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Eukaryotic Cell, February 2008, p. 401-414, Vol. 7, No. 2
1535-9778/08/$08.00+0 doi:10.1128/EC.00386-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

,
Gabriel Alfaro,2,
Baby-Periyanayaki Muthusamy,3
Zachary Klaassen,2
Todd R. Graham,3
Hongyuan Yang,1 and
Christopher T. Beh2*
Department of Biochemistry, National University of Singapore, Republic of Singapore,1 Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada,2 Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee3
Received 19 October 2007/ Accepted 14 December 2007
The pandemic of lipid-related disease necessitates a determination of how cholesterol and other lipids are transported and stored within cells. The first step in this determination is the identification of the genes involved in these transport and storage processes. Using genome-wide screens, we identified 56 yeast (Saccharomyces cerevisiae) genes involved in sterol-lipid biosynthesis, intracellular trafficking, and/or neutral-lipid storage. Direct biochemical and cytological examination of mutant cells revealed an unanticipated link between secretory protein glycosylation and triacylglycerol (TAG)/steryl ester (SE) synthesis for the storage of lipids. Together with the analysis of other deletion mutants, these results suggested at least two distinct events for the biogenesis of lipid storage particles: a step affecting neutral-lipid synthesis, generating the lipid core of storage particles, and another step for particle assembly. In addition to the lipid storage mutants, we identified mutations that affect the localization of unesterified sterols, which are normally concentrated in the plasma membrane. These findings implicated phospholipase C and the protein phosphatase Ptc1p in the regulation of sterol distribution within cells. This study identified novel sterol-related genes that define several distinct processes maintaining sterol homeostasis.
Published ahead of print on 21 December 2007.
W.F. and G.A. contributed equally to this work.
Present address: School of Biomolecular Sciences and Biotechnology, University of New South Wales, Sydney, Australia.
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