextrins / Q000737:chemistry
D003902:Detergents; D008055:Lipids; D047392:beta-Cyclodextrins; C108732:methyl-beta-cyclodextrin; C012258:mevastatin; D005372:Filipin; D002784:Cholesterol; D008148:Lovastatin; D002789:Cholesterol Oxidase