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Viewing report
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Sterol acetylation and export from yeast and
mammalian cells. Edition No. 1
VDM Publishing House, July 2009, Pages: 108
Sterol homeostasis in eukaryotic cells relies on the
reciprocal interconversion of free sterols and steryl
esters. Excess free sterols are esterified to steryl
esters, the storage form of sterols, by
acyltransferases. Upon cellular demand, steryl esters
are hydrolyzed to free sterols and fatty acids by
three sterol ester hydrolases. We have identified a
novel sterol modification in yeast, the
sterol acetylation/deacetylation cycle. Sterol
acetylation requires the acetyltransferase, ATF2,
whereas deacetylation requires a membrane-anchored
deacetylase, SAY1. Lack of SAY1 results in the
secretion of acetylated sterols into the culture
medium. Acetylation and export of
the steroid hormone precursor pregnenolone depends on
its acetylation by ATF2, but is independent of
SAY1-mediated deacetylation, indicating that the
substrate specificity of the deacetylase determines
whether acetylated sterols and steroids are secreted
from the cells or whether they are deacetylated and
retained. Human AADAC (aryl acetamide deacetylase)
complements Say1 activity and is thus a functional
homologue of SAY1. These findings indicate that at
least a part of this pathway is evolutionarily
conserved.
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