Retention of prominin in microvilli reveals distinct cholesterol-based lipid micro-domains in the apical plasma membrane

Membrane cholesterol-sphingolipid 'rafts', which are characterized by their insolubility in the non-ionic detergent Triton X-100 in the cold, have bee n implicated in the sorting of certain membrane proteins, such as placental alkaline phosphatase (PLAP), to the apical plasma membrane domain of epith elial cells. Here we show that prominin, an apically sorted pentaspan membr ane protein, becomes associated in the trans-Golgi network with a lipid raf t that is soluble in Triton X-100 but insoluble in another non-ionic deterg ent, Lubrol WX. At the cell surface, prominin remains insoluble in Lubrol W X and is selectively associated with microvilli, being largely segregated f rom the membrane subdomains containing FLAP. Cholesterol depletion results in the loss of prominin's microvillus-specific localization but does not le ad to its complete intermixing with FLAP. We propose the coexistence within a membrane domain, such as the apical plasma membrane, of different choles terol-based lipid rafts, which underlie the generation and maintenance of m embrane subdomains.