The plant P₄-ATPase ALA2 is involved in flipping of phosphatidylserine analogues

Rosa Laura López-Marqués^{1, Lisbeth Rosager Poulsen1}, Katharina Meffert², Thomas Pomorski², Michael Gjedde Palmgren¹

¹Centre for Membrane Pumps in Cells and Disease - PUMPKIN, Danish National Research Foundation, Department of Plant Biology and Biotechnology, University of Copenhagen, DK-1871 Frederiksberg C, Denmark

²Humboldt-University Berlin, Faculty of Mathematics and Natural Science I, Institute of Biology, 10115 Berlin, Germany

In the model plant Arabidopsis thaliana 12 P₄-ATPases are present, named ALA1 to 12 (for Aminophospholipid ATPase). So far, two isoforms have been characterized (ALA1 and ALA3) and shown to be involved in translocation of phospholipid analogues (1, 2). At least ALA3, located to the Golgi, has been shown to be important for membrane trafficking within the secretory pathway (1). Recently we have identified five Cdc50p homologues in Arabidopsis [ALA Interacting Subunit (ALIS) 1 to 5] (1), and demonstrated that these ß-subunits are essential for the functioning of ALA3. We are currently working on a third Arabidopsis P₄-ATPase isoform, ALA2. We have shown that this isoform is involved in specific translocation of phosphatidylserine analogues. Furthermore, we have found evidence that the substrate specificity is independent of the ß-subunit interacting with this P₄-ATPase. ALA2 in combination with ALIS genes complement both the cold and the metal sensitive phenotype caused by lack of DRS2 in yeast. Tissue specific expression patterns of ALA2 and ALIS genes indicate that different ALIS isoforms may interact with ALA2 in diverse parts of the plant. At present we are studying the subcellular localization of ALA2 in planta in order to understand better its possible physiological function.

1 Poulsen, L.R; López-Marqués, R.L et al. (2008) The Arabidopsis P₄-ATPase ALA3 localizes to the Golgi and requires a ß-subunit to function in lipid translocation and secretory vesicle formation. The Plant Cell, vol. 20, 658-676.

2 Gomès, E. et al. (2000) Chilling tolerance in Arabidopsis involves ALA1, a member of a new family of putative aminophospholipid translocases. The Plant Cell, vol. 12, 2441-2453.