Staff Members of the Institute of Biochemistry, TU - Institut für ...

Cell Biology Group
Group leader: Günther Daum
Graduate students: Tibor Czabany, Melanie Connerth, Sona Rajakumari, Karlheinz Grillitsch,
Miroslava Spanova, Susanne Horvath, Martina Gsell, Vid V. Flis
Diploma student: Sabine Zitzenbacher
Technician: Claudia Hrastnik
Visiting scientists: Sabina Tavares, Fluxome Company, Lyngby, Denmark
General description
The existence of functional organelles is the basis for regulated processes within a cell. To
sequester organelles from their environment, membranes are required which not only protect
the interior of the organelles but also govern communication with the rest of the cell.
Therefore, it is very important to understand the biogenesis and maintenance of biological
membranes. To study this question our laboratory makes use of the yeast as a well established
experimental system. Our studies are focused on the synthesis of lipids, their storage and their
assembly into organelle membranes. We make use of the advantages of this experimental
system to combine biochemical, molecular and cell biological methods addressing problems
of lipid metabolism, lipid depot formation and membrane biogenesis.
The majority of yeast lipids are synthesized in the endoplasmic reticulum (ER) with some
significant contributions of mitochondria, the Golgi and the so-called lipid particles. Other
subcellular fractions are devoid of lipid-synthesizing activities. Spatial separation of lipid
biosynthetic steps and lack of lipid synthesis in several cellular membranes necessitate
efficient transfer of lipids from their site of synthesis to their proper destination(s). The
maintenance of organelle lipid profiles requires strict coordination of biosynthetic and
translocation activities.
Specific aspects studied recently in our laboratory are (i) assembly and homeostasis of
phosphatidylethanolamine in yeast organelle membranes with emphasis on peroxisomes and
the plasma membrane, (ii) neutral lipid storage in lipid particles/droplets and mobilization of
these depots with emphasis on the involvement of lipases and hydrolases, and (iii)
characterization of organelle membranes from the industrial yeast Pichia pastoris.
Phosphatidylethanolamine, a key component of yeast organelle membranes
Work from our laboratory and from other groups had shown that phosphatidylethanolamine
(PE), one of the major phospholipids of yeast membranes, is highly important for cellular
function and cell proliferation. PE synthesis in the yeast is accomplished by a network of
reactions including (i) synthesis of phosphatidylserine (PS) in the endoplasmic reticulum,
(ii) decarboxylation of PS by mitochondrial phosphatidylserine decarboxylase 1 (Psd1p) or
(iii) Psd2p in a Golgi/vacuolar compartment, (iv) the CDP-ethanolamine pathway (Kennedy
pathway) in the endoplasmic reticulum, and (v) the lysophospholipid acylation route
catalyzed by Ale1p. To obtain more insight into biosynthesis, assembly and homeostasis of
PE single and multiple mutants bearing defects in the respective pathways can be used.
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