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Effects of cholesterol depletion by cyclodextrin on the sphingolipid microdomains of the plasma membrane

Published in Biochemical Journal. 1998, vol. 335, no. Pt 2, p. 433-440
Abstract Sphingolipid microdomains are thought to result from the organization of plasma membrane sphingolipids and cholesterol into a liquid ordered phase, wherein the glycosylphosphatidylinositol (GPI)-anchored proteins are enriched. These domains, resistant to extraction by cold Triton X-100, can be isolated as buoyant membrane complexes (detergent-resistant membranes) in isopycnic density gradients. Here the effects of methyl-beta-cyclodextrin (MBCD), a specific cholesterol-binding agent that neither binds nor inserts into the plasma membrane, were investigated on the sphingolipid microdomains of lymphocytes. MBCD released substantial quantities of GPI-anchored Thy-1 and glycosphingolipid GM1, and also other surface proteins including CD45, and intracellular Lck and Fyn kinases. From endothelial cells, MBCD released GPI-anchored CD59, and CD44, but only a negligible amount of caveolin. Most MBCD-released Thy-1 and CD59 were not sedimentable and thus differed from Thy-1 released by membrane-active cholesterol-binding agents such as saponin and streptolysin O, or Triton X-100. Unlike that released by Triton X-100, only part of the Thy-1 molecules released by MBCD was buoyant in density gradients and co-isolated with GM1. Finally, treatment of Triton X-100-isolated detergent-resistant membranes with MBCD extracted most of the cholesterol without affecting the buoyant properties of Thy-1 or GM1. We suggest that (1) MBCD preferentially extracts cholesterol from outside, rather than within the sphingolipid microdomains and (2) this partly solubilizes GPI-anchored and transmembrane proteins from the glycerophospholipid-rich membrane and releases sphingolipid microdomains in both vesicular and non-vesicular form.
Keywords AnimalsAntigens, CD44/metabolismAntigens, CD45/metabolismAntigens, CD59/metabolismAntigens, Thy-1/metabolismCaveolin 1CaveolinsCell Membrane/chemistry/drug effects/ metabolismCholesterol/ metabolismCyclodextrins/metabolism/ pharmacologyDetergents/pharmacologyEndothelium, Vascular/cytology/drug effectsG(M1) Ganglioside/metabolismGlycosylphosphatidylinositols/metabolismHumansLymphocytes/chemistry/drug effects/metabolismMembrane Proteins/chemistry/drug effects/metabolismMiceProtein-Tyrosine Kinases/drug effects/metabolismSphingolipids/chemistry/ metabolismbeta-Cyclodextrins
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PMID: 9761744
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