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

摘要: Sphingolipid microdomains are thought to result from the organization of plasma membrane sphingolipids and cholesterol into a liquid ordered phase, wherein glycosylphosphatidylinositol (GPI)-anchored proteins enriched. These domains, resistant extraction by cold Triton X-100, can be isolated as buoyant complexes (detergent-resistant membranes) in isopycnic density gradients. Here effects methyl-beta-cyclodextrin (MBCD), specific cholesterol-binding agent that neither binds nor inserts membrane, were investigated on sphingolipid lymphocytes. MBCD released substantial quantities GPI-anchored Thy-1 glycosphingolipid GM1, also other surface including CD45, intracellular Lck Fyn kinases. From endothelial cells, CD59, CD44, but only negligible amount caveolin. Most MBCD-released CD59 not sedimentable thus differed membrane-active agents such saponin streptolysin O, or X-100. Unlike part molecules was gradients co-isolated with GM1. Finally, treatment X-100-isolated detergent-resistant membranes extracted most without affecting properties We suggest (1) preferentially extracts outside, rather than within (2) this partly solubilizes transmembrane glycerophospholipid-rich releases both vesicular non-vesicular form.