XXII. BIOCHEMICKÝ ZJAZD - Jesseniova lekárska fakulta

Posters
50.
DEHYDROERGOSTEROL ELUCIDATES STEROL UPTAKE PROCESS IN YEAST
S. CereVISIae
Peter Kohút 1 , Martin Valachovič 1,2 , Lucia Hronská 1 and Ivan Hapala 1
1
Institute of Animal Biochemistry and Genetics, Slovak Academy of Sciences,
Moyzesova 61, 90028 Ivanka pri Dunaji, Slovakia
2
Medical University Vienna, Christian Doppler Laboratory for Infection Biology,
Max F. Perutz Laboratories, Vienna, Austria
Yeast Saccharomyces cerevisiae is a facultative anaerobic organism - it can grow either
in the presence or absence of oxygen. However, during anaerobic growth it is unable to
synthesize unsaturated fatty acids and ergosterol, which have to be supplied externally.
Uptake of external sterol in yeast consists of three steps: 1) passage through the cell
wall, 2) entry into plasma membrane and 3) integration into metabolism, but molecular
mechanisms of these individual steps are largely unknown. Sterol uptake can be efficiently
studied with fluorescent sterol probes. Dehydroergosterol (DHE) is a naturally
fluorescent sterol and structural similarity between DHE and ergosterol – native yeast
sterol – ensures that the data acquired using DHE as a probe in the study of sterol uptake
in yeast reflect metabolic processes taking place under physiological conditions. In our
experiments we used DHE to analyze molecular details of sterol uptake in the yeast S.
cerevisiae, particularly to reveal the role of Aus1p and Pdr11p proteins in this process.
These proteins are members of the ABC transporter family and they were previously
identified in a wide-scale screen as proteins involved in sterol uptake in S. cerevisiae. We
used mutants in Aus1p and Pdr11p putative sterol transporters to separate the first two
steps in sterol uptake process. Fluorescent properties of DHE enabled us to distinguish
between membrane-incorporated and cell wall-associated sterol. Our results indicate
that Aus1p and Pdr11p are required for entry of sterols into the plasma membrane and
not for internalization of sterols as suggested in some studies.
This work was supported by grants APVT-51-029504 and VVCE-0064-07
170 XXII. Biochemistry Congress, Martin