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Reference: Kohut P, et al. (2011) The role of ABC proteins Aus1p and Pdr11p in the uptake of external sterols in yeast: Dehydroergosterol fluorescence study. Biochem Biophys Res Commun 404(1):233-8

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Abstract


Uptake of external sterols in the yeast Saccharomyces cerevisiae is a multistep process limited to anaerobiosis or heme deficiency. It includes crossing the cell wall, insertion of sterol molecules into plasma membrane and their internalization and integration into intracellular membranes. We applied the fluorescent ergosterol analogue dehydroergosterol (DHE) to monitor the initial steps of sterol uptake by three independent approaches: fluorescence spectroscopy, fluorescence microscopy and sterol quantification by HPLC. Using specific fluorescence characteristics of DHE we showed that the entry of sterol molecules into plasma membrane is not spontaneous but requires assistance of two ABC pumps - Aus1p or Pdr11p. DHE taken up by uptake-competent hem1DeltaAUS1PDR11 cells could be directly visualized by UV-sensitive wide field fluorescence microscopy. HPLC analysis of sterols revealed significant amounts of exogenous ergosterol and DHE (but not cholesterol) associated with uptake-deficient hem1Deltaaus1Deltapdr11Delta cells. Fluorescent sterol associated with these cells did not show the characteristic emission spectrum of membrane-integrated DHE. The amount of cell-associated DHE was significantly reduced after enzymatic removal of the cell wall. Our results demonstrate that the yeast cell wall is actively involved in binding and uptake of ergosterol-like sterols.CI - Copyright (c) 2010. Published by Elsevier Inc.

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Journal Article
Authors
Kohut P, Wustner D, Hronska L, Kuchler K, Hapala I, Valachovic M
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